WO2020059873A1 - Batterie secondaire - Google Patents

Batterie secondaire Download PDF

Info

Publication number
WO2020059873A1
WO2020059873A1 PCT/JP2019/037095 JP2019037095W WO2020059873A1 WO 2020059873 A1 WO2020059873 A1 WO 2020059873A1 JP 2019037095 W JP2019037095 W JP 2019037095W WO 2020059873 A1 WO2020059873 A1 WO 2020059873A1
Authority
WO
WIPO (PCT)
Prior art keywords
positive electrode
separator
active material
electrode active
battery
Prior art date
Application number
PCT/JP2019/037095
Other languages
English (en)
Japanese (ja)
Inventor
恭平 小川
堀内　博志
将之 井原
Original Assignee
株式会社村田製作所
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 株式会社村田製作所 filed Critical 株式会社村田製作所
Publication of WO2020059873A1 publication Critical patent/WO2020059873A1/fr

Links

Images

Classifications

    • 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • 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
    • H01M10/04—Construction or manufacture in general
    • 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
    • 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
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • 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
    • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
    • H01M50/491—Porosity
    • 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 secondary battery.
  • Patent Literature 1 by using polyvinylidene fluoride (PVdF) having a melting point of 165 ° C. or less as a binder for a positive electrode, a coating layer having a stable porous structure while having a high porosity is obtained. Technologies to be realized have been proposed.
  • PVdF polyvinylidene fluoride
  • An object of the present invention is to provide a secondary battery capable of improving safety at the time of an internal short circuit and suppressing a decrease in battery characteristics due to a charge / discharge cycle.
  • the present invention has a positive electrode active material layer containing a fluorine-based binder having a melting point of 166 ° C. or less, and the content of the fluorine-based binder in the positive electrode active material layer is 0.7 mass % To 2.8% by mass, a negative electrode provided opposite to the positive electrode, a separator provided between the positive electrode and the negative electrode, and a polyamide, polyimide, and poly provided between the positive electrode and the separator. And a resin layer containing at least one selected from the group consisting of acrylonitrile.
  • the present invention it is possible to improve safety at the time of an internal short circuit, and to suppress a decrease in battery characteristics due to a charge / discharge cycle.
  • FIG. 1 is an exploded perspective view illustrating an example of a configuration of a nonaqueous electrolyte secondary battery according to a first embodiment of the present invention.
  • FIG. 2 is a sectional view taken along the line II-II of FIG. 1. It is a graph which shows an example of a DSC curve of a fluorinated binder.
  • FIG. 3 is a cross-sectional view illustrating a part of FIG. 2 in an enlarged manner. It is a block diagram showing an example of composition of electronic equipment concerning a 2nd embodiment of the present invention.
  • FIG. 1 shows an example of a configuration of a nonaqueous electrolyte secondary battery (hereinafter, simply referred to as “battery”) according to the first embodiment of the present invention.
  • the battery is a so-called laminated battery, in which the electrode body 20 to which the positive electrode lead 11 and the negative electrode lead 12 are attached is housed inside the film-shaped exterior material 10, and can be reduced in size, weight, and thickness. It has become.
  • the positive electrode lead 11 and the negative electrode lead 12 are respectively directed from the inside of the exterior material 10 to the outside, for example, in the same direction.
  • Each of the positive electrode lead 11 and the negative electrode lead 12 is made of, for example, a metal material such as Al, Cu, Ni, or stainless steel, and has a thin plate shape or a mesh shape, respectively.
  • the outer package 10 is made of, for example, a rectangular aluminum laminate film in which a nylon film, an aluminum foil, and a polyethylene film are laminated in this order.
  • the exterior material 10 is disposed, for example, such that the polyethylene film side and the electrode body 20 face each other, and the respective outer edges are adhered to each other by fusion bonding or an adhesive.
  • An adhesive film 13 is inserted between the exterior material 10 and the positive electrode lead 11 and the negative electrode lead 12 to suppress invasion of outside air.
  • the adhesive film 13 is made of a material having adhesiveness to the positive electrode lead 11 and the negative electrode lead 12, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene or modified polypropylene.
  • the packaging material 10 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film, instead of the above-described aluminum laminated film.
  • a polymer film such as polypropylene
  • a metal film instead of the above-described aluminum laminated film.
  • it may be constituted by a laminate film in which a polymer film is laminated on one or both sides of an aluminum film as a core material.
  • FIG. 2 is a cross-sectional view of the electrode body 20 shown in FIG. 1 along the line II-II.
  • the electrode body 20 is of a wound type, and has a configuration in which a long positive electrode 21 and a long negative electrode 22 are laminated via a long separator 23 and wound flat and spirally. The outermost peripheral portion is protected by a protective tape 24.
  • An electrolytic solution as an electrolyte is injected into the exterior material 10 and impregnated in the positive electrode 21, the negative electrode 22, and the separator 23.
  • the positive electrode 21 includes, for example, a positive electrode current collector 21A and positive electrode active material layers 21B provided on both surfaces of the positive electrode current collector 21A.
  • the positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.
  • the positive electrode current collector 21A may have a plate shape or a mesh shape.
  • the cathode lead 11 may be configured by extending a part of the periphery of the cathode current collector 21A.
  • the positive electrode active material layer 21B contains a positive electrode active material and a binder.
  • the positive electrode active material layer 21B may further include a conductive auxiliary as needed.
  • a lithium-containing compound such as lithium oxide, lithium phosphate, lithium sulfide, or an interlayer compound containing lithium is suitable.
  • the above may be used as a mixture.
  • a lithium-containing compound containing lithium, a transition metal element, and oxygen is preferable.
  • a lithium-containing compound for example, a lithium composite oxide having a layered rock salt type structure shown in the formula (A), a lithium composite phosphate having an olivine type structure shown in the formula (B), and the like are given. No.
  • the lithium-containing compound is more preferably a compound containing at least one of the group consisting of Co, Ni, Mn and Fe as a transition metal element.
  • a lithium-containing compound include a lithium composite oxide having a layered rock salt type structure represented by the formula (C), (D) or (E), and a spinel type compound represented by the formula (F).
  • Examples include a lithium composite oxide having a structure, a lithium composite phosphate having an olivine type structure represented by the formula (G), and specifically, LiNi 0.50 Co 0.20 Mn 0.30 O 2 , LiCoO 2 , and LiNiO. 2 , LiNiaCo 1-a O 2 (0 ⁇ a ⁇ 1), LiMn 2 O 4, LiFePO 4 and the like.
  • M1 represents at least one element selected from Group 2 to Group 15 excluding Ni and Mn.
  • X represents at least one of Group 16 elements and Group 17 elements other than oxygen.
  • P, q, y, and z are 0 ⁇ p ⁇ 1.5, 0 ⁇ q ⁇ 1.0, 0 ⁇ r ⁇ 1.0, ⁇ 0.10 ⁇ y ⁇ 0.20, 0 ⁇ It is a value within the range of z ⁇ 0.2.
  • M2 represents at least one element selected from the group 2 to group 15.
  • a and b are 0 ⁇ a ⁇ 2.0, 0.5 ⁇ b ⁇ 2.0 Value within the range of.
  • M3 is at least one of the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr and W.
