WO2014156891A1 - Lithium ion secondary battery - Google Patents

Lithium ion secondary battery Download PDF

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Publication number
WO2014156891A1
WO2014156891A1 PCT/JP2014/057555 JP2014057555W WO2014156891A1 WO 2014156891 A1 WO2014156891 A1 WO 2014156891A1 JP 2014057555 W JP2014057555 W JP 2014057555W WO 2014156891 A1 WO2014156891 A1 WO 2014156891A1
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WO
WIPO (PCT)
Prior art keywords
metal
electrode plate
resin separator
lithium ion
ion secondary
Prior art date
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PCT/JP2014/057555
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French (fr)
Japanese (ja)
Inventor
和香奈 村田
奥村　壮文
学 落田
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新神戸電機株式会社
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Publication of WO2014156891A1 publication Critical patent/WO2014156891A1/en

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Classifications

    • 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
    • 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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • 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 lithium ion secondary battery including an electrode plate group in which a positive electrode plate and a negative electrode plate are laminated via a resin separator.
  • Lithium ion secondary batteries are mainly used as power sources for portable devices such as notebook computers and mobile phones, taking advantage of the high energy density.
  • the inside of a cylindrical lithium ion secondary battery has a strip shape in which both the positive electrode and the negative electrode are coated with an active material on a metal foil, and the cross section is such that these electrodes are not in direct contact with a resin separator in between. It has a wound structure in which a wound group is formed in which a spiral is wound. And this winding group is accommodated in the cylindrical battery can used as a battery container, and is sealed after electrolyte solution injection.
  • the external dimensions of a general cylindrical lithium ion secondary battery are widely used as a small-sized consumer lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm, which is called 18650 type.
  • this 18650 type lithium ion secondary battery lithium cobalt oxide characterized by high capacity and long life is mainly used as a positive electrode active material.
  • the battery capacity of the 18650 type lithium ion secondary battery is about 1.0 Ah to 2.5 Ah (3.7 Wh to 9.3 Wh).
  • lithium-ion secondary batteries are expected to be used not only for consumer applications but also for large-scale power storage systems for natural energy such as solar power and wind power generation.
  • the amount of electric power per system is required to be several MWh.
  • a large amount (about 1 million) of lithium ion secondary batteries are required.
  • a cell controller is attached to each battery, and the battery state is detected. For this reason, in a system that requires a large amount of batteries, a large amount of necessary cell controllers are also required, resulting in a significant increase in cost. Therefore, it is necessary to increase the capacity per battery to reduce the number of batteries and the number of cell controllers required for the system.
  • a high-capacity battery has a problem that, unlike a conventional 18650 battery, energy stored in the battery becomes high, so that it is difficult to ensure safety during unsteady times. Therefore, as shown in Patent Document 1, a method of manufacturing a separator for a lithium ion secondary battery in which an electron beam irradiation treatment is performed on the separator to prevent an internal short circuit due to the shrinkage of the separator during high temperature storage is known.
  • a metal or metal compound may be mixed as a foreign substance for some reason.
  • the inventors of the present invention have found that the possibility of occurrence of an internal short circuit of the battery is increased, starting from the metal or metal compound present in the battery as such a foreign substance.
  • a resin separator with a film thickness of 15 ⁇ m to 50 ⁇ m is used, there is a risk of internal short circuit when metal or metal compound particles having a particle size of 20 ⁇ m or more are present in the cell. Found out that it would be expensive.
  • the metal or metal compound particles mixed in the battery as a foreign substance grow as a dendrite in the battery in the process of repeated charge / discharge of the lithium ion secondary battery, thereby generating an internal short circuit.
  • the internal short circuit caused by the dendrite is generally generated by the following mechanisms (1) to (3).
  • (1) The metal or metal compound is oxidized and dissolved on the positive electrode side (M ⁇ M x + + xe ⁇ ), passes through the separator in the form of metal ions, is reduced on the negative electrode side, and is deposited on the surface of the negative electrode plate ( M x + + xe ⁇ ⁇ M).
  • the metal or metal compound reduced on the negative electrode side also precipitates in the voids of the separator.
  • the battery capacity is assumed to be about 10 Ah to 300 Ah, and the energy stored in the battery becomes high, so it is necessary to further ensure safety.
  • An object of the present invention is to provide a highly safe lithium ion secondary battery that prevents an internal short circuit even when a metal or a metal compound is mixed as a foreign substance in the battery.
  • a lithium ion secondary battery to be improved by the present invention includes an electrode plate group having a resin separator having a thickness of 15 to 50 ⁇ m, and a positive electrode plate and a negative electrode plate laminated with the resin separator interposed therebetween.
  • the “resin separator” includes both a resin separator constituted by a single resin separator sheet and a resin separator constituted by laminating a plurality of resin separator sheets.
  • the “metal or metal compound particles” do not constitute a positive electrode active material or a negative electrode active material.
  • the “metal or metal compound particles” are expected to be present in the battery as foreign matter generated by welding of electrodes and terminals in the battery manufacturing process. Examples of the “particles” include granular, flaky, spherical, columnar, and irregular shapes.
  • the granular shape is not an irregular shape but a shape having almost equal dimensions (JIS Z2500: 2000).
  • the flake shape is a plate-like shape (JIS Z2500: 2000) and is also called a scaly shape because it is thin like a scale.
  • the aspect ratio is 2 to 100 in the form of a piece.
  • the particle diameter a here is defined as the square root of the area S when the flaky particles are viewed in plan, and this is the particle diameter of the present application.
  • the “spherical shape” is a shape almost similar to a sphere (see JIS Z2500: 2000).
  • the spherical shape is not necessarily required, and the ratio of the major axis (DL) to the minor axis (DS) of the particle (DL) / (DS) (sometimes referred to as spherical coefficient or sphericity) is 1.0 to 1. .2 and the particle size in the present application refers to the major axis (DL).
  • the columnar shape includes a substantially cylindrical column, a substantially polygonal column, and the like, and the particle size in the present application refers to the height of the column.
  • the “particle size” can be measured under the conditions of a magnification of 100 to 1000 times with a microscope or 1000 to 10,000 times with a scanning electron microscope.
  • the reason why the particle size is limited to a metal or metal compound having a particle size of 20 ⁇ m or more is that if it is a metal or metal compound particle having a particle size of less than 20 ⁇ m, it is less likely to cause an internal short circuit even if it exists as a foreign substance in the battery. It is.
  • the maximum particle size of the metal or metal compound mixed in the battery manufacturing process is about 150 ⁇ m.
  • the volume of the metal or metal compound is in the range of about 4.19 ⁇ 10 3 to 1.77 ⁇ 10 6 ⁇ m 3 .
  • the metal which may be mixed in the battery in the manufacturing process is at least one metal selected from copper, iron, nickel, aluminum, manganese, and chromium.
  • the metal compound that may be mixed in the battery during the manufacturing process is an oxide of at least one metal among copper, iron, nickel, aluminum, manganese, and chromium.
  • V1 and V2 are represented by the following formula (1). It is adjusted to meet.
  • the volume V1 of the metal or metal compound particles is calculated from the mass and density of the metal or metal compound.
  • grains of a metal or a metal compound are spherical, you may calculate from ⁇ particle size (micrometer) x (1/2) ⁇ 3 * 4/3 (pi).
  • the “pore volume V2 per 1 ⁇ m 2 of the resin separator” is calculated by multiplying the volume calculated by multiplying the thickness of the resin separator and the unit area (1 ⁇ m 2 ) by the porosity of the resin separator.
  • V1 / V2 means that the volume V1 of the metal or metal compound particles is divided by the pore volume V2 of the resin separator.
  • V1 / V2 ⁇ 2250 means that the value of V1 / V2 is smaller than 2250.
  • the reduction-precipitated metal or metal compound dendrite is transferred from the surface of the negative electrode plate to the resin. It stays in the separator and can be prevented from reaching the positive electrode plate through the resin separator. As a result, a short circuit between the positive electrode and the negative electrode due to dendrites is prevented, and an internal short circuit of the battery can be prevented.
  • the relational expression between V1 and V2 is 2250 or more, precipitates such as dendrite easily reach the positive electrode from the resin separator, and a short circuit between the positive electrode and the negative electrode is likely to occur.
  • the relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 of the resin separator is preferably adjusted to satisfy the relationship of the following equation (2).
  • the relational expression “150 ⁇ V1 / V2 ⁇ 2250” means that the value of V1 / V2 is larger than 150 in addition to the value of V1 / V2 being smaller than 2250. Even if the value of V1 / V2 is smaller than 2250, if the value of V1 / V2 is 150 or less, the pore volume V2 of the resin separator is relative to the volume V1 of the metal or metal compound particles. Becomes significantly larger. When the pore volume of the resin separator becomes relatively large, precipitates such as dendrites tend to penetrate the resin separator, and a short circuit between the positive electrode and the negative electrode is likely to occur. Therefore, it is preferable to adjust the value of V1 / V2 to be larger than 150 as described above.
  • the relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 of the resin separator is more preferably adjusted to satisfy the relationship of the following formula (3).
  • V1 / V2 When the value of V1 / V2 is adjusted to be smaller than 2220 and larger than 165, when the particle size of the metal or metal compound exists between the resin separator and the positive electrode plate (the internal short circuit of the battery is Even in an environment in which it is likely to occur, deposits such as dendrites extending from the surface of the negative electrode plate tend to stay in the resin separator, and the short circuit between the positive electrode and the negative electrode can be reliably prevented.
  • a resin separator having a porosity adjusted to 30 to 50% is preferable to use as the resin separator.
  • the value of V1 / V2 is reduced to a value in which an internal short circuit is unlikely to occur even when metal or metal compound particles having a particle size of 20 ⁇ m or more are mixed in the battery. Easy to adjust.
  • a resin separator containing a polyolefin made of at least one of polypropylene and polyethylene is preferable to use as a material for the resin separator.
  • the present embodiment is directed to a stacked lithium ion secondary battery in which a positive electrode plate and a negative electrode plate are stacked via a resin separator
  • the present invention includes a positive electrode plate and a negative electrode plate stacked via a resin separator.
  • the present invention can also be applied to a wound lithium ion battery in which a laminated body is wound.
  • a positive electrode plate is produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a positive electrode current collector. Specifically, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these The material is dissolved and dispersed in a liquid medium, applied as a slurry to the positive electrode current collector, and dried to form a positive electrode active material layer on the positive electrode current collector.
  • a known lithium and transition metal composite oxide capable of inserting, desorbing and dissolving lithium can be used alone or in combination of two or more.
  • the composite oxide of lithium metal and transition metal include lithium manganate, lithium nickelate, lithium cobaltate, and lithium iron phosphate. These composite oxides may be of a single phase, a transition metal partially substituted with a different element, or a surface coated with an oxide or carbon.
  • the positive electrode conductive material a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
  • the binder used for manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that dissolves or disperses in the liquid medium used during electrode manufacturing may be used.
  • the binder include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene) Rubber) Rubber-like polymers such as rubber, fluoro rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber; ), Thermoplastic elastomeric polymers such as styrene / ethylene / butadiene / ethylene copolymers, styrene / isoprene / styrene block copolymers, or hydrogenated products thereof; syndiotactic-1, 2-polybuta
  • these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios.
  • a fluorine-based polymer such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene / vinylidene fluoride copolymer is preferable.
  • the positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material.
  • the material for the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbonaceous materials such as soot carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.
  • the form of the positive electrode current collector is not particularly limited, and a known form can be arbitrarily used.
  • the metal material include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal.
  • a carbonaceous material a carbon plate, a carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred.
  • the thickness of the thin film is arbitrary, but is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, and usually 1 mm or less, preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less. If the thin film is thinner than this range, the strength required for the current collector may be insufficient. Conversely, if the thin film is thicker than this range, the handleability may be impaired.
  • the negative electrode compound material containing the negative electrode active material which can electrochemically occlude / release lithium ion is apply
  • the negative electrode active material include carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, metals that can form alloys with lithium such as tin and silicon, etc. Is mentioned. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Among these, it is preferable from the viewpoint of safety to use a carbonaceous material or a lithium composite oxide.
  • the metal composite oxide is not particularly limited as long as it can occlude and release lithium, but it contains titanium and / or lithium as a constituent component in view of high current density charge / discharge characteristics. To preferred.
  • Carbonaceous materials include amorphous carbon, natural graphite, composite carbonaceous materials in which a film formed by dry CVD (Chemical Vapor Deposition) method or wet spray method is formed on natural graphite, resins such as epoxy and phenol Lithium that can occlude and release lithium by forming a carbonaceous material such as artificial graphite and amorphous carbon material that is made by firing from raw materials or pitch-based materials obtained from petroleum or coal, or by forming a compound with lithium
  • An oxide or nitride of a group 14 element such as silicon, germanium, tin, or the like, which forms a compound with metal, lithium, and is inserted into a crystal gap to absorb and release lithium, can be used.
  • the negative electrode mixture may contain two or more carbonaceous materials having different properties as a conductive material.
  • the negative electrode current collector a known one can be arbitrarily used.
  • the current collector for the negative electrode include copper, nickel, stainless steel, nickel-plated steel, and the like. Among these, copper is preferable from the viewpoint of ease of processing and cost.
  • the shape of the negative electrode current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punching metal, and foam metal when the current collector is a metal material. Among these, a metal thin film is preferable, and a copper foil is more preferable.
  • a rolled copper foil obtained by a rolling method and an electrolytic copper foil obtained by an electrolytic method can be used as the negative electrode current collector. When the thickness of the copper foil is less than 25 ⁇ m, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.
  • the binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used during electrode production.
  • resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile-butadiene rubber), rubber-like polymers such as ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene ⁇ Thermoplastic elastomeric polymers such as butadiene / styrene copolymer, styrene /
  • the resin separator has a predetermined mechanical strength that electrically insulates both electrodes, has a high ion permeability, and is resistant to oxidation on the side in contact with the positive electrode and reducibility on the negative electrode side.
