WO2015087591A1 - Capacitor and method for charging/discharging same - Google Patents

Capacitor and method for charging/discharging same Download PDF

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Publication number
WO2015087591A1
WO2015087591A1 PCT/JP2014/074075 JP2014074075W WO2015087591A1 WO 2015087591 A1 WO2015087591 A1 WO 2015087591A1 JP 2014074075 W JP2014074075 W JP 2014074075W WO 2015087591 A1 WO2015087591 A1 WO 2015087591A1
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Prior art keywords
electrode
capacitor
upper limit
limit voltage
active material
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PCT/JP2014/074075
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French (fr)
Japanese (ja)
Inventor
光靖 小川
知陽 竹山
奥野　一樹
高橋　賢治
光保 上田
真嶋　正利
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住友電気工業株式会社
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Publication of WO2015087591A1 publication Critical patent/WO2015087591A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/26—Electrodes characterised by their structure, e.g. multi-layered, porosity or surface features
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/04—Hybrid capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/14—Arrangements or processes for adjusting or protecting hybrid or EDL capacitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/66—Current collectors
    • H01G11/70—Current collectors characterised by their structure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/13—Energy storage using capacitors

Definitions

  • the present invention relates to a capacitor charged and discharged at a high charge upper limit voltage and a method for charging and discharging the same.
  • a lithium ion capacitor includes a positive electrode including a porous carbon material such as activated carbon as an electrode active material, a negative electrode including a material that absorbs and releases lithium ions as an electrode active material, and a lithium ion conductive nonaqueous electrolyte.
  • EDLC generally includes a positive electrode including a porous carbon material that adsorbs and desorbs anions as an electrode active material, a negative electrode including a porous carbon material that adsorbs and desorbs cations as an electrode active material, and an anion and a cation.
  • An electrolyte An electrolyte.
  • a positive electrode of a lithium ion capacitor and a positive electrode and a negative electrode of an EDLC generally have an aluminum foil as an electrode current collector and an electrode mixture layer formed on the aluminum foil and containing an electrode active material.
  • the electrode mixture includes a conductive additive and / or a binder in addition to the electrode active material.
  • Patent Document 1 the positive electrode obtained by apply
  • an aluminum foil is used as an electrode current collector of EDLC.
  • Patent Document 3 proposes to use aluminum foam as an EDLC electrode current collector.
  • an alkali metal ion capacitor such as a lithium ion capacitor is charged / discharged in a range where the upper limit voltage of charging is up to about 3.8V, and an EDLC is charged / discharged in a range where the upper limit voltage of charging is up to about 2.5V. .
  • the electrode is significantly deteriorated due to charging / discharging, and the durability (or cycle characteristics) of the capacitor is lowered.
  • An object of the present invention is to provide a capacitor that can stably charge and discharge even when the upper limit voltage of charging and discharging is increased and has excellent durability.
  • One aspect of the present invention is a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, the first electrode, and the second electrode.
  • a capacitor including a separator interposed between electrodes and an electrolyte containing an anion and a cation, The capacitor is an alkali metal ion capacitor or EDLC,
  • the first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
  • the first electrode active material includes at least a material that reversibly supports the anion,
  • the content of the first electrode mixture in the first electrode is 30 to 90% by mass,
  • the density of the first electrode is 0.3 to 1.1 g / cm 3 , Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1
  • the capacitor includes a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, and the first electrode and the second electrode.
  • the first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
  • the first electrode active material includes at least a material that reversibly supports the anion,
  • the content of the first electrode mixture in the first electrode is 30 to 90% by mass,
  • the density of the first electrode is 0.3 to 1.1 g / cm 3 ,
  • Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
  • the in the alkali metal ion capacitor the upper limit voltage V 1 is 3.8V, the upper limit voltage V 2 is 4.2V,
  • the upper limit voltage V 1 is 2.5V, the upper limit voltage V 2 is 2.9V, It said
  • the upper limit voltage of charging / discharging of the capacitor is increased (for example, it is increased to 4.2 V or higher for an alkali metal ion capacitor and 2.9 V or higher for EDLC), charging / discharging is stably performed.
  • the capacitor which can be performed and is excellent in durability can be provided.
  • FIG. 1 is a longitudinal sectional view schematically showing a capacitor according to an embodiment of the present invention. It is a lineblock diagram showing roughly the charge and discharge system concerning one embodiment of the present invention.
  • a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, the first electrode A capacitor interposed between the separator and the second electrode, and an electrolyte containing an anion and a cation,
  • the capacitor is an alkali metal ion capacitor or an electric double layer capacitor
  • the first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material
  • the first electrode active material includes at least a material that reversibly supports the anion,
  • the content of the first electrode mixture in the first electrode is 30 to 90% by mass,
  • the density of the first electrode is 0.3 to 1.1 g / cm 3 , Ratio of capacity C 2 when charging / discharging with upper limit voltage V
  • the electrode density is usually increased (for example, greater than 1.1 g / cm 3 ).
  • the electrode density is usually increased (for example, greater than 1.1 g / cm 3 ).
  • the capacity may not be increased depending on the state of the electrode. Specifically, when the electrode density is larger than 1.1 g / cm 3 , increasing the charge / discharge upper limit voltage decreases the capacity due to charge / discharge (that is, the durability decreases).
  • the electrode mixture can be stably held in the skeleton by using a three-dimensional network electrode current collector.
  • the electrode density by controlling the electrode density to the above specific range, it is possible to suppress deterioration of the electrode due to charge / discharge up to a high upper limit voltage. Specifically, even if charging / discharging is performed up to a high upper limit voltage, dropping and / or peeling of the electrode mixture (particularly, the electrode active material) can be suppressed. Therefore, the capacity
  • the upper limit voltage of charging / discharging is near the upper limit voltage of a general capacitor (specifically, the voltage V 1 ), the decrease in capacity due to charging / discharging is small, so the electrode density is controlled within the above range. There is almost no effect by doing.
  • the upper limit voltage is a high voltage exceeding the voltage V 1 (specifically, the voltage V 2 or more)
  • the durability can be remarkably improved by setting the electrode density within the above range. Therefore, it can be said that the effect of improving the durability due to the electrode density in the above specific range is an effect obtained only when the upper limit voltage of charging / discharging is increased to a high voltage of V 2 or higher.
  • the density of the electrode means the mass (that is, the apparent density) of the electrode per unit apparent volume (1 cm 3 ) of the electrode.
  • the mass of the electrode includes the mass of the current collector, and specifically, is the total mass of the current collector and the electrode mixture.
  • Capacitances C1 and C2 and a later-described capacitance C3 are capacities when charging / discharging at the same current rate, respectively. These capacities are preferably measured under the condition that the current per area of the first electrode facing the second electrode is 0.1 to 10 mA / cm 2 .
  • the first electrode current collector has a hollow skeleton.
  • Such an electrode current collector is lightweight, and the hollow skeleton of the electrode current collector has a tunnel shape or a tube shape, so that the electrolyte can easily flow in the capacitor.
  • the ratio of the capacitance C 3 when the charging and discharging with the upper limit voltage V 3 with respect to the capacitance C 1: C 3 / C 1 is less than 1.7, in the alkali metal ion capacitor, the upper limit voltage V 3 Is 4.5 V, and in the electric double layer capacitor, the upper limit voltage V 3 is preferably 3.2 V.
  • the capacitor having such a feature even when it is charged up to an upper limit voltage equal to or higher than the voltage V 3 , charging and discharging can be performed stably and reversibly, and the durability of the capacitor can be improved.
  • the thickness of the first electrode is preferably 100 to 2000 ⁇ m.
  • the first electrode having such a thickness has a high retention capacity of the electrode active material, which is advantageous in improving durability.
  • the capacitor is an alkali metal ion capacitor
  • the cation includes an alkali metal ion
  • the second electrode active material includes a material that reversibly supports the alkali metal ion.
  • Another embodiment of the present invention is a method for charging and discharging a capacitor,
  • the capacitor includes a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, and the first electrode and the second electrode.
  • the first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
  • the first electrode active material includes at least a material that reversibly supports the anion,
  • the content of the first electrode mixture in the first electrode is 30 to 90% by mass,
  • the density of the first electrode is 0.3 to 1.1 g / cm 3 ,
  • Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
  • the upper limit voltage V 1 is 3.8V
  • the upper limit voltage V 2 is 4.2V
  • the electric double layer capacitor the upper limit voltage V 1 is 2.5V, the upper limit voltage V 2 is
  • a capacitor according to an embodiment of the present invention includes a first electrode, a second electrode having a polarity opposite to that of the first electrode, a separator interposed between the first electrode and the second electrode, and an electrolyte.
  • the first electrode includes a first electrode active material
  • the second electrode includes a second electrode active material.
  • the electrolyte includes anions and cations.
  • the first electrode includes a first electrode current collector having a three-dimensional network shape including aluminum or an aluminum alloy, and a first electrode material filled in the first electrode current collector and including a first electrode active material.
  • An electrode mixture is an electrode current collector having a three-dimensional network shape including aluminum or an aluminum alloy, and a first electrode material filled in the first electrode current collector and including a first electrode active material.
  • the first electrode current collector included in the first electrode includes aluminum or an aluminum alloy.
  • the content of aluminum in the first electrode current collector is, for example, 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more or 98% by mass or more.
  • the content of aluminum in the first electrode current collector is 100% by mass or less, and may be 99.9% by mass or less. These lower limit values and upper limit values can be arbitrarily combined.
  • the content of aluminum in the first electrode current collector may be, for example, 80 to 100% by mass, or 95 to 100% by mass.
  • the first electrode current collector may contain impurities inevitably mixed.
  • Examples of the aluminum alloy contained in the first electrode current collector include aluminum-iron alloy, aluminum-copper alloy, aluminum-manganese alloy, aluminum-silicon alloy, aluminum-magnesium alloy, aluminum-magnesium-silicon alloy, aluminum- Examples include zinc alloys and aluminum-nickel alloys.
  • the first electrode current collector has a three-dimensional network skeleton containing aluminum or an aluminum alloy.
  • a three-dimensional network skeleton is a skeleton or structure having a fiber part (or rod-like part) formed of aluminum or an aluminum alloy, and the fiber parts are three-dimensionally connected to form a network network.
  • the first electrode current collector can include a plurality of fiber portions (or rod-shaped portions), and the plurality of fiber portions are three-dimensionally connected to form a three-dimensional network-like skeleton. Yes.
  • the three-dimensional mesh-shaped first electrode current collector is formed of a resin porous body (resin foam, resin nonwoven fabric, etc.) having continuous voids by, for example, a metal ( Specifically, it can be formed by coating with aluminum and / or an aluminum alloy.
  • the obtained first electrode current collector has a large number of cell-like pores one by one corresponding to the shape of the resin foam, and a continuous void ( That is, it has a communication hole. It is preferable that an opening (or window) is formed between the adjacent cellular holes, and the holes communicate with each other.
  • the porosity of the first electrode current collector is, for example, 30 to 99% by volume, preferably 50 to 98% by volume, more preferably 80 to 98% by volume, or 90 to 98% by volume. It is.
  • the average pore diameter in the three-dimensional network skeleton (average diameter of cell-like pores communicating with each other) is, for example, from 50 to 1000 ⁇ m, preferably from 100 to 900 ⁇ m, from the viewpoint of filling and holding properties of the electrode mixture.
  • the thickness is preferably 350 to 900 ⁇ m.
  • the average pore diameter is preferably smaller than the thickness of the first electrode current collector (or the first electrode).
  • the three-dimensional network skeleton of the first electrode current collector has a cavity inside (that is, is hollow).
  • the cavity in the skeleton is formed by removing the porous resin body.
  • the cavity in the skeleton of the first electrode current collector may have a communication hole shape, and such a skeleton has a tunnel shape or a tube shape.
  • the first electrode current collector having a hollow skeleton is extremely lightweight while having a bulky three-dimensional structure.
  • the average width of the cavity inside the skeleton is, for example, 0.5 to 5 ⁇ m, preferably 1 to 4 ⁇ m or 2 to 3 ⁇ m.
  • the first electrode is formed by filling the first electrode current collector with the first electrode mixture, and then usually drying and compressing (or rolling) the current collector in the thickness direction.
  • the porosity and average pore diameter of the current collector change due to the compression.
  • the ranges of the porosity and average pore diameter of the first electrode current collector are those of the porosity and average pore diameter before filling the first electrode mixture and before rolling.
  • the first electrode current collector has a very high porosity and a large specific surface area. That is, a large amount of active material can be attached to a wide area of the current collector surface including the surface in the gap. In addition, since the contact area between the current collector and the active material can be increased and the porosity can be increased while filling a large amount of the active material in the gap, the active material can be effectively used.
  • the specific surface area of the first electrode collector (BET specific surface area) is, for example, 100 ⁇ 700cm 2 / g, preferably 150 ⁇ 650cm 2 / g, more preferably 200 ⁇ 600cm 2 / g.
  • the binder contained in the electrode mixture is likely to deteriorate.
  • the binder deteriorates during charging and discharging, and the electrode mixture falls off and / or the electrode mixture layer peels off. As a result, a high capacity is secured. become unable.
  • the first electrode current collector by using the first electrode current collector as described above, even if the binder is deteriorated by increasing the upper limit voltage of charge / discharge to, for example, V 2 or more, the first electrode The state in which the first electrode mixture (particularly, the first electrode active material) is held in the skeleton of the current collector can be maintained, and the electrolyte can be held. Therefore, the capacity
  • the first electrode since the three-dimensional network of the first electrode current collector is stretched, the fiber parts of the first electrode current collector are close to each other, and the distance between the fiber part and the electrode active material particles is short. Therefore, the first electrode has high conductivity. Moreover, since a certain amount of porosity can be ensured even after the first electrode mixture is filled in the first electrode, the electrolyte can be sufficiently held in the vicinity of the electrode active material. By using such a first electrode, the output of the capacitor can be easily increased.
  • the thickness of the first electrode is, for example, 100 to 2000 ⁇ m, preferably 150 to 1500 ⁇ m, and more preferably 180 to 1200 ⁇ m. In addition to being easy to obtain a high capacity, when the thickness of the first electrode is within such a range, the holding capacity of the electrode active material is high, which is advantageous for improving the durability.
  • the capacitor examples include those that can use an electrode current collector made of aluminum or an aluminum alloy, for example, alkali metal ion capacitors such as lithium ion capacitors and sodium ion capacitors; EDLCs.
  • alkali metal ion capacitors such as lithium ion capacitors and sodium ion capacitors
  • EDLCs EDLCs
  • the first electrode is a positive electrode
  • the first electrode may be either a positive electrode or a negative electrode, or may be used for both the positive electrode and the negative electrode.
  • the first electrode mixture filled in the first electrode current collector includes a first electrode active material.
  • the first electrode active material includes at least a material that reversibly supports (specifically, adsorbs and desorbs) anions.
  • the first electrode active material can be appropriately selected according to the type of capacitor and the polarity of the first electrode.
  • the first electrode active material includes at least a material that adsorbs and desorbs anions.
  • the first electrode active material may be a material that adsorbs and desorbs anions and cations.
  • the first electrode active material includes a material that adsorbs and desorbs cations. All of these materials are materials that cause a non-Faraday reaction during charging and discharging.
  • the first electrode is preferably a positive electrode.
  • the first electrode active material includes at least a material that adsorbs and desorbs anions
  • examples of such a material include porous carbon materials such as activated carbon, mesoporous carbon, microporous carbon, and carbon nanotube (first porous carbon material).
  • the first porous carbon material may be activated or may not be activated.
  • These 1st porous carbon materials can be used individually by 1 type or in combination of 2 or more types. Of the first porous carbon materials, activated carbon and / or microporous carbon is preferred.
  • the positive electrode active material can further contain other active materials as required in addition to the first porous carbon material.
  • the content of the first porous carbon material in the positive electrode active material is preferably more than 50% by mass, and may be 80% by mass or more or 90% by mass or more. Content of the 1st porous carbon material in a positive electrode active material is 100 mass% or less. In particular, the content of activated carbon and microporous carbon in the positive electrode active material is preferably within such a range. It is also preferable that the positive electrode active material contains only the first porous carbon material (particularly activated carbon and / or microporous carbon).
  • microporous carbon known ones used for capacitors can be used, for example, those obtained by heating metal carbides such as silicon carbide and titanium carbide in an atmosphere containing chlorine gas. Good.
  • the activated carbon known ones used for capacitors can be used.
  • the raw material of activated carbon include wood; coconut shells; pulp waste liquid; coal or coal-based pitch obtained by thermal decomposition thereof; heavy oil or petroleum-based pitch obtained by thermal decomposition thereof; phenol resin and the like.
  • the carbonized material is generally then activated.
  • the activation method include a gas activation method and a chemical activation method.
  • the average particle diameter of the activated carbon (median diameter in the volume-based particle size distribution, the same shall apply hereinafter) is not particularly limited, but is preferably 20 ⁇ m or less.
  • the specific surface area is not particularly limited, but is preferably about 800 to 3000 m 2 / g. When the specific surface area is in such a range, it is advantageous for increasing the capacitance of the capacitor, and the internal resistance can be reduced.
  • the first electrode is filled with the first electrode mixture slurry containing the first electrode active material in the skeleton of the first current collector, and then the dispersion medium contained in the first electrode mixture slurry is removed. Further, it can be obtained by compressing (or rolling) the current collector holding the first electrode active material, if necessary.
  • the dispersion medium for example, water or the like is used in addition to an organic solvent such as N-methyl-2-pyrrolidone (NMP).
  • the first electrode mixture may contain a conductive additive and / or a binder in addition to the first electrode active material. At least part of the conductive additive used for the first electrode is attached to the surface of the first electrode current collector to form a conductive layer, and the first electrode mixture is applied to the first electrode so as to cover the conductive layer. It may be carried on a current collector.
  • Examples of conductive assistants include carbon blacks such as acetylene black and ketjen black; graphite (natural graphite such as flake graphite and earth graphite; artificial graphite and the like); conductive compounds such as ruthenium oxide; carbon fibers and metal fibers, etc. Examples of the conductive fibers can be exemplified.
  • the amount of the conductive assistant is, for example, 1 to 20 parts by mass, preferably 2 to 10 parts by mass with respect to 100 parts by mass of the first electrode active material.
  • the amount of the conductive assistant is in such a range, it is easy to increase the electrode density while ensuring the conductivity of the electrode mixture.
  • the first electrode current collector having a three-dimensional network shape is used, it is easy to ensure high conductivity in the first electrode even if the amount of the conductive auxiliary agent is small.
  • the amount of the conductive assistant is 5 parts by mass or less (for example, 0 to 5 parts by mass) or 3 parts by mass or less (for example, 0.1 to 3 parts by mass) with respect to 100 parts by mass of the first electrode active material. ).
  • the type of the binder is not particularly limited.
  • a fluorine resin such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene
  • a chlorine-containing vinyl resin such as polyvinyl chloride
  • a polyolefin resin such as polyethylene
  • a rubbery heavy material such as styrene butadiene rubber.
  • Polyvinyl pyrrolidone polyvinyl alcohol
  • cellulose derivatives [cellulose ethers such as carboxymethyl cellulose (carboxyalkyl cellulose and the like)] and the like can be used.
  • the amount of the binder is not particularly limited, and can be selected from the range of, for example, about 0.5 to 15 parts by mass, preferably 1 to 12 parts by mass, more preferably 3 to 10 parts per 100 parts by mass of the first electrode active material. A mass part may be sufficient. In the embodiment of the present invention, since the first electrode current collector having a three-dimensional network shape is used, a large amount of the first electrode mixture can be held on the current collector even if the amount of the binder is small.
  • the amount of the binder can be 5 parts by mass or less (for example, 1 to 5 parts by mass) with respect to 100 parts by mass of the first electrode active material, and may be 2 to 4 parts by mass.
  • the density of the first electrode is controlled in the range of 0.3 to 1.1 g / cm 3 .
  • the density of the first electrode is controlled in the range of 0.3 to 1.1 g / cm 3 .
  • the density of the first electrode is 0.3 g / cm 3 or more, preferably 0.4 g / cm 3 or more, more preferably 0.5 g / cm 3 or more.
  • the density of the first electrode is 1.1 g / cm 3 or less, preferably 1 g / cm 3 or less, and more preferably 0.8 g / cm 3 or less. These lower limit values and upper limit values can be arbitrarily combined.
  • the density of the first electrode may be, for example, 0.4 to 1.1 g / cm 3 , 0.5 to 1.1 g / cm 3 , or 0.5 to 1 g / cm 3 .
  • the first electrode current collector as described above is used, and the density of the first electrode is controlled within the above range, thereby stably charging / discharging even if the upper limit voltage of charging / discharging is increased. And a high capacity can be obtained.
  • the ratio of the capacity C 2 when the capacitor is charged / discharged at the upper limit voltage V 2 to the capacity C 1 when the capacitor is charged / discharged at the upper limit voltage V 1 : C 2 / C 1 is 1.3 or more. Yes, preferably 1.4 or more.
  • the upper limit voltage V 1 is 3.8V
  • the upper limit voltage V 2 is 4.2V.
  • the upper limit voltage V 1 is 2.5V
  • the upper limit voltage V 2 is 2.9V.
  • the voltage V 1 is a general (or conventional) upper limit voltage in each capacitor, and the voltage V 2 is 0.4 V higher than the voltage V 1 .
  • the ratio of the capacity C 3 when the capacitor is charged / discharged with the upper limit voltage V 3 with respect to the capacity C 1 : C 3 / C 1 is, for example, 1.6 or more, preferably 1.7 or more, more preferably 1. 75 or more.
  • the upper limit voltage V 3 is 4.5 V for the alkali metal ion capacitor and 3.2 V for EDLC.
  • the voltage V 3 is a voltage higher by 0.7V than the voltage V 1 .
  • the high value of the C 2 / C 1 ratio and / or the C 3 / C 1 ratio indicates that the capacitor is increased by 0.4 V or more or 0.7 V or more higher than the general upper limit voltage. This means that charging and discharging can be performed stably even when charging, and a decrease in capacity due to charging and discharging can be suppressed.
  • the density of the first electrode varies slightly depending on the content of the electrode mixture. Therefore, when the content of the first electrode mixture in the first electrode is 30 to 90% by mass, the density of the first electrode only needs to satisfy the above range.
  • the content of the first electrode mixture in the first electrode is preferably 40 to 85% by mass, more preferably 50 to 83% by mass.
  • the separator included in the capacitor can be appropriately selected according to the type of the capacitor.
  • the separator has ion permeability and is interposed between the first electrode and the second electrode, and physically separates them to prevent a short circuit.
  • the separator has a porous structure and allows ions to pass through by holding an electrolyte in the pores.
  • a material of the separator for example, polyolefin such as polyethylene and polypropylene; polyester such as polyethylene terephthalate; polyamide; polyimide; cellulose; glass fiber and the like can be used.
  • the average pore diameter of the separator is not particularly limited and is, for example, about 0.01 to 5 ⁇ m.
  • the thickness of the separator is not particularly limited, and is about 10 to 100 ⁇ m, for example.
  • the configurations of capacitors other than the first electrode will be described in more detail with respect to each of the alkali metal ion capacitor and the EDLC capacitor.
  • Alkali metal ion capacitor (Alkali metal ion capacitor)
  • the first electrode is a positive electrode and the second electrode is a negative electrode.
  • the negative electrode that is the second electrode includes a second electrode active material (that is, a negative electrode active material).
  • the second electrode can include a second electrode current collector (that is, a negative electrode current collector) that holds the second electrode active material.
  • the negative electrode current collector may be a metal foil, but is preferably a metal porous body from the viewpoint of increasing the capacity of the capacitor.
  • a metal porous body having a three-dimensional network skeleton (particularly, a hollow skeleton) similar to the aluminum porous body as the first electrode current collector is preferable.
  • the porosity, average pore diameter, void width inside the skeleton, specific surface area and the like of the metal porous body can be appropriately selected from the ranges exemplified for the metal porous body of the positive electrode current collector.
  • the material for the negative electrode current collector is preferably copper, copper alloy, nickel, nickel alloy, stainless steel, or the like.
  • the negative electrode current collector can be produced according to the case of the first electrode current collector using these materials instead of aluminum or aluminum alloy when the resin porous body is metal-coated.
  • the negative electrode active material includes a material that reversibly supports (or occludes and releases, or inserts and desorbs) alkali metal ions.
  • materials that cause a Faraday reaction during charge and discharge such as carbon materials that occlude and release (or insert and desorb) alkali metal ions (also referred to as third carbon materials), and alkali metals.
  • Titanium oxide eg, lithium titanium oxide (such as spinel type lithium titanium oxide such as lithium titanate), sodium titanium oxide (such as sodium titanate)]
  • silicon oxide silicon alloy, tin oxide, tin alloy Is mentioned.
  • Examples of the third carbon material include graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), and a carbonaceous material having a graphite type crystal structure.
  • a negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.
  • the negative electrode active material preferably has a theoretical capacity of 300 mAh / g or more.
  • a third carbon material is preferable, and a carbonaceous material having a graphite-type crystal structure (hereinafter also referred to as a fourth carbon material) and / or hard carbon is particularly preferable.
  • the graphite-type crystal structure means a layered crystal structure, and examples thereof include a cubic crystal structure and a rhombohedral crystal structure.
  • the fourth carbon material include natural graphite (eg, scaly graphite), artificial graphite, and graphitized mesocarbon microspheres. These 4th carbon materials can be used individually by 1 type or in combination of 2 or more types.
  • alkali metal ions are inserted between layers of the graphite type crystal structure of the fourth carbon material during charging, and during discharge, the graphite type crystal structure has Alkali metal ions are released from the interlayer.
  • an average interplanar spacing d002 of the (002) plane measured by the X-ray diffraction spectrum of the fourth carbon material is used as an index of the degree of development of the graphite-type crystal structure in the fourth carbon material.
  • the fourth carbon material, the average spacing d 002 is preferably less than 0.337 nm.
  • the lower limit of the average spacing d 002 is not particularly limited, the average spacing d 002, for example, be 0.335 or more.
  • the fourth carbon material having an average interplanar spacing d 002 in such a range alkali metal ions can be more efficiently inserted into the graphite-type crystal structure at the time of charging, and the graphite-type crystal structure at the time of discharging. Alkali metal ions can be released smoothly from
  • Hard carbon unlike graphite having a graphite-type crystal structure in which carbon network surfaces overlap in a layered manner, has a turbostratic structure in which the carbon network surfaces overlap in a three-dimensionally shifted state. Hard carbon does not change from a turbulent structure to a graphite structure even by heat treatment at a high temperature (for example, 3000 ° C.), and the development of graphite crystallites is not observed. Therefore, hard carbon is also referred to as non-graphitizable carbon.
  • the average spacing d 002 of the fourth carbon material is classified into graphite is as small as less than 0.337nm, as described above, large average spacing d 002 of the hard carbon having a turbostratic structure, for example, more than 0.37nm It is.
  • the upper limit of the average spacing d 002 of the hard carbon is not particularly limited, the average spacing d 002, for instance, can be less than or equal to 0.42 nm.
