WO2025004811A1 - 二次電池 - Google Patents

二次電池 Download PDF

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Publication number
WO2025004811A1
WO2025004811A1 PCT/JP2024/021398 JP2024021398W WO2025004811A1 WO 2025004811 A1 WO2025004811 A1 WO 2025004811A1 JP 2024021398 W JP2024021398 W JP 2024021398W WO 2025004811 A1 WO2025004811 A1 WO 2025004811A1
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WIPO (PCT)
Prior art keywords
positive electrode
current collector
secondary battery
collector
resin
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PCT/JP2024/021398
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English (en)
French (fr)
Japanese (ja)
Inventor
拓馬 岸
孝紀 大前
格久 山本
洋一郎 宇賀
毅 千葉
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Panasonic Intellectual Property Management Co Ltd
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Panasonic Intellectual Property Management Co Ltd
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Priority to JP2025529624A priority Critical patent/JPWO2025004811A1/ja
Publication of WO2025004811A1 publication Critical patent/WO2025004811A1/ja
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    • 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

  • This disclosure relates to secondary batteries.
  • Patent Document 1 proposes "a method for manufacturing an electrode plate for a storage battery device, in which a mixture layer is formed on a strip-shaped current collector by discharging a mixture slurry from a discharge nozzle corresponding to each of a plurality of discharge regions extending along the length of the current collector, the positions of the discharge regions are set so that a portion of each of the plurality of discharge regions forms an overlapping portion that overlaps a portion of the adjacent discharge region when viewed in the length direction of the current collector, the overlapping portion has a length in the width direction of the current collector of 8 mm or less, and an uncoated portion is provided in at least one of the discharge regions by intermittently discharging the mixture slurry.”
  • Patent Document 2 proposes an "electrode plate for an electricity storage device, comprising a substantially rectangular current collector and an active material layer provided on at least one surface of the current collector, the current collector having a plain portion at one end in the width direction in a portion of the longitudinal direction to which an electrode lead is connected, and in the region in which the active material layer is provided, the elastic modulus of a first region adjacent to the plain portion in the width direction is greater than the elastic modulus of a second region adjacent to the region occupied by the plain portion and the first region in the longitudinal direction.”
  • One aspect of the present disclosure relates to a secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, the positive electrode and the negative electrode being wound with the separator interposed therebetween, the positive electrode comprising a strip-shaped positive electrode collector and a positive electrode composite layer disposed on the positive electrode collector, the positive electrode having a positive electrode edge portion including one end in the short side direction of the positive electrode and a positive electrode main portion other than the positive electrode edge portion, the positive electrode edge portion having an exposed portion of the positive electrode collector partially provided at one or more locations along the long side direction of the positive electrode collector, the exposed portion not having the positive electrode composite layer from the one end in the short side direction to the positive electrode main portion, the positive electrode composite layer including a positive electrode active material and a binder, the binder including a first resin having a first molecular weight M1 and a second resin having a second molecular weight M2, and satisfying M1>M2.
  • FIG. 1 is a schematic cross-sectional view of a secondary battery according to an embodiment
  • FIG. 2 is a schematic plan view of a positive electrode according to an embodiment.
  • Secondary batteries include non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries, lithium metal secondary batteries, and solid-state batteries containing a gel electrolyte or a solid electrolyte.
  • the secondary battery may be a liquid secondary battery containing an electrolytic solution as an electrolyte, or an all-solid-state secondary battery containing a solid electrolyte.
  • the secondary battery according to the present disclosure comprises a strip-shaped positive electrode, a strip-shaped negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode.
  • the positive electrode and the negative electrode are wound (wound) with the separator interposed therebetween.
  • the secondary battery comprises a wound electrode group.
  • the outer shape of the wound electrode group is columnar, and may be, for example, cylindrical.
  • the positive electrode comprises a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector.
  • the positive electrode mixture layer may be in the form of a film.
  • the positive electrode has a positive electrode current collector and a positive electrode mixture layer formed (or supported) on a partial region of the surface of the positive electrode current collector.
