WO2017170065A1 - 電気化学素子用セパレータ及び電気化学素子 - Google Patents
電気化学素子用セパレータ及び電気化学素子 Download PDFInfo
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- WO2017170065A1 WO2017170065A1 PCT/JP2017/011532 JP2017011532W WO2017170065A1 WO 2017170065 A1 WO2017170065 A1 WO 2017170065A1 JP 2017011532 W JP2017011532 W JP 2017011532W WO 2017170065 A1 WO2017170065 A1 WO 2017170065A1
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- separator
- value
- electrochemical element
- frequency
- nonwoven fabric
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- 239000000835 fiber Substances 0.000 claims abstract description 39
- 239000004745 nonwoven fabric Substances 0.000 claims abstract description 32
- 239000008151 electrolyte solution Substances 0.000 claims abstract description 11
- 238000000151 deposition Methods 0.000 claims abstract description 4
- 239000003990 capacitor Substances 0.000 claims description 46
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 39
- 229910001416 lithium ion Inorganic materials 0.000 claims description 39
- 239000011148 porous material Substances 0.000 claims description 37
- 229920003043 Cellulose fiber Polymers 0.000 claims description 33
- 229910052782 aluminium Inorganic materials 0.000 claims description 21
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 21
- 239000004627 regenerated cellulose Substances 0.000 claims description 13
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 9
- 229910052744 lithium Inorganic materials 0.000 claims description 9
- 239000007788 liquid Substances 0.000 abstract description 4
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- -1 and for example Substances 0.000 description 9
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- 229920002678 cellulose Polymers 0.000 description 7
- 239000001913 cellulose Substances 0.000 description 7
- 239000003792 electrolyte Substances 0.000 description 6
- 238000004519 manufacturing process Methods 0.000 description 6
- 238000009826 distribution Methods 0.000 description 5
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- 230000005484 gravity Effects 0.000 description 5
- 238000010998 test method Methods 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 210000001787 dendrite Anatomy 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000012982 microporous membrane Substances 0.000 description 4
- 238000009783 overcharge test Methods 0.000 description 4
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- 239000012209 synthetic fiber Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- WEVYAHXRMPXWCK-UHFFFAOYSA-N Acetonitrile Chemical compound CC#N WEVYAHXRMPXWCK-UHFFFAOYSA-N 0.000 description 3
- 239000004698 Polyethylene Substances 0.000 description 3
- 230000006835 compression Effects 0.000 description 3
- 238000007906 compression Methods 0.000 description 3
- 230000002950 deficient Effects 0.000 description 3
- 239000011888 foil Substances 0.000 description 3
- 229920000573 polyethylene Polymers 0.000 description 3
- 229920000139 polyethylene terephthalate Polymers 0.000 description 3
- 239000005020 polyethylene terephthalate Substances 0.000 description 3
- 229920005672 polyolefin resin Polymers 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- 229920000875 Dissolving pulp Polymers 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 229920001131 Pulp (paper) Polymers 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 210000004027 cell Anatomy 0.000 description 2
- 229910052729 chemical element Inorganic materials 0.000 description 2
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- 230000010220 ion permeability Effects 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 2
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
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- 238000010008 shearing Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229920002972 Acrylic fiber Polymers 0.000 description 1
- 244000198134 Agave sisalana Species 0.000 description 1
- 241000218631 Coniferophyta Species 0.000 description 1
- 240000000491 Corchorus aestuans Species 0.000 description 1
- 235000011777 Corchorus aestuans Nutrition 0.000 description 1
- 235000010862 Corchorus capsularis Nutrition 0.000 description 1
- 229920000433 Lyocell Polymers 0.000 description 1
- 229920001407 Modal (textile) Polymers 0.000 description 1
- 240000000907 Musa textilis Species 0.000 description 1
- 239000004952 Polyamide Substances 0.000 description 1
- 239000004734 Polyphenylene sulfide Substances 0.000 description 1
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 239000004760 aramid Substances 0.000 description 1
- 229920006231 aramid fiber Polymers 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
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- 239000013078 crystal Substances 0.000 description 1
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- 238000010292 electrical insulation Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
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- 238000009499 grossing Methods 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
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- 229920001778 nylon Polymers 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920002239 polyacrylonitrile Polymers 0.000 description 1
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- 239000000843 powder Substances 0.000 description 1
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
- H01G11/52—Separators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G9/00—Electrolytic capacitors, rectifiers, detectors, switching devices, light-sensitive or temperature-sensitive devices; Processes of their manufacture
- H01G9/004—Details
- H01G9/02—Diaphragms; Separators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/411—Organic material
- H01M50/429—Natural polymers
- H01M50/4295—Natural cotton, cellulose or wood
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/44—Fibrous material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
- H01M50/491—Porosity
-
- 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
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to a separator for an electrochemical element and an electrochemical element.
- electrochemical elements such as capacitors, capacitors, and batteries have been adopted in new fields such as automobile-related equipment, and the market is expected to continue to expand in the future.
- a lithium-ion secondary battery is used as a power source for electric vehicles and hybrid vehicles
- an electric double layer capacitor is used for energy regeneration
- an electronic control unit ECU
- aluminum electrolytic capacitors and electric double layer capacitors are used for motor control, battery control, hybrid electric vehicle (HEV) system control, and DC conversion from an external AC power source.
- HEV hybrid electric vehicle
- the electrochemical element used for the power supply of a portable device is also required to be usable for a long time by one charge.
- an electrochemical element such as an aluminum electrolytic capacitor is mounted on a circuit board for the purpose of power supply to an electronic element on the circuit board and smoothing of an alternating current.
- Low profile and small size are required.
- lithium ion secondary batteries that are often used as power sources for portable devices are required to have a high capacity so that they can be used for a long time while being small and thin.
- the separator described in Patent Document 1 controls the beating degree and fiber length of solvent-spun cellulose fibers, and improves both the density and liquid retention of the separator. Specifically, by controlling the beating degree and fiber length of the solvent-spun cellulose fiber, the average pore diameter of the separator is controlled to 0.1 ⁇ m or more, and the maximum pore diameter is controlled to 6.0 ⁇ m or less so that the shielding property and electrolysis The separator has a liquid holding power.