  • F, g, h, j and k are 0.8 ⁇ f ⁇ 1.2, 0 ⁇ g ⁇ 0.5, 0 ⁇ h ⁇ 0.5, g + h ⁇ 1, ⁇ 0.1 ⁇ j ⁇ 0.2 and 0 ⁇ k ⁇ 0.1. Note that the composition of lithium differs depending on the state of charge and discharge, and the value of f represents a value in a completely discharged state.
  • M4 is at least one of the group consisting of Co, Mn, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Mo, Sn, Ca, Sr and W.
  • M, n, p and q are 0.8 ⁇ m ⁇ 1.2, 0.005 ⁇ n ⁇ 0.5, ⁇ 0.1 ⁇ p ⁇ 0.2, 0 ⁇ q ⁇ 0
  • the composition of lithium differs depending on the state of charge and discharge, and the value of m represents a value in a completely discharged state.
  • M5 is at least one of the group consisting of Ni, Mn, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Mo, Sn, Ca, Sr and W.
  • R, s, t and u are 0.8 ⁇ r ⁇ 1.2, 0 ⁇ s ⁇ 0.5, ⁇ 0.1 ⁇ t ⁇ 0.2, 0 ⁇ u ⁇ 0.1
  • the composition of lithium varies depending on the state of charge and discharge, and the value of r represents a value in a completely discharged state.
  • M6 is at least one of the group consisting of Co, Ni, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Mo, Sn, Ca, Sr and W.
  • V, w, x, and y are 0.9 ⁇ v ⁇ 1.1, 0 ⁇ w ⁇ 0.6, 3.7 ⁇ x ⁇ 4.1, and 0 ⁇ y ⁇ 0.1.
  • the composition of lithium varies depending on the state of charge and discharge, and the value of v represents a value in a completely discharged state.
  • Li z M7PO 4 ... (G) (However, in the formula (G), M7 is one of the group consisting of Co, Mg, Fe, Ni, Mg, Al, B, Ti, V, Nb, Cu, Zn, Mo, Ca, Sr, W and Zr. And z is a value in the range of 0.9 ⁇ z ⁇ 1.1.
  • the composition of lithium differs depending on the state of charge and discharge, and the value of z is a value in a completely discharged state. Represents.
  • an inorganic compound not containing lithium such as MnO 2 , V 2 O 5 , V 6 O 13 , NiS, and MoS, may be used. it can.
  • the positive electrode active material capable of inserting and extracting lithium may be other than the above. Further, two or more of the above-described positive electrode active materials may be mixed in any combination.
  • the binder includes a fluorine-based binder.
  • the upper limit of the melting point of the fluorinated binder is 166 ° C or lower, preferably 160 ° C or lower, more preferably 155 ° C or lower.
  • the melting point of the fluorine-based binder is 166 ° C. or less, the binder is likely to flow when the positive electrode active material layer 21B is dried (heat treated) in the manufacturing process of the positive electrode 21, and the surface of the positive electrode active material particles can be broadly thinned. Since the film can be favorably covered with the film, the exposed surface of the positive electrode active material particles can be reduced. Therefore, the reaction between the positive electrode active material particles and the electrolytic solution can be suppressed, and safety can be improved.
  • the lower limit of the melting point of the fluorine-based binder is not particularly limited, it is, for example, 152 ° C. or higher.
  • the melting point of the above-mentioned fluorine-based binder is measured as follows. First, the positive electrode 21 is taken out of the battery, washed and dried with dimethyl carbonate (DMC), then the positive electrode current collector 21A is removed, and heated and stirred in an appropriate dispersion medium (for example, N-methylpyrrolidone or the like). Then, the binder is dissolved in the dispersion medium. Thereafter, the positive electrode active material is removed by centrifugation, and the supernatant is filtered, and then the binder is removed by evaporation to dryness or reprecipitation in water.
  • DMC dimethyl carbonate
  • an appropriate dispersion medium for example, N-methylpyrrolidone or the like
  • a sample of several to several tens mg was heated at a heating rate of 1 to 10 ° C./min by a differential scanning calorimeter (DSC, for example, Rigaku Thermoplus plus DSC 8230 manufactured by Rigaku Corporation), and then heated at 100 to 250 ° C.
  • DSC differential scanning calorimeter
  • the temperature showing the maximum endothermic amount is defined as the melting point of the fluorine-based binder.
  • a temperature at which a polymer becomes fluid by heating and heating is defined as a melting point.
  • PVdF polyvinylidene fluoride
  • the fluorine-based binder it is preferable to use a homopolymer of vinylidene fluoride (VdF).
  • VdF a copolymer of vinylidene fluoride
  • the polyvinylidene fluoride which is a copolymer, swells and dissolves in the electrolytic solution. The characteristics of the positive electrode 21 may be deteriorated because the bonding is easy and the binding force is weak.
  • the polyvinylidene fluoride one obtained by modifying a part of the terminal or the like with a carboxylic acid such as maleic acid may be used.
  • the content of the fluorine-based binder in the positive electrode active material layer 21B is 0.7% by mass to 2.8% by mass, preferably 1.0% by mass to 2.8% by mass, and more preferably 1.4% by mass. % To 2.8% by mass.
  • the content of the fluorine-based binder is less than 0.7% by mass, the amount of the binder present in the positive electrode active material layer 21B becomes insufficient, and the adhesiveness between the positive electrode active material layer 21B and the separator 23 decreases. Therefore, generation of a gap between the positive electrode active material layer 21B and the separator 23 cannot be suppressed. Therefore, it is not possible to maintain a favorable lithium ion movement path, and it is not possible to suppress a decrease in cycle characteristics, and it is also not possible to suppress battery swelling due to a charge / discharge cycle.
  • the content of the fluorine-based binder is less than 0.7% by mass, the surface coverage of the cathode active material particles with the binder becomes insufficient, so that the reaction between the cathode active material particles and the electrolytic solution can be suppressed. become unable. Therefore, the safety of the battery is reduced. Further, when the content of the fluorine-based binder is less than 0.7% by mass, the binding between the positive electrode active material particles and the binding between the positive electrode active material particles and the positive electrode current collector 21A become insufficient. When the cathode 21 is wound flat, the cathode active material layer 21B falls off the cathode current collector 21A.
  • the binder when the content of the binder exceeds 2.8% by mass, the binder excessively covers the surface of the positive electrode active material particles, and the binder excessively covers the surface of the positive electrode active material layer. Thereby, the occlusion and release of lithium ions with respect to the positive electrode active material particles are inhibited, and the movement of lithium ions at the interface between the separator and the positive electrode active material layer 21B is inhibited. Therefore, the migration resistance of lithium ions in the battery increases, and the cycle characteristics deteriorate.
  • the content of the binder exceeds 2.8% by mass, fusion between a weak portion of the curved portion of the electrode body 20 (turn portion of the positive electrode 21 and the negative electrode 22) and fusion of the flat portion of the electrode body 20 are caused.
  • the electrode body 20 Since the difference in adhesiveness with the strong part becomes remarkable, the electrode body 20 is deformed by expansion and contraction accompanying the cycle. Further, when the content of the binder exceeds 2.8% by mass, the flexibility of the positive electrode active material layer 21B decreases, and when the positive electrode 21 is wound flat, cracks occur in the positive electrode 21.
  • the content of the above-mentioned fluorine-based binder is measured as follows. First, the cathode 21 is taken out of the battery, washed with DMC, and dried. Next, a sample of several to several tens of mg was subjected to a differential thermal balance (TG-DTA, for example, Rigaku Thermoplus TG8120 manufactured by Rigaku Corporation) at a temperature rising rate of 1 to 5 ° C./min in an air atmosphere at 600 ° C. C., and the content of the fluorine-based binder in the positive electrode active material layer 21B is determined from the weight loss at that time.
  • TG-DTA differential thermal balance