  • a resin having both is used.
  • An olefin polymer is used as such a resin.
  • a porous sheet containing at least one of polypropylene and polyethylene as a material. .
  • the resin separator As the form of the resin separator, a microporous film having a thin film shape, a pore diameter of 0.01 to 1 ⁇ m, and a thickness of 15 to 50 ⁇ m is preferably used. Further, the porosity of the resin separator is preferably 30 to 50%, more preferably 35 to 45%. Note that the resin separator of this example (a resin separator having a thickness of 15 to 50 ⁇ m) may be constituted by a single separator or may be constituted by stacking two or more separators.
  • the metal or metal compound used in this example has a particle size of 20 ⁇ m or more.
  • the metal include copper, iron, nickel, manganese, and chromium.
  • the metal compound include oxides such as copper, iron, nickel, manganese and chromium, and compounds containing two or more of these.
  • the shape of the metal or metal compound include granular shapes, flake shapes, spherical shapes, needle shapes, irregular shapes, and the like.
  • the aspect ratio (particle diameter a / average thickness t) of the particle when analyzed from the result of SEM observation is in the range of 2 to 100, and the particle diameter a at this time (the particle is viewed in plan view)
  • the square root of the area S) was defined as the particle size.
  • the ratio (DL) / (DS) of the major axis (DL) and minor axis (DS) of the particle (sometimes referred to as a spherical coefficient or sphericity) is 1.0 to 1.2.
  • the major axis (DL) at this time was defined as the particle size.
  • the height of the column is defined as the particle size.
  • metals or metal compounds are mainly mixed from manufacturing equipment and manufacturing processes. It is preferable that a metal or a metal compound having a particle size of 20 ⁇ m or more is not included in the battery, but it is difficult to prevent a metal or a metal compound having a particle size of 20 ⁇ m or more from being included in the battery in the manufacturing process. It is.
  • the lower limit of the particle size of the metal or metal compound is 20 ⁇ m, and if it is smaller than this particle size, the problem of short circuit does not occur.
  • the upper limit is not particularly limited, but the metal or metal compound that may be mixed in the manufacturing process is assumed to be 150 ⁇ m or less.
  • V1 is calculated from the mass and density of the metal or metal compound particles, or ⁇ the particle size of the metal or metal compound ⁇ (1/2) ⁇ 3 when the metal or metal compound particles are spherical. It can be calculated from x4 / 3 ⁇ .
  • V2 is obtained by multiplying the volume calculated by multiplying the thickness and unit area (1 ⁇ m 2 ) of the resin separator by the porosity of the resin separator.
  • V1 and V2 satisfy the relationship of V1 / V2 ⁇ 2220. Further, from the practical viewpoint, the relationship 150 ⁇ V1 / V2 ⁇ 2250 may be satisfied, and more preferably the relationship 165 ⁇ V1 / V2 ⁇ 2220 is satisfied.
  • the resin separator has pores inside to hold and replace the electrolyte.
  • a metal or metal compound having a particle diameter of 20 ⁇ m or more is easily oxidized and dissolved during the operation of the lithium ion secondary battery, particularly when it is present between the resin separator and the positive electrode plate. It diffuses and migrates in the voids of the separator and is reduced and deposited on the negative electrode surface. When the reduction deposition continues, the metal or metal compound is deposited not only on the negative electrode surface but also in the separator gap. When this deposit reaches the positive electrode, it is considered that the positive electrode and the negative electrode are slightly short-circuited and an internal short circuit occurs in the battery. Note that a resin separator having a thinnest film thickness of 15 ⁇ m or more, which is generally applied, does not short-circuit when a metal or a metal compound having a particle size of less than 20 ⁇ m is included.
  • Electrolytic Solution used in the lithium ion secondary battery of this example is composed of a lithium salt and a non-aqueous solvent that dissolves the lithium salt, and may further contain an additive.
  • a known lithium salt is used as an electrolyte of a non-aqueous electrolyte for a lithium ion secondary battery, and examples thereof include the following.
  • Inorganic lithium salts inorganic fluoride salts such as LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 ; perhalogenates such as LiClO 4 , LiBrO 4 , LiIO 4 ; inorganic chloride salts such as LiAlCl 4 .
  • Fluorine-containing organic lithium salt perfluoroalkane sulfonate such as F 3 SO 3 ; LiN (CF 3 SO 2 ) 2 , LiN (CF 3 CF 2 SO 2 ) 2 , LiN (CF 3 SO 2 ) (C 4 Perfluoroalkanesulfonylimide salts such as F 9 SO 2 ); perfluoroalkanesulfonylmethide salts such as LiC (CF 3 SO 2 ) 3 ; Li [PF 5 (CF 2 CF 2 CF 3 )], Li [PF 4 (CF 2 CF 2 CF 3 ) 2 ], Li [PF 3 (CF 2 CF 2 CF 3 ) 3 ], Li [PF 5 (CF 2 CF 2 CF 2 CF 3 )], Li [PF 4 (CF 2 CF 2 CF 3 ) 2 ], Li [PF 3 (CF 2 CF 2 CF 3 ) 3 ], Li [PF 3 (CF 2 CF 2 CF 3 )], Li [PF 4 (CF 2
  • Oxalatoborate salts lithium bis (oxalato) borate, lithium difluorooxalatoborate, etc. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. Among these, lithium hexafluorophosphate (LiPF 6 ) is preferable when comprehensively judging solubility in a solvent, charge / discharge characteristics when used in a secondary battery, output characteristics, cycle characteristics, and the like.
  • the concentration of these electrolytes in the nonaqueous electrolytic solution is not particularly limited, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.7 mol / L or more. Moreover, the upper limit is 2 mol / L or less normally, Preferably it is 1.8 mol / L or less, More preferably, it is 1.7 mol / L or less. If the concentration is too low, the electrical conductivity of the electrolyte solution may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, and the performance of the lithium ion secondary battery may be reduced. May decrease.
  • non-aqueous solvent a known non-aqueous solvent is used as an electrolyte of a non-aqueous electrolyte for a lithium ion secondary battery, and examples thereof include the following.
  • Cyclic carbonate The alkylene group constituting the cyclic carbonate preferably has 2 to 6 carbon atoms, particularly preferably 2 to 4 carbon atoms. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Of these, ethylene carbonate and propylene carbonate are preferable.
  • Chain carbonate As the chain carbonate, dialkyl carbonate is preferable, and the number of carbon atoms of the alkyl group is preferably 1 to 5%, particularly preferably 1 to 4. Specifically, for example, symmetrical chain carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; asymmetric chain carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate And dialkyl carbonates. Of these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable.
  • Chain ester methyl acetate, ethyl acetate, propyl acetate, methyl propionate, etc. are mentioned.
  • Cyclic ether Tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and the like.
  • the additive is not particularly limited as long as it is known to be used as an additive for a non-aqueous electrolyte solution for a lithium ion secondary battery, and examples thereof include the following.
  • a heterocyclic compound containing nitrogen and / or sulfur or sulfur is not particularly limited, but includes 1-methyl-2-pyrrolidinone, 1,3-dimethyl- 2-pyrrolidinone, Pyrrolidinones such as 1,5-dimethyl-2-pyrrolidinone, 1-ethyl-2-pyrrolidinone, 1-cyclohexyl-2-pyrrolidinone; 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, 3-cyclohexyl- Oxazolidinones such as 2-oxazolidinone; piperidones such as 1-methyl-2-piperidone and 1-ethyl-2-piperidone; 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidi Imidazolidinones such as non-sulfones; sulfolane, 2-methylsulfolane, 3-methylsulfolane,
  • Sulfolanes Sulfolenes; sulfites such as ethylene sulfite and propylene sulfite; 1,3-propane sultone, 1-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1,4 -Sultone such as butane sultone, 1,3-propene sultone, 1,4-butene sultone, and the like.
  • Cyclic carboxylic acid ester is not particularly limited, but ⁇ -butyrolactone, ⁇ -valerolactone, ⁇ -hexalactone, ⁇ -heptalactone, ⁇ -octalactone, ⁇ -nonalactone, ⁇ -decalactone , ⁇ -undecalactone, ⁇ -dodecalactone, ⁇ -methyl- ⁇ -butyrolactone, ⁇ -ethyl- ⁇ -butyrolactone, ⁇ -propyl- ⁇ -butyrolactone, ⁇ -methyl- ⁇ -valerolactone, ⁇ -ethyl- ⁇ -Valerolactone, ⁇ , ⁇ -dimethyl- ⁇ -butyrolactone, ⁇ , ⁇ -dimethyl- ⁇ -valerolactone, ⁇ -valerolactone, ⁇ -hexalactone, ⁇ -octalactone, ⁇ -nonalactone, ⁇ -nonalactone, ⁇ -buty
  • Fluorine-containing cyclic carbonate is not particularly limited, and examples thereof include fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, tetrafluoroethylene carbonate, and trifluoropropylene carbonate.
  • aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, etc .; 2-fluoro Partially fluorinated products of the above aromatic compounds such as biphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoro Examples thereof include fluorine-containing anisole compounds such as anisole.
  • examples of the negative electrode film forming material include succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, and the like.
  • succinic anhydride and maleic anhydride are used. Two or more of these may be used in combination.
  • methyl methanesulfonate, busulfan, and dimethylsulfone are used. Two or more of these may be used in combination.
  • lithium manganate which is an active material
  • scale-like graphite average particle size: 20 ⁇ m
  • polyvinylidene fluoride as a binder
  • NMP N-methyl-2-pyrrolidone
  • the kneaded slurry was substantially evenly and evenly formed on both surfaces of an aluminum foil (positive electrode current collector) as a current collector having a thickness of 20 ⁇ m.
  • a predetermined amount was applied uniformly. Thereafter, it was dried, pressed to a predetermined density, and further cut to a width of 30 mm ⁇ 45 mm to obtain a positive electrode plate.
  • the prepared positive electrode plate and negative electrode plate are opposed to each other through a polyethylene resin separator made of a microporous film made by Asahi Kasei E-materials, and metal particles (Cu or Ni) are placed between the positive electrode plate and the resin separator.
  • metal particles Cu or Ni
  • the metal particles used were spherical. Although one metal particle is used in this example, it is considered that one or more metals or metal compounds may actually be mixed.
  • the laminate bag After pouring 1 mL of electrolyte containing 1 mol / L of lithium hexafluorophosphate as an electrolyte into a solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 2, the laminate bag was vacuumed with a vacuum welding device. Then, the other end of the bag was thermally welded and sealed to produce a lithium ion secondary battery with a design capacity of 40 mAh.
  • the resistance of the internal short circuit of the lithium ion secondary battery thus produced was evaluated by the method shown below.
  • species, and the particle size of the metal was charged in 25 degreeC environment.
  • a constant current and constant voltage method was adopted as a charging method. After constant current charging at 20 mA, switching to constant voltage charging was performed when the battery voltage reached 4.2 V, and charging was performed for a total of 5 hours.
  • a battery having a current value higher than 0.1 mA (compared to a battery into which no metal was introduced) at the time of constant voltage charging after 5 hours was defined as “with short circuit”.
  • the volume of the metal particles (V1) and the pore volume of the resin separator (V2) were calculated as follows.
  • Metal particle volume (V1) (1/2 of metal particle size) 3 ⁇ 4 ⁇ / 3
  • Resin separator pore volume (V2) (1 ⁇ m 2 ) ⁇ (resin separator thickness) ⁇ (separator porosity)
  • the particle size of the metal particles was measured using a microscope (manufactured by Keyence, VHX-2000) at a magnification of 1000 times.
  • a battery was manufactured by introducing one metal particle (copper and nickel) having a different particle size (particle size) on the positive electrode plate by changing the thickness of the separator, the metal species, and the particle size of the metal. did.
  • the evaluation results are shown in Table 1.
  • Example 1 and Comparative Examples 1 to 3 a resin separator having a thickness of 16 ⁇ m was used.
  • Examples 4 to 6 and Comparative Example 6 a separator having a thickness of 36 ⁇ m was used.
  • Examples 7 to 9 and Comparative Example 7 a separator having a thickness of 40 ⁇ m was used.
  • the porosity of the resin separator is in the range of 30 to 50%, and the pore volume of the resin separator obtained from these porosity is 4.19 ⁇ 10 3 to 3.35 ⁇ 10.
  • the range is 4 ⁇ m (the pore volume per 1 ⁇ m 2 is 6.2 to 16.8 ⁇ m 3 ).
  • Examples 1 to 9 spherical Cu metal having a particle size of 20 to 40 ⁇ m was used, and in Examples 10 and 11, spherical Ni metal having a particle size of 20 to 40 ⁇ m was used.
  • the volume of the metal particles is included in the range of 4.19 ⁇ 10 3 to 3.35 ⁇ 10 4 ⁇ m 3 . Note that the range of the particle diameter is only required to satisfy the above-described relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 per 1 ⁇ m 2 of the resin separator. It has been confirmed that the effect can be obtained.
  • the metal or metal compound particle volume V1 and the pore volume V2 per 1 ⁇ m 2 of the resin separator satisfy the relationship of V1 / V2 ⁇ 2250. Since the pore volume V2 per 1 ⁇ m 2 of the resin separator is adjusted with respect to the volume V1, the dendrite of the reduced metal or metal compound stays in the separator from the surface of the negative electrode plate, penetrates the separator and passes through the positive electrode It can prevent reaching the board. As a result, a short circuit between the positive electrode and the negative electrode due to dendrites is prevented, and an internal short circuit of the battery can be prevented. Therefore, according to the present invention, a highly safe lithium ion secondary battery can be provided.

Abstract

Provided is a highly safe lithium ion secondary battery. An electrode plate group is configured to have: a resin separator having a thickness of 15-50 μm; and a positive electrode plate and a negative electrode plate, which are laminated with the resin separator being interposed therebetween. Particles of a metal or a metal compound, which have particle diameters of 20 μm or more, are present between the resin separator and the positive electrode plate or the negative electrode plate. The volume (V1) of the particles of a metal or a metal compound and the void volume (V2) per 1 μm2 of the resin separator satisfy the following relational expression: V1/V2 < 2,250.