- Patent Document 2 discloses a microporous film made of a thermoplastic resin mainly composed of a polyolefin-based resin as a separator used for an electrolytic capacitor or the like. By stretching after the film formation, fine pores are disclosed. Forming.
- the separator described in Patent Document 1 is a separator made of a nonwoven fabric using beaten solvent-spun cellulose fibers, and when trying to cope with the thinning required in recent years, the shielding properties of the separator are reduced, It was difficult to thin the leaf while maintaining high shielding performance.
- the separator described in Patent Document 2 is made of a polyolefin-based resin, has low wettability with respect to the electrolytic solution, cannot sufficiently hold the electrolytic solution, and cannot solve the problem that the resistance value increases.
- a separator made of a microporous membrane using a polyolefin-based resin can be obtained by partially melting or shrinking the separator when an electrochemical element (for example, a battery) is heated, thereby closing the pores. Some of them have a function of cutting off the current flowing through the battery and preventing the battery from becoming so hot as to cause thermal runaway.
- the high-capacity, high-power electrochemical devices required in recent years have a large current value, so even if the current is shut off due to the above-mentioned blockage of the holes, the heat generation in the battery cannot be suppressed, and the entire separator Melted (melted down) and could cause internal short circuit and thermal runaway.
- the present invention has been made in view of the above problems, and has an object to provide a separator that achieves both sufficient shielding and thinning, which has been difficult with conventional separators, and an electrochemical device using the separator. It was made.
- a separator for an electrochemical element that is made of a non-woven fabric formed by depositing fibers in a sheet shape and interposed between a pair of electrodes, and that holds an electrolytic solution, and has a pore diameter of 0.05 to 1.00 ⁇ m.
- the frequency is 90% or more of all holes.
- the frequency of the most frequent pore value of the nonwoven fabric is 60% or more with respect to the frequency of all sections.
- the frequency in the range of the most frequent pore value ⁇ 10% of the nonwoven fabric is 75% or more with respect to the frequency of all sections.
- the nonwoven fabric has a porosity of 35 to 80%. Further, for example, the thickness of the nonwoven fabric is 5 to 30 ⁇ m.
- the fibers forming the nonwoven fabric include regenerated cellulose fibers.
- the electrochemical element is any one of an aluminum electrolytic capacitor, an electric double layer capacitor, a lithium ion capacitor, a lithium primary battery, and a lithium ion secondary battery.
- an electrochemical element separator that achieves both sufficient shielding properties and thinning, and an electrochemical element that can be miniaturized and has a reduced short-circuit defect rate and improved safety.
- an embodiment of the present invention will be described in detail with reference to the drawings.
- a separator for an electrochemical element for example, an aluminum electrolytic capacitor, an electric double layer capacitor, a lithium ion capacitor, a lithium primary battery, a lithium ion secondary battery and the like are suitable.
- the main role of the separator in the electrochemical element is to isolate the pair of electrodes and hold the electrolyte.
- the separator In order to isolate a pair of electrodes, the separator is required to have high shielding properties. As the use of electrochemical devices expands, separators are further required to improve such performance.
- the separator material is required to have electrical insulation, and moreover, lyophilicity (lyophilic property) is required for holding various types of electrolytes.
- a separator material that satisfies the above-mentioned performance, there is cellulose.
- the fiber is refined and a paper / nonwoven fabric is formed from the refined fiber to obtain a very dense sheet.
- Cellulose fibers made finer have a shorter fiber length than synthetic fibers, etc., easily fill the gaps in the sheet, and improve the shielding properties of the separator. Therefore, separators made of cellulose fibers are widely adopted, Contributes to reducing short-circuit defects in chemical elements.
- the separator according to the present embodiment is a separator for an electrochemical element that has both sufficient shielding properties and thinning, and is excellent in wettability to electrolyte, liquid retention, and heat resistance.
- a separator having a frequency of pore diameters of 0.05 to 1.00 ⁇ m (hereinafter referred to as “A value”) is 90% or more of all the pores.
- the “hole” in the following description is a hole measured by a method defined in “ASTM F0314-03”. Further, the “moderate pore value” is the mode value of the pore diameter distribution measured by the method defined in “TEST METHOD B” of “ASTM F316-03”.
- a non-woven fabric having an A value of 90% or more has a very small pore diameter and a small variation in the existing pore diameter.
- the A value is less than 90%, the hole diameter is large or the hole diameter variation is large.
- the shielding property of the separator is important.
- the present inventors have found that the shielding performance cannot be improved from a certain level only by reducing the pore diameter of the separator.
- This dendrite grows in a portion where the growth resistance of the dendrite is small, that is, a portion where the separator has a small resistance value (a portion where the separator has relatively large pores). It is considered that there is a limit to improving the shielding performance. Also, for example, in a capacitor, since the resistance value is relatively small at a location where the separator has a large hole, it is considered that a short circuit failure is caused by lightning strike through the portion where the hole is large.
- the separator according to an embodiment of the present invention has a nonwoven fabric structure formed by depositing fibers in a sheet form. Examples of the nonwoven fabric forming method include the following methods.
- the sheet is formed by dispersing the fiber in water and draining it from the mesh surface by the papermaking method. That is, it is set as a wet nonwoven fabric.
- the method for forming the wet paper nonwoven fabric include a method using a long paper machine, a circular paper machine, a short paper machine, and a combination paper machine combining these.
- the separator is not limited to the specific papermaking method shown in this embodiment.
- a wet nonwoven fabric containing fibrillated regenerated cellulose fibers is pressure-compressed in the thickness direction by pressure adjusting processing or the like. By carrying out like this, it can be set as the nonwoven fabric whose A value is 90% or more. Fibers that can be fibrillated are refined by applying a shearing force in water (treating), and forming a nonwoven fabric from the refined fibers improves the denseness of the sheet.
