WO2015145522A1 - Electrode active material for non-aqueous electrolyte cell, electrode for non-aqueous electrolyte secondary cell, non-aqueous electrolyte secondary cell, and cell pack - Google Patents

Electrode active material for non-aqueous electrolyte cell, electrode for non-aqueous electrolyte secondary cell, non-aqueous electrolyte secondary cell, and cell pack Download PDF

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WO2015145522A1
WO2015145522A1 PCT/JP2014/057972 JP2014057972W WO2015145522A1 WO 2015145522 A1 WO2015145522 A1 WO 2015145522A1 JP 2014057972 W JP2014057972 W JP 2014057972W WO 2015145522 A1 WO2015145522 A1 WO 2015145522A1
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aqueous electrolyte
active material
electrode
silicon
particles
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PCT/JP2014/057972
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French (fr)
Japanese (ja)
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深澤孝幸
越崎健司
森田朋和
久保木貴志
吉尾紗良
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株式会社 東芝
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Priority to PCT/JP2014/057972 priority Critical patent/WO2015145522A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/134—Electrodes based on metals, Si or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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 embodiment relates to an electrode active material for a non-aqueous electrolyte battery, an electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and a battery pack.
  • silicon can store lithium atoms at a ratio of 4.4 to 1 silicon atom, and theoretically can have a capacity about 10 times that of a graphitic carbon material.
  • silicon particles expand lithium by about three to four times in volume, the particles themselves are broken and pulverized by repeated charge and discharge, and other members that constitute the electrode are affected, etc. I have a problem. Therefore, it has been proposed that the size of the silicon particles be reduced and that the periphery of the particles be covered with silicon oxide so that aggregation is less likely to occur.
  • nanosized silicon particles can be deposited in and on the silicon oxide by heating the silicon oxide to disproportionate treatment.
  • silicon particles are immobilized on the silicon oxide, and grain growth and detachment of the silicon particles can be prevented.
  • silicon oxide particles themselves do not have electron conductivity, and silicon particles react when they are in direct contact with the electrolytic solution to form a film, or they dissolve in the presence of a fluorine component, resulting in a decrease in capacity or Charge and discharge efficiency is reduced.
  • An object of the present invention is to provide an electrode active material for a non-aqueous electrolyte battery which is excellent in cycle characteristics.
  • the electrode active material for a non-aqueous electrolyte battery is a particle containing at least a silicon oxide having silicon particles inside, and the surface layer of the particle contains at least one selected from silicon carbide, silicon nitride and silicon oxynitride.
  • the particles are supported.
  • the state of deterioration of the electrode using the silicon oxide coated with the carbonaceous material as the active material was analyzed in detail. As a result, voids and cracks were formed in the carbonaceous material phase by repeated charge and discharge, and the electrolyte penetrated there. It was revealed that the conductive path is gradually divided by forming a film and further connecting and expanding these air gaps.
  • silicon particles generated by disproportionation reaction of silicon oxide the presence of silicon particles mainly located on the surface portion of silicon oxide was considered.
  • the silicon particles located on this surface portion will cause great stress on the surrounding carbon material due to expansion and contraction.
  • SiOx silicon carbide
  • SiOx particles it is preferable to use SiOx particles as fine as possible, and it is not easy to coat a uniform silicon carbide film on fine SiOx particles, and there is a problem that cost increases. is there.
  • silicon particles located on at least the surface portion of silicon oxide particles of a silicon / silicon oxide composite obtained by disproportionation of silicon oxide are silicon carbide or silicon nitride, Alternatively, it has been found that conversion to silicon oxynitride can relieve stress on the carbon material covering them and improve cycle characteristics.
  • a heat-degradable organic substance is added and heat treated to form a void outside the complexed active material, thereby alleviating the volume expansion. It has been found that the generation of wrinkles on the current collector can be effectively suppressed. Embodiments will be described below with reference to the drawings.
  • the electrode active material for a non-aqueous electrolyte battery is a particle containing at least a silicon oxide having silicon particles inside, and the surface layer of the particle contains at least one selected from silicon carbide, silicon nitride and silicon oxynitride.
  • the particles are supported.
  • the structural schematic diagram of the cross section of the active material which concerns on embodiment is shown in FIG.
  • the active material 10 of FIG. 1 has silicon nanoparticles 11, silicon oxide particles 12, and particles 13 which are not alloyed with lithium. It is preferable that the particles 13 not to be alloyed with lithium be granular, not a film or the like.
  • the silicon nanoparticles 11 and the silicon oxide particles 12 may contain trace elements such as phosphorus and boron inside thereof.
  • the active material 10 of the embodiment is used, for example, for an electrode of a non-aqueous electrolyte battery.
  • the silicon nanoparticles 11 have an ability to insert and extract lithium.
  • the silicon nanoparticles 11 are obtained by depositing a part of silicon in the silicon oxide as crystalline particles by heat treatment (disproportionation reaction) of the silicon oxide.
  • the silicon nanoparticles 11 change in volume each time lithium is repeatedly stored and released. This volume change may cause the collapse of the active material. Therefore, it is preferable to make the size as fine as possible.
  • the average diameter of the silicon nanoparticles 11 is preferably 2 nm or more and 150 nm or less. If the particle size is smaller than 2 nm, the production is substantially difficult. If the particle size is larger than 150 nm, the particles themselves may be pulverized due to repeated charge and discharge.
  • silicon nanoparticles 11 have a structure coated with silicon oxide 12 around as shown in FIG.
  • particles 13 which are not alloyed with lithium located on the surface portion of the silicon oxide particles 12 are, as the name suggests, inert to lithium, do not contribute to the reaction during charge-discharge reaction, and volume expansion is also I do not wake up.
  • the silicon oxide particles 12 contain silicon nanoparticles 11 therein.
  • the silicon oxide particles 12 are mostly amorphous silicon oxides, and are represented by the composition formula SiO x (0 ⁇ x ⁇ 2).
  • the average primary particle size of the silicon oxide particles 12 is preferably in the range of 0.1 ⁇ m to 10 ⁇ m. When the cycle characteristics are considered, when the average primary particle diameter is in this range, there is no significant deterioration, and stable charge and discharge characteristics can be obtained.
  • the average primary particle size refers to ion milling of the electrode cross section, or a scanning electron microscope (SEM: scanning electron microscope) or a transmission electron microscope (TEM: transmission electron microscopy) of the powder of the silicon oxide particles 12
  • SEM scanning electron microscope
  • TEM transmission electron microscope
  • the particle size refers to the average value of the major axis and minor axis of one particle in a two-dimensional image.
  • the method of measuring the average diameter (particle diameter) of the silicon nanoparticles 11 is the same as the method of measuring the average primary particle diameter of the silicon oxide particles 12.
  • the silicon oxide particles 12 may contain a crystalline silicon oxide phase.
  • the silicon oxide particles 12 may contain a lithium silicate phase in addition to the silicon oxide.
  • silicon oxide 12 is amorphous, so lithium enters during charging and has a relaxation ability even if it expands in volume. In addition, it is possible to prevent the growth and detachment of silicon nanoparticles in charge and discharge cycles. Furthermore, the silicon oxide particles 12 react with lithium ions during charging to form a phase containing lithium silicate, and have a feature of becoming a good ion conductor.
  • the particles 13 which are not alloyed with lithium are at least one selected from crystalline silicon carbide, crystalline silicon nitride, and crystalline silicon oxynitride. Crystalline silicon carbide, crystalline silicon nitride and crystalline silicon oxynitride are used singly or as a mixture, respectively.
  • the particles 13 which are not alloyed with lithium are not in the form of a film but are granular, and are supported on the surface of the silicon oxide particles 12 and present.
  • the particles 13 not alloyed with lithium do not cover the entire surface of the silicon oxide particles 12. At least a part of the particles 13 not alloyed with lithium is partially buried in the surface layer of the silicon oxide particles 12 and exists.
  • the term “embedding” as used herein refers to a state in which at least a part of the particles 13 which are not alloyed with lithium intrudes into the inner side of the silicon oxide particles 12, for example, as shown in FIG.
  • the particles 13 which are not alloyed with lithium have a silicon carbide composition, they have electrical conductivity, which helps to maintain the formation of a conductive path with the carbon material.
  • the temperature is raised to 1100 ° C. or more and 1400 ° C. or less, and the silicon particles deposited on the surface portion are reacted with nitrogen gas.
  • silicon nanoparticles particularly located on the surface can be changed to silicon nitride or silicon oxynitride.
  • silicon oxynitride is likely to be formed because of the presence of a trace amount of oxygen, the presence of silicon oxide nearby, and the like.
  • the heat treatment time is not particularly limited, but in order to cause a sufficient reaction, a range of 10 minutes to 12 hours is preferable.
  • silicon carbide as particles 13 which are not alloyed with lithium it can be produced by coating a carbon material on silicon oxide particles as a raw material and heat treating it.
  • cover with a carbon material is not specifically limited, There exist a method of using the organic precursor carbonized by a gaseous phase method, heat processing, etc. using organic hydrocarbon gas.
  • the carbon coverage is preferably in the range of 0.1% by mass or more and 20% by mass or less after carbonization with respect to the silicon oxide particles. If the carbon coverage is less than 0.1% by mass, it is not preferable that the effect of the subsequent silicidation does not appear. In addition, when the carbon coverage exceeds 20% by mass, it is not preferable that silicon carbide particles be coated with silicon carbide because silicon carbide proceeds more than necessary.
  • the atmosphere is preferably an Ar atmosphere or a mixed atmosphere of Ar and hydrogen.
  • the heat treatment temperature is preferably 1000 ° C. or more and 1300 ° C. or less.
  • the formation of silicon carbide requires a temperature of at least 1000 ° C or more depending on the size of silicon particles etc. When heated to a temperature higher than 1300 ° C, even silicon nanoparticles inside silicon oxide are also siliconized It is preferable to carry out the heat treatment at 1300 ° C. or lower because of the possibility of
  • the active material of the second embodiment is a composite active material 20 in which the active material 10 of the first embodiment is coated with a carbonaceous material phase 21 to form a composite.
  • the cross-sectional schematic diagram of the complexing active material 20 of 2nd Embodiment is shown in FIG.
  • the composite active material 20 of FIG. 3 has a structure in which the active material 10 is enclosed in the carbonaceous material phase 21.
  • the active material complexation by the carbonaceous material 21 may be in a form in which a single active material 10 is contained, or in a form in which a plurality of active materials 10 are contained. A portion of the active material 10 may be exposed on the surface of the carbonaceous material phase 21.
  • the carbonaceous material phase 21 containing the active material 10 it is preferable to use any one or more kinds of carbonaceous materials such as graphite, hard carbon, soft carbon, amorphous carbon or acetylene black.
  • Graphite is preferable in terms of enhancing the conductivity of the active material and improving the capacity. More preferably, it is amorphous carbon.
  • the composite active material 20 may contain a carbonaceous material different from the carbonaceous material phase 21 or fine voids inside.
  • Examples of the carbonaceous material different from the carbonaceous material phase 21 include highly crystalline graphite, carbon materials such as carbon nanofibers and carbon nanotubes, and microcrystalline materials such as acetylene black.
  • gap 10 nm-10 micrometers in diameter are preferable sizes.
  • the carbonaceous material phase 21 is also a good conductive material, it greatly contributes to the improvement of charge and discharge capacity and charge and discharge efficiency.
  • carbon fibers may be included in order to prevent the retention of the structure and the aggregation of the active material 10, and the conductivity.
  • the diameter of the carbon fiber to be added is preferably 10 nm or more and 1000 nm or less.
  • the content of the carbon fiber is preferably in the range of 0.1% by mass to 8% by mass. If it exceeds 8% by mass, the specific surface area is large, so that more carbonaceous material phase is necessary to wrap it, and as a result, the silicon content is unfavorably reduced. More preferably, they are 0.5 mass% or more and 5 mass% or less.
  • lithium silicate such as Li 4 SiO 4 may be dispersed in the carbonaceous material phase 21 in the composite active material 20 or in the active material 10.
  • the lithium salt added to the carbonaceous matter can be subjected to a heat treatment to cause a solid reaction with the silicon oxide phase in the composite particles to form a lithium silicate.
  • a SiO 2 precursor and a Li compound may be added to the composite active material 20.
  • the addition of these substances into the carbonaceous material 21 strengthens the bond between the silicon oxide phase 12 and the carbonaceous material 21 and forms Li 4 SiO 4 having excellent Li ion conductivity in the silicon oxide phase. it can.
  • the SiO 2 precursor include alkoxides such as silicon ethoxide.
  • the Li compound include lithium carbonate, lithium oxide, lithium hydroxide, lithium oxalate and lithium chloride.
  • the average primary particle size of the composite active material 20 is preferably in the range of 0.1 ⁇ m to 50 ⁇ m.
  • the average primary particle size is smaller than 0.1 ⁇ m, the specific surface area is increased, and accordingly, when forming an electrode, a large amount of binder is required.
  • the average primary particle size is larger than 50 ⁇ m, an unintended space is easily formed when the electrode is formed, resulting in a decrease in capacity per volume.
  • coarse particles are an obstacle in the coating process. More preferably, it is 0.2 ⁇ m or more and 20 ⁇ m or less.
  • the particles once composited can be obtained by crushing and classification. The method is not limited to this, and it may be produced aiming at the production of 30 small particles from the beginning such as a spray dry method.
  • the method of measuring the composite active material 20 is the same as the method of measuring the average primary particle size of the silicon oxide particles 12.
  • the specific surface area of the composite active material 20 is preferably in the range of 0.5 m 2 / g to 100 m 2 / g.
  • the particle size and the specific surface area affect the rate of the insertion and desorption reaction of lithium and are considered to have a great influence on the negative electrode characteristics, but if the value is in this range, the characteristics can be exhibited stably.
  • the specific surface area is determined by the BET method (Brunauer, Emmett, Teller) by nitrogen gas adsorption.
  • the ratio of the silicon oxide phase to the carbonaceous material phase in the composite active material 20 is preferably in the range of 0.2 ⁇ silicon oxide / carbon ⁇ 2 in mass ratio of silicon oxide to carbon. Within this range, a large capacity and good cycle characteristics can be obtained as the active material.
  • composition processing Next, a method of combining the active material 10 with the carbonaceous material 21 will be described.
  • the active material 10 is mixed with a carbon material such as graphite and an organic material consisting of a carbon precursor to form a complex.
  • the mixing can be performed using a continuous ball mill, a planetary ball mill, or the like.
  • the organic material at least one of carbon materials such as graphite, coke, low-temperature fired carbon, pitch and the like, and carbon material precursors can be used.
  • carbon materials such as graphite, coke, low-temperature fired carbon, pitch and the like, and carbon material precursors.
  • pitch since what is melted by heating, such as pitch, is melted during mechanical milling and composite formation does not proceed well, it is preferable to use it by mixing with coke, graphite, etc. which does not melt.
  • the method of complexing by mixing and stirring in the liquid phase is described below.
  • the mixing and stirring process can be performed by, for example, various stirring devices, a ball mill, a bead mill device, and a combination thereof.
  • the complexation of the silicon oxide particles with the carbon precursor and the carbon material is preferably performed by liquid phase mixing in a liquid using a dispersion medium. It is for making it distribute more uniformly.
  • a dispersion medium an organic solvent, water, etc.
  • ethanol, acetone, isopropyl alcohol, methyl ethyl ketone, ethyl acetate, N-methyl pyrrolidone and the like can be mentioned.
  • the carbon precursor is preferably one that is soluble in the liquid or dispersion medium in the mixing step to be uniformly mixed with the silicon nanoparticles, and is particularly preferably a liquid and an easily polymerizable monomer or oligomer.
  • organic materials such as furan resin, xylene resin, ketone resin, amino resin, melamine resin, urea resin, aniline resin, urethane resin, polyimide resin, polyester resin, phenol resin, resole resin, sucrose and the like can be mentioned.
  • the material mixed in the liquid phase undergoes a solidification or drying process to form a carbon-coated silicon oxide particle-organic material composite.
  • the carbonization firing is performed under an inert atmosphere such as Ar.
  • a polymer in a silicon oxide particle-organic material composite or a carbon precursor such as pitch is carbonized.
  • the temperature of the carbonization and firing depends on the thermal decomposition temperature of the organic material compound to be used, but is preferably 700 ° C. or more and 1300 ° C. or less as an appropriate range. Although depending on the particle size of the silicon oxide particles, at temperatures higher than 1300 ° C., siliconization proceeds more and the capacity is reduced, which is not preferable.
  • the firing time is preferably in the range of 10 minutes to 12 hours depending on the temperature of the firing.
  • the negative electrode material according to the present embodiment can be obtained by the synthesis method as described above.
  • the product after carbonization and firing may be adjusted in particle size, specific surface area and the like using various mills, pulverizers, grinders and the like.
  • the third embodiment includes a negative electrode mixture layer 101 and a current collector 102, as shown in the cross-sectional view of FIG.
  • the negative electrode mixture layer 101 is a layer of a mixture including an active material disposed on the current collector 102.
  • the negative electrode mixture layer 101 includes a negative electrode active material 103, a conductive material 104, and a binder 105.
  • the binder 105 joins the negative electrode mixture layer 101 and the current collector.
  • the third embodiment will be described as the negative electrode, taking the active material of the first embodiment or the second embodiment as an example, but the electrode of the third embodiment may be used for the positive electrode of the battery.
  • the negative electrode mixture layer 101 is formed on one side or both sides of the current collector 102.
  • the thickness of the negative electrode mixture layer 101 is preferably in the range of 10 ⁇ m to 150 ⁇ m. Therefore, when the negative electrode current collector is supported on both sides, the total thickness of the negative electrode mixture layer 101 is in the range of 20 ⁇ m to 300 ⁇ m. A more preferable range of the thickness on one side is 10 ⁇ m or more and 100 ⁇ m or less. Within this range, the large current discharge characteristics and the cycle life are significantly improved. It is preferable that the negative electrode mixture layer 101 include a void that relieves a volume change associated with Li insertion and release of the active material contained in the negative electrode mixture layer 101.
  • the mixing ratio of the negative electrode active material 103, the conductive material 104, and the binder 105 in the negative electrode mixture layer 101 is 57% by mass to 95% by mass of the negative electrode active material 103, and 3% by mass to 20% by mass of the conductive material 104
  • the binder 105 is preferably in the range of 2% by mass to 40% by mass in order to obtain good large current discharge characteristics and cycle life.
  • the current collector 102 of the embodiment is a conductive member that bonds with the negative electrode mixture layer 101.
  • a porous conductive substrate or a non-porous conductive substrate can be used as the current collector 102.
  • These conductive substrates can be formed of, for example, copper, stainless steel or nickel.
  • the thickness of the current collector is desirably 5 ⁇ m or more and 20 ⁇ m or less. Within this range, a balance between electrode strength and weight reduction can be achieved.
  • the negative electrode active material 103 those used as an electrode active material can be used.
  • the negative electrode active material 103 for example, metals and metal oxides can be used.
  • the metal and metal oxide an element selected from the group consisting of Si, Sn, Al, In, Ga, Pb, Ti, Ni, Mg, W, Mo and Fe, an alloy containing the selected element, selection
  • it is at least one selected from oxides of selected elements and oxides containing selected elements. It is more preferable to use the active material 10 of the first embodiment or the composite active material 20 of the second embodiment.
  • the negative electrode mixture layer 101 may contain the conductive material 104.