Description

リチウムイオン二次電池Lithium ion secondary battery
　本発明は、正極板と負極板とが樹脂セパレータを介して積層されてなる極板群を備えるリチウムイオン二次電池に関するものである。 The present invention relates to a lithium ion secondary battery including an electrode plate group in which a positive electrode plate and a negative electrode plate are laminated via a resin separator.
　リチウムイオン二次電池は、高エネルギー密度であるメリットを活かして、主にノートパソコン、携帯電話等のポータブル機器の電源に使用されている。例えば、円筒形リチウムイオン二次電池の内部は、正極及び負極の両電極が共に活物質が金属箔に塗着された帯状であり、樹脂セパレータを挟んでこれら両電極が直接接触しないように断面が渦巻状等に捲回された捲回群が形成された捲回式の構造になっている。そして、この捲回群が電池容器となる円筒形の電池缶内に収納され、電解液注液後に封口されている。 Lithium ion secondary batteries are mainly used as power sources for portable devices such as notebook computers and mobile phones, taking advantage of the high energy density. For example, the inside of a cylindrical lithium ion secondary battery has a strip shape in which both the positive electrode and the negative electrode are coated with an active material on a metal foil, and the cross section is such that these electrodes are not in direct contact with a resin separator in between. It has a wound structure in which a wound group is formed in which a spiral is wound. And this winding group is accommodated in the cylindrical battery can used as a battery container, and is sealed after electrolyte solution injection.
　一般的な円筒形リチウムイオン二次電池の外形寸法は、１８６５０型と呼ばれる、直径１８ｍｍ、高さ６５ｍｍの寸法を有する小型民生用リチウムイオン二次電池として広く普及している。この１８６５０型リチウムイオン二次電池には、正極活物質として高容量、長寿命を特徴とするコバルト酸リチウムが主に用いられている。１８６５０型リチウムイオン二次電池の電池容量は、概ね１．０Ａｈ～２．５Ａｈ（３．７Ｗｈ～９．３Ｗｈ）程度である。 The external dimensions of a general cylindrical lithium ion secondary battery are widely used as a small-sized consumer lithium ion secondary battery having a diameter of 18 mm and a height of 65 mm, which is called 18650 type. In this 18650 type lithium ion secondary battery, lithium cobalt oxide characterized by high capacity and long life is mainly used as a positive electrode active material. The battery capacity of the 18650 type lithium ion secondary battery is about 1.0 Ah to 2.5 Ah (3.7 Wh to 9.3 Wh).
　最近、リチウムイオン二次電池は、民生用途にとどまらず、太陽光や風力発電といった自然エネルギー向け大規模蓄電システム用途への展開が期待されている。大規模蓄電システム用途では、システムあたりの電力量が数ＭＷｈ必要であり、上述の１８６５０電池を用いる場合は、大量（１００万本程度）のリチウムイオン二次電池が必要となる。通常、リチウムイオン二次電池は、電池１本毎にセルコントローラーが取り付けられており、電池状態を検知している。そのため、大量な電池を必要とするシステムでは、必要なセルコントローラーも大量に必要であり、コストの大幅な増加を招く。そこで、電池１本あたりの容量を高くして、システムとして必要な電池本数及びセルコントローラー数を低減する必要がある。 Recently, lithium-ion secondary batteries are expected to be used not only for consumer applications but also for large-scale power storage systems for natural energy such as solar power and wind power generation. In a large-scale power storage system application, the amount of electric power per system is required to be several MWh. When the above-described 18650 battery is used, a large amount (about 1 million) of lithium ion secondary batteries are required. Usually, in the lithium ion secondary battery, a cell controller is attached to each battery, and the battery state is detected. For this reason, in a system that requires a large amount of batteries, a large amount of necessary cell controllers are also required, resulting in a significant increase in cost. Therefore, it is necessary to increase the capacity per battery to reduce the number of batteries and the number of cell controllers required for the system.
　特に、高容量電池では、従来の１８６５０電池とは異なり、電池に蓄えられるエネルギーが高くなるため、非定常時の安全性の確保が厳しくなるという課題がある。そこで、特許文献１に示すように、セパレータに電子線照射処理を行い、高温保存時のセパレータの収縮による内部短絡を防止するリチウムイオン二次電池用セパレータの製造方法が知られている。 Especially, a high-capacity battery has a problem that, unlike a conventional 18650 battery, energy stored in the battery becomes high, so that it is difficult to ensure safety during unsteady times. Therefore, as shown in Patent Document 1, a method of manufacturing a separator for a lithium ion secondary battery in which an electron beam irradiation treatment is performed on the separator to prevent an internal short circuit due to the shrinkage of the separator during high temperature storage is known.
特開２００３－２２７９３号公報JP 2003-22793 A
　一方、電池の製造工程において、金属または金属化合物が何らかの要因で異物として混入する場合がある。本発明の発明者らは、このような異物として電池内に存在する金属または金属化合物が起点となって、電池の内部短絡が発生する可能性が高くなることを見出した。発明者らの研究では、特に、膜厚が１５μｍ～５０μｍの樹脂セパレータを用いた場合において、粒径が２０μｍ以上の金属又は金属化合物の粒子がセル内に存在するときに、内部短絡の危険性が高くなることを突き止めた。 On the other hand, in the battery manufacturing process, a metal or metal compound may be mixed as a foreign substance for some reason. The inventors of the present invention have found that the possibility of occurrence of an internal short circuit of the battery is increased, starting from the metal or metal compound present in the battery as such a foreign substance. In our research, especially when a resin separator with a film thickness of 15 μm to 50 μm is used, there is a risk of internal short circuit when metal or metal compound particles having a particle size of 20 μm or more are present in the cell. Found out that it would be expensive.
　このように電池内に異物として混入した金属または金属化合物の粒子は、リチウムイオン二次電池が充放電を繰り返す過程で、電池内でデンドライトとして成長することにより内部短絡を発生させる。このデンドライトに起因する内部短絡は、概ね次の（１）～（３）のような機構で発生する。（１）金属または金属化合物は、正極側で酸化されて溶解し（Ｍ→Ｍｘ＋＋ｘｅ－）、金属イオンの状態でセパレータを透過し、負極側で還元されて負極板の表面に析出する（Ｍｘ＋＋ｘｅ－→Ｍ）。（２）負極側で還元された金属または金属化合物は、セパレータの空隙内にも析出する。（３）セパレータ内に析出した金属または金属化合物は、その後正極板まで達して、正極と負極が短絡する（すなわち、電池内で内部短絡が生じる）。特に、金属または金属化合物の粒子が、樹脂セパレータと正極板との間に存在する場合に、このような電池内の内部短絡が発生し易い傾向がある。 Thus, the metal or metal compound particles mixed in the battery as a foreign substance grow as a dendrite in the battery in the process of repeated charge / discharge of the lithium ion secondary battery, thereby generating an internal short circuit. The internal short circuit caused by the dendrite is generally generated by the following mechanisms (1) to (3). (1) The metal or metal compound is oxidized and dissolved on the positive electrode side (M → M x + + xe − ), passes through the separator in the form of metal ions, is reduced on the negative electrode side, and is deposited on the surface of the negative electrode plate ( M x + + xe − → M). (2) The metal or metal compound reduced on the negative electrode side also precipitates in the voids of the separator. (3) The metal or metal compound deposited in the separator then reaches the positive electrode plate, and the positive electrode and the negative electrode are short-circuited (that is, an internal short circuit occurs in the battery). In particular, when metal or metal compound particles are present between the resin separator and the positive electrode plate, such an internal short circuit in the battery tends to occur.
　電池が短絡すると急激な発熱が起こり、電池の安全性に問題を生じる可能性が高くなる。特に、大規模蓄電システムでは、電池容量が１０Ａｈ～３００Ａｈ程度に想定されており、電池に蓄えられるエネルギーが高くなるため、安全性をさらに確保する必要がある。 When a battery is short-circuited, sudden heat generation occurs, and there is a high possibility of causing a problem in battery safety. In particular, in a large-scale power storage system, the battery capacity is assumed to be about 10 Ah to 300 Ah, and the energy stored in the battery becomes high, so it is necessary to further ensure safety.
　本発明の目的は、金属または金属化合物が電池内に異物として混入した場合でも、内部短絡を防止して、安全性の高いリチウムイオン二次電池を提供することにある。 An object of the present invention is to provide a highly safe lithium ion secondary battery that prevents an internal short circuit even when a metal or a metal compound is mixed as a foreign substance in the battery.
　本発明が改良の対象とするリチウムイオン二次電池は、厚みが１５～５０μｍの樹脂セパレータと、該樹脂セパレータを介して積層された正極板及び負極板とを有する極板群を備え、樹脂セパレータと正極板または負極板との間に粒径が２０μｍ以上の金属または金属化合物の粒子が存在するリチウムイオン二次電池である。 A lithium ion secondary battery to be improved by the present invention includes an electrode plate group having a resin separator having a thickness of 15 to 50 μm, and a positive electrode plate and a negative electrode plate laminated with the resin separator interposed therebetween. A lithium ion secondary battery in which particles of a metal or metal compound having a particle size of 20 μm or more exist between the positive electrode plate or the negative electrode plate.
　ここで、「樹脂セパレータ」には、１枚の樹脂セパレータ・シートで構成された樹脂セパレータ、および、複数枚の樹脂セパレータ・シートを積層して構成された樹脂セパレータの両者が含まれる。 Here, the “resin separator” includes both a resin separator constituted by a single resin separator sheet and a resin separator constituted by laminating a plurality of resin separator sheets.
 本明細書において「金属または金属化合物の粒子」は、正極活物質または負極活物質を構成するものではない。「金属または金属化合物の粒子」は、電池の製造過程で電極と端子の溶接等により発生した異物として電池内に存在するものであると予想される。「粒子」としては、例えば、粒状、フレーク状、球状、柱状、不規則形状などが挙げられる。 に お い て In the present specification, the “metal or metal compound particles” do not constitute a positive electrode active material or a negative electrode active material. The “metal or metal compound particles” are expected to be present in the battery as foreign matter generated by welding of electrodes and terminals in the battery manufacturing process. Examples of the “particles” include granular, flaky, spherical, columnar, and irregular shapes.
 前記粒状とは、不規則形状のものではなくほぼ等しい寸法をもつ形状である（ＪＩＳ　Ｚ２５００：２０００）。 The granular shape is not an irregular shape but a shape having almost equal dimensions (JIS Z2500: 2000).
　前記フレーク状（片状）とは、板のような形状であり（ＪＩＳ　Ｚ２５００：２０００）、鱗のように薄い板状であることから鱗片状とも言われ、本発明においては、ＳＥＭ観察の結果から解析を行い、アスペクト比（粒子径ａ／平均厚さｔ）が２～１００の範囲を片状とする。ここでいう粒子径ａは、片状の粒子を平面視したときの面積Ｓの平方根として定義するものとし、これを本願の粒径とする。 The flake shape (strip shape) is a plate-like shape (JIS Z2500: 2000) and is also called a scaly shape because it is thin like a scale. In the present invention, as a result of SEM observation The aspect ratio (particle diameter a / average thickness t) is 2 to 100 in the form of a piece. The particle diameter a here is defined as the square root of the area S when the flaky particles are viewed in plan, and this is the particle diameter of the present application.
　前記「球状」とは、ほぼ球に近い形状である（ＪＩＳ　Ｚ２５００：２０００参照）。必ずしも真球状である必要はなく、粒子の長径（ＤＬ）と短径（ＤＳ）との比（ＤＬ）／（ＤＳ）（球状係数あるいは真球度と言うことがある）が１．０～１．２の範囲にあるものとし、本願の粒径とは長径（ＤＬ）を指すものとする。 The “spherical shape” is a shape almost similar to a sphere (see JIS Z2500: 2000). The spherical shape is not necessarily required, and the ratio of the major axis (DL) to the minor axis (DS) of the particle (DL) / (DS) (sometimes referred to as spherical coefficient or sphericity) is 1.0 to 1. .2 and the particle size in the present application refers to the major axis (DL).
　前記柱状とは、略円柱、略多角柱等が挙げられ、本願の粒径とは柱の高さを指すものとする。 The columnar shape includes a substantially cylindrical column, a substantially polygonal column, and the like, and the particle size in the present application refers to the height of the column.
 なお、「粒径」は、マイクロスコープにより倍率が１００～１０００倍、又は走査型電子顕微鏡により１０００～１００００倍の条件で測定することができる。粒径が２０μｍ以上の金属または金属化合物に限定したのは、粒径が２０μｍ未満の金属または金属化合物の粒子であれば、電池内で異物として存在しても内部短絡を引き起こす可能性は少ないからである。なお、粒径が２０μｍ以上の金属または金属化合物のうち、電池の製造工程で混入する金属または金属化合物の粒径は最大で１５０μｍ程度である。このような金属または金属化合物の粒子の粒径を体積に換算すると、金属または金属化合物の体積は約４．１９×１０３～１．７７×１０６μｍ３の範囲となる。なお、製造過程で電池内に混入する可能性のある金属は、銅、鉄、ニッケル、アルミニウム、マンガン、及びクロムのうち少なくとも１種の金属である。また、製造過程で電池内に混入する可能性のある金属化合物は、銅、鉄、ニッケル、アルミニウム、マンガン、及びクロムのうち少なくとも１種の金属の酸化物である。 The “particle size” can be measured under the conditions of a magnification of 100 to 1000 times with a microscope or 1000 to 10,000 times with a scanning electron microscope. The reason why the particle size is limited to a metal or metal compound having a particle size of 20 μm or more is that if it is a metal or metal compound particle having a particle size of less than 20 μm, it is less likely to cause an internal short circuit even if it exists as a foreign substance in the battery. It is. Of the metals or metal compounds having a particle size of 20 μm or more, the maximum particle size of the metal or metal compound mixed in the battery manufacturing process is about 150 μm. When the particle diameter of such metal or metal compound particles is converted to volume, the volume of the metal or metal compound is in the range of about 4.19 × 10 3 to 1.77 × 10 6 μm 3 . In addition, the metal which may be mixed in the battery in the manufacturing process is at least one metal selected from copper, iron, nickel, aluminum, manganese, and chromium. In addition, the metal compound that may be mixed in the battery during the manufacturing process is an oxide of at least one metal among copper, iron, nickel, aluminum, manganese, and chromium.
