WO2017169417A1 - Lithium-ion secondary battery - Google Patents

Lithium-ion secondary battery Download PDF

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Publication number
WO2017169417A1
WO2017169417A1 PCT/JP2017/007310 JP2017007310W WO2017169417A1 WO 2017169417 A1 WO2017169417 A1 WO 2017169417A1 JP 2017007310 W JP2017007310 W JP 2017007310W WO 2017169417 A1 WO2017169417 A1 WO 2017169417A1
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Prior art keywords
positive electrode
active material
electrode active
lithium
negative electrode
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PCT/JP2017/007310
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French (fr)
Japanese (ja)
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清佳 米原
洋介 喜多
敏和 小高
水田　政智
愛佳 木村
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オートモーティブエナジーサプライ株式会社
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Publication of WO2017169417A1 publication Critical patent/WO2017169417A1/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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings, jackets or wrappings of a single cell or a single battery
    • H01M50/102—Primary casings, jackets or wrappings of a single cell or a single battery characterised by their shape or physical structure
    • H01M50/105—Pouches or flexible bags
    • 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
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • 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
    • 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
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a non-aqueous electrolyte battery, particularly a lithium ion secondary battery.
  • Non-aqueous electrolyte batteries have been put into practical use as automobile batteries including hybrid cars and electric cars.
  • Lithium ion secondary batteries are used as such on-vehicle power supply batteries.
  • Lithium ion secondary batteries are required to have various characteristics such as output characteristics, energy density, capacity, lifetime, and high temperature stability.
  • a lithium ion secondary battery includes a wound battery in which a positive electrode, a negative electrode, and a separator are laminated and wound together in a container such as a can together with an electrolytic solution, and a sheet-like material in which the positive electrode, the negative electrode, and the separator are laminated.
  • laminated batteries hereinafter also referred to as “laminate batteries”
  • a laminated battery has a high weight energy density and a high degree of freedom in shape, and is suitable for use as a battery for in-vehicle power supply.
  • Japanese Unexamined Patent Application Publication No. 2009-277397 discloses a laminated nonaqueous secondary battery in which a flat laminated electrode body in which a negative electrode and a positive electrode are laminated via a separator is housed in a laminate container together with a nonaqueous electrolyte.
  • Metal foreign matter may be mixed in the electrolyte of the laminate battery during the battery manufacturing process.
  • the metal foreign matter may be dissolved as metal ions having a positive charge during battery charging, move to the negative electrode side, and precipitate on the negative electrode to form dendrites.
  • Such batteries may not be able to generate the desired voltage due to the deposition of dendrites, so such batteries must be screened prior to shipment.
  • As a screening method for example, a method of measuring a battery voltage by pressurizing a laminated battery is known (Japanese Patent Laid-Open No. 2012-3950).
  • Laminated batteries are screened by measuring the voltage by pressurizing the entire battery surface from the outside of the battery casing.
  • the outer package is swollen, so that even when the battery outer package is pressurized during screening, it may not be uniformly pressurized.
  • a portion of insufficient pressurization due to uneven pressurization tends to occur.
  • a partial battery may be formed between the dendrite and the positive electrode facing it, and the battery outer package is uniform.
  • the battery voltage drop may not be properly measured.
  • the battery that should be removed by screening may remain as an acceptable product.
  • the amount of the electrolytic solution can be reduced to minimize the swelling of the exterior body, but if the amount of the electrolytic solution is reduced, the cycle characteristics of the battery are significantly reduced. There is a fear.
  • the present invention is suitable for screening a laminate type lithium ion secondary battery excellent in cycle characteristics by setting the amount of the electrolyte solution in a certain range in a laminate type battery using a specific positive electrode active material. The purpose is to ensure.
  • a lithium ion secondary battery includes a positive electrode in which a positive electrode active material layer is disposed on a positive electrode current collector, a negative electrode in which a negative electrode active material layer is disposed on a negative electrode current collector, a separator, and an electrolyte solution Is a lithium ion secondary battery including a power generation element including the inside of the exterior body.
  • the positive electrode active material layer is composed of a lithium / nickel composite oxide or a lithium / nickel composite oxide containing 70% by weight or less of the lithium / manganese composite oxide with respect to the weight of the positive electrode active material.
  • the volume of the electrolyte contained in the element is 1.1 to 1.4 times the total value of the volume of pores present in the positive electrode active material layer, the negative electrode active material layer, and the separator, To do.
  • the lithium ion secondary battery of the present invention is a battery with high quality reliability that has excellent cycle characteristics and good detectability by screening.
  • FIG. 1 is a schematic cross-sectional view showing a lithium ion secondary battery according to an embodiment of the present invention.
  • the positive electrode is a thin plate in which a positive electrode active material layer is formed by applying or rolling and drying a mixture of a positive electrode active material, a binder, and, if necessary, a conductive additive on a positive electrode current collector such as a metal foil. Or it is a sheet-like battery member.
  • the negative electrode is a thin plate-like or sheet-like battery member in which a negative electrode active material layer is formed by applying a mixture of a negative electrode active material, a binder, and, if necessary, a conductive additive to a negative electrode current collector.
  • the separator is a film-like battery member for separating the positive electrode and the negative electrode and ensuring the conductivity of lithium ions between the negative electrode and the positive electrode.
  • the electrolytic solution is an electrically conductive solution in which an ionic substance is dissolved in a solvent. In this embodiment, a nonaqueous electrolytic solution can be used in particular.
  • the power generation element including the positive electrode, the negative electrode, the separator, and the electrolytic solution is a unit of the main constituent member of the battery. Usually, the positive electrode and the negative electrode are laminated via the separator, and this laminate is immersed in the electrolytic solution. Has been.
  • the lithium ion secondary battery of the embodiment is configured such that the power generation element is included in the exterior body, and preferably the power generation element is sealed inside the exterior body.
  • sealed means that the power generation element is wrapped with a relatively flexible outer packaging material that can be bent so as not to touch the outside air. That is, the exterior body has a bag shape capable of sealing the power generation element therein.
  • an aluminum laminate sheet in which an aluminum foil and polypropylene or the like are laminated can be used as the exterior body.
  • the positive electrode that can be used in all embodiments includes a positive electrode in which a positive electrode active material layer including a positive electrode active material is disposed on a positive electrode current collector.
  • the positive electrode has a positive electrode active material layer obtained by applying or rolling a mixture of a positive electrode active material, a binder, and optionally a conductive additive to a positive electrode current collector made of a metal foil such as an aluminum foil, and drying. ing.
  • the positive electrode active material layer preferably has a porous shape or microporous shape including pores.
  • the positive electrode active material layer preferably contains a lithium / nickel composite oxide as the positive electrode active material.
  • Lithium-nickel composite oxide is a general formula Li x Ni y Me (1-y) O 2 (where Me is Al, Mn, Na, Fe, Co, Cr, Cu, Zn, Ca, K, It is a transition metal composite oxide containing lithium and nickel, represented by at least one metal selected from the group consisting of Mg and Pb.
  • the positive electrode active material layer can further contain a lithium / manganese composite oxide as a positive electrode active material.
  • a lithium / manganese composite oxide examples include a zigzag layered structure lithium manganate (LiMnO 2 ) and spinel type lithium manganate (LiMn 2 O 4 ).
  • the positive electrode can be produced at a lower cost.
  • the lithium-manganese-based positive electrode active material When the lithium-manganese-based positive electrode active material is included, it is preferably 70% by weight or less, and more preferably 30% by weight or less, based on the weight of the positive electrode active material. If the amount of the lithium-manganese composite oxide contained in the positive electrode active material is too large, a partial battery is likely to be formed between the dendrite derived from a metal foreign substance that can be mixed in the battery and the mixed positive electrode, and battery screening is performed. Sometimes accurate voltage behavior cannot be measured.
  • the positive electrode active material layer may include a lithium nickel manganese cobalt composite oxide having a layered crystal structure represented by the general formula Li x Ni y Co z Mn (1-yz) O 2 as a positive electrode active material.
  • x in the general formula is 1 ⁇ x ⁇ 1.2
  • y and z are positive numbers that satisfy y + z ⁇ 1, and the value of y is 0.5 or less.
  • 1-yz ⁇ 0.4 is desirable.
  • the cost increases and the capacity decreases when the proportion of cobalt increases it is desirable to satisfy z ⁇ y and z ⁇ 1-yz. In order to obtain a high-capacity battery, it is particularly preferable to satisfy y> 1-yz and y> z.
  • Carbon fibers such as carbon nanofibers, carbon blacks such as acetylene black and ketjen black, activated carbon, graphite, mesoporous carbon, fullerenes, carbon nanotubes and other carbon materials as conductive aids optionally used in the positive electrode active material layer Is mentioned.
  • electrode additives generally used for electrode formation such as thickeners, dispersants, and stabilizers, can be appropriately used for the positive electrode active material layer.
  • fluororesins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyvinyl fluoride (PVF), and conductive materials such as polyanilines, polythiophenes, polyacetylenes, and polypyrroles.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVF polyvinyl fluoride
  • conductive materials such as polyanilines, polythiophenes, polyacetylenes, and polypyrroles.
  • Polymer synthetic rubber such as styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), or carboxymethyl cellulose (CMC), xanthan gum, guar gum, Polysaccharides such as pectin can be used.
  • SBR styrene
  • the negative electrode that can be used in all the embodiments includes a negative electrode in which a negative electrode active material layer including a negative electrode active material is disposed on a negative electrode current collector.
  • the negative electrode has a negative electrode active material layer obtained by applying or rolling a mixture of a negative electrode active material, a binder, and optionally a conductive additive to a negative electrode current collector made of a metal foil such as copper foil, and drying. ing.
  • the negative electrode active material layer preferably has a porous shape or microporous shape including pores.
  • the negative electrode active material includes graphite.
  • Graphite is a carbon material of hexagonal hexagonal plate crystal, and is sometimes referred to as graphite or graphite.
  • the graphite is preferably in the form of particles.
  • amorphous carbon may be contained, and in some cases, a mixture of graphite and amorphous carbon may be used.
  • graphite coated with amorphous carbon can be used.
  • amorphous carbon refers to a carbon material that is amorphous as a whole and has a structure in which microcrystals are randomly networked. Further, the amorphous carbon may have a structure partially similar to graphite. Examples of the amorphous carbon include carbon black, coke, activated carbon, carbon fiber, hard carbon, soft carbon, and mesoporous carbon.
