JP6187071B2 - Nonaqueous electrolyte secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte secondary battery having a stacked group in which a positive electrode plate and a negative electrode plate are stacked via a separator.

  In recent years, due to an increase in power consumption accompanying the development of electronic devices, there has been a demand for higher output and higher capacity of batteries. Further, a long life is required for in-vehicle applications and industrial applications. In general, a non-aqueous electrolyte secondary battery has a structure in which a plurality of positive and negative electrode plates are alternately stacked in a battery can via separators to prevent short circuit (stacked type), and a positive electrode plate and a shaft. A structure (cylindrical type) wound through a negative electrode plate and a separator is known.

  In the laminated nonaqueous electrolyte secondary battery, tabs for connecting the electrode plate and the terminal are formed on one end of each of the positive electrode plate and the negative electrode plate. The battery can lid plate is provided with a positive electrode terminal and a negative electrode terminal, and the positive electrode terminal and the negative electrode terminal arranged on the battery can lid are joined to the tab of the positive electrode plate and the tab of the negative electrode plate, respectively.

  However, as the capacity of the laminated nonaqueous electrolyte secondary battery used for power storage and the like is increased, the number of electrode plates accommodated in the battery can increases. Therefore, as the number of electrode plates increases, the electrode plate located near the center of the electrode plate group is more susceptible to the heat generated by the battery reaction than the electrode plate located near the end, and the charge / discharge cycle is repeated. Deterioration such as a decrease in battery capacity occurs. The uneven deterioration of the electrode is one cause of shortening the battery life.

  There are various proposals as means for improving deterioration associated with charge / discharge cycles. For example, the electrode plate positioned at at least one end of the electrode plate group has a thickness of 2% to 25% thick (see Patent Document 1), and the positive electrode plate and the negative electrode plate are wound in a spiral shape via a separator. In a rotated battery, a technique (see Patent Document 2) is disclosed in which the mixture filling density of the negative electrode plate at the outermost peripheral portion is made lower than that of the negative electrode plates at other inner peripheral portions for one or more rounds.

JP-A-10-79245 JP 2000-195556 A

  However, in Patent Document 1, output characteristics deteriorate due to the complexity of the work process and uneven surface pressure applied to the electrode plate. Moreover, in patent document 2, only the part which made the mixture density low, the contact area of electrolyte solution and an active material becomes large, deterioration by a side reaction etc. advances, and adhesiveness with an electrode falls, Capacity is expected to decline.

  An object of the present invention is to provide a battery having a long life by leveling the distribution of heat generated by a battery reaction without impairing output characteristics.

  The present invention relates to a non-aqueous electrolyte secondary battery having a plurality of stacked groups in which a positive electrode plate and a negative electrode plate are stacked via a separator, and the positive and negative electrode plate mixture layer thickness of at least one stacked group, It is characterized by making it thinner than the thickness of the positive and negative electrode mixture layer of the laminated group. Specifically, for example, the mixture thickness of the positive and negative electrode plates positioned near the center of the stack group is made thinner than the mixture thickness of the positive and negative electrode plates positioned near the end side of the stack group.

  More specifically, the thickness of the positive and negative electrode mixture layer included in one or more stack groups located near the center in the direction in which the plurality of stack groups are arranged is the outermost stack group in the direction in which the plurality of stack groups are arranged. It is thinner than the positive and negative electrode plate mixture layer thickness. As a result, the number of positive plates and negative plates included in one or more stack groups located near the center in the direction in which the plurality of stack groups are arranged is greater than the number of positive plates and negative plates included in the outermost stack group. There are also many.

  As a result, the distribution of heat generated by the battery reaction is leveled, the uneven deterioration of the electrode plate is suppressed, and the life can be extended. In addition, the distance between the positive electrode plate and the negative electrode plate is reduced, and the number of electrode plates is increased to increase the facing area and to increase the output without impairing the capacity. Provide batteries.