　本発明のリチウムイオン二次電池は、金属または金属化合物の粒子の体積をＶ１、樹脂セパレータの１μｍ２当たりの空孔体積をＶ２としたときに、Ｖ１とＶ２が、下記式（１）の関係を満たすように調整されている。 In the lithium ion secondary battery of the present invention, when the volume of the metal or metal compound particles is V1, and the pore volume per 1 μm 2 of the resin separator is V2, V1 and V2 are represented by the following formula (1). It is adjusted to meet.
　　Ｖ１／Ｖ２＜２２５０　…（１）
　ここで、「金属または金属化合物の粒子の体積Ｖ１」は、金属または金属化合物の質量と密度から算出する。なお、金属または金属化合物の粒子が球状の場合は、｛粒径（μｍ）×（１／２）｝３×４／３πから算出してもよい。また、「樹脂セパレータの１μｍ２当たりの空孔体積Ｖ２」は、樹脂セパレータの厚さと単位面積（１μｍ２）を乗じて算出される体積に樹脂セパレータの空孔率を乗じて算出する。 V1 / V2 <2250 (1)
Here, “the volume V1 of the metal or metal compound particles” is calculated from the mass and density of the metal or metal compound. In addition, when the particle | grains of a metal or a metal compound are spherical, you may calculate from {particle size (micrometer) x (1/2)} 3 * 4/3 (pi). The “pore volume V2 per 1 μm 2 of the resin separator” is calculated by multiplying the volume calculated by multiplying the thickness of the resin separator and the unit area (1 μm 2 ) by the porosity of the resin separator.
　「Ｖ１／Ｖ２」の関係式は、金属または金属化合物の粒子の体積Ｖ１を樹脂セパレータの空孔体積Ｖ２で除することを意味する。また、「Ｖ１／Ｖ２＜２２５０」の関係式はＶ１／Ｖ２の値が２２５０より小さいことを意味する。 The relational expression “V1 / V2” means that the volume V1 of the metal or metal compound particles is divided by the pore volume V2 of the resin separator. The relational expression “V1 / V2 <2250” means that the value of V1 / V2 is smaller than 2250.
　本発明のように、異物として混入した金属または金属化合物の粒子の体積を考慮して、樹脂セパレータの空孔体積を調整すると、還元析出した金属または金属化合物のデンドライトが、負極板の表面から樹脂セパレータ内に留まり、樹脂セパレータを貫通して正極板まで達するのを防ぐことができる。その結果、デンドライトによる正極と負極の短絡が防止され、電池の内部短絡を防ぐことができる。なお、Ｖ１とＶ２の関係式が２２５０以上の場合は、デンドライト等の析出物が樹脂セパレータから正極まで達し易くなり、正極と負極の短絡が発生し易くなる。 When the pore volume of the resin separator is adjusted in consideration of the volume of the metal or metal compound particles mixed in as a foreign substance as in the present invention, the reduction-precipitated metal or metal compound dendrite is transferred from the surface of the negative electrode plate to the resin. It stays in the separator and can be prevented from reaching the positive electrode plate through the resin separator. As a result, a short circuit between the positive electrode and the negative electrode due to dendrites is prevented, and an internal short circuit of the battery can be prevented. When the relational expression between V1 and V2 is 2250 or more, precipitates such as dendrite easily reach the positive electrode from the resin separator, and a short circuit between the positive electrode and the negative electrode is likely to occur.
　金属または金属化合物の粒子の体積Ｖ１と樹脂セパレータの空孔体積Ｖ２との関係は、好ましくは、下記（２）式の関係を満たすように調整されている。 The relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 of the resin separator is preferably adjusted to satisfy the relationship of the following equation (2).
　　１５０＜Ｖ１／Ｖ２＜２２５０　…（２）
　ここで、「１５０＜Ｖ１／Ｖ２＜２２５０」の関係式は、Ｖ１／Ｖ２の値が２２５０よりも小さいことに加えて、さらにＶ１／Ｖ２の値が１５０よりも大きいことを意味する。Ｖ１／Ｖ２の値が２２５０より小さい範囲であっても、Ｖ１／Ｖ２の値が１５０以下の範囲では、金属または金属化合物の粒子の体積Ｖ１に対して、樹脂セパレータの空孔体積Ｖ２が相対的に著しく大きくなる。樹脂セパレータの空孔体積が相対的に大きくなりすぎると、デンドライト等の析出物は樹脂セパレータを貫通し易くなり、正極と負極の短絡が発生し易くなる。そのため、Ｖ１／Ｖ２の値は、上記のように１５０よりも大きくなるように調整するのが好ましい。 150 <V1 / V2 <2250 (2)
Here, the relational expression “150 <V1 / V2 <2250” means that the value of V1 / V2 is larger than 150 in addition to the value of V1 / V2 being smaller than 2250. Even if the value of V1 / V2 is smaller than 2250, if the value of V1 / V2 is 150 or less, the pore volume V2 of the resin separator is relative to the volume V1 of the metal or metal compound particles. Becomes significantly larger. When the pore volume of the resin separator becomes relatively large, precipitates such as dendrites tend to penetrate the resin separator, and a short circuit between the positive electrode and the negative electrode is likely to occur. Therefore, it is preferable to adjust the value of V1 / V2 to be larger than 150 as described above.
　金属または金属化合物の粒子の体積Ｖ１と樹脂セパレータの空孔体積Ｖ２との関係は、より好ましくは下記（３）式の関係を満たすように調整されている。 The relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 of the resin separator is more preferably adjusted to satisfy the relationship of the following formula (3).
　　１６５＜Ｖ１／Ｖ２＜２２２０　…（３）
　Ｖ１／Ｖ２の値を、２２２０より小さく、かつ、１６５より大きい範囲になるように調整すると、金属または金属化合物の粒径が樹脂セパレータと正極板との間に存在する場合（電池の内部短絡が発生し易い環境下）でも、負極板の表面から延びるデンドライト等の析出物が樹脂セパレータ内に留まり易くなり、正極と負極の短絡を確実に防ぐことができる。 165 <V1 / V2 <2220 (3)
When the value of V1 / V2 is adjusted to be smaller than 2220 and larger than 165, when the particle size of the metal or metal compound exists between the resin separator and the positive electrode plate (the internal short circuit of the battery is Even in an environment in which it is likely to occur, deposits such as dendrites extending from the surface of the negative electrode plate tend to stay in the resin separator, and the short circuit between the positive electrode and the negative electrode can be reliably prevented.
　樹脂セパレータには、空孔率が３０～５０％に調整された樹脂セパレータを用いるのが好ましい。このような空孔率を有する樹脂セパレータを用いることにより、Ｖ１／Ｖ２の値を、粒径が２０μｍ以上の金属または金属化合物の粒子が電池内に混入した場合でも内部短絡が発生し難い値に、調整し易くなる。 It is preferable to use a resin separator having a porosity adjusted to 30 to 50% as the resin separator. By using a resin separator having such a porosity, the value of V1 / V2 is reduced to a value in which an internal short circuit is unlikely to occur even when metal or metal compound particles having a particle size of 20 μm or more are mixed in the battery. Easy to adjust.
　樹脂セパレータには、ポリプロピレン及びポリエチレンの少なくとも一つからなるポリオレフィンを材質として含む樹脂セパレータを用いるのが好ましい。このようなポリオレフィンからなる樹脂セパレータを用いて樹脂セパレータを構成することにより、電池の内部短絡を防止する機能を左右する樹脂セパレータの空孔率（または空孔体積）の制御が容易になるからである。 It is preferable to use a resin separator containing a polyolefin made of at least one of polypropylene and polyethylene as a material for the resin separator. By configuring the resin separator using such a polyolefin resin separator, it becomes easy to control the porosity (or void volume) of the resin separator that affects the function of preventing internal short circuit of the battery. is there.
　以下、本発明の実施の形態について、詳細に説明する。本実施の形態では、正極板と負極板とを樹脂セパレータを介して積層した積層型リチウムイオン二次電池を対象とするが、本発明は正極板と負極板とを樹脂セパレータ介して積層してなる積層体を巻回した巻回形リチウムイオン電池にも当然にして適用できるものである。 Hereinafter, embodiments of the present invention will be described in detail. Although the present embodiment is directed to a stacked lithium ion secondary battery in which a positive electrode plate and a negative electrode plate are stacked via a resin separator, the present invention includes a positive electrode plate and a negative electrode plate stacked via a resin separator. Naturally, the present invention can also be applied to a wound lithium ion battery in which a laminated body is wound.
（１）正極板
　正極板は、正極活物質と結着材とを含有する正極活物質層を、正極集電体上に形成して作製される。具体的には、正極活物質と結着材、並びに必要に応じて導電材及び増粘材等を乾式で混合してシート状にしたものを正極集電体に圧着するか、または、これらの材料を液体媒体に溶解、分散させてスラリーとして正極集電体に塗布し、乾燥することにより、正極活物質層が正極集電体上に形成させる。 (1) Positive electrode plate A positive electrode plate is produced by forming a positive electrode active material layer containing a positive electrode active material and a binder on a positive electrode current collector. Specifically, a positive electrode active material and a binder, and if necessary, a conductive material and a thickener mixed in a dry form into a sheet form are pressure-bonded to the positive electrode current collector, or these The material is dissolved and dispersed in a liquid medium, applied as a slurry to the positive electrode current collector, and dried to form a positive electrode active material layer on the positive electrode current collector.
　正極活物質としては、リチウムを挿入脱離、溶解析出可能な公知のリチウムと遷移金属の複合酸化物を単独または２種以上とを混合したものを用いることができる。リチウム金属と遷移金属の複合酸化物の例としては、マンガン酸リチウム、ニッケル酸リチウム、コバルト酸リチウム、リチウム燐酸鉄等が挙げられる。これらの複合酸化物は、単相のもの、遷移金属の一部を異種元素で置換したもの、または表面を酸化物や炭素でコーティングしたものでもよい。 As the positive electrode active material, a known lithium and transition metal composite oxide capable of inserting, desorbing and dissolving lithium can be used alone or in combination of two or more. Examples of the composite oxide of lithium metal and transition metal include lithium manganate, lithium nickelate, lithium cobaltate, and lithium iron phosphate. These composite oxides may be of a single phase, a transition metal partially substituted with a different element, or a surface coated with an oxide or carbon.
　正極用導電材としては、公知の導電材を任意に用いることができる。具体例としては、銅、ニッケル等の金属材料；天然黒鉛、人造黒鉛等の黒鉛（グラファイト）；アセチレンブラック等のカーボンブラック；ニードルコークス等の無定形炭素等の炭素質材料等が挙げられる。なお、これらは、１種を単独で用いてもよく、２種以上を任意の組み合わせ及び比率で併用してもよい。 As the positive electrode conductive material, a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel; graphite such as natural graphite and artificial graphite (graphite); carbon black such as acetylene black; and carbonaceous materials such as amorphous carbon such as needle coke. In addition, these may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.
　正極活物質層の製造に用いる結着材としては、特に限定されず、塗布法の場合は、電極製造時に用いる液体媒体に対して溶解または分散する材料であれば良い。結着材の具体例としては、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、ポリメチルメタクリレート、ポリイミド、芳香族ポリアミド、セルロース、ニトロセルロース等の樹脂系高分子； ＳＢＲ（スチレン－ブタジエンゴム）、ＮＢＲ（アクリロニトリル－ブタジエンゴム） 、フッ素ゴム、イソプレンゴム、ブタジエンゴム、エチレン－プロピレンゴム等のゴム状高分子； スチレン・ブタジエン・スチレンブロック共重合体又はその水素添加物、ＥＰＤＭ（エチレン・プロピレン・ジエン三元共重合体）、スチレン・エチレン・ブタジエン・エチレン共重合体、スチレン・イソプレン・スチレンブロック共重合体、またはその水素添加物等の熱可塑性エラストマー状高分子；シンジオタクチック－１ ，２－ポリブタジエン、ポリ酢酸ビニル、エチレン・酢酸ビニル共重合体、プロピレン・α－オレフィン共重合体等の軟質樹脂状高分子； ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン、フッ素化ポリフッ化ビニリデン、ポリテトラフルオロエチレン・エチレン共重合体、ポリテトラフルオロエチレン・フッ化ビニリデン共重合体、等のフッ素系高分子；アルカリ金属イオン（特にリチウムイオン）のイオン伝導性を有する高分子組成物等が挙げられる。なお、これらの物質は、１種を単独で用いても良く、２種以上を任意の組み合わせ及び比率で併用しても良い。好ましくは、正極の安定性の観点から、ポリフッ化ビニリデン（ＰＶｄＦ）やポリテトラフルオロエチレン・フッ化ビニリデン共重合体、等のフッ素系高分子が良い。 The binder used for manufacturing the positive electrode active material layer is not particularly limited, and in the case of a coating method, any material that dissolves or disperses in the liquid medium used during electrode manufacturing may be used. Specific examples of the binder include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose; SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene) Rubber) Rubber-like polymers such as rubber, fluoro rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber; ), Thermoplastic elastomeric polymers such as styrene / ethylene / butadiene / ethylene copolymers, styrene / isoprene / styrene block copolymers, or hydrogenated products thereof; syndiotactic-1, 2-polybutadiene Soft resinous polymers such as polyethylene, polyvinyl acetate, ethylene / vinyl acetate copolymer, propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetra Fluoropolymers such as fluoroethylene / ethylene copolymer and polytetrafluoroethylene / vinylidene fluoride copolymer; polymer compositions having ion conductivity of alkali metal ions (particularly lithium ions), and the like. In addition, these substances may be used individually by 1 type, and may use 2 or more types together by arbitrary combinations and ratios. Preferably, from the viewpoint of the stability of the positive electrode, a fluorine-based polymer such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene / vinylidene fluoride copolymer is preferable.
