JP6282458B2 - Non-aqueous electrolyte secondary battery electrode winding element, non-aqueous electrolyte secondary battery using the same, and non-aqueous electrolyte secondary battery electrode winding element manufacturing method - Google Patents

Description

  The present invention relates to an electrode winding element for a non-aqueous electrolyte secondary battery and a method for manufacturing the same.

  There are many examples in which a polyvinylidene fluoride (PVDF) -based fluororesin is used as a matrix polymer of a gel electrolyte of a lithium ion secondary battery. For example, a technique for forming a porous film made of PVDF-based fluorine resin on the surface of a separator is known. In this technique, for example, a porous film is formed on the surface of a separator by the following method.

  In the first method, a slurry is prepared by dissolving a fluororesin in an organic solvent such as NMP (N-methylpyrrolidone), dimethylacetamide, or acetone. And after apply | coating this slurry to a separator or an electrode, the coating layer which made the fluororesin porous is formed by phase-separating a fluororesin using poor solvents, such as water, methanol, and a tripropylene glycol. In the second method, a heated slurry is prepared by dissolving a fluororesin in a heated electrolyte using dimethyl carbonate, propylene carbonate, ethylene carbonate, or the like as a solvent. And a coating layer is formed by apply | coating this heating slurry to a separator or an electrode. Then, the fluororesin is transferred to a gel (a porous film swollen with an electrolytic solution) by cooling the coating layer.

Japanese Patent Laid-Open No. 10-110052 JP 2012-190784 A JP 2010-538173 A JP 2011-204627 A

  By the way, the separator with the PVDF porous film formed on the surface by the above method has a problem that it is difficult to handle in the manufacturing process because it is less slidable than the unformed separator and easily generates static electricity. . Specifically, when the separator is a winding element separator, there is a problem that the winding element is distorted due to poor slipperiness when the strip-like positive electrode, negative electrode, and separator are stacked. . When the winding element is distorted, there is a problem that it becomes difficult to store the winding element in the case. Further, the non-aqueous electrolyte secondary battery using this winding element has a problem that the cycle life is not sufficient due to the influence of the distortion.

  On the other hand, for example, as disclosed in Patent Documents 1 to 4, a technique using fluororesin particles or ceramic particles is known. In the technique disclosed in Patent Document 1, a part of particles made of a fluororesin is projected from a porous film that is a separator. In the technique disclosed in Patent Document 2, ceramic particles are contained in the separator. In the technique disclosed in Patent Document 3, a part of the pores in the nonwoven fabric is filled with fluororesin particles. In the technique disclosed in Patent Document 4, a negative electrode is manufactured using an aqueous slurry in which a composite polymer of a fluororesin and a polymer having an oxygen-containing functional group is dispersed. However, these techniques cannot solve the above problems.

  Therefore, the present invention has been made in view of the above problems, and the object of the present invention is produced using a separator that is easy to handle in the manufacturing process, suppresses distortion of the winding element, and New and improved electrode winding element for nonaqueous electrolyte secondary battery capable of improving cycle life of nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery using the same, and nonaqueous electrolyte secondary It is providing the manufacturing method of the electrode winding element for secondary batteries.

  In order to solve the above problems, according to an aspect of the present invention, a strip-like positive electrode, a strip-like negative electrode, a strip-like porous film disposed between the strip-like positive electrode and the strip-like negative electrode, fluororesin-containing fine particles, and a fluororesin An adhesive layer that supports the contained fine particles and includes a binder whose total volume is smaller than the total volume of the fluororesin-containing fine particles, and is formed on the surface of the band-shaped porous film, An electrode winding element for a non-aqueous electrolyte secondary battery is provided.

  This winding element has a small distortion as shown in the examples described later. Moreover, since the interface between each electrode and the separator is stabilized by the adhesive layer, the cycle life is improved. Moreover, the porous separator in which the strip separator, that is, the adhesive layer is formed, is also excellent in slipperiness. Therefore, the strip separator has good handleability.

  Here, the strip-shaped negative electrode includes a negative electrode active material layer including a negative electrode active material and fluororesin-containing fine particles, and the adhesive layer may be bound to the negative electrode active material layer. In this case, the strip-shaped negative electrode and the separator The interface with is further stabilized. Therefore, the cycle life is further improved.

  The fluororesin-containing fine particles may be spherical particles, and in this case, the cycle life is further improved.

  Further, the fluororesin may contain polyvinylidene fluoride, and in this case, the cycle life is further improved.

  Further, the binder may contain a polyolefin resin, and in this case, the cycle life is further improved.

  The adhesive layer may contain inorganic particles, and in this case, the cycle life is further improved.