  • the conductive material 104 acetylene black, carbon black, graphite and the like can be given.
  • the negative electrode mixture layer 101 may contain a binder 105 that binds negative electrode materials.
  • a binder 105 that binds negative electrode materials.
  • the binding agent 105 for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), polyimide, polyaramid or the like is used. be able to.
  • two or more binders may be used in combination, and the binder excellent in binding between the active materials and the binder excellent in binding between the active material and the current collector When the combination of the above, the thing with high hardness, and the thing excellent in pliability are used combining, the negative electrode excellent in the lifetime characteristic can be produced.
  • the average size of the voids is preferably 20 nm or more and 5 ⁇ m or less. When it is smaller than 20 nm, the effect of suppressing the wrinkles of the current collector 102 is small, and when it is larger than 5 ⁇ m, the conductive path is divided and the battery characteristics are deteriorated.
  • the volume of the negative electrode mixture layer 101 is preferably 5% or more and 30% or less. Note that the volume of the negative electrode mixture layer 101 also includes the volume in the negative electrode mixture layer 101. If the volume of the void is less than 5%, the effect is not sufficient, and if it is greater than 30%, the electrode characteristics such as energy density may be degraded. A more preferable void volume is 10% or more and 20% or less with respect to the volume of the negative electrode mixture layer 101.
  • the number ratio of the active material particles 103 having a diameter equivalent to the thickness of the negative electrode mixture layer 101 of the negative electrode 100 be 20% or less of the whole. If it exceeds 20%, the effect of the voids formed outside the active material particles is lost, and the formation of wrinkles formed on the current collector 102 can not be suppressed.
  • the active material particles 103 having a diameter equivalent to the thickness of the negative electrode mixture layer 101 indicate that the diameter of the active material particles 103 is 90% or more of the thickness of the negative electrode mixture layer 101.
  • the volume of the void can be determined by the following method.
  • the sizes of the active material particles and the voids can be determined by observing the cross-section processed electrode with a scanning electron microscope (SEM) at a magnification of about 2000 or more. Specifically, 20 or more air gaps present on the diagonal in the field of view can be selected and determined as the average value thereof. The air gap can be observed more clearly by combining the observation with reflected electrons and the like.
  • SEM scanning electron microscope
  • 20 or more air gaps present on the diagonal in the field of view can be selected and determined as the average value thereof.
  • the air gap can be observed more clearly by combining the observation with reflected electrons and the like.
  • gap it can measure by the mercury intrusion method using the electrode with copper foil. In the mercury intrusion method, although calculated, pore diameter distribution can be obtained.
  • the manufacturing method of the negative electrode 100 of embodiment is demonstrated.
  • a mixture containing the negative electrode active material 103, the conductive material 104, the binder 105, and the pore forming agent is made into a paste, applied onto the current collector 102, and pressed, at a temperature of 350 ° C. to 450 ° C. Heat to obtain a negative electrode.
  • voids can be formed outside the composite negative electrode active material, that is, in the negative electrode mixture layer 101.
  • a mixture containing the negative electrode active material 103, the conductive material 104, the binder 105, and the pore forming agent is formed into a pellet to form a negative electrode mixture layer 101, which is used as a current collector 102. It may be made by forming on top.
  • the voids are formed by using a pyrolyzable organic substance as a pore forming agent.
  • the pore forming agent is preferably an organic substance which starts thermal decomposition at a temperature of 450 ° C. or less.
  • a thermoplastic resin or an elastomer is used as such an organic substance.
  • thermoplastic resins include polystyrene, polyethylene, polypropylene, polyisobutylene, polymethyl methacrylate, polytetrafluoroethylene, poly- ⁇ -methylstyrene, polyacetal, cellulose acetate, polyvinyl acetate, polyvinylidene chloride, polyvinyl fluoride , Polyvinyl acetate, polyvinyl alcohol and the like.
  • examples of the elastomer include styrene butadiene rubber, nitrile butadiene rubber, acrylic ester, vinyl acetate, methyl methacrylate butadiene rubber, chloroprene rubber, carboxy-modified styrene butadiene rubber, latex obtained by dispersing these in water, etc.
  • These pore forming agents are preferably added so that the volume of the voids is in the range of 5 to 30% when the volume of the negative electrode mixture layer 101 is 100%.
  • the heat treatment temperature is preferably set to a temperature higher than the thermal decomposition temperature of the organic substance which is a pore forming agent. Therefore, a preferable heat treatment temperature is 350 ° C. or more and 450 ° C. or less. After the heat treatment, it is preferable that the organic matter be thermally decomposed as much as possible, but a residue may remain.
  • the non-aqueous electrolyte secondary battery according to the fourth embodiment is housed, for example, with a separator interposed in the exterior material, the positive electrode accommodated in the exterior material, and the positive electrode spatially separated from the positive electrode in the exterior material.
  • a negative electrode and a non-aqueous electrolyte filled in the outer package are provided.
  • FIG. 5 is a schematic cross-sectional view of a flat-type non-aqueous electrolyte secondary battery 200 in which the packaging material 202 is formed of a laminate film.
  • the flat wound electrode group 201 is accommodated in an exterior material 202 formed of a laminate film in which an aluminum foil is interposed between two resin layers.
  • the flat wound electrode group 201 is laminated in the order of a negative electrode 203, a separator 204, a positive electrode 205, and a separator 204, as shown in FIG. Then, the laminate is spirally wound and formed by press molding.
  • the electrode closest to the packaging material 202 is a negative electrode, and no negative electrode mixture is formed on the negative electrode current collector on the packaging material 202 side, and only on one surface of the negative electrode current collector on the battery inner surface side It has the structure which formed the negative mix.
  • the other negative electrode 203 is configured by forming a negative electrode mixture on both sides of the negative electrode current collector.
  • the positive electrode 205 is configured by forming a positive electrode mixture on both sides of a positive electrode current collector.
  • the negative electrode terminal is electrically connected to the negative electrode current collector of the outermost negative electrode 203
  • the positive electrode terminal is electrically connected to the positive electrode current collector of the inner positive electrode 205 near the outer peripheral end of the wound electrode group 201.
  • the negative electrode terminal 206 and the positive electrode terminal 207 are extended from the opening of the package 202 to the outside.
  • a liquid non-aqueous electrolyte is injected from the opening of the bag-like exterior material 202.
  • the wound electrode group 201 and the liquid non-aqueous electrolyte are sealed by heat-sealing the opening of the package 202 with the negative electrode terminal 206 and the positive electrode terminal 207 interposed therebetween.
  • Examples of the negative electrode terminal 206 include aluminum or an aluminum alloy containing an element such as Mg, Ti, Zn, Mn, Fe, Cu, or Si.
  • the negative electrode terminal 206 is preferably made of the same material as the negative electrode current collector in order to reduce the contact resistance with the negative electrode current collector.
  • the positive electrode terminal 207 can use a material having electrical stability and conductivity in the range of 3 to 4.25 V with respect to the lithium ion metal. Specifically, an aluminum alloy containing an element such as aluminum or Mg, Ti, Zn, Mn, Fe, Cu, Si or the like can be mentioned.
  • the positive electrode terminal 207 is preferably made of the same material as the positive electrode current collector in order to reduce the contact resistance with the positive electrode current collector.
  • packaging material 202 the positive electrode 205, the electrolyte, and the separator 204, which are components of the non-aqueous electrolyte secondary battery 200, will be described in detail.
  • Exterior material 202 is formed of a laminate film having a thickness of 0.5 mm or less. Alternatively, a metal container having a thickness of 1.0 mm or less is used as the exterior material. The metal container is more preferably 0.5 mm or less in thickness.
  • the shape of the exterior material 202 can be selected from flat (thin), square, cylindrical, coin, and button.
  • the exterior material include, for example, an exterior material for a small battery loaded on a portable electronic device or the like, an exterior material for a large battery loaded on a two- or four-wheeled automobile, etc. according to the battery size.
  • the laminate film a multilayer film in which a metal layer is interposed between resin layers is used.
  • the metal layer is preferably aluminum foil or aluminum alloy foil in order to reduce the weight.
  • the resin layer for example, polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used.
  • PP polypropylene
  • PE polyethylene
  • PET polyethylene terephthalate
  • the laminated film can be molded into the shape of the exterior material by sealing by heat fusion.
  • the metal container is made of aluminum or aluminum alloy or the like.
  • the aluminum alloy is preferably an alloy containing an element such as magnesium, zinc or silicon.
  • the alloy contains a transition metal such as iron, copper, nickel, or chromium, the amount is preferably 100 ppm by mass or less.
  • the positive electrode 205 has a structure in which a positive electrode mixture containing an active material is supported on one side or both sides of a positive electrode current collector.
  • the thickness of one side of the positive electrode mixture is preferably in the range of 1.0 ⁇ m or more and 150 ⁇ m or less from the viewpoint of maintaining the large current discharge characteristics of the battery and the cycle life. Therefore, when the positive electrode current collector is supported on both sides, the total thickness of the positive electrode mixture is desirably in the range of 20 ⁇ m to 300 ⁇ m. A more preferable range of one side is 30 ⁇ m or more and 120 ⁇ m or less. Within this range, the large current discharge characteristics and the cycle life are improved.
  • the positive electrode mixture may contain a conductive material in addition to the binder that binds the positive electrode active material and the positive electrode active material.
  • various oxides such as manganese dioxide, lithium manganese composite oxide, lithium containing nickel cobalt oxide (for example, LiCOO 2 ), lithium containing nickel cobalt oxide (for example, LiNi 0.8 CO 0.2 O) 2 )
  • a lithium manganese composite oxide for example, LiMn 2 O 4 , LiMnO 2
  • LiMnO 2 lithium manganese composite oxide
  • acetylene black, carbon black, graphite and the like can be mentioned.
  • binder examples include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), polyimide and the like.
  • PTFE polytetrafluoroethylene
  • PVdF polyvinylidene fluoride
  • EPDM ethylene-propylene-diene copolymer
  • SBR styrene-butadiene rubber
  • polyimide polyimide
  • the compounding ratio of the positive electrode active material, the conductive material and the binder is 80% by mass to 95% by mass of the positive electrode active material, 3% by mass to 20% by mass of the conductive material, and 2% by mass to 7% by mass of the binder The range is preferable in order to obtain good high current discharge characteristics and cycle life.
  • a porous conductive substrate or a non-porous conductive substrate can be used as the current collector.
  • the thickness of the current collector is desirably 5 ⁇ m or more and 20 ⁇ m or less. Within this range, a balance between electrode strength and weight reduction can be achieved.
  • the positive electrode 205 is prepared, for example, by suspending an active material, a conductive material, and a binder in a widely used solvent to prepare a slurry, applying the slurry to a current collector, drying it, and then applying a press. Be done.
  • the positive electrode 205 may also be manufactured by forming an active material, a conductive material, and a binder in the form of pellets to form a positive electrode layer, and forming the positive electrode layer on a current collector.
  • negative electrode 203 As the negative electrode 203, for example, the negative electrode 100 described in the third embodiment is used.
  • Electrolyte A non-aqueous electrolytic solution, an electrolyte-impregnated polymer electrolyte, a polymer electrolyte, or an inorganic solid electrolyte can be used as the electrolyte.
  • the non-aqueous electrolytic solution is a liquid electrolytic solution prepared by dissolving the electrolyte in a non-aqueous solvent, and is held in the void in the electrode group.
  • non-aqueous solvent a non-aqueous solvent mainly composed of a mixed solvent of propylene carbonate (PC) or ethylene carbonate (EC) and a non-aqueous solvent having a viscosity lower than that of PC or EC (hereinafter referred to as second solvent) is used. Is preferred.
  • the second solvent for example, chain carbon is preferable, and among them, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, methyl ⁇ -butyrolactone (BL), acetonitrile ( AN), ethyl acetate (EA), toluene, xylene or methyl acetate (MA).
  • DMC dimethyl carbonate
  • MEC methyl ethyl carbonate
  • DEC diethyl carbonate
  • EA ethyl propionate
  • BL methyl ⁇ -butyrolactone
  • AN acetonitrile
  • EA ethyl acetate
  • MA toluene
  • MA methyl acetate
  • the viscosity of the second solvent is preferably 2.8 cmp or less at 25 ° C.
  • the blending amount of ethylene carbonate or propylene carbonate in the mixed solvent is preferably 1.0% to 80% by volume.
  • a more preferable blending amount of ethylene carbonate or propylene carbonate is 20% or more and 75% or less in volume ratio.
  • Examples of the electrolyte contained in the non-aqueous electrolytic solution include lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium borofluoride (LiBF 4 ), lithium arsenic hexafluoride (LiAsF 6 ) And lithium salts (electrolytes) such as lithium trifluorometasulfonate (LiCF 3 SO 3 ) and bis trifluoromethylsulfonyl imide lithium [LiN (CF 3 SO 2 ) 2 ].
  • LiPF 6 and LiBF 4 are preferably used.
  • the amount of electrolyte dissolved in the non-aqueous solvent is desirably 0.5 mol / L or more and 2.0 mol / L or less.
  • the separator 204 can be used.
  • the separator 204 uses a porous separator.
  • a porous film containing polyethylene, polypropylene, or polyfluorinated pinylidene (PVdF), a synthetic resin non-woven fabric, or the like can be used.
  • PVdF polyfluorinated pinylidene
  • porous films made of polyethylene or polypropylene or both are preferable because they can improve the safety of the secondary battery.
  • the thickness of the separator 204 is preferably 30 ⁇ m or less. If the thickness exceeds 30 ⁇ m, the distance between the positive and negative electrodes may be increased to increase the internal resistance.
  • the lower limit of the thickness is preferably 5 ⁇ m. If the thickness is less than 5 ⁇ m, the strength of the separator 204 may be significantly reduced to cause an internal short circuit.
  • the upper limit of the thickness is more preferably 25 ⁇ m, and the lower limit is more preferably 1.0 ⁇ m.
  • the separator 204 preferably has a thermal shrinkage of 20% or less when placed at 120 ° C. for one hour. When the thermal contraction rate exceeds 20%, the possibility of the occurrence of a short circuit due to heating increases. The heat shrinkage rate is more preferably 15% or less.
  • the separator 204 preferably has a porosity in the range of 30 to 60%. This is due to the following reasons. If the porosity is less than 30%, it may be difficult to obtain high electrolyte retention in the separator 204. On the other hand, if the porosity exceeds 60%, sufficient strength of the separator 204 may not be obtained. A more preferable range of the porosity is 35% or more and 70% or less.
  • the separator 204 preferably has an air permeability of 500 seconds / 100 cm 3 or less. If the air permeability exceeds 500 seconds / 100 cm 3 , it may be difficult to obtain high lithium ion mobility in the separator 204. Further, the lower limit value of the air permeability is 30 seconds / 100 cm 3 . If the air permeability is less than 30 seconds / 100 cm 3 , sufficient separator strength may not be obtained. The upper limit of the air permeability is more preferably 300 seconds / 100 cm 3 , and the lower limit is more preferably 50 seconds / 100 cm 3 . Ceramic particles may be coated on the surface of the separator 204. This can enhance safety. Examples of the ceramic particles include Al 2 O 3 , TiO 2 and ZrO 2 .
  • the battery pack according to the fifth embodiment includes one or more nonaqueous electrolyte secondary batteries (that is, single cells) according to the fourth embodiment.
  • the battery pack includes a plurality of unit cells, the unit cells are electrically connected in series, in parallel, or in series and in parallel.
  • the battery pack 300 will be specifically described with reference to the schematic view of FIG. 7 and the block diagram of FIG. In the battery pack 300 shown in FIG. 7, the flat non-aqueous electrolyte battery 200 shown in FIG. 5 is used as the single battery 301.
  • the plurality of unit cells 301 are stacked such that the negative electrode terminal 302 and the positive electrode terminal 303 extended to the outside are aligned in the same direction, and are assembled with the adhesive tape 304 to form a battery assembly 305. These single cells 301 are electrically connected in series to each other as shown in FIG.
  • the printed wiring board 306 is disposed to face the side surface of the unit cell 301 from which the negative electrode terminal 302 and the positive electrode terminal 303 extend.
  • a thermistor 307, a protection circuit 308, and a current-carrying terminal 309 for an external device are mounted on the printed wiring board 306, as shown in FIG. 8, as shown in FIG. 8, a thermistor 307, a protection circuit 308, and a current-carrying terminal 309 for an external device are mounted.
  • An insulating plate (not shown) is attached to the surface of the printed wiring board 306 facing the battery assembly 305 in order to avoid unnecessary connection with the wiring of the battery assembly 305.
  • the positive electrode lead 310 is connected to the positive electrode terminal 303 located in the lowermost layer of the assembled battery 305, and the tip thereof is inserted into the positive electrode connector 311 of the printed wiring board 306 and is electrically connected.
  • the negative electrode lead 312 is connected to the negative electrode terminal 302 located in the uppermost layer of the assembled battery 305, and the tip thereof is inserted into the negative electrode connector 313 of the printed wiring board 306 and electrically connected.
  • the connectors 311 and 313 are connected to the protective circuit 308 through the wires 314 and 315 formed on the printed wiring board 306.
  • the thermistor 307 is used to detect the temperature of the single battery 305, and the detection signal is transmitted to the protection circuit 308.
  • the protection circuit 308 can cut off the plus side wiring 316 a and the minus side wiring 316 b between the protection circuit 308 and the current application terminal 309 to the external device under predetermined conditions.
  • the predetermined condition is, for example, when the detected temperature of the thermistor 307 becomes equal to or higher than a predetermined temperature. Further, the predetermined condition is when overcharging, overdischarging, overcurrent, etc. of the single battery 301 is detected. The detection of the overcharge and the like is performed on the individual single battery 301 or the entire single battery 301.
  • the battery voltage When detecting each single battery 301, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each single battery 301.
  • the wires 317 for voltage detection are connected to each of the single cells 301, and the detection signal is transmitted to the protection circuit 308 through the wires 317.
  • Protective sheets 318 made of rubber or resin are respectively disposed on the three side surfaces of the assembled battery 305 except the side surfaces from which the positive electrode terminal 303 and the negative electrode terminal 302 project.
  • the assembled battery 305 is stored in the storage container 319 together with each protective sheet 318 and the printed wiring board 306. That is, the protective sheet 318 is disposed on both the inner side in the long side direction of the storage container 319 and the inner side in the short side direction, and the printed wiring board 306 is disposed on the inner side opposite to the short side.
  • the assembled battery 305 is located in a space surrounded by the protective sheet 318 and the printed wiring board 306.
  • the lid 320 is attached to the upper surface of the storage container 319.
  • a heat shrink tape may be used instead of the adhesive tape 304 for fixing the battery pack 305.
  • protective sheets are disposed on both sides of the battery pack, and the heat shrinkable tape is circulated, and then the heat shrinkable tape is heat shrunk to bind the battery pack.
  • FIG. 7 and FIG. 8 show a form in which the single cells 301 are connected in series, in order to increase the battery capacity, they may be connected in parallel, or a combination of series connection and parallel connection may be used.
  • the assembled battery packs can be further connected in series or in parallel. According to the present embodiment described above, by providing the non-aqueous electrolyte secondary battery having excellent charge and discharge cycle performance in the third embodiment, a battery pack having excellent charge and discharge cycle performance can be provided. it can.
  • the aspect of the battery pack is suitably changed according to a use.