  • Mean spacing d 002 of the hard carbon for example, 0.37 ⁇ 0.42 nm, preferably be a 0.38 ⁇ 0.4 nm.
  • the alkali metal ions When alkali metal ions are supported on the hard carbon, the alkali metal ions are inserted between the layers of the graphite-type crystal structure that is slightly contained in the hard carbon, inside the turbostratic structure (specifically, the graphite-type crystal structure It is considered that the carbon is supported (or occluded) by the hard carbon by entering and / or being adsorbed by the hard carbon.
  • Hard carbon has a turbulent structure, and the ratio of the graphite-type crystal structure in the hard carbon is small. Therefore, most of the alkali metal ions are inserted into portions other than the interlayer of the graphite-type crystal structure (for example, voids formed in the turbulent layer structure) and / or adsorbed to hard carbon, It is thought that it is occluded by hard carbon. Therefore, when using hard carbon (particularly, hard carbon having an average interplanar spacing d 002 in the above range), the volume change during charge / discharge is small, and deterioration is easy to suppress even after repeated charge / discharge. .
  • hard carbon has a lower average specific gravity than graphite having a crystal structure in which the carbon network surface is densely stacked in a layered manner.
  • the average specific gravity of graphite is about 2.1 to 2.25 g / cm 3
  • the average specific gravity of hard carbon is, for example, 1.7 g / cm 3 or less, preferably 1.4 to 1.7 g / cm 3. 3 or 1.5 to 1.7 g / cm 3 .
  • Hard carbon includes, for example, a carbonaceous material obtained by carbonizing a raw material in a solid phase.
  • the raw material that undergoes carbonization in the solid phase is a solid organic substance, and specifically includes sugars, resins (thermosetting resins such as phenol resins; thermoplastic resins such as polyvinylidene chloride) and the like.
  • the saccharide include saccharides having relatively short sugar chains (monosaccharides or oligosaccharides such as sugar), and polysaccharides such as cellulose [eg cellulose or derivatives thereof (cellulose ester, cellulose ether, etc.); wood, Materials containing cellulose, such as fruit shells (coconut shells, etc.)] and the like.
  • Hard carbon is obtained by heating and carbonizing the above raw material in a solid phase. Carbonization can be performed at a temperature of about 500 to 1600 ° C., for example, and heating at a first temperature (for example, a temperature of 500 ° C. or more and less than 800 ° C.) and a second temperature higher than the first temperature (for example, , A temperature of 800 to 1600 ° C.) may be appropriately combined. Glassy carbon is also included in hard carbon. Hard carbon may be used alone or in combination of two or more.
  • the negative electrode active material can include an active material other than hard carbon and the fourth carbon material. From the viewpoint of efficiently occluding and releasing alkali metal ions, the content of hard carbon and / or fourth carbon material in the negative electrode active material is 80% by mass or more (specifically, 80 to 100% by mass). It is preferably 90% by mass or more (specifically, 90 to 100% by mass).
  • the negative electrode active material may be composed of only hard carbon and / or fourth carbon material.
  • the negative electrode is coated or filled with a negative electrode mixture (specifically, a negative electrode mixture slurry) on the negative electrode current collector, dried, and if necessary, the dried product is compressed (or Obtained by rolling).
  • a negative electrode you may use what is obtained by forming the deposit film of a negative electrode active material on the surface of a negative electrode collector by vapor phase methods, such as vapor deposition and sputtering.
  • at least part of the conductive additive used for the negative electrode is attached to the surface of the negative electrode current collector to form a conductive layer, and the negative electrode mixture or The negative electrode active material may be supported on the negative electrode current collector.
  • the negative electrode active material may be pre-doped with alkali metal ions. By pre-doping with alkali metal ions, the negative electrode potential is sufficiently lowered, thereby increasing the voltage of the capacitor, so that the capacity of the alkali metal ion capacitor can be increased.
  • the alkali metal ion is the same as the alkali metal ion contained in the electrolyte.
  • Ratio of negative electrode capacity C n to positive electrode capacity C p is, for example, larger than 1.1, preferably 1.2 or 1.3 or more, more preferably 2 or more or 3 or more. .
  • the C n / C p ratio is, for example, less than 12.5, preferably 10 or less, more preferably 9 or less. These lower limit value and upper limit value can be appropriately selected and combined.
  • the C n / C p ratio may be, for example, 1.2 to 10, or 3 to 10.
  • the C n / C p ratio is in the above range, a sufficient amount of alkali metal ions can be pre-doped on the negative electrode, and the voltage of the capacitor can be increased more effectively. Further, it is easy to increase the initial voltage, which is advantageous because it makes it easy to increase the capacity of the capacitor. Furthermore, since it is not necessary to increase the volume of the positive electrode or the negative electrode more than necessary, it is easy to suppress a decrease in the capacitance density of the capacitor while ensuring a high discharge capacity.
  • the positive electrode capacity C p is a value obtained by subtracting the irreversible capacity from the theoretical value of the chargeable charge amount calculated from the amount of the positive electrode active material contained in the positive electrode.
  • the negative electrode capacity C n is a value obtained by subtracting the irreversible capacity from the theoretical value of the chargeable charge amount calculated from the amount of the negative electrode active material contained in the negative electrode.
  • C p and C n can be evaluated based on the discharge capacity measured for EDLC using the positive electrode and the half cell using the negative electrode and alkali metal, respectively.
  • the negative electrode mixture slurry may contain a binder and / or a conductive aid in addition to the negative electrode active material and the dispersion medium.
  • a dispersion medium and a binder it can select suitably from what was illustrated about the 1st electrode mixture of the 1st electrode.
  • the amount of the binder with respect to 100 parts by mass of the negative electrode active material can be appropriately selected from the range of the amount of the binder with respect to 100 parts by mass of the first electrode active material.
  • the conductive assistant is not particularly limited, and examples thereof include carbon black such as acetylene black and ketjen black; conductive compound such as ruthenium oxide; conductive fiber such as carbon fiber and metal fiber.
  • the amount of the conductive additive relative to 100 parts by mass of the negative electrode active material can be appropriately selected from the range of the amount of the conductive auxiliary relative to 100 parts by mass of the first electrode active material.
  • the thickness of the negative electrode can be appropriately selected from the range of 50 to 2000 ⁇ m, for example.
  • the thickness of the negative electrode is, for example, 100 to 2000 ⁇ m, preferably 100 to 1500 ⁇ m, or 100 to 1200 ⁇ m.
  • the electrolyte of the alkali metal ion capacitor is preferably a non-aqueous electrolyte having alkali metal ion conductivity.
  • a non-aqueous electrolyte contains a cation containing an alkali metal ion and an anion.
  • Nonaqueous electrolytes include, for example, electrolytes (organic electrolytes) in which a salt of an alkali metal ion and an anion (alkali metal salt) is dissolved in a nonaqueous solvent (or an organic solvent), as well as ions containing an alkali metal ion and an anion. Liquid or the like is used.
  • the organic electrolyte can contain an ionic liquid and / or an additive in addition to the nonaqueous solvent (organic solvent) and the alkali metal salt, but the total content of the nonaqueous solvent and the alkali metal salt in the electrolyte is: For example, it is 60% by mass or more, preferably 75% by mass or more, and more preferably 85% by mass or more.
  • the total content of the nonaqueous solvent and the alkali metal salt in the electrolyte may be, for example, 100% by mass or less, or 95% by mass or less. These lower limit values and upper limit values can be arbitrarily combined.
  • the total content of the nonaqueous solvent and the alkali metal salt in the electrolyte may be, for example, 60 to 100% by mass, or 75 to 95% by mass.
  • the “ionic liquid” is synonymous with a molten salt (molten salt) and is a liquid ionic substance composed of an anion and a cation.
  • the electrolyte can contain a nonaqueous solvent and / or an additive in addition to the ionic liquid containing alkali metal ions and anions, but the ions containing alkali metal ions and anions in the electrolyte
  • the content of the liquid is preferably 60% by mass or more, and more preferably 70% by mass or more.
  • the content of the ionic liquid containing alkali metal ions and anions in the electrolyte may be 80% by mass or more, or 90% by mass or more.
  • the content of the ionic liquid in the electrolyte is 100% by mass or less.
  • an electrolyte containing a non-aqueous solvent organic solvent
  • an electrolyte containing an ionic liquid is preferably used, and an electrolyte containing an ionic liquid and a nonaqueous solvent may be used.
  • the concentration of the alkali metal salt or alkali metal ion in the electrolyte can be appropriately selected from the range of 0.3 to 5 mol / L, for example.
  • the alkali metal ion include at least one selected from the group consisting of lithium ion, sodium ion, potassium ion, rubidium ion, and cesium ion. Of these, at least one selected from the group consisting of lithium ions and sodium ions is preferred.
  • An alkali metal ion capacitor using an electrolyte having lithium ion conductivity is also referred to as a lithium ion capacitor.
  • An alkali metal ion capacitor using an electrolyte having sodium ion conductivity is also referred to as a sodium ion capacitor.
  • the kind of the anion (first anion) constituting the alkali metal salt is not particularly limited.
  • an anion of a fluorine-containing acid anion of fluorine-containing phosphate such as hexafluorophosphate ion (PF 6 ⁇ );
  • Anion of fluorine-containing boric acid such as acid ion (BF 4 ⁇ )], anion of chlorine-containing acid [perchlorate ion (ClO 4 ⁇ ), etc.]
  • anion of oxyacid having an oxalate group bis (oxalato) borate Ions (Oxalatoborate ions such as B (C 2 O 4 ) 2 ⁇ );
  • Oxalatoborate ions such as tris (oxalato) phosphate ions (P (C 2 O 4 ) 3 ⁇ )], fluoroalkanesulfonic acid anion [trifluoromethanesulfonate ion (CF 3 SO 3
  • bissulfonylamide anion examples include bis (fluorosulfonyl) amide anion [bis (fluorosulfonyl) amide anion (N (SO 2 F) 2 ⁇ ) and the like], (fluorosulfonyl) (perfluoroalkylsulfonyl) amide Anion [(fluorosulfonyl) (trifluoromethylsulfonyl) amide anion ((FSO 2 ) (CF 3 SO 2 ) N ⁇ , etc.)], bis (perfluoroalkylsulfonyl) amide anion [bis (trifluoromethylsulfonyl) amide anion (N (SO 2 CF 3 ) 2 ⁇ ), bis (pentafluoroethylsulfonyl) amide anion (N (SO 2 C 2 F 5 ) 2 ⁇ ) and the like].
  • the carbon number of the perfluoroalkyl group is preferably
  • bis (fluorosulfonyl) amide anion FSA ⁇ : bis (fluorosulfonyl) amide anion
  • bis (trifluoromethylsulfonyl) amide anion TFSA ⁇ : bis (trifluoromethylsulfonyl) amide anion
  • bis ( A bis (perfluoroalkylsulfonyl) amide anion PFSA ⁇ : bis (perfluoroalkylsulfonyl) amide anion
  • PFSA ⁇ bis (perfluoroalkylsulfonyl) amide anion
  • the non-aqueous solvent contained in the electrolyte is not particularly limited, and known non-aqueous solvents used for alkali metal ion capacitors can be used.
  • Non-aqueous solvents include, for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; cyclic carbonates such as ⁇ -butyrolactone. Etc. can be preferably used.
  • a non-aqueous solvent may be used individually by 1 type, and may be used in combination of 2 or more type.
  • the ionic liquid containing alkali metal ions contains alkali metal ions and anions (second anions).
  • second anion various anions exemplified for the first anion, specifically, a bissulfonylamide anion, an anion of a fluorine-containing acid, an anion of a chlorine-containing acid, an anion of an oxyacid having an oxalate group, a fluoroalkanesulfonic acid Can be used.
  • a 2nd anion can be used individually by 1 type or in combination of 2 or more types.
  • the second anion preferably contains at least a bissulfonylamide anion.
  • the content of the bissulfonylamide anion in the second anion is, for example, 80 to 100 mol%, preferably 90 to 100 mol%.
  • the ionic liquid may further contain a second cation in addition to the alkali metal ion (first cation).
  • a second cation in addition to the alkali metal ion (first cation).
  • inorganic cations other than alkali metal ions such as magnesium ions, calcium ions and ammonium cations may be used, but organic cations are preferred.
  • a 2nd cation can be used individually by 1 type or in combination of 2 or more types.
  • Examples of the organic cation used as the second cation include a cation derived from an aliphatic amine, an alicyclic amine, or an aromatic amine (for example, a quaternary ammonium cation), and a cation having a nitrogen-containing heterocycle ( That is, examples include nitrogen-containing onium cations such as cations derived from cyclic amines; sulfur-containing onium cations; and phosphorus-containing onium cations.
  • nitrogen-containing organic onium cations those having pyrrolidine, pyridine, or imidazole as the nitrogen-containing heterocyclic skeleton in addition to the quaternary ammonium cation are particularly preferable.
  • the quaternary ammonium cation include tetraalkylammonium cation, tetraethylammonium cation (TEA + : tetraethylammonium cation), ethyltrimethylammonium cation, hexyltrimethylammonium cation, and methyltriethylammonium cation (TEMA + : methyltriethylammonium cation).
  • TAA + tetraethylammonium cation
  • ethyltrimethylammonium cation ethyltrimethylammonium cation
  • hexyltrimethylammonium cation methyltriethylammonium c
  • the organic onium cation having a pyrrolidine skeleton preferably has two alkyl groups on one nitrogen atom constituting the pyrrolidine ring.
  • Examples of such organic onium cations include 1,1-dimethylpyrrolidinium cation, 1,1-diethylpyrrolidinium cation, 1-ethyl-1-methylpyrrolidinium cation, and 1-methyl-1-propyl.
  • Pyrrolidinium cation (MPPY + : 1-methyl-1-pyrrolidinium cation), 1-butyl-1-methylpyrrolidinium cation (MBPY + : 1-butyl-1-methylpyrrolidinium cation), 1-ethyl-1-propyl Examples include pyrrolidinium cation.
  • the organic onium cation having a pyridine skeleton preferably has one alkyl group on one nitrogen atom constituting the pyridine ring.
  • Examples of such organic onium cations include 1-alkylpyridinium cations such as 1-methylpyridinium cation, 1-ethylpyridinium cation, and 1-propylpyridinium cation.
  • the organic onium cation having an imidazole skeleton preferably has one alkyl group on each of two nitrogen atoms constituting the imidazole ring.
  • organic onium cations include 1,3-dimethylimidazolium cation, 1-ethyl-3-methylimidazolium cation (EMI + : 1-ethyl-3-methylimidazolium cation), 1-methyl-3- Propylimidazolium cation, 1-butyl-3-methylimidazolium cation (BMI + : 1-butyl-3-methylimidazolium cation), 1-ethyl-3-propylimidazolium cation, 1-butyl-3-ethylimidazolium cation Etc.
  • imidazolium cations having a methyl group and an alkyl group having 2 to 4 carbon atoms such as EMI + and BMI + are preferable.
  • the first electrode is a positive electrode and the second electrode is a negative electrode.
  • the same electrode as the first electrode may be used as the second electrode.
  • the second electrode includes a second electrode active material.
  • the second electrode can include a second electrode current collector that holds the second electrode active material.
  • the second electrode active material includes a material that reversibly carries cations (specifically, adsorption and desorption), that is, a material that causes a non-Faraday reaction.
  • adsorption and desorption a material that causes a non-Faraday reaction.
  • the second electrode active material those exemplified for the first electrode active material can be used.
  • the first electrode active material and the second electrode active material may be the same or different.
  • the second electrode current collector may be a metal foil, but is preferably a metal porous body from the viewpoint of increasing the capacity of the capacitor.
  • the metal porous body may have a three-dimensional network skeleton (particularly, a hollow skeleton) similar to the aluminum porous body that is the first electrode current collector.
  • the material of the second electrode current collector may be aluminum or aluminum alloy exemplified for the first electrode current collector, and exemplified for the negative electrode current collector of the alkali metal ion capacitor. It may be a material.
  • the second electrode current collector can be produced in the same manner as the first electrode current collector or the negative electrode current collector of the alkali metal ion capacitor.
  • the second electrode can be produced in the same manner as the first electrode. Components and amounts other than the electrode active material contained in the second electrode can be appropriately selected from those exemplified for the first electrode and ranges.
  • the electrolyte used for EDLC may contain water or may be a non-aqueous electrolyte.
  • the electrolyte includes a cation including an organic cation and an anion.
  • As the electrolyte in addition to an electrolyte in which a salt of an organic cation and an anion (third anion) is dissolved in a non-aqueous solvent (or organic solvent), non-aqueous such as an ionic liquid containing an organic cation and an anion (fourth anion) An electrolyte is preferably used.
  • the cation may include a cation other than the organic cation, such as the alkali metal cation exemplified above and / or the inorganic cation exemplified above.
  • concentration of the organic cation in the electrolyte can be appropriately selected from the range of 0.3 to 5 mol / L, for example.
  • Examples of the organic cation include those similar to the organic cation exemplified as the second cation of the alkali metal ion capacitor.
  • the third anion can be appropriately selected from those exemplified as the first anion of the alkali metal ion capacitor.
  • As a nonaqueous solvent it can select suitably from what was illustrated about the alkali metal ion capacitor.
  • the fourth anion contained in the ionic liquid can be appropriately selected from those exemplified as the second anion of the alkali metal ion capacitor.
  • the fourth anion preferably includes at least a bissulfonylamide anion.
  • the content of the bissulfonylamide anion in the fourth anion can be selected from the same range as in the case of the second anion.
  • Content of the ionic liquid in electrolyte can be suitably selected from the range illustrated about the alkali metal ion capacitor.
  • an electrolyte containing an ionic liquid is preferably used, and an electrolyte containing an ionic liquid and an organic solvent may be used.
  • the capacitor according to the embodiment of the present invention includes, for example, (a) a step of forming an electrode group with a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode, and (b )
  • the electrode group and the electrolyte can be manufactured through a step of housing in the cell case.
  • FIG. 1 is a longitudinal sectional view schematically showing a capacitor according to an embodiment of the present invention.
  • the capacitor includes a stacked electrode group, an electrolyte (not shown), and a rectangular aluminum cell case 10 for housing them.
  • the cell case 10 includes a bottomed container body 12 having an upper opening and a lid 13 that closes the upper opening.
  • an electrode group is formed by laminating the first electrode 2 and the second electrode 3 with the separator 1 interposed therebetween, and the configured electrode group is a cell case.
  • 10 container bodies 12 are inserted.
  • a step of injecting an electrolyte into the container main body 12 and impregnating the electrolyte in the gaps of the separator 1, the first electrode 2, and the second electrode 3 constituting the electrode group is performed.
  • the electrolyte includes an ionic liquid
  • the electrode group may be impregnated in the electrolyte, and then the electrode group including the electrolyte may be accommodated in the container body 12.
  • a safety valve 16 is provided for releasing gas generated inside when the internal pressure of the cell case 10 rises.
  • An external positive terminal 14 that penetrates the lid 13 is provided near the one side of the lid 13 with the safety valve 16 in the center, and an external that penetrates the lid 13 is located near the other side of the lid 13.
  • a negative terminal is provided.
  • the stacked electrode group is composed of a plurality of first electrodes 2, a plurality of second electrodes 3, and a plurality of separators 1 interposed between them, each having a rectangular sheet shape.
  • the separator 1 is formed in a bag shape so as to surround the first electrode 2, but the form of the separator is not particularly limited.
  • the plurality of first electrodes 2 and the plurality of second electrodes 3 are alternately arranged in the stacking direction within the electrode group.
  • An electrode lead piece 2 a may be formed at one end of each first electrode 2.
  • the plurality of first electrodes 2 are connected in parallel by bundling the electrode lead pieces 2 a of the plurality of first electrodes 2 and connecting them to the external electrode terminals 14 provided on the lid 13 of the cell case 10.
  • an electrode lead piece 3 a may be formed at one end of each second electrode 3.
  • the plurality of second electrodes 3 are connected in parallel by bundling the electrode lead pieces 3 a of the plurality of second electrodes 3 and connecting them to external electrode terminals provided on the lid 13 of the cell case 10. It is desirable that the bundle of electrode lead pieces 2a and the bundle of electrode lead pieces 3a are arranged on the left and right sides of one end face of the electrode group with a space so as to avoid mutual contact.
  • the external electrode terminal 14 has a columnar shape, and at least a portion exposed to the outside has a screw groove.
  • a nut 7 is fitted in the screw groove of each terminal, and the nut 7 is fixed to the lid 13 by rotating the nut 7.
  • a flange 8 is provided in a portion of each terminal accommodated in the cell case 10, and the flange 8 is fixed to the inner surface of the lid 13 via a washer 9 by the rotation of the nut 7. .
  • the electrode group is not limited to the laminated type, and may be formed by winding the first electrode and the second electrode through a separator.
  • the dimension of the negative electrode may be larger than that of the positive electrode from the viewpoint of preventing alkali metal from being deposited on the negative electrode.
  • the capacitor according to the embodiment of the present invention can stably charge and discharge even when the upper limit voltage of charging and discharging is increased, and can improve durability during charging and discharging.
  • the upper limit voltage of charging / discharging can be increased, the capacity of the electrode active material can be used effectively, and the capacity of the capacitor can be increased.
  • the charge / discharge method includes a step of charging / discharging a capacitor with an upper limit voltage equal to or higher than the voltage V 2 (that is, a voltage equal to or higher than the upper limit voltage V 2 ).
  • Capacitor has an upper limit voltage of the voltage V 2 or more charge-discharge (i.e., charging).
  • the upper limit voltage of charging / discharging (that is, charging) is preferably higher than 4.2V, and more preferably 4.3V or higher.
  • the upper limit voltage may be 4.4 V or higher or 4.5 V or higher.
  • an upper limit voltage can also be made into the value exceeding 5V, it is preferable that it is 5V or less, and 4.9V or less or 4.7V or less may be sufficient. These lower limit values and upper limit values can be arbitrarily combined.
  • the upper limit voltage of charging may be, for example, more than 4.2V and 5V or less, 4.3 to 5V, or 4.5 to 5V.
  • the upper limit voltage for charging and discharging a capacitor cannot be determined freely by the user, but is a characteristic of the capacitor determined at the time of designing the capacitor according to the component of the capacitor.
  • Charging and discharging of the capacitor is usually performed within a preset voltage range. Specifically, the capacitor is charged until a preset upper limit voltage is reached, and the capacitor is discharged until a preset end voltage is reached.
  • Charging and discharging are usually performed by a charge control unit and a discharge control unit in a charge / discharge system including a capacitor.
  • Embodiments of the present invention also include a charge / discharge system including a capacitor, a charge control unit that controls charging of the capacitor, and a discharge control unit that controls discharge of the capacitor.
  • the discharge control unit may include a load device that consumes power supplied from the capacitor.
  • FIG. 2 is a block diagram schematically showing a charge / discharge system according to an embodiment of the present invention.
  • the charge / discharge system 100 includes a capacitor 101, a charge / discharge control unit 102 that controls charge / discharge of the capacitor 101, and a load device 103 that consumes power supplied from the capacitor 101.
  • the charge / discharge control unit 102 includes a charge control unit 102a that controls current and / or voltage when the capacitor 101 is charged, and a discharge control unit 102b that controls current and / or voltage when the capacitor 101 is discharged. including.
  • the charge control unit 102 a is connected to the external power source 104 and the capacitor 101, and the discharge control unit 102 b is connected to the capacitor 101.
  • a load device 103 is connected to the capacitor 101.
  • a first electrode including a first electrode active material; a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material; and being interposed between the first electrode and the second electrode.
  • a capacitor comprising a separator and an electrolyte comprising an anion and a cation
  • the capacitor is an alkali metal ion capacitor or an electric double layer capacitor
  • the first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
  • the first electrode active material includes at least a material that reversibly supports the anion,
  • the content of the first electrode mixture in the first electrode is 30 to 90% by mass,
  • the density of the first electrode is 0.3 to 1.1 g / cm 3
  • Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
  • the upper limit voltage V 1 is 3.8V
  • the upper limit voltage V 2 is 4.2V
  • the upper limit voltage V 1 is 2.5V
  • the upper limit voltage V 1 is
  • the first electrode current collector has a hollow skeleton, Ratio of capacity C 3 when charging / discharging with upper limit voltage of 4.5V with respect to capacity C 1 : C 3 / C 1 is 1.7 or more,
  • the thickness of the first electrode is preferably 150 to 1500 ⁇ m. In such a capacitor, even when it is charged to an upper limit voltage of 4.5 V or more, charging and discharging can be performed stably and reversibly, and a decrease in capacity due to charging and discharging can be suppressed. As a result, the durability of the capacitor Can be improved more effectively.
  • a charge / discharge system including the capacitor according to Supplementary Note 1, a charge control unit that controls charging of the capacitor, and a discharge control unit that controls discharge of the capacitor.
  • Example 1 A lithium ion capacitor was produced according to the following procedure.
  • the foam having the conductive layer formed on the surface was immersed in a molten salt aluminum plating bath, and a direct current having a current density of 3.6 A / dm 2 was applied for 90 minutes to form an aluminum layer.
  • the mass of the aluminum layer per apparent area of the foam was 150 g / m 2 .
  • the molten salt aluminum plating bath contained 33 mol% 1-ethyl-3-methylimidazolium chloride and 67 mol% aluminum chloride, and the temperature was 40 ° C.
  • the foam with the aluminum layer formed on the surface was immersed in a lithium chloride-potassium chloride eutectic molten salt at 500 ° C., and a negative potential of ⁇ 1 V was applied for 30 minutes to decompose the foam.
  • the obtained aluminum porous body was taken out from the molten salt, cooled, washed with water, and dried to obtain a positive electrode current collector.
  • the obtained positive electrode current collector has a three-dimensional network-like porous structure in which pores communicate, reflecting the pore shape of the foam, has a porosity of 94% by volume, and an average pore diameter of 550 ⁇ m.
  • the BET specific surface area was 350 cm 2 / g, and the thickness was 1100 ⁇ m.
  • the three-dimensional mesh-like aluminum skeleton had a communication hole-like cavity formed by removing the foam. In this way, a positive electrode current collector was obtained.
  • a Cu film having a basis weight of 5 g / cm 2 is formed on the surface of the same thermosetting polyurethane foam as used in the production of the positive electrode current collector ( Conductive layer) was formed.
  • a foam having a conductive layer formed on the surface was used as a work, immersed in a copper sulfate plating bath, and a direct current having a cathode current density of 2 A / dm 2 was applied to form a Cu layer on the surface.
  • the copper sulfate plating bath contained 250 g / L copper sulfate, 50 g / L sulfuric acid, and 30 g / L copper chloride, and the temperature was 30 ° C.
  • the foam with the Cu layer formed on the surface is heat-treated at 700 ° C. in an air atmosphere to decompose the foam, and then fired in a hydrogen atmosphere to reduce the oxide film formed on the surface.
  • a copper porous body (negative electrode current collector) was obtained.
  • the obtained negative electrode current collector had a three-dimensional network-like porous structure in which pores communicated, reflecting the pore shape of the foam, had a porosity of 92% by volume, and an average pore diameter of 550 ⁇ m.