  As is clear from the above description, according to the nonaqueous electrolyte secondary battery of the present invention, the positive and negative electrode mixture layer thicknesses of one or more stacked groups of the electrode plate group are set to be larger than the mixture thicknesses of the other stacked groups. By reducing the thickness and increasing the number of electrode plates, local deterioration due to a temperature distribution difference during discharge can be suppressed without impairing the discharge capacity, and a longer life and higher output can be achieved.

1 is a partially broken front view of a lithium ion secondary battery 1 as a nonaqueous electrolyte secondary battery to which an embodiment of the present invention is applied. It is a perspective view of the state which removed the battery can 7 of the lithium ion secondary battery 1 as a nonaqueous electrolyte secondary battery to which embodiment of this invention is applied. It is a right view of the electrode group 3 of the lithium ion secondary battery 1 as a nonaqueous electrolyte secondary battery to which embodiment of this invention is applied.

  Hereinafter, embodiments of the present invention will be described in detail. In order to describe the configuration of the embodiment, a positive electrode plate, a negative electrode plate, a separator, and an electrolytic solution that can be used in the embodiment will be described.

(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 plate. 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 plate, or these The material is dissolved and dispersed in a liquid medium, applied as a slurry to the positive electrode current collector plate, and dried to form a positive electrode active material layer on the positive electrode current collector plate.

  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.

  A known conductive material can be arbitrarily used as the positive electrode conductive material. 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 in manufacturing the electrode 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), rubbery polymers such as fluorine rubber, isoprene rubber, butadiene rubber, ethylene-propylene rubber; styrene / butadiene / styrene block copolymer or hydrogenated product thereof, EPDM (ethylene / propylene / diene terpolymer) ), Thermoplastic elastomeric polymers such as styrene / ethylene / butadiene / ethylene copolymer, styrene / isoprene / styrene block copolymer, or hydrogenated products thereof; syndiotactic-1, 2-polybutadiene , Polyvinyl acetate, ethylene / vinyl acetate copolymer, soft resinous polymer such as propylene / α-olefin copolymer; polyvinylidene fluoride (PVdF), polytetrafluoroethylene, fluorinated polyvinylidene fluoride, polytetrafluoro Fluorine polymers such as ethylene / ethylene copolymer, 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. 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.

  There is no restriction | limiting in particular as a material of a positive electrode current collecting plate, A well-known thing can be used arbitrarily. Specific examples include metal materials such as aluminum, stainless steel, nickel plating, titanium, and tantalum; and carbonaceous materials such as carbon cloth and carbon paper. Of these, metal materials, particularly aluminum, are preferred.

  The form of the positive electrode current collector plate is not particularly limited, and a known form can be arbitrarily used. Specific examples of the metal material include metal foil, 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, etc. are mentioned. Of these, metal foil is preferred. The metal foil may be appropriately formed in a mesh shape. The thickness of the metal foil 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 metal foil is thinner than this range, the strength required for the current collector may be insufficient. Conversely, if the metal foil is thicker than this range, the handleability may be impaired.

(2) Negative electrode plate As for the negative electrode plate, the negative electrode mixture containing the negative electrode active material which can electrochemically occlude / release lithium ion is apply | coated to both surfaces of the negative electrode current collecting plate. Negative electrode active materials include carbonaceous materials, tin oxide, lithium titanate, silicon oxide and other metal oxides, metal composite oxides, lithium alloys such as lithium alone and lithium aluminum alloys, and alloys with lithium such as tin and silicon Possible metals and the like. 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 for high current density charge / discharge characteristics. It is preferable from the viewpoint.

  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 13 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.

  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.

  As a negative electrode current collecting plate, a well-known thing can be used arbitrarily. Examples of the current collector plate for the negative electrode include metal materials such as copper, nickel, stainless steel, and nickel-plated steel. Among these, copper is preferable from the viewpoint of ease of processing and cost. Examples of the shape of the negative electrode current collector plate include a metal foil, a metal plate, a metal thin film, an expanded metal, a punching metal, and a foam metal when the current collector is a metal material. Among these, a metal foil 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 plate. 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.

  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) Separator The separator has a predetermined mechanical strength that electrically insulates the electrodes from each other, has a large ion permeability, and has resistance to oxidation on the side in contact with the positive electrode plate and reduction on the negative electrode side. Resin which combines 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%, and more preferably 35 to 45%. Note that the resin separator of this example (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) 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.