  • the application of the battery pack is preferably one that exhibits excellent cycle characteristics when taking out a large current.
  • examples include power supplies for digital cameras, and in-vehicle applications such as two-wheel and four-wheel hybrid electric vehicles, two- and four-wheel electric vehicles, and assist bicycles.
  • a battery pack using a non-aqueous electrolyte secondary battery excellent in high temperature characteristics is suitably used for vehicles.
  • Example 1 Active material particles in which silicon in the surface portion was replaced with silicon carbide were produced under the following conditions.
  • a commercially available silicon monoxide particle (average particle diameter 45 ⁇ m) was ground by a ball mill to obtain a powder of average 0.3 ⁇ m.
  • sucrose is dissolved in a mixture of water and ethanol in an amount such that 0.3% by mass of carbon is formed when carbonized, and heated to 150 ° C. to remove alcohol and water, Heat treatment was performed at 1100 ° C. for 1 hour in Ar in an electric furnace (disproportionation treatment + reaction with carbon).
  • disproportionation treatment + reaction with carbon As a result, carbon-coated silicon oxide particles were obtained, and disproportionation of silicon oxide particles and carbonization of particles on the surface of the silicon oxide particles were achieved.
  • silicon oxide particles siliconized at the surface portion were complexed with hard carbon in the following procedure.
  • 1.2 g of silicon oxide particles and 0.3 g of graphite powder were added to a mixed solution of 2.4 g of furfuryl alcohol and 20 g of ethanol, and kneaded with a kneader to prepare a slurry sample.
  • 0.5 g of dilute hydrochloric acid as a polymerization catalyst of furfuryl alcohol was added to the obtained slurry, and the mixture was allowed to stand at room temperature, dried and solidified to obtain a carbon complex.
  • the obtained carbon composite was calcined at 1100 ° C.
  • Example 2 An electrode was prepared in the same manner as in Example 1, and powder X-ray diffraction measurement and high-resolution electron microscopic observation were performed, and a charge / discharge test was performed.
  • the obtained active material is mixed with 0.1 g of graphite having an average diameter of 3 ⁇ m, mixed with a solution prepared with N-methylpyrrolidone dispersion medium so that the polyimide is 16 mass%, using a rotation / revolution mixer Mixed.
  • the obtained paste-like slurry was applied onto a copper foil with a thickness of 12 ⁇ m and rolled, and then heat treated in Ar gas at 400 ° C. for 2 hours.
  • the obtained electrode was subjected to powder X-ray diffraction measurement and high resolution electron microscopy.
  • Discharge was performed up to 1.5 V at a constant current of 1 mA (CC discharge). Thereafter, the potential difference between the reference electrode and the test electrode is charged at a constant current of 6 mA to 0.01 V, then charged at a constant voltage, and then discharged to 1.5 V at a constant current of 6 mA. This cycle is repeated 100 times.
  • the ratio of the 100th discharge capacity to the first discharge capacity of the charge and discharge was defined as the discharge capacity retention ratio.
  • Discharge capacity retention rate (%) (100th discharge capacity) / (first discharge capacity) ⁇ 100
  • Example 1 The following Examples and Comparative Examples are summarized in Table 1. For the following examples and comparative examples, only portions different from those in Example 1 will be described, and the other synthesis and evaluation procedures are the same as in Example 1 and thus the description will be omitted.
  • Example 2 The silicon monoxide particles crushed by a ball mill in the same manner as in Example 1 were subjected to heat treatment at 1300 ° C. for 1 hour in an N 2 atmosphere. Using the heat-treated silicon oxide particles thus obtained, the composite material was treated with a carbon material in the same manner as in Example 1 to prepare a composite negative electrode active material. An electrode was produced in the same manner as in Example 1, and powder X-ray diffraction measurement and high-resolution electron microscopic observation were performed, and a charge and discharge test was performed.
  • Example 3 An electrode was manufactured in the same manner as in Example 1 except that polystyrene particles of 1 ⁇ m in size were added so as to be about 15% of the electrode volume in the step of forming electrodes using the composite particles prepared in Example 1 did. The same charge / discharge test as in Example 1 was carried out one cycle, and after the test, it was disassembled and the electrode was observed with an optical microscope.
  • Example 1 The silicon oxide particles pulverized in the same manner as in Example 1 were subjected to disproportionation treatment by heating at 1100 ° C. for 1 hour in an Ar atmosphere. Using the obtained disproportionated silicon oxide particles, the composite material was treated with a carbon material in the same manner as in Example 2 except that the firing temperature was set to 900 ° C., to prepare a composite negative electrode active material. An electrode was prepared in the same manner as in Example 1, and powder X-ray diffraction measurement and high-resolution electron microscopic observation were performed, and a charge / discharge test was performed.
  • Example 1 As a result of TEM observation of the cross section of the electrode in Example 1, the presence of silicon oxide particles covered with a carbonaceous material and a plurality of crystalline silicon nanoparticles of about 2 to 5 nm in its inside was confirmed. Furthermore, it was confirmed that particulate silicon carbide particles were present in the form of a portion partially invading the silicon oxide side near at least the interface between the silicon oxide particles and the coated carbon material.
  • Example 2 it was confirmed that part of the silicon particles was converted to silicon oxynitride (Si 2 ON 2 ). Silicon oxynitride does not react with lithium but has a slight decrease in capacity because it has neither electron conductivity nor ion conductivity. However, in the cycle property, the progress of deterioration is slow and an effect is observed.
  • Example 3 in SEM observation of the cross section of the electrode, it was observed that many voids of about 1 ⁇ m in size were formed on the outside of the composite particles.
  • the 1 ⁇ m-size voids are generated by thermal decomposition of polystyrene particles.
  • the volume of the void was about 15% with respect to the volume of the entire negative electrode.
  • FIG. 9 shows an optical microscope observation photograph of the current collector of the electrode after one cycle of Example 1 (without pore former) and Example 3 (with pore former). In the case where the hole was formed, almost no unevenness (wrinkling) as seen in the ordinary test was observed, and it was almost flat.
  • Example 3 showed further improvement in the cycle characteristics as compared with Example 1 in which the electrode was prepared without using styrene particles as a pore forming agent.
  • the energy density is slightly lowered by decreasing the electrode density, peeling of the electrode, breakage of the current collector, and the like can be prevented by forming no wrinkles in the current collector.
  • stress relaxation against volume expansion can be effectively achieved. It has been confirmed that the same effect occurs even when using an organic substance which thermally decomposes below the heat treatment temperature of the electrode as polystyrene does.

Abstract

[Problem] To provide an electrode active material for a non-aqueous electrolyte cell having excellent cycle characteristics. [Solution] The electrode active material for a non-aqueous electrolyte cell according to an embodiment is a particulate containing at least silicon oxide having silicon particles therein, a particulate containing at least one substance selected from silicon carbide, silicon nitride, and silicon oxynitride being supported on a surface layer part of the particulate.

Description

非水電解質電池用電極活物質、非水電解質二次電池用電極、非水電解質二次電池及び電池パックElectrode active material for non-aqueous electrolyte battery, electrode for non-aqueous electrolyte secondary battery, non-aqueous electrolyte secondary battery and battery pack
　実施形態は、非水電解質電池用電極活物質、非水電解質二次電池用電極、非水電解質二次電池及び電池パックに係わる。 The embodiment relates to an electrode active material for a non-aqueous electrolyte battery, an electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery, and a battery pack.
　近年、スマートフォンやタブレットなどに代表される小型携帯端末の急速な普及により、それらを駆動させる小型でエネルギー密度の高い電池に対する要求が高まっている。
　一般に、リチウムイオン電池の負極には黒鉛系材料が用いられている。黒鉛系材料の理論容量は３７２ｍＡｈ／ｇ（ＬｉＣ６）であり、現状、ほぼ限界にきている。さらなるエネルギー密度の向上には、新しい電極材の開発が必要である。特に、負極材として、炭素、リチウムに次いで電位が低く、電気化学当量の小さい、ケイ素、スズなどのリチウムと合金化する材料系が注目されている。 BACKGROUND ART In recent years, with the rapid spread of small portable terminals represented by smartphones and tablets, there is an increasing demand for small, high energy density batteries that drive them.
Generally, a graphite material is used for the negative electrode of a lithium ion battery. The theoretical capacity of the graphitic material is 372 mAh / g (LiC 6 ), which is almost at the present limit. Further energy density improvement requires the development of new electrode materials. In particular, as a negative electrode material, a material system that has the lowest potential next to carbon and lithium and has a small electrochemical equivalent and which is alloyed with lithium such as silicon and tin has attracted attention.
　中でもケイ素はケイ素原子１に対して４．４の比率までリチウム原子を吸蔵することができ、理論的には黒鉛系炭素材料の約１０倍の容量をもたせることができる。しかし、ケイ素粒子はリチウムを吸蔵すると体積がおよそ３～４倍に膨張するため、充放電の繰り返しにより粒子自体が割れて微粉化したり、電極を構成する他の部材に影響を及ぼしたりするなどの問題を有している。そこで、ケイ素粒子サイズを微細化し、凝集が起こりにくくなるように粒子の周囲をケイ素酸化物で覆う構造とすることが提案されている。例えば、ケイ素酸化物を加熱して不均化処理することによって、ケイ素酸化物中および表面にナノサイズのケイ素粒子を析出させることができる。これにより、ケイ素粒子がケイ素酸化物に固定化され、ケイ素粒子の粒成長や脱落を防止することができる。しかし、ケイ素酸化物粒子そのものは電子伝導性がなく、また、ケイ素粒子は、直接電解液と接すると反応して被膜を形成したり、フッ素成分が存在すると溶解したりして、容量の低下や充放電効率の低下を招く。 Above all, silicon can store lithium atoms at a ratio of 4.4 to 1 silicon atom, and theoretically can have a capacity about 10 times that of a graphitic carbon material. However, since silicon particles expand lithium by about three to four times in volume, the particles themselves are broken and pulverized by repeated charge and discharge, and other members that constitute the electrode are affected, etc. I have a problem. Therefore, it has been proposed that the size of the silicon particles be reduced and that the periphery of the particles be covered with silicon oxide so that aggregation is less likely to occur. For example, nanosized silicon particles can be deposited in and on the silicon oxide by heating the silicon oxide to disproportionate treatment. As a result, the silicon particles are immobilized on the silicon oxide, and grain growth and detachment of the silicon particles can be prevented. However, silicon oxide particles themselves do not have electron conductivity, and silicon particles react when they are in direct contact with the electrolytic solution to form a film, or they dissolve in the presence of a fluorine component, resulting in a decrease in capacity or Charge and discharge efficiency is reduced.
　サイクル特性に優れる非水電解質電池用電極活物質を提供することを目的とする。 An object of the present invention is to provide an electrode active material for a non-aqueous electrolyte battery which is excellent in cycle characteristics.
　実施形態の非水電解質電池用電極活物質は、ケイ素粒子を内部に有するケイ素酸化物を少なくとも含む粒子であり、粒子の表層部に炭化ケイ素、窒化ケイ素と酸窒化ケイ素より選ばれる少なくとも一種を含む粒子が担持されている。 The electrode active material for a non-aqueous electrolyte battery according to the embodiment is a particle containing at least a silicon oxide having silicon particles inside, and the surface layer of the particle contains at least one selected from silicon carbide, silicon nitride and silicon oxynitride. The particles are supported.
特開２０１２－１７８２７９号公報JP 2012-178279 A
実施形態の負極活物質の断面構造模式図である。It is a cross-sectional structure schematic diagram of the negative electrode active material of embodiment. 実施形態のケイ素酸化物粒子表面部粒子の担持状態模式図である。It is a supporting state schematic diagram of silicon oxide particle surface part particle | grains of embodiment. 実施形態の複合化負極活物質の断面構造模式図である。It is a cross-sectional structure schematic diagram of the composite negative electrode active material of the embodiment. 実施形態の非水電解質電池用電極を示す断面図である。It is a sectional view showing the electrode for nonaqueous electrolyte batteries of an embodiment. 実施形態の扁平型非水電解質電池を示す断面図である。It is a sectional view showing a flat type nonaqueous electrolyte battery of an embodiment. 実施形態の非水電解質二次電池の拡大図である。It is an enlarged view of the nonaqueous electrolyte secondary battery of an embodiment. 実施形態の電池パックの模式図である。It is a schematic diagram of the battery pack of embodiment. 電池パックの電気回路を示すブロック図である。It is a block diagram showing an electric circuit of a battery pack. 充放電試験後の実施例１と実施例３の集電体観察写真である。It is the collector observation photograph of Example 1 and Example 3 after a charging / discharging test.
　ケイ素酸化物の周りを、さらに導電性の炭素質物で覆うことにより、このようなケイ素粒子と電解液との接触を防ぎ、かつ、ケイ素粒子の体積膨張を抑制使用とする試みがなされている。 Attempts have been made to prevent the contact of such silicon particles with the electrolytic solution and to suppress the volume expansion of the silicon particles by further covering the silicon oxide with a conductive carbonaceous substance.
　炭素質物で被覆したケイ素酸化物を活物質として用いる電極の劣化の様子を詳細に分析したところ、炭素質物相内に繰り返しの充放電により空隙やクラックが形成され、そこに電解液が侵入して被膜を形成し、さらにこれら空隙が連結・拡大していくことによって、徐々に導電パスが分断されていくことが明らかになった。 The state of deterioration of the electrode using the silicon oxide coated with the carbonaceous material as the active material was analyzed in detail. As a result, voids and cracks were formed in the carbonaceous material phase by repeated charge and discharge, and the electrolyte penetrated there. It was revealed that the conductive path is gradually divided by forming a film and further connecting and expanding these air gaps.
　そして、その原因の一つとして、ケイ素酸化物の不均化反応で生じたケイ素粒子のうち、主としてケイ素酸化物の表面部に位置するケイ素粒子の存在が考えられた。この表面部に位置するケイ素粒子は、膨張・収縮により、周りの炭素材料に大きなストレスを与えることになる。 And as one of the causes, among silicon particles generated by disproportionation reaction of silicon oxide, the presence of silicon particles mainly located on the surface portion of silicon oxide was considered. The silicon particles located on this surface portion will cause great stress on the surrounding carbon material due to expansion and contraction.
　そこで、表面部に位置するケイ素粒子を、リチウムと反応しないように不均化することによる、サイクル性のさらなる向上を検討した。その結果、ケイ素酸化物の表面に位置するケイ素粒子を炭化あるいは窒化することで容量の低下を抑えることを検討した。 Therefore, further improvement of the cycleability was examined by disproportionating silicon particles located on the surface so as not to react with lithium. As a result, it was studied to suppress the decrease in capacity by carbonizing or nitriding silicon particles located on the surface of silicon oxide.
　例えば、一般式ＳｉＯｘで表わされるケイ素酸化物粒子の周りに炭化ケイ素の被膜を形成する方法が提案されている。炭化ケイ素はケイ素との結合性が強く、リチウムと電気化学的にも反応しない物質であるため、体積膨張抑制効果があると考えられる。しかし、炭化ケイ素は、イオン伝導性も持たないため、炭化ケイ素でケイ素酸化物粒子を覆ってしまうとリチウムが入りにくくなってしまい、レート特性が悪くなったり、充放電の容量そのものが低下したりしてしまうことになる。また、前述したように、ＳｉＯｘ粒子はできるだけ微細なものを使用した方が好ましく、微細なＳｉＯｘ粒子への均一な炭化ケイ素膜の被覆は容易ではなく、コスト的にも高くなってしまうという問題がある。 For example, a method has been proposed for forming a coating of silicon carbide around silicon oxide particles represented by the general formula SiOx. Silicon carbide is considered to have an effect of suppressing volume expansion because silicon carbide is a substance having strong bonding with silicon and which does not react electrochemically with lithium. However, since silicon carbide does not have ion conductivity, when silicon oxide particles are covered with silicon carbide, lithium is difficult to enter, the rate characteristics deteriorate, and the charge / discharge capacity itself decreases. It will be done. Further, as described above, it is preferable to use SiOx particles as fine as possible, and it is not easy to coat a uniform silicon carbide film on fine SiOx particles, and there is a problem that cost increases. is there.
　一方、ケイ素系電極など充放電時の体積変化が大きい活物質を用いた電極の別の問題として、体積膨張により集電体にシワが形成されるという問題がある。このシワの形成は、電極合剤層の厚さを増加させてしまうとともに、集電体に無理な力を加えてしまい集電体を破断し、短絡の危険性もあるため、できるだけシワを発生しないようにしておくことが必要である。 On the other hand, as another problem of an electrode using an active material having a large volume change during charge and discharge, such as a silicon-based electrode, there is a problem that wrinkles are formed on the current collector due to volume expansion. The formation of wrinkles causes the thickness of the electrode mixture layer to increase, and an excessive force is applied to the current collector to break the current collector, and there is also a risk of short circuit. It is necessary to keep in mind.
　発明者らは鋭意検討を重ねた結果、ケイ素酸化物を不均化して得られるケイ素／ケイ素酸化物複合体の少なくともケイ素酸化物粒子表面部に位置するケイ素粒子を、炭化ケイ素、あるいは窒化ケイ素、あるいは酸窒化ケイ素、に転化させることによって、それらを被覆する炭素材料への応力を緩和し、サイクル特性を向上させられることを見出した。 As a result of intensive studies, the inventors of the present invention have found that silicon particles located on at least the surface portion of silicon oxide particles of a silicon / silicon oxide composite obtained by disproportionation of silicon oxide are silicon carbide or silicon nitride, Alternatively, it has been found that conversion to silicon oxynitride can relieve stress on the carbon material covering them and improve cycle characteristics.
　さらに、活物質と導電助剤とバインダーにより作製される電極において、熱分解性の有機物を添加し加熱処理することによって、複合化した活物質の外に空隙を形成し、これにより体積膨張を緩和して集電体へのシワの発生を有効に抑えられることを見出した。
　以下、実施の形態について、図面を参照して説明する。 Furthermore, in the electrode made of the active material, the conductive additive, and the binder, a heat-degradable organic substance is added and heat treated to form a void outside the complexed active material, thereby alleviating the volume expansion. It has been found that the generation of wrinkles on the current collector can be effectively suppressed.
Embodiments will be described below with reference to the drawings.
（第１実施形態）
　実施形態の非水電解質電池用電極活物質は、ケイ素粒子を内部に有するケイ素酸化物を少なくとも含む粒子であり、粒子の表層部に炭化ケイ素、窒化ケイ素と酸窒化ケイ素より選ばれる少なくとも一種を含む粒子が担持されている。実施形態に係る活物質の断面の構造模式図を図１に示す。図１の活物質１０は、ケイ素ナノ粒子１１と、ケイ素酸化物粒子１２と、リチウムと合金化しない粒子１３を有している。リチウムと合金化しない粒子１３は、膜などではなく粒状であることが好ましい。ケイ素ナノ粒子１１およびケイ素酸化物粒子１２は、その内部にリンやホウ素などの微量元素を含んでいても構わない。実施形態の活物質１０は、例えば、非水電解質電池の電極に用いられる。 First Embodiment
The electrode active material for a non-aqueous electrolyte battery according to the embodiment is a particle containing at least a silicon oxide having silicon particles inside, and the surface layer of the particle contains at least one selected from silicon carbide, silicon nitride and silicon oxynitride. The particles are supported. The structural schematic diagram of the cross section of the active material which concerns on embodiment is shown in FIG. The active material 10 of FIG. 1 has silicon nanoparticles 11, silicon oxide particles 12, and particles 13 which are not alloyed with lithium. It is preferable that the particles 13 not to be alloyed with lithium be granular, not a film or the like. The silicon nanoparticles 11 and the silicon oxide particles 12 may contain trace elements such as phosphorus and boron inside thereof. The active material 10 of the embodiment is used, for example, for an electrode of a non-aqueous electrolyte battery.