　塗布、乾燥によって得られた正極活物質層は、正極活物質の充填密度を上げるために、ハンドプレス、ローラープレス等により圧密化することが好ましい。 The positive electrode active material layer obtained by coating and drying is preferably consolidated by a hand press, a roller press or the like in order to increase the packing density of the positive electrode active material.
　正極集電体の材質としては特に制限は無く、公知のものを任意に用いることができる。具体例としては、アルミニウム、ステンレス鋼、ニッケルメッキ、チタン、タンタル等の金属材料； カーボンクロス、カーボンペーパー等の炭素質材料が挙げられる。中でも金属材料、特にアルミニウムが好ましい。 The material for the positive electrode current collector is not particularly limited, and any known material can be used. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbonaceous materials such as soot carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.
　正極集電体の形態は特に制限されるものではなく、公知の形態を任意に用いることができる。具体例としては、金属材料の場合は、金属箔、金属円柱、金属コイル、金属板、金属薄膜、エキスパンドメタル、パンチメタル、発泡メタル等が挙げられる。炭素質材料の場合は、炭素板、炭素薄膜、炭素円柱等が挙げられる。これらのうち、金属薄膜が好ましい。なお、薄膜は適宜メッシュ状に形成してもよい。薄膜の厚さは任意であるが、通常１μｍ以上、好ましくは３μｍ以上、より好ましくは５μｍ以上、また、通常１ｍｍ以下、好ましくは１００μｍ以下、より好ましくは５０μｍ 以下である。薄膜がこの範囲よりも薄いと、集電体として必要な強度が不足する場合がある。逆に、薄膜がこの範囲よりも厚いと、取り扱い性が損なわれる場合がある。 The form of the positive electrode current collector is not particularly limited, and a known form can be arbitrarily used. Specific examples of the metal material include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punch metal, and foam metal. In the case of a carbonaceous material, a carbon plate, a carbon thin film, a carbon cylinder, etc. are mentioned. Of these, metal thin films are preferred. In addition, you may form a thin film suitably in mesh shape. The thickness of the thin film is arbitrary, but is usually 1 μm or more, preferably 3 μm or more, more preferably 5 μm or more, and usually 1 mm or less, preferably 100 μm or less, more preferably 50 μm or less. If the thin film is thinner than this range, the strength required for the current collector may be insufficient. Conversely, if the thin film is thicker than this range, the handleability may be impaired.
（２）負極板
　負極板は、電気化学的にリチウムイオンを吸蔵・放出可能な負極活物質を含む負極合材が、負極集電体の両面に塗布されている。負極活物質としては、炭素質材料、酸化スズや酸化ケイ素等の金属酸化物、金属複合酸化物、リチウム単体やリチウムアルミニウム合金等のリチウム合金、スズやケイ素等のリチウムと合金形成可能な金属等が挙げられる。これらは、１種を単独で用いても、２種以上を任意の組み合わせ及び比率で併用しても良い。中でも炭素質材料またはリチウム複合酸化物を用いるのが安全性の点から好ましい。 (2) Negative electrode plate As for the negative electrode plate, the negative electrode compound material containing the negative electrode active material which can electrochemically occlude / release lithium ion is apply | coated on both surfaces of the negative electrode collector. Examples of the negative electrode active material include carbonaceous materials, metal oxides such as tin oxide and silicon oxide, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, metals that can form alloys with lithium such as tin and silicon, etc. Is mentioned. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and a ratio. Among these, it is preferable from the viewpoint of safety to use a carbonaceous material or a lithium composite oxide.
　金属複合酸化物としては、リチウムを吸蔵、放出可能であれば特には制限されるものではないが、構成成分としてチタン及び／又はリチウムを含有していることが、高電流密度充放電特性の観点から好ましい。 The metal composite oxide is not particularly limited as long as it can occlude and release lithium, but it contains titanium and / or lithium as a constituent component in view of high current density charge / discharge characteristics. To preferred.
　炭素質材料としては、非晶質炭素、天然黒鉛、天然黒鉛に乾式のＣＶＤ（Ｃｈｅｍｉｃａｌ　Ｖａｐｏｒ　Ｄｅｐｏｓｉｔｉｏｎ）法や湿式のスプレイ法で形成される被膜を形成した複合炭素質材料、エポキシやフェノール等の樹脂原料、若しくは石油や石炭から得られるピッチ系材料を原料として焼成して造られる人造黒鉛、非晶質炭素材料などの炭素質材料、又は、リチウムと化合物を形成することでリチウムを吸蔵放出できるリチウム金属、リチウムと化合物を形成し、結晶間隙に挿入されることでリチウムを吸蔵放出できるケイ素、ゲルマニウム、スズなど１４族元素の酸化物若しくは窒化物を用いることができる。 Carbonaceous materials include amorphous carbon, natural graphite, composite carbonaceous materials in which a film formed by dry CVD (Chemical Vapor Deposition) method or wet spray method is formed on natural graphite, resins such as epoxy and phenol Lithium that can occlude and release lithium by forming a carbonaceous material such as artificial graphite and amorphous carbon material that is made by firing from raw materials or pitch-based materials obtained from petroleum or coal, or by forming a compound with lithium An oxide or nitride of a group 14 element such as silicon, germanium, tin, or the like, which forms a compound with metal, lithium, and is inserted into a crystal gap to absorb and release lithium, can be used.
　また、負極合材には負極活物質以外にも、導電材として性質の異なる炭素質材料を２種以上含有しても良い。 In addition to the negative electrode active material, the negative electrode mixture may contain two or more carbonaceous materials having different properties as a conductive material.
　負極集電体としては、公知のものを任意に用いることができる。負極の集電体としては、銅、ニッケル、ステンレス鋼、ニッケルメッキ鋼等の金属材料が挙げられ、中でも加工し易さとコストの点から銅が好ましい。負極集電体の形状は、集電体が金属材料の場合は、例えば金属箔、金属円柱、金属コイル、金属板、金属薄膜、エキスパンドメタル、パンチングメタル、発泡メタル等が挙げられる。中でも好ましくは金属薄膜、より好ましくは銅箔であり、更に好ましくは圧延法による圧延銅箔と、電解法による電解銅箔を負極集電体として用いることができる。銅箔の厚さが２５μｍよりも薄い場合は、純銅よりも強度の高い銅合金（リン青銅、チタン銅、コルソン合金、Ｃｕ－Ｃｒ－Ｚｒ合金等）を用いることができる。 As the negative electrode current collector, a known one can be arbitrarily used. Examples of the current collector for the negative electrode include copper, nickel, stainless steel, nickel-plated steel, and the like. Among these, copper is preferable from the viewpoint of ease of processing and cost. Examples of the shape of the negative electrode current collector include metal foil, metal cylinder, metal coil, metal plate, metal thin film, expanded metal, punching metal, and foam metal when the current collector is a metal material. Among these, a metal thin film is preferable, and a copper foil is more preferable. A rolled copper foil obtained by a rolling method and an electrolytic copper foil obtained by an electrolytic method can be used as the negative electrode current collector. When the thickness of the copper foil is less than 25 μm, a copper alloy (phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.) having higher strength than pure copper can be used.
　負極活物質を結着するバインダーとしては、非水系電解液や電極製造時に用いる溶媒に対して安定な材料であれば、特に制限はない。具体的には、ポリエチレン、ポリプロピレン、ポリエチレンテレフタレート、ポリメチルメタクリレート、芳香族ポリアミド、セルロース、ニトロセルロース等の樹脂系高分子；ＳＢＲ（スチレン－ブタジエンゴム）、イソプレンゴム、ブタジエンゴム、フッ素ゴム、ＮＢＲ（アクリロニトリル－ブタジエンゴム）、エチレン－プロピレンゴム等のゴム状高分子；スチレン・ブタジエン・スチレンブロック共重合体、又はその水素添加物；ＥＰＤＭ（エチレン・プロピレン・ジエン三元共重合体）、スチレン・エチレン・ブタジエン・スチレン共重合体、スチレン・イソプレン・スチレンブロック共重合体又はその水素添加物等の熱可塑性エラストマー状高分子； シンジオタクチック－１，２－ポリブタジエン、ポリ酢酸ビニル、エチレン・酢酸ビニル共重合体、プロピレン・α－オレフィン共重合体等の軟質樹脂状高分子；ポリフッ化ビニリデン、ポリテトラフルオロエチレン、フッ素化ポリフッ化ビニリデン、ポリテトラフルオロエチレン・エチレン共重合体等のフッ素系高分子；アルカリ金属イオン（特にリチウムイオン）のイオン伝導性を有する高分子組成物等が挙げられる。これらの成分は、１種を単独で用いても、２種以上を任意の組み合わせ及び比率で併用して用いても良い。 The binder for binding the negative electrode active material is not particularly limited as long as it is a material that is stable with respect to the non-aqueous electrolyte solution and the solvent used during electrode production. Specifically, resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, aromatic polyamide, cellulose, nitrocellulose; SBR (styrene-butadiene rubber), isoprene rubber, butadiene rubber, fluorine rubber, NBR ( Acrylonitrile-butadiene rubber), rubber-like polymers such as ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof; EPDM (ethylene / propylene / diene terpolymer), styrene / ethylene・ Thermoplastic elastomeric polymers such as butadiene / styrene copolymer, styrene / isoprene / styrene block copolymer or hydrogenated products thereof; Syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene Soft resinous polymers such as vinyl acetate copolymer and propylene / α-olefin copolymer; Fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene / ethylene copolymer Polymers: Polymer compositions having ionic conductivity of alkali metal ions (particularly lithium ions), and the like. These components may be used individually by 1 type, or may be used in combination of 2 or more types by arbitrary combinations and ratios.
（３）樹脂セパレータ
　樹脂セパレータは、両極間を電子的に絶縁する所定の機械的強度を有し、イオン透過度が大きく、かつ、正極に接する側における酸化性と負極側における還元性への耐性を兼ね備える樹脂が用いられる。このような樹脂としては、オレフィン系ポリマーが用いられる。具体的には、非水系電解液に対して安定で、保液性の優れた材料の中から選ぶのが好ましく、例えばポリプロピレン及びポリエチレンの少なくとも一つを材質として含む多孔性シートを用いるのが好ましい。樹脂セパレータの形態としては、薄膜形状で、孔径が０．０１～１μｍ、厚みが１５～５０μｍの微多孔性フィルム等が好適に用いられる。また、樹脂セパレータの空孔率は、３０～５０％が好ましく、３５～４５％がより好ましい。なお、本例の樹脂セパレータ（厚みが１５～５０μｍの樹脂セパレータ）は、１枚のセパレータで構成してもよく、２枚以上のセパレータを重ねて構成してもよい。 (3) Resin separator The resin separator has a predetermined mechanical strength that electrically insulates both electrodes, has a high ion permeability, and is resistant to oxidation on the side in contact with the positive electrode and reducibility on the negative electrode side. A resin having both is used. An olefin polymer is used as such a resin. Specifically, it is preferable to select from materials that are stable with respect to the non-aqueous electrolyte and have excellent liquid retention properties. For example, it is preferable to use a porous sheet containing at least one of polypropylene and polyethylene as a material. . As the form of the resin separator, a microporous film having a thin film shape, a pore diameter of 0.01 to 1 μm, and a thickness of 15 to 50 μm is preferably used. Further, the porosity of the resin separator is preferably 30 to 50%, more preferably 35 to 45%. Note that the resin separator of this example (a resin separator having a thickness of 15 to 50 μm) may be constituted by a single separator or may be constituted by stacking two or more separators.
（４）金属または金属化合物
　本例で用いる金属または金属化合物は、粒径が２０μm以上である。金属としては、銅、鉄、ニッケル、マンガン、クロム等である。金属化合物としては、銅、鉄、ニッケル、マンガン、クロム等の酸化物やこれらを２種以上含む化合物である。金属または金属化合物の形状は、粒状、フレーク状、球状、針状、不規則形等が挙げられる。本例では、ＳＥＭ観察した結果から解析を行ったときの粒子のアスペクト比（粒子径ａ／平均厚さｔ）が２～１００の範囲にあり、このときの粒子径ａ（粒子を平面視したときの面積Ｓの平方根）を粒径とした。ただし、球状の場合は、粒子の長径（ＤＬ）と短径（ＤＳ）との比（ＤＬ）／（ＤＳ）（球状係数あるいは真球度と言うことがある）が１.０～１.２の範囲にあり、このときの長径（ＤＬ）を粒径とした。さらに、柱状の場合は、柱の高さを粒径とした。 (4) Metal or metal compound The metal or metal compound used in this example has a particle size of 20 μm or more. Examples of the metal include copper, iron, nickel, manganese, and chromium. Examples of the metal compound include oxides such as copper, iron, nickel, manganese and chromium, and compounds containing two or more of these. Examples of the shape of the metal or metal compound include granular shapes, flake shapes, spherical shapes, needle shapes, irregular shapes, and the like. In this example, the aspect ratio (particle diameter a / average thickness t) of the particle when analyzed from the result of SEM observation is in the range of 2 to 100, and the particle diameter a at this time (the particle is viewed in plan view) The square root of the area S) was defined as the particle size. However, in the case of a spherical shape, the ratio (DL) / (DS) of the major axis (DL) and minor axis (DS) of the particle (sometimes referred to as a spherical coefficient or sphericity) is 1.0 to 1.2. The major axis (DL) at this time was defined as the particle size. Further, in the case of a columnar shape, the height of the column is defined as the particle size.