  • the positive electrode has a positive electrode edge portion including one end in the short side direction of the positive electrode and a positive electrode main portion other than the positive electrode edge portion.
  • the positive electrode edge portion has an exposed portion of the positive electrode current collector that is partially provided at one or more locations along the longitudinal direction of the positive electrode current collector.
  • the exposed portion of the positive electrode current collector does not have a positive electrode mixture layer from one end in the short side direction to the positive electrode main portion.
  • the exposed portion of the positive electrode current collector may be provided at multiple locations intermittently along the longitudinal direction of the positive electrode current collector.
  • the positive electrode mixture layer is composed of a positive electrode mixture. Since the positive electrode mixture contains a positive electrode active material as an essential component, the positive electrode mixture layer may also be called a positive electrode active material layer. The positive electrode mixture layer is supported on one or both surfaces of the positive electrode current collector.
  • the positive electrode mixture contains a positive electrode active material and a binder as essential components, and may contain a conductive assistant, a thickener, etc. as optional components.
  • the binder contains a first resin having a first molecular weight M1 and a second resin having a second molecular weight M2, and satisfies M1>M2.
  • M1 and M2 may be weight average molecular weights Mw.
  • the positive electrode mixture layer can be formed, for example, by applying a positive electrode slurry, in which the positive electrode mixture containing particles of the positive electrode active material, which is an essential component, a binder, and further optional components (such as a conductive additive), is dispersed in a dispersion medium, to the surface of the positive electrode current collector and then drying. The coating film after drying may be rolled as necessary.
  • the positive electrode mixture layer may be formed on one surface or both surfaces of the positive electrode current collector. N-methyl-2-pyrrolidone (NMP), cyclohexanone, alcohol, ether, etc. are used as the dispersion medium for the positive electrode slurry.
  • the necessary toughness (elongation) and rigidity are imparted to the positive electrode mixture layer, making the positive electrode less likely to break and the positive electrode current collector and the positive electrode mixture layer less likely to peel off.
  • the positive electrode composite layer In order to increase the energy density of secondary batteries, the positive electrode composite layer has become thicker and more densely packed. The thicker and denser the positive electrode composite layer, the greater the elastic modulus of the entire positive electrode, requiring advanced measures to prevent breakage of the positive electrode and peeling of the positive electrode current collector and the positive electrode composite layer.
  • the positive electrode edge has an exposed portion of the positive electrode current collector provided intermittently in multiple locations along the longitudinal direction of the positive electrode current collector, it is important to prevent breakage at the boundary between the exposed portion and the portion having the positive electrode composite layer.
  • the content of the first resin in the total of the first resin and the second resin may be, for example, 5% by mass or more and 95% by mass or less, 10% by mass or more and 90% by mass or less, or 20% by mass or more and 80% by mass or less.
  • the content of the second resin in the total of the first resin and the second resin may be, for example, 5% by mass or more and 95% by mass or less, 10% by mass or more and 90% by mass or less, or 20% by mass or more and 80% by mass or less.
  • the resin with the largest weight-average molecular weight Mw is the first resin
  • the resin with the smallest weight-average molecular weight Mw is the second resin. If the weight-average molecular weight Mw of the resin with the largest weight-average molecular weight Mw is Mmax, and the weight-average molecular weight Mw of the resin with the smallest weight-average molecular weight Mw is Mmin, the resin with a weight-average molecular weight Mw larger than (Mmax + Mmin)/2 is the first resin, and the resin with a weight-average molecular weight Mw smaller than (Mmax + Mmin)/2 is the second resin.
  • the weight average molecular weight Mw of the first resin is, for example, 300,000 to 2,000,000, or may be 500,000 to 1,500,000, or may be 1,000,000 to 1,500,000. This increases the rigidity of the positive electrode and makes it less likely to peel off.
  • the second resin examples include polyolefin resins such as polyethylene and polypropylene; polyamide resins such as aramid resin; polyimide resins such as polyimide and polyamideimide; acrylic resins such as polyacrylic acid, polymethyl acrylate, and ethylene-acrylic acid copolymer; vinyl resins such as polyacrylonitrile and polyvinyl acetate; polyvinylpyrrolidone; polyethersulfone; rubber, etc. Also, vinylidene fluoride resins may be used as the second resin.