　ケイ素ナノ粒子１１は、リチウムの吸蔵・放出能を有する。ケイ素ナノ粒子１１はケイ素酸化物の熱処理（不均化反応）により、ケイ素酸化物中の一部ケイ素が結晶性粒子として析出したものである。ケイ素ナノ粒子１１は、リチウムの吸蔵と放出を繰り返すたびに体積変化を生じる。この体積変化は活物質の崩壊を引き起こす恐れがある。そのため、できるだけ微細なサイズにすることが好ましい。ケイ素ナノ粒子１１の平均直径は、具体的には、２ｎｍ以上１５０ｎｍ以下にすることが好ましい。２ｎｍより小さいものは実質的に製造が困難であり、１５０ｎｍより大きいと充放電の繰り返しにより粒子そのものが微粉化してしまう恐れがあるからである。これらケイ素ナノ粒子１１は、図１のように周りをケイ素酸化物１２で被覆された構造をとる。一方、ケイ素酸化物粒子１２の表面部に位置するリチウムと合金化しない粒子１３は、その名の通り、リチウムに対しては不活性で、充放電反応中、反応に寄与せず、体積膨張も起こさない。 The silicon nanoparticles 11 have an ability to insert and extract lithium. The silicon nanoparticles 11 are obtained by depositing a part of silicon in the silicon oxide as crystalline particles by heat treatment (disproportionation reaction) of the silicon oxide. The silicon nanoparticles 11 change in volume each time lithium is repeatedly stored and released. This volume change may cause the collapse of the active material. Therefore, it is preferable to make the size as fine as possible. Specifically, the average diameter of the silicon nanoparticles 11 is preferably 2 nm or more and 150 nm or less. If the particle size is smaller than 2 nm, the production is substantially difficult. If the particle size is larger than 150 nm, the particles themselves may be pulverized due to repeated charge and discharge. These silicon nanoparticles 11 have a structure coated with silicon oxide 12 around as shown in FIG. On the other hand, particles 13 which are not alloyed with lithium located on the surface portion of the silicon oxide particles 12 are, as the name suggests, inert to lithium, do not contribute to the reaction during charge-discharge reaction, and volume expansion is also I do not wake up.
　ケイ素酸化物粒子１２は、ケイ素ナノ粒子１１を内部に含む。そして、ケイ素酸化物粒子１２は、その大部分が非晶質のケイ素酸化物であり、組成式ＳｉＯｘ（０＜ｘ＜２）で表される。ケイ素酸化物粒子１２の平均一次粒径は、０．１μｍ以上１０μｍ以下の範囲であることが好ましい。サイクル特性を考慮した場合、平均一次粒径をこの範囲にしておくと大きな劣化がなく、安定した充放電特性が得られるからである。ここでいう平均一次粒径とは、電極断面をイオンミリング加工し、又は、ケイ素酸化物粒子１２の粉末を走査型電子顕微鏡（ＳＥＭ：Ｓｃａｎｎｉｎｇ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｙ）もしくは透過型電子顕微鏡（ＴＥＭ：Ｔｒａｎｓｍｉｓｓｉｏｎ　Ｅｌｅｃｔｒｏｎ　Ｍｉｃｒｏｓｃｏｐｙ）にて２００００倍以上の倍率で観察した時に、視野の対角線上に存在する粒子を２０個以上選択し、その平均径として求めることができる。粒子径とは二次元画像における一つの粒子の長径と短径の平均値をいう。ケイ素ナノ粒子１１の平均直径（粒子径）の測定方法は、ケイ素酸化物粒子１２の平均一次粒径の測定方法と同様である。 The silicon oxide particles 12 contain silicon nanoparticles 11 therein. The silicon oxide particles 12 are mostly amorphous silicon oxides, and are represented by the composition formula SiO x (0 <x <2). The average primary particle size of the silicon oxide particles 12 is preferably in the range of 0.1 μm to 10 μm. When the cycle characteristics are considered, when the average primary particle diameter is in this range, there is no significant deterioration, and stable charge and discharge characteristics can be obtained. Here, the average primary particle size refers to ion milling of the electrode cross section, or a scanning electron microscope (SEM: scanning electron microscope) or a transmission electron microscope (TEM: transmission electron microscopy) of the powder of the silicon oxide particles 12 When observing with a magnification of 20000 times or more, the 20 or more particles present on the diagonal of the visual field can be selected and determined as their average diameter. The particle size refers to the average value of the major axis and minor axis of one particle in a two-dimensional image. The method of measuring the average diameter (particle diameter) of the silicon nanoparticles 11 is the same as the method of measuring the average primary particle diameter of the silicon oxide particles 12.
　ケイ素酸化物粒子１２中には、結晶質のケイ素酸化物相が含まれていても構わない。ケイ素酸化物粒子１２には、ケイ素酸化物の他にリチウムシリケート相が含まれていてもよい。 The silicon oxide particles 12 may contain a crystalline silicon oxide phase. The silicon oxide particles 12 may contain a lithium silicate phase in addition to the silicon oxide.
　ケイ素酸化物１２は、その大部分が非晶質であるため、充電時にリチウムが入り、体積膨張しても緩和能力がある。また、充放電サイクルにおけるケイ素ナノ粒子同士の成長および脱落を防ぐことができる。さらにケイ素酸化物粒子１２は、充電時にリチウムイオンと反応してリチウムシリケートを含む相を形成し、良イオン導電体となる特徴を有している。 Most of the silicon oxide 12 is amorphous, so lithium enters during charging and has a relaxation ability even if it expands in volume. In addition, it is possible to prevent the growth and detachment of silicon nanoparticles in charge and discharge cycles. Furthermore, the silicon oxide particles 12 react with lithium ions during charging to form a phase containing lithium silicate, and have a feature of becoming a good ion conductor.
　リチウムと合金化しない粒子１３は、結晶性の炭化ケイ素、結晶性の窒化ケイ素と結晶性の酸窒化ケイ素の中から選ばれる１種以上である。結晶性の炭化ケイ素、結晶性の窒化ケイ素と結晶性の酸窒化ケイ素は、それぞれ単体又は混合物として用いられる。リチウムと合金化しない粒子１３は、膜状ではなく、粒状であり、ケイ素酸化物粒子１２の表面に担持されて存在する。リチウムと合金化しない粒子１３は、ケイ素酸化物粒子１２の全表面を覆わないことが好ましい。このリチウムと合金化しない粒子１３の少なくとも一部がケイ素酸化物粒子１２の表層部に一部埋没して存在している。ここでいう埋没というのは、リチウムと合金化しない粒子１３の少なくとも一部がケイ素酸化物粒子１２の内部側に入り込んでいる状態であり、例えば、図２に示すような状態である。特に、リチウムと合金化しない粒子１３が炭化ケイ素組成の場合には、電気伝導性を有するため、炭素材料との導電パスの形成維持に役立つ。 The particles 13 which are not alloyed with lithium are at least one selected from crystalline silicon carbide, crystalline silicon nitride, and crystalline silicon oxynitride. Crystalline silicon carbide, crystalline silicon nitride and crystalline silicon oxynitride are used singly or as a mixture, respectively. The particles 13 which are not alloyed with lithium are not in the form of a film but are granular, and are supported on the surface of the silicon oxide particles 12 and present. Preferably, the particles 13 not alloyed with lithium do not cover the entire surface of the silicon oxide particles 12. At least a part of the particles 13 not alloyed with lithium is partially buried in the surface layer of the silicon oxide particles 12 and exists. The term “embedding” as used herein refers to a state in which at least a part of the particles 13 which are not alloyed with lithium intrudes into the inner side of the silicon oxide particles 12, for example, as shown in FIG. In particular, in the case where the particles 13 which are not alloyed with lithium have a silicon carbide composition, they have electrical conductivity, which helps to maintain the formation of a conductive path with the carbon material.
（製造方法）
　次に、第１の実施形態に係る活物質の製造方法について説明する。まず、ケイ素酸化物の表面部に窒化ケイ素もしくは酸窒化ケイ素を形成する方法について説明する。これら粒子の形成については雰囲気焼成法を用いる。まず、原料であるケイ素酸化物ＳｉＯｘ（０＜ｘ≦２）を雰囲気焼成炉に入れ、窒素ガス雰囲気中で熱処理を行う。ケイ素酸化物は、不活性雰囲気下の熱処理で不均化反応を起こし、ケイ素酸化物中および表面部にケイ素ナノ粒子を析出する。この不均化反応は、９００℃付近から始まる。 (Production method)
Next, a method of manufacturing the active material according to the first embodiment will be described. First, a method of forming silicon nitride or silicon oxynitride on the surface portion of silicon oxide will be described. An atmosphere baking method is used to form these particles. First, silicon oxide SiOx (0 <x ≦ 2), which is a raw material, is placed in an atmosphere baking furnace, and heat treatment is performed in a nitrogen gas atmosphere. Silicon oxide undergoes disproportionation reaction by heat treatment under an inert atmosphere to precipitate silicon nanoparticles in the silicon oxide and on the surface portion. This disproportionation reaction starts at around 900 ° C.
　その後、１１００℃以上１４００℃以下に昇温し、表面部に析出したケイ素粒子と窒素ガスとを反応させる。これにより、特に表面部に位置するケイ素ナノ粒子を窒化ケイ素、あるいは酸窒化ケイ素に変化させることができる。一般には、微量な酸素が存在する、酸化ケイ素が近くに存在する、などの理由から、酸窒化ケイ素が生成しやすい。熱処理温度が１１００℃より低い場合には窒化反応が起こらず、１４００℃より高い場合には不均化により生成したケイ素ナノ粒子が必要以上に粒成長を起こしてしまうため、好ましくない。熱処理の時間については特に定めないが、十分な反応を起こさせるために、１０分以上１２時間以下の範囲が好ましい。 Thereafter, the temperature is raised to 1100 ° C. or more and 1400 ° C. or less, and the silicon particles deposited on the surface portion are reacted with nitrogen gas. Thereby, silicon nanoparticles particularly located on the surface can be changed to silicon nitride or silicon oxynitride. In general, silicon oxynitride is likely to be formed because of the presence of a trace amount of oxygen, the presence of silicon oxide nearby, and the like. When the heat treatment temperature is lower than 1100 ° C., the nitriding reaction does not occur, and when it is higher than 1400 ° C., the silicon nanoparticles generated by disproportionation cause grain growth more than necessary, which is not preferable. The heat treatment time is not particularly limited, but in order to cause a sufficient reaction, a range of 10 minutes to 12 hours is preferable.
　一方、リチウムと合金化しない粒子１３として、炭化ケイ素を作製する場合には、原料であるケイ素酸化物粒子に炭素材の被覆を行って、それを熱処理することによって作ることができる。炭素材で被覆する方法は、特に限定されないが、有機炭化水素ガスを用いて気相法や、熱処理により炭化する有機前駆体を用いる方法などがある。炭素の被覆量としては、ケイ素酸化物粒子に対し、炭素化後に０．１質量％以上２０質量％以下の範囲であることが好ましい。炭素の被覆量が０．１質量％より小さい場合には、その後の炭化ケイ素化の効果が現れないことが好ましくない。また、炭素の被覆量が２０質量％を超えると、必要以上に炭化ケイ素化が進むことで、炭化ケイ素によって、ケイ素酸化物粒子が被覆されてしまうことが好ましくない。 On the other hand, when producing silicon carbide as particles 13 which are not alloyed with lithium, it can be produced by coating a carbon material on silicon oxide particles as a raw material and heat treating it. Although the method to coat | cover with a carbon material is not specifically limited, There exist a method of using the organic precursor carbonized by a gaseous phase method, heat processing, etc. using organic hydrocarbon gas. The carbon coverage is preferably in the range of 0.1% by mass or more and 20% by mass or less after carbonization with respect to the silicon oxide particles. If the carbon coverage is less than 0.1% by mass, it is not preferable that the effect of the subsequent silicidation does not appear. In addition, when the carbon coverage exceeds 20% by mass, it is not preferable that silicon carbide particles be coated with silicon carbide because silicon carbide proceeds more than necessary.
　炭素被覆処理を行ったケイ素酸化物粒子を不活性雰囲気中で加熱処理すると、不均化反応で生じた表面部ケイ素粒子と被覆炭素と間で反応が起こり、炭化ケイ素粒子が形成される。雰囲気は、Ａｒ雰囲気もしくはＡｒと水素の混合雰囲気下にて行うのが好ましい。熱処理温度は１０００℃以上１３００℃以下が好ましい。炭化ケイ素の生成は、ケイ素粒子の大きさなどにもよるが、少なくとも１０００℃以上の温度が必要であり、１３００℃よりも高温に加熱するとケイ素酸化物内部のケイ素ナノ粒子までも炭化ケイ素化してしまう可能性があるため、熱処理は１３００℃以下で行うことが好ましい。 When the carbon-coated silicon oxide particles are heat-treated in an inert atmosphere, a reaction occurs between the surface silicon particles produced by the disproportionation reaction and the coated carbon to form silicon carbide particles. The atmosphere is preferably an Ar atmosphere or a mixed atmosphere of Ar and hydrogen. The heat treatment temperature is preferably 1000 ° C. or more and 1300 ° C. or less. The formation of silicon carbide requires a temperature of at least 1000 ° C or more depending on the size of silicon particles etc. When heated to a temperature higher than 1300 ° C, even silicon nanoparticles inside silicon oxide are also siliconized It is preferable to carry out the heat treatment at 1300 ° C. or lower because of the possibility of
（第２実施形態）
　第２実施形態の活物質は、第１実施形態の活物質１０を炭素質物相２１で被覆して複合化させた複合化活物質２０である。第２の実施形態の複合化活物質２０の断面模式図を図３に示す。図３の複合化活物質２０は、活物質１０を炭素質物相２１で内包した構造である。炭素質物２１による活物質複合化は、単一の活物質１０を内包する形態でもよいし、複数の活物質１０を内包する形態でもよい。活物質１０の一部は、炭素質物相２１の表面に露出していてもよい。 Second Embodiment
The active material of the second embodiment is a composite active material 20 in which the active material 10 of the first embodiment is coated with a carbonaceous material phase 21 to form a composite. The cross-sectional schematic diagram of the complexing active material 20 of 2nd Embodiment is shown in FIG. The composite active material 20 of FIG. 3 has a structure in which the active material 10 is enclosed in the carbonaceous material phase 21. The active material complexation by the carbonaceous material 21 may be in a form in which a single active material 10 is contained, or in a form in which a plurality of active materials 10 are contained. A portion of the active material 10 may be exposed on the surface of the carbonaceous material phase 21.
活物質１０を内包する炭素質物相２１としては、グラファイト、ハードカーボン、ソフトカーボン、アモルファス炭素またはアセチレンブラックなどの炭素質物のうちのいずれか１種以上を用いることが好ましい。グラファイトは活物質の導電性を高め、容量を向上させる点で、好ましい。より好ましくは非晶質炭素である。 As the carbonaceous material phase 21 containing the active material 10, it is preferable to use any one or more kinds of carbonaceous materials such as graphite, hard carbon, soft carbon, amorphous carbon or acetylene black. Graphite is preferable in terms of enhancing the conductivity of the active material and improving the capacity. More preferably, it is amorphous carbon.
　複合化活物質２０は、その内部に炭素質物相２１とは異なる炭素質物や微細な空隙を含んでいてもよい。炭素質物相２１とは異なる炭素質物としては、結晶性の高い黒鉛、カーボンナノファイバーやカーボンナノチューブなどの炭素材料やアセチレンブラックなどの微結晶体が挙げられる。微細な空隙としては、直径が１０ｎｍ以上１０μｍ以下が好ましい大きさである。 The composite active material 20 may contain a carbonaceous material different from the carbonaceous material phase 21 or fine voids inside. Examples of the carbonaceous material different from the carbonaceous material phase 21 include highly crystalline graphite, carbon materials such as carbon nanofibers and carbon nanotubes, and microcrystalline materials such as acetylene black. As a fine space | gap, 10 nm-10 micrometers in diameter are preferable sizes.
　このように、炭素質物相２１中に負極活物質１０や炭素材料や空隙を分散させることにより、体積膨張を緩和するとともに、活物質の脱落等を防止することができる。また、炭素質物相２１は良好な導電材でもあるため、充放電容量や充放電効率の向上にも大きく貢献する。 As described above, by dispersing the negative electrode active material 10, the carbon material, and the voids in the carbonaceous material phase 21, it is possible to alleviate the volume expansion and to prevent the dropping of the active material and the like. In addition, since the carbonaceous material phase 21 is also a good conductive material, it greatly contributes to the improvement of charge and discharge capacity and charge and discharge efficiency.
　また、複合化活物質２０おいては、構造の保持および活物質１０の凝集を防ぎ、導電性を確保するために炭素繊維を含んでいてもよい。添加される炭素繊維の直径は、平均直径が１０ｎｍ以上１０００ｎｍ以下であることが好ましい。炭素繊維の含有量は０．１質量％以上８質量％以下の範囲であることが好ましい。８質量％を超えると、比表面積が大きいため、それを包む炭素質物相もより多く必要になり、結果としてケイ素含有量が減って好ましくない。より好ましくは０．５質量％以上５質量％以下である。 In addition, in the composite active material 20, carbon fibers may be included in order to prevent the retention of the structure and the aggregation of the active material 10, and the conductivity. The diameter of the carbon fiber to be added is preferably 10 nm or more and 1000 nm or less. The content of the carbon fiber is preferably in the range of 0.1% by mass to 8% by mass. If it exceeds 8% by mass, the specific surface area is large, so that more carbonaceous material phase is necessary to wrap it, and as a result, the silicon content is unfavorably reduced. More preferably, they are 0.5 mass% or more and 5 mass% or less.
　また、Ｌｉ４ＳｉＯ４などのリチウムシリケートが、複合化活物質２０内部の炭素質物相２１中や活物質１０中に分散されていてもよい。炭素質物に添加されたリチウム塩は熱処理を行うことによって複合粒子内のケイ素酸化物相と固体反応を起こしリチウムシリケートを形成することができる。 Alternatively, lithium silicate such as Li 4 SiO 4 may be dispersed in the carbonaceous material phase 21 in the composite active material 20 or in the active material 10. The lithium salt added to the carbonaceous matter can be subjected to a heat treatment to cause a solid reaction with the silicon oxide phase in the composite particles to form a lithium silicate.
　複合化活物質２０の中にＳｉＯ２前駆体およびＬｉ化合物が添加されていてもよい。これらの物質を炭素質物２１中に加えることでケイ素酸化物相１２と炭素質物２１の結合がより強固になると共に、Ｌｉイオン導電性に優れるＬｉ４ＳｉＯ４を酸化ケイ素相中に生成することができる。ＳｉＯ２前駆体としては、シリコンエトキシド等のアルコキシドが挙げられる。Ｌｉ化合物としては、炭酸リチウム、酸化リチウム、水酸化リチウム、シュウ酸リチウム、塩化リチウムなどが挙げられる。 A SiO 2 precursor and a Li compound may be added to the composite active material 20. The addition of these substances into the carbonaceous material 21 strengthens the bond between the silicon oxide phase 12 and the carbonaceous material 21 and forms Li 4 SiO 4 having excellent Li ion conductivity in the silicon oxide phase. it can. Examples of the SiO 2 precursor include alkoxides such as silicon ethoxide. Examples of the Li compound include lithium carbonate, lithium oxide, lithium hydroxide, lithium oxalate and lithium chloride.