- the internal structure of the fiber is composed of a cellulose crystalline part and an amorphous part, and the crystalline part is bonded to each other through the amorphous part to constitute a fiber.
- this fiber When beating this fiber, the amorphous part is destroyed, the crystalline part is peeled off from the fiber, and fibrils having a diameter of 1 ⁇ m or less are generated.
- the separator constituted by the fibrillated regenerated cellulose fiber becomes a very dense sheet.
- this fibril is a cellulose with a very high degree of crystallinity, so it has high rigidity, and the fibril itself is not flattened by the press in the paper making process and maintains a cross-sectional shape close to a circle.
- a paper layer is formed by entanglement of points and hydrogen bonding.
- the separator containing the fibrillated regenerated cellulose fiber has a fine paper quality, but the ion flow path is not redundant and the ion permeability is excellent.
- the content of the fibrillated regenerated cellulose fiber is less than 30% by mass, the shielding performance of the separator is lowered, the short circuit failure of the electrochemical element is increased, or the ion permeability of the separator is lowered, thereby reducing the electrochemical element.
- the resistance value increases.
- fibers other than fibrillated regenerated cellulose fibers as a raw material for the nonwoven fabric, and for example, synthetic fibers and other cellulose fibers can be used without any particular limitation.
- synthetic fibers include polyester fibers such as polyethylene terephthalate fibers, acrylic fibers such as polyacrylonitrile fibers, polyamide fibers such as nylon fibers and aramid fibers, and polyphenylene sulfide fibers.
- cellulose fibers include, for example, regenerated cellulose fibers that are not fibrillated, wood pulp such as hardwood and conifers, and non-wood pulp such as manila hemp, sisal, jute, and esparto.
- a pulping method As a pulping method, a kraft method, a sulfite method, a soda method, or the like can be used, and not only ordinary papermaking pulp but also dissolving pulp and mercerized pulp can be used. These pulps may be bleached.
- a pressure compression facility such as a calender roll or a touch roll, for example.
- the calendar roll and the touch roll may be made of resin or metal. Moreover, the structure which combined these may be sufficient. Furthermore, you may heat-process as needed in the case of pressure compression.
- Non-woven fabric is a sheet having a structure in which fibers are overlapped, and there is a space in which no fibers are present inside the sheet. In the present embodiment, this space is reduced by compressing and compressing the sheet after forming it, and the hole diameter is controlled by shortening the distance between the fibers. In addition, when the thickness of a separator becomes thin, the shielding performance of a separator often falls.
- the fibers themselves in the nonwoven fabric are also crushed and become a slightly flat shape. For this reason, the denseness of the nonwoven fabric in the thickness direction is increased, and even if it is thinned by pressure compression, the shielding property is not lowered.
- the frequency of the most frequent vacancy value of the separator is more preferably 60% or more with respect to the frequency of all sections.
- the frequency of the most frequent pore value of the separator (hereinafter referred to as “B value”) of 60% or more indicates that the pores existing in the separator are particularly concentrated on a specific diameter. If the B value is less than 60%, the variation in pore diameter cannot be reduced from a certain level.
- the mode value in the present embodiment is the mode value of the hole diameter distribution according to “TEST METHOD B of ASTM F316-03”.
- the degree of beating of the fibrillated regenerated cellulose fiber used for the separator As one means for setting the B value of the separator to 60% or more, in this embodiment, attention was paid to the degree of beating of the fibrillated regenerated cellulose fiber used for the separator.
- the freeness (CSF value) according to “JIS P8121-2” is used as an index indicating the degree of beating.
- the CSF value of the fiber used for the separator of the present embodiment is preferably in the range of 100 ml or less for the lowered CSF value and 700 ml or less for the raised CSF value.
- the lowered CSF value is larger than 100 ml, the degree of beating of the fiber is low, so the B value of the separator tends to be less than 60%, and the shielding performance cannot be improved. Further, when the increasing CSF value further exceeds 700 ml, the fibers become too fine and the fibers falling from the papermaking net during papermaking increase, so the B value tends to be less than 60%.
- the equipment used for beating the regenerated cellulose fiber used in the separator of the present embodiment may be any as long as it is used for preparing a normal papermaking raw material.
- a beater, a conical refiner, a disc refiner, a high-pressure homogenizer, or the like can be used.
- the frequency in the range of the most frequent vacancy value ⁇ 10% of the separator is 75% or more with respect to the frequency of all sections.
- the frequency in the range of the most frequent pore value ⁇ 10% of the separator (hereinafter referred to as “C value”) is 75% or more of the entire section.
- the majority of the pores existing in the separator have a specific diameter and its It shows that it is distributed in the vicinity, and the variation in the pore diameter of the separator is further reduced, so that the shielding performance can be further improved. If the C value is less than 75%, the variation in the hole diameter cannot be reduced from a certain level.
- the porosity of the separator of this embodiment is preferably 35 to 80%.
- the porosity of the separator is less than 35%, the space occupied in the nonwoven fabric is too small, the amount of electrolyte retained is reduced, and the capacity of the electrochemical device is reduced and the resistance value is increased.
- the porosity of the separator is more preferably 35 to 65%, and still more preferably 35 to 55%.
- the thickness of the separator in this embodiment is preferably 5 to 30 ⁇ m. If the thickness of the separator is less than 5 ⁇ m, the short-circuit defect rate cannot be reduced because the distance between the pair of electrodes is shortened even with the technique of the present invention. On the other hand, when the thickness exceeds 30 ⁇ m, the distance between the electrodes becomes long, and the resistance value of the electrochemical element increases.
- ⁇ Measuring method of separator properties The measured values of the separators according to Examples, Comparative Examples, and Conventional Examples described below are measured by the following methods.
- the CSF value is measured in accordance with “JIS P811-2-2 Pulp-Freeness test method-Part 2: Canadian Standard Freeness Method”.
- the porosity of the separator is obtained from Equation 1 below the porosity. (Separator's true specific gravity-separator density) / Separator's true specific gravity x 100 (%) For example, the porosity of a separator made only of cellulose having a density of 0.4 g / cm 3 is determined as follows.