  • the BET specific surface area was 200 cm 2 / g.
  • the three-dimensional network copper skeleton had a communication hole-like cavity formed by removing the foam.
  • a negative electrode mixture slurry was prepared by mixing artificial graphite powder as a negative electrode active material, acetylene black as a conductive additive, PVDF as a binder, and NMP as a dispersion medium. .
  • the mass ratio of the graphite powder, acetylene black, and PVDF was 90: 5: 5.
  • the obtained negative electrode mixture slurry was filled in the current collector obtained in the step (a) and dried at 100 ° C. for 30 minutes. The dried product was rolled using a pair of rolls to produce a negative electrode having a thickness of 130 ⁇ m.
  • steps (1) and (2) the filling amounts of the positive electrode mixture and the negative electrode mixture were adjusted so that the chargeable capacity of the negative electrode after pre-doping was about twice the capacity of the positive electrode.
  • a lithium foil (thickness: 50 ⁇ m) is pressure-bonded to one surface of a punching copper foil (thickness: 20 ⁇ m, opening diameter: 50 ⁇ m, opening ratio 50%, 2 cm ⁇ 2 cm) as a current collector.
  • a lithium electrode was produced.
  • a nickel lead was welded to the other surface of the current collector of the lithium electrode.
  • a single-cell electrode group was formed by laminating a positive electrode and a negative electrode with a cellulose separator (thickness: 60 ⁇ m) interposed between the positive electrode and the negative electrode. Further, a lithium separator is disposed on the negative electrode side of the electrode group with a polyolefin separator (a laminate of a polyethylene microporous membrane and a polypropylene microporous membrane), and the obtained laminate is made of an aluminum laminate sheet. It accommodated in the produced cell case.
  • an electrolyte was injected into the cell case, and the positive electrode, the negative electrode, and the separator were impregnated.
  • a solution in which LiPF 6 as a lithium salt was dissolved to a concentration of 1.0 mol / L in a mixed solvent containing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 was used.
  • the cell case was sealed while reducing the pressure with a vacuum sealer.
  • the negative electrode lead wire and the lithium electrode lead wire were connected to a power source outside the cell case.
  • the cell in this state was allowed to stand for a predetermined time in a thermostat at 30 ° C. so that the temperature of the electrolyte was the same as the temperature of the thermostat.
  • a lithium ion capacitor (A1) was produced by pre-doping lithium into the negative electrode active material.
  • the design capacity of the lithium ion capacitor A1 was about 1.0 mAh / cm 2 when charged at 3.8V.
  • Electrode density The positive electrode density (g / cm 3 ) was calculated by measuring the mass of the positive electrode and dividing this mass by the apparent volume of the positive electrode.
  • Capacitor Capacitor The capacitor was charged with a current of 1 mA / cm 2 to an upper limit voltage of 3.8 V and discharged with a current of 1 mA / cm 2 until the voltage reached 2.2 V. This charge / discharge cycle was repeated 10 times, and the discharge capacity C 1 (mAh) at the 10th discharge was determined.
  • the upper limit voltage of charging except for changing the 4.2V or 4.5V, in the same manner as described above, the discharge capacity C 2 and C 3 determined, the ratio C 2 / C 1 and of the discharge capacity with respect to C 1 C 3 / C 1 was calculated.
  • Comparative Examples 1 and 2 A positive electrode was produced in the same manner as in Example 1 except that an aluminum foil (thickness 20 ⁇ m) was used as the positive electrode current collector, and the positive electrode mixture slurry was applied to one surface of the aluminum foil to form a positive electrode mixture layer. .
  • the coating amount of the positive electrode mixture slurry and the compression ratio when compressing with a roll were appropriately changed so that the density and thickness of the positive electrode were as shown in Table 1.
  • Lithium ion capacitors (B1 and B2) were produced and evaluated in the same manner as in Example 1 except that the obtained positive electrode was used.
  • Examples 2 and 3 and Comparative Example 3 The positive electrode and the negative electrode were changed in the same manner as in Example 1 except that the filling amount of the mixture and the compressibility when the dried product was compressed using a roll were changed so that the thicknesses of the positive electrode and the negative electrode were as shown in Table 1. A negative electrode was produced. At this time, the capacity balance between the positive electrode and the negative electrode was made substantially the same as in Example 1. Lithium ion capacitors (A2, A3 and B3) were prepared and evaluated in the same manner as in Example 1 except that the obtained positive and negative electrodes were used. The results of Examples and Comparative Examples are shown in Table 1 together with the density of the positive electrode, the content and thickness of the positive electrode mixture in the positive electrode. The lithium ion capacitors A1 to A3 are examples, and B1 to B3 are comparative examples.
  • the upper limit voltage is as high as 4.2 V (V 2 ) or 4.5 V (V 3 ). Even if charging / discharging was repeated, a high discharge capacity was maintained even when charging / discharging was repeated, and excellent durability was obtained. In the lithium ion capacitors B1 and B2 using the aluminum foil as the positive electrode current collector, the capacity improvement effect was small even when the upper limit voltage was increased to 4.2 V or 4.5 V, and the behavior was different from that of the example.
  • the values of the capacitance ratios C2 / C1 and C3 / C1 are small, and it can be said that the effect of increasing the upper limit voltage is hardly obtained.
  • the values of the capacity ratios C2 / C1 and C3 / C1 were larger than those of the lithium ion capacitor B1, but were lower than those of the examples, and the value of the discharge capacity after the cycle itself was also small.
  • the values of the capacitance ratios C2 / C1 and C3 / C1 are approximately the same as those of the lithium ion capacitor B2, and compared with the example, The value of the discharge capacity after the cycle was small, and the durability was inferior.
  • the same or similar result as a lithium ion capacitor is obtained also about EDLC.
  • V 1 is 2.5 V
  • V 2 is 2.9 V
  • V 3 is 3.2 V
  • the capacitor according to one embodiment of the present invention can stably charge and discharge reversibly even when the charging voltage is increased, a capacitor having excellent durability can be obtained. Therefore, it can be applied to various uses that require durability (or high cycle characteristics).
  • DESCRIPTION OF SYMBOLS 100 Charge / discharge system 101: Capacitor 102: Charge / discharge control unit 102a: Charge control unit 102b: Discharge control unit 103: Load apparatus

Abstract

Provided is an exceptionally durable capacitor which enables charging/discharging in a stable manner even when the upper limit voltage for charging/discharging is increased. The capacitor includes a first electrode containing a first electrode active material, a second electrode having an opposite polarity to that of the first electrode and containing a second electrode active material, a separator interposed between the first and second electrodes, and an electrolyte containing anions and cations. The first electrode contains a three-dimensional mesh-like first electrode collector containing Al or an Al alloy, and a first electrode mixture packed into the first electrode collector. The amount of the first electrode mixture contained in the first electrode is 30-90 mass%, the density of the first electrode is 0.3-1.1 g/cm3, and the ratio C2/C1 of the capacitance C2 when charging/discharging is performed at an upper limit voltage V2 relative to the capacitance C1 when charging/discharging is performed at an upper limit voltage V1 is 1.3 or above. In an alkali metal ion capacitor, V1 is 3.8V and V2 is 4.2V. In an electric double layer capacitor, V1 is 2.5V and V2 is 2.9V.

Description

キャパシタおよびその充放電方法Capacitor and charging / discharging method thereof
　本発明は、高い充電上限電圧で充放電されるキャパシタおよびその充放電方法に関する。 The present invention relates to a capacitor charged and discharged at a high charge upper limit voltage and a method for charging and discharging the same.
　環境問題がクローズアップされる中、太陽光または風力などのクリーンエネルギーを電力に変換し、電気エネルギーとして蓄電するシステムの開発が盛んに行われている。このような蓄電デバイスとしては、リチウムイオン二次電池、電気二重層キャパシタ（ＥＤＬＣ：ｅｌｅｃｔｒｉｃ　ｄｏｕｂｌｅ－ｌａｙｅｒ　ｃａｐａｃｉｔｏｒ）、リチウムイオンキャパシタなどが知られている。最近では、瞬時の充放電特性に優れるとともに、高い出力特性が得られ、取り扱い性に優れるといった観点から、ＥＤＬＣおよびリチウムイオンキャパシタなどのキャパシタが注目されている。 中 Amid the close-up of environmental issues, systems that convert clean energy such as solar or wind power into electric power and store it as electric energy are being actively developed. As such an electricity storage device, a lithium ion secondary battery, an electric double-layer capacitor (EDLC), a lithium ion capacitor, and the like are known. Recently, capacitors such as EDLCs and lithium ion capacitors have attracted attention from the viewpoints of excellent instantaneous charge / discharge characteristics, high output characteristics, and excellent handleability.
　リチウムイオンキャパシタは、一般に、電極活物質として活性炭などの多孔質炭素材料を含む正極と、電極活物質としてリチウムイオンを吸蔵および放出する材料を含む負極と、リチウムイオン伝導性の非水電解質とを含む。ＥＤＬＣは、一般に、電極活物質としてアニオンを吸着および脱離する多孔質炭素材料を含む正極と、電極活物質としてカチオンを吸着および脱離する多孔質炭素材料を含む負極と、アニオンおよびカチオンを含む電解質とを含む。 Generally, a lithium ion capacitor includes a positive electrode including a porous carbon material such as activated carbon as an electrode active material, a negative electrode including a material that absorbs and releases lithium ions as an electrode active material, and a lithium ion conductive nonaqueous electrolyte. Including. EDLC generally includes a positive electrode including a porous carbon material that adsorbs and desorbs anions as an electrode active material, a negative electrode including a porous carbon material that adsorbs and desorbs cations as an electrode active material, and an anion and a cation. An electrolyte.
　リチウムイオンキャパシタの正極、ならびにＥＤＬＣの正極および負極は、一般に、電極集電体としてのアルミニウム箔と、このアルミニウム箔上に形成され、かつ電極活物質を含む電極合剤層とを有する。電極合剤は、電極活物質に加え、導電助剤および／またはバインダを含む。 A positive electrode of a lithium ion capacitor and a positive electrode and a negative electrode of an EDLC generally have an aluminum foil as an electrode current collector and an electrode mixture layer formed on the aluminum foil and containing an electrode active material. The electrode mixture includes a conductive additive and / or a binder in addition to the electrode active material.
　例えば、特許文献１では、アルミニウム箔上に、正極活物質としての活性炭粉末を含むスラリーを塗布し、乾燥して得られる正極が、リチウムイオンキャパシタに使用されている。特許文献２では、ＥＤＬＣの電極集電体としてアルミニウム箔が使用されている。
　また、特許文献３には、ＥＤＬＣの電極集電体として、発泡アルミニウムを使用することが提案されている。 For example, in patent document 1, the positive electrode obtained by apply | coating the slurry containing activated carbon powder as a positive electrode active material on aluminum foil, and drying is used for the lithium ion capacitor. In Patent Document 2, an aluminum foil is used as an electrode current collector of EDLC.
Patent Document 3 proposes to use aluminum foam as an EDLC electrode current collector.
特開２０１３－１５７６０３号公報JP 2013-157603 A 特開２０１３－１６８４８５号公報JP 2013-168485 A 特開２０１２－９４７３７号公報JP 2012-94737 A
　従来、リチウムイオンキャパシタなどのアルカリ金属イオンキャパシタは、充電の上限電圧が３．８Ｖ程度までの範囲で充放電され、ＥＤＬＣは、充電の上限電圧が２．５Ｖ程度までの範囲で充放電される。キャパシタを高容量化するには、充放電の上限電圧を高めるのが有利である。しかし、充電の上限電圧がこれらの電圧値を超えて高くなると、充放電による電極の劣化が顕著になり、キャパシタの耐久性（またはサイクル特性）が低下する。 Conventionally, an alkali metal ion capacitor such as a lithium ion capacitor is charged / discharged in a range where the upper limit voltage of charging is up to about 3.8V, and an EDLC is charged / discharged in a range where the upper limit voltage of charging is up to about 2.5V. . In order to increase the capacity of the capacitor, it is advantageous to increase the upper limit voltage for charging and discharging. However, when the upper limit voltage for charging exceeds these voltage values, the electrode is significantly deteriorated due to charging / discharging, and the durability (or cycle characteristics) of the capacitor is lowered.
　特に、特許文献１および特許文献２に記載されるようなアルミニウム箔を集電体として用いた場合、上記のような従来の上限電圧を超えるような高い上限電圧で充放電を行うと、電極の劣化が顕著になり易い。また、キャパシタの充放電の上限電圧を高めると、バインダが劣化して、充放電時に、電極活物質が脱落したり、および／または電極合剤層が剥がれたりして、実際に容量を高めることは難しい。 In particular, when an aluminum foil as described in Patent Document 1 and Patent Document 2 is used as a current collector, when charging / discharging at a high upper limit voltage exceeding the conventional upper limit voltage as described above, Deterioration tends to be remarkable. In addition, when the upper limit voltage of charge / discharge of the capacitor is increased, the binder deteriorates, and the electrode active material falls off and / or the electrode mixture layer peels off during charge / discharge, which actually increases the capacity. Is difficult.
　本発明の目的は、充放電の上限電圧を高めても、充放電を安定に行うことができ、耐久性に優れるキャパシタを提供することである。 An object of the present invention is to provide a capacitor that can stably charge and discharge even when the upper limit voltage of charging and discharging is increased and has excellent durability.
　本発明の一局面は、第１電極活物質を含む第１電極、前記第１電極と反対の極性を有し、かつ第２電極活物質を含む第２電極、前記第１電極と前記第２電極との間に介在するセパレータ、ならびにアニオンおよびカチオンを含む電解質を含むキャパシタであって、
　前記キャパシタは、アルカリ金属イオンキャパシタまたはＥＤＬＣであり、
　前記第１電極は、アルミニウムまたはアルミニウム合金を含む三次元網目状の第１電極集電体と、前記第１電極集電体に充填され、かつ前記第１電極活物質を含む第１電極合剤とを含み、
　前記第１電極活物質は、少なくとも前記アニオンを可逆的に担持する材料を含み、
　前記第１電極中の前記第１電極合剤の含有量は、３０～９０質量％であり、
　前記第１電極の密度は、０．３～１．１ｇ／ｃｍ3であり、
　上限電圧Ｖ1で充放電したときの容量Ｃ1に対する上限電圧Ｖ2で充放電したときの容量Ｃ2の比：Ｃ2／Ｃ1は、１．３以上であり、
　前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ1は３．８Ｖであり、前記上限電圧Ｖ2は４．２Ｖであり、
　前記ＥＤＬＣにおいて、前記上限電圧Ｖ1は２．５Ｖであり、前記上限電圧Ｖ2は２．９Ｖであるキャパシタに関する。 One aspect of the present invention is a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, the first electrode, and the second electrode. A capacitor including a separator interposed between electrodes and an electrolyte containing an anion and a cation,
The capacitor is an alkali metal ion capacitor or EDLC,
The first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
The first electrode active material includes at least a material that reversibly supports the anion,
The content of the first electrode mixture in the first electrode is 30 to 90% by mass,
The density of the first electrode is 0.3 to 1.1 g / cm 3 ,
Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
In the alkali metal ion capacitor, the upper limit voltage V 1 is 3.8V, the upper limit voltage V 2 is 4.2V,
In the EDLC, the upper limit voltage V 1 is 2.5V and the upper limit voltage V 2 is 2.9V.
　本発明の他の一局面は、キャパシタの充放電方法であって、
　前記キャパシタは、第１電極活物質を含む第１電極、前記第１電極と反対の極性を有し、かつ第２電極活物質を含む第２電極、前記第１電極と前記第２電極との間に介在するセパレータ、ならびにアニオンおよびカチオンを含む電解質を含むアルカリ金属イオンキャパシタまたはＥＤＬＣであり、
　前記第１電極は、アルミニウムまたはアルミニウム合金を含む三次元網目状の第１電極集電体と、前記第１電極集電体に充填され、かつ前記第１電極活物質を含む第１電極合剤とを含み、
　前記第１電極活物質は、少なくとも前記アニオンを可逆的に担持する材料を含み、
　前記第１電極中の前記第１電極合剤の含有量は、３０～９０質量％であり、
　前記第１電極の密度は、０．３～１．１ｇ／ｃｍ3であり、
　上限電圧Ｖ1で充放電したときの容量Ｃ1に対する上限電圧Ｖ2で充放電したときの容量Ｃ2の比：Ｃ2／Ｃ1は、１．３以上であり、
り、
　前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ1は３．８Ｖであり、前記上限電圧Ｖ2は４．２Ｖであり、
　前記ＥＤＬＣにおいて、前記上限電圧Ｖ1は２．５Ｖであり、前記上限電圧Ｖ2は２．９Ｖであり、
　前記キャパシタを、前記上限電圧Ｖ2以上の上限電圧で充放電する工程を有する充放電方法に関する。 Another aspect of the present invention is a method for charging and discharging a capacitor,
The capacitor includes a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, and the first electrode and the second electrode. An alkali metal ion capacitor or EDLC comprising an intervening separator and an electrolyte containing anions and cations,
The first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
The first electrode active material includes at least a material that reversibly supports the anion,
The content of the first electrode mixture in the first electrode is 30 to 90% by mass,
The density of the first electrode is 0.3 to 1.1 g / cm 3 ,
Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
The
In the alkali metal ion capacitor, the upper limit voltage V 1 is 3.8V, the upper limit voltage V 2 is 4.2V,
In the EDLC, the upper limit voltage V 1 is 2.5V, the upper limit voltage V 2 is 2.9V,
It said capacitor, to charge and discharge method having a step of charging and discharging at the upper limit voltage V 2 or more the upper limit voltage.
　本発明の上記局面によれば、キャパシタの充放電の上限電圧を高めても（例えば、アルカリ金属イオンキャパシタでは４．２Ｖ以上、ＥＤＬＣでは２．９Ｖ以上に高めても）、充放電を安定に行うことができ、耐久性に優れるキャパシタを提供できる。 According to the above aspect of the present invention, even if the upper limit voltage of charging / discharging of the capacitor is increased (for example, it is increased to 4.2 V or higher for an alkali metal ion capacitor and 2.9 V or higher for EDLC), charging / discharging is stably performed. The capacitor which can be performed and is excellent in durability can be provided.
本発明の一実施形態に係るキャパシタを概略的に示す縦断面図である。1 is a longitudinal sectional view schematically showing a capacitor according to an embodiment of the present invention. 本発明の一実施形態に係る充放電システムを概略的に示す構成図である。It is a lineblock diagram showing roughly the charge and discharge system concerning one embodiment of the present invention.
［発明の実施形態の説明］
　最初に、本発明の実施形態の内容を列記して説明する。
　本発明の一実施形態は、（１）第１電極活物質を含む第１電極、前記第１電極と反対の極性を有し、かつ第２電極活物質を含む第２電極、前記第１電極と前記第２電極との間に介在するセパレータ、ならびにアニオンおよびカチオンを含む電解質を含むキャパシタであって、
　前記キャパシタは、アルカリ金属イオンキャパシタまたは電気二重層キャパシタであり、
　前記第１電極は、アルミニウムまたはアルミニウム合金を含む三次元網目状の第１電極集電体と、前記第１電極集電体に充填され、かつ前記第１電極活物質を含む第１電極合剤とを含み、
　前記第１電極活物質は、少なくとも前記アニオンを可逆的に担持する材料を含み、
　前記第１電極中の前記第１電極合剤の含有量は、３０～９０質量％であり、
　前記第１電極の密度は、０．３～１．１ｇ／ｃｍ3であり、
　上限電圧Ｖ1で充放電したときの容量Ｃ1に対する上限電圧Ｖ2で充放電したときの容量Ｃ2の比：Ｃ2／Ｃ1は、１．３以上であり、
　前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ1は３．８Ｖであり、前記上限電圧Ｖ2は４．２Ｖであり、
　前記電気二重層キャパシタにおいて、前記上限電圧Ｖ1は２．５Ｖであり、前記上限電圧Ｖ2は２．９Ｖであるキャパシタに関する。 [Description of Embodiment of the Invention]
First, the contents of the embodiment of the present invention will be listed and described.
In one embodiment of the present invention, (1) a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, the first electrode A capacitor interposed between the separator and the second electrode, and an electrolyte containing an anion and a cation,
The capacitor is an alkali metal ion capacitor or an electric double layer capacitor,
The first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
The first electrode active material includes at least a material that reversibly supports the anion,
The content of the first electrode mixture in the first electrode is 30 to 90% by mass,
The density of the first electrode is 0.3 to 1.1 g / cm 3 ,
Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
In the alkali metal ion capacitor, the upper limit voltage V 1 is 3.8V, the upper limit voltage V 2 is 4.2V,
In the electric double layer capacitor, the upper limit voltage V 1 is 2.5V and the upper limit voltage V 2 is 2.9V.
　一般に、キャパシタの容量を高めるには、キャパシタの充放電の上限電圧を高めることが有効であると考えられる。しかし、上限電圧を高めると、充放電により電極が劣化し易くなり、キャパシタの耐久性（またはサイクル特性）が低下する。特に、アルミニウム箔などの金属箔を電極集電体として用いた従来のキャパシタでは、キャパシタの充放電の上限電圧を高めると、電極合剤に含まれるバインダが劣化し易くなり、充放電時に、電極活物質が脱落したり、および／または電極合剤層が剥がれたりして、実際に容量を高めることは難しい。 Generally, in order to increase the capacity of a capacitor, it is considered effective to increase the upper limit voltage for charging and discharging the capacitor. However, when the upper limit voltage is increased, the electrode is likely to deteriorate due to charge / discharge, and the durability (or cycle characteristics) of the capacitor is reduced. In particular, in a conventional capacitor using a metal foil such as an aluminum foil as an electrode current collector, if the upper limit voltage of charge and discharge of the capacitor is increased, the binder contained in the electrode mixture is likely to be deteriorated. It is difficult to actually increase the capacity due to falling off of the active material and / or peeling of the electrode mixture layer.
　また、キャパシタの容量を高めるためには、電極の密度を高くすることも有効であると考えられている。発泡アルミニウムなどの金属多孔体を電極集電体として用いた場合、金属箔を用いる場合よりも電極密度を高め易いと考えられる。このような観点から、通常は、電極密度を大きく（例えば、１．１ｇ／ｃｍ3よりも大きく）する。しかし、金属多孔体を用いた場合、充放電の上限電圧を高めても、電極の状態によっては、容量を高められない場合がある。具体的には、電極密度が１．１ｇ／ｃｍ3よりも大きい場合、充放電の上限電圧を高めると、充放電により容量が低下する（つまり、耐久性が低下する）。 It is also considered effective to increase the density of the electrodes in order to increase the capacitance of the capacitor. When a metal porous body such as foamed aluminum is used as the electrode current collector, it is considered that the electrode density can be increased more easily than when a metal foil is used. From such a viewpoint, the electrode density is usually increased (for example, greater than 1.1 g / cm 3 ). However, when a metal porous body is used, even if the upper limit voltage of charge / discharge is increased, the capacity may not be increased depending on the state of the electrode. Specifically, when the electrode density is larger than 1.1 g / cm 3 , increasing the charge / discharge upper limit voltage decreases the capacity due to charge / discharge (that is, the durability decreases).
　本発明の実施形態では、三次元網目状の電極集電体を用いることで、電極合剤を骨格内に安定に保持することができる。また、電極密度を上記の特定の範囲に制御することで、高い上限電圧まで充放電を行うことによる電極の劣化を抑制できる。具体的には、高い上限電圧まで充放電を行っても、電極合剤（特に、電極活物質）の脱落および／または剥離を抑制することができる。従って、充放電による容量の低下を抑制でき、その結果、耐久性（またはサイクル特性）を向上できる。 In the embodiment of the present invention, the electrode mixture can be stably held in the skeleton by using a three-dimensional network electrode current collector. In addition, by controlling the electrode density to the above specific range, it is possible to suppress deterioration of the electrode due to charge / discharge up to a high upper limit voltage. Specifically, even if charging / discharging is performed up to a high upper limit voltage, dropping and / or peeling of the electrode mixture (particularly, the electrode active material) can be suppressed. Therefore, the capacity | capacitance fall by charging / discharging can be suppressed, As a result, durability (or cycling characteristics) can be improved.
　充放電の上限電圧が、一般的なキャパシタの上限電圧（具体的には、上記電圧Ｖ1）付近である場合には、充放電による容量の低下が小さいため、電極密度を上記の範囲に制御することによる効果はほとんどない。ところが、上限電圧が上記電圧Ｖ1を超える高い電圧（具体的には、上記電圧Ｖ2以上）である場合には、電極密度を上記の範囲とすることにより、耐久性を格段に向上できる。従って、上記の特定の範囲の電極密度による耐久性の向上効果は、充放電の上限電圧を電圧Ｖ2以上の高い電圧まで高めたときに初めて得られる効果であると言える。 When the upper limit voltage of charging / discharging is near the upper limit voltage of a general capacitor (specifically, the voltage V 1 ), the decrease in capacity due to charging / discharging is small, so the electrode density is controlled within the above range. There is almost no effect by doing. However, when the upper limit voltage is a high voltage exceeding the voltage V 1 (specifically, the voltage V 2 or more), the durability can be remarkably improved by setting the electrode density within the above range. Therefore, it can be said that the effect of improving the durability due to the electrode density in the above specific range is an effect obtained only when the upper limit voltage of charging / discharging is increased to a high voltage of V 2 or higher.
　このように、本発明の実施形態によれば、キャパシタの充放電の上限電圧を、例えば、電圧Ｖ2以上に高めても、充放電を安定に行うことができる。また、充放電の上限電圧を高めても、充放電による容量の低下を抑制できるため、キャパシタの耐久性を向上できる。
　電極の密度とは、電極の単位見かけ体積（１ｃｍ3）当たりの電極の質量（つまり、見かけ密度）を意味する。なお、電極の質量とは、集電体の質量を含み、具体的には、集電体と電極合剤との合計質量である。 As described above, according to the embodiment of the present invention, even when the upper limit voltage for charging and discharging the capacitor is increased to, for example, the voltage V 2 or more, charging and discharging can be performed stably. Moreover, even if the upper limit voltage of charging / discharging is increased, a decrease in capacity due to charging / discharging can be suppressed, so that the durability of the capacitor can be improved.
The density of the electrode means the mass (that is, the apparent density) of the electrode per unit apparent volume (1 cm 3 ) of the electrode. In addition, the mass of the electrode includes the mass of the current collector, and specifically, is the total mass of the current collector and the electrode mixture.
　容量Ｃ１およびＣ２、ならびに後述の容量Ｃ３は、それぞれ、同じ電流レートで充放電を行った場合の容量とする。これらの容量は、第２電極に対向する第１電極の面積当たりの電流が０．１～１０ｍＡ／ｃｍ2の条件で測定することが好ましい。 Capacitances C1 and C2 and a later-described capacitance C3 are capacities when charging / discharging at the same current rate, respectively. These capacities are preferably measured under the condition that the current per area of the first electrode facing the second electrode is 0.1 to 10 mA / cm 2 .