　複合化活物質２０の平均一次粒径は、０．１μｍ以上５０μｍ以下の範囲であることが好ましい。この平均一次粒径が０．１μｍより小さいと、比表面積が大きくなり、その分だけ電極化する際に多くの結着剤が必要となってしまう。この平均一次粒径が５０μｍより大きいと、電極化した時に意図しない空間が形成され易く、結果として体積あたりの容量の低下を引き起こす。また、粗大な粒子は塗工プロセスにおいて障害になる。より好ましくは０．２μｍ以上２０μｍ以内である。この大きさの複合化活物質２０を得るために、たとえば、いったん複合化した粒子を粉砕・分級して得ることができる。方法はこれに限ったものではなく、スプレードライ法など最初から小さい３０の粒子製造を狙って作製しても構わない。複合化活物質２０の測定方法は、ケイ素酸化物粒子１２の平均一次粒径の測定方法と同様である。 The average primary particle size of the composite active material 20 is preferably in the range of 0.1 μm to 50 μm. When the average primary particle size is smaller than 0.1 μm, the specific surface area is increased, and accordingly, when forming an electrode, a large amount of binder is required. When the average primary particle size is larger than 50 μm, an unintended space is easily formed when the electrode is formed, resulting in a decrease in capacity per volume. Also, coarse particles are an obstacle in the coating process. More preferably, it is 0.2 μm or more and 20 μm or less. In order to obtain the composite active material 20 of this size, for example, the particles once composited can be obtained by crushing and classification. The method is not limited to this, and it may be produced aiming at the production of 30 small particles from the beginning such as a spray dry method. The method of measuring the composite active material 20 is the same as the method of measuring the average primary particle size of the silicon oxide particles 12.
　複合化活物質２０の比表面積としては０．５ｍ２／ｇ以上１００ｍ２／ｇ以下の範囲であることが好ましい。粒径および比表面積は、リチウムの挿入脱離反応の速度に影響し、負極特性に大きな影響をもつと考えられるが、この範囲の値であれば安定して特性を発揮することができる。比表面積は、窒素ガス吸着によるＢＥＴ法（Ｂｒｕｎａｕｅｒ，　Ｅｍｍｅｔｔ，　Ｔｅｌｌｅｒ）によって求められる。 The specific surface area of the composite active material 20 is preferably in the range of 0.5 m 2 / g to 100 m 2 / g. The particle size and the specific surface area affect the rate of the insertion and desorption reaction of lithium and are considered to have a great influence on the negative electrode characteristics, but if the value is in this range, the characteristics can be exhibited stably. The specific surface area is determined by the BET method (Brunauer, Emmett, Teller) by nitrogen gas adsorption.
　複合化活物質２０中のケイ素酸化物相と炭素質物相の比率は、ケイ素酸化物と炭素の質量比で０．２≦ケイ素酸化物／炭素≦２の範囲にあるのが好ましい。この範囲であれば、活物質として大きな容量と良好なサイクル特性を得ることができるからである。 The ratio of the silicon oxide phase to the carbonaceous material phase in the composite active material 20 is preferably in the range of 0.2 ≦ silicon oxide / carbon ≦ 2 in mass ratio of silicon oxide to carbon. Within this range, a large capacity and good cycle characteristics can be obtained as the active material.
（複合化処理）
　次に、活物質１０を炭素質物２１で複合化する方法について説明する。
　複合化処理においては、活物質１０と、黒鉛などの炭素材料および炭素前駆体からなる有機材料を混合し複合体を形成する。混合は、連続式ボールミルや遊星ボールミル等を用いて行うことができる。 (Composition processing)
Next, a method of combining the active material 10 with the carbonaceous material 21 will be described.
In the complexing process, the active material 10 is mixed with a carbon material such as graphite and an organic material consisting of a carbon precursor to form a complex. The mixing can be performed using a continuous ball mill, a planetary ball mill, or the like.
　有機材料としては、グラファイト、コークス、低温焼成炭、ピッチなどの炭素材料および炭素材料前駆体のうち少なくとも一種を用いることができる。特に、ピッチなど加熱により溶融するものは力学的なミル処理中には溶融して複合化が良好に進まないため、コークス・グラファイトなど溶融しないものと混合して使用すると良い。 As the organic material, at least one of carbon materials such as graphite, coke, low-temperature fired carbon, pitch and the like, and carbon material precursors can be used. In particular, since what is melted by heating, such as pitch, is melted during mechanical milling and composite formation does not proceed well, it is preferable to use it by mixing with coke, graphite, etc. which does not melt.
　液相での混合攪拌により複合化を行う方法を以下に説明する。混合攪拌処理は例えば各種攪拌装置、ボールミル、ビーズミル装置およびこれらの組み合わせにより行うことができる。ケイ素酸化物粒子と炭素前駆体および炭素材との複合化は分散媒を用いた液中で液相混合を行うと良い。より均一に分散させるためである。分散媒としては有機溶媒、水等を用いることができるが、ケイ素酸化物粒子と炭素前駆体および炭素材の双方と良好な親和性をもつ液体を用いることが好ましい。具体例として、エタノール、アセトン、イソプロピルアルコール、メチルエチルケトン、酢酸エチル、Ｎ－メチルピロリドンなどを挙げることができる。 The method of complexing by mixing and stirring in the liquid phase is described below. The mixing and stirring process can be performed by, for example, various stirring devices, a ball mill, a bead mill device, and a combination thereof. The complexation of the silicon oxide particles with the carbon precursor and the carbon material is preferably performed by liquid phase mixing in a liquid using a dispersion medium. It is for making it distribute more uniformly. Although an organic solvent, water, etc. can be used as a dispersion medium, It is preferable to use the liquid which has a favorable affinity with both a silicon oxide particle, a carbon precursor, and a carbon material. As specific examples, ethanol, acetone, isopropyl alcohol, methyl ethyl ketone, ethyl acetate, N-methyl pyrrolidone and the like can be mentioned.
　また、炭素前駆体はケイ素ナノ粒子と均一に混合するために混合段階で液体あるいは分散媒に可溶であるものが好ましく、液体であり容易に重合可能なモノマーあるいはオリゴマーであると特に好ましい。例えば、フラン樹脂、キシレン樹脂、ケトン樹脂、アミノ樹脂、メラミン樹脂、尿素樹脂、アニリン樹脂、ウレタン樹脂、ポリイミド樹脂、ポリエステル樹脂、フェノール樹脂、レゾール樹脂、スクロースなどの有機材料が挙げられる。液相で混合を行った材料は、固化あるいは乾燥工程を経て炭素被覆ケイ素酸化物粒子－有機材料複合化物を形成する。 The carbon precursor is preferably one that is soluble in the liquid or dispersion medium in the mixing step to be uniformly mixed with the silicon nanoparticles, and is particularly preferably a liquid and an easily polymerizable monomer or oligomer. For example, organic materials such as furan resin, xylene resin, ketone resin, amino resin, melamine resin, urea resin, aniline resin, urethane resin, polyimide resin, polyester resin, phenol resin, resole resin, sucrose and the like can be mentioned. The material mixed in the liquid phase undergoes a solidification or drying process to form a carbon-coated silicon oxide particle-organic material composite.
（炭化焼成処理）
　炭化焼成は、Ａｒ中等の不活性雰囲気下にて行なわれる。炭化焼成においては、ケイ素酸化物粒子－有機材料複合化物中のポリマーまたはピッチ等の炭素前駆体が炭化される。この炭化焼成の温度は、使用する有機材料化合物の熱分解温度にもよるが、適正な範囲として７００℃以上１３００℃以下であることが好ましい。ケイ素酸化物粒子の粒子径にもよるが、１３００℃より高い温度では、炭化ケイ素化がより進行し、容量が低下してしまうため、好ましくない。焼成時間は、焼成の温度にもよるが、１０分から１２時間の範囲であることが好ましい。 (Carbonizing treatment)
The carbonization firing is performed under an inert atmosphere such as Ar. In carbonization and firing, a polymer in a silicon oxide particle-organic material composite or a carbon precursor such as pitch is carbonized. The temperature of the carbonization and firing depends on the thermal decomposition temperature of the organic material compound to be used, but is preferably 700 ° C. or more and 1300 ° C. or less as an appropriate range. Although depending on the particle size of the silicon oxide particles, at temperatures higher than 1300 ° C., siliconization proceeds more and the capacity is reduced, which is not preferable. The firing time is preferably in the range of 10 minutes to 12 hours depending on the temperature of the firing.
　以上のような合成方法により本実施形態に係る負極材料が得られる。炭化焼成後の生成物は各種ミル、粉砕装置、グラインダー等を用いて粒径、比表面積等を調製してもよい。
　以上、説明した第１実施形態に係る負極材料と第２実施形態に係る複合化負極活物質は、粉末Ｘ線回折測定において少なくとも２θ＝２８．４°に回折ピークを有するものである。２θ＝２８．４°のピークは、不均化反応で形成したケイ素に由来する。このような負極活物質を用いることで充放電特性に優れ、サイクル寿命の長い負極材料を実現することができる。 The negative electrode material according to the present embodiment can be obtained by the synthesis method as described above. The product after carbonization and firing may be adjusted in particle size, specific surface area and the like using various mills, pulverizers, grinders and the like.
As described above, the negative electrode material according to the first embodiment and the composite negative electrode active material according to the second embodiment have a diffraction peak at least 2θ = 28.4 ° in powder X-ray diffraction measurement. The peak at 2θ = 28.4 ° is derived from silicon formed in the disproportionation reaction. By using such a negative electrode active material, a negative electrode material excellent in charge and discharge characteristics and having a long cycle life can be realized.
（第３実施形態）
　第３実施形態は、図４の断面図に示すように、負極合剤層１０１と集電体１０２とを含む。負極合剤層１０１は集電体１０２上に配置された、活物質を含む合剤の層である。負極合剤層１０１は、負極活物質１０３と、導電材１０４と結着剤１０５とを含む。結着剤１０５は、負極合剤層１０１と集電体を接合する。以下、第１実施形態又は第２実施形態の活物質を例に、負極として第３実施形態を説明するが、電池の正極に第３実施形態の電極を用いても良い。負極合剤層１０１は、集電体１０２の片面または両面に形成されている。 Third Embodiment
The third embodiment includes a negative electrode mixture layer 101 and a current collector 102, as shown in the cross-sectional view of FIG. The negative electrode mixture layer 101 is a layer of a mixture including an active material disposed on the current collector 102. The negative electrode mixture layer 101 includes a negative electrode active material 103, a conductive material 104, and a binder 105. The binder 105 joins the negative electrode mixture layer 101 and the current collector. Hereinafter, the third embodiment will be described as the negative electrode, taking the active material of the first embodiment or the second embodiment as an example, but the electrode of the third embodiment may be used for the positive electrode of the battery. The negative electrode mixture layer 101 is formed on one side or both sides of the current collector 102.
　負極合剤層１０１の厚さは、１０μｍ以上１５０μｍ以下の範囲であることが望ましい。従って負極集電体の両面に担持されている場合は負極合剤層１０１の合計の厚さ、２０μｍ以上３００μｍ以下の範囲となる。片面の厚さのより好ましい範囲は、１０μｍ以上１００μｍ以下である。この範囲であると大電流放電特性とサイクル寿命は大幅に向上する。負極合剤層１０１には、負極合剤層１０１に含まれる活物質のＬｉ挿入脱離に伴う体積変化を緩和する空隙を含むことが好ましい。 The thickness of the negative electrode mixture layer 101 is preferably in the range of 10 μm to 150 μm. Therefore, when the negative electrode current collector is supported on both sides, the total thickness of the negative electrode mixture layer 101 is in the range of 20 μm to 300 μm. A more preferable range of the thickness on one side is 10 μm or more and 100 μm or less. Within this range, the large current discharge characteristics and the cycle life are significantly improved. It is preferable that the negative electrode mixture layer 101 include a void that relieves a volume change associated with Li insertion and release of the active material contained in the negative electrode mixture layer 101.
　負極合剤層１０１の負極活物質１０３、導電材１０４および結着剤１０５の配合割合は、負極活物質１０３が５７質量％以上９５質量％以下、導電材１０４が３質量％以上２０質量％以下、結着剤１０５が２質量％以上４０質量％以下の範囲にすることが、良好な大電流放電特性とサイクル寿命を得られるために好ましい。 The mixing ratio of the negative electrode active material 103, the conductive material 104, and the binder 105 in the negative electrode mixture layer 101 is 57% by mass to 95% by mass of the negative electrode active material 103, and 3% by mass to 20% by mass of the conductive material 104 The binder 105 is preferably in the range of 2% by mass to 40% by mass in order to obtain good large current discharge characteristics and cycle life.
　実施形態の集電体１０２は、負極合剤層１０１と結着する導電性の部材である。集電体１０２としては、多孔質構造の導電性基板か、あるいは無孔の導電性基板を用いることができる。これら導電性基板は、例えば、銅、ステンレスまたはニッケルから形成することができる。集電体の厚さは５μｍ以上２０μｍ以下であることが望ましい。この範囲内であると電極強度と軽量化のバランスがとれるからである。 The current collector 102 of the embodiment is a conductive member that bonds with the negative electrode mixture layer 101. As the current collector 102, a porous conductive substrate or a non-porous conductive substrate can be used. These conductive substrates can be formed of, for example, copper, stainless steel or nickel. The thickness of the current collector is desirably 5 μm or more and 20 μm or less. Within this range, a balance between electrode strength and weight reduction can be achieved.
　負極活物質１０３としては、電極活物質として用いられるものを使用することができる。負極活物質１０３としては、例えば、金属および金属酸化物を用いることができる。金属および金属酸化物としては、Ｓｉ、Ｓｎ、Ａｌ、Ｉｎ、Ｇａ、Ｐｂ、Ｔｉ、Ｎｉ、Ｍｇ、Ｗ、Ｍｏ、およびＦｅからなる群より選択される元素、選択された元素を含む合金、選択された元素の酸化物と選択された元素を含む酸化物の内から選ばれる少なくとも１種であることが好ましい。第１実施形態の活物質１０または第２実施形態の複合化活物質２０を用いることがより好ましい。 As the negative electrode active material 103, those used as an electrode active material can be used. As the negative electrode active material 103, for example, metals and metal oxides can be used. As the metal and metal oxide, an element selected from the group consisting of Si, Sn, Al, In, Ga, Pb, Ti, Ni, Mg, W, Mo and Fe, an alloy containing the selected element, selection Preferably, it is at least one selected from oxides of selected elements and oxides containing selected elements. It is more preferable to use the active material 10 of the first embodiment or the composite active material 20 of the second embodiment.
　また、負極合剤層１０１は、導電材１０４を含んでいてもよい。導電材１０４としては、アセチレンブラック、カーボンブラック、黒鉛などを挙げることができる。 In addition, the negative electrode mixture layer 101 may contain the conductive material 104. As the conductive material 104, acetylene black, carbon black, graphite and the like can be given.
　負極合剤層１０１は負極材料同士を結着する結着剤１０５を含んでいてもよい。結着剤１０５としては、例えばポリテトラフルオロエチレン（ＰＴＦＥ）、ポリ弗化ビニリデン（ＰＶｄＦ）、エチレン－プロピレン－ジエン共重合体（ＥＰＤＭ）、スチレン－ブタジエンゴム（ＳＢＲ）、ポリイミド、ポリアラミド等を用いることができる。また、結着剤には２種またはそれ以上のものを組み合わせて用いてもよく、活物質同士の結着に優れた結着剤と活物質と集電体の結着に優れた結着剤の組み合わせや、硬度の高いものと柔軟性に優れるものを組み合わせて用いると、寿命特性に優れた負極を作製することができる。 The negative electrode mixture layer 101 may contain a binder 105 that binds negative electrode materials. As the binding agent 105, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), polyimide, polyaramid or the like is used. be able to. Further, two or more binders may be used in combination, and the binder excellent in binding between the active materials and the binder excellent in binding between the active material and the current collector When the combination of the above, the thing with high hardness, and the thing excellent in pliability are used combining, the negative electrode excellent in the lifetime characteristic can be produced.
　空隙の平均サイズは、２０ｎｍ以上５μｍ以下とするのが好ましい。２０ｎｍより小さい場合には集電体１０２のシワ抑制効果が小さく、５μｍより大きいと導電パスが分断され、電池特性が低下するからである。 The average size of the voids is preferably 20 nm or more and 5 μm or less. When it is smaller than 20 nm, the effect of suppressing the wrinkles of the current collector 102 is small, and when it is larger than 5 μm, the conductive path is divided and the battery characteristics are deteriorated.
　負極合剤層１０１の体積に対して、集電体１０２のシワの発生を抑制する観点から、５％以上３０％以下であることが好ましい。なお、負極合剤層１０１の体積には、負極合剤層１０１中の体積も含む。空隙の体積は、５％より小さいと、その効果が十分ではなく、３０％より大きいと、エネルギー密度など、電極特性そのものを低下させてしまう恐れがある。より好ましい空隙の体積は、負極合剤層１０１の体積に対して、１０％以上２０％以下である。 From the viewpoint of suppressing the generation of wrinkles of the current collector 102, the volume of the negative electrode mixture layer 101 is preferably 5% or more and 30% or less. Note that the volume of the negative electrode mixture layer 101 also includes the volume in the negative electrode mixture layer 101. If the volume of the void is less than 5%, the effect is not sufficient, and if it is greater than 30%, the electrode characteristics such as energy density may be degraded. A more preferable void volume is 10% or more and 20% or less with respect to the volume of the negative electrode mixture layer 101.
　また、負極１００の負極合剤層１０１の厚み相当の直径を有する活物質粒子１０３の個数割合が全体の２０％以下である方が好ましい。２０％を超えると活物質粒子の外に形成する空隙の効果が失われてしまい、集電体１０２にできるシワの形成を抑えられなくなる。負極合剤層１０１の厚み相当の直径を有する活物質粒子１０３とは、活物質粒子１０３の直径が、負極合剤層１０１の厚みの９０％以上であるものを示す。 Further, it is preferable that the number ratio of the active material particles 103 having a diameter equivalent to the thickness of the negative electrode mixture layer 101 of the negative electrode 100 be 20% or less of the whole. If it exceeds 20%, the effect of the voids formed outside the active material particles is lost, and the formation of wrinkles formed on the current collector 102 can not be suppressed. The active material particles 103 having a diameter equivalent to the thickness of the negative electrode mixture layer 101 indicate that the diameter of the active material particles 103 is 90% or more of the thickness of the negative electrode mixture layer 101.
　空隙の体積は以下の方法で求めることができる。
　活物質粒子および空隙の大きさは、断面加工した電極を走査型電子顕微鏡（ＳＥＭ）にて２０００倍程度以上の倍率で観察することによって求めることができる。具体的には、視野中の対角線上に存在する空隙を２０個以上選択し、その平均値として求めることができる。空隙は反射電子による観察などを組み合わせると、より鮮明に観察することができる。また、空隙の体積については、銅箔付きの電極を用いて水銀圧入法により測定することができる。水銀圧入法では、計算上ではあるが、気孔径分布を得ることができる。 The volume of the void can be determined by the following method.