　これら金属または金属化合物は主として製造設備や製造工程から混入するものである。粒径が２０μｍ以上の金属または金属化合物は電池内に含まれないことが好ましいが、製造工程上、電池内に粒径が２０μｍ以上の金属または金属化合物が全く含まれないようにすることは困難である。ここで、金属または金属化合物の粒径の下限値は２０μｍであり、この粒径より小さい場合は、短絡の問題は発生しない。また、上限値は特に制限はないが、製造工程で混入する可能性のある金属または金属化合物は、１５０μｍ以下と想定される。 These metals or metal compounds are mainly mixed from manufacturing equipment and manufacturing processes. It is preferable that a metal or a metal compound having a particle size of 20 μm or more is not included in the battery, but it is difficult to prevent a metal or a metal compound having a particle size of 20 μm or more from being included in the battery in the manufacturing process. It is. Here, the lower limit of the particle size of the metal or metal compound is 20 μm, and if it is smaller than this particle size, the problem of short circuit does not occur. The upper limit is not particularly limited, but the metal or metal compound that may be mixed in the manufacturing process is assumed to be 150 μm or less.
（５）金属または金属化合物と樹脂セパレータとの関係
　金属または金属化合物の粒子の体積をＶ１、樹脂セパレータの１μｍ２当たりの空孔体積をＶ２としたときに、Ｖ１とＶ２とが、Ｖ１／Ｖ２＜２２５０の関係を満たすように調整されている。このような条件となるように、金属または金属化合物の粒子の体積Ｖ１、樹脂セパレータの１μｍ２当たりの空孔体積Ｖ２とを調整すると、後述のようにリチウムイオン二次電池が内部短絡を防止できることが分かった。 (5) Relationship between metal or metal compound and resin separator When the volume of metal or metal compound particles is V1, and the pore volume per 1 μm 2 of the resin separator is V2, V1 and V2 are V1 / V2. It is adjusted to satisfy the relationship <2250. By adjusting the volume V1 of the metal or metal compound particles and the pore volume V2 per 1 μm 2 of the resin separator so as to satisfy such conditions, the lithium ion secondary battery can prevent an internal short circuit as described later. I understood.
　ここで、Ｖ１は、金属又は金属化合物の粒子の質量と密度から算出し、または、金属又は金属化合物の粒子が球状の場合には｛金属又は金属化合物の粒径×（１／２）｝３×４／３πから算出することができる。Ｖ２は、樹脂セパレータの厚さと単位面積（１μｍ２）を乗じて算出される体積に樹脂セパレータの空孔率を乗じたものである。 Here, V1 is calculated from the mass and density of the metal or metal compound particles, or {the particle size of the metal or metal compound × (1/2)} 3 when the metal or metal compound particles are spherical. It can be calculated from x4 / 3π. V2 is obtained by multiplying the volume calculated by multiplying the thickness and unit area (1 μm 2 ) of the resin separator by the porosity of the resin separator.
　なお、電池の内部短絡の問題をより低減できる観点からは、Ｖ１とＶ２は、Ｖ１/Ｖ２＜２２２０の関係を満たすことが好ましい。また、実用的な観点から１５０＜Ｖ１/Ｖ２＜２２５０の関係を満たすものであってもよく、さらに好ましくは１６５＜Ｖ１/Ｖ２＜２２２０の関係を満たす。 From the viewpoint of further reducing the problem of internal short circuit of the battery, it is preferable that V1 and V2 satisfy the relationship of V1 / V2 <2220. Further, from the practical viewpoint, the relationship 150 <V1 / V2 <2250 may be satisfied, and more preferably the relationship 165 <V1 / V2 <2220 is satisfied.
　通常、樹脂セパレータは、電解液を保持、また補液するため、内部に空孔を有している。粒径２０μｍ以上の金属または金属化合物は、特に樹脂セパレータと正極板との間に存在する場合において、リチウムイオン二次電池の動作過程で酸化溶解し易くなり、酸化溶解した金属イオンが、前記樹脂セパレータの空隙を拡散、泳動し負極表面上で還元析出する。還元析出が継続すると、金属又は金属化合物は負極表面上のみならず、セパレータ空隙内にも析出する。この析出物が正極に達すると、正極と負極が微小短絡し、電池内で内部短絡が発生すると考えられる。なお、一般的に適用されている中で最も薄い膜厚が１５μm以上の樹脂セパレータでは、粒径が２０μm未満の金属又は金属化合物を含む場合は短絡しない。 Usually, the resin separator has pores inside to hold and replace the electrolyte. A metal or metal compound having a particle diameter of 20 μm or more is easily oxidized and dissolved during the operation of the lithium ion secondary battery, particularly when it is present between the resin separator and the positive electrode plate. It diffuses and migrates in the voids of the separator and is reduced and deposited on the negative electrode surface. When the reduction deposition continues, the metal or metal compound is deposited not only on the negative electrode surface but also in the separator gap. When this deposit reaches the positive electrode, it is considered that the positive electrode and the negative electrode are slightly short-circuited and an internal short circuit occurs in the battery. Note that a resin separator having a thinnest film thickness of 15 μm or more, which is generally applied, does not short-circuit when a metal or a metal compound having a particle size of less than 20 μm is included.
（６）電解液
　本例のリチウムイオン二次電池で用いる電解液は、リチウム塩と、これを溶解する非水系溶媒とから構成されており、さらに添加剤を含有しても良い。 (6) Electrolytic Solution The electrolytic solution used in the lithium ion secondary battery of this example is composed of a lithium salt and a non-aqueous solvent that dissolves the lithium salt, and may further contain an additive.
　リチウム塩としては、リチウムイオン二次電池用非水系電解液の電解質として公知のリチウム塩が用いられ、例えば次のものが挙げられる。 As the lithium salt, a known lithium salt is used as an electrolyte of a non-aqueous electrolyte for a lithium ion secondary battery, and examples thereof include the following.
　・無機リチウム塩：ＬｉＰＦ６、ＬｉＢＦ４、ＬｉＡｓＦ６、ＬｉＳｂＦ６等の無機フッ化物塩；ＬｉＣｌＯ４、ＬｉＢｒＯ４、ＬｉＩＯ４等の過ハロゲン酸塩；ＬｉＡｌＣｌ４等の無機塩化物塩等がある。 Inorganic lithium salts: inorganic fluoride salts such as LiPF 6 , LiBF 4 , LiAsF 6 , LiSbF 6 ; perhalogenates such as LiClO 4 , LiBrO 4 , LiIO 4 ; inorganic chloride salts such as LiAlCl 4 .
　・含フッ素有機リチウム塩：Ｆ３ＳＯ３等のパーフルオロアルカンスルホン酸塩；ＬｉＮ（ＣＦ３ＳＯ２）２、ＬｉＮ（ＣＦ３ＣＦ２ＳＯ２）２、ＬｉＮ（ＣＦ３ＳＯ２）（Ｃ４Ｆ９ＳＯ２）等のパーフルオロアルカンスルホニルイミド塩；ＬｉＣ（ＣＦ３ＳＯ２）３等のパーフルオロアルカンスルホニルメチド塩；Ｌｉ［ＰＦ５（ＣＦ２ＣＦ２ＣＦ３）］、Ｌｉ［ＰＦ４（ＣＦ２ＣＦ２ＣＦ３）２］、Ｌｉ［ＰＦ３（ＣＦ２ＣＦ２ＣＦ３）３］、Ｌｉ［ＰＦ５（ＣＦ２ＣＦ２ＣＦ２ＣＦ３）］、Ｌｉ［ＰＦ４（ＣＦ２ＣＦ２ＣＦ２ＣＦ３）２］、Ｌｉ［ＰＦ３（ＣＦ２ＣＦ２ＣＦ２ＣＦ３）３］等のフルオロアルキルフッ化リン酸塩等がある。 Fluorine-containing organic lithium salt: perfluoroalkane sulfonate such as F 3 SO 3 ; LiN (CF 3 SO 2 ) 2 , LiN (CF 3 CF 2 SO 2 ) 2 , LiN (CF 3 SO 2 ) (C 4 Perfluoroalkanesulfonylimide salts such as F 9 SO 2 ); perfluoroalkanesulfonylmethide salts such as LiC (CF 3 SO 2 ) 3 ; Li [PF 5 (CF 2 CF 2 CF 3 )], Li [PF 4 (CF 2 CF 2 CF 3 ) 2 ], Li [PF 3 (CF 2 CF 2 CF 3 ) 3 ], Li [PF 5 (CF 2 CF 2 CF 2 CF 3 )], Li [PF 4 (CF 2 CF 2 CF 2 CF 3 ) 2 ], Li [PF 3 (CF 2 CF 2 CF 2 CF 3 ) 3 ], and the like.
　・オキサラトボレート塩：リチウムビス（オキサラト）ボレート、リチウムジフルオロオキサラトボレート等がある。これらは、１種を単独で使用しても、２種以上を任意の組み合わせ及び比率で併用しても良い。これらの中でも、溶媒に対する溶解性、二次電池に用いた場合の充放電特性、出力特性、サイクル特性等を総合的に判断すると、ヘキサフルオロリン酸リチウム（ＬｉＰＦ６）が好ましい。 Oxalatoborate salts: lithium bis (oxalato) borate, lithium difluorooxalatoborate, etc. These may be used individually by 1 type, or may use 2 or more types together by arbitrary combinations and ratios. Among these, lithium hexafluorophosphate (LiPF 6 ) is preferable when comprehensively judging solubility in a solvent, charge / discharge characteristics when used in a secondary battery, output characteristics, cycle characteristics, and the like.
　非水系電解液中のこれらの電解質の濃度は、特に制限はないが、通常０．５ｍｏｌ／Ｌ以上、好ましくは０．６ｍｏｌ／Ｌ以上、より好ましくは０．７ｍｏｌ／Ｌ以上である。また、その上限は、通常２ｍｏｌ／Ｌ以下、好ましくは１．８ｍｏｌ／Ｌ以下、より好ましくは１．７ｍｏｌ／Ｌ以下である。濃度が低すぎると、電解液の電気伝導率が不十分の場合があり、一方、濃度が高すぎると、粘度上昇のため電気伝導度が低下する場合があり、リチウムイオン二次電池の性能が低下する場合がある。 The concentration of these electrolytes in the nonaqueous electrolytic solution is not particularly limited, but is usually 0.5 mol / L or more, preferably 0.6 mol / L or more, more preferably 0.7 mol / L or more. Moreover, the upper limit is 2 mol / L or less normally, Preferably it is 1.8 mol / L or less, More preferably, it is 1.7 mol / L or less. If the concentration is too low, the electrical conductivity of the electrolyte solution may be insufficient. On the other hand, if the concentration is too high, the electrical conductivity may decrease due to an increase in viscosity, and the performance of the lithium ion secondary battery may be reduced. May decrease.
　非水系溶媒としては、リチウムイオン二次電池用非水系電解液の電解質として公知の非水系溶媒が用いられ、例えば次のものが挙げられる。 As the non-aqueous solvent, a known non-aqueous solvent is used as an electrolyte of a non-aqueous electrolyte for a lithium ion secondary battery, and examples thereof include the following.
　・環状カーボネート：環状カーボネートを構成するアルキレン基の炭素数は２～６が好ましく、特に好ましくは２～４である。具体的には例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート等が挙げられる。中でも、エチレンカーボネート、プロピレンカーボネートが好ましい。 Cyclic carbonate: The alkylene group constituting the cyclic carbonate preferably has 2 to 6 carbon atoms, particularly preferably 2 to 4 carbon atoms. Specific examples include ethylene carbonate, propylene carbonate, butylene carbonate, and the like. Of these, ethylene carbonate and propylene carbonate are preferable.
　・鎖状カーボネート：鎖状カーボネートとしては、ジアルキルカーボネートが好ましく、構成するアルキル基の炭素数は、それぞれ、１～５ が好ましく、特に好ましくは１～４である。具体的には例えば、ジメチルカーボネート、ジエチルカーボネート、ジ－ｎ－プロピルカーボネート等の対称鎖状カーボネート類；エチルメチルカーボネート、メチル－ｎ－プロピルカーボネート、エチル－ｎ－プロピルカーボネート等の非対称鎖状カーボネート類等のジアルキルカーボネートが挙げられる。中でも、ジメチルカーボネート、ジエチルカーボネート、エチルメチルカーボネートが好ましい。 Chain carbonate: As the chain carbonate, dialkyl carbonate is preferable, and the number of carbon atoms of the alkyl group is preferably 1 to 5%, particularly preferably 1 to 4. Specifically, for example, symmetrical chain carbonates such as dimethyl carbonate, diethyl carbonate, and di-n-propyl carbonate; asymmetric chain carbonates such as ethyl methyl carbonate, methyl-n-propyl carbonate, and ethyl-n-propyl carbonate And dialkyl carbonates. Of these, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable.
　・鎖状エステル：酢酸メチル、酢酸エチル、酢酸プロピル、プロピオン酸メチル等が挙げられる。 Chain ester: methyl acetate, ethyl acetate, propyl acetate, methyl propionate, etc. are mentioned.
　・環状エーテル：テトラヒドロフラン、２－メチルテトラヒドロフラン、テトラヒドロピラン等が挙げられる。 ・ Cyclic ether: Tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran and the like.
　・鎖状エーテル：ジメトキシエタン、ジメトキシメタン等が挙げられる。 ・ Chainous ethers: Dimethoxyethane, dimethoxymethane and the like.
これらは単独で用いても、２種類以上を併用してもよいが、２種以上の化合物を併用するのが好ましい。 These may be used alone or in combination of two or more, but it is preferable to use in combination of two or more.
　前記添加材としては、リチウムイオン二次電池用非水系電解液の添加材として用いられ得ることが知られている添加材であれば特に制限はないが、例えば次のものが挙げられる。 The additive is not particularly limited as long as it is known to be used as an additive for a non-aqueous electrolyte solution for a lithium ion secondary battery, and examples thereof include the following.