  As a lithium salt, a well-known lithium salt is used as an electrolyte of the non-aqueous electrolyte solution for lithium ion secondary batteries, for example, the following are mentioned.

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 ₂ CF ₃ ) ₂ ], Li [PF ₃ (CF ₂ CF ₂ CF ₂ CF ₃ ) ₃ ], and the like.

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.

  As the non-aqueous solvent, a known non-aqueous solvent is used as an electrolyte of a non-aqueous electrolyte solution 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 a chain carbonate, dialkyl carbonate is preferable, and carbon number of the alkyl group which comprises is respectively preferable 1-5, Most preferably, it is 1-4. 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, etc. are mentioned.

  -Chain ether: Dimethoxyethane, dimethoxymethane, etc. are mentioned.

These may be used alone or in combination of two or more, but it is preferable to use in combination of two or more.

  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.

  -Heterocyclic compound containing nitrogen and / or sulfur: The heterocyclic compound containing nitrogen and / or sulfur is not particularly limited, but 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 Non-imidazolidinones such as sulfone; sulfolane, 2-methylsulfolane, 3-methylsulfolane, etc. Phoranes; 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: The cyclic carboxylic acid ester is not particularly limited, but γ-butyrolactone, γ-valerolactone, γ-hexalactone, γ-heptalactone, γ-octalactone, γ-nonalactone, and 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.

  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.

  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 and 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 acid, ethyl methacrylate, propyl methacrylate; divinyl sulfone, methyl vinyl sulfone, ethyl Sulfones such as vinyl sulfone, propyl vinyl sulfone, diallyl sulfone, allyl methyl sulfone, allyl ethyl sulfone, and allyl propyl sulfone; sulfites such as divinyl sulfite, methyl vinyl sulfite, ethyl vinyl sulfite, and diallyl sulfite; vinyl Methane sulfonate, vinyl ethane sulfonate, allyl methane sulfonate, allyl ethane sulfonate, methyl vinyl sulfonate, ethyl vinyl sulfonate, and other sulfonates; divinyl sulfate, methyl vinyl sulfate, ethyl vinyl sulfate, diallyl sulfate, and the like.

  In addition, as said additive, you may use the well-known additive mentioned later according to the function calculated | required. For example, as an overcharge preventing 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.

  Examples of the negative electrode film forming material include succinic anhydride, glutaric anhydride, maleic anhydride, citraconic anhydride, glutaconic anhydride, itaconic anhydride, and cyclohexanedicarboxylic anhydride. Preferably, succinic anhydride and maleic anhydride are used. Two or more of these may be used in combination.

  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.

[Battery structure]
Hereinafter, a non-aqueous electrolyte secondary battery current collecting structure and a configuration of a secondary battery according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partially broken front view of a lithium ion secondary battery 1 as a nonaqueous electrolyte secondary battery to which the present invention is applied. In the present embodiment, in order to facilitate understanding, the thickness dimensions of some components are exaggerated and the number of electrode plates is smaller than the actual number.

  As shown in FIG. 1, the lithium ion secondary battery 1 of the present embodiment includes an electrode plate group 3 and a stainless-made square battery case 5 that houses the electrode plate group 3 therein. The battery container 5 includes a battery can 7 having one end opened, and a battery lid 9. After the electrode plate group 3 is inserted into the battery can 7, the opening peripheral edge of the battery can 7, and the battery lid It is sealed by welding the peripheral part of 9.