　（２）好ましい態様では、前記第１電極集電体は、中空の骨格を有する。このような電極集電体は、軽量であるとともに、電極集電体の中空の骨格は、トンネル状またはチューブ状になっているため、キャパシタ内で電解質がより流通し易くなる。 (2) In a preferred embodiment, the first electrode current collector has a hollow skeleton. Such an electrode current collector is lightweight, and the hollow skeleton of the electrode current collector has a tunnel shape or a tube shape, so that the electrolyte can easily flow in the capacitor.
　（３）前記容量Ｃ1に対する上限電圧Ｖ3で充放電したときの容量Ｃ3の比：Ｃ3／Ｃ1は、１．７以上であり、前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ3は４．５Ｖであり、前記電気二重層キャパシタにおいて、前記上限電圧Ｖ3は３．２Ｖであることが好ましい。このような特徴を有するキャパシタでは、電圧Ｖ3以上の上限電圧まで充電しても、安定に充放電を可逆的に行うことができ、キャパシタの耐久性を向上できる。 (3) the ratio of the capacitance C 3 when the charging and discharging with the upper limit voltage V 3 with respect to the capacitance C 1: C 3 / C 1 is less than 1.7, in the alkali metal ion capacitor, the upper limit voltage V 3 Is 4.5 V, and in the electric double layer capacitor, the upper limit voltage V 3 is preferably 3.2 V. In the capacitor having such a feature, even when it is charged up to an upper limit voltage equal to or higher than the voltage V 3 , charging and discharging can be performed stably and reversibly, and the durability of the capacitor can be improved.
　（４）前記第１電極の厚みは、１００～２０００μｍであることが好ましい。第１電極がこのような厚みを有することにより、高い容量が得られ易くなる。また、このような厚みを有する第１電極は、電極活物質の保持力が高く、耐久性の向上に有利である。 (4) The thickness of the first electrode is preferably 100 to 2000 μm. When the first electrode has such a thickness, a high capacity is easily obtained. In addition, the first electrode having such a thickness has a high retention capacity of the electrode active material, which is advantageous in improving durability.
　（５）好ましい一実施形態では、前記キャパシタは、アルカリ金属イオンキャパシタであり、前記カチオンはアルカリ金属イオンを含み、前記第２電極活物質は、前記アルカリ金属イオンを可逆的に担持する材料を含む。少なくとも第１電極に上記電極を用いることで、耐久性に優れるアルカリ金属イオンキャパシタが得られる。 (5) In a preferred embodiment, the capacitor is an alkali metal ion capacitor, the cation includes an alkali metal ion, and the second electrode active material includes a material that reversibly supports the alkali metal ion. . By using the electrode for at least the first electrode, an alkali metal ion capacitor having excellent durability can be obtained.
　（６）本発明の他の一実施形態は、キャパシタの充放電方法であって、
　前記キャパシタは、第１電極活物質を含む第１電極、前記第１電極と反対の極性を有し、かつ第２電極活物質を含む第２電極、前記第１電極と前記第２電極との間に介在するセパレータ、ならびにアニオンおよびカチオンを含む電解質を含むアルカリ金属イオンキャパシタまたは電気二重層キャパシタであり、
　前記第１電極は、アルミニウムまたはアルミニウム合金を含む三次元網目状の第１電極集電体と、前記第１電極集電体に充填され、かつ前記第１電極活物質を含む第１電極合剤とを含み、
　前記第１電極活物質は、少なくとも前記アニオンを可逆的に担持する材料を含み、
　前記第１電極中の前記第１電極合剤の含有量は、３０～９０質量％であり、
　前記第１電極の密度は、０．３～１．１ｇ／ｃｍ3であり、
　上限電圧Ｖ1で充放電したときの容量Ｃ1に対する上限電圧Ｖ2で充放電したときの容量Ｃ2の比：Ｃ2／Ｃ1は、１．３以上であり、
　前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ1は３．８Ｖであり、前記上限電圧Ｖ2は４．２Ｖであり、
　前記電気二重層キャパシタにおいて、前記上限電圧Ｖ1は２．５Ｖであり、前記上限電圧Ｖ2は２．９Ｖであり、
　前記キャパシタを、前記上限電圧Ｖ2以上の上限電圧で充放電する工程を有する充放電方法に関する。
　このような実施形態によれば、例えば、電圧Ｖ2以上の高い上限電圧まで充電しても、充放電を、安定かつ可逆的に行うことができ、これによりキャパシタの耐久性を向上できる。 (6) Another embodiment of the present invention is a method for charging and discharging a capacitor,
The capacitor includes a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, and the first electrode and the second electrode. An alkali metal ion capacitor or an electric double layer capacitor comprising an intervening separator and an electrolyte containing an anion and a cation,
The first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
The first electrode active material includes at least a material that reversibly supports the anion,
The content of the first electrode mixture in the first electrode is 30 to 90% by mass,
The density of the first electrode is 0.3 to 1.1 g / cm 3 ,
Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
In the alkali metal ion capacitor, the upper limit voltage V 1 is 3.8V, the upper limit voltage V 2 is 4.2V,
In the electric double layer capacitor, the upper limit voltage V 1 is 2.5V, the upper limit voltage V 2 is 2.9V,
It said capacitor, to charge and discharge method having a step of charging and discharging at the upper limit voltage V 2 or more the upper limit voltage.
According to this embodiment, for example, it is charged to a voltage V 2 higher than the upper limit voltage, the charge and discharge, stable and can be carried out reversibly, thereby improving the durability of the capacitor.
［発明の実施形態の詳細］
　本発明の実施形態に係るキャパシタ、およびその充放電方法の具体例を、適宜図面を参照しつつ以下に説明する。なお、本発明はこれらの例示に限定されるものではなく、添付の特許請求の範囲によって示され、特許請求の範囲と均等の意味および範囲内での全ての変更が含まれることが意図される。 [Details of the embodiment of the invention]
Specific examples of capacitors according to embodiments of the present invention and charge / discharge methods thereof will be described below with reference to the drawings as appropriate. In addition, this invention is not limited to these illustrations, is shown by the attached claim, and is intended that all the changes within the meaning and range equivalent to the claim are included. .
（キャパシタおよびその充放電方法）
　以下、キャパシタの構成要素についてより詳細に説明する。
　本発明の一実施形態に係るキャパシタは、第１電極、第１電極と反対の極性を有する第２電極、第１電極と第２電極との間に介在するセパレータ、および電解質を含む。第１電極は、第１電極活物質を含み、第２電極は、第２電極活物質を含む。電解質はアニオンおよびカチオンを含む。このようなキャパシタにおいて、第１電極は、アルミニウムまたはアルミニウム合金を含む三次元網目状の第１電極集電体と、第１電極集電体に充填され、かつ第１電極活物質を含む第１電極合剤とを含む。 (Capacitor and charge / discharge method thereof)
Hereinafter, the components of the capacitor will be described in more detail.
A capacitor according to an embodiment of the present invention includes a first electrode, a second electrode having a polarity opposite to that of the first electrode, a separator interposed between the first electrode and the second electrode, and an electrolyte. The first electrode includes a first electrode active material, and the second electrode includes a second electrode active material. The electrolyte includes anions and cations. In such a capacitor, the first electrode includes a first electrode current collector having a three-dimensional network shape including aluminum or an aluminum alloy, and a first electrode material filled in the first electrode current collector and including a first electrode active material. An electrode mixture.
　（第１電極）
　（第１電極集電体）
　第１電極に含まれる第１電極集電体は、アルミニウムまたはアルミニウム合金を含む。
　第１電極集電体中のアルミニウムの含有量は、例えば、８０質量％以上、好ましくは９０質量％以上、さらに好ましくは９５質量％以上または９８質量％以上である。第１電極集電体中のアルミニウムの含有量は、１００質量％以下であり、９９．９質量％以下であってもよい。これらの下限値と上限値とは任意に組み合わせることができる。第１電極集電体中のアルミニウムの含有量は、例えば、８０～１００質量％、または９５～１００質量％であってもよい。第１電極集電体には、不可避的に混入する不純物が含まれていてもよい。 (First electrode)
(First electrode current collector)
The first electrode current collector included in the first electrode includes aluminum or an aluminum alloy.
The content of aluminum in the first electrode current collector is, for example, 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more or 98% by mass or more. The content of aluminum in the first electrode current collector is 100% by mass or less, and may be 99.9% by mass or less. These lower limit values and upper limit values can be arbitrarily combined. The content of aluminum in the first electrode current collector may be, for example, 80 to 100% by mass, or 95 to 100% by mass. The first electrode current collector may contain impurities inevitably mixed.
　第１電極集電体に含まれるアルミニウム合金としては、例えば、アルミニウム－鉄合金、アルミニウム－銅合金、アルミニウム－マンガン合金、アルミニウム－ケイ素合金、アルミニウム－マグネシウム合金、アルミニウム－マグネシウム－ケイ素合金、アルミニウム－亜鉛合金、アルミニウム－ニッケル合金などが挙げられる。 Examples of the aluminum alloy contained in the first electrode current collector include aluminum-iron alloy, aluminum-copper alloy, aluminum-manganese alloy, aluminum-silicon alloy, aluminum-magnesium alloy, aluminum-magnesium-silicon alloy, aluminum- Examples include zinc alloys and aluminum-nickel alloys.
　第１電極集電体は、アルミニウムまたはアルミニウム合金を含む三次元網目状の骨格を有する。三次元網目状の骨格とは、アルミニウムまたはアルミニウム合金で形成された繊維部（または棒状部）を有し、繊維部が三次元的に連結して網目状のネットワークを形成した骨格またはその構造であってもよい。つまり、第１電極集電体は、複数の繊維部（または棒状部）を含むことができ、これらの複数の繊維部は、三次元的に連結して三次元網目状の骨格を形成している。 The first electrode current collector has a three-dimensional network skeleton containing aluminum or an aluminum alloy. A three-dimensional network skeleton is a skeleton or structure having a fiber part (or rod-like part) formed of aluminum or an aluminum alloy, and the fiber parts are three-dimensionally connected to form a network network. There may be. That is, the first electrode current collector can include a plurality of fiber portions (or rod-shaped portions), and the plurality of fiber portions are three-dimensionally connected to form a three-dimensional network-like skeleton. Yes.
　三次元網目状の第１電極集電体は、連続空隙を有する樹脂製の多孔体（樹脂発泡体、樹脂製の不織布など）を、例えば、メッキ処理などにより、集電体を構成する金属（具体的には、アルミニウムおよび／またはアルミニウム合金）で被覆することにより形成できる。得られる第１電極集電体は、樹脂製発泡体の形状に対応して、１つ１つがセル状の空孔を多数有しており、これらのセル状の空孔が連通した連続空隙（つまり、連通孔）を有する。隣り合うセル状の空孔の間には、開口（または窓）が形成され、この開口により空孔が連通した状態となることが好ましい。 The three-dimensional mesh-shaped first electrode current collector is formed of a resin porous body (resin foam, resin nonwoven fabric, etc.) having continuous voids by, for example, a metal ( Specifically, it can be formed by coating with aluminum and / or an aluminum alloy. The obtained first electrode current collector has a large number of cell-like pores one by one corresponding to the shape of the resin foam, and a continuous void ( That is, it has a communication hole. It is preferable that an opening (or window) is formed between the adjacent cellular holes, and the holes communicate with each other.
　キャパシタを高容量化する観点から、第１電極集電体の気孔率は、例えば、３０～９９体積％、好ましくは５０～９８体積％、さらに好ましくは８０～９８体積％または９０～９８体積％である。三次元網目状の骨格における平均空孔径（連通するセル状の空孔の平均径）は、電極合剤の充填性および保持性の観点から、例えば、５０～１０００μｍ、好ましくは１００～９００μｍ、さらに好ましくは３５０～９００μｍである。なお、平均空孔径は、第１電極集電体（または第１電極）の厚みよりも小さいことが好ましい。 From the viewpoint of increasing the capacity of the capacitor, the porosity of the first electrode current collector is, for example, 30 to 99% by volume, preferably 50 to 98% by volume, more preferably 80 to 98% by volume, or 90 to 98% by volume. It is. The average pore diameter in the three-dimensional network skeleton (average diameter of cell-like pores communicating with each other) is, for example, from 50 to 1000 μm, preferably from 100 to 900 μm, from the viewpoint of filling and holding properties of the electrode mixture. The thickness is preferably 350 to 900 μm. The average pore diameter is preferably smaller than the thickness of the first electrode current collector (or the first electrode).
　好ましい実施形態では、第１電極集電体の三次元網目状の骨格は、内部に空洞を有する（つまり、中空である）。骨格内の空洞は、樹脂製の多孔体の除去により形成される。第１電極集電体の骨格内の空洞は、連通孔状であってもよく、このような骨格は、トンネル状またはチューブ状になっている。中空の骨格を有する第１電極集電体は、嵩高い三次元構造を有しながらも、極めて軽量である。骨格内部の空洞の幅は、平均値で、例えば、０．５～５μｍ、好ましくは１～４μｍまたは２～３μｍである。 In a preferred embodiment, the three-dimensional network skeleton of the first electrode current collector has a cavity inside (that is, is hollow). The cavity in the skeleton is formed by removing the porous resin body. The cavity in the skeleton of the first electrode current collector may have a communication hole shape, and such a skeleton has a tunnel shape or a tube shape. The first electrode current collector having a hollow skeleton is extremely lightweight while having a bulky three-dimensional structure. The average width of the cavity inside the skeleton is, for example, 0.5 to 5 μm, preferably 1 to 4 μm or 2 to 3 μm.
　第１電極は、第１電極集電体に第１電極合剤を充填した後、通常、乾燥され、集電体の厚み方向に圧縮（または圧延）することにより形成される。圧縮により、集電体の気孔率および平均空孔径は変化する。第１電極集電体の上記の気孔率および平均空孔径の範囲は、第１電極合剤を充填する前で、かつ圧延前の気孔率および平均空孔径のものである。 The first electrode is formed by filling the first electrode current collector with the first electrode mixture, and then usually drying and compressing (or rolling) the current collector in the thickness direction. The porosity and average pore diameter of the current collector change due to the compression. The ranges of the porosity and average pore diameter of the first electrode current collector are those of the porosity and average pore diameter before filling the first electrode mixture and before rolling.
　第１電極集電体は、気孔率が非常に高く、比表面積が大きい。つまり、空隙内の表面も含む集電体表面の広い面積に活物質を多く付着させることができる。また、多くの活物質を空隙内に充填しながらも、集電体と活物質との接触面積が大きく、気孔率も大きくすることができるので、活物質を有効利用できる。
　第１電極集電体の比表面積（ＢＥＴ比表面積）は、例えば、１００～７００ｃｍ2／ｇ、好ましくは１５０～６５０ｃｍ2／ｇ、さらに好ましくは２００～６００ｃｍ2／ｇである。 The first electrode current collector has a very high porosity and a large specific surface area. That is, a large amount of active material can be attached to a wide area of the current collector surface including the surface in the gap. In addition, since the contact area between the current collector and the active material can be increased and the porosity can be increased while filling a large amount of the active material in the gap, the active material can be effectively used.
The specific surface area of the first electrode collector (BET specific surface area) is, for example, 100 ~ 700cm 2 / g, preferably 150 ~ 650cm 2 / g, more preferably 200 ~ 600cm 2 / g.
　充放電の上限電圧が高い場合、電極合剤に含まれるバインダが劣化し易くなる。金属箔を電極集電体として用いる場合には、充放電時にバインダが劣化して、電極合剤が脱落したり、および／または電極合剤層が剥離したりし、その結果、高い容量を確保できなくなる。本発明の実施形態では、上記のような第１電極集電体を用いることで、充放電の上限電圧を、例えば、Ｖ2以上に高くすることで仮にバインダが劣化しても、第１電極集電体の骨格内に、第１電極合剤（特に、第１電極活物質）を保持した状態を維持することができるとともに、電解質を保持することができる。よって、充放電時の活物質および／または電極合剤の脱落による容量の低下を効果的に抑制でき、耐久性を向上できる。 When the upper limit voltage of charging / discharging is high, the binder contained in the electrode mixture is likely to deteriorate. When using a metal foil as an electrode current collector, the binder deteriorates during charging and discharging, and the electrode mixture falls off and / or the electrode mixture layer peels off. As a result, a high capacity is secured. become unable. In the embodiment of the present invention, by using the first electrode current collector as described above, even if the binder is deteriorated by increasing the upper limit voltage of charge / discharge to, for example, V 2 or more, the first electrode The state in which the first electrode mixture (particularly, the first electrode active material) is held in the skeleton of the current collector can be maintained, and the electrolyte can be held. Therefore, the capacity | capacitance fall by dropping of the active material and / or electrode mixture at the time of charging / discharging can be suppressed effectively, and durability can be improved.
　第１電極では、第１電極集電体の三次元ネットワークが張り巡らされているため、第１電極集電体の繊維部同士が近接し、繊維部と電極活物質粒子との距離が近い。よって、第１電極は、高い導電性を有する。また、第１電極内には、第１電極合剤を充填後も、ある程度の気孔率を確保できるため、電解質を電極活物質の近辺に十分に保持させることができる。このような第１電極を用いることでキャパシタの出力を高め易くなる。 In the first electrode, since the three-dimensional network of the first electrode current collector is stretched, the fiber parts of the first electrode current collector are close to each other, and the distance between the fiber part and the electrode active material particles is short. Therefore, the first electrode has high conductivity. Moreover, since a certain amount of porosity can be ensured even after the first electrode mixture is filled in the first electrode, the electrolyte can be sufficiently held in the vicinity of the electrode active material. By using such a first electrode, the output of the capacitor can be easily increased.
　第１電極の厚みは、例えば、１００～２０００μｍ、好ましくは１５０～１５００μｍ、さらに好ましくは１８０～１２００μｍである。高い容量が得られ易いことに加え、第１電極の厚みがこのような範囲である場合、電極活物質の保持力が高く、耐久性の向上に有利である。 The thickness of the first electrode is, for example, 100 to 2000 μm, preferably 150 to 1500 μm, and more preferably 180 to 1200 μm. In addition to being easy to obtain a high capacity, when the thickness of the first electrode is within such a range, the holding capacity of the electrode active material is high, which is advantageous for improving the durability.
　キャパシタとしては、アルミニウムまたはアルミニウム合金製の電極集電体を使用できるもの、例えば、リチウムイオンキャパシタ、ナトリウムイオンキャパシタなどのアルカリ金属イオンキャパシタ；ＥＤＬＣが挙げられる。
　アルカリ金属イオンキャパシタでは、第１電極は正極であり、ＥＤＬＣでは、第１電極は、正極および負極のいずれであってもよく、正極および負極の双方に使用してもよい。 Examples of the capacitor include those that can use an electrode current collector made of aluminum or an aluminum alloy, for example, alkali metal ion capacitors such as lithium ion capacitors and sodium ion capacitors; EDLCs.
In the alkali metal ion capacitor, the first electrode is a positive electrode, and in EDLC, the first electrode may be either a positive electrode or a negative electrode, or may be used for both the positive electrode and the negative electrode.
　（第１電極合剤）
　（第１電極活物質）
　第１電極集電体に充填される第１電極合剤は、第１電極活物質を含む。第１電極活物質は、少なくともアニオンを可逆的に担持（具体的には、吸着および脱離）する材料を含む。第１電極活物質は、キャパシタの種類および第１電極の極性に応じて、適宜選択できる。 (First electrode mixture)
(First electrode active material)
The first electrode mixture filled in the first electrode current collector includes a first electrode active material. The first electrode active material includes at least a material that reversibly supports (specifically, adsorbs and desorbs) anions. The first electrode active material can be appropriately selected according to the type of capacitor and the polarity of the first electrode.
　第１電極が正極である場合、第１電極活物質は、少なくともアニオンを吸着および脱離する材料を含む。第１電極活物質は、アニオンおよびカチオンを吸着および脱離する材料であってもよい。第１電極が負極である場合、第１電極活物質は、カチオンを吸着および脱離する材料を含む。これらの材料はいずれも、充放電の際に、非ファラデー反応を起こす材料である。第１電極は、正極であることが好ましい。 When the first electrode is a positive electrode, the first electrode active material includes at least a material that adsorbs and desorbs anions. The first electrode active material may be a material that adsorbs and desorbs anions and cations. When the first electrode is a negative electrode, the first electrode active material includes a material that adsorbs and desorbs cations. All of these materials are materials that cause a non-Faraday reaction during charging and discharging. The first electrode is preferably a positive electrode.
　第１電極活物質が少なくともアニオンを吸着および脱離する材料を含む場合、このような材料としては、活性炭、メソポーラスカーボン、マイクロポーラスカーボン、カーボンナノチューブなどの多孔質炭素材料（第１多孔質炭素材料とも言う）が例示できる。第１多孔質炭素材料は、賦活処理されたものであってもよく、賦活処理されていなくてもよい。これらの第１多孔質炭素材料は、一種を単独でまたは二種以上を組み合わせて使用できる。第１多孔質炭素材料のうち、活性炭および／またはマイクロポーラスカーボンが好ましい。 When the first electrode active material includes at least a material that adsorbs and desorbs anions, examples of such a material include porous carbon materials such as activated carbon, mesoporous carbon, microporous carbon, and carbon nanotube (first porous carbon material). Can also be exemplified. The first porous carbon material may be activated or may not be activated. These 1st porous carbon materials can be used individually by 1 type or in combination of 2 or more types. Of the first porous carbon materials, activated carbon and / or microporous carbon is preferred.
　正極活物質は、第１多孔質炭素材料に加え、必要に応じて、さらに他の活物質を含むことができる。正極活物質中の第１多孔質炭素材料の含有量は、５０質量％を超えることが好ましく、８０質量％以上または９０質量％以上であってもよい。正極活物質中の第１多孔質炭素材料の含有量は１００質量％以下である。特に、正極活物質中の活性炭およびマイクロポーラスカーボンの含有量がこのような範囲であることが好ましい。正極活物質が、第１多孔質炭素材料（特に、活性炭および／またはマイクロポーラスカーボン）のみを含む場合も好ましい。 The positive electrode active material can further contain other active materials as required in addition to the first porous carbon material. The content of the first porous carbon material in the positive electrode active material is preferably more than 50% by mass, and may be 80% by mass or more or 90% by mass or more. Content of the 1st porous carbon material in a positive electrode active material is 100 mass% or less. In particular, the content of activated carbon and microporous carbon in the positive electrode active material is preferably within such a range. It is also preferable that the positive electrode active material contains only the first porous carbon material (particularly activated carbon and / or microporous carbon).
　マイクロポーラスカーボンとしては、キャパシタに使用される公知のものが使用でき、例えば、塩素ガスを含む雰囲気中で、炭化珪素、炭化チタンなどの金属炭化物を加熱することにより得られるものを使用してもよい。 As the microporous carbon, known ones used for capacitors can be used, for example, those obtained by heating metal carbides such as silicon carbide and titanium carbide in an atmosphere containing chlorine gas. Good.
　活性炭としては、キャパシタに使用される公知のものが使用できる。活性炭の原料としては、例えば、木材；ヤシ殻；パルプ廃液；石炭またはその熱分解により得られる石炭系ピッチ；重質油またはその熱分解により得られる石油系ピッチ；フェノール樹脂などが挙げられる。炭化された材料は、その後、賦活するのが一般的である。賦活法としては、ガス賦活法および薬品賦活法が例示できる。 As the activated carbon, known ones used for capacitors can be used. Examples of the raw material of activated carbon include wood; coconut shells; pulp waste liquid; coal or coal-based pitch obtained by thermal decomposition thereof; heavy oil or petroleum-based pitch obtained by thermal decomposition thereof; phenol resin and the like. The carbonized material is generally then activated. Examples of the activation method include a gas activation method and a chemical activation method.
　活性炭の平均粒径（体積基準の粒度分布におけるメディアン径、以下同じ。）は、特に限定されないが、２０μｍ以下であることが好ましい。比表面積も特に限定されないが、８００～３０００ｍ2／ｇ程度が好ましい。比表面積がこのような範囲である場合、キャパシタの静電容量を大きくする上で有利であるとともに、内部抵抗を小さくすることができる。 The average particle diameter of the activated carbon (median diameter in the volume-based particle size distribution, the same shall apply hereinafter) is not particularly limited, but is preferably 20 μm or less. The specific surface area is not particularly limited, but is preferably about 800 to 3000 m 2 / g. When the specific surface area is in such a range, it is advantageous for increasing the capacitance of the capacitor, and the internal resistance can be reduced.
　第１電極は、例えば、第１集電体の骨格内に、第１電極活物質を含む第１電極合剤スラリーを充填し、その後、第１電極合剤スラリーに含まれる分散媒を除去し、さらに必要に応じて、第１電極活物質を保持した集電体を圧縮（または圧延）することにより得られる。
　分散媒としては、例えば、Ｎ－メチル－２－ピロリドン（ＮＭＰ：Ｎ－ｍｅｔｈｙｌ－２－ｐｙｒｒｏｌｉｄｏｎｅ）などの有機溶媒の他、水などが用いられる。 For example, the first electrode is filled with the first electrode mixture slurry containing the first electrode active material in the skeleton of the first current collector, and then the dispersion medium contained in the first electrode mixture slurry is removed. Further, it can be obtained by compressing (or rolling) the current collector holding the first electrode active material, if necessary.
As the dispersion medium, for example, water or the like is used in addition to an organic solvent such as N-methyl-2-pyrrolidone (NMP).
　第１電極合剤は、第１電極活物質の他に、導電助剤、および／またはバインダなどを含んでもよい。第１電極に使用される導電助剤の少なくとも一部を、第１電極集電体の表面に付着させて導電層を形成し、導電層を覆うように、第１電極合剤を第１電極集電体に担持させてもよい。 The first electrode mixture may contain a conductive additive and / or a binder in addition to the first electrode active material. At least part of the conductive additive used for the first electrode is attached to the surface of the first electrode current collector to form a conductive layer, and the first electrode mixture is applied to the first electrode so as to cover the conductive layer. It may be carried on a current collector.
　導電助剤としては、アセチレンブラック、ケッチェンブラックなどのカーボンブラック；黒鉛（鱗片状黒鉛、土状黒鉛などの天然黒鉛；人造黒鉛など）；酸化ルテニウムなどの導電性化合物；炭素繊維、金属繊維などの導電性繊維などが例示できる。 Examples of conductive assistants include carbon blacks such as acetylene black and ketjen black; graphite (natural graphite such as flake graphite and earth graphite; artificial graphite and the like); conductive compounds such as ruthenium oxide; carbon fibers and metal fibers, etc. Examples of the conductive fibers can be exemplified.