  • nitrile group-containing rubber is preferred because it imparts toughness and extensibility to the positive electrode composite layer.
  • the nitrile group-containing rubber may be a copolymer containing acrylonitrile units and diene (e.g., butadiene) units.
  • the nitrile group-containing rubber may be nitrile rubber (NBR), hydrogenated nitrile rubber (H-NBR), or modified products thereof.
  • the weight average molecular weight Mw of the second resin is, for example, 1,000 to 500,000, or may be 50,000 to 500,000. This increases the rigidity of the positive electrode, making it less susceptible to peeling.
  • the weight average molecular weight Mw of the nitrile group-containing rubber may be 10,000 to 500,000, 20,000 to 300,000, or 100,000 to 300,000.
  • a composite oxide containing lithium and a transition metal such as Ni, Co, or Mn can be used.
  • examples include Li a CoO 2 , Li a NiO 2 , Li a MnO 2 , Li a Co b Ni 1-b O 2 , Li a Co b M 1-b O c , Li a Ni 1-b M b O c , Li a Mn 2 O 4 , Li a Mn 2-b M b O 4 , LiMPO 4 , and Li 2 MPO 4 F
  • M is at least one selected from the group consisting of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, and B).
  • the value a which indicates the molar ratio of lithium, increases or decreases due to charging and discharging.
  • Examples of conductive additives include carbon materials such as graphite, carbon blacks such as furnace black and acetylene black, and carbon fibers (carbon nanotubes (CNTs), carbon fibers other than CNTs).
  • the conductive agents may be used alone or in combination of two or more.
  • a non-porous conductive substrate such as metal foil
  • a porous conductive substrate such as mesh, net, or punched sheet
  • the material of the positive electrode current collector include stainless steel, aluminum, aluminum alloy, and titanium.
  • the thickness of the positive electrode current collector is preferably 1 to 50 ⁇ m, and more preferably 5 to 20 ⁇ m.
  • the negative electrode composite layer may contain an alloy-based material.
  • the alloy-based material contains a phase that reversibly forms an alloy with lithium.
  • the phase that reversibly forms an alloy with lithium may be, for example, silicon (silicon phase).
  • Such a phase expands and contracts greatly during charging and discharging.
  • the content of the alloy-based material in the negative electrode composite layer at the edge of the negative electrode may be greater than that in the main part of the negative electrode. This makes it easy to increase the expansion rate of the negative electrode at the edge of the negative electrode compared to the main part of the negative electrode.
  • the category of alloy-based materials includes Si-containing materials, Sn-containing materials, Si, Sn, Si alloys, Sn alloys, etc. Among them, Si-containing materials have high capacity and are suitable as negative electrode active materials. Si-containing materials contain a silicon phase. Silicon can reversibly form an alloy with lithium. Si-containing materials are materials that can reversibly absorb and release lithium ions.
  • silicon-containing materials contain silicon (silicon phase), they expand and contract greatly during charging and discharging.
  • silicon-containing materials contain silicon (silicon phase)
  • the silicon-containing material may be a composite particle including a silicon phase and a matrix phase in which the silicon phase is dispersed.
  • the matrix phase may be composed of a material having lithium ion conductivity.
  • the matrix phase may include, for example, at least one type selected from the group consisting of a silicon oxide phase and a carbon phase.
  • the silicon oxide phase contains Si and O, and may further contain a third element other than Si and O.
  • the silicon oxide phase may be composed of SiO 2 , may be composed of lithium silicate, or may be composed of both of these.
  • Composite particles that are silicon-containing materials may be, for example, in any of the following forms (a) to (c).
  • a first composite particle including a silicon phase and a silicon dioxide (SiO 2 ) phase in which the silicon phase is dispersed.
  • a second composite particle comprising a silicon phase and a lithium silicate phase in which the silicon phase is dispersed.
  • a third composite particle comprising a silicon phase and a carbon phase in which the silicon phase is dispersed.