  • the amorphous carbon is preferably in the form of particles. When a mixed carbon material containing both graphite particles and amorphous carbon particles is used as the negative electrode active material, the battery regeneration performance is improved.
  • graphite particles coated with amorphous carbon can also be used.
  • Examples of conductive auxiliary agents used in the negative electrode active material layer include carbon fibers such as carbon nanofibers, carbon blacks such as acetylene black and ketjen black, carbon materials such as activated carbon, mesoporous carbon, fullerenes, and carbon nanotubes. It is done.
  • electrode additives generally used for electrode formation such as a thickener, a dispersant, and a stabilizer, can be appropriately used for the negative electrode active material layer.
  • fluororesins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyvinyl fluoride (PVF), and conductive materials such as polyanilines, polythiophenes, polyacetylenes, and polypyrroles.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PVF polyvinyl fluoride
  • conductive materials such as polyanilines, polythiophenes, polyacetylenes, and polypyrroles.
  • Polymer synthetic rubber such as styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), or carboxymethyl cellulose (CMC), xanthan gum, guar gum, Polysaccharides such as pectin can be used.
  • SBR styrene
  • the positive electrode and negative electrode that can be used in all the embodiments are those in which the electrode active material layer containing the positive electrode active material or the negative electrode active material described above is disposed on the electrode current collector.
  • the thickness of the electrode active material layer is preferably 25 to 100 ⁇ m per side. If the thickness of the electrode active material layer is too small, there is an inconvenience that it is difficult to form a uniform electrode active material layer. On the other hand, if the thickness of the electrode active material layer is too large, the charge / discharge performance at a high rate decreases. There can be.
  • the separator used in all the embodiments is composed of an olefin resin layer.
  • the olefin resin layer is a layer composed of polyolefin obtained by polymerizing or copolymerizing ⁇ -olefin such as ethylene, propylene, butene, pentene, hexene and the like.
  • a structure having pores that are closed when the battery temperature rises that is, a layer composed of a porous or microporous polyolefin is preferable. Since the olefin resin layer has such a structure, even if the battery temperature rises, the separator is closed (shuts down), and the ion flow can be cut off.
  • the separator may optionally have a heat-resistant fine particle layer.
  • the heat-resistant fine particle layer provided to prevent overheating of the battery is composed of inorganic fine particles having a heat resistance of 150 ° C. or higher and stable to an electrochemical reaction.
  • inorganic fine particles inorganic oxides such as silica, alumina ( ⁇ -alumina, ⁇ -alumina, ⁇ -alumina), iron oxide, titanium oxide, barium titanate, zirconium oxide; boehmite, zeolite, apatite, kaolin, Mention may be made of minerals such as spinel, mica and mullite.
  • a ceramic separator having a heat-resistant layer can also be used.
  • the electrolyte used in all the embodiments of the present specification is a non-aqueous electrolyte and is dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), di-n-propyl carbonate, di- A mixture containing a chain carbonate such as t-propyl carbonate, di-n-butyl carbonate, di-isobutyl carbonate, or di-t-butyl carbonate and a cyclic carbonate such as propylene carbonate (PC) or ethylene carbonate (EC).
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • di-n-propyl carbonate di- A mixture containing a chain carbonate such as t-propyl carbonate, di-n-butyl carbonate, di-isobutyl carbonate, or di-t-butyl carbonate and a cyclic carbonate such as propy
  • the electrolytic solution is obtained by dissolving a lithium salt such as lithium hexafluorophosphate (LiPF 6 ), lithium borofluoride (LiBF 4 ), or lithium perchlorate (LiClO 4 ) in such a carbonate mixture.
  • a lithium salt such as lithium hexafluorophosphate (LiPF 6 ), lithium borofluoride (LiBF 4 ), or lithium perchlorate (LiClO 4 ) in such a carbonate mixture.
  • the electrolytic solution may contain a cyclic carbonate compound as an additive.
  • a cyclic carbonate compound is mentioned as a cyclic carbonate used as an additive.
  • Vinylene carbonate is a compound that can form a protective film on the positive electrode and the negative electrode in the process of charging and discharging the battery.
  • These cyclic carbonates are also compounds that form a protective film on the positive electrode and the negative electrode in the charge and discharge process of the battery.
  • halogen-containing cyclic carbonate compound examples include fluoroethylene carbonate (FEC), difluoroethylene carbonate, trifluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, and trichloroethylene carbonate.
  • Fluoroethylene carbonate which is a cyclic carbonate compound having a halogen and an unsaturated bond, is particularly preferably used.
  • vinylene carbonate and fluoroethylene carbonate can prevent attacks on positive electrode active materials containing lithium / nickel composite oxides by sulfur-containing compounds such as the following disulfonic acid compounds or disulfonic acid ester compounds. Known as a compound.
  • the electrolytic solution may further contain a disulfonic acid compound as an additive.
  • the disulfonic acid compound is a compound having two sulfo groups in one molecule, and includes a disulfonate compound in which the sulfo group forms a salt with a metal ion, or a disulfonate compound in which the sulfo group forms an ester. .
  • One or two of the sulfo groups of the disulfonic acid compound may form a salt with the metal ion or may be in an anionic state.
  • disulfonic acid compounds include methanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,3-propanedisulfonic acid, 1,4-butanedisulfonic acid, benzenedisulfonic acid, naphthalenedisulfonic acid, biphenyldisulfonic acid, and these And salts (lithium methanedisulfonate, lithium 1,3-ethanedisulfonate, etc.) and anions thereof (methanedisulfonate anion, 1,3-ethanedisulfonate anion, etc.).
  • Disulfonic acid compounds include disulfonic acid ester compounds, such as methanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,3-propanedisulfonic acid, 1,4-butanedisulfonic acid, benzenedisulfonic acid, naphthalenedisulfonic acid, Alternatively, chain disulfonic acid esters such as alkyl diesters or aryl diesters of biphenyl disulfonic acid; and cyclic disulfonic acid esters such as methylenemethane disulfonic acid ester, ethylenemethane disulfonic acid ester, and propylene methane disulfonic acid ester are preferably used. Methylenemethane disulfonate (MMDS) is particularly preferably used.
  • MMDS Methylenemethane disulfonate
  • the above positive electrode and negative electrode can be laminated via a separator, and this can be enclosed together with the above electrolytic solution in the exterior body to form a laminated lithium ion secondary battery.
  • Any material can be used as the exterior body as long as it does not allow the electrolytic solution to be leached to the outside, but an aluminum laminate that is a laminate of an aluminum foil and a polymer such as polyethylene or polypropylene can be used.
  • the amount of the electrolytic solution is 1.1 to 1. with respect to the total volume of pores existing in the laminate composed of the positive electrode active material layer, the negative electrode active material layer, and the separator. It is preferably 4 times. If the amount of the electrolytic solution is too small, the cycle characteristics of the battery may be deteriorated. If the amount of the electrolytic solution is too large, the laminate-type battery may swell, and screening for measuring the voltage in a state where the battery is pressurized may be performed. May not be done properly.
  • FIG. 1 shows an example of a cross-sectional view of a lithium ion secondary battery.
  • the lithium ion secondary battery 10 includes a negative electrode current collector 11, a negative electrode active material layer 13, a separator 17, a positive electrode current collector 12, and a positive electrode active material layer 15 as main components.
  • the negative electrode active material layer 13 is provided on both surfaces of the negative electrode current collector 11 and the positive electrode active material layer 15 is provided on both surfaces of the positive electrode current collector 12, but only on one side of each current collector.
  • An active material layer can also be formed.
  • the negative electrode current collector 11, the positive electrode current collector 12, the negative electrode active material layer 13, the positive electrode active material layer 15, and the separator 17 are constituent units of one battery, that is, a power generation element (unit cell 19 in the figure). A plurality of such unit cells 19 are stacked via the separator 17.
  • the extending portion extending from each negative electrode current collector 11 is collectively bonded onto the negative electrode lead 25, and the extending portion extending from each positive electrode current collector 12 is collectively bonded to the positive electrode lead 27.
  • An aluminum plate is preferably used as the positive electrode lead, and a copper plate is preferably used as the negative electrode lead, and in some cases, it may have a partial coating with another metal (for example, nickel, tin, solder) or a polymer material.
  • the positive electrode lead and the negative electrode lead are welded to the positive electrode and the negative electrode, respectively.
  • a battery formed by laminating a plurality of single cells in this manner is packaged by an outer package 29 so that the welded negative electrode lead 25 and positive electrode lead 27 are drawn out to the outside.
  • An electrolytic solution 31 is injected into the exterior body 29.
  • the exterior body 29 has a shape in which the peripheral edge portion is heat-sealed.
  • the areas of the positive electrode and the negative electrode are preferably 75 cm 2 or more.
  • the area of both electrodes being 75 cm 2 or more means that the lithium ion secondary battery of the present embodiment is a battery having a relatively large area.
  • the above screening can be more difficult.
  • appropriate screening can be performed without deteriorating the cycle characteristics of the battery.
  • lithium / manganese composite oxide having a spinel structure Li 1 .1 Mn 1.9 O 4 powder
  • carbon black powder CB
  • PVDF made by Kureha, # 7200
  • oxalic anhydride molecular weight 90
  • oxalic anhydride molecular weight 90
  • oxalic anhydride molecular weight 90
  • these materials were disperse
  • the obtained slurry was applied on a 20 ⁇ m thick aluminum foil serving as a positive electrode current collector so that the weight after drying was 20 mg / cm 2 per side.
  • the electrode was heated at 125 ° C. for 10 minutes to evaporate NMP, thereby forming a positive electrode active material layer.
  • the electrode was pressed so that the porosity of the positive electrode active material layer was 25%, and a positive electrode in which a positive electrode active material layer having a thickness of 63 ⁇ m was applied on one surface of the positive electrode current collector was produced.
  • the electrode was pressed so that the porosity of the negative electrode active material layer was 33%, and a negative electrode in which a negative electrode active material layer having a thickness of 62 ⁇ m was applied on one surface of the negative electrode current collector was produced.