　導電助剤の量は、第１電極活物質１００質量部に対して、例えば１～２０質量部、好ましくは２～１０質量部である。導電助剤の量がこのような範囲である場合、電極合剤の導電性を確保しながらも、電極密度を高め易い。本発明の実施形態では、三次元網目状の第１電極集電体を用いるため、導電助剤の量が少なくても、第１電極において高い導電性を確保し易い。例えば、導電助剤の量は、第１電極活物質１００質量部に対して、５質量部以下（例えば、０～５質量部）、または３質量部以下（例えば、０．１～３質量部）とすることもできる。 The amount of the conductive assistant is, for example, 1 to 20 parts by mass, preferably 2 to 10 parts by mass with respect to 100 parts by mass of the first electrode active material. When the amount of the conductive auxiliary is in such a range, it is easy to increase the electrode density while ensuring the conductivity of the electrode mixture. In the embodiment of the present invention, since the first electrode current collector having a three-dimensional network shape is used, it is easy to ensure high conductivity in the first electrode even if the amount of the conductive auxiliary agent is small. For example, the amount of the conductive assistant is 5 parts by mass or less (for example, 0 to 5 parts by mass) or 3 parts by mass or less (for example, 0.1 to 3 parts by mass) with respect to 100 parts by mass of the first electrode active material. ).
　バインダの種類は特に制限されず、例えば、ポリフッ化ビニリデン（ＰＶＤＦ：ｐｏｌｙｖｉｎｙｌｉｄｅｎｅ　ｆｌｕｏｒｉｄｅ）、ポリテトラフルオロエチレンなどのフッ素樹脂；ポリビニルクロリドなどの塩素含有ビニル樹脂；ポリオレフィン樹脂；スチレンブタジエンゴムなどのゴム状重合体；ポリビニルピロリドン、ポリビニルアルコール；セルロース誘導体［カルボキシメチルセルロースなどのセルロースエーテル（カルボキシアルキルセルロースなど）など］などを用いることができる。 The type of the binder is not particularly limited. For example, a fluorine resin such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene; a chlorine-containing vinyl resin such as polyvinyl chloride; a polyolefin resin; or a rubbery heavy material such as styrene butadiene rubber. Polyvinyl pyrrolidone, polyvinyl alcohol; cellulose derivatives [cellulose ethers such as carboxymethyl cellulose (carboxyalkyl cellulose and the like)] and the like can be used.
　バインダの量は、特に制限されず、第１電極活物質１００質量部あたり、例えば、０．５～１５質量部程度の範囲から選択でき、好ましくは１～１２質量部、さらに好ましくは３～１０質量部であってもよい。本発明の実施形態では、三次元網目状の第１電極集電体を用いるため、バインダの量が少なくても、多くの第１電極合剤を集電体に保持させることができる。バインダの量は、第１電極活物質１００質量部に対して、５質量部以下（例えば、１～５質量部）とすることができ、２～４質量部であってもよい。 The amount of the binder is not particularly limited, and can be selected from the range of, for example, about 0.5 to 15 parts by mass, preferably 1 to 12 parts by mass, more preferably 3 to 10 parts per 100 parts by mass of the first electrode active material. A mass part may be sufficient. In the embodiment of the present invention, since the first electrode current collector having a three-dimensional network shape is used, a large amount of the first electrode mixture can be held on the current collector even if the amount of the binder is small. The amount of the binder can be 5 parts by mass or less (for example, 1 to 5 parts by mass) with respect to 100 parts by mass of the first electrode active material, and may be 2 to 4 parts by mass.
　本発明の実施形態では、第１電極の密度を、０．３～１．１ｇ／ｃｍ3の範囲に制御する。第１電極の密度をこのような範囲とすることで、充放電の上限電圧を、電圧Ｖ2以上に高くしても、容量の低下を抑制して充放電を安定に行うことができ、充放電による容量の低下を抑制できるため、キャパシタの耐久性を向上できる。第１電極の密度をこのような範囲に制御することで、耐久性が向上する理由は定かではないが、現象論として、このような範囲に第１電極の密度を制御することで、上記の効果が実際に得られることが確認されている。第１電極の密度が適正であることで、三次元網目状の第１電極集電体との高い密着性を維持し易いため、耐久性が向上すると推測される。 In the embodiment of the present invention, the density of the first electrode is controlled in the range of 0.3 to 1.1 g / cm 3 . By setting the density of the first electrode in such a range, even if the upper limit voltage of charging / discharging is increased to the voltage V 2 or higher, it is possible to stably perform charging / discharging while suppressing a decrease in capacity. Since the decrease in capacity due to discharge can be suppressed, the durability of the capacitor can be improved. The reason why the durability is improved by controlling the density of the first electrode in such a range is not clear, but as a phenomenological theory, by controlling the density of the first electrode in such a range, It has been confirmed that the effect is actually obtained. Since the density of the first electrode is appropriate, it is easy to maintain high adhesion with the three-dimensional network-shaped first electrode current collector, and it is estimated that durability is improved.
　第１電極の密度は、０．３ｇ／ｃｍ3以上、好ましくは０．４ｇ／ｃｍ3以上、さらに好ましくは０．５ｇ／ｃｍ3以上である。第１電極の密度は、１．１ｇ／ｃｍ3以下であり、好ましくは１ｇ／ｃｍ3以下であり、さらに好ましくは０．８ｇ／ｃｍ3以下である。これらの下限値と上限値とは任意に組み合わせることができる。第１電極の密度は、例えば、０．４～１．１ｇ／ｃｍ3、０．５～１．１ｇ／ｃｍ3、または０．５～１ｇ／ｃｍ3であってもよい。 The density of the first electrode is 0.3 g / cm 3 or more, preferably 0.4 g / cm 3 or more, more preferably 0.5 g / cm 3 or more. The density of the first electrode is 1.1 g / cm 3 or less, preferably 1 g / cm 3 or less, and more preferably 0.8 g / cm 3 or less. These lower limit values and upper limit values can be arbitrarily combined. The density of the first electrode may be, for example, 0.4 to 1.1 g / cm 3 , 0.5 to 1.1 g / cm 3 , or 0.5 to 1 g / cm 3 .
　本発明の実施形態では、上記のような第１電極集電体を用いるとともに、第１電極の密度を上記の範囲に制御することで、充放電の上限電圧を高めても安定して充放電を行うことができ、高い容量を得ることができる。具体的には、キャパシタを、上限電圧Ｖ1で充放電したときの容量Ｃ1に対する上限電圧Ｖ2で充放電したときの容量Ｃ2の比：Ｃ2／Ｃ1は、１．３以上であり、好ましくは１．４以上である。ここで、アルカリ金属イオンキャパシタでは、上限電圧Ｖ1は３．８Ｖであり、上限電圧Ｖ2は４．２Ｖである。ＥＤＬＣでは、上限電圧Ｖ1は２．５Ｖであり、上限電圧Ｖ2は２．９Ｖである。電圧Ｖ1は、各キャパシタにおける一般的な（または従来の）上限電圧であり、電圧Ｖ2は、電圧Ｖ1よりも０．４Ｖ高い電圧である。 In the embodiment of the present invention, the first electrode current collector as described above is used, and the density of the first electrode is controlled within the above range, thereby stably charging / discharging even if the upper limit voltage of charging / discharging is increased. And a high capacity can be obtained. Specifically, the ratio of the capacity C 2 when the capacitor is charged / discharged at the upper limit voltage V 2 to the capacity C 1 when the capacitor is charged / discharged at the upper limit voltage V 1 : C 2 / C 1 is 1.3 or more. Yes, preferably 1.4 or more. Here, in the alkali metal ion capacitor, the upper limit voltage V 1 is 3.8V, and the upper limit voltage V 2 is 4.2V. In EDLC, the upper limit voltage V 1 is 2.5V, and the upper limit voltage V 2 is 2.9V. The voltage V 1 is a general (or conventional) upper limit voltage in each capacitor, and the voltage V 2 is 0.4 V higher than the voltage V 1 .
　容量Ｃ1に対する上限電圧Ｖ3でキャパシタを充放電したときの容量Ｃ3の比：Ｃ3／Ｃ1は、例えば、１．６以上であり、好ましくは１．７以上、さらに好ましくは１．７５以上である。上限電圧Ｖ3は、アルカリ金属イオンキャパシタでは、４．５Ｖであり、ＥＤＬＣでは、３．２Ｖである。電圧Ｖ3は、電圧Ｖ1よりも０．７Ｖ高い電圧である。 The ratio of the capacity C 3 when the capacitor is charged / discharged with the upper limit voltage V 3 with respect to the capacity C 1 : C 3 / C 1 is, for example, 1.6 or more, preferably 1.7 or more, more preferably 1. 75 or more. The upper limit voltage V 3 is 4.5 V for the alkali metal ion capacitor and 3.2 V for EDLC. The voltage V 3 is a voltage higher by 0.7V than the voltage V 1 .
　このように、Ｃ2／Ｃ1比および／またはＣ3／Ｃ1比が高い値を示すことは、キャパシタを、一般的な上限電圧よりも０．４Ｖ以上または０．７Ｖ以上高い上限電圧まで充電しても、安定に充放電を行うことができ、充放電による容量の低下を抑制できることを意味している。 Thus, the high value of the C 2 / C 1 ratio and / or the C 3 / C 1 ratio indicates that the capacitor is increased by 0.4 V or more or 0.7 V or more higher than the general upper limit voltage. This means that charging and discharging can be performed stably even when charging, and a decrease in capacity due to charging and discharging can be suppressed.
　なお、第１電極の密度は、電極合剤の含有量によって若干変化する。そのため、第１電極中の第１電極合剤の含有量が３０～９０質量％である場合に、第１電極の密度が上記の範囲を満たせばよい。第１電極中の第１電極合剤の含有量は、好ましくは４０～８５質量％、さらに好ましくは５０～８３質量％である。 Note that the density of the first electrode varies slightly depending on the content of the electrode mixture. Therefore, when the content of the first electrode mixture in the first electrode is 30 to 90% by mass, the density of the first electrode only needs to satisfy the above range. The content of the first electrode mixture in the first electrode is preferably 40 to 85% by mass, more preferably 50 to 83% by mass.
　（セパレータ）
　キャパシタに含まれるセパレータは、キャパシタの種類に応じて適宜選択できる。
　セパレータは、イオン透過性を有し、第１電極と第２電極との間に介在して、これらを物理的に離間させて短絡を防止する。セパレータは、多孔質構造を有し、細孔内に電解質を保持することで、イオンを透過させる。セパレータの材質としては、例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン；ポリエチレンテレフタレートなどのポリエステル；ポリアミド；ポリイミド；セルロース；ガラス繊維などを用いることができる。
　セパレータの平均孔径は特に制限されず、例えば、０．０１～５μｍ程度である。セパレータの厚みは特に制限されず、例えば、１０～１００μｍ程度である。 (Separator)
The separator included in the capacitor can be appropriately selected according to the type of the capacitor.
The separator has ion permeability and is interposed between the first electrode and the second electrode, and physically separates them to prevent a short circuit. The separator has a porous structure and allows ions to pass through by holding an electrolyte in the pores. As a material of the separator, for example, polyolefin such as polyethylene and polypropylene; polyester such as polyethylene terephthalate; polyamide; polyimide; cellulose; glass fiber and the like can be used.
The average pore diameter of the separator is not particularly limited and is, for example, about 0.01 to 5 μm. The thickness of the separator is not particularly limited, and is about 10 to 100 μm, for example.
　以下に、アルカリ金属イオンキャパシタおよびＥＤＬＣの各キャパシタについて、第１電極以外のキャパシタの構成をより詳細に説明する。
（アルカリ金属イオンキャパシタ）
　（第２電極）
　アルカリ金属イオンキャパシタでは、第１電極は正極であり、第２電極は負極である。
　第２電極である負極は、第２電極活物質（つまり、負極活物質）を含む。第２電極は、第２電極活物質を保持する第２電極集電体（つまり、負極集電体）を含むことができる。
　負極集電体は、金属箔でもよいが、キャパシタを高容量化する観点からは、金属多孔体であることが好ましい。金属多孔体としては、第１電極集電体であるアルミニウム多孔体と同様の三次元網目状の骨格（特に、中空の骨格）を有する金属多孔体が好ましい。金属多孔体の気孔率、平均空孔径、骨格内部の空洞の幅、比表面積などは、正極集電体の金属多孔体について例示した範囲から適宜選択できる。 Hereinafter, the configurations of capacitors other than the first electrode will be described in more detail with respect to each of the alkali metal ion capacitor and the EDLC capacitor.
(Alkali metal ion capacitor)
(Second electrode)
In the alkali metal ion capacitor, the first electrode is a positive electrode and the second electrode is a negative electrode.
The negative electrode that is the second electrode includes a second electrode active material (that is, a negative electrode active material). The second electrode can include a second electrode current collector (that is, a negative electrode current collector) that holds the second electrode active material.
The negative electrode current collector may be a metal foil, but is preferably a metal porous body from the viewpoint of increasing the capacity of the capacitor. As the metal porous body, a metal porous body having a three-dimensional network skeleton (particularly, a hollow skeleton) similar to the aluminum porous body as the first electrode current collector is preferable. The porosity, average pore diameter, void width inside the skeleton, specific surface area and the like of the metal porous body can be appropriately selected from the ranges exemplified for the metal porous body of the positive electrode current collector.
　負極集電体の材質としては、銅、銅合金、ニッケル、ニッケル合金、ステンレス鋼等が好ましい。負極集電体は、樹脂多孔体を金属被覆する際に、アルミニウムまたはアルミニウム合金に代えて、これらの材質を用い、第１電極集電体の場合に準じて作製することができる。 The material for the negative electrode current collector is preferably copper, copper alloy, nickel, nickel alloy, stainless steel, or the like. The negative electrode current collector can be produced according to the case of the first electrode current collector using these materials instead of aluminum or aluminum alloy when the resin porous body is metal-coated.
　負極活物質は、アルカリ金属イオンを可逆的に担持（もしくは、吸蔵および放出、または挿入および脱離）する材料を含む。このような材料としては、充放電の際にファラデー反応を起こす材料、例えば、アルカリ金属イオンを吸蔵および放出（または挿入および脱離）する炭素材料（第３炭素材料とも言う）の他、アルカリ金属チタン酸化物［例えば、リチウムチタン酸化物（チタン酸リチウムなどのスピネル型リチウムチタン酸化物など）、ナトリウムチタン酸化物（チタン酸ナトリウムなど）］、ケイ素酸化物、ケイ素合金、錫酸化物、錫合金が挙げられる。第３炭素材料としては、易黒鉛化性炭素（ソフトカーボン）、難黒鉛化性炭素（ハードカーボン）、黒鉛型結晶構造を有する炭素質材料などが例示できる。負極活物質は、一種を単独で用いてもよく、二種以上を組み合わせて用いてもよい。負極活物質は、理論容量が３００ｍＡｈ／ｇ以上であるものが好ましい。負極活物質のうち、第３炭素材料が好ましく、特に、黒鉛型結晶構造を有する炭素質材料（以下、第４炭素材料とも言う）、および／またはハードカーボンが好ましい。 The negative electrode active material includes a material that reversibly supports (or occludes and releases, or inserts and desorbs) alkali metal ions. Examples of such materials include materials that cause a Faraday reaction during charge and discharge, such as carbon materials that occlude and release (or insert and desorb) alkali metal ions (also referred to as third carbon materials), and alkali metals. Titanium oxide [eg, lithium titanium oxide (such as spinel type lithium titanium oxide such as lithium titanate), sodium titanium oxide (such as sodium titanate)], silicon oxide, silicon alloy, tin oxide, tin alloy Is mentioned. Examples of the third carbon material include graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), and a carbonaceous material having a graphite type crystal structure. A negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type. The negative electrode active material preferably has a theoretical capacity of 300 mAh / g or more. Of the negative electrode active material, a third carbon material is preferable, and a carbonaceous material having a graphite-type crystal structure (hereinafter also referred to as a fourth carbon material) and / or hard carbon is particularly preferable.
　黒鉛型結晶構造とは、層状の結晶構造を意味し、立方晶型結晶構造、菱面体晶型結晶構造などが例示できる。第４炭素材料としては、例えば、天然黒鉛（鱗片状黒鉛など）、人造黒鉛、黒鉛化メソカーボン小球体などが例示できる。これらの第４炭素材料は、一種を単独でまたは二種以上組み合わせて使用できる。 The graphite-type crystal structure means a layered crystal structure, and examples thereof include a cubic crystal structure and a rhombohedral crystal structure. Examples of the fourth carbon material include natural graphite (eg, scaly graphite), artificial graphite, and graphitized mesocarbon microspheres. These 4th carbon materials can be used individually by 1 type or in combination of 2 or more types.
　第４炭素材料を含む負極活物質を用いる場合、アルカリ金属イオンキャパシタ内では、充電時には、第４炭素材料の黒鉛型結晶構造の層間にアルカリ金属イオンが挿入され、放電時には、黒鉛型結晶構造の層間からアルカリ金属イオンが放出される。
　第４炭素材料における黒鉛型結晶構造の発達の程度の指標の１つとして、第４炭素材料のＸ線回折スペクトルで測定される（００２）面の平均面間隔ｄ002が使用されている。
第４炭素材料は、平均面間隔ｄ002が、０．３３７ｎｍ未満であることが好ましい。平均面間隔ｄ002の下限は特に制限されないが、平均面間隔ｄ002を、例えば、０．３３５以上とすることができる。平均面間隔ｄ002がこのような範囲の第４炭素材料を用いることで、充電時には、黒鉛型結晶構造内にアルカリ金属イオンをより効率よく挿入することができるとともに、放電時には、黒鉛型結晶構造からアルカリ金属イオンをスムーズに放出することができる。 In the case of using a negative electrode active material containing a fourth carbon material, in the alkali metal ion capacitor, alkali metal ions are inserted between layers of the graphite type crystal structure of the fourth carbon material during charging, and during discharge, the graphite type crystal structure has Alkali metal ions are released from the interlayer.
As an index of the degree of development of the graphite-type crystal structure in the fourth carbon material, an average interplanar spacing d002 of the (002) plane measured by the X-ray diffraction spectrum of the fourth carbon material is used.
The fourth carbon material, the average spacing d 002 is preferably less than 0.337 nm. The lower limit of the average spacing d 002 is not particularly limited, the average spacing d 002, for example, be 0.335 or more. By using the fourth carbon material having an average interplanar spacing d 002 in such a range, alkali metal ions can be more efficiently inserted into the graphite-type crystal structure at the time of charging, and the graphite-type crystal structure at the time of discharging. Alkali metal ions can be released smoothly from
　ハードカーボンは、炭素網面が層状に重なりあった黒鉛型結晶構造を有する黒鉛とは異なり、炭素網面が三次元的にずれた状態で重なりあった乱層構造を有する。ハードカーボンは、高温（例えば、３０００℃）での加熱処理によっても、乱層構造から黒鉛構造への転換が起こらず、黒鉛結晶子の発達が見られない。そのため、ハードカーボンは、難黒鉛化性炭素（ｎｏｎ－ｇｒａｐｈｉｔｉｚａｂｌｅ　ｃａｒｂｏｎ）とも称される。 Hard carbon, unlike graphite having a graphite-type crystal structure in which carbon network surfaces overlap in a layered manner, has a turbostratic structure in which the carbon network surfaces overlap in a three-dimensionally shifted state. Hard carbon does not change from a turbulent structure to a graphite structure even by heat treatment at a high temperature (for example, 3000 ° C.), and the development of graphite crystallites is not observed. Therefore, hard carbon is also referred to as non-graphitizable carbon.
　黒鉛に分類される第４炭素材料の平均面間隔ｄ002は上記のように０．３３７ｎｍ未満と小さいが、乱層構造を有するハードカーボンの平均面間隔ｄ002は大きく、例えば、０．３７ｎｍ以上である。ハードカーボンの平均面間隔ｄ002の上限は特に制限されないが、平均面間隔ｄ002を、例えば、０．４２ｎｍ以下とすることができる。ハードカーボンの平均面間隔ｄ002は、例えば、０．３７～０．４２ｎｍ、好ましくは０．３８～０．４ｎｍであってもよい。 The average spacing d 002 of the fourth carbon material is classified into graphite is as small as less than 0.337nm, as described above, large average spacing d 002 of the hard carbon having a turbostratic structure, for example, more than 0.37nm It is. The upper limit of the average spacing d 002 of the hard carbon is not particularly limited, the average spacing d 002, for instance, can be less than or equal to 0.42 nm. Mean spacing d 002 of the hard carbon, for example, 0.37 ~ 0.42 nm, preferably be a 0.38 ~ 0.4 nm.
　ハードカーボンにアルカリ金属イオンが担持される場合、アルカリ金属イオンは、ハードカーボンにわずかに含まれる黒鉛型結晶構造の層間に挿入されること、乱層構造内（具体的には、黒鉛型結晶構造の層間以外の部分）に入り込むこと、および／またはハードカーボンに吸着されることにより、ハードカーボンに担持（または吸蔵）されると考えられる。 When alkali metal ions are supported on the hard carbon, the alkali metal ions are inserted between the layers of the graphite-type crystal structure that is slightly contained in the hard carbon, inside the turbostratic structure (specifically, the graphite-type crystal structure It is considered that the carbon is supported (or occluded) by the hard carbon by entering and / or being adsorbed by the hard carbon.
　ハードカーボンは、乱層構造を有し、ハードカーボン中の黒鉛型結晶構造の比率は小さい。そのため、アルカリ金属イオンの多くは、黒鉛型結晶構造の層間以外の部分（例えば、乱層構造内に形成される空隙など）に挿入されること、および／またはハードカーボンに吸着されることで、ハードカーボンに吸蔵されると考えられる。よって、ハードカーボン（特に、平均面間隔ｄ002が上記のような範囲であるハードカーボン）を用いる場合には、充放電時の体積変化が小さくなり、充放電を繰り返しても劣化を抑制し易い。 Hard carbon has a turbulent structure, and the ratio of the graphite-type crystal structure in the hard carbon is small. Therefore, most of the alkali metal ions are inserted into portions other than the interlayer of the graphite-type crystal structure (for example, voids formed in the turbulent layer structure) and / or adsorbed to hard carbon, It is thought that it is occluded by hard carbon. Therefore, when using hard carbon (particularly, hard carbon having an average interplanar spacing d 002 in the above range), the volume change during charge / discharge is small, and deterioration is easy to suppress even after repeated charge / discharge. .
　ハードカーボンの構造については、様々なモデルが提案されているが、乱層構造内には、炭素網面が三次元的にずれて重なり合うことで、上記のように空隙が形成されていると考えられている。そのため、炭素網面が層状に密に積層した状態の結晶構造を有する黒鉛に比べて、ハードカーボンは平均比重が低い。黒鉛の平均比重は２．１～２．２５ｇ／ｃｍ3程度であるが、ハードカーボンの平均比重は、例えば、１．７ｇ／ｃｍ3以下であり、好ましくは１．４～１．７ｇ／ｃｍ3または１．５～１．７ｇ／ｃｍ3である。ハードカーボンがこのような平均比重を有する場合、充放電時のアルカリ金属イオンの吸蔵および放出に伴う体積変化をさらに低減し易くなり、活物質の劣化をより効果的に抑制することができる。 Various models have been proposed for the structure of hard carbon, but it is thought that voids are formed in the turbulent structure as described above, because the carbon network surfaces are three-dimensionally shifted and overlapped. It has been. Therefore, hard carbon has a lower average specific gravity than graphite having a crystal structure in which the carbon network surface is densely stacked in a layered manner. The average specific gravity of graphite is about 2.1 to 2.25 g / cm 3 , but the average specific gravity of hard carbon is, for example, 1.7 g / cm 3 or less, preferably 1.4 to 1.7 g / cm 3. 3 or 1.5 to 1.7 g / cm 3 . When hard carbon has such an average specific gravity, it becomes easier to reduce the volume change accompanying the occlusion and discharge | release of the alkali metal ion at the time of charging / discharging, and deterioration of an active material can be suppressed more effectively.
　ハードカーボンは、例えば、原料を、固相で炭素化することで得られる炭素質材料を包含する。固相で炭素化が起こる原料は、固形の有機物であり、具体的には、糖類、樹脂（フェノール樹脂などの熱硬化性樹脂；ポリ塩化ビニリデンなどの熱可塑性樹脂など）などが挙げられる。糖類には、糖鎖が比較的短い糖類（単糖類またはオリゴ糖類、例えば、砂糖など）の他、セルロース類などの多糖類［例えば、セルロースまたはその誘導体（セルロースエステル、セルロースエーテルなど）；木材、果実殻（ヤシ殻など）などのセルロースを含む材料など］などが挙げられる。これらの原料は、一種を単独でまたは二種以上を組み合わせて使用できる。ハードカーボンは、上記原料を、固相で加熱して炭素化することにより得られる。炭素化は、例えば、５００～１６００℃程度の温度で行うことができ、第１温度（例えば、５００℃以上８００℃未満の温度）での加熱と、第１温度よりも高い第２温度（例えば、８００～１６００℃の温度）での加熱とを適宜組み合わせてもよい。ガラス状カーボンもハードカーボンに含まれる。ハードカーボンは、一種を単独でまたは二種以上を組み合わせてもよい。 Hard carbon includes, for example, a carbonaceous material obtained by carbonizing a raw material in a solid phase. The raw material that undergoes carbonization in the solid phase is a solid organic substance, and specifically includes sugars, resins (thermosetting resins such as phenol resins; thermoplastic resins such as polyvinylidene chloride) and the like. Examples of the saccharide include saccharides having relatively short sugar chains (monosaccharides or oligosaccharides such as sugar), and polysaccharides such as cellulose [eg cellulose or derivatives thereof (cellulose ester, cellulose ether, etc.); wood, Materials containing cellulose, such as fruit shells (coconut shells, etc.)] and the like. These raw materials can be used individually by 1 type or in combination of 2 or more types. Hard carbon is obtained by heating and carbonizing the above raw material in a solid phase. Carbonization can be performed at a temperature of about 500 to 1600 ° C., for example, and heating at a first temperature (for example, a temperature of 500 ° C. or more and less than 800 ° C.) and a second temperature higher than the first temperature (for example, , A temperature of 800 to 1600 ° C.) may be appropriately combined. Glassy carbon is also included in hard carbon. Hard carbon may be used alone or in combination of two or more.
　負極活物質は、ハードカーボンおよび第４炭素材料以外の活物質を含むことができる。
アルカリ金属イオンの吸蔵および放出を効率よく行う観点からは、負極活物質中のハードカーボンおよび／または第４炭素材料の含有量は、８０質量％以上（具体的には８０～１００質量％）であることが好ましく、９０質量％以上（具体的には９０～１００質量％）であることがさらに好ましい。負極活物質をハードカーボンおよび／または第４炭素材料のみで構成してもよい。 The negative electrode active material can include an active material other than hard carbon and the fourth carbon material.
From the viewpoint of efficiently occluding and releasing alkali metal ions, the content of hard carbon and / or fourth carbon material in the negative electrode active material is 80% by mass or more (specifically, 80 to 100% by mass). It is preferably 90% by mass or more (specifically, 90 to 100% by mass). The negative electrode active material may be composed of only hard carbon and / or fourth carbon material.