  • the amount of weight loss due to the binder can be determined by isolating the binder as described in the method for measuring the melting point of the binder, performing TG-DTA measurement of the binder alone in an air atmosphere, Can be confirmed by examining how many times they burn.
  • the conductive additive for example, at least one carbon material of graphite, carbon fiber, carbon black, acetylene black, Ketjen black, carbon nanotube, graphene, and the like can be used.
  • the conductive assistant may be any material having conductivity, and is not limited to a carbon material.
  • a metal material or a conductive polymer material may be used as the conductive assistant.
  • the shape of the conductive additive include, but are not limited to, granules, scales, hollows, needles, and cylinders.
  • the negative electrode 22 includes, for example, a negative electrode current collector 22A and negative electrode active material layers 22B provided on both surfaces of the negative electrode current collector 22A.
  • the anode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.
  • the negative electrode current collector 22A may have a plate shape or a mesh shape.
  • the negative electrode lead 12 may be configured by extending a part of the peripheral edge of the negative electrode current collector 22A.
  • the anode active material layer 22B includes one or more anode active materials capable of inserting and extracting lithium.
  • the negative electrode active material layer 22B may further include at least one of a binder and a conductive additive as necessary.
  • the electrochemical equivalent of the negative electrode 22 or the negative electrode active material is larger than the electrochemical equivalent of the positive electrode 21.
  • lithium metal does not precipitate on the negative electrode 22 during charging. Is preferred.
  • the negative electrode active material examples include carbon materials such as non-graphitizable carbon, easily graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, carbon fibers, and activated carbon. Is mentioned.
  • the coke includes pitch coke, needle coke, petroleum coke and the like.
  • An organic polymer compound fired body is obtained by firing a polymer material such as a phenol resin or a furan resin at an appropriate temperature and carbonizing the material, and a part thereof is hardly graphitizable carbon or easily graphitizable carbon. Some are classified as.
  • These carbon materials are preferable because a change in crystal structure that occurs during charge and discharge is very small, a high charge and discharge capacity can be obtained, and good cycle characteristics can be obtained.
  • graphite is preferable because it has a large electrochemical equivalent and can obtain a high energy density.
  • non-graphitizable carbon is preferable because excellent cycle characteristics can be obtained.
  • a material having a low charge / discharge potential specifically, a material having a charge / discharge potential close to lithium metal is preferable because a high energy density of the battery can be easily realized.
  • the negative electrode active material capable of increasing the capacity include a material containing at least one of a metal element and a metalloid element as a constituent element (for example, an alloy, a compound, or a mixture). If such a material is used, a high energy density can be obtained. In particular, when used together with a carbon material, high energy density can be obtained and excellent cycle characteristics can be obtained, which is more preferable.
  • alloys include alloys containing one or more metal elements and one or more metalloid elements in addition to alloys composed of two or more metal elements. Further, a nonmetallic element may be included.
  • the structure includes a solid solution, a eutectic (eutectic mixture), an intermetallic compound, and a structure in which two or more of them coexist.
  • a negative electrode active material for example, a metal element or a metalloid element capable of forming an alloy with lithium is given.
  • a metal element or a metalloid element capable of forming an alloy with lithium.
  • Specific examples include Mg, B, Al, Ti, Ga, In, Si, Ge, Sn, Pb, Bi, Cd, Ag, Zn, Hf, Zr, Y, Pd and Pt. These may be crystalline or amorphous.
  • the negative electrode active material a material containing a metal element or a metalloid element belonging to the group 4B in the short-periodic periodic table as a constituent element is preferable, and a material containing at least one of Si and Sn as a constituent element is more preferable. This is because Si and Sn have a large ability to insert and extract lithium and can obtain a high energy density.
  • Examples of such a negative electrode active material include a simple substance, an alloy, or a compound of Si, a simple substance, an alloy, or a compound of Sn, and a material having at least one or more of them.
  • Si for example, Sn, Ni, Cu, Fe, Co, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb, Nb, Mo, Al
  • second constituent elements other than Si examples include those containing at least one selected from the group consisting of P, Ga, and Cr.
  • Sn for example, as a second constituent element other than Sn, Si, Ni, Cu, Fe, Co, Mn, Zn, In, Ag, Ti, Ge, Bi, Sb, Nb, Mo, Al
  • Examples include those containing at least one selected from the group consisting of P, Ga, and Cr.
  • Examples of the compound of Sn or the compound of Si include those containing O or C as a constituent element. These compounds may contain the second constituent element described above.
  • the Sn-based negative electrode active material contains Co, Sn, and C as constituent elements and has a low crystallinity or an amorphous structure.
  • Other negative electrode active materials include, for example, metal oxides or polymer compounds capable of inserting and extracting lithium.
  • metal oxide include lithium titanium oxide containing Li and Ti, such as lithium titanate (Li 4 Ti 5 O 12 ), iron oxide, ruthenium oxide, and molybdenum oxide.
  • the polymer compound include polyacetylene, polyaniline, and polypyrrole.
  • binder examples include resin materials such as polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), styrene butadiene rubber (SBR), and carboxymethyl cellulose (CMC), and these resin materials as main components. At least one selected from the group consisting of copolymers and the like is used.
  • PVdF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PAN polyacrylonitrile
  • SBR styrene butadiene rubber
  • CMC carboxymethyl cellulose
  • the separator 23 is an insulating porous film that separates the positive electrode 21 and the negative electrode 22, suppresses a short circuit due to contact between the two electrodes, and allows lithium ions to pass therethrough. Since the electrolyte is held in the pores of the separator 23, the separator 23 preferably has characteristics of high resistance to the electrolyte, low reactivity, and difficulty in expanding.
  • the separator 23 is made of, for example, a porous material made of polytetrafluoroethylene, polyolefin resin (such as polypropylene (PP) or polyethylene (PE)), acrylic resin, styrene resin, polyester resin, nylon resin, or a resin obtained by blending these resins. It may be formed of a porous film, and may have a structure in which two or more of these porous films are laminated.
  • PP polypropylene
  • PE polyethylene
  • a porous film made of polyolefin is preferable because it has an excellent short circuit prevention effect and can improve the safety of the battery by a shutdown effect.
  • polyethylene is preferable as a material constituting the separator 23 because it can obtain a shutdown effect in the range of 100 ° C. or more and 160 ° C. or less and has excellent electrochemical stability.
  • low-density polyethylene, high-density polyethylene, and linear polyethylene are suitably used because they have an appropriate melting temperature and are easily available.
  • a material obtained by copolymerizing or blending a resin having chemical stability with polyethylene or polypropylene can be used.
  • the porous membrane may have a structure of three or more layers in which a polypropylene layer, a polyethylene layer, and a polypropylene layer are sequentially laminated.
  • the method for producing the separator 23 may be either a wet method or a dry method.
  • a non-woven fabric may be used as the separator 23.