  • ⁇ Separator> A ceramic separator composed of a heat-resistant fine particle layer using boehmite as heat-resistant fine particles and an olefin-based resin layer made of polypropylene and polyethylene having a thickness of 25 ⁇ m and a porosity of 55% was used.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • LiPF 6 lithium hexafluorophosphate
  • the positive electrode and the negative electrode produced as described above were cut into a rectangular shape having a size of 220 mm ⁇ 190 mm so as to leave a current collector extension portion to which each active material was not applied to prepare a positive electrode plate and a negative electrode plate.
  • a 20-layer electrode stack was obtained by arranging the negative electrode plate and the positive electrode plate on both sides of the separator so that both active material layers overlapped with the separator therebetween.
  • the inner side end (one end part) of the negative electrode terminal was joined with the negative electrode collector extension part of the negative electrode plate.
  • the inner end (one end) of the positive electrode terminal was joined to the positive electrode current collector extension of the positive electrode plate.
  • This electrode plate laminate was wrapped with two aluminum laminate films serving as an outer package, and the surrounding four sides were bonded together by thermal fusion, leaving only relatively small filling holes. Subsequently, the electrolyte solution was injected from the filling height so that the volume of the electrolyte solution was as shown in Table 1 during the screening detectability test to be performed later. One side of the four sides was heat-sealed with the aluminum laminate film with the positive electrode terminal and the negative electrode terminal pulled out. The distance between the heat-sealed portion and the electrode plate laminate was 15 mm at the terminal lead-out side and 5 mm at the other sides.
  • ⁇ Porosity of positive electrode, negative electrode, separator> The porosity of the electrode was calculated from the true density of the material, the member thickness, the coating amount, and the mixing ratio.
  • the porosity of the separator was calculated from the true density of the material and the member thickness.
  • ⁇ Cycle characteristic test> The battery manufactured as described above is charged under a temperature of 45 ° C., charging: 1 C current, constant current constant voltage charging at an upper limit voltage of 4.15 V, discharging: constant current discharging at the end of 1 C current, lower limit voltage of 2.5 V The discharge cycle was repeated 1000 times. The discharge capacity retention rate (%) after 1000 cycles was measured.
  • the same test is performed for a battery that does not fix copper foil cutting waste, and the amount of voltage drop is calculated. If the voltage drop amount of the battery with copper foil cutting waste fixed is significantly large, this battery is marked as “detectable”. evaluated. On the other hand, when there was no significant difference in voltage drop between the battery that did not fix the copper foil cutting waste and the battery that did not fix the copper foil, this battery was evaluated as “undetectable”.
  • Table 1 shows the results of the above evaluations on the stacked lithium ion secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 3.
  • the numerical value of the cycle characteristics in Table 1 is a relative value with respect to the value of the post-cycle discharge capacity retention rate (%) of the battery of Comparative Example 1 being 100.
  • the batteries according to the examples using the positive electrode active material in which the ratio of the lithium-manganese composite oxide satisfies the scope of the present invention and maintaining the abundance of the electrolyte in a predetermined range are all subjected to foreign matter screening by pressurization. Contamination could be detected.
  • the battery according to the example also had good cycle characteristics.
  • the battery of Comparative Example 1 with a small amount of electrolyte solution was detectable by screening, but the battery of Comparative Example 2 with a poor amount of cycle characteristics and a large amount of electrolyte solution could be detected by screening. There wasn't.
  • the battery according to Comparative Example 3 using the positive electrode active material having a large proportion of the lithium / manganese composite oxide could not be detected by screening.
  • Example of this invention was described, the said Example was only an example of Embodiment of this invention, and in the meaning which limits the technical scope of this invention to specific embodiment or a specific structure. Absent.

Abstract

The purpose of the present invention is to provide a laminate-type battery employing a specific positive electrode active material, wherein the fluid volume of an electrolytic solution is kept within a certain range so as to enable screening to be performed appropriately and reliably on the laminate-type lithium-ion secondary battery having an excellent cycle characteristic. The present invention relates to a lithium-ion secondary battery which includes, within an external package, a power generation element comprising: a positive electrode in which a positive electrode active material layer is disposed to a positive electrode collector; a negative electrode in which a negative electrode active material layer is disposed to a negative electrode collector; a separator; and an electrolytic solution. The positive electrode active material layer is characterized by comprising a lithium-nickel-based composite oxide or a lithium-nickel-based composite oxide that contains a lithium-manganese-based composite oxide in an amount not more than 70 wt% with respect to the weight of the positive electrode active material, and characterized in that the volume of the electrolytic solution included in the power generation element equals 1.1-1.4 times the total volume of void present in the positive electrode active material layer, the negative electrode active material layer, and the separator.

Description

リチウムイオン二次電池Lithium ion secondary battery
　本発明は、非水電解質電池、特にリチウムイオン二次電池に関する。 The present invention relates to a non-aqueous electrolyte battery, particularly a lithium ion secondary battery.
　非水電解質電池は、ハイブリッド自動車や電気自動車等を含む自動車用電池として実用化されている。このような車載電源用電池としてリチウムイオン二次電池が使用されている。リチウムイオン二次電池は、出力特性、エネルギー密度、容量、寿命、高温安定性等の種々の特性を併せ持つことが要求されている。 Non-aqueous electrolyte batteries have been put into practical use as automobile batteries including hybrid cars and electric cars. Lithium ion secondary batteries are used as such on-vehicle power supply batteries. Lithium ion secondary batteries are required to have various characteristics such as output characteristics, energy density, capacity, lifetime, and high temperature stability.
　リチウムイオン二次電池には、正極、負極およびセパレータを積層して巻回したものを、電解液と共に缶などの容器に封入した巻回型電池と、正極、負極およびセパレータを積層したシート状物を、電解液と共に、比較的柔軟な外装体内部に封じ込めた積層型電池（以下、「ラミネート型電池」とも称する。）がある。積層型電池は、重量エネルギー密度が高く、形状の自由度も高いため、車載電源用電池としての使用に適している。 A lithium ion secondary battery includes a wound battery in which a positive electrode, a negative electrode, and a separator are laminated and wound together in a container such as a can together with an electrolytic solution, and a sheet-like material in which the positive electrode, the negative electrode, and the separator are laminated. Are laminated batteries (hereinafter also referred to as “laminate batteries”) encapsulated in a relatively flexible outer package together with the electrolyte. A laminated battery has a high weight energy density and a high degree of freedom in shape, and is suitable for use as a battery for in-vehicle power supply.
　たとえば、特開２００９－２７７３９７号には、負極および正極をセパレータを介して積層した平板状積層電極体を、非水電解質とともにラミネート容器に収容したラミネート型非水二次電池が開示されている。 For example, Japanese Unexamined Patent Application Publication No. 2009-277397 discloses a laminated nonaqueous secondary battery in which a flat laminated electrode body in which a negative electrode and a positive electrode are laminated via a separator is housed in a laminate container together with a nonaqueous electrolyte.
　ラミネート型電池の電解液中には、電池製造工程において金属異物が紛れ込むことがある。この金属異物は、電池充電中にプラスの電荷を有する金属イオンとなって溶解し、負極側に移動し、負極に析出してデンドライトを形成することがある。このデンドライトの析出が原因で電池が所望の電圧を発生できない場合があるため、このような電池は、出荷に先立ちスクリーニングしておく必要がある。スクリーニング方法として、たとえば、ラミネート型電池を加圧して電池電圧を測定する方法が知られている（特開２０１２－３９５０号）。 金属 Metal foreign matter may be mixed in the electrolyte of the laminate battery during the battery manufacturing process. The metal foreign matter may be dissolved as metal ions having a positive charge during battery charging, move to the negative electrode side, and precipitate on the negative electrode to form dendrites. Such batteries may not be able to generate the desired voltage due to the deposition of dendrites, so such batteries must be screened prior to shipment. As a screening method, for example, a method of measuring a battery voltage by pressurizing a laminated battery is known (Japanese Patent Laid-Open No. 2012-3950).
　ラミネート型電池のスクリーニングは、電池の外装体の外側から電池全面を加圧して電圧を測定することにより行う。外装体内部の電解液量が多いと、外装体に膨れが生じるため、スクリーニングの際に電池外装体を加圧しても均一に加圧できないことがある。特に、面積の広いラミネート型電池のスクリーニングにおいては、不均一な加圧による加圧不足の箇所が生じやすい。一方、ラミネート型電池の内部で金属異物が原因のデンドライトが形成されているにもかかわらず、このデンドライトと対向する正極との間で部分電池が形成されることがあり、電池外装体が均一に加圧できないことと相まって、電池電圧の低下を適切に測定できないことがある。このように、金属異物の存在が見逃されると、本来はスクリーニングにより除去されるべき電池が合格品として残留してしまうことがあった。このような事態を回避するために、外装体の膨れを最低限にすべく電解液の液量を少なくすることもできるが、電解液の液量を減じると、電池のサイクル特性が著しく低下するおそれがある。 ス ク リ ー ニ ン グ Laminated batteries are screened by measuring the voltage by pressurizing the entire battery surface from the outside of the battery casing. When the amount of the electrolytic solution inside the outer package is large, the outer package is swollen, so that even when the battery outer package is pressurized during screening, it may not be uniformly pressurized. In particular, in the screening of a laminate type battery having a large area, a portion of insufficient pressurization due to uneven pressurization tends to occur. On the other hand, despite the fact that dendrites due to metallic foreign matter are formed inside the laminate type battery, a partial battery may be formed between the dendrite and the positive electrode facing it, and the battery outer package is uniform. In combination with the inability to pressurize, the battery voltage drop may not be properly measured. As described above, when the presence of the metal foreign object is overlooked, the battery that should be removed by screening may remain as an acceptable product. In order to avoid such a situation, the amount of the electrolytic solution can be reduced to minimize the swelling of the exterior body, but if the amount of the electrolytic solution is reduced, the cycle characteristics of the battery are significantly reduced. There is a fear.
　そこで、本発明は、特定の正極活物質を用いたラミネート型電池において、電解液の液量を一定の範囲とすることにより、サイクル特性に優れたラミネート型リチウムイオン二次電池のスクリーニングを適切かつ確実に行うことを目的とする。 Therefore, the present invention is suitable for screening a laminate type lithium ion secondary battery excellent in cycle characteristics by setting the amount of the electrolyte solution in a certain range in a laminate type battery using a specific positive electrode active material. The purpose is to ensure.