- Density of the separator in an absolutely dry state is measured by a method defined in Method B of “JIS C2300-2“ Electrical Cellulose Paper—Part 2: Test Method ”7.0 A Density”.
- Method B JIS C2300-2“ Electrical Cellulose Paper—Part 2: Test Method ”7.0 A Density”.
- CFP-1200-AEXL-ESA manufactured by Porous Materials, Inc.
- TEST METHOD B of ASTM F316-03 the hole diameter is 0.01 ⁇ m and the hole diameter is 0.01 ⁇ m. The distribution was determined.
- GALWICK Porous Materials, Inc.
- the 0.015 ⁇ m holes were assigned to the 0.02 ⁇ m section, and the 0.020 ⁇ m holes were assigned to the 0.02 ⁇ m section.
- the ratio (%) of the section 0.05 to 1.00 ⁇ m was obtained out of all the sections, and was taken as the A value.
- the frequency (%) of the most frequent vacancy value in this vacancy diameter distribution was read and used as the B value. Further, the frequency (%) of the hole value interval range of the most frequent hole value ⁇ 10% was determined and used as the C value.
- the cylindrical lithium ion secondary battery was produced as follows.
- a lithium cobalt oxide electrode for a lithium ion secondary battery was used as the positive electrode material, a graphite electrode was used as the negative electrode material, and wound with a separator to obtain a lithium ion secondary battery element.
- the device is housed in a cylindrical case with a bottom, and an electrolyte solution in which lithium hexafluorophosphate is dissolved as an electrolyte is injected into a mixed solvent of ethylene carbonate and diethyl carbonate, sealed with a press machine, and rated voltage
- a cylindrical lithium ion secondary battery having a voltage of 3.7 V, a rated capacity of 3000 mAh, a diameter of 18 mm, and a height of 65 mm was produced.
- the coin-type lithium ion secondary battery was produced as follows. A lithium cobalt oxide electrode for a lithium ion secondary battery was used as the positive electrode material, a graphite electrode was used as the negative electrode material, and the separators were interposed. Next, a mixed solvent of diethyl carbonate and ethylene carbonate is impregnated with an electrolyte solution in which lithium hexafluorophosphate is dissolved as an electrolyte, and caulked and sealed, and a rated voltage of 3.6 V, a rated capacity of 30 mAh, a diameter of 20 mm, a high A coin-type lithium ion secondary battery having a thickness of 3.2 mm was produced.
- Short-circuit failure rate The short-circuit failure rate of an electrochemical device is considered as a short-circuit failure when the charging voltage does not increase to the rated voltage, and the number of electrochemical devices that have had these short-circuit failures is the electric capacity used for capacitance measurement. Dividing by the number of chemical elements, the percentage of short-circuit failure was taken as a percentage.
- Overcharge test failure rate The test was performed on coin-type and cylindrical lithium ion secondary batteries, and the overcharge test failure rate was used as an indicator of the shielding property of the separator. This test was carried out in order to quantify the difference in the shielding properties of the separator, which does not show a difference in a normal short circuit defect test. Specifically, when the manufactured lithium ion secondary battery was charged at a constant current up to 5.0 V at a rate of 1.0 C at 60 ° C., the case where the charging voltage did not increase to the rated voltage was regarded as defective. Then, the number of electrochemical elements that were defective was divided by the number of electrochemical elements subjected to capacitance measurement, and the percentage was used as the overcharge test defect rate.
- the internal resistance of the lithium ion secondary battery is defined in “8.6 C-8715-1“ Industrial Lithium Secondary Battery Cell and Battery System-Part 1: Performance Requirements ””. .3 AC internal resistance ”.
- the internal resistance of the electric double layer capacitor is measured by the alternating current (ac) resistance method of “4.6 Internal Resistance” specified in “JIS C 5160-1“ Fixed Electric Double Layer Capacitor for Electronic Equipment ””. did.
- the impedance of the aluminum electrolytic capacitor was measured using an LCR meter at a frequency of 20 ° C. and 100 kHz.
- Discharge Capacity The discharge capacity of the lithium ion secondary battery is defined in “8.4 C. JIS C 8715-1“ Industrial Lithium Secondary Battery Cell and Battery System—Part 1: Performance Requirements ””. .1 Discharge performance test ".
- the capacitance of the electrostatic double layer capacitor is obtained by the constant current discharge method of “4.5 Capacitance” specified in “JIS C 5160-1“ Fixed Electric Double Layer Capacitor for Electronic Equipment ””. It was.
- the capacitance of the aluminum electrolytic capacitor was measured using an LCR meter at 20 ° C. and a frequency of 100 Hz.
- Example 1 100% by mass of solvent-spun cellulose fiber (specifically, lyocell (registered trademark) fiber), which is a regenerated cellulose fiber, was beaten to obtain a raw material having a CSF value of 100 ml. After making this raw material with a long paper machine, the thickness was adjusted at a linear pressure of 0.5 kN / cm using a resin roll and a metal roll to obtain a separator having a thickness of 20 ⁇ m and a density of 0.35 g / cm 3 . .
- the separator of Example 1 had a porosity of 76.7%, an A value of 90.5%, a modest pore value of 0.70 ⁇ m, a B value of 64.9%, and a C value of 76.8%.
- Example 2 30% by mass of solvent-spun cellulose fiber and 70% by mass of hardwood dissolving pulp (LDP) were mixed and beaten to obtain a raw material having a CSF value of 0 ml. After making this raw material with a long paper machine, the thickness was adjusted at a linear pressure of 1.0 kN / cm using a resin roll and a metal roll to obtain a separator having a thickness of 30 ⁇ m and a density of 0.50 g / cm 3 . .
- the separator of Example 2 had a porosity of 66.7%, an A value of 100%, a modest hole value of 0.40 ⁇ m, a B value of 70.2%, and a C value of 78.5%.