  A positive electrode terminal 11 made of aluminum and a negative electrode terminal 13 made of copper are fixed to the battery lid 9. The positive electrode terminal 11 and the negative electrode terminal 13 are screwed terminal portions 11a and 13a that pass through the cover plate of the battery lid 9 and project outside the battery container 5, and a positive current collector (not shown) disposed in the battery container. And a negative electrode current collector. A positive terminal nut 21 and a negative terminal nut 23 are screwed onto the screwed terminal portions 11a and 13a. An annular inner packing 15 is provided between the positive electrode terminal 11 and the negative electrode terminal 13 and the battery lid 9. An annular outer packing 17 and a terminal washer 19 are provided on the outer side of the battery lid 9 so as to be opposed to the inner packing 15 via the battery lid 9. The positive electrode terminal 11 and the negative electrode terminal 13 are respectively attached to the battery lid 9 by a positive terminal nut 21 and a negative terminal nut 23 provided at the tip of the threaded portion via the inner packing 15, the outer packing 17, and the terminal washer 19. It is fixed. The portion of the battery lid 9 where the positive electrode terminal 11 and the negative electrode terminal 13 are provided ensures a sealed / sealed state in the battery container 5 by the inner packing 15 and the outer packing 17.

  The battery lid 9 is provided with a gas discharge valve 9a and a liquid injection port 9b welded with stainless steel foil. The gas discharge valve 9a has a function of cleaving the stainless steel foil and releasing the internal gas when the battery internal pressure increases. A non-aqueous electrolyte (not shown) is injected from the liquid injection port 9b.

  A positive electrode tab 35 a is formed at one end of the positive electrode current collector plate of the positive electrode plate 35. A negative electrode tab 37 a is formed at one end of the negative electrode current collector plate of the negative electrode plate 37. A plurality of positive electrode tabs 35a of a plurality of positive electrode plates 25 are stacked to form a positive electrode current collecting tab layer 27, and a plurality of negative electrode current collecting tabs 37a of a plurality of negative electrode plates 37 are stacked to be negative electrode current collecting tabs. A layer 33 is formed. The separator 39 has a size that can prevent the positive electrode plate 35 and the negative electrode plate 37 from contacting each other in a stacked state.

  The positive electrode current collector of the positive electrode terminal 11 is agitated by being pressed against the positive electrode side holding plate 25 while rotating the stirring bonding tool with the positive electrode current collecting tab layer 27 sandwiched between the positive electrode side holding plate 25 and the positive electrode side holding plate 25. By forming the joint portion 29, the positive electrode current collecting tab layer 27 is attached to the positive electrode current collector. Further, the negative electrode current collector of the negative electrode terminal 13 is pressed against the negative electrode side holding plate 31 while rotating the stirring bonding tool with the negative electrode current collecting tab layer 33 sandwiched between the negative electrode side holding plate 31 and the negative electrode side holding plate 31. Thus, the negative electrode current collector tab layer 33 is attached to the negative electrode current collector.

  FIG. 2 is a perspective view of the lithium ion secondary battery 1 with the battery can 7 removed, and FIG. 3 is a right side view of the electrode plate group 3. In FIGS. 2 and 3, each component is schematically shown for easy understanding. Therefore, each component shown in FIGS. 2 and 3 is different in shape, size, and the like from the actual component of the electrode plate group. In the present embodiment, the electrode plate group 3 includes a plurality of stacked groups 3a, 3b, 3c, and 3d. The stacked groups 3a, 3b, 3c, and 3d are configured by stacking a positive electrode plate 35, a separator 39, and a negative electrode plate 37, respectively. FIG. 2 shows an embodiment in which there are four stack groups. In the present embodiment, the number of stacked groups is preferably 2-8, and more preferably 3-6. Further, the number of positive electrode plates and the number of negative electrode plates included in the electrode plate group 3 are each preferably in the range of 150 to 300, and more preferably in the range of 180 to 250. The number of positive electrode plates and the number of negative electrode plates included in one stacked group are each preferably 20 to 80, more preferably 30 to 70, and still more preferably 40 to 60.

  In this embodiment, the thickness of the positive electrode mixture of the positive electrode active material layer formed on one positive electrode plate and the thickness of the negative electrode mixture of the negative electrode active material layer formed on one negative electrode plate (excluding the current collector) ) Is preferably 100 μm to 300 μm, more preferably 120 to 250 μm, and still more preferably 140 to 200 μm.