  • carbon materials As materials other than the Si-containing material, carbon materials, spinel-type lithium titanium oxide, spinel-type lithium manganese oxide, etc. are preferred. Of these, carbon materials are preferred.
  • the carbon material can be graphite, easily graphitized carbon (soft carbon), hardly graphitized carbon (hard carbon), etc. Of these, graphite is preferred because of its excellent charge/discharge stability and low irreversible capacity.
  • Graphite refers to a carbon material in which the interplanar spacing d002 of the (002) plane measured by X-ray diffraction is, for example, 0.340 nm or less.
  • the crystallite size Lc(002) of graphite measured by X-ray diffraction may be, for example, 5 nm or more, 5 nm or more and 300 nm or less, or 10 nm or more and 200 nm or less.
  • the average particle size of the graphite is, for example, 1 ⁇ m or more and 30 ⁇ m or less.
  • the proportion of the silicon-containing material in the negative electrode active material is, for example, 1% by mass or more and 20% by mass or less, or may be 3% by mass or more and 15% by mass or less, or may be 3% by mass or more and 10% by mass or less. In this case, it is easy to achieve a good balance between improved cycle characteristics and high capacity.
  • binders include resin materials, such as fluororesins such as polytetrafluoroethylene and polyvinylidene fluoride (PVDF); polyolefin resins such as polyethylene and polypropylene; polyamide resins such as aramid resin; polyimide and polyamideimide; acrylic resins such as polyacrylic acid, polymethyl acrylate, and ethylene-acrylic acid copolymer; vinyl resins such as polyacrylonitrile and polyvinyl acetate; polyvinylpyrrolidone; polyethersulfone; and rubber-like materials such as styrene-butadiene copolymer rubber (SBR).
  • resin materials such as fluororesins such as polytetrafluoroethylene and polyvinylidene fluoride (PVDF); polyolefin resins such as polyethylene and polypropylene; polyamide resins such as aramid resin; polyimide and polyamideimide; acrylic resins such as polyacrylic acid, polymethyl acryl
  • Examples of conductive additives include carbons such as acetylene black, carbon fibers (carbon nanotubes (CNT), carbon fibers other than CNT), metal fibers, and metal powders such as aluminum.
  • the conductive agents may be used alone or in combination of two or more.
  • Thickeners include, for example, carboxymethylcellulose (CMC) and its modified forms (including salts such as the Na salt), cellulose derivatives such as methylcellulose (cellulose ethers, etc.), and saponified polymers having vinyl acetate units such as polyvinyl alcohol.
  • CMC carboxymethylcellulose
  • cellulose derivatives such as methylcellulose (cellulose ethers, etc.)
  • saponified polymers having vinyl acetate units such as polyvinyl alcohol.
  • One type of thickener may be used alone, or two or more types may be used in combination.
  • a non-porous conductive substrate such as metal foil
  • a porous conductive substrate such as mesh, net, or punched sheet
  • the material of the negative electrode current collector include stainless steel, nickel, nickel alloy, copper, and copper alloy.
  • the thickness of the negative electrode current collector is preferably 1 to 50 ⁇ m, and more preferably 5 to 20 ⁇ m.
  • FIG. 1 is a schematic cross-sectional view of a secondary battery 10 according to one example of this embodiment.
  • FIG. 2 is a schematic plan view of a positive electrode according to one example of this embodiment.
  • the length of the actual positive electrode may differ from that shown in the schematic diagram, and the number of positive electrode leads may also differ.
  • the following explanation is an example, and the structure of the battery is not particularly limited.
  • the secondary battery 10 may be, for example, a lithium ion secondary battery or a lithium secondary battery (lithium metal secondary battery). As shown in FIG. 1, the secondary battery 10 includes a non-polar case 11, a wound electrode group 14, a plurality of positive electrode leads 112 made of a conductor, a positive electrode terminal 16 made of a conductor, an end surface current collector 19 made of a conductor, a negative electrode current collector 22 made of a conductor, and a sealing plate 23.
  • the case 11 is formed in a cylindrical shape with a bottom and an opening at one end (the lower end in FIG. 1).
  • the case 11 is made of metal.