- [Conventional example 1] A commercially available microporous membrane made of polyethylene having a thickness of 25 ⁇ m and a porosity of 36.8% was used as the separator of Conventional Example 1. The separator had an A value of 21.6%, a modest hole value of 0.03 ⁇ m, a B value of 88.0%, and a C value of 96.6%.
- Example 3 A raw material having a rising CSF value of 350 ml was obtained by beating the solvent-spun cellulose fiber.
- the thickness was adjusted with a resin roll and a metal roll at a linear pressure of 5.5 kN / cm to obtain a separator having a thickness of 5 ⁇ m and a density of 0.70 g / cm 3 . .
- the separator had a porosity of 53.3%, an A value of 100.0%, a modest hole value of 0.45 ⁇ m, a B value of 79.0%, and a C value of 91.0%.
- Example 4 85% by mass of solvent-spun cellulose fiber having a rising CSF value of 650 ml and 15% by mass of polyethylene terephthalate fiber (PET fiber) were mixed to obtain a papermaking raw material. After making this raw material with a long paper machine, a thickness of 15 ⁇ m and a density of 0.85 g / cm 3 were obtained by using a metal roll and a metal roll to adjust the thickness at a linear pressure of 7.5 kN / cm. . The separator had a porosity of 39.2%, an A value of 100.0%, a modest pore value of 0.28 ⁇ m, a B value of 78.9%, and a C value of 93.5%.
- Example 3 Using the same raw material as in Example 3, the paper was made with a long paper machine, and then the thickness was adjusted using a metal roll and a metal roll at a linear pressure of 7.0 kN / cm. The thickness was 3 ⁇ m and the density was 0.90 g / A cm 3 separator was obtained. The separator had a porosity of 37.8%, an A value of 100.0%, a modest hole value of 0.47 ⁇ m, a B value of 60.6%, and a C value of 92.2%.
- Alumina powder was applied and dried on a microporous membrane made of polyethylene having a thickness of 25 ⁇ m and a porosity of 32.0% to obtain a separator having a thickness of 30 ⁇ m and a porosity of 57.6%.
- the separator had an A value of 5.0%, a modest hole value of 0.02 ⁇ m, a B value of 91.7%, and a C value of 98.0%.
- Example 1 Using the separators obtained in Example 1 and Example 2, Reference Example 1 and Reference Example 2, Comparative Example 1 and Comparative Example 2, and Conventional Example 1, rated voltage 3.6 V, rated capacity 30 mAh, diameter 20 mm, high A 3.2 mm coin-type lithium ion secondary battery and an aluminum electrolytic capacitor having a rated voltage of 63 V, a rated capacity of 120 ⁇ F, a diameter of 10 mm, and a height of 20 mm were prepared and evaluated.
- Table 1 shows the physical properties of these separators and the evaluation results of lithium ion secondary batteries and aluminum electrolytic capacitors produced using the separators.
- Example 3 and Example 4 Comparative Example 3 and Comparative Example 4, and Conventional Example 2
- cylindrical lithium having a rated voltage of 3.7 V, a rated capacity of 3000 mAh, a diameter of 18 mm, and a height of 65 mm
- Table 2 shows the physical properties of these separators and the evaluation results of lithium ion secondary batteries and electric double layer capacitors produced using the separators.
- the separators of Examples 1 and 2 have a thickness of 20 to 30 ⁇ m, an A value of 90% or more, a B value of 60% or more, a C value of 75% or more, and a porosity of 35 to 80%. It is in the range.
- the lithium ion secondary battery and the aluminum electrolytic capacitor produced using the separators of Examples 1 and 2 have no short circuit defects. Also, the internal resistance value is sufficiently smaller than that of the conventional example.
- the lithium ion secondary batteries of Reference Example 1 and Reference Example 2 have no occurrence of short circuit defects, and the internal resistance is sufficiently lower than that of the conventional example.
- the defective rate in the overcharge test is 0.3% or more, which is slightly higher than those in Example 1 and Example 2. This is probably because the B value of the separator is 55.1% in Reference Example 1 and the C value of the separator is 73.0% in Reference Example 2. From Example 1 and Example 2, Reference Example 1 and Reference Example 2, it can be seen that the B value of the separator is preferably 60% or more and the C value is preferably 75% or more.
- the A value of the separator of Comparative Example 1 is 75.0%. And in the lithium ion secondary battery and aluminum electrolytic capacitor which used the separator of the comparative example 1, the short circuit defect has generate
- the separator of Comparative Example 2 has a higher porosity than the separators of Example 1 and Example 2. However, the internal resistance value of the lithium ion secondary battery using the separator of Comparative Example 2 is 10% or more larger than each Example. This is because the thickness of the separator of Comparative Example 2 is as thick as 40 ⁇ m. From Examples 1 and 2, and Comparative Example 2, it can be seen that the thickness of the separator is preferably 30 ⁇ m or less.
- the separators of Examples 3 and 4 have a thickness of 5 to 15 ⁇ m, an A value of 90% or more, a B value of 60% or more, a C value of 75% or more, and a porosity of 35 to 80%. It is in.
- the lithium ion secondary battery and the electric double layer capacitor produced using the separators of Example 3 and Example 4 do not have a short circuit defect. Also, the internal resistance value is sufficiently smaller than that of the conventional example.
- the separator of Comparative Example 3 is a separator whose thickness is adjusted to 3 ⁇ m using the same raw material as in Example 3, and the separator of Comparative Example 3 has a low porosity. Nevertheless, the lithium ion secondary battery using the separator of Comparative Example 3 has a short circuit defect. From this, it is understood that a short circuit failure may occur when the thickness of the separator is less than 5 ⁇ m.
- the separator of Comparative Example 4 has a low porosity of 30.0%. For this reason, the internal resistance value of the lithium ion secondary battery using the separator of Comparative Example 4 is 20% or more larger than that of the battery using the separator of Example 3 having the same thickness. Moreover, it is 10% or more larger than the resistance value of the lithium ion secondary battery using the separator of Example 4 which is thicker than Comparative Example 4. From Examples 3 and 4 and Comparative Example 4, it can be seen that the porosity of the separator is preferably 35% or more.