  • Aramid fiber, glass fiber, polyolefin fiber, polyethylene terephthalate (PET) fiber, nylon fiber, or the like can be used as the fiber constituting the nonwoven fabric. Further, these two or more kinds of fibers may be mixed to form a nonwoven fabric.
  • the heat shrinkage at 150 ° C. of the separator 23 provided with the resin layer 23A is preferably 30% or less. When the heat shrinkage of the separator 23 is 30% or less, the heat shrinkage at the time of short circuit can be suppressed.
  • FIG. 4 is an enlarged cross-sectional view of a part of FIG.
  • a resin layer 23A is provided on both surfaces of the separator 23.
  • the resin layer 23A may be provided only on one surface facing the positive electrode 21.
  • it is preferable that the resin layers 23A are provided on both surfaces.
  • the resin layer 23A may be provided on the surface of the positive electrode active material layer 21B and the negative electrode active material layer 22B.
  • the resin layer 23A contains a resin material containing at least one selected from the group consisting of polyamide, polyimide and polyacrylonitrile.
  • the resin material may be fibrillated and have a three-dimensional network structure in which the fibrils are connected to each other continuously.
  • Polyamide, polyimide, and polyacrylonitrile can maintain good adhesion between the positive electrode active material layer 21B and the separator 23, though they have low swellability. Therefore, even if the electrode body 20 repeatedly expands and contracts due to the charge / discharge cycle, the generation of the gap between the positive electrode active material layer 21B and the separator 23 can be suppressed. Therefore, the movement path of the lithium ions can be maintained. In addition, swelling of the battery due to charge / discharge cycles can be suppressed.
  • polyamide, polyimide and polyacrylonitrile have high heat resistance, safety at the time of internal short circuit can be improved.
  • the glass transition point of the resin layer 23A is preferably from 50 ° C to 400 ° C.
  • the glass transition point of the resin layer 23A is 50 ° C. or higher, it is possible to suppress heat shrinkage at the time of short circuit.
  • the glass transition point of the resin layer 23A is 400 ° C. or lower, the fusion between the positive electrode 21 and the separator 23 and the fusion between the negative electrode 22 and the separator 23 during high-temperature pressing are ensured, and the expansion after the cycle is increased. Can be suppressed.
  • the glass transition temperature (Tg) is the temperature corresponding to the intersection of the extrapolation line of the linear portion on the low temperature side of the storage elastic modulus curve and the tangent at the point where the slope of the curve in the glass transition region is considered to be the maximum.
  • the average thickness of the resin layer 23A is preferably 1 ⁇ m or more and 5 ⁇ m or less.
  • the average thickness of the resin layer 23A is 1 ⁇ m or more, fusion between the positive electrode 21 and the separator 23 and fusion between the negative electrode 22 and the separator 23 during high-temperature pressing are ensured, and expansion after a cycle is suppressed. Can be.
  • the average thickness of the resin layer 23A is 5 ⁇ m or less, cycle characteristics can be improved.
  • the average air permeability of the separator 23 provided with the resin layer 23A is preferably 10 s / 100 ml or more and 100 s / 100 ml or less.
  • the average air permeability of the separator 23 provided with the resin layer 23A is 10 s / 100 ml or more, the heat shrinkage at the time of short circuit can be suppressed.
  • the average air permeability of the separator 23 provided with the resin layer 23A is 100 s / 100 ml or less, the cycle characteristics can be improved.
  • the peel strength between the positive electrode 21 and the separator 23 is preferably 5 mN / mm or more and 35 mN / mm or less.
  • the peel strength is 5 mN / mm or more, generation of a gap between the positive electrode active material layer 21B and the separator 23 can be suppressed. Therefore, a favorable lithium ion movement path can be maintained, and a decrease in cycle characteristics can be suppressed, and swelling of the battery accompanying a charge / discharge cycle can be suppressed.
  • the peel strength is 35 mN / mm or less
  • the adhesion between the positive electrode 21 and the separator 23 becomes excessively high and the inhibition of lithium ion migration at the interface between the separator and the positive electrode active material layer 21B is suppressed. can do. Therefore, an increase in the migration resistance of lithium ions in the battery can be suppressed, and a decrease in cycle characteristics can be suppressed.
  • the peel strength between the positive electrode 21 and the separator 23 is measured according to iso29862: 2007 (JIS Z0237).
  • the electrolyte is a so-called non-aqueous electrolyte, and includes an organic solvent (non-aqueous solvent) and an electrolyte salt dissolved in the organic solvent.
  • the electrolytic solution may contain a known additive in order to improve battery characteristics. Note that, instead of the electrolytic solution, an electrolytic layer containing the electrolytic solution and a polymer compound serving as a holder for holding the electrolytic solution may be used. In this case, the electrolyte layer may be in a gel state.
  • a cyclic carbonate such as ethylene carbonate or propylene carbonate can be used, and it is preferable to use one of ethylene carbonate and propylene carbonate, particularly a mixture of both. This is because the cycle characteristics can be further improved.
  • organic solvent it is preferable to use a mixture of chain carbonates such as diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate and methylpropyl carbonate in addition to these cyclic carbonates. This is because high ionic conductivity can be obtained.
  • the organic solvent further contains 2,4-difluoroanisole or vinylene carbonate. This is because 2,4-difluoroanisole can further improve the discharge capacity, and vinylene carbonate can further improve the cycle characteristics. Therefore, it is preferable to use a mixture of these, because the discharge capacity and cycle characteristics can be further improved.
  • organic solvents include butylene carbonate, ⁇ -butyrolactone, ⁇ -valerolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, and 4-methyl-1,3 -Dioxolan, methyl acetate, methyl propionate, acetonitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropironitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N- Examples thereof include dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, dimethylsulfoxide, and trimethyl phosphate.
  • Examples of the electrolyte salt include a lithium salt, and one kind may be used alone, or two or more kinds may be used in combination.
  • the lithium salt LiPF 6, LiBF 4, LiAsF 6, LiClO 4, LiB (C 6 H 5) 4, LiCH 3 SO 3, LiCF 3 SO 3, LiN (SO 2 CF 3) 2, LiC (SO 2 CF 3 ) 3 , LiAlCl 4 , LiSiF 6 , LiCl, lithium difluoro [oxolate-O, O ′] borate, lithium bisoxalate borate, or LiBr.
  • LiPF 6 is preferable because high ion conductivity can be obtained and cycle characteristics can be further improved.
  • the positive electrode 21 is manufactured as follows. First, for example, a positive electrode mixture is prepared by mixing a positive electrode active material, a binder, and a conductive auxiliary, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) to form a paste. A positive electrode mixture slurry is prepared. Next, the positive electrode mixture slurry is applied to the positive electrode current collector 21A, the solvent is dried, and compression molding is performed by a roll press or the like to form the positive electrode active material layer 21B, and the positive electrode 21 is obtained.
  • NMP N-methyl-2-pyrrolidone
  • the negative electrode 22 is manufactured as follows. First, for example, a negative electrode mixture is prepared by mixing a negative electrode active material and a binder, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a paste-like negative electrode mixture slurry. I do. Next, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, the solvent is dried, and compression molding is performed by a roll press or the like to form the negative electrode active material layer 22B, and the negative electrode 22 is obtained.