  • a through hole 12 through which a positive electrode terminal 16 is inserted is formed in the center of the bottom (the upper end in FIG. 1) of the case 11.
  • the case 11 contains an electrolyte (not shown) together with an electrode group 14.
  • a recess 13 is formed that is recessed radially inward of the case 11.
  • the electrode group 14 has a positive electrode 110 and a negative electrode 120.
  • the electrode group 14 is a wound type electrode group in which the positive electrode 110 and the negative electrode 120 are wound with a separator (not shown) interposed therebetween.
  • the electrode group 14 is generally cylindrical overall.
  • each of the positive electrode leads 112 is connected to the exposed portion 113b of the positive electrode current collector of the positive electrode edge portion 113 of the positive electrode 110.
  • the other end of each of the positive electrode leads 112 is provided so as to stand upright from one end face of the electrode group 14.
  • the positive electrode leads 112 are stacked on top of each other and connected to the positive electrode terminal 16 by welding.
  • the number of positive electrode leads 112 is eight, but this is not limited to this. Also, only four of the eight positive electrode leads 112 are shown in FIG. 1.
  • each positive electrode lead 112 is, for example, stainless steel, aluminum, aluminum alloy, nickel, nickel alloy, etc.
  • An insulating member 24 is disposed between the electrode group 14 and the bottom of the case 11 to electrically insulate them from each other.
  • the insulating member 24 is made of, for example, an insulating resin.
  • the insulating member 24 may be attached to the bottom of the case 11.
  • the positive electrode terminal 16 is provided on the opposite side to the electrode group 14, sandwiching multiple positive electrode leads 112 between them.
  • the positive electrode terminal 16 is inserted into the through hole 12 in the bottom of the case 11, penetrating the bottom of the case 11.
  • the positive electrode terminal 16 is made of metal, and a rivet or the like is used.
  • the positive electrode terminal 16 is insulated from the case 11 by a positive electrode gasket 26 made of an insulating material.
  • An insulating plate 25 is placed between the positive electrode terminal 16 and the electrode group 14 to electrically insulate them from each other.
  • the positive electrode terminal 16 has a first terminal member 17 extending from the inside to the outside of the case 11, and a disk-shaped second terminal member 18 joined to the first terminal member 17 and exposed to the outside of the case 11.
  • the first terminal member 17 has a disk-shaped first portion 17a, a hollow cylindrical second portion 17b formed continuously with the first portion 17a and inserted into the through hole 12, and a third portion 17c extending radially outward from the end of the second portion 17b and joined to the second terminal member 18.
  • the first terminal member 17 is welded to the multiple positive electrode leads 112 at the first portion 17a by a laser irradiated in a direction from the first terminal member 17 toward the electrode group 14.
  • the positive electrode terminal 16 is electrically connected to the positive electrode 110 via the multiple positive electrode leads 112 and functions as an external positive electrode terminal of the secondary battery 10.
  • the first terminal member 17 is an example of a terminal member.
  • the positive electrode lead 112 closest to the electrode group 14 has a folded portion 112a formed by folding a part of the positive electrode lead 112 (specifically, a part of the tip side) and on which a part of the laser mark LM by the laser is formed.
  • the folded portion 112a is positioned on the opposite side to the electrode group 14 with the insulating plate 25 in between.
  • the end collector plate 19 is made of metal. There are no particular limitations on the shape of the end collector plate 19, and it may be, for example, generally cross-shaped overall. The end collector plate 19 is electrically connected to the negative electrode 120 of the electrode group 14.
  • the sealing plate 23 seals the opening of the case 11.
  • the sealing plate 23 is made of metal and has a generally circular plate shape.
  • the sealing plate 23 is insulated from the case 11 by a negative electrode gasket 27.
  • the sealing plate 23 is not electrically connected to either the positive electrode 110 or the negative electrode 120 of the electrode group 14, but this is not limited to this.
  • the sealing plate 23 has an explosion-proof mechanism (not shown) that is activated when the internal pressure of the case 11 exceeds a predetermined value.
  • the positive electrode 110 shown in FIG. 2 is in a state before being wound into the electrode group 14.