- the separator of the present embodiment uses cellulose fibers that are excellent in heat resistance in any of the above-described examples, and the heat resistance of the electrochemical device is increased compared with the conventional microporous membrane made of polyethylene, and its safety. Can be expected to improve.
- examples of the electrochemical element to which the separator according to the embodiment of the present invention can be applied include a lithium ion secondary battery, an electric double layer capacitor, and an aluminum electrolytic capacitor, and electrode materials and electrolytic solution materials used for them.
- the other members and the like do not need to be specifically limited, and various materials can be used.
- the separator for an electrochemical element according to the embodiment of the present invention can be applied to an electrochemical element such as a lithium ion capacitor or a lithium primary battery in addition to the above-described electrochemical element.
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Abstract
Description
例えば、電気自動車やハイブリッド自動車では電源等としてリチウムイオン二次電池が、エネルギー回生等には電気二重層キャパシタが、燃料噴霧や変速機、電子スロットル、アンチロックブレーキシステム等の電子制御ユニット(ECU)及びモーター制御や電池制御、ハイブリッド電気自動車(HEV)システム制御、外部交流電源からの直流変換にはアルミニウム電解コンデンサや電気二重層キャパシタが用いられたりしている。
こういった電気化学素子では、ショート不良が直ちに事故に結びつくおそれがあるため、高い信頼性が求められる。
また、特許文献2に記載されたセパレータは、素材がポリオレフィン系樹脂であり、電解液に対する濡れ性が低く、電解液を十分に保持できず、抵抗値が増大してしまうという問題が解決できない。
しかしながら、近年求められる高容量、高出力の電気化学素子では、流れる電流値も大きいので、前記した空孔の閉塞により電流を遮断しても、電池内の発熱をおさえることが出来ず、セパレータ全体が溶融(メルトダウン)し、内部短絡して熱暴走を引き起こす可能性があった。
本発明は、上記課題に鑑みてなされたもので、従来のセパレータで困難であった十分な遮蔽性と薄葉化を両立したセパレータ及び、該セパレータを用いた電気化学素子を提供することを目的として成されたものである。
即ち、一対の電極間に介在し、繊維をシート状に堆積させて形成した不織布から成り電解液を保持する電気化学素子用セパレータであって、前記不織布の空孔径0.05~1.00μmの頻度が、全空孔の90%以上であることを特徴とする。
また例えば前記不織布を形成する繊維は再生セルロース繊維を含むことを特徴とする。
最初に、本発明を実施するための形態に係る電気化学素子用のセパレータについて説明する。電気化学素子としては、例えばアルミ電解コンデンサ、電気二重層キャパシタ、リチウムイオンキャパシタ、リチウム一次電池、リチウムイオン二次電池等が好適である。
また、「最頻空孔値」とは、「ASTM F316-03の『TEST METHOD B』」に規定された方法で測定した空孔の空孔径分布の最頻値である。
電気化学素子のショート不良率低減のためには、セパレータの遮蔽性が重要である。そして、セパレータの遮蔽性能を向上させるには、空孔径を小さくすることが重要である。
しかし、本願発明者らは、セパレータの空孔径を小さくするのみでは、遮蔽性能を一定のレベルから改善できないことを見出した。
電気化学素子、例えばリチウムイオン二次電池では、負極のリチウムイオンの濃度が高まると、リチウムが針状結晶(デンドライト)として析出する。そしてこのデンドライトは、セパレータの空孔中を徐々に成長していき、両電極を接触させ、ショートにいたる。
また、例えばキャパシタにおいても、セパレータの空孔が大きい箇所は、相対的に抵抗値が小さくなるため、この空孔が大きい箇所を通して落雷するようにしてショート不良にいたると考えられる。
本実施の一形態例のセパレータは、繊維をシート状に堆積させて形成した不織布構造であり、その不織布の形成方法として、例えば、以下の方法が挙げられる。
フィブリル化が可能な繊維は、水中でせん断力を加えて処理(叩解)することで微細化され、この微細化された繊維から不織布を形成することで、シートの緻密性が向上する。
なお、本実施の形態例における最頻空孔値とは、「ASTM F316-03の『TEST METHOD B』」による空孔径分布の最頻値である。
以下に説明する実施例、比較例および従来例にかかるセパレータの各測定値は、次の方法で測定している。
CSF値
「JIS P8121-2 パルプ-ろ水度試験法-第2部:カナダ標準ろ水度法」に従い測定している。
「JIS C2300-2 『電気用セルロース紙-第2部:試験方法』 5.1 厚さ」に規定された、「5.1.1 測定器及び測定方法」における「a) 外側マイクロメータを用いる場合」のマイクロメータを用いて、「5.1.3 紙を折り重ねて厚さを測る場合」の10枚に折り重ねる方法でセパレータの厚さを測定している。