The sizes of the active material particles and the voids can be determined by observing the cross-section processed electrode with a scanning electron microscope (SEM) at a magnification of about 2000 or more. Specifically, 20 or more air gaps present on the diagonal in the field of view can be selected and determined as the average value thereof. The air gap can be observed more clearly by combining the observation with reflected electrons and the like. Moreover, about the volume of a space | gap, it can measure by the mercury intrusion method using the electrode with copper foil. In the mercury intrusion method, although calculated, pore diameter distribution can be obtained.
　実施形態の負極１００の製造方法について説明する。負極活物質１０３と、導電材１０４と、結着剤１０５と、造孔剤とを含有する混合物をペースト化し、集電体１０２上に塗布、プレスして、３５０℃以上４５０℃以下の温度で加熱して負極を得る。この方法により、複合化負極活物質の外部つまり、負極合剤層１０１中に空隙を形成できる。負極１００はまた、負極活物質１０３と、導電材１０４と、結着剤１０５と、造孔剤とを含有する混合物をペレット状に形成して負極合剤層１０１とし、これを集電体１０２上に形成することにより作製されてもよい。 The manufacturing method of the negative electrode 100 of embodiment is demonstrated. A mixture containing the negative electrode active material 103, the conductive material 104, the binder 105, and the pore forming agent is made into a paste, applied onto the current collector 102, and pressed, at a temperature of 350 ° C. to 450 ° C. Heat to obtain a negative electrode. By this method, voids can be formed outside the composite negative electrode active material, that is, in the negative electrode mixture layer 101. In the negative electrode 100, a mixture containing the negative electrode active material 103, the conductive material 104, the binder 105, and the pore forming agent is formed into a pellet to form a negative electrode mixture layer 101, which is used as a current collector 102. It may be made by forming on top.
　空隙は、熱分解性の有機物を造孔剤として用いることによって形成する。造孔剤には、４５０℃以下の温度で熱分解を開始する有機物が好ましい。このような有機物としては、熱可塑性樹脂やエラストマーが用いられる。熱可塑性樹脂の例としては、ポリスチレン、ポリエチレン、ポリプロピレン、ポリイソブチレン、ポリメタクリル酸メチル、ポリテトラフルオロエチレン、ポリ－α―メチルスチレン、ポリアセタール、セルロースアセテート、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリフッ化ビニル、ポリ酢酸ビニル、ポリビニルアルコールなどがある。また、エラストマーの例としては、スチレンブタジエンゴム、ニトリルブタジエンゴム、アクリル酸エステル、酢酸ビニル、メチルメタクリレートブタジエンゴム、クロロプレンゴム、カルボキシ変性スチレンブタジエンゴムや、これらを水等に分散させたラテックスなどが挙げられる。 The voids are formed by using a pyrolyzable organic substance as a pore forming agent. The pore forming agent is preferably an organic substance which starts thermal decomposition at a temperature of 450 ° C. or less. As such an organic substance, a thermoplastic resin or an elastomer is used. Examples of thermoplastic resins include polystyrene, polyethylene, polypropylene, polyisobutylene, polymethyl methacrylate, polytetrafluoroethylene, poly-α-methylstyrene, polyacetal, cellulose acetate, polyvinyl acetate, polyvinylidene chloride, polyvinyl fluoride , Polyvinyl acetate, polyvinyl alcohol and the like. Further, examples of the elastomer include styrene butadiene rubber, nitrile butadiene rubber, acrylic ester, vinyl acetate, methyl methacrylate butadiene rubber, chloroprene rubber, carboxy-modified styrene butadiene rubber, latex obtained by dispersing these in water, etc. Be
　これら造孔剤は、負極合剤層１０１の体積を１００％とした時に、空隙の体積が、５以上３０％の範囲になるように添加することが好ましい。 These pore forming agents are preferably added so that the volume of the voids is in the range of 5 to 30% when the volume of the negative electrode mixture layer 101 is 100%.
　熱処理温度は造孔剤である有機物の熱分解温度より高い温度に設定するのが好ましい。そこで、好ましい熱処理温度は、３５０℃以上４５０℃以下である。熱処理後には有機物ができるだけ熱分解しているのが好ましいが、残留物が残っていても構わない。 The heat treatment temperature is preferably set to a temperature higher than the thermal decomposition temperature of the organic substance which is a pore forming agent. Therefore, a preferable heat treatment temperature is 350 ° C. or more and 450 ° C. or less. After the heat treatment, it is preferable that the organic matter be thermally decomposed as much as possible, but a residue may remain.
（第４実施形態）
　第４実施形態に係る非水電解質二次電池を説明する。
　第４実施形態に係る非水電解質二次電池は、外装材と、外装材内に収納された正極と、外装材内に正極と空間的に離間して、例えばセパレータを介在して収納された負極と、外装材内に充填された非水電解質とを具備する。 Fourth Embodiment
A nonaqueous electrolyte secondary battery according to a fourth embodiment will be described.
The non-aqueous electrolyte secondary battery according to the fourth embodiment is housed, for example, with a separator interposed in the exterior material, the positive electrode accommodated in the exterior material, and the positive electrode spatially separated from the positive electrode in the exterior material. A negative electrode and a non-aqueous electrolyte filled in the outer package are provided.
　実施形態に係る非水電解質二次電池２００の一例を示した図５の模式図を参照してより詳細に説明する。図５は、外装材２０２がラミネートフィルムからなる扁平型非水電解質二次電池２００の断面模式図である。 A more detailed description will be given with reference to the schematic view of FIG. 5 showing an example of the non-aqueous electrolyte secondary battery 200 according to the embodiment. FIG. 5 is a schematic cross-sectional view of a flat-type non-aqueous electrolyte secondary battery 200 in which the packaging material 202 is formed of a laminate film.
　扁平状の捲回電極群２０１は、２枚の樹脂層の間にアルミニウム箔を介在したラミネートフィルムからなる外装材２０２内に収納されている。扁平状の捲回電極群２０１は、一部を抜粋した模式図である図６に示すように、負極２０３、セパレータ２０４、正極２０５、セパレータ２０４の順で積層されている。そして積層物を渦巻状に捲回し、プレス成型することにより形成されたものである。外装材２０２に最も近い電極は負極であり、この負極は、外装材２０２側の負極集電体には、負極合剤が形成されておらず、負極集電体の電池内面側の片面のみに負極合剤を形成した構成を有する。その他の負極２０３は、負極集電体の両面に負極合剤を形成して構成されている。正極２０５は、正極集電体の両面に正極合剤を形成して構成されている。 The flat wound electrode group 201 is accommodated in an exterior material 202 formed of a laminate film in which an aluminum foil is interposed between two resin layers. The flat wound electrode group 201 is laminated in the order of a negative electrode 203, a separator 204, a positive electrode 205, and a separator 204, as shown in FIG. Then, the laminate is spirally wound and formed by press molding. The electrode closest to the packaging material 202 is a negative electrode, and no negative electrode mixture is formed on the negative electrode current collector on the packaging material 202 side, and only on one surface of the negative electrode current collector on the battery inner surface side It has the structure which formed the negative mix. The other negative electrode 203 is configured by forming a negative electrode mixture on both sides of the negative electrode current collector. The positive electrode 205 is configured by forming a positive electrode mixture on both sides of a positive electrode current collector.
　捲回電極群２０１の外周端近傍において、負極端子は最外殻の負極２０３の負極集電体に電気的に接続され、正極端子は内側の正極２０５の正極集電体に電気的に接続されている。これらの負極端子２０６及び正極端子２０７は、外装材２０２の開口部から外部に延出されている。例えば液状非水電解質は、袋状外装材２０２の開口部から注入されている。外装材２０２の開口部を負極端子２０６及び正極端子２０７を挟んでヒートシールすることにより捲回電極群２０１及び液状非水電解質を密封している。 The negative electrode terminal is electrically connected to the negative electrode current collector of the outermost negative electrode 203, and the positive electrode terminal is electrically connected to the positive electrode current collector of the inner positive electrode 205 near the outer peripheral end of the wound electrode group 201. ing. The negative electrode terminal 206 and the positive electrode terminal 207 are extended from the opening of the package 202 to the outside. For example, a liquid non-aqueous electrolyte is injected from the opening of the bag-like exterior material 202. The wound electrode group 201 and the liquid non-aqueous electrolyte are sealed by heat-sealing the opening of the package 202 with the negative electrode terminal 206 and the positive electrode terminal 207 interposed therebetween.
　負極端子２０６は、例えばアルミニウムまたはＭｇ、Ｔｉ、Ｚｎ、Ｍｎ、Ｆｅ、Ｃｕ、Ｓｉ等の元素を含むアルミニウム合金が挙げられる。負極端子２０６は、負極集電体との接触抵抗を低減するために、負極集電体と同様の材料であることが好ましい。
　正極端子２０７は、リチウムイオン金属に対する電位が３～４．２５Ｖの範囲における電気的安定性と導電性とを備える材料を用いることができる。具体的には、アルミニウムまたはＭｇ、Ｔｉ、Ｚｎ、Ｍｎ、Ｆｅ、Ｃｕ、Ｓｉ等の元素を含むアルミニウム合金が挙げられる。正極端子２０７は、正極集電体との接触抵抗を低減するために、正極集電体と同様の材料であることが好ましい。 Examples of the negative electrode terminal 206 include aluminum or an aluminum alloy containing an element such as Mg, Ti, Zn, Mn, Fe, Cu, or Si. The negative electrode terminal 206 is preferably made of the same material as the negative electrode current collector in order to reduce the contact resistance with the negative electrode current collector.
The positive electrode terminal 207 can use a material having electrical stability and conductivity in the range of 3 to 4.25 V with respect to the lithium ion metal. Specifically, an aluminum alloy containing an element such as aluminum or Mg, Ti, Zn, Mn, Fe, Cu, Si or the like can be mentioned. The positive electrode terminal 207 is preferably made of the same material as the positive electrode current collector in order to reduce the contact resistance with the positive electrode current collector.
　以下、非水電解質二次電池２００の構成部材である外装材２０２、正極２０５、電解質、セパレータ２０４について詳細に説明する。 Hereinafter, the packaging material 202, the positive electrode 205, the electrolyte, and the separator 204, which are components of the non-aqueous electrolyte secondary battery 200, will be described in detail.
１）外装材２０２
　外装材２０２は、厚さ０．５ｍｍ以下のラミネートフィルムから形成される。或いは、外装材は厚さ１．０ｍｍ以下の金属製容器が用いられる。金属製容器は、厚さ０．５ｍｍ以下であることがより好ましい。 1) Exterior material 202
The exterior material 202 is formed of a laminate film having a thickness of 0.5 mm or less. Alternatively, a metal container having a thickness of 1.0 mm or less is used as the exterior material. The metal container is more preferably 0.5 mm or less in thickness.
　外装材２０２の形状は、扁平型（薄型）、角型、円筒型、コイン型、及びボタン型から選択できる。外装材の例には、電池寸法に応じて、例えば携帯用電子機器等に積載される小型電池用外装材、二輪乃至四輪の自動車等に積載される大型電池用外装材などが含まれる。 The shape of the exterior material 202 can be selected from flat (thin), square, cylindrical, coin, and button. Examples of the exterior material include, for example, an exterior material for a small battery loaded on a portable electronic device or the like, an exterior material for a large battery loaded on a two- or four-wheeled automobile, etc. according to the battery size.
　ラミネートフィルムは、樹脂層間に金属層を介在した多層フィルムが用いられる。金属層は、軽量化のためにアルミニウム箔若しくはアルミニウム合金箔が好ましい。樹脂層は、例えばポリプロピレン（ＰＰ）、ポリエチレン（ＰＥ）、ナイロン、ポリエチレンテレフタレート（ＰＥＴ）等の高分子材料を用いることができる。ラミネートフィルムは、熱融着によりシールを行って外装材の形状に成形することができる。 As the laminate film, a multilayer film in which a metal layer is interposed between resin layers is used. The metal layer is preferably aluminum foil or aluminum alloy foil in order to reduce the weight. For the resin layer, for example, polymeric materials such as polypropylene (PP), polyethylene (PE), nylon, polyethylene terephthalate (PET) can be used. The laminated film can be molded into the shape of the exterior material by sealing by heat fusion.
　金属製容器は、アルミニウムまたはアルミニウム合金等から作られる。アルミニウム合金は、マグネシウム、亜鉛、ケイ素等の元素を含む合金が好ましい。合金中に鉄、銅、ニッケル、クロム等の遷移金属が含まれる場合、その量は１００質量ｐｐｍ以下にすることが好ましい。 The metal container is made of aluminum or aluminum alloy or the like. The aluminum alloy is preferably an alloy containing an element such as magnesium, zinc or silicon. When the alloy contains a transition metal such as iron, copper, nickel, or chromium, the amount is preferably 100 ppm by mass or less.
２）正極２０５
　正極２０５は、活物質を含む正極合剤が正極集電体の片面もしくは両面に担持された構造を有する。
　前記正極合剤の片面の厚さは１．０μｍ以上１５０μｍ以下の範囲であることが電池の大電流放電特性とサイクル寿命の保持の点から望ましい。従って正極集電体の両面に担持されている場合は正極合剤の合計の厚さは２０μｍ以上３００μｍ以下の範囲となることが望ましい。片面のより好ましい範囲は３０μｍ以上１２０μｍ以下である。この範囲であると大電流放電特性とサイクル寿命は向上する。
　正極合剤は、正極活物質と正極活物質同士を結着する結着剤の他に導電材を含んでいてもよい。 2) positive electrode 205
The positive electrode 205 has a structure in which a positive electrode mixture containing an active material is supported on one side or both sides of a positive electrode current collector.
The thickness of one side of the positive electrode mixture is preferably in the range of 1.0 μm or more and 150 μm or less from the viewpoint of maintaining the large current discharge characteristics of the battery and the cycle life. Therefore, when the positive electrode current collector is supported on both sides, the total thickness of the positive electrode mixture is desirably in the range of 20 μm to 300 μm. A more preferable range of one side is 30 μm or more and 120 μm or less. Within this range, the large current discharge characteristics and the cycle life are improved.
The positive electrode mixture may contain a conductive material in addition to the binder that binds the positive electrode active material and the positive electrode active material.
　正極活物質としては、種々の酸化物、例えば二酸化マンガン、リチウムマンガン複合酸化物、リチウム含有ニッケルコバルト酸化物（例えばＬｉＣＯＯ２）、リチウム含有ニッケルコバルト酸化物（例えばＬｉＮｉ０．８ＣＯ０．２Ｏ２）、リチウムマンガン複合酸化物（例えばＬｉＭｎ２Ｏ４、ＬｉＭｎＯ２）を用いると高電圧が得られるために好ましい。 As the positive electrode active material, various oxides such as manganese dioxide, lithium manganese composite oxide, lithium containing nickel cobalt oxide (for example, LiCOO 2 ), lithium containing nickel cobalt oxide (for example, LiNi 0.8 CO 0.2 O) 2 ) It is preferable to use a lithium manganese composite oxide (for example, LiMn 2 O 4 , LiMnO 2 ) because a high voltage can be obtained.
　導電材としてはアセチレンブラック、カーボンブラック、黒鉛などを挙げることができる。 As the conductive material, acetylene black, carbon black, graphite and the like can be mentioned.
　結着材の具体例としては例えばポリテトラフルオロエチレン（ＰＴＦＥ）、ポリ弗化ビニリデン（ＰＶｄＦ）、エチレン－プロピレン－ジエン共重合体（ＥＰＤＭ）、スチレン－ブタジエンゴム（ＳＢＲ）、ポリイミド等を用いることができる。 Specific examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), polyimide and the like. Can.
　正極活物質、導電材および結着剤の配合割合は、正極活物質８０質量％以上９５質量％以下、導電材３質量％以上２０質量％以下、結着剤２質量％以上７質量％以下の範囲にすることが、良好な大電流放電特性とサイクル寿命を得られるために好ましい。 The compounding ratio of the positive electrode active material, the conductive material and the binder is 80% by mass to 95% by mass of the positive electrode active material, 3% by mass to 20% by mass of the conductive material, and 2% by mass to 7% by mass of the binder The range is preferable in order to obtain good high current discharge characteristics and cycle life.
　集電体としては、多孔質構造の導電性基板かあるいは無孔の導電性基板を用いることができる。集電体の厚さは５μｍ以上２０μｍ以下であることが望ましい。この範囲であると電極強度と軽量化のバランスがとれるからである。 As the current collector, a porous conductive substrate or a non-porous conductive substrate can be used. The thickness of the current collector is desirably 5 μm or more and 20 μm or less. Within this range, a balance between electrode strength and weight reduction can be achieved.
　正極２０５は、例えば活物質、導電材及び結着剤を汎用されている溶媒に懸濁してスラリーを調製し、このスラリーを集電体に塗布し、乾燥し、その後、プレスを施すことにより作製される。正極２０５はまた活物質、導電材及び結着剤をペレット状に形成して正極層とし、これを集電体上に形成することにより作製されてもよい。 The positive electrode 205 is prepared, for example, by suspending an active material, a conductive material, and a binder in a widely used solvent to prepare a slurry, applying the slurry to a current collector, drying it, and then applying a press. Be done. The positive electrode 205 may also be manufactured by forming an active material, a conductive material, and a binder in the form of pellets to form a positive electrode layer, and forming the positive electrode layer on a current collector.
３）負極２０３
　負極２０３としては、例えば、第３実施形態に記載した負極１００を用いる。 3) negative electrode 203
As the negative electrode 203, for example, the negative electrode 100 described in the third embodiment is used.
４）電解質
　電解質としては非水電解液、電解質含浸型ポリマー電解質、高分子電解質、あるいは無機固体電解質を用いることができる。
　非水電解液は、非水溶媒に電解質を溶解することにより調製される液体状電解液で、電極群中の空隙に保持される。 4) Electrolyte A non-aqueous electrolytic solution, an electrolyte-impregnated polymer electrolyte, a polymer electrolyte, or an inorganic solid electrolyte can be used as the electrolyte.
The non-aqueous electrolytic solution is a liquid electrolytic solution prepared by dissolving the electrolyte in a non-aqueous solvent, and is held in the void in the electrode group.
　非水溶媒としては、プロピレンカーボネート（ＰＣ）やエチレンカーボネート（ＥＣ）とＰＣやＥＣより低粘度である非水溶媒（以下第２溶媒と称す）との混合溶媒を主体とする非水溶媒を用いることが好ましい。 As the non-aqueous solvent, a non-aqueous solvent mainly composed of a mixed solvent of propylene carbonate (PC) or ethylene carbonate (EC) and a non-aqueous solvent having a viscosity lower than that of PC or EC (hereinafter referred to as second solvent) is used. Is preferred.