  According to another aspect of the present invention, there is provided a non-aqueous electrolyte secondary battery comprising the electrode winding element for a non-aqueous electrolyte secondary battery.

  The winding element included in this nonaqueous electrolyte secondary battery has a small distortion. Further, the cycle life of the nonaqueous electrolyte secondary battery is good. In addition, the strip separator included in the nonaqueous electrolyte secondary battery, that is, the porous film on which the adhesive layer is formed is excellent in slipperiness. Therefore, the strip separator has good handleability.

  According to another aspect of the present invention, an aqueous slurry containing fluororesin-containing fine particles and a binder that supports the fluororesin-containing fine particles and has a total volume smaller than the total volume of the fluororesin-containing fine particles There is provided a method for producing an electrode winding element for a non-aqueous electrolyte secondary battery, comprising the steps of coating on the surface of a membrane and drying.

  According to this viewpoint, a strip separator excellent in handleability is produced. Moreover, the winding element produced using this strip separator has a small distortion. Moreover, in this winding element, since the interface between each electrode and the separator is stabilized, the cycle life of the nonaqueous electrolyte secondary battery produced using this winding element is improved.

  As described above, the winding element according to the present invention is manufactured using a separator that is easy to handle in the manufacturing process. Further, the wound element can suppress the distortion and improve the cycle life of the nonaqueous electrolyte secondary battery.

It is sectional drawing which shows schematic structure of the lithium ion secondary battery which concerns on embodiment of this invention. It is sectional drawing which shows schematic structure of the electrode laminated body which concerns on embodiment of this invention.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

<1. Configuration of lithium ion secondary battery>
(Overall configuration of lithium ion secondary battery)
First, with reference to FIG.1 and FIG.2, the structure of the lithium ion secondary battery which concerns on embodiment of this invention is demonstrated. FIG. 1 shows a plan view of the winding element 100 and an enlarged view in which a region A of the winding element 100 is enlarged. FIG. 2 shows a plan view of an electrode laminate 100a in which a positive electrode, a negative electrode, and two separators are laminated, and an enlarged view in which a region A of the electrode laminate 100a is enlarged.

  The lithium ion secondary battery includes a winding element 100, a non-aqueous electrolyte solution, and an exterior material. The winding element 100 is obtained by winding an electrode stack 100a in which a strip-like negative electrode 10, a strip-like separator 20, a strip-like positive electrode 30, and a strip-like separator 20 are laminated in this order in the longitudinal direction and compressing in the arrow B direction.

(Configuration of negative electrode)
The strip-shaped negative electrode 10 includes a negative electrode current collector 10b and a negative electrode active material layer 10a formed on both surfaces of the negative electrode current collector 10b. The strip-shaped negative electrode 10 is a so-called aqueous negative electrode.

Specifically, the negative electrode active material layer 10a includes a negative electrode active material, a thickener, and a binder. The negative electrode active material constituting the negative electrode active material layer 10a is not particularly limited as long as it is a material capable of alloying with lithium or reversibly occluding and releasing lithium (Li). For example, lithium, indium (In), tin (Sn), aluminum (Al), silicon (Si) and other metals and alloys and oxides thereof, transition metal oxides such as Li _4/3 Ti _5/3 O ₄ and SnO, and artificial Graphite, natural graphite, mixture of artificial graphite and natural graphite, natural graphite coated with artificial graphite, non-graphitizable carbon, graphite carbon fiber, resin-fired carbon, pyrolytic vapor-grown carbon, coke, mesocarbon Carbon such as microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon fiber, etc. Materials and the like. These negative electrode active materials may be used independently and 2 or more types may be used together. Among these, it is preferable to use a graphite-based material as a main material.

  The thickener adjusts the negative electrode mixture slurry to a viscosity suitable for coating and functions as a binder in the negative electrode active material layer 10a. As the thickener, a water-soluble polymer is preferably used, and examples thereof include a cellulose-based polymer, a polyacrylic acid-based polymer, polyvinyl alcohol, polyethylene oxide, and the like. Examples of the cellulosic polymer include metal derivatives or ammonium salts of carboxymethyl cellulose (CMC), cellulose derivatives such as methyl cellulose, ethyl cellulose, and hydroxyalkyl cellulose. . Other examples include polyvinylpyrrolidone (PVP), starch, starch phosphate, casein, various modified starches, chitin, chitosan derivatives and the like. These thickeners can be used alone or in combination of two or more. Among these, cellulose polymers are preferable, and alkali metal salts of carboxymethyl cellulose are particularly preferable.