以下の式1により、セパレータの空隙率を求めている。
(セパレータの真比重-セパレータ密度)/セパレータの真比重×100(%) …… 式1
例えば、密度0.4g/cm3のセルロースのみからなるセパレータの空隙率は、以下のようにして求める。
また例えば、比重1.2の合成繊維を30質量%、比重1.5のセルロース繊維を70質量%含有する密度0.45g/cm3のセパレータでは、セパレータの比重は、1.5×0.7+1.2×0.3= 1.41となる。そして、上記式1にあてはめると、セパレータの空隙率は、(1.41-0.45)/1.41×100=68.1(%)となる。
「JIS C2300-2 『電気用セルロース紙-第2部:試験方法』 7.0A 密度」のB法に規定された方法で、絶乾状態のセパレータの密度を測定している。
A値、B値、及びC値
CFP-1200-AEXL-ESA(Porous Materials,Inc.製)を用いて、「ASTM F316-03の『TEST METHOD B』」により、区間幅0.01μmで空孔径分布を求めた。試験液としてGALWICK(Porous Materials,Inc.製)を用いている。
この空孔径分布を用いて、全区間のうち、区間0.05~1.00μmの比率(%)を求め、A値とした。そして、この空孔径分布の最頻空孔値の頻度(%)を読み取り、B値とした。更に、この最頻空孔値±10%の空孔値区間範囲の頻度(%)を求め、C値とした。
以下、本実施の形態例のセパレータを用いたリチウムイオン二次電池の製作方法を説明する。具体的には、リチウムイオン二次電池として、円筒形リチウムイオン二次電池及びコイン型リチウム二次電池の2種類を作製した。
正極材として、リチウムイオン二次電池用のコバルト酸リチウム電極を用い、負極材としてグラファイト電極を用い、セパレータと共に捲回し、リチウムイオン二次電池素子を得た。その素子を有底円筒状のケース内に収納し、エチレンカーボネートとジエチルカーボネートの混合溶媒に、電解質として六フッ化リン酸リチウムを溶解した電解液を注入し、プレス機で封口して、定格電圧3.7V、定格容量3000mAh、直径18mm、高さ65mmの円筒型リチウムイオン二次電池を作製した。
正極材として、リチウムイオン二次電池用のコバルト酸リチウム電極を用い、負極材としてグラファイト電極を用い、セパレータを介在させて積層した。次に、ジエチルカーボネートとエチレンカーボネートとの混合溶媒に、電解質として六フッ化リン酸リチウムを溶解した電解液を含浸させ、かしめ封口して、定格電圧3.6V、定格容量30mAh、直径20mm、高さ3.2mmのコイン型リチウムイオン二次電池を作製した。
以下、本実施の形態例のセパレータを用いた電気二重層キャパシタの製作方法を説明する。
活性炭電極と、本実施の形態例のセパレータとを交互に折り重ね、電気二重層キャパシタ素子を得た。その素子をアルミニウムケースに収納し、アセトニトリルにトリエチルメチルアンモニウムヘキサフルオロホスフェイトを溶解した電解液を注入し、真空含浸を行った後に密封して、定格電圧2.5V、定格容量3000F、サイズ55×55×155mm(W×D×L)の電気二重層キャパシタを作製した。
以下、本実施の形態例のセパレータを用いたアルミニウム電解コンデンサの製作方法を説明する。
エッチング処理および酸化皮膜形成処理を行った陽極アルミ箔と陰極アルミ箔とを、セパレータを介在させて捲回してコンデンサ素子を得た。このコンデンサ素子に電解液を含浸させ、ケースに入れた後に封口して、直径10mm、高さ20mm、定格電圧63V、定格容量120μFのアルミニウム電解コンデンサを作製した。なお、コンデンサ素子を作製する際の陽極アルミニウム箔の長さは一定とした。
本実施の形態例の電気化学素子は、上記の各例につき1000個作製し、以下の特性評価に用いた。特性評価は、以下の条件及び方法で行った。
ショート不良率
電気化学素子のショート不良率は、定格電圧まで充電電圧が上がらなかった場合をショート不良とみなし、これらのショート不良となった電気化学素子の個数を、静電容量測定に供した電気化学素子数で除して、百分率をもってショート不良率とした。
コイン型及び円筒型のリチウムイオン二次電池について実施し、過充電試験不良率を、セパレータの遮蔽性の指標とした。本試験は、通常のショート不良試験では差が現れないようなセパレータの遮蔽性の違いを数値化するために行ったものである。
具体的には、作製したリチウムイオン二次電池を60℃にて1.0Cレートで5.0Vまで定電流充電した際に、定格電圧まで充電電圧が上がらなかった場合を不良とみなした。そして、これらの不良となった電気化学素子の個数を、静電容量測定に供した電気化学素子数で除して、百分率をもって過充電試験不良率とした。
リチウムイオン二次電池の内部抵抗は、「JIS C 8715-1 『産業用リチウム二次電池の単電池及び電池システム-第一部:性能要求事項』」に規定された、「8.6.3 交流内部抵抗」に従い測定した。
電気二重層キャパシタの内部抵抗は、「JIS C 5160-1 『電子機器用固定電気二重層コンデンサ』」に規定された、「4.6 内部抵抗」の交流(a.c.)抵抗法により測定した。
アルミニウム電解コンデンサのインピーダンスは、20℃、100kHzの周波数でLCRメータを用いて測定した。
放電容量
リチウムイオン二次電池の放電容量は、「JIS C 8715-1 『産業用リチウム二次電池の単電池及び電池システム-第一部:性能要求事項』」に規定された、「8.4.1 放電性能試験」に従い測定した。
電気二重層キャパシタの静電容量は、「JIS C 5160-1 『電子機器用固定電気二重層コンデンサ』」に規定された、「4.5 静電容量」の定電流放電法により求めた。
アルミニウム電解コンデンサの静電容量は、20℃、100Hzの周波数でLCRメータを用いて測定した。
再生セルロース繊維である溶剤紡糸セルロース繊維(具体的にはリヨセル(登録商標)繊維を用いる。)100質量%を叩解し、CSF値100mlの原料を得た。この原料を長網抄紙機で抄紙した後、樹脂ロールと金属ロールとを用いて線圧0.5kN/cmで調厚処理し、厚さ20μm、密度0.35g/cm3のセパレータを得た。この実施例1のセパレータの空隙率は76.7%、A値は90.5%、最頻空孔値0.70μm、B値64.9%、C値76.8%であった。