　本発明の実施形態におけるリチウムイオン二次電池は、正極活物質層が正極集電体に配置された正極と、負極活物質層が負極集電体に配置された負極と、セパレータと、電解液と、を含む発電要素を、外装体内部に含むリチウムイオン二次電池である。ここで正極活物質層はリチウム・ニッケル系複合酸化物、または正極活物質の重量に対して７０重量％以下のリチウム・マンガン系複合酸化物を含むリチウム・ニッケル系複合酸化物から構成され、発電要素中に含まれる電解液の体積は、正極活物質層、負極活物質層およびセパレータに存在する空孔の体積の合計の値に対して１．１～１．４倍であることを特徴とする。 A lithium ion secondary battery according to an embodiment of the present invention includes a positive electrode in which a positive electrode active material layer is disposed on a positive electrode current collector, a negative electrode in which a negative electrode active material layer is disposed on a negative electrode current collector, a separator, and an electrolyte solution Is a lithium ion secondary battery including a power generation element including the inside of the exterior body. Here, the positive electrode active material layer is composed of a lithium / nickel composite oxide or a lithium / nickel composite oxide containing 70% by weight or less of the lithium / manganese composite oxide with respect to the weight of the positive electrode active material. The volume of the electrolyte contained in the element is 1.1 to 1.4 times the total value of the volume of pores present in the positive electrode active material layer, the negative electrode active material layer, and the separator, To do.
　本発明のリチウムイオン二次電池は、サイクル特性に優れ、かつスクリーニングによる検出性が良好な、品質信頼性の高い電池である。 The lithium ion secondary battery of the present invention is a battery with high quality reliability that has excellent cycle characteristics and good detectability by screening.
図１は、本発明の一の実施形態のリチウムイオン二次電池を表す模式断面図である。FIG. 1 is a schematic cross-sectional view showing a lithium ion secondary battery according to an embodiment of the present invention.
　本発明の実施形態を以下に説明する。実施形態において正極とは、正極活物質と、バインダーと、必要な場合導電助剤との混合物を金属箔等の正極集電体に塗布または圧延および乾燥して正極活物質層を形成した薄板状あるいはシート状の電池部材である。負極とは、負極活物質と、バインダーと、必要な場合導電助剤との混合物を負極集電体に塗布して負極活物質層を形成した薄板状あるいはシート状の電池部材である。セパレータとは、正極と負極とを隔離して負極・正極間のリチウムイオンの伝導性を確保するための膜状の電池部材である。電解液とは、イオン性物質を溶媒に溶解させた電気伝導性のある溶液のことであり、本実施形態においては特に非水電解液を用いることができる。正極と負極とセパレータと電解液とを含む発電要素とは、電池の主構成部材の一単位であり、通常、正極と負極とがセパレータを介して積層されて、この積層物が電解液に浸漬されている。 Embodiments of the present invention will be described below. In the embodiment, the positive electrode is a thin plate in which a positive electrode active material layer is formed by applying or rolling and drying a mixture of a positive electrode active material, a binder, and, if necessary, a conductive additive on a positive electrode current collector such as a metal foil. Or it is a sheet-like battery member. The negative electrode is a thin plate-like or sheet-like battery member in which a negative electrode active material layer is formed by applying a mixture of a negative electrode active material, a binder, and, if necessary, a conductive additive to a negative electrode current collector. The separator is a film-like battery member for separating the positive electrode and the negative electrode and ensuring the conductivity of lithium ions between the negative electrode and the positive electrode. The electrolytic solution is an electrically conductive solution in which an ionic substance is dissolved in a solvent. In this embodiment, a nonaqueous electrolytic solution can be used in particular. The power generation element including the positive electrode, the negative electrode, the separator, and the electrolytic solution is a unit of the main constituent member of the battery. Usually, the positive electrode and the negative electrode are laminated via the separator, and this laminate is immersed in the electrolytic solution. Has been.
　実施形態のリチウムイオン二次電池は、外装体の内部に該発電要素が含まれて成り、好ましくは、発電要素は該外装体内部に封止されている。封止されているとは、発電要素が外気に触れないように、折り曲げが可能な比較的柔軟な外装体材料により包まれていることを意味する。すなわち外装体は、発電要素をその内部に封止することが可能な袋形状をしている。外装体として、アルミニウム箔とポリプロピレン等を積層したアルミニウムラミネートシートを使用することができる。 The lithium ion secondary battery of the embodiment is configured such that the power generation element is included in the exterior body, and preferably the power generation element is sealed inside the exterior body. The term “sealed” means that the power generation element is wrapped with a relatively flexible outer packaging material that can be bent so as not to touch the outside air. That is, the exterior body has a bag shape capable of sealing the power generation element therein. As the exterior body, an aluminum laminate sheet in which an aluminum foil and polypropylene or the like are laminated can be used.
　すべての実施形態において用いることができる正極は、正極活物質を含む正極活物質層が正極集電体に配置された正極を含む。好ましくは、正極は、正極活物質、バインダーおよび場合により導電助剤の混合物をアルミニウム箔などの金属箔からなる正極集電体に塗布または圧延し、乾燥して得た正極活物質層を有している。正極活物質層は、空孔を含む多孔質形状または微孔質形状のものであることが好ましい。各実施形態において、正極活物質層は、好ましくはリチウム・ニッケル系複合酸化物を正極活物質として含む。リチウム・ニッケル系複合酸化物とは、一般式ＬｉｘＮｉｙＭｅ（１－ｙ）Ｏ２（ここでＭｅは、Ａｌ、Ｍｎ、Ｎａ、Ｆｅ、Ｃｏ、Ｃｒ、Ｃｕ、Ｚｎ、Ｃａ、Ｋ、Ｍｇ、およびＰｂからなる群より選択される、少なくとも１種以上の金属である。）で表される、リチウムとニッケルとを含有する遷移金属複合酸化物のことである。 The positive electrode that can be used in all embodiments includes a positive electrode in which a positive electrode active material layer including a positive electrode active material is disposed on a positive electrode current collector. Preferably, the positive electrode has a positive electrode active material layer obtained by applying or rolling a mixture of a positive electrode active material, a binder, and optionally a conductive additive to a positive electrode current collector made of a metal foil such as an aluminum foil, and drying. ing. The positive electrode active material layer preferably has a porous shape or microporous shape including pores. In each embodiment, the positive electrode active material layer preferably contains a lithium / nickel composite oxide as the positive electrode active material. Lithium-nickel composite oxide is a general formula Li x Ni y Me (1-y) O 2 (where Me is Al, Mn, Na, Fe, Co, Cr, Cu, Zn, Ca, K, It is a transition metal composite oxide containing lithium and nickel, represented by at least one metal selected from the group consisting of Mg and Pb.
　正極活物質層は、さらにリチウム・マンガン系複合酸化物を正極活物質として含むことができる。リチウム・マンガン系複合酸化物は、たとえばジグザグ層状構造のマンガン酸リチウム（ＬｉＭｎＯ２）、スピネル型マンガン酸リチウム（ＬｉＭｎ２Ｏ４）等を挙げることができる。リチウム・マンガン系複合酸化物を併用することで、より安価に正極を作製することができる。特に、過充電状態での結晶構造の安定度の点で優れるスピネル型のマンガン酸リチウム（ＬｉＭｎ２Ｏ４）を用いることが好ましい。リチウム・マンガン系正極活物質を含む場合、正極活物質の重量に対して７０重量％以下であることが好ましく、３０重量％以下であることがさらに好ましい。正極活物質中に含まれるリチウム・マンガン系複合酸化物の量が多すぎると、電池内に混入しうる金属異物由来のデンドライトと混合正極との間に部分電池が形成されやすくなり、電池のスクリーニング時に正確な電圧挙動が計測できなくなる場合がある。 The positive electrode active material layer can further contain a lithium / manganese composite oxide as a positive electrode active material. Examples of the lithium / manganese composite oxide include a zigzag layered structure lithium manganate (LiMnO 2 ) and spinel type lithium manganate (LiMn 2 O 4 ). By using a lithium-manganese composite oxide in combination, the positive electrode can be produced at a lower cost. In particular, it is preferable to use spinel type lithium manganate (LiMn 2 O 4 ) which is excellent in terms of stability of the crystal structure in an overcharged state. When the lithium-manganese-based positive electrode active material is included, it is preferably 70% by weight or less, and more preferably 30% by weight or less, based on the weight of the positive electrode active material. If the amount of the lithium-manganese composite oxide contained in the positive electrode active material is too large, a partial battery is likely to be formed between the dendrite derived from a metal foreign substance that can be mixed in the battery and the mixed positive electrode, and battery screening is performed. Sometimes accurate voltage behavior cannot be measured.
　正極活物質層は、特に、一般式ＬｉｘＮｉｙＣｏｚＭｎ（１－ｙ－ｚ）Ｏ２で表される層状結晶構造を有するリチウムニッケルマンガンコバルト複合酸化物を正極活物質として含むことが好ましい。ここで、一般式中のｘは１≦ｘ≦１．２であり、ｙおよびｚはｙ＋ｚ＜１を満たす正の数であり、ｙの値が０．５以下である。なお、マンガンの割合が大きくなると単一相の複合酸化物が合成されにくくなるため、１－ｙ－ｚ≦０．４とすることが望ましい。また、コバルトの割合が大きくなると高コストとなり容量も減少するため、ｚ＜ｙ、ｚ＜１－ｙ－ｚとすることが望ましい。高容量の電池を得るためには、ｙ＞１－ｙ－ｚ、ｙ＞ｚとすることが特に好ましい。 In particular, the positive electrode active material layer may include a lithium nickel manganese cobalt composite oxide having a layered crystal structure represented by the general formula Li x Ni y Co z Mn (1-yz) O 2 as a positive electrode active material. preferable. Here, x in the general formula is 1 ≦ x ≦ 1.2, y and z are positive numbers that satisfy y + z <1, and the value of y is 0.5 or less. Note that when the proportion of manganese increases, it becomes difficult to synthesize a single-phase composite oxide, so 1-yz ≦ 0.4 is desirable. Further, since the cost increases and the capacity decreases when the proportion of cobalt increases, it is desirable to satisfy z <y and z <1-yz. In order to obtain a high-capacity battery, it is particularly preferable to satisfy y> 1-yz and y> z.