  The binder binds the negative electrode active materials to each other. Preferable examples of the binder include fluororesin-containing fine particles. The fluororesin-containing fine particles are fine particles containing a fluororesin and serve as a binder for the negative electrode active material layer 10a. The fluororesin-containing fine particles are preferably composed of a fluororesin.

  Preferable examples of the fluororesin constituting the fluororesin-containing fine particles include PVDF and a copolymer containing PVDF. Examples of the copolymer containing PVDF include a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), a copolymer of vinylidene fluoride (VDF) and tetrafluoroethylene (TFE), and the like. .

  The particle size of the fluororesin-containing fine particles (the diameter when the fluorine-based fine particles are regarded as spheres) is not particularly limited, and may be any value as long as it can be dispersed in the negative electrode active material layer 10a. For example, the average particle diameter (arithmetic average value of particle diameter) of the fluororesin-containing fine particles may be about 80-500 nm. The average particle diameter of the fluororesin-containing fine particles is measured by, for example, a laser diffraction method (laser diffraction method). Specifically, the particle size distribution of the fluorine-based fine particles may be measured by a laser diffraction method, and the arithmetic average value of the particle sizes may be calculated based on this particle size distribution.

  In addition, the fluororesin-containing fine particles may be combined with various types of processing, for example, other resins within a range that does not impair the effects of the present embodiment. For example, the fluororesin-containing fine particles may be combined with an acrylic resin. The fluororesin-containing fine particles have an IPN (Inter-penetrating network polymer) -like structure.

  The fluororesin-containing fine particles are produced (synthesized) by, for example, emulsion polymerization of a monomer (for example, VDF) constituting the fluororesin. The fluorine-based fine particles may be produced by suspension polymerization of a monomer constituting the fluororesin and pulverizing coarse particles obtained thereby.

  In the present embodiment, since the fluororesin is used as fine particles, the fluororesin-containing fine particles are dispersed in water to form a latex. Therefore, water can be used as a solvent for the slurry for forming the negative electrode active material layer 10a.

  The fluororesin-containing fine particles of the present embodiment are particularly preferably spherical particles. The spherical fluororesin-containing fine particles can be produced, for example, by the emulsion polymerization method described above. The shape of the fluororesin-containing fine particles (and the structure described above) can be confirmed by, for example, SEM (scanning electron microscope).

  The negative electrode active material layer 10a may further contain fine particles of an elastomeric polymer as a binder. Elastomer polymers include SBR (styrene butadiene rubber), BR (butadiene rubber), NBR (nitrile butadiene rubber), NR (natural rubber), IR (isoprene rubber), EPDM (ethylene-propylene-diene ternary copolymer) Coalesced), CR (chloroprene rubber), CSM (chlorosulfonated polyethylene), acrylic acid ester, methacrylic acid ester copolymer, and partially hydride or complete hydride, acrylic acid ester copolymer, etc. Is mentioned. These may be modified with a monomer having a polar functional group such as carboxylic acid, sulfonic acid, phosphoric acid, or hydroxyl group in order to improve binding properties.

  The content ratio of the thickener and the binder in the negative electrode active material layer is not particularly limited as long as the content ratio is applicable to the negative electrode active material layer of the lithium ion secondary battery.

  The negative electrode current collector 10b may be any conductor as long as it is a conductor, and is made of, for example, copper, stainless steel, nickel-plated steel, or the like. A negative electrode terminal is connected to the negative electrode current collector 10b.

  The strip-shaped negative electrode 10 is produced by the following method, for example. That is, a negative electrode mixture slurry (aqueous slurry) is formed by dispersing the material of the negative electrode active material layer in water, and this negative electrode mixture slurry is applied onto a current collector. Thereby, a coating layer is formed. Next, the coating layer is dried. In the negative electrode mixture slurry, fluororesin fine particles and elastomeric polymer fine particles are dispersed in the negative electrode active material layer 10a. Next, the dried coating layer is rolled together with the negative electrode current collector 10b. Thereby, the strip-shaped negative electrode 10 is produced.

  The strip-shaped separator 20 includes a strip-shaped porous membrane 20c and an adhesive layer 20a formed on both surfaces of the strip-shaped porous membrane 20c.