  • a negative electrode mixture is prepared by mixing a negative electrode active material and a binder, and this negative electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a paste-like negative electrode mixture slurry. I do.
  • the negative electrode mixture slurry is applied to the negative electrode current collector 22A, the solvent is dried, and compression molding is performed by a roll press or the like to form the negative electrode active material layer 22B, and the negative electrode 22 is
  • the resin layer 23A is manufactured as follows. First, at least one resin material selected from the group consisting of polyamide, polyimide and polyacrylonitrile is dispersed in a solvent to prepare a resin solution. Next, the resin solution is uniformly applied to both surfaces of the separator 23 and dried to form the resin layer 23A. After applying the resin solution to both surfaces of the separator 23, the resin solution is passed through a poor solvent and a solvent-friendly bath of the solvent to separate phases, and then dried to form the resin layer 23A. You may.
  • the wound electrode body 20 is manufactured as follows. First, the cathode lead 11 is attached to one end of the cathode current collector 21A by welding, and the anode lead 12 is attached to one end of the anode current collector 22A by welding. Next, the positive electrode 21 and the negative electrode 22 are wound around a flat core through a separator 23 having resin layers 23A formed on both surfaces, and wound many times in the longitudinal direction. The electrode body 20 is obtained by bonding the protective tape 24.
  • the exterior body 10 seals the electrode body 20 as follows. First, the electrode body 20 is sandwiched between the package members 10, and the outer peripheral edge portion excluding one side is heat-fused into a bag shape, and is housed inside the package member 10. At that time, an adhesive film 13 is inserted between the positive electrode lead 11 and the negative electrode lead 12 and the exterior material 10. Note that the adhesive film 13 may be attached to each of the positive electrode lead 11 and the negative electrode lead 12 in advance. Next, after injecting the electrolytic solution into the exterior material 10 from one side of the unfused part, one side of the unfused part is heat-sealed in a vacuum atmosphere to be sealed. Thus, the batteries shown in FIGS. 1 and 2 are obtained.
  • the resin layer 23A containing the material is combined with the separator 23 provided on both sides, and the content of the fluorine-based binder in the positive electrode active material layer 21B is 0.7% by mass or more and 2.8% by mass or less.
  • FIG. 5 shows an example of the configuration of an electronic device 400 according to the second embodiment of the present invention.
  • the electronic device 400 includes an electronic circuit 401 of the electronic device main body and the battery pack 300.
  • Battery pack 300 is electrically connected to electronic circuit 401 via positive electrode terminal 331a and negative electrode terminal 331b.
  • the electronic device 400 may have a configuration in which the battery pack 300 is detachable.
  • Examples of the electronic device 400 include a notebook personal computer, a tablet computer, a mobile phone (for example, a smartphone), a portable information terminal (Personal Digital Assistants: PDA), a display device (LCD (Liquid Crystal Display), and an EL (Electro Luminescence).
  • a notebook personal computer for example, a tablet computer
  • a mobile phone for example, a smartphone
  • a portable information terminal Personal Digital Assistants: PDA
  • a display device LCD (Liquid Crystal Display)
  • EL Electro Luminescence
  • imaging device eg, digital still camera, digital video camera, etc.
  • audio equipment eg, portable audio player
  • game equipment e.g., cordless phone handset, electronic book, electronic dictionary, radio, headphone, navigation System, memory card, pacemaker, hearing aid, power tool, electric shaver, refrigerator, air conditioner, TV, stereo, water heater, microwave oven, dishwasher, washing machine, dryer, lighting equipment, toy, medical equipment, robot Load conditioners, although traffic signals and the like, without such limited thereto.
  • the electronic circuit 401 includes, for example, a CPU (Central Processing Unit), a peripheral logic unit, an interface unit, a storage unit, and the like, and controls the entire electronic device 400.
  • a CPU Central Processing Unit
  • the battery pack 300 includes an assembled battery 301 and a charge / discharge circuit 302. Battery pack 300 may further include an exterior material (not shown) that accommodates assembled battery 301 and charge / discharge circuit 302 as necessary.
  • the assembled battery 301 is configured by connecting a plurality of secondary batteries 301a in series and / or in parallel.
  • the plurality of secondary batteries 301a are connected in, for example, n parallel and m series (n and m are positive integers).
  • FIG. 5 shows an example in which six rechargeable batteries 301a are connected in two parallel and three series (2P3S).
  • the secondary battery 301a the battery according to the above-described first embodiment is used.
  • the battery pack 300 includes an assembled battery 301 including a plurality of secondary batteries 301a.
  • the battery pack 300 includes a single secondary battery 301a instead of the assembled battery 301. May be adopted.
  • the charging / discharging circuit 302 is a control unit that controls charging / discharging of the battery pack 301. Specifically, at the time of charging, the charge / discharge circuit 302 controls charging of the battery pack 301. On the other hand, at the time of discharging (that is, at the time of using the electronic device 400), the charging / discharging circuit 302 controls discharging to the electronic device 400.
  • the exterior material for example, a case made of a metal, a polymer resin, or a composite material thereof can be used.
  • the composite material include a laminate in which a metal layer and a polymer resin layer are laminated.
  • Example 1-1 (Preparation process of positive electrode) A positive electrode was produced as follows. First, 98.3% by mass of a lithium-cobalt composite oxide (LiCoO 2 ) as a positive electrode active material, 1.4% by mass of PVdF (homopolymer of VdF) having a melting point of 155 ° C. as a binder, and 0% carbon black as a conductive additive. And 3% by mass, to obtain a positive electrode mixture. The positive electrode mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone: NMP) to obtain a paste-like positive electrode mixture slurry. .
  • NMP N-methyl-2-pyrrolidone
  • the positive electrode mixture slurry was applied to the positive electrode current collector (aluminum foil) using a coating device, and then dried to form a positive electrode active material layer. Finally, the positive electrode active material layer was compression-molded using a press until the mixture density reached 4.0 g / cm 3 .
  • a negative electrode was manufactured as follows. First, 96% by mass of artificial graphite powder as a negative electrode active material, After mixing 1% by mass of styrene butadiene rubber (SBR) as a first binder, 2% by mass of PVdF as a second binder, and 1% by mass of carboxymethyl cellulose (CMC) as a thickener, a negative electrode mixture was obtained. This negative electrode mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone: NMP) to obtain a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was applied to the negative electrode current collector (copper foil) using a coating device and then dried. Finally, the negative electrode active material layer was compression molded using a press.
  • SBR styrene butadiene rubber
  • CMC carboxymethyl cellulose
  • Step of preparing electrolyte solution An electrolyte was prepared as follows. First, a mixed solvent was prepared by mixing EC, PC, and ethyl formate in a volume ratio of 11: 9: 80. Subsequently, in this mixed solvent, lithium hexafluorophosphate (LiPF 6 ) as an electrolyte salt was dissolved at a concentration of 1 mol / l to prepare an electrolyte solution.
  • LiPF 6 lithium hexafluorophosphate
  • a resin layer (coat layer) was prepared as follows. First, a resin solution was obtained by dispersing a polyamide (Pervio: Sumitomo Chemical) as a resin material in an organic solvent (N-methyl-2-pyrrolidone: NMP) so as to be an 8% solution. Subsequently, a resin solution was applied to both sides of the microporous polyethylene film using a coating device and then dried to form a resin layer. The resin layer was formed to have a thickness of 3.0 ⁇ m.