  • the arrow Y1 indicates the winding direction of the positive electrode 110 when producing the electrode group 14, and is the longitudinal direction of the positive electrode 110.
  • the arrow Y2 perpendicular to the arrow Y1 indicates the winding axis direction of the positive electrode 110 (i.e., the winding axis direction of the electrode group 14) and is the short side direction of the positive electrode 110.
  • the positive electrode 110 has a positive electrode edge 113 including one end 110a in the short side direction of the positive electrode 110, and a positive electrode main part 114 other than the positive electrode edge 113.
  • the positive electrode main part 114 is the region from the positive electrode center end 113a of the positive electrode edge 113 to the other end 110b in the short side direction of the positive electrode 110.
  • the ratio of the width (length in the short side direction) of the positive electrode edge 113 to the width (length in the short side direction) of the positive electrode main part 114 is, for example, in the range of 1:15 to 3:4 or 1:12 to 1:6.
  • the positive electrode edge portion 113 of the positive electrode 110 has an exposed portion 113b of the positive electrode current collector where the positive electrode composite layer is not disposed on the positive electrode current collector, and a first positive electrode composite portion 113c where the positive electrode composite layer is disposed on the positive electrode current collector.
  • the positive electrode main portion 114 has a second positive electrode composite portion 114c where the positive electrode composite layer is disposed on the positive electrode current collector.
  • the exposed portions 113b of the positive electrode current collector are provided at multiple locations (e.g., eight locations) intermittently along the longitudinal direction of the positive electrode current collector.
  • the exposed portions 113b do not have a positive electrode composite layer from one end 110a of the positive electrode 110 in the lateral direction to the positive electrode main portion 114.
  • the spacing between adjacent exposed portions 113b of the positive electrode collector be as uniform as possible.
  • the spacing between adjacent exposed portions 113b of the positive electrode collector may be 0.8 x L100/n to 1.2 x L100/n.
  • a tab-shaped positive electrode lead 112 is connected to each exposed portion 113b of the positive electrode collector.
  • the multiple positive electrode leads 112 are bundled together and connected to the first portion 17a of the first terminal member 17.
  • the negative electrode 120 has a negative electrode composite layer in a region from one end of the negative electrode 120 facing the positive electrode edge portion 113 to just before the other end, and the other end 120b side of the negative electrode 120 in the short direction may have an exposed portion of the negative electrode collector where the negative electrode composite layer is not disposed on the negative electrode collector.
  • the exposed portion of the negative electrode collector is formed along the length of the negative electrode collector, is exposed at the end face of the electrode group 14, and may be connected to the end face collector plate 19 by, for example, laser welding.
  • the configuration of the negative electrode is not particularly limited, and the structure of the battery is not limited to the structure of FIG. 1.
  • the negative electrode may not be connected to the end face collector plate 19, and may be electrically connected to the case 11 via a specified negative electrode lead.
  • the electrolyte may be a liquid electrolyte (electrolytic solution), a gel electrolyte, or a solid electrolyte.
  • the liquid electrolyte is, for example, an electrolytic solution containing a non-aqueous solvent and a salt dissolved in the non-aqueous solvent.
  • the concentration of the salt in the electrolytic solution is, for example, 0.5 mol/L or more and 2 mol/L or less.
  • the electrolytic solution may contain a known additive.
  • the gel electrolyte contains a salt and a matrix polymer, or a salt, a non-aqueous solvent, and a matrix polymer.
  • a matrix polymer for example, a polymer material that absorbs the non-aqueous solvent and gels is used. Examples of the polymer material include fluororesin, acrylic resin, polyether resin, and polyethylene oxide.
  • solid electrolyte for example, a material known in all-solid-state lithium-ion secondary batteries (e.g., oxide-based solid electrolyte, sulfide-based solid electrolyte, halide-based solid electrolyte, etc.) is used.
  • oxide-based solid electrolyte e.g., oxide-based solid electrolyte, sulfide-based solid electrolyte, halide-based solid electrolyte, etc.
  • a liquid non-aqueous electrolyte is prepared by dissolving a salt in a non-aqueous solvent.