　負極は、第１電極の場合に準じて、負極集電体に負極合剤（具体的には負極合剤スラリー）を塗布または充填し、乾燥し、必要に応じて、乾燥物を圧縮（または圧延）することにより得られる。また、負極としては、負極集電体の表面に、蒸着、スパッタリングなどの気相法で負極活物質の堆積膜を形成することにより得られるものを用いてもよい。第１電極の場合と同様に、負極に使用される導電助剤の少なくとも一部を、負極集電体の表面に付着させて導電層を形成し、導電層を覆うように、負極合剤または負極活物質を負極集電体に担持させてもよい。 According to the case of the first electrode, the negative electrode is coated or filled with a negative electrode mixture (specifically, a negative electrode mixture slurry) on the negative electrode current collector, dried, and if necessary, the dried product is compressed (or Obtained by rolling). Moreover, as a negative electrode, you may use what is obtained by forming the deposit film of a negative electrode active material on the surface of a negative electrode collector by vapor phase methods, such as vapor deposition and sputtering. As in the case of the first electrode, at least part of the conductive additive used for the negative electrode is attached to the surface of the negative electrode current collector to form a conductive layer, and the negative electrode mixture or The negative electrode active material may be supported on the negative electrode current collector.
　負極活物質には、アルカリ金属イオンをプレドープしてもよい。アルカリ金属イオンをプレドープすることで、負極電位が十分に低下した状態となり、これにより、キャパシタの電圧が高くなるため、アルカリ金属イオンキャパシタを高容量化することができる。なお、アルカリ金属イオンは、電解質に含まれるアルカリ金属イオンと同じである。 The negative electrode active material may be pre-doped with alkali metal ions. By pre-doping with alkali metal ions, the negative electrode potential is sufficiently lowered, thereby increasing the voltage of the capacitor, so that the capacity of the alkali metal ion capacitor can be increased. The alkali metal ion is the same as the alkali metal ion contained in the electrolyte.
　負極容量Ｃnと正極容量Ｃpとの比：Ｃn／Ｃp比は、例えば、１．１より大きく、好ましくは１．２または１．３以上、さらに好ましくは２以上または３以上である。Ｃn／Ｃp比は、例えば、１２．５未満であり、好ましくは１０以下、さらに好ましくは９以下である。これらの下限値と上限値とは適宜選択して組み合わせることができる。Ｃn／Ｃp比は、例えば、１．２～１０、または３～１０であってもよい。 Ratio of negative electrode capacity C n to positive electrode capacity C p : C n / C p ratio is, for example, larger than 1.1, preferably 1.2 or 1.3 or more, more preferably 2 or more or 3 or more. . The C n / C p ratio is, for example, less than 12.5, preferably 10 or less, more preferably 9 or less. These lower limit value and upper limit value can be appropriately selected and combined. The C n / C p ratio may be, for example, 1.2 to 10, or 3 to 10.
　Ｃn／Ｃp比が上記のような範囲である場合、負極に十分な量のアルカリ金属イオンをプレドープすることができ、より効果的にキャパシタを高電圧化することができる。また、初期電圧を高め易く、これにより、キャパシタを高容量化し易くなるため有利である。さらに、正極または負極の体積を必要以上に大きくする必要がないため、高い放電容量を確保しながらも、キャパシタの容量密度の低下を抑制し易い。 When the C n / C p ratio is in the above range, a sufficient amount of alkali metal ions can be pre-doped on the negative electrode, and the voltage of the capacitor can be increased more effectively. Further, it is easy to increase the initial voltage, which is advantageous because it makes it easy to increase the capacity of the capacitor. Furthermore, since it is not necessary to increase the volume of the positive electrode or the negative electrode more than necessary, it is easy to suppress a decrease in the capacitance density of the capacitor while ensuring a high discharge capacity.
　ここで、正極容量Ｃpとは、正極に含まれる正極活物質量から計算される蓄電可能な電荷量の理論値から不可逆容量を差し引いた値である。また、負極容量Ｃnとは、負極に含まれる負極活物質量から計算される蓄電可能な電荷量の理論値から不可逆容量を差し引いた値である。なお、ＣpおよびＣnは、それぞれ、正極を用いたＥＤＬＣ、および負極とアルカリ金属を用いたハーフセルについて測定される放電容量に基づいて評価することができる。 Here, the positive electrode capacity C p is a value obtained by subtracting the irreversible capacity from the theoretical value of the chargeable charge amount calculated from the amount of the positive electrode active material contained in the positive electrode. The negative electrode capacity C n is a value obtained by subtracting the irreversible capacity from the theoretical value of the chargeable charge amount calculated from the amount of the negative electrode active material contained in the negative electrode. C p and C n can be evaluated based on the discharge capacity measured for EDLC using the positive electrode and the half cell using the negative electrode and alkali metal, respectively.
　負極合剤スラリーは、負極活物質および分散媒の他に、バインダおよび／または導電助剤などを含んでもよい。分散媒、バインダとしては、第１電極の第１電極合剤について例示したものから適宜選択できる。負極活物質１００質量部に対するバインダの量は、前述の第１電極活物質１００質量部に対するバインダの量の範囲から適宜選択できる。 The negative electrode mixture slurry may contain a binder and / or a conductive aid in addition to the negative electrode active material and the dispersion medium. As a dispersion medium and a binder, it can select suitably from what was illustrated about the 1st electrode mixture of the 1st electrode. The amount of the binder with respect to 100 parts by mass of the negative electrode active material can be appropriately selected from the range of the amount of the binder with respect to 100 parts by mass of the first electrode active material.
　導電助剤としては、特に制限されず、アセチレンブラック、ケッチェンブラックなどのカーボンブラック；酸化ルテニウムなどの導電性化合物；炭素繊維、金属繊維などの導電性繊維などが例示できる。負極活物質１００質量部に対する導電助剤の量は、前述の第１電極活物質１００質量部に対する導電助剤の量の範囲から適宜選択できる。 The conductive assistant is not particularly limited, and examples thereof include carbon black such as acetylene black and ketjen black; conductive compound such as ruthenium oxide; conductive fiber such as carbon fiber and metal fiber. The amount of the conductive additive relative to 100 parts by mass of the negative electrode active material can be appropriately selected from the range of the amount of the conductive auxiliary relative to 100 parts by mass of the first electrode active material.
　負極の厚みは、例えば、５０～２０００μｍの範囲から適宜選択できる。負極集電体として三次元網目状の金属多孔体を用いる場合、負極の厚みは、例えば、１００～２０００μｍ、好ましくは１００～１５００μｍ、または１００～１２００μｍである。 The thickness of the negative electrode can be appropriately selected from the range of 50 to 2000 μm, for example. When a three-dimensional network metal porous body is used as the negative electrode current collector, the thickness of the negative electrode is, for example, 100 to 2000 μm, preferably 100 to 1500 μm, or 100 to 1200 μm.
　（電解質）
　アルカリ金属イオンキャパシタの電解質は、アルカリ金属イオン伝導性を有する非水電解質であることが好ましい。このような非水電解質は、アルカリ金属イオンを含むカチオンとアニオンとを含む。非水電解質としては、例えば、非水溶媒（または有機溶媒）にアルカリ金属イオンとアニオンとの塩（アルカリ金属塩）を溶解させた電解質（有機電解質）の他、アルカリ金属イオンおよびアニオンを含むイオン液体などが用いられる。 (Electrolytes)
The electrolyte of the alkali metal ion capacitor is preferably a non-aqueous electrolyte having alkali metal ion conductivity. Such a non-aqueous electrolyte contains a cation containing an alkali metal ion and an anion. Nonaqueous electrolytes include, for example, electrolytes (organic electrolytes) in which a salt of an alkali metal ion and an anion (alkali metal salt) is dissolved in a nonaqueous solvent (or an organic solvent), as well as ions containing an alkali metal ion and an anion. Liquid or the like is used.
　有機電解質は、非水溶媒（有機溶媒）およびアルカリ金属塩に加え、イオン液体および／または添加剤などを含むことができるが、電解質中の非水溶媒およびアルカリ金属塩の含有量の合計は、例えば、６０質量％以上、好ましくは７５質量％以上、さらに好ましくは８５質量％以上である。電解質中の非水溶媒およびアルカリ金属塩の含有量の合計は、例えば、１００質量％以下、または９５質量％以下であってもよい。これらの下限値と上限値とは任意に組み合わせることができる。電解質中の非水溶媒およびアルカリ金属塩の含有量の合計は、例えば、６０～１００質量％、または７５～９５質量％であってもよい。 The organic electrolyte can contain an ionic liquid and / or an additive in addition to the nonaqueous solvent (organic solvent) and the alkali metal salt, but the total content of the nonaqueous solvent and the alkali metal salt in the electrolyte is: For example, it is 60% by mass or more, preferably 75% by mass or more, and more preferably 85% by mass or more. The total content of the nonaqueous solvent and the alkali metal salt in the electrolyte may be, for example, 100% by mass or less, or 95% by mass or less. These lower limit values and upper limit values can be arbitrarily combined. The total content of the nonaqueous solvent and the alkali metal salt in the electrolyte may be, for example, 60 to 100% by mass, or 75 to 95% by mass.
　本明細書中、「イオン液体」とは、溶融状態の塩（溶融塩）と同義であり、アニオンとカチオンとで構成される液状イオン性物質である。
　電解質にイオン液体を用いる場合、電解質は、アルカリ金属イオンおよびアニオンを含むイオン液体に加え、非水溶媒および／または添加剤などを含むことができるが、電解質中のアルカリ金属イオンおよびアニオンを含むイオン液体の含有量は、６０質量％以上であることが好ましく、７０質量％以上であることがさらに好ましい。電解質中のアルカリ金属イオンおよびアニオンを含むイオン液体の含有量は、８０質量％以上、または９０質量％以上であってもよい。電解質中のイオン液体の含有量は、１００質量％以下である。 In the present specification, the “ionic liquid” is synonymous with a molten salt (molten salt) and is a liquid ionic substance composed of an anion and a cation.
When an ionic liquid is used for the electrolyte, the electrolyte can contain a nonaqueous solvent and / or an additive in addition to the ionic liquid containing alkali metal ions and anions, but the ions containing alkali metal ions and anions in the electrolyte The content of the liquid is preferably 60% by mass or more, and more preferably 70% by mass or more. The content of the ionic liquid containing alkali metal ions and anions in the electrolyte may be 80% by mass or more, or 90% by mass or more. The content of the ionic liquid in the electrolyte is 100% by mass or less.
　低温特性などの観点からは、非水溶媒（有機溶媒）を含む電解質を用いることが好ましい。電解質の分解をできるだけ抑制する観点からは、イオン液体を含む電解質を用いることが好ましく、イオン液体および非水溶媒を含む電解質を用いてもよい。 From the viewpoint of low temperature characteristics, it is preferable to use an electrolyte containing a non-aqueous solvent (organic solvent). From the viewpoint of suppressing the decomposition of the electrolyte as much as possible, an electrolyte containing an ionic liquid is preferably used, and an electrolyte containing an ionic liquid and a nonaqueous solvent may be used.
　電解質におけるアルカリ金属塩またはアルカリ金属イオンの濃度は、例えば、０．３～５ｍｏｌ／Ｌの範囲から適宜選択できる。
　アルカリ金属イオンとしては、例えば、リチウムイオン、ナトリウムイオン、カリウムイオン、ルビジウムイオン、およびセシウムイオンからなる群より選択される少なくとも一種が挙げられる。これらのうち、リチウムイオンおよびナトリウムイオンからなる群より選択される少なくとも一種が好ましい。これらのアルカリ金属イオンを用いることで、アルカリ金属イオンを、充電時にはスムーズに負極活物質に吸蔵させることができるとともに、放電時には負極活物質から放出させることができる。 The concentration of the alkali metal salt or alkali metal ion in the electrolyte can be appropriately selected from the range of 0.3 to 5 mol / L, for example.
Examples of the alkali metal ion include at least one selected from the group consisting of lithium ion, sodium ion, potassium ion, rubidium ion, and cesium ion. Of these, at least one selected from the group consisting of lithium ions and sodium ions is preferred. By using these alkali metal ions, the alkali metal ions can be smoothly occluded in the negative electrode active material during charging, and can be released from the negative electrode active material during discharge.
　リチウムイオン伝導性を有する電解質を用いるアルカリ金属イオンキャパシタは、リチウムイオンキャパシタとも称される。また、ナトリウムイオン伝導性を有する電解質を用いるアルカリ金属イオンキャパシタは、ナトリウムイオンキャパシタとも称される。 An alkali metal ion capacitor using an electrolyte having lithium ion conductivity is also referred to as a lithium ion capacitor. An alkali metal ion capacitor using an electrolyte having sodium ion conductivity is also referred to as a sodium ion capacitor.
　アルカリ金属塩を構成するアニオン（第１アニオン）の種類は特に限定されず、例えば、フッ素含有酸のアニオン［ヘキサフルオロリン酸イオン（ＰＦ6 -）などのフッ素含有リン酸のアニオン；テトラフルオロホウ酸イオン（ＢＦ4 -）などのフッ素含有ホウ酸のアニオンなど］、塩素含有酸のアニオン［過塩素酸イオン（ＣｌＯ4 -）など］、オキサレート基を有する酸素酸のアニオン［ビス（オキサラト）ボレートイオン（Ｂ（Ｃ2Ｏ4）2 -）などのオキサラトボレートイオン；トリス（オキサラト）ホスフェートイオン（Ｐ（Ｃ2Ｏ4）3 -）などのオキサラトボレートイオンなど］、フルオロアルカンスルホン酸のアニオン［トリフルオロメタンスルホン酸イオン（ＣＦ3ＳＯ3 -）など］、ビススルホニルアミドアニオンなどが挙げられる。
　アルカリ金属塩は、一種を単独で用いてもよく、第１アニオンの種類が異なるアルカリ金属塩を二種以上組み合わせて用いてもよい。 The kind of the anion (first anion) constituting the alkali metal salt is not particularly limited. For example, an anion of a fluorine-containing acid [anion of fluorine-containing phosphate such as hexafluorophosphate ion (PF 6 − ); Anion of fluorine-containing boric acid such as acid ion (BF 4 − )], anion of chlorine-containing acid [perchlorate ion (ClO 4 − ), etc.], anion of oxyacid having an oxalate group [bis (oxalato) borate Ions (Oxalatoborate ions such as B (C 2 O 4 ) 2 − ); Oxalatoborate ions such as tris (oxalato) phosphate ions (P (C 2 O 4 ) 3 − )], fluoroalkanesulfonic acid anion [trifluoromethanesulfonate ion (CF 3 SO 3 -), etc.], the levator like bissulfonylamide anion It is.
One alkali metal salt may be used alone, or two or more alkali metal salts having different types of first anions may be used in combination.
　上記のビススルホニルアミドアニオンとしては、例えば、ビス（フルオロスルホニル）アミドアニオン［ビス（フルオロスルホニル）アミドアニオン（Ｎ（ＳＯ2Ｆ）2 -）など］、（フルオロスルホニル）（パーフルオロアルキルスルホニル）アミドアニオン［（フルオロスルホニル）（トリフルオロメチルスルホニル）アミドアニオン（（ＦＳＯ2）（ＣＦ3ＳＯ2）Ｎ-）など］、ビス（パーフルオロアルキルスルホニル）アミドアニオン［ビス（トリフルオロメチルスルホニル）アミドアニオン（Ｎ（ＳＯ2ＣＦ3）2 -）、ビス（ペンタフルオロエチルスルホニル）アミドアニオン（Ｎ（ＳＯ2Ｃ2Ｆ5）2 -）など］などが挙げられる。パーフルオロアルキル基の炭素数は、好ましくは１～８、さらに好ましくは１、２、または３である。 Examples of the bissulfonylamide anion include bis (fluorosulfonyl) amide anion [bis (fluorosulfonyl) amide anion (N (SO 2 F) 2 − ) and the like], (fluorosulfonyl) (perfluoroalkylsulfonyl) amide Anion [(fluorosulfonyl) (trifluoromethylsulfonyl) amide anion ((FSO 2 ) (CF 3 SO 2 ) N −, etc.)], bis (perfluoroalkylsulfonyl) amide anion [bis (trifluoromethylsulfonyl) amide anion (N (SO 2 CF 3 ) 2 − ), bis (pentafluoroethylsulfonyl) amide anion (N (SO 2 C 2 F 5 ) 2 − ) and the like]. The carbon number of the perfluoroalkyl group is preferably 1-8, more preferably 1, 2, or 3.
　ビススルホニルアミドアニオンのうち、ビス（フルオロスルホニル）アミドアニオン（ＦＳＡ-：ｂｉｓ（ｆｌｕｏｒｏｓｕｌｆｏｎｙｌ）ａｍｉｄｅ　ａｎｉｏｎ））；ビス（トリフルオロメチルスルホニル）アミドアニオン（ＴＦＳＡ-：ｂｉｓ（ｔｒｉｆｌｕｏｒｏｍｅｔｈｙｌｓｕｌｆｏｎｙｌ）ａｍｉｄｅ　ａｎｉｏｎ）、ビス（ペンタフルオロエチルスルホニル）アミドアニオン、（フルオロスルホニル）（トリフルオロメチルスルホニル）アミドアニオンなどのビス（パーフルオロアルキルスルホニル）アミドアニオン（ＰＦＳＡ-：ｂｉｓ（ｐｅｒｆｌｕｏｒｏａｌｋｙｌｓｕｌｆｏｎｙｌ）ａｍｉｄｅ　ａｎｉｏｎ）などが好ましい。 Among bissulfonylamide anions, bis (fluorosulfonyl) amide anion (FSA − : bis (fluorosulfonyl) amide anion)); bis (trifluoromethylsulfonyl) amide anion (TFSA − : bis (trifluoromethylsulfonyl) amide anion), bis ( A bis (perfluoroalkylsulfonyl) amide anion (PFSA − : bis (perfluoroalkylsulfonyl) amide anion) such as a pentafluoroethylsulfonyl) amide anion and a (fluorosulfonyl) (trifluoromethylsulfonyl) amide anion is preferred.
　電解質に含まれる非水溶媒は、特に限定されず、アルカリ金属イオンキャパシタに使用される公知の非水溶媒が使用できる。非水溶媒は、イオン伝導度の観点から、例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネートなどの環状カーボネート；ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネートなどの鎖状カーボネート；γ－ブチロラクトンなどの環状炭酸エステルなどを好ましく用いることができる。非水溶媒は、一種を単独で用いてもよく、二種以上を組み合わせて用いてもよい。 The non-aqueous solvent contained in the electrolyte is not particularly limited, and known non-aqueous solvents used for alkali metal ion capacitors can be used. Non-aqueous solvents include, for example, cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate; cyclic carbonates such as γ-butyrolactone. Etc. can be preferably used. A non-aqueous solvent may be used individually by 1 type, and may be used in combination of 2 or more type.
　アルカリ金属イオンを含むイオン液体は、アルカリ金属イオンと、アニオン（第２アニオン）とを含む。第２アニオンとしては、第１アニオンについて例示した各種アニオン、具体的には、ビススルホニルアミドアニオン、フッ素含有酸のアニオン、塩素含有酸のアニオン、オキサレート基を有する酸素酸のアニオン、フルオロアルカンスルホン酸のアニオンなどが使用できる。第２アニオンは、一種を単独でまたは二種以上を組み合わせて使用できる。第２アニオンは、少なくともビススルホニルアミドアニオンを含むことが好ましい。第２アニオン中のビススルホニルアミドアニオンの含有量は、例えば、８０～１００ｍｏｌ％であり、好ましくは９０～１００ｍｏｌ％である。 The ionic liquid containing alkali metal ions contains alkali metal ions and anions (second anions). As the second anion, various anions exemplified for the first anion, specifically, a bissulfonylamide anion, an anion of a fluorine-containing acid, an anion of a chlorine-containing acid, an anion of an oxyacid having an oxalate group, a fluoroalkanesulfonic acid Can be used. A 2nd anion can be used individually by 1 type or in combination of 2 or more types. The second anion preferably contains at least a bissulfonylamide anion. The content of the bissulfonylamide anion in the second anion is, for example, 80 to 100 mol%, preferably 90 to 100 mol%.
　イオン液体（またはイオン液体に含まれるカチオン）は、アルカリ金属イオン（第１カチオン）に加え、さらに第２カチオンを含んでいてもよい。このような第２カチオンとしては、アルカリ金属イオン以外の無機カチオン、例えば、マグネシウムイオン、カルシウムイオン、アンモニウムカチオンなどを使用してもよいが、有機カチオンが好ましい。第２カチオンは、一種を単独でまたは二種以上を組み合わせて使用できる。 The ionic liquid (or cation contained in the ionic liquid) may further contain a second cation in addition to the alkali metal ion (first cation). As such second cations, inorganic cations other than alkali metal ions such as magnesium ions, calcium ions and ammonium cations may be used, but organic cations are preferred. A 2nd cation can be used individually by 1 type or in combination of 2 or more types.
　第２カチオンとして使用される有機カチオンとしては、脂肪族アミン、脂環族アミンまたは芳香族アミンに由来するカチオン（例えば、第４級アンモニウムカチオンなど）の他、窒素含有へテロ環を有するカチオン（つまり、環状アミンに由来するカチオン）などの窒素含有オニウムカチオン；イオウ含有オニウムカチオン；リン含有オニウムカチオンなどが例示できる。 Examples of the organic cation used as the second cation include a cation derived from an aliphatic amine, an alicyclic amine, or an aromatic amine (for example, a quaternary ammonium cation), and a cation having a nitrogen-containing heterocycle ( That is, examples include nitrogen-containing onium cations such as cations derived from cyclic amines; sulfur-containing onium cations; and phosphorus-containing onium cations.
　窒素含有有機オニウムカチオンのうち、特に、第４級アンモニウムカチオンの他、窒素含有ヘテロ環骨格として、ピロリジン、ピリジン、またはイミダゾールを有するものが好ましい。
　第４級アンモニウムカチオンとしては、テトラメチルアンモニウムカチオン、テトラエチルアンモニウムカチオン（ＴＥＡ+：ｔｅｔｒａｅｔｈｙｌａｍｍｏｎｉｕｍ　ｃａｔｉｏｎ）、エチルトリメチルアンモニウムカチオン、ヘキシルトリメチルアンモニウムカチオン、メチルトリエチルアンモニウムカチオン（ＴＥＭＡ+：ｍｅｔｈｙｌｔｒｉｅｔｈｙｌａｍｍｏｎｉｕｍ　ｃａｔｉｏｎ）などのテトラアルキルアンモニウムカチオンなどが例示できる。 Of the nitrogen-containing organic onium cations, those having pyrrolidine, pyridine, or imidazole as the nitrogen-containing heterocyclic skeleton in addition to the quaternary ammonium cation are particularly preferable.
Examples of the quaternary ammonium cation include tetraalkylammonium cation, tetraethylammonium cation (TEA + : tetraethylammonium cation), ethyltrimethylammonium cation, hexyltrimethylammonium cation, and methyltriethylammonium cation (TEMA + : methyltriethylammonium cation). A cation etc. can be illustrated.
　ピロリジン骨格を有する有機オニウムカチオンは、ピロリジン環を構成する１つの窒素原子に、２つのアルキル基を有するものが好ましい。このような有機オニウムカチオンとしては、例えば、１，１－ジメチルピロリジニウムカチオン、１，１－ジエチルピロリジニウムカチオン、１－エチル－１－メチルピロリジニウムカチオン、１－メチル－１－プロピルピロリジニウムカチオン（ＭＰＰＹ+：１－ｍｅｔｈｙｌ－１－ｐｒｏｐｙｌｐｙｒｒｏｌｉｄｉｎｉｕｍ　ｃａｔｉｏｎ）、１－ブチル－１－メチルピロリジニウムカチオン（ＭＢＰＹ+：１－ｂｕｔｙｌ－１－ｍｅｔｈｙｌｐｙｒｒｏｌｉｄｉｎｉｕｍ　ｃａｔｉｏｎ）、１－エチル－１－プロピルピロリジニウムカチオンなどが挙げられる。 The organic onium cation having a pyrrolidine skeleton preferably has two alkyl groups on one nitrogen atom constituting the pyrrolidine ring. Examples of such organic onium cations include 1,1-dimethylpyrrolidinium cation, 1,1-diethylpyrrolidinium cation, 1-ethyl-1-methylpyrrolidinium cation, and 1-methyl-1-propyl. Pyrrolidinium cation (MPPY + : 1-methyl-1-pyrrolidinium cation), 1-butyl-1-methylpyrrolidinium cation (MBPY + : 1-butyl-1-methylpyrrolidinium cation), 1-ethyl-1-propyl Examples include pyrrolidinium cation.
　ピリジン骨格を有する有機オニウムカチオンは、ピリジン環を構成する１つの窒素原子に、１つのアルキル基を有することが好ましい。このような有機オニウムカチオンとしては、１－メチルピリジニウムカチオン、１－エチルピリジニウムカチオン、１－プロピルピリジニウムカチオンなどの１－アルキルピリジニウムカチオンが挙げられる。 The organic onium cation having a pyridine skeleton preferably has one alkyl group on one nitrogen atom constituting the pyridine ring. Examples of such organic onium cations include 1-alkylpyridinium cations such as 1-methylpyridinium cation, 1-ethylpyridinium cation, and 1-propylpyridinium cation.
　イミダゾール骨格を有する有機オニウムカチオンは、イミダゾール環を構成する２つの窒素原子に、それぞれ、１つのアルキル基を有することが好ましい。このような有機オニウムカチオンとしては、例えば、１，３－ジメチルイミダゾリウムカチオン、１－エチル－３－メチルイミダゾリウムカチオン（ＥＭＩ+：　１－ｅｔｈｙｌ－３－ｍｅｔｈｙｌｉｍｉｄａｚｏｌｉｕｍ　ｃａｔｉｏｎ）、１－メチル－３－プロピルイミダゾリウムカチオン、１－ブチル－３－メチルイミダゾリウムカチオン（ＢＭＩ+：１－ｂｕｔｈｙｌ－３－ｍｅｔｈｙｌｉｍｉｄａｚｏｌｉｕｍ　ｃａｔｉｏｎ）、１－エチル－３－プロピルイミダゾリウムカチオン、１－ブチル－３－エチルイミダゾリウムカチオンなどが挙げられる。これらのうち、ＥＭＩ+、ＢＭＩ+などのメチル基と炭素数２～４のアルキル基とを有するイミダゾリウムカチオンが好ましい。 The organic onium cation having an imidazole skeleton preferably has one alkyl group on each of two nitrogen atoms constituting the imidazole ring. Examples of such organic onium cations include 1,3-dimethylimidazolium cation, 1-ethyl-3-methylimidazolium cation (EMI + : 1-ethyl-3-methylimidazolium cation), 1-methyl-3- Propylimidazolium cation, 1-butyl-3-methylimidazolium cation (BMI + : 1-butyl-3-methylimidazolium cation), 1-ethyl-3-propylimidazolium cation, 1-butyl-3-ethylimidazolium cation Etc. Of these, imidazolium cations having a methyl group and an alkyl group having 2 to 4 carbon atoms such as EMI + and BMI + are preferable.
　（ＥＤＬＣ）
　（第２電極）
　ＥＤＬＣでは、第１電極は正極であり、第２電極は負極である。ただし、第２電極として、第１電極と同じものを使用してもよい。第２電極は、第２電極活物質を含む。第２電極は、第２電極活物質を保持する第２電極集電体を含むことができる。 (EDLC)
(Second electrode)
In EDLC, the first electrode is a positive electrode and the second electrode is a negative electrode. However, the same electrode as the first electrode may be used as the second electrode. The second electrode includes a second electrode active material. The second electrode can include a second electrode current collector that holds the second electrode active material.