  The belt-like porous membrane 20c is not particularly limited, and any belt-like porous membrane 20c may be used as long as it is used as a separator for a lithium ion secondary battery. As the belt-like porous film 20c, it is preferable to use a porous film or a non-woven fabric exhibiting excellent high rate discharge performance alone or in combination. Examples of the resin constituting the band-shaped porous film 20c include polyolefin resins represented by polyethylene, polypropylene, and the like, polyethylene terephthalate, and polybutylene terephthalate. Representative polyester resin, PVDF, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetra Fluoroethylene (tetrafluoroeth) len) copolymer, vinylidene fluoride-trifluoroethylene copolymer, vinylidene fluoride-fluoroethylene copolymer, vinylidene fluoride-hexafluoroacetone copolymer, vinylidene fluoride -Ethylene copolymer, vinylidene fluoride-propylene copolymer, vinylidene fluoride-trifluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene (Hexafluoropropylene) copolymer, vinylidene fluoride-ethylene ( thylene) - can be exemplified tetrafluoroethylene (tetrafluoroethylene) copolymers.

  The adhesive layer 20 a includes the above-described fluororesin-containing fine particles 20 b-1 and the binder 20 b-2, and binds the strip separator 20, the strip negative electrode 10, and the strip positive electrode 30. In FIG. 1, the adhesive layer 20a is formed on both surfaces of the strip separator 20, but may be formed on at least one surface.

  The fluororesin-containing fine particles 20b-1 are the same as those contained in the negative electrode active material layer 10a. The binder 20b-2 carries the fluororesin-containing fine particles 20b-1 in the adhesive layer 20a. The total volume of the binder 20b-2 in the adhesive layer 20a is smaller than the total volume of the fluororesin-containing fine particles 20b-1 in the adhesive layer 20a. Specifically, (total volume of fluororesin-containing fine particles 20b-1) / (total volume of binder 20b-2) is preferably about 2 to 20.

  The binder 20b-2 preferably contains a polyolefin resin. More preferably, the binder 20b-2 is made of a polyolefin resin. Examples of the polyolefin resin include polyethylene, polypropylene, ethylene-vinyl acetate copolymers, and ionomers thereof. In addition, although the binder 20b-2 may be comprised with the elastomer type polymer mentioned above, it is preferable that it is a binder containing polyolefin resin.

  The adhesive layer 20a may further include a thickener for imparting a viscosity suitable for the above-described coating. Further, the adhesive layer 20a may further contain inorganic particles for adjusting the degree of porosity and thermal stability. The inorganic particles are specifically ceramic particles, and more specifically metal oxide particles. Examples of the metal oxide particles include fine particles such as alumina, boehmite, titania, zirconia, magnesia, zinc oxide, aluminum hydroxide, and magnesium hydroxide. The average particle diameter of the inorganic particles is preferably 1/2 or less of the thickness of the adhesive layer. The average particle diameter of the inorganic particles is, for example, 50% cumulative volume (D50) measured by a laser diffraction method or the like. Although the content rate of an inorganic particle will not be restrict | limited especially if it is in the range with which the effect of this embodiment is acquired, For example, what is necessary is just 70 mass% or less with respect to the total mass of the contact bonding layer 20a.

  The adhesive layer 20a is produced by the following method. That is, the adhesive layer mixture slurry (aqueous slurry) is prepared by dispersing and dissolving the material of the adhesive layer 20a in water. Next, the adhesive layer mixture slurry is applied to at least one surface of both surfaces of the belt-like porous film 20c to form a coating layer. Subsequently, this coating layer is dried. Thereby, the adhesive layer 20a is formed.

  The strip-shaped positive electrode 30 includes a positive electrode current collector 30b and a positive electrode active material layer 30a formed on both surfaces of the positive electrode current collector 30b. The positive electrode active material layer 30a includes at least a positive electrode active material, and may further include a conductive agent and a binder. The positive electrode active material is not particularly limited as long as it is a material capable of reversibly occluding and releasing lithium ions. For example, lithium cobalt oxide (LCO), lithium nickelate, lithium nickel cobaltate, nickel cobalt aluminum acid Lithium (hereinafter also referred to as “NCA”), nickel cobalt lithium manganate (hereinafter also referred to as “NCM”), lithium manganate, lithium iron phosphate, nickel sulfide, copper sulfide, sulfur , Iron oxide, vanadium oxide and the like. These positive electrode active materials may be used independently and 2 or more types may be used together.

The positive electrode active material is preferably a lithium salt of a transition metal oxide having a layered rock salt type structure, among the examples of the positive electrode active materials listed above. As a lithium salt of a transition metal oxide having such a layered rock salt structure, for example, Li _1-x-yz Ni _x Co _y Al _z O ₂ (NCA) or Li _1-x-yz Ni _x Co _y Mn _z O ₂ (NCM) (0 <x <1, 0 <y <1, 0 <z <1, and x + y + z <1) is represented by a lithium salt of a ternary transition metal oxide. Can be mentioned.

  The conductive agent is, for example, carbon black such as ketjen black or acetylene black, natural graphite, artificial graphite, or the like, but is not particularly limited as long as it is intended to increase the conductivity of the positive electrode.