　正極活物質層に場合により用いられる導電助剤として、カーボンナノファイバー等のカーボン繊維、アセチレンブラック、ケッチェンブラック等のカーボンブラック、活性炭、黒鉛、メゾポーラスカーボン、フラーレン類、カーボンナノチューブ等の炭素材料が挙げられる。その他、正極活物質層には増粘剤、分散剤、安定剤等の、電極形成のために一般的に用いられる電極添加剤を適宜使用することができる。 Carbon fibers such as carbon nanofibers, carbon blacks such as acetylene black and ketjen black, activated carbon, graphite, mesoporous carbon, fullerenes, carbon nanotubes and other carbon materials as conductive aids optionally used in the positive electrode active material layer Is mentioned. In addition, electrode additives generally used for electrode formation, such as thickeners, dispersants, and stabilizers, can be appropriately used for the positive electrode active material layer.
　正極活物質層に用いられるバインダーとして、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニル（ＰＶＦ）等のフッ素樹脂、ポリアニリン類、ポリチオフェン類、ポリアセチレン類、ポリピロール類等の導電性ポリマー、スチレンブタジエンラバー（ＳＢＲ）、ブタジエンラバー（ＢＲ）、クロロプレンラバー（ＣＲ）、イソプレンラバー（ＩＲ）、アクリロニトリルブタジエンラバー（ＮＢＲ）等の合成ゴム、あるいはカルボキシメチルセルロース（ＣＭＣ）、キサンタンガム、グアーガム、ペクチン等の多糖類を用いることができる。 As a binder used for the positive electrode active material layer, fluororesins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyvinyl fluoride (PVF), and conductive materials such as polyanilines, polythiophenes, polyacetylenes, and polypyrroles. Polymer, synthetic rubber such as styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), or carboxymethyl cellulose (CMC), xanthan gum, guar gum, Polysaccharides such as pectin can be used.
　すべての実施形態において用いることができる負極は、負極活物質を含む負極活物質層が負極集電体に配置された負極を含む。好ましくは、負極は、負極活物質、バインダーおよび場合により導電助剤の混合物を銅箔などの金属箔からなる負極集電体に塗布または圧延し、乾燥して得た負極活物質層を有している。負極活物質層は、空孔を含む多孔質形状または微孔質形状のものであることが好ましい。各実施形態において、負極活物質が、黒鉛を含む。特に負極活物質層に黒鉛が含まれると、電池の残容量（ＳＯＣ）が低いときにも電池の出力を向上させることができるというメリットがある。黒鉛は、六方晶系六角板状結晶の炭素材料であり、石墨、グラファイト等と称されることがある。黒鉛は粒子の形態であることが好ましい。 The negative electrode that can be used in all the embodiments includes a negative electrode in which a negative electrode active material layer including a negative electrode active material is disposed on a negative electrode current collector. Preferably, the negative electrode has a negative electrode active material layer obtained by applying or rolling a mixture of a negative electrode active material, a binder, and optionally a conductive additive to a negative electrode current collector made of a metal foil such as copper foil, and drying. ing. The negative electrode active material layer preferably has a porous shape or microporous shape including pores. In each embodiment, the negative electrode active material includes graphite. In particular, when graphite is contained in the negative electrode active material layer, there is an advantage that the output of the battery can be improved even when the remaining capacity (SOC) of the battery is low. Graphite is a carbon material of hexagonal hexagonal plate crystal, and is sometimes referred to as graphite or graphite. The graphite is preferably in the form of particles.
　また、負極活物質として、非晶質炭素が含まれていてもよく、場合により黒鉛と非晶質炭素との混合物を用いてもよい。あるいは、非晶質炭素で被覆された黒鉛を用いることもできる。ここで非晶質炭素とは、微結晶がランダムにネットワークした構造をとった、全体として非晶質である炭素材料のことである。さらに非晶質炭素は、部分的に黒鉛に類似する構造を有していてもよい。非晶質炭素として、カーボンブラック、コークス、活性炭、カーボンファイバー、ハードカーボン、ソフトカーボン、メソポーラスカーボン等が挙げられる。非晶質炭素は粒子の形状をしていることが好ましい。黒鉛粒子と非晶質炭素粒子とをともに含む混合炭素材料を負極活物質として用いると、電池の回生性能が向上する。炭素材料として、非晶質炭素で被覆された黒鉛粒子を用いることもできる。 Further, as the negative electrode active material, amorphous carbon may be contained, and in some cases, a mixture of graphite and amorphous carbon may be used. Alternatively, graphite coated with amorphous carbon can be used. As used herein, amorphous carbon refers to a carbon material that is amorphous as a whole and has a structure in which microcrystals are randomly networked. Further, the amorphous carbon may have a structure partially similar to graphite. Examples of the amorphous carbon include carbon black, coke, activated carbon, carbon fiber, hard carbon, soft carbon, and mesoporous carbon. The amorphous carbon is preferably in the form of particles. When a mixed carbon material containing both graphite particles and amorphous carbon particles is used as the negative electrode active material, the battery regeneration performance is improved. As the carbon material, graphite particles coated with amorphous carbon can also be used.
　負極活物質層に場合により用いられる導電助剤として、カーボンナノファイバー等のカーボン繊維、アセチレンブラック、ケッチェンブラック等のカーボンブラック、活性炭、メゾポーラスカーボン、フラーレン類、カーボンナノチューブ等の炭素材料が挙げられる。その他、負極活物質層には増粘剤、分散剤、安定剤等の、電極形成のために一般的に用いられる電極添加剤を適宜使用することができる。 Examples of conductive auxiliary agents used in the negative electrode active material layer include carbon fibers such as carbon nanofibers, carbon blacks such as acetylene black and ketjen black, carbon materials such as activated carbon, mesoporous carbon, fullerenes, and carbon nanotubes. It is done. In addition, electrode additives generally used for electrode formation, such as a thickener, a dispersant, and a stabilizer, can be appropriately used for the negative electrode active material layer.
　負極活物質層に用いられるバインダーとして、ポリフッ化ビニリデン（ＰＶＤＦ）、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニル（ＰＶＦ）等のフッ素樹脂、ポリアニリン類、ポリチオフェン類、ポリアセチレン類、ポリピロール類等の導電性ポリマー、スチレンブタジエンラバー（ＳＢＲ）、ブタジエンラバー（ＢＲ）、クロロプレンラバー（ＣＲ）、イソプレンラバー（ＩＲ）、アクリロニトリルブタジエンラバー（ＮＢＲ）等の合成ゴム、あるいはカルボキシメチルセルロース（ＣＭＣ）、キサンタンガム、グアーガム、ペクチン等の多糖類を用いることができる。 As a binder used for the negative electrode active material layer, fluororesins such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and polyvinyl fluoride (PVF), and conductive materials such as polyanilines, polythiophenes, polyacetylenes, and polypyrroles. Polymer, synthetic rubber such as styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), or carboxymethyl cellulose (CMC), xanthan gum, guar gum, Polysaccharides such as pectin can be used.
　すべての実施形態において用いることができる正極ならびに負極は、先に説明した正極活物質あるいは負極活物質を含む電極活物質層が電極集電体に配置されたものである。好ましくは、このとき電極活物質層の厚さは片面あたり２５～１００μｍであることが好ましい。電極活物質層の厚さが小さすぎると均一な電極活物質層の形成が難しいという不都合があり、一方電極活物質層の厚さが大きすぎると高レートでの充放電性能が低下するという不都合があり得る。 The positive electrode and negative electrode that can be used in all the embodiments are those in which the electrode active material layer containing the positive electrode active material or the negative electrode active material described above is disposed on the electrode current collector. In this case, the thickness of the electrode active material layer is preferably 25 to 100 μm per side. If the thickness of the electrode active material layer is too small, there is an inconvenience that it is difficult to form a uniform electrode active material layer. On the other hand, if the thickness of the electrode active material layer is too large, the charge / discharge performance at a high rate decreases. There can be.
　すべての実施形態において用いられるセパレータは、オレフィン系樹脂層から構成される。オレフィン系樹脂層は、エチレン、プロピレン、ブテン、ペンテン、へキセンなどのα－オレフィンを重合または共重合させたポリオレフィンから構成される層である。実施形態において、電池温度上昇時に閉塞される空孔を有する構造、すなわち多孔質あるいは微多孔質のポリオレフィンから構成される層であることが好ましい。オレフィン系樹脂層がこのような構造を有していることにより、万一電池温度が上昇しても、セパレータが閉塞して（シャットダウンして）、イオン流を寸断することができる。シャットダウン効果を発揮するためには、多孔質のポリエチレン膜を用いることが非常に好ましい。セパレータは、場合により耐熱性微粒子層を有していてよい。この際、電池の過熱を防止するために設けられた耐熱性微粒子層は、耐熱温度が１５０℃以上の耐熱性を有し、電気化学反応に安定な無機微粒子から構成される。このような無機微粒子として、シリカ、アルミナ（α－アルミナ、β－アルミナ、θ－アルミナ）、酸化鉄、酸化チタン、チタン酸バリウム、酸化ジルコニウムなどの無機酸化物；ベーマイト、ゼオライト、アパタイト、カオリン、スピネル、マイカ、ムライトなどの鉱物を挙げることができる。このように、耐熱層を有するセラミックセパレータを用いることもできる。 The separator used in all the embodiments is composed of an olefin resin layer. The olefin resin layer is a layer composed of polyolefin obtained by polymerizing or copolymerizing α-olefin such as ethylene, propylene, butene, pentene, hexene and the like. In the embodiment, a structure having pores that are closed when the battery temperature rises, that is, a layer composed of a porous or microporous polyolefin is preferable. Since the olefin resin layer has such a structure, even if the battery temperature rises, the separator is closed (shuts down), and the ion flow can be cut off. In order to exert a shutdown effect, it is very preferable to use a porous polyethylene film. The separator may optionally have a heat-resistant fine particle layer. At this time, the heat-resistant fine particle layer provided to prevent overheating of the battery is composed of inorganic fine particles having a heat resistance of 150 ° C. or higher and stable to an electrochemical reaction. As such inorganic fine particles, inorganic oxides such as silica, alumina (α-alumina, β-alumina, θ-alumina), iron oxide, titanium oxide, barium titanate, zirconium oxide; boehmite, zeolite, apatite, kaolin, Mention may be made of minerals such as spinel, mica and mullite. Thus, a ceramic separator having a heat-resistant layer can also be used.