　第２溶媒としては、例えば鎖状カーボンが好ましく、中でもジメチルカーボネート（ＤＭＣ）、メチルエチルカーボネート（ＭＥＣ）、ジエチルカーボネート（ＤＥＣ）、プロピオン酸エチル、プロピオン酸メチル、γ－ブチロラクトン（ＢＬ）、アセトニトリル（ＡＮ）、酢酸エチル（ＥＡ）、トルエン、キシレンまたは、酢酸メチル（ＭＡ）等が挙げられる。これらの第２溶媒は、単独または２種以上の混合物の形態で用いることができる。特に、第２溶媒はドナー数が１６．５以下であることがより好ましい。 As the second solvent, for example, chain carbon is preferable, and among them, dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, methyl γ-butyrolactone (BL), acetonitrile ( AN), ethyl acetate (EA), toluene, xylene or methyl acetate (MA). These second solvents can be used alone or in the form of a mixture of two or more. In particular, the second solvent more preferably has a donor number of 16.5 or less.
　第２溶媒の粘度は、２５℃において２．８ｃｍｐ以下であることが好ましい。混合溶媒中のエチレンカーボネートまたはプロピレンカーボネートの配合量は、体積比率で１．０％～８０％であることが好ましい。より好ましいエチレンカーボネートまたはプロピレンカーボネートの配合量は体積比率で２０％以上７５％以下である。 The viscosity of the second solvent is preferably 2.8 cmp or less at 25 ° C. The blending amount of ethylene carbonate or propylene carbonate in the mixed solvent is preferably 1.0% to 80% by volume. A more preferable blending amount of ethylene carbonate or propylene carbonate is 20% or more and 75% or less in volume ratio.
　非水電解液に含まれる電解質としては、例えば過塩素酸リチウム（ＬｉＣｌＯ４）、六弗化リン酸リチウム（ＬｉＰＦ６）、ホウ弗化リチウム（ＬｉＢＦ４）、六弗化砒素リチウム（ＬｉＡｓＦ６）、トリフルオロメタスルホン酸リチウム（ＬｉＣＦ３ＳＯ３）、ビストリフルオロメチルスルホニルイミドリチウム［ＬｉＮ（ＣＦ３ＳＯ２）２］等のリチウム塩（電解質）が挙げられる。中でもＬｉＰＦ６、ＬｉＢＦ４を用いるのが好ましい。
　電解質の非水溶媒に対する溶解量は、０．５ｍｏｌ／Ｌ以上２．０ｍｏｌ／Ｌ以下とすることが望ましい。 Examples of the electrolyte contained in the non-aqueous electrolytic solution include lithium perchlorate (LiClO 4 ), lithium hexafluorophosphate (LiPF 6 ), lithium borofluoride (LiBF 4 ), lithium arsenic hexafluoride (LiAsF 6 ) And lithium salts (electrolytes) such as lithium trifluorometasulfonate (LiCF 3 SO 3 ) and bis trifluoromethylsulfonyl imide lithium [LiN (CF 3 SO 2 ) 2 ]. Among them, LiPF 6 and LiBF 4 are preferably used.
The amount of electrolyte dissolved in the non-aqueous solvent is desirably 0.5 mol / L or more and 2.0 mol / L or less.
５）セパレータ２０４
　非水電解液を用いる場合、および電解質含浸型ポリマー電解質を用いる場合においてはセパレータ２０４を用いることができる。セパレータ２０４は多孔質セパレータを用いる。セパレータ２０４の材料としては、例えば、ポリエチレン、ポリプロピレン、またはポリ弗化ピニリデン（ＰＶｄＦ）を含む多孔質フィルム、合成樹脂製不織布等を用いることができる。中でも、ポリエチレンか、あるいはポリプロピレン、または両者からなる多孔質フィルムは、二次電池の安全性を向上できるため好ましい。 5) Separator 204
In the case of using a non-aqueous electrolyte and in the case of using an electrolyte-impregnated polymer electrolyte, the separator 204 can be used. The separator 204 uses a porous separator. As a material of the separator 204, for example, a porous film containing polyethylene, polypropylene, or polyfluorinated pinylidene (PVdF), a synthetic resin non-woven fabric, or the like can be used. Among them, porous films made of polyethylene or polypropylene or both are preferable because they can improve the safety of the secondary battery.
　セパレータ２０４の厚さは、３０μｍ以下にすることが好ましい。厚さが３０μｍを越えると、正負極間の距離が大きくなって内部抵抗が大きくなる恐れがある。また、厚さの下限値は、５μｍにすることが好ましい。厚さを５μｍ未満にすると、セパレータ２０４の強度が著しく低下して内部ショートが生じやすくなる恐れがある。厚さの上限値は、２５μｍにすることがより好ましく、また、下限値は１．０μｍにすることがより好ましい。
　セパレータ２０４は、１２０℃の条件で１時間おいたときの熱収縮率が２０％以下であることが好ましい。熱収縮率が２０％を超えると、加熱により短絡が起こる可能性が大きくなる。熱収縮率は、１５％以下にすることがより好ましい。 The thickness of the separator 204 is preferably 30 μm or less. If the thickness exceeds 30 μm, the distance between the positive and negative electrodes may be increased to increase the internal resistance. The lower limit of the thickness is preferably 5 μm. If the thickness is less than 5 μm, the strength of the separator 204 may be significantly reduced to cause an internal short circuit. The upper limit of the thickness is more preferably 25 μm, and the lower limit is more preferably 1.0 μm.
The separator 204 preferably has a thermal shrinkage of 20% or less when placed at 120 ° C. for one hour. When the thermal contraction rate exceeds 20%, the possibility of the occurrence of a short circuit due to heating increases. The heat shrinkage rate is more preferably 15% or less.
　セパレータ２０４は、多孔度が３０以上６０％以下の範囲であることが好ましい。これは次のような理由によるものである。多孔度を３０％未満にすると、セパレータ２０４において高い電解質保持性を得ることが困難になる恐れがある。一方、多孔度が６０％を超えると十分なセパレータ２０４強度を得られなくなる恐れがある。多孔度のより好ましい範囲は、３５％以上７０％以下である。 The separator 204 preferably has a porosity in the range of 30 to 60%. This is due to the following reasons. If the porosity is less than 30%, it may be difficult to obtain high electrolyte retention in the separator 204. On the other hand, if the porosity exceeds 60%, sufficient strength of the separator 204 may not be obtained. A more preferable range of the porosity is 35% or more and 70% or less.
　セパレータ２０４は、空気透過率が５００秒／１００ｃｍ３以下であると好ましい。空気透過率が５００秒／１００ｃｍ３を超えると、セパレータ２０４において高いリチウムイオン移動度を得ることが困難になる恐れがある。また、空気透過率の下限値は、３０秒／１００ｃｍ３である。空気透過率を３０秒／１００ｃｍ３未満にすると、十分なセパレータ強度を得られなくなる恐れがあるからである。
　空気透過率の上限値は３００秒／１００ｃｍ３にすることがより好ましく、また、下限値は５０秒／１００ｃｍ３にするとより好ましい。
　セパレータ２０４表面に、セラミックスの粒子がコーティングされていてもよい。これにより、安全性を高めることができる。セラミックス粒子の例としては、Ａｌ２Ｏ３、ＴｉＯ２、ＺｒＯ２などである。 The separator 204 preferably has an air permeability of 500 seconds / 100 cm 3 or less. If the air permeability exceeds 500 seconds / 100 cm 3 , it may be difficult to obtain high lithium ion mobility in the separator 204. Further, the lower limit value of the air permeability is 30 seconds / 100 cm 3 . If the air permeability is less than 30 seconds / 100 cm 3 , sufficient separator strength may not be obtained.
The upper limit of the air permeability is more preferably 300 seconds / 100 cm 3 , and the lower limit is more preferably 50 seconds / 100 cm 3 .
Ceramic particles may be coated on the surface of the separator 204. This can enhance safety. Examples of the ceramic particles include Al 2 O 3 , TiO 2 and ZrO 2 .
（第５実施形態）
　次に、第５実施形態に係る電池パックを説明する。
　第５実施形態に係る電池パックは、上記第４実施形態に係る非水電解質二次電池（即ち、単電池）を一以上有する。電池パックに複数の単電池が含まれる場合、各単電池は、電気的に直列、並列、或いは、直列と並列に接続して配置される。
　図７の模式図及び図８のブロック図を参照して電池パック３００を具体的に説明する。図７に示す電池パック３００では、単電池３０１として図５に示す扁平型非水電解液電池２００を使用している。 Fifth Embodiment
Next, a battery pack according to a fifth embodiment will be described.
The battery pack according to the fifth embodiment includes one or more nonaqueous electrolyte secondary batteries (that is, single cells) according to the fourth embodiment. When the battery pack includes a plurality of unit cells, the unit cells are electrically connected in series, in parallel, or in series and in parallel.
The battery pack 300 will be specifically described with reference to the schematic view of FIG. 7 and the block diagram of FIG. In the battery pack 300 shown in FIG. 7, the flat non-aqueous electrolyte battery 200 shown in FIG. 5 is used as the single battery 301.
　複数の単電池３０１は、外部に延出した負極端子３０２及び正極端子３０３が同じ向きに揃えられるように積層され、粘着テープ３０４で締結することにより組電池３０５を構成している。これらの単電池３０１は、図８に示すように互いに電気的に直列に接続されている。 The plurality of unit cells 301 are stacked such that the negative electrode terminal 302 and the positive electrode terminal 303 extended to the outside are aligned in the same direction, and are assembled with the adhesive tape 304 to form a battery assembly 305. These single cells 301 are electrically connected in series to each other as shown in FIG.
　プリント配線基板３０６は、負極端子３０２及び正極端子３０３が延出する単電池３０１側面と対向して配置されている。プリント配線基板３０６には、図８に示すようにサーミスタ３０７、保護回路３０８及び外部機器への通電用端子３０９が搭載されている。なお、組電池３０５と対向するプリント配線基板３０６の面には組電池３０５の配線と不要な接続を回避するために絶縁板（図示せず）が取り付けられている。 The printed wiring board 306 is disposed to face the side surface of the unit cell 301 from which the negative electrode terminal 302 and the positive electrode terminal 303 extend. On the printed wiring board 306, as shown in FIG. 8, a thermistor 307, a protection circuit 308, and a current-carrying terminal 309 for an external device are mounted. An insulating plate (not shown) is attached to the surface of the printed wiring board 306 facing the battery assembly 305 in order to avoid unnecessary connection with the wiring of the battery assembly 305.
　正極側リード３１０は、組電池３０５の最下層に位置する正極端子３０３に接続され、その先端はプリント配線基板３０６の正極側コネクタ３１１に挿入されて電気的に接続されている。負極側リード３１２は、組電池３０５の最上層に位置する負極端子３０２に接続され、その先端はプリント配線基板３０６の負極側コネクタ３１３に挿入されて電気的に接続されている。これらのコネクタ３１１、３１３は、プリント配線基板３０６に形成された配線３１４、３１５を通して保護回路３０８に接続されている。 The positive electrode lead 310 is connected to the positive electrode terminal 303 located in the lowermost layer of the assembled battery 305, and the tip thereof is inserted into the positive electrode connector 311 of the printed wiring board 306 and is electrically connected. The negative electrode lead 312 is connected to the negative electrode terminal 302 located in the uppermost layer of the assembled battery 305, and the tip thereof is inserted into the negative electrode connector 313 of the printed wiring board 306 and electrically connected. The connectors 311 and 313 are connected to the protective circuit 308 through the wires 314 and 315 formed on the printed wiring board 306.
　サーミスタ３０７は、単電池３０５の温度を検出するために用いられ、その検出信号は保護回路３０８に送信される。保護回路３０８は、所定の条件で保護回路３０８と外部機器への通電用端子３０９との間のプラス側配線３１６ａ及びマイナス側配線３１６ｂを遮断できる。所定の条件とは、例えばサーミスタ３０７の検出温度が所定温度以上になったときである。また、所定の条件とは単電池３０１の過充電、過放電、過電流等を検出したときである。この過充電等の検出は、個々の単電池３０１もしくは単電池３０１全体について行われる。個々の単電池３０１を検出する場合、電池電圧を検出してもよいし、正極電位もしくは負極電位を検出してもよい。後者の場合、個々の単電池３０１中に参照極として用いるリチウム電極が挿入される。図７及び図８の場合、単電池３０１それぞれに電圧検出のための配線３１７を接続し、これら配線３１７を通して検出信号が保護回路３０８に送信される。 The thermistor 307 is used to detect the temperature of the single battery 305, and the detection signal is transmitted to the protection circuit 308. The protection circuit 308 can cut off the plus side wiring 316 a and the minus side wiring 316 b between the protection circuit 308 and the current application terminal 309 to the external device under predetermined conditions. The predetermined condition is, for example, when the detected temperature of the thermistor 307 becomes equal to or higher than a predetermined temperature. Further, the predetermined condition is when overcharging, overdischarging, overcurrent, etc. of the single battery 301 is detected. The detection of the overcharge and the like is performed on the individual single battery 301 or the entire single battery 301. When detecting each single battery 301, the battery voltage may be detected, or the positive electrode potential or the negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each single battery 301. In the case of FIG. 7 and FIG. 8, the wires 317 for voltage detection are connected to each of the single cells 301, and the detection signal is transmitted to the protection circuit 308 through the wires 317.
　正極端子３０３及び負極端子３０２が突出する側面を除く組電池３０５の三側面には、ゴムもしくは樹脂からなる保護シート３１８がそれぞれ配置されている。
　組電池３０５は、各保護シート３１８及びプリント配線基板３０６と共に収納容器３１９内に収納される。すなわち、収納容器３１９の長辺方向の両方の内側面と短辺方向の内側面それぞれに保護シート３１８が配置され、短辺方向の反対側の内側面にプリント配線基板３０６が配置される。組電池３０５は、保護シート３１８及びプリント配線基板３０６で囲まれた空間内に位置する。蓋３２０は、収納容器３１９の上面に取り付けられている。 Protective sheets 318 made of rubber or resin are respectively disposed on the three side surfaces of the assembled battery 305 except the side surfaces from which the positive electrode terminal 303 and the negative electrode terminal 302 project.
The assembled battery 305 is stored in the storage container 319 together with each protective sheet 318 and the printed wiring board 306. That is, the protective sheet 318 is disposed on both the inner side in the long side direction of the storage container 319 and the inner side in the short side direction, and the printed wiring board 306 is disposed on the inner side opposite to the short side. The assembled battery 305 is located in a space surrounded by the protective sheet 318 and the printed wiring board 306. The lid 320 is attached to the upper surface of the storage container 319.
　なお、組電池３０５の固定には粘着テープ３０４に代えて、熱収縮テープを用いてもよい。この場合、組電池の両側面に保護シートを配置し、熱収縮テープを周回させた後、熱収縮テープを熱収縮させて組電池を結束させる。 A heat shrink tape may be used instead of the adhesive tape 304 for fixing the battery pack 305. In this case, protective sheets are disposed on both sides of the battery pack, and the heat shrinkable tape is circulated, and then the heat shrinkable tape is heat shrunk to bind the battery pack.
　図７、図８では単電池３０１を直列接続した形態を示したが、電池容量を増大させるためには並列に接続しても、または直列接続と並列接続を組み合わせてもよい。組み上がった電池パックをさらに直列、並列に接続することもできる。
　以上記載した本実施形態によれば、上記第３実施形態における優れた充放電サイクル性能を有する非水電解質二次電池を備えることにより、優れた充放電サイクル性能を有する電池パックを提供することができる。 Although FIG. 7 and FIG. 8 show a form in which the single cells 301 are connected in series, in order to increase the battery capacity, they may be connected in parallel, or a combination of series connection and parallel connection may be used. The assembled battery packs can be further connected in series or in parallel.
According to the present embodiment described above, by providing the non-aqueous electrolyte secondary battery having excellent charge and discharge cycle performance in the third embodiment, a battery pack having excellent charge and discharge cycle performance can be provided. it can.
　なお、電池パックの態様は用途により適宜変更される。電池パックの用途は、大電流を取り出したときに優れたサイクル特性を示すものが好ましい。具体的には、デジタルカメラの電源用や、二輪乃至四輪のハイブリッド電気自動車、二輪乃至四輪の電気自動車、アシスト自転車等の車載用が挙げられる。特に、高温特性の優れた非水電解質二次電池を用いた電池パックは車載用に好適に用いられる。 In addition, the aspect of the battery pack is suitably changed according to a use. The application of the battery pack is preferably one that exhibits excellent cycle characteristics when taking out a large current. Specifically, examples include power supplies for digital cameras, and in-vehicle applications such as two-wheel and four-wheel hybrid electric vehicles, two- and four-wheel electric vehicles, and assist bicycles. In particular, a battery pack using a non-aqueous electrolyte secondary battery excellent in high temperature characteristics is suitably used for vehicles.
　以下に具体的な実施例（各実施例で説明するそれぞれの条件で、図５で説明した電池を具体的に作製した例）を挙げ、その効果について述べる。但し、これらの実施例に限定されるものではない。 Hereinafter, specific examples (examples in which the battery described in FIG. 5 is specifically manufactured under the respective conditions described in the respective examples) will be described, and the effects thereof will be described. However, it is not limited to these examples.
（実施例１）次のような条件で、表面部のケイ素が炭化ケイ素に置き換えられた活物質粒子を作製した。市販の一酸化ケイ素粒子（平均粒径４５μｍ）をボールミルにて粉砕し、平均０．３μｍの粉末を得た。
　この粉末に対して、炭素化したときに０．３質量％の炭素が形成される量のスクロースを水＋エタノールの混合液に溶いて、１５０℃に加熱してアルコールおよび水分を飛ばした後、電気炉にてＡｒ中、１１００℃で１時間熱処理を行った（不均化処理＋炭素との反応）。これにより、炭素被覆ケイ素酸化物粒子を得るとともに、ケイ素酸化物粒子の不均化およびケイ素酸化物粒子表面部の粒子の炭化ケイ素化を図った。 Example 1 Active material particles in which silicon in the surface portion was replaced with silicon carbide were produced under the following conditions. A commercially available silicon monoxide particle (average particle diameter 45 μm) was ground by a ball mill to obtain a powder of average 0.3 μm.
With respect to this powder, sucrose is dissolved in a mixture of water and ethanol in an amount such that 0.3% by mass of carbon is formed when carbonized, and heated to 150 ° C. to remove alcohol and water, Heat treatment was performed at 1100 ° C. for 1 hour in Ar in an electric furnace (disproportionation treatment + reaction with carbon). As a result, carbon-coated silicon oxide particles were obtained, and disproportionation of silicon oxide particles and carbonization of particles on the surface of the silicon oxide particles were achieved.
　次に、表面部を炭化ケイ素化したケイ素酸化物粒子を、以下のような手順でハードカーボンと複合化した。フルフリルアルコール２．４ｇとエタノール２０ｇの混合液に、ケイ素酸化物粒子１．２ｇと黒鉛粉末０．３ｇを加え混練機にて混練処理しスラリー状の試料を作製した。得られたスラリーにフルフリルアルコールの重合触媒となる希塩酸を０．５ｇ加え、室温で放置し乾燥、固化して炭素複合体を得た。得られた炭素複合体を１１００℃で１時間、Ａｒガス雰囲気中にて焼成し、室温まで冷却後、粉砕し２０μｍ径のふるいにかけて複合化負極活物質を得た。実施例１と同様に電極を作製し、粉末Ｘ線回折測定および高分解能電子顕微鏡観察を行うとともに充放電試験を行った。 Next, silicon oxide particles siliconized at the surface portion were complexed with hard carbon in the following procedure. 1.2 g of silicon oxide particles and 0.3 g of graphite powder were added to a mixed solution of 2.4 g of furfuryl alcohol and 20 g of ethanol, and kneaded with a kneader to prepare a slurry sample. 0.5 g of dilute hydrochloric acid as a polymerization catalyst of furfuryl alcohol was added to the obtained slurry, and the mixture was allowed to stand at room temperature, dried and solidified to obtain a carbon complex. The obtained carbon composite was calcined at 1100 ° C. for 1 hour in an Ar gas atmosphere, cooled to room temperature, pulverized, and sieved to a diameter of 20 μm to obtain a composite negative electrode active material. An electrode was prepared in the same manner as in Example 1, and powder X-ray diffraction measurement and high-resolution electron microscopic observation were performed, and a charge / discharge test was performed.