  • a polyamide Pervio: Sumitomo Chemical
  • NMP N-methyl-2-pyrrolidone
  • a laminated battery was manufactured as follows. First, a positive electrode lead made of aluminum was welded to the positive electrode current collector, and a negative electrode lead made of copper was welded to the negative electrode current collector. Subsequently, the positive electrode and the negative electrode are adhered to each other via a microporous polyethylene film having a resin layer formed on both sides, and then wound in the longitudinal direction, and a protective tape is attached to the outermost peripheral portion, thereby flattening. A wound electrode body having a shape was produced. Next, this electrode body was loaded between the package members, and three sides of the package member were heat-sealed, and one side had an opening without heat-sealing.
  • a moisture-proof aluminum laminated film in which a nylon film having a thickness of 25 ⁇ m, an aluminum foil having a thickness of 40 ⁇ m, and a polypropylene film having a thickness of 30 ⁇ m were laminated in this order from the outermost layer was used.
  • Example 1-2 A battery was obtained in the same manner as in Example 1-1, except that polyimide was used as the resin material in the process of forming the resin layer.
  • Example 1-3 A battery was obtained in the same manner as in Example 1-1, except that polyacrylonitrile was used as a resin material in the step of forming the resin layer.
  • Example 1-1 A battery was obtained in the same manner as in Example 1-1, except that PVdF was used as the resin material in the step of forming the resin layer.
  • Example 1-2 A battery was obtained in the same manner as in Example 1-1, except that the resin alone was not formed on both surfaces of the polyethylene film and the film alone was used as a separator.
  • Examples 2-1 to 2-3, Comparative Examples 2-1 and 2-2 In the process of producing the positive electrode, in the same manner as in Examples 1-1 to 1-3 and Comparative Examples 1-1 and 1-2, except that PVdF (homopolymer of VdF) having a melting point of 166 ° C. was used as a binder. I got a battery.
  • PVdF homopolymer of VdF
  • Examples 5-1 to 5-3, Comparative examples 5-1 and 5-2 99.0% by mass of lithium-cobalt composite oxide (LiCoO 2 ) as a positive electrode active material, 0.7% by mass of PVdF (homopolymer of VdF) having a melting point of 166 ° C. as a binder, and 0.3% of carbon black as a conductive additive. % By mass, to obtain a battery in the same manner as in Examples 1-1 to 1-3 and Comparative examples 1-1 and 1-2, except that a positive electrode mixture was obtained.
  • LiCoO 2 lithium-cobalt composite oxide
  • PVdF homopolymer of VdF
  • Example 6-1 to 6-3, Comparative Examples 6-1 and 6-2 96.9% by mass of lithium-cobalt composite oxide (LiCoO 2 ) as a positive electrode active material, 2.8% by mass of PVdF (homopolymer of VdF) having a melting point of 166 ° C. as a binder, and 0.3% of carbon black as a conductive auxiliary agent % By mass, to obtain a battery in the same manner as in Examples 1-1 to 1-3 and Comparative examples 1-1 and 1-2, except that a positive electrode mixture was obtained.
  • LiCoO 2 lithium-cobalt composite oxide
  • PVdF homopolymer of VdF
  • Examples 8-1 to 8-5 In the manufacturing process of the laminated battery, the peeling strength between the positive electrode and the separator is changed by adjusting the compression pressure in the range of 2 to 30 kgf when compressing the laminated battery in which the electrolyte is injected from both flat surfaces in the range of 2 to 30 kgf. A battery was obtained in the same manner as in Example 1-1, except that the above procedure was repeated.
  • Example 9-1 to 9-4 A battery was obtained in the same manner as in Example 1-1, except that the thickness of the coat layer was changed by adjusting the applied thickness of the mixed solution in the process of forming the coat layer.
  • Example 10-1 to 10-4 A battery was obtained in the same manner as in Example 1-1, except that a coat layer was formed on a microporous polyethylene film having different air permeability.
  • Example 11-1 to 11-4 In the step of forming the coat layer, PVdF (a homopolymer of VdF) is dispersed in an organic solvent (N-methyl-2-pyrrolidone: NMP) so as to be a 3 to 15% solution, whereby the separator on which the coat layer is formed is formed.
  • NMP N-methyl-2-pyrrolidone
  • peel strength of separator with coat layer The peel strength of the separator was measured based on iso29862: 2007 (JIS Z 0237). Note that a general-purpose double-sided adhesive tape G9000 manufactured by Dexerials was used as a peeling tape.
  • Gurley air permeability of the separator with coat layer Using a Gurley air permeability meter having a circular hole with an outer diameter of 28.6 mm, the Gurley air permeability was measured at 10 positions in the width direction of the separator with a coat layer, and the measured values were simply averaged ( (Arithmetic average) to obtain the average air permeability of the separator with the coat layer. Gurley air permeability was measured according to JIS P8117.
  • a test piece was prepared by cutting a separator having a coat layer into a size of 5 cm ⁇ 5 cm. Next, the test piece was sandwiched between two stainless steel plates fixed with clips, left in a thermostat at 150 ° C. for 30 minutes, taken out, and the length of the test piece was measured. Next, the reduction ratio of the length based on the length before the test was determined as a percentage, and this was defined as the heat shrinkage of the separator with a coat layer.
  • Table 1 shows the configurations and evaluation results of the batteries of Examples 1-1 to 2-3 and Comparative examples 1-1 to 3-5.
  • Table 2 shows the configurations and evaluation results of the batteries of Examples 5-1 to 6-3 and Comparative examples 4-1 to 7-5.
  • Table 3 shows the configurations and evaluation results of the batteries of Examples 8-1 to 8-5, 9-1 to 9-4, 10-1 to 10-4, and 11-1 to 11-4.
  • Table 1 shows the following. Examples 1-1 to 1-3, 2-1 to 2-3: Positive electrode active material layer containing PVdF having a melting point of 166 ° C. or less (hereinafter referred to as “low melting point PVdF” as appropriate), polyamide, and polyimide Alternatively, in a battery in which a separator provided with a resin layer containing polyacrylonitrile is combined, safety at the time of an internal short circuit (a nail penetration test) can be improved, a decrease in cycle characteristics is suppressed, and after a cycle, Battery expansion can be suppressed.
  • PVdF Positive electrode active material layer containing PVdF having a melting point of 166 ° C. or less
  • Comparative Examples 1-1 and 2-1 In a battery in which a positive electrode active material layer containing PVdF having a low melting point was combined with a separator provided with a resin layer containing PVdF, safety during an internal short circuit (a nail penetration test) was obtained. Can be improved, but the cycle characteristics deteriorate and the expansion of the battery after the cycle increases. This decrease in cycle characteristics is considered to be due to the following reasons. That is, since the resin layer contains PVdF, it easily swells, and the low melting point PVdF of the positive electrode active material layer excessively covers the surface of the positive electrode active material particles.
  • the low melting point PVdF of the material layer is mixed at the interface between the separator and the positive electrode active material layer, the surface of the positive electrode active material layer is excessively covered with PVdF.
  • the increase in expansion after the cycle is considered to be due to the following reason. That is, if the resin layer contains PVdF and easily swells, the adhesiveness between the separator and the positive electrode active material layer is improved, but the melting of the curved portion (turn portion of the electrode) of the flat electrode wound electrode body is performed. The difference in adhesion between the weakly adhered portion and the strongly fused flat portion becomes remarkable, and the electrode body is deformed due to expansion and contraction of the electrode body during a charge / discharge cycle.