  • the salt is an electrolyte salt that ionizes in the electrolyte, and may include, for example, a lithium salt.
  • the electrolyte may include various additives.
  • the electrolyte is usually used in liquid form, but may also have its fluidity restricted by a gelling agent or the like.
  • Examples of the cyclic carboxylate ester include ⁇ -butyrolactone (GBL), ⁇ -valerolactone (GVL), etc.
  • Examples of the chain carboxylate ester include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, etc.
  • the non-aqueous solvent may be used alone or in combination of two or more.
  • lithium salt examples include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiB 10 Cl 10 , lower aliphatic lithium carboxylate, LiCl, LiBr, LiI, borates, imide salts, etc.
  • borates examples include lithium bis(1,2-benzenediolate(2-)-O,O')borate, lithium bis(2,3-naphthalenediolate(2-)-O,O')borate, lithium bis(2,2'-biphenyldiolate(2-)-O,O')borate, lithium bis(5-fluoro-2-oleate-1-benzenesulfonic acid-O,O')borate, etc.
  • the separator has high ion permeability and has appropriate mechanical strength and insulation properties.
  • a microporous thin film, a woven fabric, a nonwoven fabric, etc. can be used.
  • polyolefin such as polypropylene and polyethylene is preferable.
  • the battery includes a positive electrode, a negative electrode, an electrolyte, and a separator. the positive electrode and the negative electrode are wound with the separator interposed therebetween,
  • the positive electrode includes a strip-shaped positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector,
  • the positive electrode has a positive electrode edge portion including one end in a short side direction of the positive electrode, and a positive electrode main portion other than the positive electrode edge portion, the positive electrode edge portion has an exposed portion of the positive electrode current collector that is partially provided at one or more locations along a longitudinal direction of the positive electrode current collector, the exposed portion does not have the positive electrode mixture layer from the one end in the short side direction to the positive electrode main portion
  • the positive electrode mixture layer includes a positive electrode active material and a binder,
  • the binder includes a first resin having a first molecular weight M1 and a second resin having a second molecular weight M2, A secondary battery that satisfies M1
  • the positive electrode edge portion has an exposed portion of the positive electrode current collector that is intermittently provided at a plurality of locations along a longitudinal direction of the positive electrode current collector.
  • the secondary battery according to claim 1 or 2 wherein the mass of the positive electrode mixture layer arranged per unit area of the surface of the positive electrode current collector is 240 g/ m2 or more.
  • First resin A polyvinylidene fluoride (PVdF) having a weight average molecular weight M1 of about 1,000,000
  • the positive electrode slurry was applied to both sides of the aluminum foil positive electrode collector in a predetermined thickness, the coating was dried, and rolled to form a positive electrode composite layer, and a positive electrode as shown in FIG. 2 was obtained. Specifically, the positive electrode slurry was intermittently applied to one end of the short side of the aluminum foil in a predetermined thickness along the longitudinal direction of the positive electrode collector, and the positive electrode slurry was applied to the remaining part of the positive electrode collector in the same thickness, the coating was dried, and rolled to form a positive electrode having a positive electrode edge part having a first positive electrode composite part and a positive electrode main part having a second positive electrode composite part.
  • the mass of the positive electrode composite layer arranged per unit area on the surface of the positive electrode collector was controlled to the value shown in Table 1. Eight exposed parts of the positive electrode collector on the positive electrode edge part were provided, and a positive electrode lead was attached to each exposed part.
  • the width of the positive electrode edge part was set to 12 mm, and the width of the positive electrode main part was set to 62 mm.
  • ⁇ Peel strength> The peel strength of the positive electrode composite layer from the positive electrode current collector was measured by a peel test conforming to JIS K 6854-1. A positive electrode measuring 1.5 cm x 7 cm was cut out as a test piece. The average peel strength was measured when the gripping movement speed was set to 24 mm/min. The average peel strength of each battery was shown in Table 1 as a relative value of the peel strength of each battery when the peel strength of battery B1 was set to 1.0.
  • the mass ratio of SiO x :graphite:SBR:CMC was 5:93:1:1.