　本明細書のすべての実施形態において用いる電解液は、非水電解液であって、ジメチルカーボネート（ＤＭＣ）、ジエチルカーボネート（ＤＥＣ）、エチルメチルカーボネート（ＥＭＣ）、ジ－ｎ－プロピルカーボネート、ジ－ｔ－プロピルカーボネート、ジ－ｎ－ブチルカーボネート、ジ－イソブチルカーボネート、またはジ－ｔ－ブチルカーボネート等の鎖状カーボネートと、プロピレンカーボネート（ＰＣ）、エチレンカーボネート（ＥＣ）等の環状カーボネートとを含む混合物であることが好ましい。電解液は、このようなカーボネート混合物に、六フッ化リン酸リチウム（ＬｉＰＦ６）、ホウフッ化リチウム（ＬｉＢＦ４）、過塩素酸リチウム（ＬｉＣｌＯ４）等のリチウム塩を溶解させたものである。 The electrolyte used in all the embodiments of the present specification is a non-aqueous electrolyte and is dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), di-n-propyl carbonate, di- A mixture containing a chain carbonate such as t-propyl carbonate, di-n-butyl carbonate, di-isobutyl carbonate, or di-t-butyl carbonate and a cyclic carbonate such as propylene carbonate (PC) or ethylene carbonate (EC). It is preferable that The electrolytic solution is obtained by dissolving a lithium salt such as lithium hexafluorophosphate (LiPF 6 ), lithium borofluoride (LiBF 4 ), or lithium perchlorate (LiClO 4 ) in such a carbonate mixture.
　電解液は、このほか、添加剤として環状カーボネート化合物を含んでいてもよい。添加剤として用いられる環状カーボネートとしてビニレンカーボネート（ＶＣ）が挙げられる。ビニレンカーボネートは、電池の充放電過程において正極ならびに負極上に保護被膜を形成することができる化合物である。また、添加剤としてハロゲンを有する環状カーボネート化合物を用いてもよい。これらの環状カーボネートも、電池の充放電過程において正極ならびに負極上に保護被膜を形成する化合物である。ハロゲンを有する環状カーボネート化合物として、フルオロエチレンカーボネート（ＦＥＣ）、ジフルオロエチレンカーボネート、トリフルオロエチレンカーボネート、クロロエチレンカーボネート、ジクロロエチレンカーボネート、トリクロロエチレンカーボネート等を挙げることができる。ハロゲンを有し不飽和結合を有する環状カーボネート化合物であるフルオロエチレンカーボネートは特に好ましく用いられる。ビニレンカーボネートやフルオロエチレンカーボネートは、特に、下記のジスルホン酸化合物またはジスルホン酸エステル化合物のような硫黄を含む化合物による、リチウム・ニッケル系複合酸化物を含有する正極活物質への攻撃を防ぐことができる化合物として知られている。 In addition to this, the electrolytic solution may contain a cyclic carbonate compound as an additive. Vinylene carbonate (VC) is mentioned as a cyclic carbonate used as an additive. Vinylene carbonate is a compound that can form a protective film on the positive electrode and the negative electrode in the process of charging and discharging the battery. Moreover, you may use the cyclic carbonate compound which has a halogen as an additive. These cyclic carbonates are also compounds that form a protective film on the positive electrode and the negative electrode in the charge and discharge process of the battery. Examples of the halogen-containing cyclic carbonate compound include fluoroethylene carbonate (FEC), difluoroethylene carbonate, trifluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, and trichloroethylene carbonate. Fluoroethylene carbonate, which is a cyclic carbonate compound having a halogen and an unsaturated bond, is particularly preferably used. In particular, vinylene carbonate and fluoroethylene carbonate can prevent attacks on positive electrode active materials containing lithium / nickel composite oxides by sulfur-containing compounds such as the following disulfonic acid compounds or disulfonic acid ester compounds. Known as a compound.
　電解液は、添加剤としてジスルホン酸化合物をさらに含んでいてもよい。ジスルホン酸化合物とは、一分子内にスルホ基を２つ有する化合物であり、スルホ基が金属イオンと共に塩を形成したジスルホン酸塩化合物、あるいはスルホ基がエステルを形成したジスルホン酸エステル化合物を包含する。ジスルホン酸化合物のスルホ基の１つまたは２つは、金属イオンと共に塩を形成していてもよく、アニオンの状態であってもよい。ジスルホン酸化合物の例として、メタンジスルホン酸、１，２－エタンジスルホン酸、１，３－プロパンジスルホン酸、１，４－ブタンジスルホン酸、ベンゼンジスルホン酸、ナフタレンジスルホン酸、ビフェニルジスルホン酸、およびこれらの塩（メタンジスルホン酸リチウム、１，３－エタンジスルホン酸リチウム等）、およびこれらのアニオン（メタンジスルホン酸アニオン、１，３－エタンジスルホン酸アニオン等）が挙げられる。またジスルホン酸化合物としてはジスルホン酸エステル化合物が挙げられ、メタンジスルホン酸、１，２－エタンジスルホン酸、１，３－プロパンジスルホン酸、１，４－ブタンジスルホン酸、ベンゼンジスルホン酸、ナフタレンジスルホン酸、またはビフェニルジスルホン酸のアルキルジエステルまたはアリールジエステル等の鎖状ジスルホン酸エステル；ならびにメチレンメタンジスルホン酸エステル、エチレンメタンジスルホン酸エステル、プロピレンメタンジスルホン酸エステル等の環状ジスルホン酸エステルが好ましく用いられる。メチレンメタンジスルホン酸エステル（ＭＭＤＳ）は特に好ましく用いられる。 The electrolytic solution may further contain a disulfonic acid compound as an additive. The disulfonic acid compound is a compound having two sulfo groups in one molecule, and includes a disulfonate compound in which the sulfo group forms a salt with a metal ion, or a disulfonate compound in which the sulfo group forms an ester. . One or two of the sulfo groups of the disulfonic acid compound may form a salt with the metal ion or may be in an anionic state. Examples of disulfonic acid compounds include methanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,3-propanedisulfonic acid, 1,4-butanedisulfonic acid, benzenedisulfonic acid, naphthalenedisulfonic acid, biphenyldisulfonic acid, and these And salts (lithium methanedisulfonate, lithium 1,3-ethanedisulfonate, etc.) and anions thereof (methanedisulfonate anion, 1,3-ethanedisulfonate anion, etc.). Disulfonic acid compounds include disulfonic acid ester compounds, such as methanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,3-propanedisulfonic acid, 1,4-butanedisulfonic acid, benzenedisulfonic acid, naphthalenedisulfonic acid, Alternatively, chain disulfonic acid esters such as alkyl diesters or aryl diesters of biphenyl disulfonic acid; and cyclic disulfonic acid esters such as methylenemethane disulfonic acid ester, ethylenemethane disulfonic acid ester, and propylene methane disulfonic acid ester are preferably used. Methylenemethane disulfonate (MMDS) is particularly preferably used.
　上記の正極ならびに負極をセパレータを介して積層し、これを上記の電解液と共に外装体内部に封入してラミネート型リチウムイオン二次電池を形成することができる。外装体として、電解液を外部に浸出させない材料であればいかなるものを使用してもよいが、アルミニウム箔と、ポリエチレンやポリプロピレン等のポリマーとの積層体であるアルミニウムラミネートを使用することができる。 The above positive electrode and negative electrode can be laminated via a separator, and this can be enclosed together with the above electrolytic solution in the exterior body to form a laminated lithium ion secondary battery. Any material can be used as the exterior body as long as it does not allow the electrolytic solution to be leached to the outside, but an aluminum laminate that is a laminate of an aluminum foil and a polymer such as polyethylene or polypropylene can be used.
　ここで、すべての実施態様において、電解液の量は、正極活物質層、負極活物質層およびセパレータから構成される積層物に存在する空孔の体積の合計に対して１．１～１．４倍であることが好ましい。電解液の量が少なすぎると、電池のサイクル特性が低下するおそれがあり、電解液の量が多すぎると、ラミネート型電池の膨れが起こり、電池を加圧した状態で電圧測定を行うスクリーニングが適切に行われなくなる可能性がある。 Here, in all the embodiments, the amount of the electrolytic solution is 1.1 to 1. with respect to the total volume of pores existing in the laminate composed of the positive electrode active material layer, the negative electrode active material layer, and the separator. It is preferably 4 times. If the amount of the electrolytic solution is too small, the cycle characteristics of the battery may be deteriorated. If the amount of the electrolytic solution is too large, the laminate-type battery may swell, and screening for measuring the voltage in a state where the battery is pressurized may be performed. May not be done properly.
　ここで、実施形態にかかるリチウムイオン二次電池の構成例を、図面を用いて説明する。図１はリチウムイオン二次電池の断面図の一例を表す。リチウムイオン二次電池１０は、主な構成要素として、負極集電体１１、負極活物質層１３、セパレータ１７、正極集電体１２、正極活物質層１５を含む。図１では、負極集電体１１の両面に負極活物質層１３が設けられ、正極集電体１２の両面に正極活物質層１５が設けられているが、各々の集電体の片面上のみに活物質層を形成することもできる。負極集電体１１、正極集電体１２、負極活物質層１３、正極活物質層１５、及びセパレータ１７が一つの電池の構成単位、すなわち発電要素である（図中、単電池１９）。このような単電池１９を、セパレータ１７を介して複数積層する。各負極集電体１１から延びる延出部を負極リード２５上に一括して接合し、各正極集電体１２から延びる延出部を正極リード２７上に一括して接合してある。なお正極リードとしてアルミニウム板、負極リードとして銅板が好ましく用いられ、場合により他の金属（たとえばニッケル、スズ、はんだ）または高分子材料による部分コーティングを有していてもよい。正極リードおよび負極リードはそれぞれ正極および負極に溶接される。このように複数の単電池を積層してできた電池は、溶接された負極リード２５および正極リード２７を外側に引き出す形で、外装体２９により包装される。外装体２９の内部には電解液３１が注入されている。外装体２９は、周縁部が熱融着した形状をしている。 Here, a configuration example of the lithium ion secondary battery according to the embodiment will be described with reference to the drawings. FIG. 1 shows an example of a cross-sectional view of a lithium ion secondary battery. The lithium ion secondary battery 10 includes a negative electrode current collector 11, a negative electrode active material layer 13, a separator 17, a positive electrode current collector 12, and a positive electrode active material layer 15 as main components. In FIG. 1, the negative electrode active material layer 13 is provided on both surfaces of the negative electrode current collector 11 and the positive electrode active material layer 15 is provided on both surfaces of the positive electrode current collector 12, but only on one side of each current collector. An active material layer can also be formed. The negative electrode current collector 11, the positive electrode current collector 12, the negative electrode active material layer 13, the positive electrode active material layer 15, and the separator 17 are constituent units of one battery, that is, a power generation element (unit cell 19 in the figure). A plurality of such unit cells 19 are stacked via the separator 17. The extending portion extending from each negative electrode current collector 11 is collectively bonded onto the negative electrode lead 25, and the extending portion extending from each positive electrode current collector 12 is collectively bonded to the positive electrode lead 27. An aluminum plate is preferably used as the positive electrode lead, and a copper plate is preferably used as the negative electrode lead, and in some cases, it may have a partial coating with another metal (for example, nickel, tin, solder) or a polymer material. The positive electrode lead and the negative electrode lead are welded to the positive electrode and the negative electrode, respectively. A battery formed by laminating a plurality of single cells in this manner is packaged by an outer package 29 so that the welded negative electrode lead 25 and positive electrode lead 27 are drawn out to the outside. An electrolytic solution 31 is injected into the exterior body 29. The exterior body 29 has a shape in which the peripheral edge portion is heat-sealed.