  The binder binds the positive electrode active materials to each other and bonds the positive electrode active material and the positive electrode current collector 30b. The type of the binder is not particularly limited, and any binder can be used as long as it is used for the positive electrode active material layer of the conventional lithium ion secondary battery. For example, polyvinylidene fluoride, vinylidene fluoride (VDF) -hexafluoropropylene (HFP) copolymer, vinylidene fluoride-perfluorovinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene (polyvinylidene fluoride) tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer, ethylene-propylene-diene terpolymer, styrene-butadiene rubber butadiene rubber, butadiene rubber acrylonitrile-butadie erubber, fluororubber, polyvinyl acetate, polymethylmethacrylate, polyethylene, cellulosic nitrate, and the like. There is no particular limitation as long as it can be bound on the body 21.

  The positive electrode current collector 30b may be any material as long as it is a conductor. For example, the positive electrode current collector 30b is made of aluminum, stainless steel, nickel-plated steel, or the like. A positive electrode terminal is connected to the positive electrode current collector 30b.

  The strip-shaped positive electrode 30 is produced by the following method, for example. That is, a positive electrode mixture slurry is formed by dispersing the material of the positive electrode active material layer in an organic solvent or water, and this positive electrode mixture slurry is applied onto a current collector. Thereby, a coating layer is formed. Next, the coating layer is dried. Next, the dried coating layer is rolled together with the positive electrode current collector 30b. Thereby, the strip-shaped positive electrode 30 is produced.

  The electrode laminate 100a is manufactured by laminating the strip-shaped negative electrode 10, the strip-shaped separator 20, the strip-shaped positive electrode 30, and the strip-shaped separator 20 in this order. Accordingly, the strip separator 20 is disposed on one surface (front surface) of the electrode laminate 100a, and the strip negative electrode 10 is disposed on the back surface. Therefore, when the electrode laminate 100a is wound, a portion of the electrode laminate 100a is present. The back surface (that is, the strip-shaped negative electrode 10) of the other part of the electrode laminate 100a is in contact with the surface (that is, the strip-shaped separator 20).

The non-aqueous electrolyte solution is a solution in which an electrolyte is dissolved in an organic solvent. The electrolyte is not particularly limited. For example, in this embodiment, a lithium salt can be used. Examples of the lithium salt include LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiPF ₆ , LiPF _6-x (C _n F _{2n + 1} ) _x (where 1 <x <6, n = 1 or 2), LiSCN, LiBr, LiI, Inorganic ion salts containing one of lithium (Li), sodium (Na) or potassium (K) such as Li ₂ SO ₄ , Li ₂ B ₁₀ Cl ₁₀ , NaClO ₄ , NaI, NaSCN, NaBr, KClO ₄ , KSCN, etc. LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) ₃ , (CH ₃ ) ₄ NBF ₄ , (CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n-C ₄ H ₉ ) ₄ NClO ₄ , (n-C ₄ H ₉ ) ₄ NI, (C ₂ H ₅ ) ₄ N-maleate, _{(C 2 H 5) 4 N} -benzoate, (C 2 H 5) 4 N-phtalate, lithium stearyl sulfonate (stearyl sulfonic acid lithium), lithium octyl sulfonate (octyl sulfonic acid), lithium dodecylbenzenesulfonate (dodecyl organic ionic salts such as benzene sulphonic acid), and the like, and these ionic compounds can be used alone or in admixture of two or more. The concentration of the electrolyte salt may be the same as that of the nonaqueous electrolytic solution used in the conventional lithium secondary battery, and is not particularly limited. In this embodiment, a nonaqueous electrolytic solution containing an appropriate lithium compound (electrolyte salt) at a concentration of about 0.8 to 1.5 mol / L can be used.

  Examples of the organic solvent include propylene carbonate, ethylene carbonate, butylene carbonate, chloroethylene carbonate, vinylene carbonate (vinyl carbonate), and the like. Esters; cyclic esters such as γ-butyrolactone and γ-valerolactone; dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate (eth) linear carbonates such as l methyl carbonate; methyl format, methyl acetate, butyric acid methyl, ethyl acetate, ethyl propionate, etc. Tetrahydrofuran or its derivatives; 1,3-dioxane, 1,4-dioxane, 1,2-dimethoxyethane, 1,4-dibutoxyethane , Ethers such as methyl diglyme; Nitriles such as acetyl, benzonitrile; dioxolane or derivatives thereof; ethylene sulfide, sulfolane, sultone or derivatives thereof alone or the like A mixture of two or more types can be mentioned, but is not limited thereto. The non-aqueous electrolyte solution is impregnated in the strip separator 20. In addition, you may add a well-known conductive support agent, an additive, etc. to said each electrode suitably. The exterior material is, for example, an aluminum laminate.