  • a negative electrode slurry was applied to both sides of the copper foil, which was the negative electrode current collector, in a specified thickness, then dried and rolled to form a negative electrode composite layer, and a negative electrode as shown in Figure 3 was obtained.
  • the negative electrode slurry was applied uniformly to the surface of the copper foil in a specified thickness, then dried and rolled to simultaneously form a first negative electrode composite part and a second negative electrode composite part. However, a portion of one end side of the negative electrode current collector was left as an exposed part.
  • the thickness of the negative electrode composite part was appropriately changed depending on the thickness of the positive electrode composite layer.
  • VC Vinylene carbonate
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • LiPF 6 LiPF 6 was dissolved to prepare an electrolyte.
  • the content of VC in the entire electrolyte was 5 mass%.
  • the concentration of LiPF 6 in the electrolyte was 1.5 mol/L.
  • the positive and negative electrodes were wound with a separator (a microporous polyethylene film) between them to prepare an electrode group.
  • the electrodes were stacked so that the edge of the positive electrode was positioned on one end face of the electrode group, and the exposed part of the negative electrode current collector was positioned on the other end face of the electrode group.
  • Cylindrical lithium ion secondary batteries as shown in FIG. 1 (batteries A1 to A8 of the embodiment and batteries B1 to B11 of the comparative example) were completed using the electrode group and the electrolyte.
  • the multiple positive electrode leads were bundled and electrically connected to the first portion of the first terminal member.
  • the exposed portion of the negative electrode collector was connected to the end collector plate by laser welding, and the end collector plate was electrically connected to the negative electrode collector plate via a connecting plate.
  • the secondary battery disclosed herein is useful as a main power source for mobile communication devices, portable electronic devices, electric vehicles, etc.
  • Electrode group 16 Positive electrode terminal 17: First terminal member (terminal member) 17a: First portion 17b: Second portion 17c: Third portion 18: Second terminal member 19: End face current collector plate 21: Connecting plate 22: Negative electrode current collector plate 22a: Injection hole 23: Sealing plate 24: Insulating member 25: Insulating plate 26: Positive electrode gasket 27: Negative electrode gasket
  • Positive electrode 110a One end 110b: Other end 112: Positive electrode lead 112a: Folded portion 113: Positive electrode edge portion 113a: Positive electrode central end portion 113b: Positive electrode current collector exposed portion 113c: First positive electrode composite portion 114: Positive electrode main portion 114c: Second positive electrode composite portion

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004079327A (ja) * 2002-08-16 2004-03-11 Hitachi Maxell Ltd 非水二次電池および非水二次電池用正極とその製造方法
JP2008243643A (ja) * 2007-03-28 2008-10-09 Hitachi Vehicle Energy Ltd リチウム二次電池
WO2014051067A1 (ja) * 2012-09-28 2014-04-03 日本ゼオン株式会社 リチウムイオン二次電池
JP2015146248A (ja) * 2014-02-03 2015-08-13 トヨタ自動車株式会社 非水電解質二次電池
WO2022224872A1 (ja) * 2021-04-20 2022-10-27 パナソニックＩｐマネジメント株式会社 リチウム二次電池
WO2023100756A1 (ja) * 2021-11-30 2023-06-08 パナソニックエナジ－株式会社 非水電解質二次電池

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2004079327A (ja) * 2002-08-16 2004-03-11 Hitachi Maxell Ltd 非水二次電池および非水二次電池用正極とその製造方法
JP2008243643A (ja) * 2007-03-28 2008-10-09 Hitachi Vehicle Energy Ltd リチウム二次電池
WO2014051067A1 (ja) * 2012-09-28 2014-04-03 日本ゼオン株式会社 リチウムイオン二次電池
JP2015146248A (ja) * 2014-02-03 2015-08-13 トヨタ自動車株式会社 非水電解質二次電池
WO2022224872A1 (ja) * 2021-04-20 2022-10-27 パナソニックＩｐマネジメント株式会社 リチウム二次電池
WO2023100756A1 (ja) * 2021-11-30 2023-06-08 パナソニックエナジ－株式会社 非水電解質二次電池

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