　第２電極活物質は、カチオンを可逆的に担持（具体的には、吸着および脱離）する材料、つまり、非ファラデー反応を起こす材料を含む。第２電極活物質としては、第１電極活物質について例示したものが使用できる。第１電極活物質と第２電極活物質とは同じであってもよく、異なるものであってもよい。 The second electrode active material includes a material that reversibly carries cations (specifically, adsorption and desorption), that is, a material that causes a non-Faraday reaction. As the second electrode active material, those exemplified for the first electrode active material can be used. The first electrode active material and the second electrode active material may be the same or different.
　第２電極集電体は、金属箔でもよいが、キャパシタを高容量化する観点からは、金属多孔体であることが好ましい。金属多孔体は、第１電極集電体であるアルミニウム多孔体と同様の三次元網目状の骨格（特に、中空の骨格）を有していてもよい。 The second electrode current collector may be a metal foil, but is preferably a metal porous body from the viewpoint of increasing the capacity of the capacitor. The metal porous body may have a three-dimensional network skeleton (particularly, a hollow skeleton) similar to the aluminum porous body that is the first electrode current collector.
　第２電極が負極である場合、第２電極集電体の材質は、第１電極集電体について例示したアルミニウムまたはアルミニウム合金であってもよく、アルカリ金属イオンキャパシタの負極集電体について例示した材質であってもよい。第２電極集電体は、第１電極集電体またはアルカリ金属イオンキャパシタの負極集電体と同様にして作製することができる。
　第２電極は、第１電極と同様にして作製することができる。第２電極に含まれる電極活物質以外の成分および量などについても、第１電極について例示したものおよび範囲からそれぞれ適宜選択できる。 When the second electrode is a negative electrode, the material of the second electrode current collector may be aluminum or aluminum alloy exemplified for the first electrode current collector, and exemplified for the negative electrode current collector of the alkali metal ion capacitor. It may be a material. The second electrode current collector can be produced in the same manner as the first electrode current collector or the negative electrode current collector of the alkali metal ion capacitor.
The second electrode can be produced in the same manner as the first electrode. Components and amounts other than the electrode active material contained in the second electrode can be appropriately selected from those exemplified for the first electrode and ranges.
　（電解質）
　ＥＤＬＣに使用される電解質は、水を含んでもよく、または非水電解質でもよい。電解質は、有機カチオンを含むカチオンとアニオンとを含む。電解質としては、有機カチオンとアニオン（第３アニオン）との塩を非水溶媒（または有機溶媒）に溶解させた電解質の他、有機カチオンおよびアニオン（第４アニオン）を含むイオン液体などの非水電解質が好ましく用いられる。カチオンは、有機カチオン以外のカチオン、例えば、前記例示のアルカリ金属カチオン、および／または前記例示の無機カチオンなどを含んでもよい。
　電解質における有機カチオンの濃度は、例えば、０．３～５ｍｏｌ／Ｌの範囲から適宜選択できる。 (Electrolytes)
The electrolyte used for EDLC may contain water or may be a non-aqueous electrolyte. The electrolyte includes a cation including an organic cation and an anion. As the electrolyte, in addition to an electrolyte in which a salt of an organic cation and an anion (third anion) is dissolved in a non-aqueous solvent (or organic solvent), non-aqueous such as an ionic liquid containing an organic cation and an anion (fourth anion) An electrolyte is preferably used. The cation may include a cation other than the organic cation, such as the alkali metal cation exemplified above and / or the inorganic cation exemplified above.
The concentration of the organic cation in the electrolyte can be appropriately selected from the range of 0.3 to 5 mol / L, for example.
　有機カチオンとしては、アルカリ金属イオンキャパシタの第２カチオンとして例示した有機カチオンと同様のものが例示できる。第３アニオンとしては、アルカリ金属イオンキャパシタの第１アニオンとして例示したものから適宜選択できる。非水溶媒としては、アルカリ金属イオンキャパシタについて例示したものから適宜選択できる。 Examples of the organic cation include those similar to the organic cation exemplified as the second cation of the alkali metal ion capacitor. The third anion can be appropriately selected from those exemplified as the first anion of the alkali metal ion capacitor. As a nonaqueous solvent, it can select suitably from what was illustrated about the alkali metal ion capacitor.
　イオン液体に含まれる第４アニオンとしては、アルカリ金属イオンキャパシタの第２アニオンとして例示したものから適宜選択できる。第４アニオンは、少なくともビススルホニルアミドアニオンを含むことが好ましい。第４アニオン中のビススルホニルアミドアニオンの含有量は、第２アニオンの場合と同様の範囲から選択できる。
　電解質中のイオン液体の含有量は、アルカリ金属イオンキャパシタについて例示した範囲から適宜選択できる。アルカリ金属イオンキャパシタの場合と同様に、電解質の分解を抑制する観点からは、イオン液体を含む電解質を用いることが好ましく、イオン液体および有機溶媒を含む電解質を用いてもよい。 The fourth anion contained in the ionic liquid can be appropriately selected from those exemplified as the second anion of the alkali metal ion capacitor. The fourth anion preferably includes at least a bissulfonylamide anion. The content of the bissulfonylamide anion in the fourth anion can be selected from the same range as in the case of the second anion.
Content of the ionic liquid in electrolyte can be suitably selected from the range illustrated about the alkali metal ion capacitor. As in the case of the alkali metal ion capacitor, from the viewpoint of suppressing the decomposition of the electrolyte, an electrolyte containing an ionic liquid is preferably used, and an electrolyte containing an ionic liquid and an organic solvent may be used.
　本発明の実施形態に係るキャパシタは、例えば、（ａ）第１電極と、第２電極と、第１電極および第２電極の間に介在するセパレータとで電極群を形成する工程、ならびに（ｂ）電極群および電解質をセルケース内に収容する工程を経ることにより製造できる。 The capacitor according to the embodiment of the present invention includes, for example, (a) a step of forming an electrode group with a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode, and (b ) The electrode group and the electrolyte can be manufactured through a step of housing in the cell case.
　図１は、本発明の一実施形態に係るキャパシタを概略的に示す縦断面図である。キャパシタは、積層型の電極群、電解質（図示せず）およびこれらを収容する角型のアルミニウム製のセルケース１０を具備する。セルケース１０は、上部が開口した有底の容器本体１２と、上部開口を塞ぐ蓋体１３とで構成されている。 FIG. 1 is a longitudinal sectional view schematically showing a capacitor according to an embodiment of the present invention. The capacitor includes a stacked electrode group, an electrolyte (not shown), and a rectangular aluminum cell case 10 for housing them. The cell case 10 includes a bottomed container body 12 having an upper opening and a lid 13 that closes the upper opening.
　キャパシタを組み立てる際には、まず、第１電極２と第２電極３とをこれらの間にセパレータ１を介在させた状態で積層することにより電極群が構成され、構成された電極群がセルケース１０の容器本体１２に挿入される。その後、容器本体１２に電解質を注液し、電極群を構成するセパレータ１、第１電極２および第２電極３の空隙に電解質を含浸させる工程が行われる。あるいは、電解質が、イオン液体を含む場合、電解質に電極群を含浸し、その後、電解質を含んだ状態の電極群を容器本体１２に収容してもよい。 When assembling a capacitor, first, an electrode group is formed by laminating the first electrode 2 and the second electrode 3 with the separator 1 interposed therebetween, and the configured electrode group is a cell case. 10 container bodies 12 are inserted. Thereafter, a step of injecting an electrolyte into the container main body 12 and impregnating the electrolyte in the gaps of the separator 1, the first electrode 2, and the second electrode 3 constituting the electrode group is performed. Alternatively, when the electrolyte includes an ionic liquid, the electrode group may be impregnated in the electrolyte, and then the electrode group including the electrolyte may be accommodated in the container body 12.
　蓋体１３の中央には、セルケース１０の内圧が上昇したときに内部で発生したガスを放出するための安全弁１６が設けられている。安全弁１６を中央にして、蓋体１３の一方側寄りには、蓋体１３を貫通する外部正極端子１４が設けられ、蓋体１３の他方側寄りの位置には、蓋体１３を貫通する外部負極端子が設けられる。 In the center of the lid 13, a safety valve 16 is provided for releasing gas generated inside when the internal pressure of the cell case 10 rises. An external positive terminal 14 that penetrates the lid 13 is provided near the one side of the lid 13 with the safety valve 16 in the center, and an external that penetrates the lid 13 is located near the other side of the lid 13. A negative terminal is provided.
　積層型の電極群は、いずれも矩形のシート状である、複数の第１電極２と複数の第２電極３およびこれらの間に介在する複数のセパレータ１により構成されている。図１では、セパレータ１は、第１電極２を包囲するように袋状に形成されているが、セパレータの形態は特に限定されない。複数の第１電極２と複数の第２電極３は、電極群内で積層方向に交互に配置される。 The stacked electrode group is composed of a plurality of first electrodes 2, a plurality of second electrodes 3, and a plurality of separators 1 interposed between them, each having a rectangular sheet shape. In FIG. 1, the separator 1 is formed in a bag shape so as to surround the first electrode 2, but the form of the separator is not particularly limited. The plurality of first electrodes 2 and the plurality of second electrodes 3 are alternately arranged in the stacking direction within the electrode group.
　各第１電極２の一端部には、電極リード片２ａを形成してもよい。複数の第１電極２の電極リード片２ａを束ねるとともに、セルケース１０の蓋体１３に設けられた外部電極端子１４に接続することにより、複数の第１電極２が並列に接続される。同様に、各第２電極３の一端部には、電極リード片３ａを形成してもよい。複数の第２電極３の電極リード片３ａを束ねるとともに、セルケース１０の蓋体１３に設けられた外部電極端子に接続することにより、複数の第２電極３が並列に接続される。電極リード片２ａの束と電極リード片３ａの束は、互いの接触を避けるように、電極群の一端面の左右に、間隔を空けて配置することが望ましい。 An electrode lead piece 2 a may be formed at one end of each first electrode 2. The plurality of first electrodes 2 are connected in parallel by bundling the electrode lead pieces 2 a of the plurality of first electrodes 2 and connecting them to the external electrode terminals 14 provided on the lid 13 of the cell case 10. Similarly, an electrode lead piece 3 a may be formed at one end of each second electrode 3. The plurality of second electrodes 3 are connected in parallel by bundling the electrode lead pieces 3 a of the plurality of second electrodes 3 and connecting them to external electrode terminals provided on the lid 13 of the cell case 10. It is desirable that the bundle of electrode lead pieces 2a and the bundle of electrode lead pieces 3a are arranged on the left and right sides of one end face of the electrode group with a space so as to avoid mutual contact.
　外部電極端子１４は、柱状であり、少なくとも外部に露出する部分が螺子溝を有する。各端子の螺子溝にはナット７が嵌められ、ナット７を回転することにより蓋体１３に対してナット７が固定される。各端子のセルケース１０内部に収容される部分には、鍔部８が設けられており、ナット７の回転により、鍔部８が、蓋体１３の内面に、ワッシャ９を介して固定される。 The external electrode terminal 14 has a columnar shape, and at least a portion exposed to the outside has a screw groove. A nut 7 is fitted in the screw groove of each terminal, and the nut 7 is fixed to the lid 13 by rotating the nut 7. A flange 8 is provided in a portion of each terminal accommodated in the cell case 10, and the flange 8 is fixed to the inner surface of the lid 13 via a washer 9 by the rotation of the nut 7. .
　電極群は、積層タイプに限らず、第１電極と第２電極とをセパレータを介して捲回することにより形成したものであってもよい。リチウムイオンキャパシタなどのアルカリ金属イオンキャパシタでは、負極にアルカリ金属が析出するのを防止する観点から、正極よりも負極の寸法を大きくしてもよい。 The electrode group is not limited to the laminated type, and may be formed by winding the first electrode and the second electrode through a separator. In an alkali metal ion capacitor such as a lithium ion capacitor, the dimension of the negative electrode may be larger than that of the positive electrode from the viewpoint of preventing alkali metal from being deposited on the negative electrode.
　本発明の実施形態に係るキャパシタは、上記のような構成により、充放電の上限電圧を高めても安定して充放電を行うことができ、充放電時の耐久性を向上できる。また、充放電の上限電圧を高めることができるため、電極活物質の容量を有効に利用でき、キャパシタを高容量化することもできる。 The capacitor according to the embodiment of the present invention can stably charge and discharge even when the upper limit voltage of charging and discharging is increased, and can improve durability during charging and discharging. In addition, since the upper limit voltage of charging / discharging can be increased, the capacity of the electrode active material can be used effectively, and the capacity of the capacitor can be increased.
　本発明の一実施形態に係る充放電方法は、キャパシタを、電圧Ｖ2以上（つまり、上記上限電圧Ｖ2と同じかもしくはこれよりも大きい電圧）の上限電圧で、充放電する工程を含む。キャパシタは、電圧Ｖ2以上の充放電（つまり、充電）の上限電圧を有する。
　アルカリ金属イオンキャパシタでは、充放電（つまり、充電）の上限電圧は、電圧４．２Ｖを超えることが好ましく、さらに好ましくは４．３Ｖ以上である。上限電圧は、４．４Ｖ以上または４．５Ｖ以上であってもよい。上限電圧は、５Ｖを超える値にすることもできるが、５Ｖ以下であることが好ましく、４．９Ｖ以下または４．７Ｖ以下であってもよい。これらの下限値と上限値とは任意に組み合わせることができる。充電の上限電圧は、例えば、４．２Ｖを超えて５Ｖ以下、４．３～５Ｖ、または４．５～５Ｖであってもよい。 The charge / discharge method according to an embodiment of the present invention includes a step of charging / discharging a capacitor with an upper limit voltage equal to or higher than the voltage V 2 (that is, a voltage equal to or higher than the upper limit voltage V 2 ). Capacitor has an upper limit voltage of the voltage V 2 or more charge-discharge (i.e., charging).
In the alkali metal ion capacitor, the upper limit voltage of charging / discharging (that is, charging) is preferably higher than 4.2V, and more preferably 4.3V or higher. The upper limit voltage may be 4.4 V or higher or 4.5 V or higher. Although an upper limit voltage can also be made into the value exceeding 5V, it is preferable that it is 5V or less, and 4.9V or less or 4.7V or less may be sufficient. These lower limit values and upper limit values can be arbitrarily combined. The upper limit voltage of charging may be, for example, more than 4.2V and 5V or less, 4.3 to 5V, or 4.5 to 5V.
　特定の第１電極集電体を用いるとともに、第１電極密度を上記の範囲とすることで、電圧Ｖ2以上の上限電圧まで充電しても、安定に充放電を可逆的に行うことができ、キャパシタの耐久性を向上できる。充電電圧を高めることができるため、電極活物質の容量を有効に利用でき、キャパシタを高容量化できる。 By using a specific first electrode current collector and setting the first electrode density within the above range, charging and discharging can be performed reversibly stably even when charging up to an upper limit voltage of voltage V 2 or higher. The durability of the capacitor can be improved. Since the charging voltage can be increased, the capacity of the electrode active material can be used effectively, and the capacity of the capacitor can be increased.
　キャパシタの充放電の上限電圧は、ユーザーなどにより自由に決定できるものではなく、キャパシタの構成要素に応じて、キャパシタの設計時に決定されるキャパシタの特性である。キャパシタの充放電は、通常、予め設定された電圧範囲内で行われる。具体的には、予め設定された上限電圧に達するまでキャパシタを充電し、予め設定された終止電圧に達するまでキャパシタを放電する。充電と放電は、通常、キャパシタを含む充放電システムにおける充電制御ユニットおよび放電制御ユニットが担う。本発明の実施形態には、キャパシタと、キャパシタの充電を制御する充電制御ユニットと、キャパシタの放電を制御する放電制御ユニットとを含む充放電システムも包含される。放電制御ユニットは、キャパシタから供給される電力を消費する負荷機器を含んでもよい。 The upper limit voltage for charging and discharging a capacitor cannot be determined freely by the user, but is a characteristic of the capacitor determined at the time of designing the capacitor according to the component of the capacitor. Charging and discharging of the capacitor is usually performed within a preset voltage range. Specifically, the capacitor is charged until a preset upper limit voltage is reached, and the capacitor is discharged until a preset end voltage is reached. Charging and discharging are usually performed by a charge control unit and a discharge control unit in a charge / discharge system including a capacitor. Embodiments of the present invention also include a charge / discharge system including a capacitor, a charge control unit that controls charging of the capacitor, and a discharge control unit that controls discharge of the capacitor. The discharge control unit may include a load device that consumes power supplied from the capacitor.
　図２は、本発明の一実施形態に係る充放電システムを概略的に示す構成図である。
　充放電システム１００は、キャパシタ１０１と、キャパシタ１０１の充放電を制御する充放電制御ユニット１０２と、キャパシタ１０１から供給される電力を消費する負荷機器１０３とを含む。充放電制御ユニット１０２は、キャパシタ１０１を充電する際の電流および／または電圧などを制御する充電制御ユニット１０２ａと、キャパシタ１０１を放電する際の電流および／または電圧などを制御する放電制御ユニット１０２ｂとを含む。充電制御ユニット１０２ａは、外部電源１０４およびキャパシタ１０１と接続しており、放電制御ユニット１０２ｂは、キャパシタ１０１と接続している。キャパシタ１０１には、負荷機器１０３が接続している。 FIG. 2 is a block diagram schematically showing a charge / discharge system according to an embodiment of the present invention.
The charge / discharge system 100 includes a capacitor 101, a charge / discharge control unit 102 that controls charge / discharge of the capacitor 101, and a load device 103 that consumes power supplied from the capacitor 101. The charge / discharge control unit 102 includes a charge control unit 102a that controls current and / or voltage when the capacitor 101 is charged, and a discharge control unit 102b that controls current and / or voltage when the capacitor 101 is discharged. including. The charge control unit 102 a is connected to the external power source 104 and the capacitor 101, and the discharge control unit 102 b is connected to the capacitor 101. A load device 103 is connected to the capacitor 101.
［付記］
　以上の実施形態に関し、さらに以下の付記を開示する。
　（付記１）
　第１電極活物質を含む第１電極、前記第１電極と反対の極性を有し、かつ第２電極活物質を含む第２電極、前記第１電極と前記第２電極との間に介在するセパレータ、ならびにアニオンおよびカチオンを含む電解質を含むキャパシタであって、
　前記キャパシタは、アルカリ金属イオンキャパシタまたは電気二重層キャパシタであり、
　前記第１電極は、アルミニウムまたはアルミニウム合金を含む三次元網目状の第１電極集電体と、前記第１電極集電体に充填され、かつ前記第１電極活物質を含む第１電極合剤とを含み、
　前記第１電極活物質は、少なくとも前記アニオンを可逆的に担持する材料を含み、
　前記第１電極中の前記第１電極合剤の含有量は、３０～９０質量％であり、
　前記第１電極の密度は、０．３～１．１ｇ／ｃｍ3であり、
　上限電圧Ｖ1で充放電したときの容量Ｃ1に対する上限電圧Ｖ2で充放電したときの容量Ｃ2の比：Ｃ2／Ｃ1は、１．３以上であり、
　前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ1は３．８Ｖであり、前記上限電圧Ｖ2は４．２Ｖであり、
　前記電気二重層キャパシタにおいて、前記上限電圧Ｖ1は２．５Ｖであり、前記上限電圧Ｖ2は２．９Ｖであるキャパシタ。
　このようなキャパシタでは、充放電の上限電圧を、Ｖ2以上の高い電圧まで高めても、充放電を安定に行うことができ、耐久性に優れるキャパシタが得られる。 [Appendix]
Regarding the above embodiment, the following additional notes are disclosed.
(Appendix 1)
A first electrode including a first electrode active material; a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material; and being interposed between the first electrode and the second electrode. A capacitor comprising a separator and an electrolyte comprising an anion and a cation,
The capacitor is an alkali metal ion capacitor or an electric double layer capacitor,
The first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
The first electrode active material includes at least a material that reversibly supports the anion,
The content of the first electrode mixture in the first electrode is 30 to 90% by mass,
The density of the first electrode is 0.3 to 1.1 g / cm 3 ,
Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
In the alkali metal ion capacitor, the upper limit voltage V 1 is 3.8V, the upper limit voltage V 2 is 4.2V,
In the electric double layer capacitor, the upper limit voltage V 1 is 2.5V, and the upper limit voltage V 2 is 2.9V.
In such a capacitor, even if the upper limit voltage of charging / discharging is increased to a high voltage of V 2 or higher, charging / discharging can be performed stably, and a capacitor having excellent durability can be obtained.
　（付記２）
　アルカリ金属イオンキャパシタであり、
　前記第１電極集電体は、中空の骨格を有し、
　前記容量Ｃ1に対する４．５Ｖの上限電圧で充放電したときの容量Ｃ3の比：Ｃ3／Ｃ1は、１．７以上であり、
　前記第１電極の厚みは、１５０～１５００μｍであることが好ましい。
　このようなキャパシタでは、４．５Ｖ以上の上限電圧まで充電しても、安定に充放電を可逆的に行うことができ、充放電に伴う容量の低下を抑制でき、その結果、キャパシタの耐久性をより効果的に向上できる。 (Appendix 2)
An alkali metal ion capacitor,
The first electrode current collector has a hollow skeleton,
Ratio of capacity C 3 when charging / discharging with upper limit voltage of 4.5V with respect to capacity C 1 : C 3 / C 1 is 1.7 or more,
The thickness of the first electrode is preferably 150 to 1500 μm.
In such a capacitor, even when it is charged to an upper limit voltage of 4.5 V or more, charging and discharging can be performed stably and reversibly, and a decrease in capacity due to charging and discharging can be suppressed. As a result, the durability of the capacitor Can be improved more effectively.
　（付記３）
　上記付記１のキャパシタと、前記キャパシタの充電を制御する充電制御ユニットと、前記キャパシタの放電を制御する放電制御ユニットとを含む充放電システム。
　このような充放電システムでは、キャパシタの充放電の上限電圧を、例えば、Ｖ2以上の高い電圧まで高めても、充放電を安定に行うことができ、キャパシタの耐久性を向上できる。 (Appendix 3)
A charge / discharge system including the capacitor according to Supplementary Note 1, a charge control unit that controls charging of the capacitor, and a discharge control unit that controls discharge of the capacitor.
In such a charge / discharge system, even if the upper limit voltage of charge / discharge of the capacitor is increased to, for example, a voltage higher than V 2 , charge / discharge can be performed stably, and the durability of the capacitor can be improved.
　以下、本発明を実施例および比較例に基づいて具体的に説明するが、本発明は以下の実施例に限定されるものではない。 Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.
　実施例１
　下記の手順でリチウムイオンキャパシタを作製した。
（１）正極の作製
　（ａ）正極集電体の作製
　熱硬化性ポリウレタンの発泡体（気孔率：９５体積％、表面１インチ（＝２．５４ｃｍ）長さ当たりの空孔（セル）数：約５０個、縦１００ｍｍ×横３０ｍｍ×厚み１．１ｍｍ）を準備した。
　発泡体を、黒鉛、カーボンブラック（平均粒径Ｄ50：０．５μｍ）、樹脂バインダ、浸透剤、および消泡剤を含む導電性懸濁液の中に浸漬した後、乾燥することにより、発泡体の表面に導電性層を形成した。なお、懸濁液中の黒鉛およびカーボンブラックの含有量は合計で２５質量％であった。 Example 1
A lithium ion capacitor was produced according to the following procedure.
(1) Production of positive electrode (a) Production of positive electrode current collector Thermosetting polyurethane foam (porosity: 95 vol%, surface 1 inch (= 2.54 cm) Number of pores (cells) per length: About 50, 100 mm long × 30 mm wide × 1.1 mm thick) were prepared.
The foam is immersed in a conductive suspension containing graphite, carbon black (average particle size D 50 : 0.5 μm), a resin binder, a penetrating agent, and an antifoaming agent, and then dried to foam. A conductive layer was formed on the surface of the body. The total content of graphite and carbon black in the suspension was 25% by mass.
　表面に導電性層を形成した発泡体を、溶融塩アルミニウムメッキ浴中に浸漬して、電流密度３．６Ａ／ｄｍ2の直流電流を９０分間印加することにより、アルミニウム層を形成した。なお、発泡体の見掛け面積当たりのアルミニウム層の質量は、１５０ｇ／ｍ2であった。溶融塩アルミニウムメッキ浴は、３３ｍｏｌ％の１－エチル－３－メチルイミダゾリウムクロライドおよび６７ｍｏｌ％の塩化アルミニウムを含み、温度は、４０℃であった。 The foam having the conductive layer formed on the surface was immersed in a molten salt aluminum plating bath, and a direct current having a current density of 3.6 A / dm 2 was applied for 90 minutes to form an aluminum layer. The mass of the aluminum layer per apparent area of the foam was 150 g / m 2 . The molten salt aluminum plating bath contained 33 mol% 1-ethyl-3-methylimidazolium chloride and 67 mol% aluminum chloride, and the temperature was 40 ° C.
　表面にアルミニウム層が形成された発泡体を、５００℃の塩化リチウム－塩化カリウム共晶溶融塩中に浸漬し、－１Ｖの負電位を３０分間印加することにより、発泡体を分解させた。得られたアルミニウム製の多孔体を、溶融塩から取り出して冷却し、水洗し、乾燥させることにより正極集電体を得た。得られた正極集電体は、発泡体の空孔形状を反映した、空孔が連通した三次元網目状の多孔構造を有し、気孔率は９４体積％であり、平均空孔径は５５０μｍであり、ＢＥＴ法による比表面積（ＢＥＴ比表面積）は、３５０ｃｍ2／ｇであり、厚みは１１００μｍであった。また、三次元網目状のアルミニウム製の骨格は、発泡体の除去により形成された連通孔状の空洞を内部に有していた。このようにして正極集電体を得た。 The foam with the aluminum layer formed on the surface was immersed in a lithium chloride-potassium chloride eutectic molten salt at 500 ° C., and a negative potential of −1 V was applied for 30 minutes to decompose the foam. The obtained aluminum porous body was taken out from the molten salt, cooled, washed with water, and dried to obtain a positive electrode current collector. The obtained positive electrode current collector has a three-dimensional network-like porous structure in which pores communicate, reflecting the pore shape of the foam, has a porosity of 94% by volume, and an average pore diameter of 550 μm. Yes, the BET specific surface area (BET specific surface area) was 350 cm 2 / g, and the thickness was 1100 μm. In addition, the three-dimensional mesh-like aluminum skeleton had a communication hole-like cavity formed by removing the foam. In this way, a positive electrode current collector was obtained.