　得られた活物質０．６ｇに平均径３μｍの黒鉛０．１ｇと混合し、ポリイミドを１６質量％となるようにＮ－メチルピロリドン分散媒で調整した溶液に混ぜ、自転・公転ミキサーを用いて混合した。得られたペースト状のスラリーを厚さ１２μｍの銅箔上に塗布して圧延した後、４００℃で２時間、Ａｒガス中にて熱処理した。得られた電極ついて、粉末Ｘ線回折測定および高分解能電子顕微鏡観察を行った。 0.6 g of the obtained active material is mixed with 0.1 g of graphite having an average diameter of 3 μm, mixed with a solution prepared with N-methylpyrrolidone dispersion medium so that the polyimide is 16 mass%, using a rotation / revolution mixer Mixed. The obtained paste-like slurry was applied onto a copper foil with a thickness of 12 μm and rolled, and then heat treated in Ar gas at 400 ° C. for 2 hours. The obtained electrode was subjected to powder X-ray diffraction measurement and high resolution electron microscopy.
（充放電試験）
　次いで前記電極付き銅箔を２０ｍｍ×２０ｍｍサイズに裁断した後、１００℃で１２時間、真空乾燥し、試験電極とした。対極および参照極を金属Ｌｉ、電解液をＬｉＮ（ＣＦ３ＳＯ２）２（１Ｍ）のＥＣ・ＤＥＣ（体積比ＥＣ：ＤＥＣ＝１：２）溶液とした電池をアルゴン雰囲気中で作製し充放電試験を行った。充放電試験の条件は、参照極と試験電極間の電位差０．０１Ｖまで１ｍＡの定電流で充電し、その後定電圧での充電を行った（ＣＣ／ＣＶ充電）。放電は、１ｍＡの定電流で１．５Ｖまで行った（ＣＣ放電）。さらにその後、参照極と試験電極間の電位差０．０１Ｖまで６ｍＡの定電流で充電、その後定電圧で充電し、６ｍＡの定電流で１．５Ｖまで放電するというサイクルを１００回繰り返し、この６ｍＡでの充放電の１回目の放電容量に対する１００回目の放電容量の比を放電容量維持率とした。
 
放電容量維持率（％）＝（１００回目の放電容量）／（１回目の放電容量）×１００
  (Charge and discharge test)
Subsequently, the copper foil with an electrode was cut into a size of 20 mm × 20 mm and vacuum dried at 100 ° C. for 12 hours to obtain a test electrode. A battery in which the counter electrode and the reference electrode are metal Li and the electrolyte is a solution of LiN (CF 3 SO 2 ) 2 (1 M) in EC · DEC (volume ratio EC: DEC = 1: 2) is prepared in argon atmosphere and charged / discharged The test was done. The conditions of the charge / discharge test were charging at a constant current of 1 mA up to a potential difference of 0.01 V between the reference electrode and the test electrode and then charging at a constant voltage (CC / CV charge). Discharge was performed up to 1.5 V at a constant current of 1 mA (CC discharge). Thereafter, the potential difference between the reference electrode and the test electrode is charged at a constant current of 6 mA to 0.01 V, then charged at a constant voltage, and then discharged to 1.5 V at a constant current of 6 mA. This cycle is repeated 100 times. The ratio of the 100th discharge capacity to the first discharge capacity of the charge and discharge was defined as the discharge capacity retention ratio.

Discharge capacity retention rate (%) = (100th discharge capacity) / (first discharge capacity) × 100
　以下の実施例と比較例に関して表１にまとめた。以下の実施例および比較例については実施例１と異なる部分のみ説明し、その他の合成および評価手順については実施例１と同様に行ったので説明を省略する。 The following Examples and Comparative Examples are summarized in Table 1. For the following examples and comparative examples, only portions different from those in Example 1 will be described, and the other synthesis and evaluation procedures are the same as in Example 1 and thus the description will be omitted.
（実施例２）
　実施例１と同様にボールミルで粉砕した一酸化ケイ素粒子をＮ２雰囲気中、１３００℃で１時間加熱処理を行った。得られた熱処理ケイ素酸化物粒子を用い、実施例１と同様の方法で炭素材料と複合化処理を行い、複合化負極活物質を作製した。実施例１と同様に電極を作製し
粉末Ｘ線回折測定および高分解能電子顕微鏡観察を行うとともに充放電試験を行った。 (Example 2)
The silicon monoxide particles crushed by a ball mill in the same manner as in Example 1 were subjected to heat treatment at 1300 ° C. for 1 hour in an N 2 atmosphere. Using the heat-treated silicon oxide particles thus obtained, the composite material was treated with a carbon material in the same manner as in Example 1 to prepare a composite negative electrode active material. An electrode was produced in the same manner as in Example 1, and powder X-ray diffraction measurement and high-resolution electron microscopic observation were performed, and a charge and discharge test was performed.
（実施例３）
　実施例１で作製した複合化粒子を用い、電極化の工程で１μｍサイズのポリスチレン粒子を電極体積の１５％ほどになるように添加した以外はすべて実施例１と同様の方法にて電極を作製した。実施例１と同様の充放電試験を１サイクル行い、試験後に解体して光学顕微鏡による電極の観察を行った。 (Example 3)
An electrode was manufactured in the same manner as in Example 1 except that polystyrene particles of 1 μm in size were added so as to be about 15% of the electrode volume in the step of forming electrodes using the composite particles prepared in Example 1 did. The same charge / discharge test as in Example 1 was carried out one cycle, and after the test, it was disassembled and the electrode was observed with an optical microscope.
（比較例１）
　実施例１と同様に粉砕したケイ素酸化物粒子をＡｒ雰囲気中、１１００℃で１時間加熱して不均化処理を行った。得られた不均化ケイ素酸化物粒子を用い、焼成温度を９００℃とした以外はすべて実施例２と同様の方法で炭素材と複合化処理を行い、複合化負極活物質を作製した。実施例１と同様に電極を作製し、粉末Ｘ線回折測定および高分解能電子顕微鏡観察を行うとともに充放電試験を行った。 (Comparative example 1)
The silicon oxide particles pulverized in the same manner as in Example 1 were subjected to disproportionation treatment by heating at 1100 ° C. for 1 hour in an Ar atmosphere. Using the obtained disproportionated silicon oxide particles, the composite material was treated with a carbon material in the same manner as in Example 2 except that the firing temperature was set to 900 ° C., to prepare a composite negative electrode active material. An electrode was prepared in the same manner as in Example 1, and powder X-ray diffraction measurement and high-resolution electron microscopic observation were performed, and a charge / discharge test was performed.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　実施例１における電極の断面のＴＥＭ観察の結果、炭素質物に覆われたケイ素酸化物粒子と、その内部に２～５ｎｍ程度の複数の結晶性のケイ素ナノ粒子の存在を確認した。さらに、少なくともケイ素酸化物粒子と被覆炭素材との界面付近に、一部がケイ素酸化物側に入り込んだ形で粒子状の炭化ケイ素質粒子が存在することを確認した。 As a result of TEM observation of the cross section of the electrode in Example 1, the presence of silicon oxide particles covered with a carbonaceous material and a plurality of crystalline silicon nanoparticles of about 2 to 5 nm in its inside was confirmed. Furthermore, it was confirmed that particulate silicon carbide particles were present in the form of a portion partially invading the silicon oxide side near at least the interface between the silicon oxide particles and the coated carbon material.
　この結果は、１１００℃の熱処理により、ケイ素酸化物が不均化反応を起こしてケイ素ナノ粒子を析出し、かつケイ素酸化物の表面部に析出したケイ素粒子が周りの炭素と反応して炭化ケイ素に変化したものと考えられる。この炭化ケイ素粒子は、リチウムとは反応せず、体積膨張を抑制するとともに、炭素材と接触することで導電性パスが確保され、サイクル寿命の向上が図られたものと思われる。 The result is that heat treatment at 1100 ° C. causes disproportionation reaction of silicon oxide to precipitate silicon nanoparticles, and silicon particles deposited on the surface of silicon oxide react with surrounding carbon to form silicon carbide It is considered to have changed. The silicon carbide particles do not react with lithium to suppress volume expansion, and contact with the carbon material secures a conductive path, which seems to improve cycle life.
　実施例２では、ケイ素粒子の一部が酸窒化ケイ素（Ｓｉ２ＯＮ２）化しているのが確認された。酸窒化ケイ素は、リチウムとは反応しないが、電子伝導性もイオン導電性もないため、容量においては若干低下している。しかし、サイクル性においては、劣化の進行が遅く、効果が見られている。 In Example 2, it was confirmed that part of the silicon particles was converted to silicon oxynitride (Si 2 ON 2 ). Silicon oxynitride does not react with lithium but has a slight decrease in capacity because it has neither electron conductivity nor ion conductivity. However, in the cycle property, the progress of deterioration is slow and an effect is observed.
　一方、不均化によりケイ素ナノ粒子は析出したが炭素前駆体の焼成温度が低いために炭化ケイ素化が起こっていない比較例１の場合には、初期の容量としては特に差は見られないが、サイクルにおいて、劣化がより速く進行することが分かった。 On the other hand, in the case of Comparative Example 1 in which silicon nanoparticles are precipitated due to disproportionation but the carbonization does not occur because the firing temperature of the carbon precursor is low, no particular difference is seen as the initial capacity. In the cycle, it was found that the degradation progressed faster.
　実施例３では、電極の断面のＳＥＭ観察において、複合粒子の外側に約１μｍサイズの空隙が多数形成されているのが観察された。この１μｍサイズの空隙はポリスチレン粒子が熱分解して生じたものである。空隙の体積は、負極全体の体積に対して、１５％ほどであった。図９に、実施例１（造孔剤無し）と実施例３（造孔剤有り）の１サイクル後の電極の集電体の光学顕微鏡観察写真を示す。造孔を施したものは、通常の試験で見られるような凹凸（シワ）はほとんど見られず、ほぼ平坦な状態であった。また、実施例３の電極は、造孔剤としてのスチレン粒子を用いずに電極を作成した実施例１と比べてサイクル特性においてさらなる改善がみられた。電極密度が低下することでエネルギー密度は若干低くなるが、集電体にシワが形成されなくなったことで、電極の剥離や集電体の破れなどを防ぐことができるようになった。このように、複合体の外側に空隙を形成することで、体積膨張に対する応力緩和が効果的に図られることが分かった。同様な効果が、ポリスチレンと同じく電極の熱処理温度以下で熱分解する有機物を用いても起こることが確認されている。 In Example 3, in SEM observation of the cross section of the electrode, it was observed that many voids of about 1 μm in size were formed on the outside of the composite particles. The 1 μm-size voids are generated by thermal decomposition of polystyrene particles. The volume of the void was about 15% with respect to the volume of the entire negative electrode. FIG. 9 shows an optical microscope observation photograph of the current collector of the electrode after one cycle of Example 1 (without pore former) and Example 3 (with pore former). In the case where the hole was formed, almost no unevenness (wrinkling) as seen in the ordinary test was observed, and it was almost flat. Moreover, the electrode of Example 3 showed further improvement in the cycle characteristics as compared with Example 1 in which the electrode was prepared without using styrene particles as a pore forming agent. Although the energy density is slightly lowered by decreasing the electrode density, peeling of the electrode, breakage of the current collector, and the like can be prevented by forming no wrinkles in the current collector. Thus, it has been found that, by forming a void on the outside of the composite, stress relaxation against volume expansion can be effectively achieved. It has been confirmed that the same effect occurs even when using an organic substance which thermally decomposes below the heat treatment temperature of the electrode as polystyrene does.
　以上、本発明の実施の形態を説明したが、本発明はこれらに限られず、特許請求の範囲に記載の発明の要旨の範疇において様々に変更可能である。また、本発明は、実施段階ではその要旨を逸脱しない範囲で種々に変形することが可能である。さらに、上記実施形態に開示されている複数の構成要素を適宜組み合わせることにより種々の発明を形成できる。 Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications can be made within the scope of the subject matter of the invention described in the claims. Further, the present invention can be variously modified in the implementation stage without departing from the scope of the invention. Furthermore, various inventions can be formed by appropriately combining the plurality of components disclosed in the above embodiments.
１０…活物質、１１…ケイ素ナノ粒子、１２…ケイ素酸化物粒子、１３…リチウムと合金化しない粒子、２０…負極活物質、２１…炭素質物相、１００…非水電解質電池用電極、１０１…負極合剤層、１０２…集電体、１０３…負極活物質、１０４…導電材、１０５…結着剤、２００…非水電解質二次電池、２０１…捲回電極群、２０２…外装材、２０３…負極、２０４…セパレータ、２０５…正極、３００…電池パック、３０１…単電池、３０２…負極端子、３０３…正極端子、３０４…粘着テープ、３０５…組電池、３０６…プリント配線基板、３０７…サーミスタ、３０８…保護回路、３０９…通電用端子、３１０…正極側リード、３１１…正極側コネクタ、３１２…負極側リード、３１３…負極側コネクタ、３１４…配線、３１５…配線、３１６ａ…プラス側配線、３１６ｂ…マイナス側配線、３１７…配線、３１８…保護シート、３１９…収納容器、３２０…蓋
  DESCRIPTION OF SYMBOLS 10 active material, 11 silicon nanoparticle, 12 silicon oxide particle, 13 particle which is not alloyed with lithium 20 negative electrode active material 21 carbonaceous material phase 100 electrode for nonaqueous electrolyte battery 101 Negative electrode mixture layer 102 Current collector 103 Negative electrode active material 104 Conductive material 105 Binder 200 Non-aqueous electrolyte secondary battery 201 Coiled electrode group 202 Exterior material 203 ... Negative electrode 204 separator 205 positive electrode 300 battery pack 301 unit cell 302 negative electrode terminal 303 positive electrode terminal 304 adhesive tape 305 assembled battery 306 printed wiring board 307 thermistor , 308: protection circuit, 309: conduction terminal, 310: positive electrode side lead, 311: positive electrode side connector, 312: negative electrode side lead, 313: negative electrode side connector, 314: wiring, 315: Line, 316a ... plus side wiring, 316b ... minus side wiring, 317 ... wire, 318 ... protective sheet, 319 ... receiving container, 320 ... lid

Claims (9)

  1. 　ケイ素粒子を内部に有するケイ素酸化物を少なくとも含む粒子であり、
    　前記粒子の表層部に炭化ケイ素、窒化ケイ素と酸窒化ケイ素より選ばれる少なくとも一種を含む粒子が担持されていることを特徴とする非水電解質電池用電極活物質。     Particles containing at least silicon oxide having silicon particles inside;
    The electrode active material for a non-aqueous electrolyte battery, wherein particles containing at least one selected from silicon carbide, silicon nitride and silicon oxynitride are supported on the surface layer portion of the particles.
  2. 　前記ケイ素酸化物を含む粒子が、酸化ケイ素相と前記酸化ケイ素相の内部にケイ素相とを含むことを特徴とする請求項１に記載の非水電解質電池用電極活物質。 The electrode active material for a non-aqueous electrolyte battery according to claim 1, wherein the particles containing silicon oxide contain a silicon oxide phase and a silicon phase inside the silicon oxide phase.
  3. 　前記炭化ケイ素、窒化ケイ素と酸窒化ケイ素を含む粒子が、前記ケイ素酸化物の表層部に一部埋没して存在することを特徴とする請求項１に記載の非水電解質電池用電極活物質。 The electrode active material for a non-aqueous electrolyte battery according to claim 1, wherein the particles containing silicon carbide, silicon nitride and silicon oxynitride are partially embedded in the surface layer of the silicon oxide.
  4. 　前記請求項１に記載の非水電解質電池用活物質を炭素質物で被覆してなることを特徴とする非水電解質電池用電極活物質。 An electrode active material for a non-aqueous electrolyte battery, which is obtained by coating the non-aqueous electrolyte battery active material according to claim 1 with a carbonaceous material.
  5. 　集電体と、
    　前記集電体上に、前記請求項１乃至４のいずれか１項に記載の非水電解質電池用電極活物質と、導電助剤と、結着剤を含む電極合剤層とを有することを特徴とする非水電解質二次電池用電極。     Current collector,
    5. Having the electrode active material for a non-aqueous electrolyte battery according to any one of claims 1 to 4, a conductive support agent, and an electrode mixture layer containing a binder on the current collector. An electrode for a non-aqueous electrolyte secondary battery characterized by the present invention.
  6. 　前記電極合剤層の体積に対して、５％以上３０％以下の空隙を前記電極合剤層内に含むことを特徴とする請求項５に記載の非水電解質二次電池用電極。 The electrode for a non-aqueous electrolyte secondary battery according to claim 5, wherein a void of 5% or more and 30% or less with respect to the volume of the electrode mixture layer is included in the electrode mixture layer.
  7. 　前記非水電解質電池用電極活物質の直径が前記電極合剤層１０１の厚みの９０％以上であるものを含み、
    　前記前記電極合剤層１０１の厚みの９０％以上の直径を有する非水電解質電池用電極活物質の個数は、前記電極合剤層に含まれる非水電解質電池用電極活物質の個数の２０％以下であることを特徴とする請求項５に記載の非水電解質二次電池用電極     The electrode active material for a non-aqueous electrolyte battery, including the one having a diameter of 90% or more of the thickness of the electrode mixture layer 101,
    The number of the electrode active material for a non-aqueous electrolyte battery having a diameter of 90% or more of the thickness of the electrode mixture layer 101 is 20% of the number of the electrode active material for a non-aqueous electrolyte battery contained in the electrode mixture layer. It is the following, The electrode for non-aqueous electrolyte secondary batteries of Claim 5 characterized by the above-mentioned.
  8. 　外装材と、
    　前記外装材内に収納された正極と、
    　前記外装材内に前記正極と空間的に離間して、セパレータを介在して収納された前記請求項５に記載の電極を用いた負極と、
    　前記外装材内に充填された非水電解質とを具備することを特徴とする非水電解質二次電池。     Exterior material,
    A positive electrode housed in the exterior material;
    6. The negative electrode using the electrode according to claim 5, which is accommodated in the outer package material spatially separated from the positive electrode and interposed with a separator.
    A non-aqueous electrolyte secondary battery comprising: a non-aqueous electrolyte filled in the outer package.
  9. 　前記請求項８に記載された非水電解質二次電池をセルとして用いた電池パック。 A battery pack using the non-aqueous electrolyte secondary battery according to claim 8 as a cell.
PCT/JP2014/057972 2014-03-24 2014-03-24 Electrode active material for non-aqueous electrolyte cell, electrode for non-aqueous electrolyte secondary cell, non-aqueous electrolyte secondary cell, and cell pack WO2015145522A1 (en)

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CN114436238A (en) * 2021-12-28 2022-05-06 深圳市翔丰华科技股份有限公司 Preparation method of low-expansion silicon-carbon negative electrode material for lithium ion battery

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