  In the present specification, the positive and negative electrode plate mixture layer thickness means the total thickness of the positive electrode active material layer of one set of positive electrode plates and the negative electrode active material layer of the negative electrode plate, and the positive and negative electrode plate mixture layer thickness is thin. Means that the coating amount of the positive electrode mixture to the positive electrode plate and the negative electrode mixture (positive and negative electrode mixture) to the negative electrode plate is small (the thickness of the current collector is not included). That is, the mixture density of each of the positive electrode plate and the negative electrode plate is the same, which is different from changing the thickness by changing the density. In addition, the number of electrode plates is increased simultaneously with reducing the thickness. For this reason, the total amount of substances involved in the battery reaction does not change and the reaction area increases, so that a long life and high output can be achieved without impairing the battery capacity.

  When the number of laminated groups 3a, 3b, 3c, and 3d constituting the electrode plate group 3 is 4 as shown in FIG. 2, the thickness of at least one positive and negative electrode mixture layer of the laminated group 3b and the laminated group 3c is laminated. By making it thinner than the positive and negative electrode mixture layers of the group 3a and the laminated group 3d and increasing the number of electrode plates, the heat distribution during charge and discharge is leveled and the distance between the positive and negative electrode plates is reduced. And, by extending the facing area, it tends to have a long life and high output. Here, the positive and negative electrode plate mixture layers of the outermost laminated groups 3a and 3d have positive and negative electrode plate mixture layers of the inner laminated groups 3b and 3c (sandwiched between the outermost laminated groups 3a and 3d). More preferably, it is thicker than the thickness. That is, it is preferable that the number of electrode plates included in the outermost stacked groups 3a and 3d is smaller than the number of electrode plates included in the inner stacked groups 3b and 3c.

  The difference between the positive and negative electrode mixture layer thickness of the electrode plates used for the outermost laminated groups 3a and 3d and the positive and negative electrode plate mixture layer thickness of the electrode plates used for the inner laminated groups 3b and 3c is 5 to 30 μm. It is preferable that it is 6 to 25 μm.

  In FIG. 3, for the sake of simplicity, the positive and negative plates and separators of the stacked groups 3a, 3b, 3c, and 3d are omitted, but the present embodiment assumes a capacity of about 70 to 120 Ah. In the lithium ion secondary battery 1 of this form, the electrode plate group 3 is actually configured by stacking several hundred positive electrode plates, several hundred negative electrode plates, and several hundred separators.

  In a non-aqueous electrolyte secondary battery using a lithium-containing composite oxide for the positive electrode and a carbonaceous material for the negative electrode, a greater effect can be obtained when the number of electrode plates is 200 or more. However, the positive electrode plate and the negative electrode plate are connected via a separator. A non-aqueous electrolyte secondary battery having a laminated group laminated in a similar manner exhibits the same effect.

  The positive electrode current collecting tab layer 27 in which the positive electrode tabs 35a are bundled is used when the method of electrically connecting the positive electrode current collector to the positive electrode current collector of the positive electrode terminal 11 through an independent connecting current collector plate is used. One end of the layer 27 may be joined to one end of the connecting current collector plate using ultrasonic welding, laser welding, or the like, and the connecting current collector plate may be connected to the positive electrode current collector.

  Hereinafter, specific examples according to embodiments of the present invention will be described with reference to the drawings.

  As a battery manufactured for use in this example, a battery prepared in the same manner as the battery described in the embodiment for carrying out the present invention was used.

[Positive electrode plate]
The positive electrode plate was prepared using an aluminum foil as a current collector, lithium manganate as a positive electrode active material, polyvinylidene fluoride (hereinafter referred to as PVDF) as a binder, and acetylene black as a conductive material.

[Negative electrode plate]
For the negative electrode plate, copper foil was used as the current collector, graphite as the negative electrode active material, and PVDF as the binder.

[Separator]
A polyethylene porous material was used for the separator.

[Electrolyte]
As the electrolytic solution, LiBF4 was used as a lithium salt, a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) was used as a non-aqueous solvent, and vinylene carbonate (VC) was used as an additive.

Example 1
Four stacked groups were prepared using 204 positive plates and 208 negative plates. The laminated groups 3a and 3d have 50 positive plates and 51 negative plates, and the thickness of the mixture layer of one set of positive and negative plates is 170 μm. The laminated groups 3b and 3c are 52 positive electrode plates and 53 negative electrode plates, and the mixture layer thickness of one set of positive and negative electrode plates is 163 μm. A battery 1 having these laminated groups was produced and used as a test battery of Example 1.