　・窒素及び／ 又は硫黄を含有する複素環化合物：窒素及び／ 又は硫黄を含有する複素環化合物としては特に限定はないが、１－メチル－２－ピロリジノン、１，３－ジメチル－ ２－ピロリジノン、１，５－ジメチル－２－ピロリジノン、１－エチル－２－ピロリジノン、１－シクロヘキシル－２－ピロリジノン等のピロリジノン類；３－メチル－２－オキサゾリジノン、３－エチル－２－オキサゾリジノン、３－シクロヘキシル－２－オキサゾリジノン等のオキサゾリジノン類；１－メチル－２－ピペリドン、１－エチル－２－ピペリドン等のピペリドン類；１，３－ジメチル－２－イミダゾリジノン、１，３－ジエチル－２－イミダゾリジノン等のイミダゾリジノン類；スルホラン、２－メチルスルホラン、３－メチルスルホラン等のスルホラン類；スルホレン；エチレンサルファイト、プロピレンサルファイト等のサルファイト類；１，３－プロパンスルトン、１－メチル－１，３－プロパンスルトン、３－メチル－１，３－プロパンスルトン、１，４－ブタンスルトン、１，３－プロペンスルトン、１，４－ブテンスルトン等のスルトン類等が挙げられる。 A heterocyclic compound containing nitrogen and / or sulfur or sulfur: The heterocyclic compound containing nitrogen and / or sulfur or sulfur is not particularly limited, but includes 1-methyl-2-pyrrolidinone, 1,3-dimethyl- 2-pyrrolidinone, Pyrrolidinones such as 1,5-dimethyl-2-pyrrolidinone, 1-ethyl-2-pyrrolidinone, 1-cyclohexyl-2-pyrrolidinone; 3-methyl-2-oxazolidinone, 3-ethyl-2-oxazolidinone, 3-cyclohexyl- Oxazolidinones such as 2-oxazolidinone; piperidones such as 1-methyl-2-piperidone and 1-ethyl-2-piperidone; 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidi Imidazolidinones such as non-sulfones; sulfolane, 2-methylsulfolane, 3-methylsulfolane, etc. Sulfolanes; sulfolenes; sulfites such as ethylene sulfite and propylene sulfite; 1,3-propane sultone, 1-methyl-1,3-propane sultone, 3-methyl-1,3-propane sultone, 1,4 -Sultone such as butane sultone, 1,3-propene sultone, 1,4-butene sultone, and the like.
　・環状カルボン酸エステル：環状カルボン酸エステルとしては、特に限定はないが、γ－ブチロラクトン、γ－バレロラクトン、γ－ヘキサラクトン、γ－ヘプタラクトン、γ－オクタラクトン、γ－ノナラクトン、γ－デカラクトン、γ－ウンデカラクトン、γ－ドデカラクトン、α－メチル-γ-ブチロラクトン、α－エチル-γ-ブチロラクトン、α－プロピル-γ-ブチロラクトン、α－メチル－γ－バレロラクトン、α－エチル－γ－バレロラクトン、α,α－ジメチル-γ-ブチロラクトン、α,α-ジメチル－γ－バレロラクトン、δ－バレロラクトン、δ－ヘキサラクトン、δ－オクタラクトン、δ－ノナラクトン、δ－デカラクトン、δ－ウンデカラクトン、δ－ドデカラクトン等が挙げられる。 Cyclic carboxylic acid ester: The cyclic carboxylic acid ester is not particularly limited, but γ-butyrolactone, γ-valerolactone, γ-hexalactone, γ-heptalactone, γ-octalactone, γ-nonalactone, γ-decalactone , Γ-undecalactone, γ-dodecalactone, α-methyl-γ-butyrolactone, α-ethyl-γ-butyrolactone, α-propyl-γ-butyrolactone, α-methyl-γ-valerolactone, α-ethyl-γ -Valerolactone, α, α-dimethyl-γ-butyrolactone, α, α-dimethyl-γ-valerolactone, δ-valerolactone, δ-hexalactone, δ-octalactone, δ-nonalactone, δ-decalactone, δ- Examples include undecalactone and δ-dodecalactone.
　・フッ素含有環状カーボネート：フッ素含有環状カーボネートとしては、特に限定はないが、フルオロエチレンカーボネート、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、テトラフルオロエチレンカーボネート、トリフルオロプロピレンカーボネート等が挙げられる。 Fluorine-containing cyclic carbonate: The fluorine-containing cyclic carbonate is not particularly limited, and examples thereof include fluoroethylene carbonate, difluoroethylene carbonate, trifluoroethylene carbonate, tetrafluoroethylene carbonate, and trifluoropropylene carbonate.
　・その他分子内に不飽和結合を有する化合物：ビニレンカーボネート、ビニルエチレンカーボネート、ジビニルエチレンカーボネート、メチルビニルカーボネート、エチルビニルカーボネート、プロピルビニルカーボネート、ジビニルカーボネート、アリルメチルカーボネート、アリルエチルカーボネート、アリルプロピルカーボネート、ジアリルカーボネート、ジメタリルカーボネート等のカーボネート類； 酢酸ビニル、プロピオン酸ビニル、アクリル酸ビニル、クロトン酸ビニル、メタクリル酸ビニル、酢酸アリル、プロピオン酸アリル、アクリル酸メチル、アクリル酸エチル、アクリル酸プロピル、メタクリル酸メチル、メタクリル酸エチル、メタクリル酸プロピル等のエステル類； ジビニルスルホン、メチルビニルスルホン、エチルビニルスルホン、プロピルビニルスルホン、ジアリルスルホン、アリルメチルスルホン、アリルエチルスルホン、アリルプロピルスルホン等のスルホン類； ジビニルサルファイト、メチルビニルサルファイト、エチルビニルサルファイト、ジアリルサルファイト等のサルファイト類；ビニルメタンスルホネート、ビニルエタンスルホネート、アリルメタンスルホネート、アリルエタンスルホネート、メチルビニルスルホネート、エチルビニルスルホネート等のスルホネート類； ジビニルサルフェート、メチルビニルサルフェート、エチルビニルサルフェート、ジアリルサルフェート等のサルフェート類等が挙げられる。 Other compounds having an unsaturated bond in the molecule: vinylene carbonate, vinyl ethylene carbonate, divinyl ethylene carbonate, methyl vinyl carbonate, ethyl vinyl carbonate, propyl vinyl carbonate, divinyl carbonate, allyl methyl carbonate, allyl ethyl carbonate, allyl propyl carbonate, Carbonates such as diallyl carbonate, dimethallyl carbonate; vinyl acetate, vinyl propionate, vinyl acrylate, vinyl crotonate, vinyl methacrylate, allyl acetate, allyl propionate, methyl acrylate, ethyl acrylate, propyl acrylate, methacryl Esters such as methyl acetate, ethyl methacrylate, propyl methacrylate; divinyl sulfone, methyl vinyl sulfone, ester Sulfones such as til vinyl sulfone, propyl vinyl sulfone, diallyl sulfone, allyl methyl sulfone, allyl ethyl sulfone, and allyl propyl sulfone; Sulphites such as divinyl sulfite, methyl vinyl sulfite, ethyl vinyl sulfite, diallyl sulfite; Sulfonates such as vinyl methane sulfonate, vinyl ethane sulfonate, allyl methane sulfonate, allyl ethane sulfonate, methyl vinyl sulfonate, and ethyl vinyl sulfonate; sulfates such as divinyl sulfate, methyl vinyl sulfate, ethyl vinyl sulfate, diallyl sulfate, and the like.
　その他、上記の添加剤としては、求められる機能に応じて後述する公知の添加剤を用いても良い。例えば、過充電防止材としては、ビフェニル、アルキルビフェニル、ターフェニル、ターフェニルの部分水素化体、シクロヘキシルベンゼン、ｔ－ブチルベンゼン、ｔ－アミルベンゼン、ジフェニルエーテル、ジベンゾフラン等の芳香族化合物；２－フルオロビフェニル、ｏ－シクロヘキシルフルオロベンゼン、ｐ－シクロヘキシルフルオロベンゼン等の前記芳香族化合物の部分フッ素化物；２，４－ジフルオロアニソール、２，５－ジフルオロアニソール、２，６－ジフルオロアニソール、３，５－ジフルオロアニソール等の含フッ素アニソール化合物等が挙げられる。 In addition, as the above-mentioned additives, known additives described later may be used according to the required function. For example, as an overcharge prevention material, aromatic compounds such as biphenyl, alkylbiphenyl, terphenyl, partially hydrogenated terphenyl, cyclohexylbenzene, t-butylbenzene, t-amylbenzene, diphenyl ether, dibenzofuran, etc .; 2-fluoro Partially fluorinated products of the above aromatic compounds such as biphenyl, o-cyclohexylfluorobenzene, p-cyclohexylfluorobenzene; 2,4-difluoroanisole, 2,5-difluoroanisole, 2,6-difluoroanisole, 3,5-difluoro Examples thereof include fluorine-containing anisole compounds such as anisole.
　また、例えば負極皮膜形成材としては、無水コハク酸、無水グルタル酸、無水マレイン酸、無水シトラコン酸、無水グルタコン酸、無水イタコン酸、シクロヘキサンジカルボン酸無水物等が挙げられる。好ましくは、無水コハク酸、無水マレイン酸が挙げられる。これらは２種類以上併用して用いても良い。 For example, examples of the negative electrode film forming material include succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, cyclohexanedicarboxylic anhydride, and the like. Preferably, succinic anhydride and maleic anhydride are used. Two or more of these may be used in combination.
　また、例えば正極保護材としては、ジメチルスルホキシド、ジエチルスルホキシド、ジメチルサルファイト、ジエチルサルファイト、メタンスルホン酸メチル、ブスルファン、トルエンスルホン酸メチル、ジメチルサルフェート、ジエチルサルフェート、ジメチルスルホン、ジエチルスルホン、ジフェニルスルフィド、チオアニソール、ジフェニルジスルフィド等が挙げられる。好ましくは、メタンスルホン酸メチル、ブスルファン、ジメチルスルホンが挙げられる。これらは２種類以上併用して用いても良い。 Further, for example, as a positive electrode protective material, dimethyl sulfoxide, diethyl sulfoxide, dimethyl sulfite, diethyl sulfite, methyl methanesulfonate, busulfan, methyl toluenesulfonate, dimethyl sulfate, diethyl sulfate, dimethyl sulfone, diethyl sulfone, diphenyl sulfide, Examples include thioanisole and diphenyl disulfide. Preferably, methyl methanesulfonate, busulfan, and dimethylsulfone are used. Two or more of these may be used in combination.
　以下、本発明の効果を確認するために行った実施例について説明する。なお実施例では、上記実施の形態と同様に、積層型リチウムイオン二次電池を作成した。 Hereinafter, examples performed for confirming the effects of the present invention will be described. In the examples, a stacked lithium ion secondary battery was prepared as in the above embodiment.
［正極板の作製］
　まず、活物質であるマンガン酸リチウムを後述する所定比で混合し、次に導電材の鱗片状黒鉛（平均粒径：２０μｍ）と、結着材のポリフッ化ビニリデンとを順次混合した。混合比は、活物質：導電材：結着材＝９０：５：５とした。さらに混合物に対し、分散溶媒のＮ－メチル－２－ピロリドン（ＮＭＰ）を添加、混練したスラリーを厚さ２０μｍの集電体としてのアルミニウム箔（正極集電体）の両面に実質的に均等かつ均質に所定量塗布した。その後乾燥し、所定密度までプレスし、更に３０ｍｍ×４５ｍｍ幅に裁断して正極板を得た。 [Production of positive electrode plate]
First, lithium manganate, which is an active material, was mixed at a predetermined ratio described later, and then scale-like graphite (average particle size: 20 μm) as a conductive material and polyvinylidene fluoride as a binder were sequentially mixed. The mixing ratio was active material: conductive material: binder = 90: 5: 5. Furthermore, N-methyl-2-pyrrolidone (NMP) as a dispersion solvent was added to the mixture, and the kneaded slurry was substantially evenly and evenly formed on both surfaces of an aluminum foil (positive electrode current collector) as a current collector having a thickness of 20 μm. A predetermined amount was applied uniformly. Thereafter, it was dried, pressed to a predetermined density, and further cut to a width of 30 mm × 45 mm to obtain a positive electrode plate.
［負極板の作製］
　非晶質炭素粉末９２重量部に結着材として８重量部のポリフッ化ビニリデンを添加し、これに分散溶媒のＮＭＰを添加、混練したスラリーを厚さ１０μｍ の第２の集電体としての圧延銅箔（負極集電体）の片面に実質的に均等かつ均質に塗布した。その後乾燥し、プレスして、３１ｍｍ×４６ｍｍ幅に裁断して負極板を得た。 [Production of negative electrode plate]
8 parts by weight of polyvinylidene fluoride as a binder is added to 92 parts by weight of amorphous carbon powder, NMP as a dispersion solvent is added thereto, and the kneaded slurry is rolled as a second current collector having a thickness of 10 μm. It was applied substantially uniformly and uniformly on one side of a copper foil (negative electrode current collector). Thereafter, it was dried, pressed, and cut to a width of 31 mm × 46 mm to obtain a negative electrode plate.
 ［電池の作製］
　作製した正極板と負極板を、旭化成イーマテリアルズ製の微多孔性フィルムからなるポリエチレン製の樹脂セパレータを介して対向させて、正極板と樹脂セパレータの間に金属粒子（Ｃｕ、又はＮｉ）を１個設置し、チューブ状のラミネート袋に入れて、一端を熱溶着装置で熱溶着した。金属粒子の形状は、球状のものを用いた。なお、本例では１個の金属粒子を用いたが、実際には１個以上の金属または金属化合物が混入する可能性があると考えられる。 [Production of battery]
The prepared positive electrode plate and negative electrode plate are opposed to each other through a polyethylene resin separator made of a microporous film made by Asahi Kasei E-materials, and metal particles (Cu or Ni) are placed between the positive electrode plate and the resin separator. One was installed, put in a tube-shaped laminate bag, and one end was heat-welded with a heat-welding apparatus. The metal particles used were spherical. Although one metal particle is used in this example, it is considered that one or more metals or metal compounds may actually be mixed.