溶剤紡糸セルロース繊維を30質量%と、広葉樹溶解パルプ(LDP)70質量%とを混合叩解し、CSF値0mlの原料を得た。この原料を長網抄紙機で抄紙した後、樹脂ロールと金属ロールとを用いて線圧1.0kN/cmで調厚処理し、厚さ30μm、密度0.50g/cm3のセパレータを得た。この実施例2のセパレータの空隙率は66.7%、A値は100%、最頻空孔値0.40μm、B値70.2%、C値78.5%であった。
溶剤紡糸セルロース繊維を叩解してCSF値150mlの原料を得た。この原料を長網抄紙機で抄紙した後、樹脂ロールと金属ロールとを用いて線圧4.0kN/cmで調厚処理し、厚さ30μm、密度0.60g/cm3のセパレータを得た。このセパレータの空隙率は60.0%、A値92.0%、最頻空孔値0.51μm、B値55.1%、C値89.0%であった。
溶剤紡糸セルロース繊維を叩解してCSF値75mlの原料を得た。この原料を長網抄紙機でシート形成した後、樹脂製タッチロールを用いて線圧0.3kN/cmで加圧圧縮し、厚さ25μm、密度0.27g/cm3のセパレータを得た。このセパレータの空隙率は82.0%、A値92.0%、最頻空孔値0.82μm、B値62.3%、C値73.0%であった。
溶剤紡糸セルロース繊維を叩解して上昇しているCSF値680mlの原料を得た。この原料を長網抄紙機でシート形成した後、樹脂製タッチロールを用いて線圧0.2kN/cmで加圧圧縮し、厚さ30μm、密度0.65g/cm3のセパレータを得た。このセパレータの空隙率は56.7%、A値75.0%、最頻空孔値0.71μm、B値67.3%、C値76.6%であった。
溶剤紡糸セルロース繊維を叩解してCSF値0mlの原料を得た。この原料を長網抄紙機で抄紙した後、樹脂ロールと金属ロールとを用いて線圧0.3kN/cmで調厚処理し、厚さ40μm、密度0.33g/cm3のセパレータを得た。このセパレータの空隙率は78.0%、A値97.7%、最頻空孔値0.42μm、B値71.1%、C値85.4%であった。
厚さ25μm、空隙率36.8%のポリエチレン製の市販の微多孔膜を従来例1のセパレータとした。このセパレータのA値は21.6%、最頻空孔値0.03μm、B値88.0%、C値96.6%であった。
[実施例3]
溶剤紡糸セルロース繊維を叩解して上昇しているCSF値350mlの原料を得た。この原料を長網抄紙機で抄紙した後、樹脂ロールと金属ロールとを用いて線圧5.5kN/cmで調厚処理し、厚さ5μm、密度0.70g/cm3のセパレータを得た。このセパレータの空隙率は53.3%、A値100.0%、最頻空孔値0.45μm、B値79.0%、C値91.0%であった。
上昇しているCSF値650mlの溶剤紡糸セルロース繊維85質量%と、ポリエチレンテレフタレート繊維(PET繊維)15質量%とを混合し、抄紙原料を得た。この原料を長網抄紙機で抄紙した後、金属ロールと金属ロールとを用いて線圧7.5kN/cmで調厚処理し、厚さ15μm、密度0.85g/cm3のセパレータを得た。このセパレータの空隙率は39.2%、A値100.0%、最頻空孔値0.28μm、B値78.9%、C値93.5%であった。
実施例3と同じ原料を用いて、長網抄紙機で抄紙した後、金属ロールと金属ロールとを用いて線圧7.0kN/cmで調厚処理し、厚さ3μm、密度0.90g/cm3のセパレータを得た。このセパレータの空隙率は37.8%、A値100.0%、最頻空孔値0.47μm、B値60.6%、C値92.2%であった。
溶剤紡糸セルロース繊維を叩解して上昇しているCSF値500mlの原料を得た。この原料を長網抄紙機で抄紙した後、金属ロールと金属ロールとを用いて線圧8.0kN/cmで調厚処理し、厚さ5μm、密度1.05g/cm3のセパレータを得た。このセパレータの空隙率は30.0%、A値95.7%、最頻空孔値0.21μm、B値88.8%、C値95.7%であった。
厚さ25μm、空隙率32.0%のポリエチレン製の微多孔膜に、アルミナ粉末を塗布乾燥し、厚さ30μm、空隙率57.6%のセパレータを得た。このセパレータのA値は5.0%、最頻空孔値0.02μm、B値91.7%、C値98.0%であった。
これらのセパレータの諸物性、そのセパレータを用いて作製したリチウムイオン二次電池及びアルミニウム電解コンデンサの評価結果を、表1に示す。
実施例1及び実施例2のセパレータは厚さが20~30μm、A値が90%以上であり、またB値が60%以上、C値が75%以上であり、空隙率が35~80%の範囲にある。これら実施例1及び実施例2のセパレータを用いて作製したリチウムイオン二次電池及びアルミニウム電解コンデンサは、ショート不良の発生がない。また、内部抵抗値も従来例と比べ十分に小さい値である。
実施例1及び実施例2、参考例1及び参考例2から、セパレータのB値は60%以上、C値は75%以上が好ましいとわかる。
Claims (8)
- 一対の電極間に介在し、繊維をシート状に堆積させて形成した不織布からなり電解液を保持する電気化学素子用セパレータであって、
前記不織布の空孔径0.05~1.00μmの頻度が、全空孔の90%以上であることを特徴とする電気化学素子用セパレータ。 - 前記不織布の最頻空孔値の頻度が、全区間の頻度に対して60%以上であることを特徴とする請求項1に記載の電気化学素子用セパレータ。
- 前記不織布の最頻空孔値±10%の範囲の頻度が、全区間の頻度に対して75%以上であることを特徴とする請求項1または請求項2に記載の電気化学素子用セパレータ。
- 前記不織布の空隙率が35~80%であることを特徴とする請求項1から請求項3のいずれか1項に記載の電気化学素子用セパレータ。
- 前記不織布の厚さが5~30μmであることを特徴とする請求項1から請求項4のいずれか1項に記載の電気化学素子用セパレータ。
- 前記不織布を形成する繊維は再生セルロース繊維を含むことを特徴とする請求項1から請求項5のいずれか1項に記載の電気化学素子用セパレータ。
- 請求項1から請求項6のいずれか1項に記載の電気化学素子用セパレータを用いたことを特徴とする電気化学素子。
- 当該電気化学素子は、アルミニウム電解コンデンサ、電気二重層キャパシタ、リチウムイオンキャパシタ、リチウム一次電池、リチウムイオン二次電池のいずれかであることを特徴とする請求項7に記載の電気化学素子。
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