　（ｂ）正極の作製
　正極活物質として活性炭粉末（比表面積２３００ｍ2／ｇ、平均粒径約５μｍ）および導電助剤としてアセチレンブラック、バインダとしてＰＶＤＦ（濃度１２質量％でＰＶＤＦを含むＮＭＰ溶液）、および分散媒としてＮＭＰを、混合機にて混合、攪拌することにより、正極合剤スラリーを調製した。スラリー中の各成分の質量比は、活性炭：アセチレンブラック：ＰＶＤＦ＝８７：３：１０であった。
　得られた正極合剤スラリーを、上記工程（ａ）で得られた集電体に充填し、１００℃にて３０分乾燥した。乾燥物を、一対のロールを用いて厚み方向に圧縮することにより、正極を作製した。 (B) Preparation of positive electrode Activated carbon powder as a positive electrode active material (specific surface area 2300 m 2 / g, average particle size of about 5 μm), acetylene black as a conductive additive, PVDF as a binder (NMP solution containing PVDF at a concentration of 12% by mass), Then, NMP as a dispersion medium was mixed and stirred in a mixer to prepare a positive electrode mixture slurry. The mass ratio of each component in the slurry was activated carbon: acetylene black: PVDF = 87: 3: 10.
The obtained positive electrode mixture slurry was filled in the current collector obtained in the step (a) and dried at 100 ° C. for 30 minutes. The dried product was compressed in the thickness direction using a pair of rolls to produce a positive electrode.
（２）負極の作製
　（ａ）負極集電体の作製
　正極集電体の作製で用いたものと同じ熱硬化性ポリウレタンの発泡体の表面に、スパッタリングにより目付量５ｇ／ｃｍ2のＣｕ被膜（導電性層）を形成した。
　表面に導電性層を形成した発泡体をワークとして、硫酸銅メッキ浴中に浸漬して、陰極電流密度２Ａ／ｄｍ2の直流電流を印加することにより、表面にＣｕ層を形成した。硫酸銅メッキ浴は、２５０ｇ／Ｌの硫酸銅、５０ｇ／Ｌの硫酸、および３０ｇ／Ｌの塩化銅を含み、温度は、３０℃であった。 (2) Production of Negative Electrode (a) Production of Negative Electrode Current Collector A Cu film having a basis weight of 5 g / cm 2 is formed on the surface of the same thermosetting polyurethane foam as used in the production of the positive electrode current collector ( Conductive layer) was formed.
A foam having a conductive layer formed on the surface was used as a work, immersed in a copper sulfate plating bath, and a direct current having a cathode current density of 2 A / dm 2 was applied to form a Cu layer on the surface. The copper sulfate plating bath contained 250 g / L copper sulfate, 50 g / L sulfuric acid, and 30 g / L copper chloride, and the temperature was 30 ° C.
　表面にＣｕ層が形成された発泡体を、大気雰囲気下、７００℃で熱処理することにより、発泡体を分解させ、次いで、水素雰囲気下で焼成することにより表面に形成された酸化被膜を還元することにより、銅製の多孔体（負極集電体）を得た。得られた負極集電体は、発泡体の空孔形状を反映した、空孔が連通した三次元網目状の多孔構造を有し、気孔率は９２体積％であり、平均空孔径は５５０μｍであり、ＢＥＴ比表面積は２００ｃｍ2／ｇであった。また、三次元網目状の銅製の骨格は、発泡体の除去により形成された連通孔状の空洞を内部に有していた。 The foam with the Cu layer formed on the surface is heat-treated at 700 ° C. in an air atmosphere to decompose the foam, and then fired in a hydrogen atmosphere to reduce the oxide film formed on the surface. As a result, a copper porous body (negative electrode current collector) was obtained. The obtained negative electrode current collector had a three-dimensional network-like porous structure in which pores communicated, reflecting the pore shape of the foam, had a porosity of 92% by volume, and an average pore diameter of 550 μm. The BET specific surface area was 200 cm 2 / g. In addition, the three-dimensional network copper skeleton had a communication hole-like cavity formed by removing the foam.
　（ｂ）負極の作製
　負極活物質としての人造黒鉛粉末と、導電助剤としてのアセチレンブラックと、バインダとしてのＰＶＤＦと、分散媒としてのＮＭＰとを混合することにより、負極合剤スラリーを調製した。黒鉛粉末と、アセチレンブラックと、ＰＶＤＦとの質量比は、９０：５：５であった。
　得られた負極合剤スラリーを、上記工程（ａ）で得られた集電体に充填し、１００℃にて３０分乾燥した。乾燥物を、一対のロールを用いて圧延し、厚み１３０μｍの負極を作製した。
　なお、工程（１）および（２）では、プレドープ後の負極の充電可能な容量が、正極の容量の約２倍となるように、正極合剤および負極合剤の充填量を調節した。 (B) Production of negative electrode A negative electrode mixture slurry was prepared by mixing artificial graphite powder as a negative electrode active material, acetylene black as a conductive additive, PVDF as a binder, and NMP as a dispersion medium. . The mass ratio of the graphite powder, acetylene black, and PVDF was 90: 5: 5.
The obtained negative electrode mixture slurry was filled in the current collector obtained in the step (a) and dried at 100 ° C. for 30 minutes. The dried product was rolled using a pair of rolls to produce a negative electrode having a thickness of 130 μm.
In steps (1) and (2), the filling amounts of the positive electrode mixture and the negative electrode mixture were adjusted so that the chargeable capacity of the negative electrode after pre-doping was about twice the capacity of the positive electrode.
（３）リチウム極の作製
　集電体としてのパンチング銅箔（厚み：２０μｍ、開口径：５０μｍ、開口率５０％、２ｃｍ×２ｃｍ）の一方の表面に、リチウム箔（厚み：５０μｍ）を圧着することにより、リチウム極を作製した。リチウム極の集電体の他方の表面には、ニッケル製のリードを溶接した。 (3) Production of lithium electrode A lithium foil (thickness: 50 μm) is pressure-bonded to one surface of a punching copper foil (thickness: 20 μm, opening diameter: 50 μm, opening ratio 50%, 2 cm × 2 cm) as a current collector. Thus, a lithium electrode was produced. A nickel lead was welded to the other surface of the current collector of the lithium electrode.
（４）リチウムイオンキャパシタの作製
　上記（１）および（２）で得られた正極および負極を、それぞれ、１．５ｃｍ×１．５ｃｍのサイズに切り出し、１辺に沿って幅０．５ｍｍの部分の合剤を取り除いて集電体露出部を形成した。正極の集電体露出部には、アルミニウム製のリードを、負極集電体露出部には、ニッケル製のリードを、それぞれ溶接した。なお、得られた正極および負極において、合剤が存在する部分の面積は、いずれも、１．５ｃｍ2であった。 (4) Production of Lithium Ion Capacitor The positive electrode and the negative electrode obtained in (1) and (2) above were cut into a size of 1.5 cm × 1.5 cm, respectively, and a portion having a width of 0.5 mm along one side The mixture was removed to form a current collector exposed portion. An aluminum lead was welded to the positive electrode current collector exposed portion, and a nickel lead was welded to the negative electrode current collector exposed portion. In the obtained positive electrode and negative electrode, the area of the portion where the mixture was present was 1.5 cm 2 .
　正極と負極との間に、セルロース製のセパレータ（厚み：６０μｍ）を介在させて正極と負極とを積層することにより単セルの電極群を形成した。さらに、電極群の負極側に、ポリオレフィン製のセパレータ（ポリエチレン微多孔膜とポリプロピレン微多孔膜との積層体）を介在させて、リチウム極を配置し、得られた積層物を、アルミニウムラミネートシートで作製されたセルケース内に収容した。 A single-cell electrode group was formed by laminating a positive electrode and a negative electrode with a cellulose separator (thickness: 60 μm) interposed between the positive electrode and the negative electrode. Further, a lithium separator is disposed on the negative electrode side of the electrode group with a polyolefin separator (a laminate of a polyethylene microporous membrane and a polypropylene microporous membrane), and the obtained laminate is made of an aluminum laminate sheet. It accommodated in the produced cell case.
　次いで、電解質をセルケース内に注入して、正極、負極およびセパレータに含浸させた。電解質としては、エチレンカーボネートおよびジエチルカーボネートを体積比１：１で含む混合溶媒に、リチウム塩としてＬｉＰＦ6を１．０ｍｏｌ／Ｌの濃度となるように溶解させた溶液を用いた。最後に真空シーラーにて減圧しながらセルケースを封止した。 Next, an electrolyte was injected into the cell case, and the positive electrode, the negative electrode, and the separator were impregnated. As the electrolyte, a solution in which LiPF 6 as a lithium salt was dissolved to a concentration of 1.0 mol / L in a mixed solvent containing ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 was used. Finally, the cell case was sealed while reducing the pressure with a vacuum sealer.
　負極のリード線とリチウム極のリード線とを、セルケース外部で電源に接続した。この状態のセルを、３０℃の恒温槽内で、電解質の温度が恒温槽の温度と同じになるように所定時間静置した。次いで、負極とリチウム極との間で、０．２ｍＡ／ｃｍ2の電流で、金属リチウムに対して０Ｖの電位まで充電した後、０．２ｍＡ／ｃｍ2の電流で２．３ｍＡｈ放電して、負極活物質にリチウムをプレドープすることによりリチウムイオンキャパシタ（Ａ１）を作製した。リチウムイオンキャパシタＡ１の設計容量は、３．８Ｖ充電時で約１．０ｍＡｈ／ｃｍ2であった。 The negative electrode lead wire and the lithium electrode lead wire were connected to a power source outside the cell case. The cell in this state was allowed to stand for a predetermined time in a thermostat at 30 ° C. so that the temperature of the electrolyte was the same as the temperature of the thermostat. Then, between the negative electrode and the lithium electrode, with a current 0.2 mA / cm 2, it was charged to a potential of 0V with respect to metallic lithium, and 2.3mAh discharged at a current 0.2 mA / cm 2, A lithium ion capacitor (A1) was produced by pre-doping lithium into the negative electrode active material. The design capacity of the lithium ion capacitor A1 was about 1.0 mAh / cm 2 when charged at 3.8V.
　得られた正極および負極、ならびにリチウムイオンキャパシタを用いて、下記の評価を行った。
（ａ）電極密度
　正極の質量を測定し、この質量を正極の見かけ体積で除することで、正極の密度（ｇ／ｃｍ3）を算出した。
（ｂ）キャパシタの容量
　キャパシタを、１ｍＡ／ｃｍ2の電流で、上限電圧３．８Ｖまで充電し、１ｍＡ／ｃｍ2の電流で、電圧が２．２Ｖになるまで放電した。この充放電サイクルを１０回繰り返し、１０回目の放電時の放電容量Ｃ1（ｍＡｈ）を求めた。
　充電の上限電圧を、４．２Ｖまたは４．５Ｖに変更する以外は、上記と同様にして、放電容量Ｃ2およびＣ3を求め、Ｃ1に対するこれらの放電容量の比Ｃ2／Ｃ1およびＣ3／Ｃ1を算出した。 The following evaluation was performed using the obtained positive and negative electrodes and a lithium ion capacitor.
(A) Electrode density The positive electrode density (g / cm 3 ) was calculated by measuring the mass of the positive electrode and dividing this mass by the apparent volume of the positive electrode.
(B) Capacitor Capacitor The capacitor was charged with a current of 1 mA / cm 2 to an upper limit voltage of 3.8 V and discharged with a current of 1 mA / cm 2 until the voltage reached 2.2 V. This charge / discharge cycle was repeated 10 times, and the discharge capacity C 1 (mAh) at the 10th discharge was determined.
The upper limit voltage of charging, except for changing the 4.2V or 4.5V, in the same manner as described above, the discharge capacity C 2 and C 3 determined, the ratio C 2 / C 1 and of the discharge capacity with respect to C 1 C 3 / C 1 was calculated.
　比較例１および２
　正極集電体としてアルミニウム箔（厚み２０μｍ）を用い、アルミニウム箔の片面に正極合剤スラリーを塗布して、正極合剤の層を形成する以外は、実施例１と同様にして正極を作製した。正極合剤の層を形成する際、正極の密度および厚みが表１に示す値となるように、正極合剤スラリーの塗布量およびロールを用いて圧縮する際の圧縮率を適宜変更した。得られた正極を用いる以外は、実施例１と同様にして、リチウムイオンキャパシタ（Ｂ１およびＢ２）を作製し、評価を行った。 Comparative Examples 1 and 2
A positive electrode was produced in the same manner as in Example 1 except that an aluminum foil (thickness 20 μm) was used as the positive electrode current collector, and the positive electrode mixture slurry was applied to one surface of the aluminum foil to form a positive electrode mixture layer. . When forming the positive electrode mixture layer, the coating amount of the positive electrode mixture slurry and the compression ratio when compressing with a roll were appropriately changed so that the density and thickness of the positive electrode were as shown in Table 1. Lithium ion capacitors (B1 and B2) were produced and evaluated in the same manner as in Example 1 except that the obtained positive electrode was used.
　実施例２および３、ならびに比較例３
　正極および負極の厚みが表１に示す値となるように、合剤の充填量およびロールを用いて乾燥物を圧縮する際の圧縮率を変更する以外は、実施例１と同様にして正極および負極を作製した。このとき、正極と負極との容量バランスが、実施例１とほぼ同じになるようにした。得られた正極および負極を用いる以外は、実施例１と同様にして、リチウムイオンキャパシタ（Ａ２、Ａ３およびＢ３）を作製し、評価を行った。
　実施例および比較例の結果を、正極の密度、正極中の正極合剤の含有量および厚みとともに、表１に示す。なお、リチウムイオンキャパシタＡ１～Ａ３は実施例であり、Ｂ１～Ｂ３は比較例である。 Examples 2 and 3 and Comparative Example 3
The positive electrode and the negative electrode were changed in the same manner as in Example 1 except that the filling amount of the mixture and the compressibility when the dried product was compressed using a roll were changed so that the thicknesses of the positive electrode and the negative electrode were as shown in Table 1. A negative electrode was produced. At this time, the capacity balance between the positive electrode and the negative electrode was made substantially the same as in Example 1. Lithium ion capacitors (A2, A3 and B3) were prepared and evaluated in the same manner as in Example 1 except that the obtained positive and negative electrodes were used.
The results of Examples and Comparative Examples are shown in Table 1 together with the density of the positive electrode, the content and thickness of the positive electrode mixture in the positive electrode. The lithium ion capacitors A1 to A3 are examples, and B1 to B3 are comparative examples.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示されるように、正極の密度が特定の範囲内である実施例のリチウムイオンキャパシタＡ１～Ａ３では、上限電圧が４．２Ｖ（Ｖ2）または４．５Ｖ（Ｖ3）と高くなっても、安定に充放電することができ、充放電を繰り返しても高い放電容量が維持され、優れた耐久性が得られた。正極集電体としてアルミニウム箔を用いたリチウムイオンキャパシタＢ１およびＢ２では、上限電圧を４．２Ｖまたは４．５Ｖに高めても容量の向上効果は小さく、実施例とは異なる挙動を示した。リチウムイオンキャパシタＢ１では、特に、容量比Ｃ２／Ｃ１およびＣ３／Ｃ１の値が小さく、上限電圧を高めることによる効果はほとんど得られていないと言える。リチウムイオンキャパシタＢ２は、容量比Ｃ２／Ｃ１およびＣ３／Ｃ１の値はリチウムイオンキャパシタＢ１に比べると大きいが、実施例に比べると低く、サイクル後の放電容量の値自体も小さかった。 As shown in Table 1, in the lithium ion capacitors A1 to A3 of the examples in which the density of the positive electrode is within a specific range, the upper limit voltage is as high as 4.2 V (V 2 ) or 4.5 V (V 3 ). Even if charging / discharging was repeated, a high discharge capacity was maintained even when charging / discharging was repeated, and excellent durability was obtained. In the lithium ion capacitors B1 and B2 using the aluminum foil as the positive electrode current collector, the capacity improvement effect was small even when the upper limit voltage was increased to 4.2 V or 4.5 V, and the behavior was different from that of the example. In particular, in the lithium ion capacitor B1, the values of the capacitance ratios C2 / C1 and C3 / C1 are small, and it can be said that the effect of increasing the upper limit voltage is hardly obtained. In the lithium ion capacitor B2, the values of the capacity ratios C2 / C1 and C3 / C1 were larger than those of the lithium ion capacitor B1, but were lower than those of the examples, and the value of the discharge capacity after the cycle itself was also small.
　正極集電体として実施例と同様のアルミニウム多孔体を用いたリチウムイオンキャパシタＢ３では、容量比Ｃ２／Ｃ１およびＣ３／Ｃ１の値はリチウムイオンキャパシタＢ２と同程度であり、実施例と比較すると、サイクル後の放電容量の値自体が小さく、耐久性の点で劣っていた。
　なお、上記の結果は、リチウムイオンキャパシタを用いた場合のものであるが、ＥＤＬＣについても、リチウムイオンキャパシタと同様のまたは類似の結果が得られる。具体的には、ＥＤＬＣの場合、Ｖ1が２．５Ｖ、Ｖ2が２．９Ｖであり、Ｖ3が３．２Ｖである場合に、リチウムイオンキャパシタの上記の結果と同様の傾向が確認できる。 In the lithium ion capacitor B3 using the same aluminum porous body as in the example as the positive electrode current collector, the values of the capacitance ratios C2 / C1 and C3 / C1 are approximately the same as those of the lithium ion capacitor B2, and compared with the example, The value of the discharge capacity after the cycle was small, and the durability was inferior.
In addition, although said result is a thing at the time of using a lithium ion capacitor, the same or similar result as a lithium ion capacitor is obtained also about EDLC. Specifically, in the case of EDLC, when V 1 is 2.5 V, V 2 is 2.9 V, and V 3 is 3.2 V, the same tendency as the above result of the lithium ion capacitor can be confirmed. .
　本発明の一実施形態に係るキャパシタは、充電電圧を高めても、充放電を安定して可逆的に行うことができるため、耐久性に優れるキャパシタを得ることができる。よって、耐久性（または高いサイクル特性）が求められる様々な用途に適用することができる。 Since the capacitor according to one embodiment of the present invention can stably charge and discharge reversibly even when the charging voltage is increased, a capacitor having excellent durability can be obtained. Therefore, it can be applied to various uses that require durability (or high cycle characteristics).
　１：セパレータ
　２：第１電極
　２ａ：電極リード片
　３：第２電極
　３ａ：電極リード片
　７：ナット
　８：鍔部
　９：ワッシャ
　１０：セルケース
　１２：容器本体
　１３：蓋体
　１４：外部電極端子
　１６：安全弁 1: Separator 2: First electrode 2a: Electrode lead piece 3: Second electrode 3a: Electrode lead piece 7: Nut 8: Hook 9: Washer 10: Cell case 12: Container body 13: Lid 14: External electrode terminal 16: Safety valve
　１００：充放電システム
　１０１：キャパシタ
　１０２：充放電制御ユニット
　１０２ａ：充電制御ユニット
　１０２ｂ：放電制御ユニット
　１０３：負荷機器 DESCRIPTION OF SYMBOLS 100: Charge / discharge system 101: Capacitor 102: Charge / discharge control unit 102a: Charge control unit 102b: Discharge control unit 103: Load apparatus

Claims (6)

  1. 　第１電極活物質を含む第１電極、前記第１電極と反対の極性を有し、かつ第２電極活物質を含む第２電極、前記第１電極と前記第２電極との間に介在するセパレータ、ならびにアニオンおよびカチオンを含む電解質を含むキャパシタであって、
    　前記キャパシタは、アルカリ金属イオンキャパシタまたは電気二重層キャパシタであり、
    　前記第１電極は、アルミニウムまたはアルミニウム合金を含む三次元網目状の第１電極集電体と、前記第１電極集電体に充填され、かつ前記第１電極活物質を含む第１電極合剤とを含み、
    　前記第１電極活物質は、少なくとも前記アニオンを可逆的に担持する材料を含み、
    　前記第１電極中の前記第１電極合剤の含有量は、３０～９０質量％であり、
    　前記第１電極の密度は、０．３～１．１ｇ／ｃｍ3であり、
    　上限電圧Ｖ1で充放電したときの容量Ｃ1に対する上限電圧Ｖ2で充放電したときの容量Ｃ2の比：Ｃ2／Ｃ1は、１．３以上であり、
    　前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ1は３．８Ｖであり、前記上限電圧Ｖ2は４．２Ｖであり、
    　前記電気二重層キャパシタにおいて、前記上限電圧Ｖ1は２．５Ｖであり、前記上限電圧Ｖ2は２．９Ｖであるキャパシタ。     A first electrode including a first electrode active material; a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material; and being interposed between the first electrode and the second electrode. A capacitor comprising a separator and an electrolyte comprising an anion and a cation,
    The capacitor is an alkali metal ion capacitor or an electric double layer capacitor,
    The first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
    The first electrode active material includes at least a material that reversibly supports the anion,
    The content of the first electrode mixture in the first electrode is 30 to 90% by mass,
    The density of the first electrode is 0.3 to 1.1 g / cm 3 ,
    Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
    In the alkali metal ion capacitor, the upper limit voltage V 1 is 3.8V, the upper limit voltage V 2 is 4.2V,
    In the electric double layer capacitor, the upper limit voltage V 1 is 2.5V, and the upper limit voltage V 2 is 2.9V.
  2. 　前記第１電極集電体は、中空の骨格を有する請求項１に記載のキャパシタ。 The capacitor according to claim 1, wherein the first electrode current collector has a hollow skeleton.
  3. 　前記容量Ｃ1に対する上限電圧Ｖ3で充放電したときの容量Ｃ3の比：Ｃ3／Ｃ1は、１．７以上であり、
    　前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ3は４．５Ｖであり、
    　前記電気二重層キャパシタにおいて、前記上限電圧Ｖ3は３．２Ｖである請求項１または請求項２に記載のキャパシタ。     Ratio of capacity C 3 when charging / discharging with upper limit voltage V 3 with respect to capacity C 1 : C 3 / C 1 is 1.7 or more,
    In the alkali metal ion capacitor, the upper limit voltage V 3 is 4.5V,
    The capacitor according to claim 1, wherein the upper limit voltage V 3 is 3.2 V in the electric double layer capacitor.
  4. 　前記第１電極の厚みは、１００～２０００μｍである請求項１～請求項３のいずれか１項に記載のキャパシタ。 The capacitor according to any one of claims 1 to 3, wherein a thickness of the first electrode is 100 to 2000 µm.
  5. 　前記キャパシタは、アルカリ金属イオンキャパシタであり、
    　前記カチオンは、アルカリ金属イオンを含み、
    　前記第２電極活物質は、前記アルカリ金属イオンを可逆的に担持する材料を含む請求項１～請求項４のいずれか１項に記載のキャパシタ。     The capacitor is an alkali metal ion capacitor,
    The cation includes an alkali metal ion,
    5. The capacitor according to claim 1, wherein the second electrode active material includes a material that reversibly carries the alkali metal ion.
  6. 　キャパシタの充放電方法であって、
    　前記キャパシタは、第１電極活物質を含む第１電極、前記第１電極と反対の極性を有し、かつ第２電極活物質を含む第２電極、前記第１電極と前記第２電極との間に介在するセパレータ、ならびにアニオンおよびカチオンを含む電解質を含むアルカリ金属イオンキャパシタまたは電気二重層キャパシタであり、
    　前記第１電極は、アルミニウムまたはアルミニウム合金を含む三次元網目状の第１電極集電体と、前記第１電極集電体に充填され、かつ前記第１電極活物質を含む第１電極合剤とを含み、
    　前記第１電極活物質は、少なくとも前記アニオンを可逆的に担持する材料を含み、
    　前記第１電極中の前記第１電極合剤の含有量は、３０～９０質量％であり、
    　前記第１電極の密度は、０．３～１．１ｇ／ｃｍ3であり、
    　上限電圧Ｖ1で充放電したときの容量Ｃ1に対する上限電圧Ｖ2で充放電したときの容量Ｃ2の比：Ｃ2／Ｃ1は、１．３以上であり、
    　前記アルカリ金属イオンキャパシタにおいて、前記上限電圧Ｖ1は３．８Ｖであり、前記上限電圧Ｖ2は４．２Ｖであり、
    　前記電気二重層キャパシタにおいて、前記上限電圧Ｖ1は２．５Ｖであり、前記上限電圧Ｖ2は２．９Ｖであり、
    　前記キャパシタを、前記上限電圧Ｖ2以上の上限電圧で充放電する工程を有する充放電方法。     A capacitor charging / discharging method comprising:
    The capacitor includes a first electrode including a first electrode active material, a second electrode having a polarity opposite to that of the first electrode and including a second electrode active material, and the first electrode and the second electrode. An alkali metal ion capacitor or an electric double layer capacitor comprising an intervening separator and an electrolyte containing an anion and a cation,
    The first electrode is a three-dimensional network-shaped first electrode current collector containing aluminum or an aluminum alloy, and a first electrode mixture filled in the first electrode current collector and containing the first electrode active material Including
    The first electrode active material includes at least a material that reversibly supports the anion,
    The content of the first electrode mixture in the first electrode is 30 to 90% by mass,
    The density of the first electrode is 0.3 to 1.1 g / cm 3 ,
    Ratio of capacity C 2 when charging / discharging with upper limit voltage V 2 to capacity C 1 when charging / discharging with upper limit voltage V 1 : C 2 / C 1 is 1.3 or more,
    In the alkali metal ion capacitor, the upper limit voltage V 1 is 3.8V, the upper limit voltage V 2 is 4.2V,
    In the electric double layer capacitor, the upper limit voltage V 1 is 2.5V, the upper limit voltage V 2 is 2.9V,
    The capacitor, charging and discharging method comprising the step of charging and discharging at the upper limit voltage V 2 or more the upper limit voltage.
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Citations (6)

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JP3591055B2 (en) * 1995-06-12 2004-11-17 旭硝子株式会社 Electric double layer capacitor, method of manufacturing the same, and method of manufacturing electrodes therefor
JP2011254029A (en) * 2010-06-04 2011-12-15 Sumitomo Electric Ind Ltd Capacitor prepared using metal porous body
JP2012119465A (en) * 2010-11-30 2012-06-21 Mitsubishi Materials Corp Electrode for electric double layer capacitor and electric double layer capacitor using thereof
JP2012243924A (en) * 2011-05-19 2012-12-10 Sumitomo Electric Ind Ltd Capacitor
WO2013054710A1 (en) * 2011-10-12 2013-04-18 住友電気工業株式会社 Lithium ion capacitor, power storage device, power storage system
WO2013061789A1 (en) * 2011-10-27 2013-05-02 住友電気工業株式会社 Capacitor

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JP3591055B2 (en) * 1995-06-12 2004-11-17 旭硝子株式会社 Electric double layer capacitor, method of manufacturing the same, and method of manufacturing electrodes therefor
JP2011254029A (en) * 2010-06-04 2011-12-15 Sumitomo Electric Ind Ltd Capacitor prepared using metal porous body
JP2012119465A (en) * 2010-11-30 2012-06-21 Mitsubishi Materials Corp Electrode for electric double layer capacitor and electric double layer capacitor using thereof
JP2012243924A (en) * 2011-05-19 2012-12-10 Sumitomo Electric Ind Ltd Capacitor
WO2013054710A1 (en) * 2011-10-12 2013-04-18 住友電気工業株式会社 Lithium ion capacitor, power storage device, power storage system
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