<2. Manufacturing method of non-aqueous electrolyte lithium ion secondary battery>
Next, the manufacturing method of a nonaqueous electrolyte lithium ion secondary battery is demonstrated.
(Method for producing strip-shaped positive electrode)
The strip-shaped positive electrode 30 is produced by the following method, for example. That is, a positive electrode mixture slurry is formed by dispersing the material of the positive electrode active material layer in an organic solvent or water, and this positive electrode mixture slurry is applied onto a current collector. Thereby, a coating layer is formed. Next, the coating layer is dried. Next, the dried coating layer is rolled together with the positive electrode current collector 30b. Thereby, the strip-shaped positive electrode 30 is produced.

(Method for producing strip-shaped negative electrode)
The strip-shaped negative electrode 10 is produced by the following method, for example. That is, a negative electrode mixture slurry is formed by dispersing the material of the negative electrode active material layer in water, and this negative electrode mixture slurry is applied onto a current collector. Thereby, a coating layer is formed. Next, the coating layer is dried. In the negative electrode mixture slurry, fluororesin fine particles and elastomeric polymer fine particles are dispersed in the negative electrode active material layer 10a. Next, the dried coating layer is rolled together with the negative electrode current collector 10b. Thereby, the strip-shaped negative electrode 10 is produced.

  (Manufacturing method of strip separator)

  The strip separator 20 is produced by the following method. That is, the adhesive layer mixture slurry is prepared by dispersing and dissolving the material of the adhesive layer 20a in water. Next, the adhesive layer mixture slurry is applied to at least one surface of both surfaces of the belt-like porous film 20c to form a coating layer. Subsequently, this coating layer is dried. Thereby, the adhesive layer 20a is formed. That is, the strip separator 20 is produced.

(Wound element and battery manufacturing method)
Next, the electrode stack 100a is manufactured by laminating the belt-like negative electrode 10, the belt-like separator 20, the belt-like positive electrode 30, and the belt-like separator 20 in this order. Next, the electrode laminate 100a is wound. Thereby, the back surface (namely, strip | belt-shaped negative electrode 10) of the other part of the electrode laminated body 100a contacts the surface (namely, strip | belt-shaped separator 20) of a part with the electrode multilayer body 100a. Thereby, the winding element 100 is produced. Subsequently, the flat winding element 100 is produced by crushing the winding element 100. Next, the flat wound element 100 is inserted into an exterior body (for example, a laminate film) together with a non-aqueous electrolyte, and the exterior body is sealed to produce a lithium ion secondary battery. Note that, when sealing the exterior body, the terminals that are electrically connected to the current collectors are projected outside the exterior body.

Example 1
(Preparation of positive electrode)
A positive electrode mixture slurry was prepared by dissolving and dispersing lithium cobaltate, carbon black, and polyvinylidene fluoride (PVDF) in N-methylpyrrolidone in a mass ratio of solids of 96: 2: 2. Next, the positive electrode mixture slurry was applied to both sides of an aluminum foil current collector having a thickness of 12 μm and then dried. The positive electrode active material layer was produced by rolling the coating layer after drying. The total thickness of the current collector and the positive electrode active material layer was 120 μm. Subsequently, a strip-like positive electrode was obtained by welding an aluminum lead wire to the end portion of the electrode.

(Preparation of negative electrode)
Graphite, an aqueous dispersion of modified SBR fine particles, an aqueous dispersion of fluororesin-containing polymer fine particles obtained by polymerizing an acrylic resin in a PVDF aqueous dispersion, and a sodium salt of carboxymethyl cellulose in a mass ratio of 97: 1 A negative electrode mixture slurry was prepared by dissolving and dispersing in an aqueous solvent at a ratio of 1: 1. Next, this negative electrode mixture slurry was applied to both sides of a 10 μm thick copper foil current collector and then dried. The negative electrode active material layer was obtained by rolling the coating layer after drying. The total thickness of the current collector and the negative electrode active material layer was 120 μm. Then, the strip | belt-shaped negative electrode was obtained by welding a nickel lead wire to an edge part. In addition, when the average particle diameter of the fluororesin-containing fine particles used in this example was measured by a laser diffraction method, it was about 300 nm. Further, when the fluororesin-containing fine particles were observed with an SEM, they were spherical particles.