　実施形態にかかるリチウムイオン二次電池において、正極および負極の面積は７５ｃｍ２以上であることが好ましい。ここで両電極の面積が７５ｃｍ２以上であることは、本実施形態のリチウムイオン二次電池が比較的面積の広い電池であることを意味する。ラミネート型電池の電極面積が大きいと、上記のスクリーニングはより困難になりうる。ここで正極の種類と、電解液の体積とのバランスを考慮することで、電池のサイクル特性を低下させることなく、適切なスクリーニングを遂行できるようになった。 In the lithium ion secondary battery according to the embodiment, the areas of the positive electrode and the negative electrode are preferably 75 cm 2 or more. Here, the area of both electrodes being 75 cm 2 or more means that the lithium ion secondary battery of the present embodiment is a battery having a relatively large area. When the electrode area of the laminated battery is large, the above screening can be more difficult. Here, by considering the balance between the type of the positive electrode and the volume of the electrolytic solution, appropriate screening can be performed without deteriorating the cycle characteristics of the battery.
＜正極の作製＞
　リチウム・ニッケル系複合酸化物（ニッケル・コバルト・マンガン酸リチウム（「ＮＣＭ４３３」、すなわちニッケル：コバルト：マンガン＝４：３：３））と、スピネル構造を有するリチウム・マンガン系複合酸化物（Ｌｉ１．１Ｍｎ１．９Ｏ４の粉末）とを、表１に記載の割合で混合したものと、導電助剤としてカーボンブラック粉末（ＣＢ）と、バインダー樹脂としてＰＶＤＦ（クレハ製、＃７２００）とを、固形分質量比で複合酸化物：ＣＢ：ＰＶＤＦが９３：４：３の割合となるように混合し、溶媒であるＮＭＰに添加した。さらに、この混合物に有機系水分捕捉剤として無水シュウ酸（分子量９０）を、上記混合物からＮＭＰを除いた固形分１００質量部に対して０．０３質量部添加した上で遊星方式の分散混合を３０分間実施することで、これらの材料を均一に分散させてスラリーを作製した。得られたスラリーを、正極集電体となる厚み２０μｍのアルミニウム箔上に乾燥後重量が片面あたり２０ｍｇ／ｃｍ２となるように塗布した。次いで、１２５℃にて１０分間、電極を加熱し、ＮＭＰを蒸発させることにより正極活物質層を形成した。さらに、正極活物質層の空孔率が２５％となるように電極をプレスして、正極集電体の片面上に厚さ６３μｍの正極活物質層を塗布した正極を作製した。 <Preparation of positive electrode>
Lithium / nickel composite oxide (nickel / cobalt / lithium manganate (“NCM433”, ie, nickel: cobalt: manganese = 4: 3: 3)) and lithium / manganese composite oxide having a spinel structure (Li 1 .1 Mn 1.9 O 4 powder) at a ratio shown in Table 1, carbon black powder (CB) as a conductive additive, PVDF (made by Kureha, # 7200) as a binder resin, Were mixed so that the composite oxide: CB: PVDF was in a ratio of 93: 4: 3 in terms of solid content mass ratio, and added to NMP as a solvent. Further, oxalic anhydride (molecular weight 90) as an organic moisture scavenger was added to this mixture in an amount of 0.03 parts by mass with respect to 100 parts by mass of the solid content obtained by removing NMP from the above mixture, followed by planetary dispersion mixing. By carrying out for 30 minutes, these materials were disperse | distributed uniformly and the slurry was produced. The obtained slurry was applied on a 20 μm thick aluminum foil serving as a positive electrode current collector so that the weight after drying was 20 mg / cm 2 per side. Next, the electrode was heated at 125 ° C. for 10 minutes to evaporate NMP, thereby forming a positive electrode active material layer. Furthermore, the electrode was pressed so that the porosity of the positive electrode active material layer was 25%, and a positive electrode in which a positive electrode active material layer having a thickness of 63 μm was applied on one surface of the positive electrode current collector was produced.
＜負極の作製＞
　負極活物質として、非晶質炭素で被覆された粒子状黒鉛粉末（平均粒子径２０μｍ）を用いた。この黒鉛粉末と、導電助剤としてＣＢとを、バインダー樹脂であるスチレンブタジエンラバーとカルボキシメチルセルロースとの水溶液に、固形分質量比が黒鉛粉末：導電助剤：バインダー＝９６．７：０．３：３の割合となるように均一に混合してスラリーを作製した。得られたスラリーを、負極集電体となる厚み１０μｍの銅箔上に乾燥後重量が片面あたり１６ｍｇ／ｃｍ２となるように塗布した。次いで、１２５℃にて１０分間、電極を加熱し、水を蒸発させることにより負極活物質層を形成した。さらに、負極活物質層の空孔率が３３％となるように電極をプレスして、負極集電体の片面上に厚さ６２μｍの負極活物質層を塗布した負極を作製した。 <Production of negative electrode>
As the negative electrode active material, particulate graphite powder (average particle size 20 μm) coated with amorphous carbon was used. This graphite powder and CB as a conductive auxiliary agent are added to an aqueous solution of styrene butadiene rubber and carboxymethyl cellulose as a binder resin, and the solid content mass ratio is graphite powder: conductive auxiliary agent: binder = 96.7: 0.3: A slurry was prepared by uniformly mixing to a ratio of 3. The obtained slurry was applied onto a 10 μm thick copper foil serving as a negative electrode current collector so that the weight after drying was 16 mg / cm 2 per side. Next, the electrode was heated at 125 ° C. for 10 minutes to evaporate water, thereby forming a negative electrode active material layer. Further, the electrode was pressed so that the porosity of the negative electrode active material layer was 33%, and a negative electrode in which a negative electrode active material layer having a thickness of 62 μm was applied on one surface of the negative electrode current collector was produced.
＜セパレータ＞
　耐熱微粒子としてベーマイトを用いた耐熱微粒子層とポリプロピレンおよびポリエチレンからなる厚さ１８μｍのオレフィン系樹脂層都から構成される、全体の厚さが２５μｍ、空孔率が５５％のセラミックセパレータを使用した。 <Separator>
A ceramic separator composed of a heat-resistant fine particle layer using boehmite as heat-resistant fine particles and an olefin-based resin layer made of polypropylene and polyethylene having a thickness of 25 μm and a porosity of 55% was used.
＜電解液＞
　エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、およびエチルメチルカーボネート（ＥＭＣ）とを、ＥＣ：ＤＥＣ：ＥＭＣ＝３０：６０：１０の体積比で混合した非水溶媒を用意した。この混合非水溶媒に電解質塩としての六フッ化リン酸リチウム（ＬｉＰＦ６）を濃度が０．９ｍｏｌ／Ｌとなるように溶解させ、次いで、添加剤としてＭＭＤＳ、ＶＣおよびＦＥＣ（ＭＭＤＳ：ＶＣ：ＦＥＣ＝:１：１：１）を、これらの合計濃度が３重量％となるように溶解させた。 <Electrolyte>
A non-aqueous solvent prepared by mixing ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) at a volume ratio of EC: DEC: EMC = 30: 60: 10 was prepared. In this mixed non-aqueous solvent, lithium hexafluorophosphate (LiPF 6 ) as an electrolyte salt is dissolved so as to have a concentration of 0.9 mol / L, and then MMDS, VC and FEC (MMDS: VC: FEC =: 1: 1: 1) was dissolved so that their total concentration was 3% by weight.
＜リチウムイオン二次電池の作製＞
　上記のように作製した正極ならびに負極を、各活物質が塗布されていない集電体延長部が残るようにサイズ２２０ｍｍ×１９０ｍｍの矩形に切り出して正極版と負極板とを用意した。セパレータの両面に上記負極板と正極板とを両活物質層がセパレータを隔てて重なるように配置したものを２０層重ね電極積層体を得た。そして、負極板の負極集電体延長部に対し負極端子の内側端（一端部）を接合した。同様に正極板の正極集電体延長部にたいし正極端子の内側端（一端部）を接合した。この電極板積層体を外装体となる２枚のアルミニウムラミネートフィルムで包み、比較的小さな充填孔のみを残して周囲の四辺を熱融着により接着した。次いで、後に行うスクリーニング検出性試験時に電解液量が表１に示すような体積割合となるように、充填高から電解液を注入した。なお四辺のうち一辺は正極端子および負極端子を引き出した状態でアルミニウムラミネートフィルムの熱融着を行った。この熱融着部と電極板積層体との距離は、端子引き出し辺においては１５ｍｍ、それ以外の辺においては５ｍｍとした。電解液を注入した後に外装体内部を真空含浸させ、減圧して充填孔を熱融着により封止して、積層型リチウムイオン電池を作成した。この積層型リチウムイオン電池の初充電を行った後、４５℃でエージングを数日間行い、各実施例ならびに比較例の積層型リチウムイオン電池を得た。 <Production of lithium ion secondary battery>
The positive electrode and the negative electrode produced as described above were cut into a rectangular shape having a size of 220 mm × 190 mm so as to leave a current collector extension portion to which each active material was not applied to prepare a positive electrode plate and a negative electrode plate. A 20-layer electrode stack was obtained by arranging the negative electrode plate and the positive electrode plate on both sides of the separator so that both active material layers overlapped with the separator therebetween. And the inner side end (one end part) of the negative electrode terminal was joined with the negative electrode collector extension part of the negative electrode plate. Similarly, the inner end (one end) of the positive electrode terminal was joined to the positive electrode current collector extension of the positive electrode plate. This electrode plate laminate was wrapped with two aluminum laminate films serving as an outer package, and the surrounding four sides were bonded together by thermal fusion, leaving only relatively small filling holes. Subsequently, the electrolyte solution was injected from the filling height so that the volume of the electrolyte solution was as shown in Table 1 during the screening detectability test to be performed later. One side of the four sides was heat-sealed with the aluminum laminate film with the positive electrode terminal and the negative electrode terminal pulled out. The distance between the heat-sealed portion and the electrode plate laminate was 15 mm at the terminal lead-out side and 5 mm at the other sides. After injecting the electrolytic solution, the inside of the outer package was vacuum-impregnated, the pressure was reduced, and the filling hole was sealed by thermal fusion to produce a stacked lithium ion battery. After the initial charge of this multilayer lithium ion battery, aging was performed at 45 ° C. for several days to obtain multilayer lithium ion batteries of Examples and Comparative Examples.