  • Comparative Examples 1-2 and 2-2 In a battery in which a positive electrode active material layer containing PVdF having a low melting point was combined with a separator having no resin layer, the cycle characteristics were deteriorated, and the battery expanded after the cycle. Becomes larger. It is considered that the cycle characteristics and the expansion of the battery after the cycle increase due to the following reasons. That is, since no resin layer is provided on the surface of the separator, the adhesiveness between the separator and the positive electrode and between the separator and the negative electrode are extremely weak, and a gap is easily generated between the positive electrode and the negative electrode. Therefore, the movement path of lithium ions is cut between the positive electrode and the negative electrode, and the cycle characteristics are degraded.
  • the battery expands with the charge / discharge cycle.
  • the melting point of PVdF is 166 ° C.
  • the voltage of the nail penetration test is 4.25 V, and the safety at the time of an internal short circuit (a nail penetration test) is reduced.
  • This reduction in safety is due to the fact that PVdF having a melting point of 166 ° C. has a lower coating property of the positive electrode active material particles than PVdF having a melting point of 155 ° C., and that the resin layer is not provided on the separator. Is considered to be due to low heat resistance.
  • Comparative Examples 3-1 to 3-3 Good safety is obtained in a battery in which a positive electrode active material layer containing PVdF having a melting point of more than 166 ° C. and a separator provided with a resin layer containing polyamide, polyimide or polyacrylonitrile are provided. However, cycle characteristics are deteriorated, and battery expansion after cycling is increased.
  • Comparative Example 3-4 In a battery in which a positive electrode active material layer containing PVdF having a melting point of more than 166 ° C. and a separator provided with a resin layer containing PVdF were combined, deterioration in cycle characteristics was suppressed, and Although the expansion of the battery can be suppressed, safety at the time of an internal short circuit (a nail penetration test) is reduced. It is considered that the suppression of the deterioration of the cycle characteristics and the suppression of the expansion after the cycle are due to the following reasons. That is, when the melting point of PVdF of the positive electrode active material layer exceeds 166 ° C., the surface coating of the positive electrode active material particles becomes insufficient.
  • the area of the surface of the positive electrode active material layer covered with PVdF is appropriately reduced, and inhibition of lithium ion transfer at the interface between the separator and the positive electrode active material layer is suppressed.
  • the adhesiveness between the separator and the positive electrode active material layer is appropriately reduced, and deformation of the electrode body due to expansion and contraction of the electrode body due to charge / discharge cycles is suppressed.
  • this decrease in safety is due to the fact that the resin layer containing PVdF has lower heat resistance than the resin layer containing polyamide, polyimide or polyacrylonitrile, and the surface coating of the positive electrode active material particles is insufficient. It is considered something.
  • Comparative Example 3-5 In a battery in which a positive electrode active material layer containing PVdF having a melting point of more than 166 ° C. and a separator having no resin layer are combined, safety during an internal short circuit (a nail penetration test) is reduced. At the same time, the cycle characteristics are particularly deteriorated, and the expansion of the battery after the cycle is particularly large. It is considered that the decrease in the cycle characteristics and the increase in the battery expansion after the cycle become remarkable for the following reasons. That is, when the resin layer is not provided on the surface of the separator and the melting point of PVdF of the positive electrode active material layer exceeds 166 ° C., the surface coating of the positive electrode active material particles becomes insufficient.
  • the adhesiveness between the separator and the positive electrode and between the separator and the negative electrode become extremely weak, and a gap is particularly easily generated between the positive electrode and the negative electrode.
  • the movement path of lithium ions is particularly easily cut between the positive electrode and the negative electrode, and the cycle characteristics are significantly reduced.
  • the battery expands significantly due to a charge / discharge cycle.
  • this decrease in safety is due to the fact that a separator without a resin layer containing polyamide, polyimide or polyacrylonitrile has low heat resistance and insufficient surface coating of the positive electrode active material particles. Conceivable.
  • Table 2 shows the following.
  • a positive electrode active material layer containing low melting point PVdF and a separator provided with a resin layer containing polyamide, polyimide or polyacrylonitrile have a PVdF content of less than 0.7% by mass in the positive electrode active material.
  • the cycle characteristics deteriorate, and the battery expansion after the cycle increases.
  • This decrease in cycle characteristics and increase in battery expansion after cycling are considered to be due to the following reasons. That is, the content of PVdF in the positive electrode active material layer is too small, and the surface coating of the positive electrode active material particles becomes insufficient. Therefore, the adhesiveness between the separator and the positive electrode active material layer is weakened, and a gap is easily generated between the positive electrode and the negative electrode.
  • the occlusion and release of lithium ions with respect to the positive electrode active material particles are inhibited, and the movement of lithium ions at the interface between the separator and the positive electrode active material layer is inhibited. Therefore, the migration resistance of lithium ions in the battery increases, and the cycle characteristics deteriorate.
  • the increase in expansion after the cycle is considered to be due to the following reason. That is, when the content of PVdF exceeds 2.8% by mass, the adhesion between the separator and the positive electrode active material layer is improved, but the curved portion (turn portion of the electrode) of a flat wound wound electrode body and the like are used. The adhesion between the weakly fused portion and the strongly fused flat portion becomes remarkable, and the electrode body is deformed by expansion and contraction of the electrode body during a charge / discharge cycle.
  • the positive electrode active material layer will fall off. This dropping of the positive electrode active material layer is considered to be because the content of PVdF contained in the positive electrode active material layer is too small, and the adhesiveness (that is, peel strength) between the positive electrode current collector and the positive electrode active material layer is reduced. .
  • Table 3 shows the following.
  • the peel strength between the positive electrode and the separator is 5 mN / mm or more and 35 mN / mm or less
  • safety at the time of an internal short circuit (a nail penetration test) can be improved, deterioration of cycle characteristics is suppressed, and high-temperature storage is performed.
  • the effect of suppressing battery swelling (gas generation) at the time (hereinafter, referred to as “effect of improving safety”) can be further improved.
  • the average thickness of the resin layer is 1 ⁇ m or more and 5 ⁇ m or less, effects such as improvement of safety can be further improved.
  • the average air permeability of the separator provided with the resin layer is 10 s / 100 ml or more and 100 s / 100 ml or less, effects such as improved safety can be further improved.
  • the heat shrinkage at 150 ° C. of the separator provided with the resin layer is 30% or less, safety at the time of an internal short circuit (a nail penetration test) can be further improved.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