(Preparation of separator)
An aqueous dispersion of fluororesin-containing polymer fine particles obtained by polymerizing an acrylic resin in a PVDF aqueous dispersion to form a composite, and an aqueous dispersion of sodium ion of carboxymethyl cellulose and polyethylene ionomer fine particles of a binder as a solid content of 95: 1: 4 was used to dissolve and disperse in an aqueous solvent to prepare an adhesive layer mixture slurry. Next, this adhesive layer mixture slurry was applied to both sides of a 12 μm thick porous polyethylene separator film and dried to obtain a separator having a 3 μm thick adhesive layer formed on both sides. At this time, the volume ratio of the fluororesin-containing polymer fine particles to the polyethylene ionomer fine particles as a binder was about 18: 1.

(Production of wound element)
A negative electrode, a separator, a positive electrode, and a separator were laminated in this order, and this laminate was wound in the longitudinal direction using a winding core having a diameter of 3 cm. After fixing the end with tape, the winding core is removed, a cylindrical electrode winding element is sandwiched between two 3 cm thick metal plates, and held for 3 seconds, so that a flat electrode winding element Got.

(Evaluation of thickness increase rate)
The electrode winding element was measured for the rate of increase in thickness of the element before and after being left for 48 hours to obtain shape stability. The smaller the rate of increase in thickness, the better the shape stability (that is, because the distortion of the winding element is small), which is preferable. The thickness increase rate can be obtained by dividing the increase in the thickness of the element before and after being left for 48 hours by the thickness of the element before being left.

(Production of battery)
The electrode winding element was sealed under reduced pressure with an electrolyte so that two lead wires were exposed to a laminate film composed of three layers of polypropylene / aluminum / nylon, thereby producing a battery. As the electrolytic solution, a solution obtained by dissolving 1M LiPF ₆ in a solvent in which ethylene carbonate / ethyl methyl carbonate was mixed at a ratio of 3 to 7 (volume ratio) was used. The battery was sandwiched between two 3 cm thick metal plates heated to 80 ° C. and held for 5 minutes. This battery was charged with a constant current up to 4.4 V at 1/10 CA of the designed capacity (1 CA is a discharge rate for 1 hour), and then charged with a constant voltage until 4.4 V at 1/20 CA. Thereafter, constant current discharge was performed to 3.0 V at 1/2 CA. The capacity at this time was used as the initial discharge capacity, and a battery for life evaluation was produced.

(Life test)
The cycle test which repeats the charge process of 0.5CA, the constant current charge of 4.4V, the constant voltage charge to 0.05CA, and the discharge process of the constant current discharge of 0.5CA and 3.0V is performed for the manufactured battery. The reduction rate (maintenance rate) of the discharge capacity with respect to the initial discharge capacity after 100 cycles was measured to evaluate the life performance. The smaller the reduction rate of the discharge capacity, the better the life characteristics, which is preferable. The maintenance rate is obtained by dividing the discharge capacity after 100 cycles by the initial discharge capacity.

(Example 2)
In the production of the negative electrode, a negative electrode mixture slurry was prepared by dissolving and dispersing graphite, an aqueous dispersion of modified SBR fine particles, and a sodium salt of carboxymethyl cellulose in an aqueous solvent at a solid mass ratio of 97: 2: 1. In the production of separators, solid dispersion of fluororesin-containing polymer fine particle water dispersion, polymerized acrylic resin in PVDF water dispersion, sodium salt of carboxymethyl cellulose, and polyethylene ionomer fine particle binder as solid The same treatment as in Example 1 was performed except that the adhesive layer mixture slurry was prepared by dissolving and dispersing in a water solvent at a mass ratio of 89: 1: 10 min. The volume ratio of the fluororesin-containing polymer fine particles and the polyethylene ionomer fine particles as the binder in Example 2 was about 7: 1.

(Example 3)
In the production of separators, alumina powder having an average particle size of 0.5 μm, aqueous dispersion of fluororesin-containing polymer fine particles obtained by polymerizing acrylic resin in PVDF aqueous dispersion, sodium salt of carboxymethyl cellulose, binder The same treatment as in Example 1 was carried out except that an aqueous dispersion of polyethylene ionomer fine particles was dissolved and dispersed in an aqueous solvent at a mass ratio of solid content of 62: 27: 1: 10 to prepare an adhesive layer mixture slurry. went. The volume ratio of the fluororesin-containing polymer fine particles and the polyethylene ionomer fine particles as the binder in Example 3 was about 2: 1. In addition, the average particle diameter of alumina powder is 50% (D50) of volume accumulation measured by the laser diffraction method.

(Comparative Example 1)
In the manufacture of separators, a film in which PVDF is dissolved in N-methylpyrrolidone is applied to both sides of a porous polyethylene film having a thickness of 12 μm, and the film coated with the solution is immersed in water and then dried. An adhesive layer having a mesh-like porosity was formed on both sides. The thickness of the adhesive layer was 3 μm. In Comparative Example 1, the same treatment as in Example 1 was performed except that this film was used as a separator.