＜正極、負極、セパレータの空孔率＞
　電極の空孔率は、材料の真密度と部材厚み、塗布量、混合比より算出した。セパレータの空孔率は、材料の真密度と部材厚みより算出した。 <Porosity of positive electrode, negative electrode, separator>
The porosity of the electrode was calculated from the true density of the material, the member thickness, the coating amount, and the mixing ratio. The porosity of the separator was calculated from the true density of the material and the member thickness.
＜サイクル特性試験＞
　上記の通り作製した電池を、温度４５℃環境下で、充電：１Ｃ電流、上限電圧４．１５Ｖでの定電流定電圧充電、放電：１Ｃ電流、下限電圧２．５Ｖ終止で定電流放電の充放電サイクルを１０００回繰り返した。１０００サイクル後の放電容量維持率（％）を測定した。 <Cycle characteristic test>
The battery manufactured as described above is charged under a temperature of 45 ° C., charging: 1 C current, constant current constant voltage charging at an upper limit voltage of 4.15 V, discharging: constant current discharging at the end of 1 C current, lower limit voltage of 2.5 V The discharge cycle was repeated 1000 times. The discharge capacity retention rate (%) after 1000 cycles was measured.
＜スクリーニング検出性試験＞
　電池の作製時に、正極に銅箔切断屑（サイズ１０μｍ×１０μｍ×１ｍｍ）を固定した正極を用いた電池を別途作製した。スクリーニング検出性試験用電池の残容量（ＳＯＣ）を５％となるまで充電し、２つのスペーサ板の間に挟んだ。この状態で２つのスペーサに荷重を加え、電池の外装体が弾性変形を生じるまで押圧し、この状態で電池の電圧を測定した。２５℃で４日間加圧状態を保った後、再び電池の電圧を測定し、加圧時の電圧低下量を算出した。一方銅箔切断屑を固定しない電池についても同様の試験を行って電圧低下量を算出し、銅箔切断屑を固定した電池の電圧低下量が有意に大きい場合、この電池を「検出可」と評価した。一方、銅箔切断屑を固定しない電池と、これを固定しない電池とで電圧低下量に有意な差が見られない場合、この電池を「検出不可」と評価した。 <Screening detectability test>
When the battery was manufactured, a battery using a positive electrode in which copper foil cutting waste (size 10 μm × 10 μm × 1 mm) was fixed to the positive electrode was separately manufactured. The remaining capacity (SOC) of the screening detectability test battery was charged to 5% and sandwiched between two spacer plates. In this state, a load was applied to the two spacers, and the battery outer body was pressed until elastic deformation occurred, and the battery voltage was measured in this state. After maintaining the pressurized state at 25 ° C. for 4 days, the voltage of the battery was measured again, and the amount of voltage decrease during pressurization was calculated. On the other hand, the same test is performed for a battery that does not fix copper foil cutting waste, and the amount of voltage drop is calculated.If the voltage drop amount of the battery with copper foil cutting waste fixed is significantly large, this battery is marked as “detectable”. evaluated. On the other hand, when there was no significant difference in voltage drop between the battery that did not fix the copper foil cutting waste and the battery that did not fix the copper foil, this battery was evaluated as “undetectable”.
　実施例１～６および比較例１～３の積層型リチウムイオン二次電池について、上記の評価を行った結果を表１に示す。なお、表１中のサイクル特性の数値は、比較例１の電池のサイクル後放電容量維持率（％）の値を１００とし、これに対する相対値である。 Table 1 shows the results of the above evaluations on the stacked lithium ion secondary batteries of Examples 1 to 6 and Comparative Examples 1 to 3. In addition, the numerical value of the cycle characteristics in Table 1 is a relative value with respect to the value of the post-cycle discharge capacity retention rate (%) of the battery of Comparative Example 1 being 100.
Figure JPOXMLDOC01-appb-T000001
  
Figure JPOXMLDOC01-appb-T000001
  
　リチウム・マンガン系複合酸化物の割合が本発明の範囲を満たす正極活物質を用い、電解液の存在量を所定の範囲に維持した実施例に係る電池は、いずれも加圧によるスクリーニングによって異物の混入を検出することができた。実施例に係る電池はサイクル特性も良好であった。一方、電解液の存在量が少ない比較例１の電池は、スクリーニングによる検出は可能であったが、サイクル特性に劣り、電解液の存在量が多い比較例２の電池は、スクリーニングによる検出ができなかった。さらにリチウム・マンガン系複合酸化物の割合が多い正極活物質を用いた比較例３に係る電池は、スクリーニングによる検出ができなかった。 The batteries according to the examples using the positive electrode active material in which the ratio of the lithium-manganese composite oxide satisfies the scope of the present invention and maintaining the abundance of the electrolyte in a predetermined range are all subjected to foreign matter screening by pressurization. Contamination could be detected. The battery according to the example also had good cycle characteristics. On the other hand, the battery of Comparative Example 1 with a small amount of electrolyte solution was detectable by screening, but the battery of Comparative Example 2 with a poor amount of cycle characteristics and a large amount of electrolyte solution could be detected by screening. There wasn't. Furthermore, the battery according to Comparative Example 3 using the positive electrode active material having a large proportion of the lithium / manganese composite oxide could not be detected by screening.
　以上、本発明の実施例について説明したが、上記実施例は本発明の実施形態の一例を示したに過ぎず、本発明の技術的範囲を特定の実施形態あるいは具体的構成に限定する趣旨ではない。 As mentioned above, although the Example of this invention was described, the said Example was only an example of Embodiment of this invention, and in the meaning which limits the technical scope of this invention to specific embodiment or a specific structure. Absent.

Claims (6)

  1. 　正極活物質層が正極集電体に配置された正極と、
    　負極活物質層が負極集電体に配置された負極と、
    　セパレータと、
    　電解液と、
    を含む発電要素を、外装体内部に含むリチウムイオン二次電池であって、
    　　該正極活物質層が、リチウム・ニッケル系複合酸化物、または正極活物質の重量に対して７０重量％以下のリチウム・マンガン系複合酸化物を含むリチウム・ニッケル系複合酸化物から構成され、
    　　該発電要素中に含まれる該電解液の体積が、該正極活物質層、該負極活物質層および該セパレータに存在する空孔の体積の合計の値に対して１．１～１．４倍である、
    前記リチウムイオン二次電池。     A positive electrode having a positive electrode active material layer disposed on a positive electrode current collector;
    A negative electrode having a negative electrode active material layer disposed on a negative electrode current collector;
    A separator;
    An electrolyte,
    A lithium ion secondary battery including a power generation element including
    The positive electrode active material layer is composed of a lithium / nickel composite oxide, or a lithium / nickel composite oxide containing 70% by weight or less of a lithium / manganese composite oxide based on the weight of the positive electrode active material,
    The volume of the electrolyte contained in the power generation element is 1.1 to 1.4 times the total value of the volume of pores present in the positive electrode active material layer, the negative electrode active material layer, and the separator. Is,
    The lithium ion secondary battery.
  2. 　該正極および該負極の面積が７５ｃｍ２以上である、請求項１に記載のリチウムイオン二次電池。 The lithium ion secondary battery according to claim 1, wherein an area of the positive electrode and the negative electrode is 75 cm 2 or more.
  3. 　該リチウム・ニッケル系複合酸化物が、該正極活物質の重量に対して３０重量％以下のリチウム・マンガン系複合酸化物を含む、請求項１または２に記載のリチウムイオン二次電池。 The lithium ion secondary battery according to claim 1 or 2, wherein the lithium / nickel composite oxide includes 30% by weight or less of a lithium / manganese composite oxide based on the weight of the positive electrode active material.
  4. 　該電解液が、メチレンメタンジスルホン酸エステル、ビニレンカーボネート、フルオロエチレンカーボネートおよびこれらの混合物からなる群より選択される添加剤を含む、請求項１～３のいずれかに記載のリチウムイオン二次電池。 The lithium ion secondary battery according to any one of claims 1 to 3, wherein the electrolytic solution contains an additive selected from the group consisting of methylenemethane disulfonate, vinylene carbonate, fluoroethylene carbonate, and a mixture thereof.
  5. 　該リチウム・ニッケル系複合酸化物が、一般式ＬｉｘＮｉｙＣｏｚＭｎ（１－ｙ－ｚ）Ｏ２で表される層状結晶構造を有するリチウムニッケルコバルトマンガン複合酸化物である、請求項１～４のいずれかに記載のリチウムイオン二次電池。 2. The lithium / nickel composite oxide is a lithium nickel cobalt manganese composite oxide having a layered crystal structure represented by a general formula Li x Ni y Co z Mn (1-yz) O 2. The lithium ion secondary battery according to any one of 1 to 4.
  6. 　該リチウムイオン二次電池がラミネート型電池である、請求項１～５のいずれかに記載のリチウムイオン二次電池。 The lithium ion secondary battery according to any one of claims 1 to 5, wherein the lithium ion secondary battery is a laminate type battery.
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