(Example 2)
Four groups were prepared using 208 positive electrode plates and 212 negative electrode plates. The laminated groups 3a and 3d have 50 positive plates and 51 negative plates, and the thickness of the mixture layer of one set of positive and negative plates is 170 μm. The laminated groups 3b and 3c have 54 positive plates and 55 negative plates, and the mixture layer thickness of one set of positive and negative plates is 157 μm. A battery 1 having these laminated groups was produced and used as a test battery of Example 2.

(Example 3)
Four groups were prepared using 216 positive plates and 220 negative plates. The laminated groups 3a and 3d have 50 positive plates and 51 negative plates, and the thickness of the mixture layer of one set of positive and negative plates is 170 μm. The laminated groups 3b and 3c are 58 positive plates and 59 negative plates, and the thickness of the mixture layer of one set of positive and negative plates is 146 μm. A battery 1 having these laminated groups was produced and used as a test battery of Example 3.

(Comparative Example 1)
Four groups were prepared using 200 positive plates and 204 negative plates. Each of the laminated groups 3a, 3b, 3c, and 3d has 50 positive plates and 51 negative plates, and the mixture layer thickness of one set of positive and negative plates is 170 μm. A battery 1 having these stacked groups was produced and used as a test battery of Comparative Example 1.

Hereafter, it will list about the element which compared about the Example and comparative example of this invention.

The results of charging and discharging these batteries are summarized in Table 3. Charging was performed at a constant voltage of 4.1V and a maximum current of 50A. Discharging was performed at 500 A until the voltage reached 3V. The discharge capacity retention rate was the ratio of the discharge capacity at the 100th cycle to the initial discharge capacity. These results are average values of two batteries.

  It can be seen that the thinner the thickness of the stacked groups 3b and 3c located on the center side of the stacked body, the smaller the difference between the highest electrode temperature and the lowest temperature, and the higher the discharge capacity retention rate.

  In addition, although the four laminated groups were produced in the said Example and comparative example, as long as the above-mentioned laminated group is arranged, how many groups may be produced.

  Moreover, in the said embodiment, although the lithium ion battery was demonstrated, of course, this invention is applicable to another nonaqueous electrolyte secondary battery.

DESCRIPTION OF SYMBOLS 1 Lithium ion secondary battery 3 Electrode group 3a Lamination group 3b Lamination group 3c Lamination group 3d Lamination group 5 Battery container 7 Battery can 9 Battery lid 9a Gas exhaust valve 9b Injection port 11 Positive electrode terminal 11a Terminal part 13 Negative electrode terminal 13a Terminal Part 15 Inner packing 17 Outer packing 19 Terminal washer 21 Positive terminal nut 23 Negative terminal nut 25 Positive side holding plate 27 Positive current collecting tab layer 29 Stirred joint 31 Negative electrode side holding plate 33 Negative current collecting tab layer 35 Positive electrode plate 35a Positive electrode current collecting tab 37 Negative electrode plate 37a Negative electrode current collecting tab 39 Separator

Claims (2)

In a non-aqueous electrolyte secondary battery having a plurality of stacked groups in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween, the positive and negative electrode plate mixture layer thickness of at least one of the stacked groups is equal to the other stacked layers. a thin yet non-aqueous electrolyte secondary battery than the positive and negative electrode plates mixture layer thickness of the group,
The positive and negative electrode plate mixture layer thickness included in one or more of the stacked groups located near the center in the direction in which the plurality of stacked groups are arranged is included in the outermost stacked group in the direction in which the plurality of stacked groups are arranged. Thinner than the positive and negative electrode plate mixture layer thickness,
The number of positive and negative electrode plates included in the one or more stacked groups located near the center in the direction in which the plurality of stacked groups are arranged is greater than the number of positive and negative electrode plates included in the outermost stacked group. A non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery according to claim 1, wherein the lithium-containing composite oxide is a positive electrode active material, and the carbonaceous material is a negative electrode active material.