(Comparative Example 2)
In the production of separators, alumina powder having an average particle size of 0.5 μm, aqueous dispersion of fluororesin-containing polymer fine particles obtained by polymerizing acrylic resin in PVDF aqueous dispersion, sodium salt of carboxymethyl cellulose, binder The same treatment as in Example 1 was conducted except that an aqueous dispersion of polyethylene ionomer fine particles was dissolved and dispersed in an aqueous solvent at a solid mass ratio of 63: 18: 1: 18 to prepare an adhesive layer mixture slurry. went. The volume ratio of the fluororesin-containing polymer fine particles and the polyethylene ionomer fine particles as the binder in Comparative Example 2 was about 0.8: 1.

(Comparative Example 3)
In the production of the separator, the same treatment as in Example 2 was performed except that crosslinked polystyrene fine particles were used in place of the aqueous dispersion of fluororesin-containing polymer fine particles obtained by polymerizing and compounding an acrylic resin in PVDF aqueous dispersion. went.

(Evaluation)
The evaluation results are summarized in Table 1.

  In Examples 1 to 3, the thickness increase rate was small and the cycle life was good. In particular, in Example 3 containing inorganic particles, the cycle life was improved. On the other hand, Comparative Example 1 was inferior in shape stability after the production of the flat wound element because the fluororesin-containing polymer had a network structure instead of particles. That is, the winding element of Comparative Example 1 was distorted to a greater extent than the winding element of the example. Further, in Comparative Example 1, the cycle life is also deteriorated, and this is considered to be due to the distortion of the flat winding element. That is, the strip separator of Comparative Example 1 was less slippery than the strip separators of Examples 1 to 3, and the contact portions between the electrode laminates did not slip well when the winding element was flattened. As a result, the winding element was distorted. And in the comparative example 1, the battery is produced using the distorted winding element. For this reason, it is considered that the distance between the electrodes is not stable in the battery and the cycle life is reduced. Comparative Example 2 contains a larger volume of binder than the fluororesin-containing polymer, and the cycle capacity retention rate is inferior to that of the example. Comparative Example 3 containing particulate crosslinked polystyrene instead of the fluororesin-containing polymer is similarly inferior in cycle life characteristics.

  As described above, the winding element according to this embodiment is manufactured using a separator that is easy to handle in the manufacturing process. Further, the wound element can suppress the distortion and improve the cycle life of the nonaqueous electrolyte secondary battery.

  The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 100 Winding element 100a Laminated body 10 Strip | belt-shaped negative electrode 10a Negative electrode active material layer 10b Negative electrode collector 20 Band-shaped separator 20a Adhesion layer 20b-1 Fluorine resin containing fine particle 20b-2 Binder 20c Band-shaped porous film 30 Band-shaped positive electrode 30a Positive electrode active Material layer 30b Positive electrode current collector

Claims (7)

A strip-shaped positive electrode;
A strip-shaped negative electrode;
A band-shaped porous film disposed between the band-shaped positive electrode and the band-shaped negative electrode;
An adhesive formed on the surface of the band-shaped porous film, comprising: a fluororesin-containing fine particle; and a binder that supports the fluororesin-containing fine particle and has a total volume smaller than the total volume of the fluororesin-containing fine particle includes a layer, the,
The electrode winding element for a non-aqueous electrolyte secondary battery, wherein the binder contains a polyolefin resin . The strip-shaped negative electrode includes a negative electrode active material layer including a negative electrode active material and the fluororesin-containing fine particles,
The electrode winding element for a nonaqueous electrolyte secondary battery according to claim 1, wherein the adhesive layer is bound to the negative electrode active material layer. The electrode winding element for a non-aqueous electrolyte secondary battery according to claim 1, wherein the fluororesin-containing fine particles are spherical particles.   The electrode winding element for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the fluororesin includes polyvinylidene fluoride. The electrode winding element for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 4 , wherein the adhesive layer includes inorganic particles. A nonaqueous electrolyte secondary battery comprising the electrode winding element for a nonaqueous electrolyte secondary battery according to any one of claims 1 to 5 . An aqueous slurry containing fluororesin-containing microparticles and a binder that supports the fluororesin-containing microparticles and has a total volume smaller than the total volume of the fluororesin-containing microparticles is applied to the surface of the belt-like porous membrane. , the step of drying seen including,
The method for producing an electrode winding element for a nonaqueous electrolyte secondary battery, wherein the binder contains a polyolefin resin .

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