 エチレンカーボネートとジメチルカーボネートを体積比で１：２に混合した溶媒中に、電解質として６フッ化リン酸リチウムを１ｍｏｌ／Ｌ含有させた電解液１ｍＬを注液後、真空溶着装置でラミネート袋を真空引きし、袋のもう一端を熱溶着して封止して、設計容量４０ｍＡｈのリチウムイオン二次電池を作製した。 After pouring 1 mL of electrolyte containing 1 mol / L of lithium hexafluorophosphate as an electrolyte into a solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 1: 2, the laminate bag was vacuumed with a vacuum welding device. Then, the other end of the bag was thermally welded and sealed to produce a lithium ion secondary battery with a design capacity of 40 mAh.
［内部短絡の評価］
　このように作製したリチウムイオン二次電池の内部短絡の耐性を、下記に示す方法で評価した。作製したリチウムイオン二次電池について、樹脂セパレータの膜厚、金属種及び金属の粒径を変化させた電池を２５℃の環境下において充電した。充電方式として定電流定電圧方式を採用し、２０ｍＡで定電流充電後、電池電圧４．２Ｖに達した段階で定電圧充電に切り替え、合計５時間充電した。５時間後の定電圧充電時の電流値が（金属を導入していない電池と比較して）０．１ｍＡより高いものを「短絡あり」とした。 [Evaluation of internal short circuit]
The resistance of the internal short circuit of the lithium ion secondary battery thus produced was evaluated by the method shown below. About the produced lithium ion secondary battery, the battery which changed the film thickness of the resin separator, the metal seed | species, and the particle size of the metal was charged in 25 degreeC environment. A constant current and constant voltage method was adopted as a charging method. After constant current charging at 20 mA, switching to constant voltage charging was performed when the battery voltage reached 4.2 V, and charging was performed for a total of 5 hours. A battery having a current value higher than 0.1 mA (compared to a battery into which no metal was introduced) at the time of constant voltage charging after 5 hours was defined as “with short circuit”.
　金属粒子の体積（Ｖ１）及び樹脂セパレータの空孔体積（Ｖ２）は、以下のようにして算出した。 The volume of the metal particles (V1) and the pore volume of the resin separator (V2) were calculated as follows.
　金属粒子の体積（Ｖ１）＝（金属の粒径の１/２）３×４π/３
　樹脂セパレータの空孔体積（Ｖ２）＝（１μｍ２）×（樹脂セパレータの厚さ）×（セパレータの空孔率）
　なお、金属粒子の粒径は、マイクロスコープ（キーエンス製、ＶＨＸ－２０００）を用いて、倍率１０００倍の条件で測定した。 Metal particle volume (V1) = (1/2 of metal particle size) 3 × 4π / 3
Resin separator pore volume (V2) = (1 μm 2 ) × (resin separator thickness) × (separator porosity)
The particle size of the metal particles was measured using a microscope (manufactured by Keyence, VHX-2000) at a magnification of 1000 times.
　表１に示すように、セパレータの膜厚と金属種と金属の粒径を変化させ、正極板上に粒径（粒径）の異なる金属粒子（銅及びニッケル）１個を導入した電池を作製した。評価結果を表１に示す。
Figure JPOXMLDOC01-appb-T000001
 As shown in Table 1, a battery was manufactured by introducing one metal particle (copper and nickel) having a different particle size (particle size) on the positive electrode plate by changing the thickness of the separator, the metal species, and the particle size of the metal. did. The evaluation results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
　本例では、１６、３０、３６、４０μｍの４種類の樹脂セパレータを使用した。具体的には、実施例１及び比較例１～３では、厚みが１６μｍの樹脂セパレータを用いた。実施例２，３，１０，１１及び比較例４，５，８，９では、厚みが３０μｍのセパレータを用いた。実施例４～６及び比較例６では、厚みが３６μｍのセパレータを用いた。実施例７～９及び比較例７では、厚みが４０μｍのセパレータを用いた。 In this example, four types of resin separators of 16, 30, 36, and 40 μm were used. Specifically, in Example 1 and Comparative Examples 1 to 3, a resin separator having a thickness of 16 μm was used. In Examples 2, 3, 10, and 11 and Comparative Examples 4, 5, 8, and 9, a separator having a thickness of 30 μm was used. In Examples 4 to 6 and Comparative Example 6, a separator having a thickness of 36 μm was used. In Examples 7 to 9 and Comparative Example 7, a separator having a thickness of 40 μm was used.
　実施例１～１１では、樹脂セパレータの空孔率が３０～５０％の範囲にあり、これらの空孔率から得られる樹脂セパレータの空孔体積は４．１９×１０３～３．３５×１０４μｍ（１μｍ２当たりの空孔体積が６．２～１６．８μｍ3）の範囲となっている。 In Examples 1 to 11, the porosity of the resin separator is in the range of 30 to 50%, and the pore volume of the resin separator obtained from these porosity is 4.19 × 10 3 to 3.35 × 10. The range is 4 μm (the pore volume per 1 μm 2 is 6.2 to 16.8 μm 3 ).
　実施例１～９では、粒径が２０～４０μｍの球状Ｃｕ金属を用い、実施例１０及び１１では、粒径が２０～４０μｍの球状Ｎｉ金属を用いた。実施例１～１１では、金属粒子の体積は、４．１９×１０３～３．３５×１０４μｍ３の範囲に含まれている。なお粒径の範囲は、前述の金属または金属化合物の粒子の体積Ｖ１と樹脂セパレータの１μｍ２当たりの空孔体積Ｖ２との関係を満たせばよく、２０～１５０μｍの範囲の粒径において、本発明の効果が得られることが確認されている。 In Examples 1 to 9, spherical Cu metal having a particle size of 20 to 40 μm was used, and in Examples 10 and 11, spherical Ni metal having a particle size of 20 to 40 μm was used. In Examples 1 to 11, the volume of the metal particles is included in the range of 4.19 × 10 3 to 3.35 × 10 4 μm 3 . Note that the range of the particle diameter is only required to satisfy the above-described relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 per 1 μm 2 of the resin separator. It has been confirmed that the effect can be obtained.
　各実施例と各比較例から、膜厚が１５～５０μｍの樹脂セパレータで、粒径が２０μｍ以上の金属または金属化合物を含む場合に、金属又は金属化合物の体積Ｖ１とセパレータ膜厚が１５～５０μｍの樹脂セパレータの空孔体積Ｖ２がＶ１／Ｖ２＜２２５０の関係式を満たすときに、電池の内部短絡の発生を防止することができることが判った。 From each example and each comparative example, when a resin separator having a film thickness of 15 to 50 μm and containing a metal or metal compound having a particle size of 20 μm or more, the volume V1 of the metal or metal compound and the separator film thickness is 15 to 50 μm. It was found that the internal short circuit of the battery can be prevented when the void volume V2 of the resin separator satisfies the relational expression V1 / V2 <2250.
　以上、本発明の実施の形態および実施例について具体的に説明したが、本発明はこれらの実施の形態および実施例に限定されるものではなく、本発明の技術的思想に基づく変更が可能であるのは勿論である。 Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to these embodiments and examples, and modifications based on the technical idea of the present invention are possible. Of course there is.
　本発明によれば、金属または金属化合物の粒子の体積Ｖ１と樹脂セパレータの１μｍ２当たりの空孔体積Ｖ２との関係がＶ１／Ｖ２＜２２５０の関係を満たすように、金属または金属化合物の粒子の体積Ｖ１に対して樹脂セパレータの１μｍ２当たりの空孔体積Ｖ２が調整されているため、還元析出した金属または金属化合物のデンドライトが、負極板の表面からセパレータ内に留まり、セパレータを貫通して正極板まで達するのを防ぐことができる。その結果、デンドライトによる正極と負極の短絡が防止され、電池の内部短絡を防ぐことができる。したがって、本発明によれば、安全性の高いリチウムイオン二次電池を提供することができる。 According to the present invention, the metal or metal compound particle volume V1 and the pore volume V2 per 1 μm 2 of the resin separator satisfy the relationship of V1 / V2 <2250. Since the pore volume V2 per 1 μm 2 of the resin separator is adjusted with respect to the volume V1, the dendrite of the reduced metal or metal compound stays in the separator from the surface of the negative electrode plate, penetrates the separator and passes through the positive electrode It can prevent reaching the board. As a result, a short circuit between the positive electrode and the negative electrode due to dendrites is prevented, and an internal short circuit of the battery can be prevented. Therefore, according to the present invention, a highly safe lithium ion secondary battery can be provided.

Claims (11)

  1. 　厚みが１５～５０μｍの樹脂セパレータと、前記樹脂セパレータを介して積層された正極板及び負極板とを有する極板群を備え、前記樹脂セパレータと前記正極板または負極板との間に粒径が２０μｍ以上の金属または金属化合物の粒子が存在するリチウムイオン二次電池であって、
    　前記金属または金属化合物の粒子の体積Ｖ１と前記樹脂セパレータの１μｍ２当たりの空孔体積Ｖ２との関係が、下記式（１）の関係を満たすリチウムイオン二次電池。
    　　Ｖ１／Ｖ２＜２２５０　…（１）     And an electrode plate group having a resin separator having a thickness of 15 to 50 μm and a positive electrode plate and a negative electrode plate laminated via the resin separator, and a particle size is between the resin separator and the positive electrode plate or the negative electrode plate. A lithium ion secondary battery in which particles of a metal or metal compound of 20 μm or more exist,
    The lithium ion secondary battery in which the relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 per 1 μm 2 of the resin separator satisfies the relationship of the following formula (1).
    V1 / V2 <2250 (1)
  2. 　厚みが１５～５０μｍの樹脂セパレータと、前記樹脂セパレータを介して積層された正極板及び負極板とを有する極板群を備え、前記樹脂セパレータと前記正極板または負極板との間に粒径が２０μｍ以上の金属または金属化合物の粒子が存在するリチウムイオン二次電池であって、
    　前記金属または金属化合物の粒子の体積Ｖ１と前記樹脂セパレータの１μｍ２当たりの空孔体積Ｖ２との関係が、下記（２）式の関係を満たすリチウムイオン二次電池。
    　　１５０＜Ｖ１／Ｖ２＜２２５０　…（２）     And an electrode plate group having a resin separator having a thickness of 15 to 50 μm and a positive electrode plate and a negative electrode plate laminated via the resin separator, and a particle size is between the resin separator and the positive electrode plate or the negative electrode plate. A lithium ion secondary battery in which particles of a metal or metal compound of 20 μm or more exist,
    The lithium ion secondary battery in which the relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 per 1 μm 2 of the resin separator satisfies the relationship of the following formula (2).
    150 <V1 / V2 <2250 (2)
  3. 　厚みが１５～５０μｍの樹脂セパレータと、前記樹脂セパレータを介して積層された正極板及び負極板とを有する極板群を備え、前記樹脂セパレータと前記正極板または負極板との間に粒径が２０μｍ以上の金属または金属化合物の粒子が存在するリチウムイオン二次電池であって、
    　前記金属または金属化合物の粒子の体積Ｖ１と前記樹脂セパレータの１μｍ２当たりの空孔体積Ｖ２との関係が、下記（３）式の関係を満たすリチウムイオン二次電池。
    　　１６５＜Ｖ１／Ｖ２＜２２２０　…（３）     And an electrode plate group having a resin separator having a thickness of 15 to 50 μm and a positive electrode plate and a negative electrode plate laminated via the resin separator, and a particle size is between the resin separator and the positive electrode plate or the negative electrode plate. A lithium ion secondary battery in which particles of a metal or metal compound of 20 μm or more exist,
    The lithium ion secondary battery in which the relationship between the volume V1 of the metal or metal compound particles and the pore volume V2 per 1 μm 2 of the resin separator satisfies the relationship of the following formula (3).
    165 <V1 / V2 <2220 (3)
  4. 　前記樹脂セパレータの空孔率が、３０～５０％である請求項１乃至３のいずれか１項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 a porosity of the resin separator is 30 to 50%.
  5. 　前記樹脂セパレータはポリプロピレン及びポリエチレンの少なくとも一つを材質として含む請求項１乃至３のいずれか１項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 resin separator includes at least one of polypropylene and polyethylene as a material.
  6. 　前記金属または金属化合物の粒子が、前記樹脂セパレータと前記正極板との間に存在する請求項１乃至３のいずれか１項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 particles of the metal or metal compound are present between the resin separator and the positive electrode plate.
  7. 　前記金属または金属化合物の粒子の前記粒径が、２０～１５０μｍである請求項１乃至３のいずれか１項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 particle diameter of the metal or metal compound particles is 20 to 150 µm.
  8. 　前記金属または金属化合物の粒子の前記体積Ｖ１が、４．１９×１０３～１．７７×１０６μｍ３である請求項１乃至３のいずれか１項に記載のリチウムイオン二次電池。 4. The lithium ion secondary battery according to claim 1, wherein the volume V1 of the metal or metal compound particles is 4.19 × 10 3 to 1.77 × 10 6 μm 3 .
  9. 　前記金属が、銅、鉄、ニッケル、マンガン、及びクロムのうち少なくとも１種の金属である請求項１乃至３のいずれか１項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 metal is at least one metal selected from copper, iron, nickel, manganese, and chromium.
  10. 　前記金属化合物が、銅、鉄、ニッケル、マンガン、及びクロムのうち少なくとも１種の金属の酸化物である請求項１乃至３のいずれか１項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 metal compound is an oxide of at least one metal selected from copper, iron, nickel, manganese, and chromium.
  11. 　前記金属が、銅またはニッケルである請求項１乃至３のいずれか１項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 metal is copper or nickel.
PCT/JP2014/057555 2013-03-29 2014-03-19 Lithium ion secondary battery WO2014156891A1 (en)

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