L'invention concerne une batterie secondaire comportant : une électrode positive qui a une couche de substance active d'électrode positive contenant un liant à base de fluor ayant un point de fusion inférieur ou égal à 166 °C, la teneur du liant à base de fluor dans la couche de substance active d'électrode positive étant de 0,7 à 2,8 % en masse ; une électrode négative qui est disposée à l'opposé de l'électrode positive ; un séparateur qui est disposé entre l'électrode positive et l'électrode négative ; et une couche de résine qui est disposée entre l'électrode positive et le séparateur et qui contient au moins un élément choisi dans le groupe constitué par le polyamide, le polyimide et le polyacrylonitrile.
PCT/JP2019/037095 2018-09-20 2019-09-20 Batterie secondaire WO2020059873A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2018176673 2018-09-20
JP2018-176673 2018-09-20

Publications (1)

Publication Number Publication Date
WO2020059873A1 true WO2020059873A1 (fr) 2020-03-26

Family

ID=69887257

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2019/037095 WO2020059873A1 (fr) 2018-09-20 2019-09-20 Batterie secondaire

Country Status (1)

Country Link
WO (1) WO2020059873A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006032246A (ja) * 2004-07-21 2006-02-02 Sanyo Electric Co Ltd 非水電解質電池用セパレータ及び非水電解質電池
JP2009123483A (ja) * 2007-11-14 2009-06-04 Sony Corp セパレータ及び電池
JP2014078434A (ja) * 2012-10-11 2014-05-01 Fujifilm Corp 非水電解液二次電池
WO2014208596A1 (fr) * 2013-06-25 2014-12-31 日立化成株式会社 Séparateur pour éléments électrochimiques et batterie rechargeable lithium-ion
JP2016197505A (ja) * 2015-04-02 2016-11-24 旭化成株式会社 捲回体
JP2017117754A (ja) * 2015-12-25 2017-06-29 三星エスディアイ株式会社Samsung SDI Co., Ltd. 二次電池電極用バインダ組成物、二次電池電極合剤、二次電池電極および二次電池

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006032246A (ja) * 2004-07-21 2006-02-02 Sanyo Electric Co Ltd 非水電解質電池用セパレータ及び非水電解質電池
JP2009123483A (ja) * 2007-11-14 2009-06-04 Sony Corp セパレータ及び電池
JP2014078434A (ja) * 2012-10-11 2014-05-01 Fujifilm Corp 非水電解液二次電池
WO2014208596A1 (fr) * 2013-06-25 2014-12-31 日立化成株式会社 Séparateur pour éléments électrochimiques et batterie rechargeable lithium-ion
JP2016197505A (ja) * 2015-04-02 2016-11-24 旭化成株式会社 捲回体
JP2017117754A (ja) * 2015-12-25 2017-06-29 三星エスディアイ株式会社Samsung SDI Co., Ltd. 二次電池電極用バインダ組成物、二次電池電極合剤、二次電池電極および二次電池

Similar Documents

Publication Publication Date Title
JP6332483B2 (ja) セパレータおよび電池
KR101455663B1 (ko) 리튬 이온 2차 배터리
US8828605B2 (en) Lithium-ion secondary battery
KR101568418B1 (ko) 부극 및 이차 전지
US20070248884A1 (en) Negative electrode and secondary battery
CN110462885B (zh) 用于圆柱形卷芯的条形电极以及包含其的锂二次电池
US20210043941A1 (en) Battery
WO2020059803A1 (fr) Batterie secondaire
JP2012054147A (ja) 非水電解質電池用負極および非水電解質電池
JP6656370B2 (ja) リチウムイオン二次電池および組電池
JP4840302B2 (ja) セパレータおよびこれを用いた電池
JP4551539B2 (ja) 非水電解質二次電池
US20210210789A1 (en) Secondary battery
JP4802217B2 (ja) 非水電解質二次電池
JP2009054469A (ja) 非水二次電池
JP2019164965A (ja) リチウムイオン二次電池
WO2019208806A1 (fr) Batterie
WO2020059874A1 (fr) Batterie secondaire
JP7107382B2 (ja) 二次電池
WO2020080245A1 (fr) Électrode négative pour batterie secondaire au lithium-ion et batterie secondaire au lithium-ion
WO2020059873A1 (fr) Batterie secondaire
JPWO2020241837A1 (ja) 二次電池
US20240047828A1 (en) Non-aqueous electrolyte secondary battery
US20210159540A1 (en) Nonaqueous electrolyte secondary battery
WO2020059802A1 (fr) Batterie secondaire

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 19862857

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 19862857

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: JP