Non-aqueous electrolyte secondary battery and method for manufacturing non-aqueous electrolyte secondary battery

Abstract

The non-aqueous electrolyte secondary battery (1) has a wound electrode body (2) formed by winding a positive electrode (11) and a negative electrode (12) with a spacer between them, a non-aqueous electrolyte, and a battery case for containing the wound electrode body (2) and the non-aqueous electrolyte. The nitrogen concentration (A1) of the outermost peripheral surface (2a) of the wound electrode body (2) derived from a dinitrile compound and the nitrogen concentration (B) of the internal region of the wound electrode body (2) located inside the outermost peripheral surface (2a) derived from a dinitrile compound satisfy the relationship A1 > B.

Description

Technical Field

[0001] This invention relates to non-aqueous electrolyte secondary batteries and a method for manufacturing non-aqueous electrolyte secondary batteries. Background Technology

[0002] In recent years, non-aqueous electrolyte secondary batteries, which are high-output, high-energy-density rechargeable batteries, have been widely used. These batteries consist of an electrode body formed by winding a spacer between the positive and negative electrodes and a non-aqueous electrolyte, and allow lithium ions to move between the positive and negative electrodes for charging and discharging.

[0003] For example, patent documents 1 to 4 propose non-aqueous electrolyte secondary batteries using non-aqueous electrolytes containing nitrile compounds.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 07-176322

[0007] Patent Document 2: Japanese Patent Application Publication No. 2004-179146

[0008] Patent Document 3: Japanese Patent Application Publication No. 2010-073367

[0009] Patent Document 4: Japanese Patent Application Publication No. 2006-073513 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, if nitrile compounds are added to the non-aqueous electrolyte, although the dissolution of metal components from the electrode body and battery box into the non-aqueous electrolyte can be suppressed, there is a problem of increased initial resistance in the non-aqueous electrolyte secondary battery.

[0012] Therefore, the object of the present invention is to provide a non-aqueous electrolyte secondary battery and a method thereof capable of suppressing the dissolution of metals into the non-aqueous electrolyte and the increase in the initial resistance of the battery.

[0013] Methods for solving problems

[0014] As one aspect of the present invention, a non-aqueous electrolyte secondary battery includes a wound electrode body obtained by winding a positive electrode and a negative electrode with a spacer between them, a non-aqueous electrolyte, and a battery case for containing the wound electrode body and the non-aqueous electrolyte. The nitrogen element concentration A1 of the outermost peripheral surface of the wound electrode body, which originates from a dinitrile compound, and the nitrogen element concentration B of the inner region of the wound electrode body located inside the outermost peripheral surface, which originates from a dinitrile compound, satisfy the relationship A1 > B.

[0015] Furthermore, as one aspect of the present invention, a non-aqueous electrolyte secondary battery includes a wound electrode body obtained by winding a positive electrode and a negative electrode with a spacer between them, a non-aqueous electrolyte, and a battery case that contains the wound electrode body and the non-aqueous electrolyte. The nitrogen element concentration A2 of the inner wall of the battery case, which originates from a dinitrile compound, and the nitrogen element concentration B of the wound electrode body, which originates from a dinitrile compound and is located in the inner region of the inner side relative to the outermost peripheral surface, satisfy the relationship A2 > B.

[0016] In addition, as an aspect of the present invention, a method for manufacturing a non-aqueous electrolyte secondary battery includes a step of coating the outermost peripheral surface of a wound electrode body obtained by winding a positive electrode and a negative electrode with a spacer in between, and a step of housing the wound electrode body coated with the aforementioned dinitrile compound and a non-aqueous electrolyte in a battery case. The aforementioned dinitrile compound is a compound represented by the chemical formula NC-X-CN (where X is a C1 to C12 aliphatic hydrocarbon group (which may have heteroatoms) or a C6 to C20 aromatic hydrocarbon group (which may have heteroatoms)).

[0017] In addition, as an aspect of the present invention, a method for manufacturing a non-aqueous electrolyte secondary battery includes a step of coating the inner wall of a battery case with a dinitrile compound, and a step of accommodating a wound electrode body obtained by winding a positive electrode and a negative electrode with a spacer in between in the battery case coated with the aforementioned dinitrile compound. The aforementioned dinitrile compound is a compound represented by the chemical formula NC-X-CN (where X is a C1 to C12 aliphatic hydrocarbon group (which may have heteroatoms) or a C6 to C20 aromatic hydrocarbon group (which may have heteroatoms)).

[0018] Invention Effects

[0019] According to one aspect of the present invention, a non-aqueous electrolyte secondary battery and a method thereof can be provided that can suppress the dissolution of metals into the non-aqueous electrolyte and the increase in the initial resistance of the battery. Attached Figure Description

[0020] Figure 1 This is a perspective view showing the appearance of the non-aqueous electrolyte secondary battery according to the embodiment.

[0021] Figure 2 It is along Figure 1 A cross-sectional view of a non-aqueous electrolyte secondary battery with line L1-L1. Detailed Implementation

[0022] Hereinafter, an example of a non-aqueous electrolyte secondary battery as an embodiment of the present invention will be described. The accompanying drawings, which are shown schematically in the following description of the embodiments, may sometimes differ from reality in terms of the dimensions, proportions, etc., of the constituent elements depicted.

[0023] Figure 1 This is a perspective view showing the appearance of the non-aqueous electrolyte secondary battery according to the embodiment. Figure 2 It is along Figure 1 A cross-sectional view of a non-aqueous electrolyte secondary battery with line L1-L1.

[0024] The non-aqueous electrolyte secondary battery 1 of this embodiment includes an electrode body 2, a non-aqueous electrolyte (not shown), and a battery case 3.

[0025] The battery case 3 houses the electrode body 2, non-aqueous electrolyte, etc., and includes, for example, a case body 5 with an opening and a sealing body 6 that seals the opening of the case body 5. The case body 5 is, for example, a bottomed cylindrical metal outer packaging can, with an inwardly protruding groove 5c formed along the circumferential direction on the upper part of the case body 5. The sealing body 6 is supported by the groove 5c and seals the opening of the case body 5. To ensure the airtightness of the battery interior, it is desirable to provide a gasket between the case body 5 and the sealing body 6.

[0026] Figure 2 The electrode body 2 shown is a wound electrode body (hereinafter referred to as wound electrode body 2) obtained by winding the positive electrode 11 and the negative electrode 12 together with a spacer in between. However, Figure 2 The spacer, not shown, is disposed between the positive electrode 11 and the negative electrode 12. Figure 2 The wound electrode body 2 shown is cylindrical, but the shape of the wound electrode body 2 is not limited to this, and it can also be flat, etc.

[0027] The negative electrode 12 includes a negative electrode current collector 14 and a negative electrode active material layer 16 disposed on the negative electrode current collector 14. It should be noted that the negative electrode active material layer 16 is preferably disposed on both sides of the negative electrode current collector 14.

[0028] Furthermore, the negative electrode 12 has exposed portions 14a and 14b on the negative electrode current collector 14 where the negative electrode active material layer 16 is not disposed, but the negative electrode current collector 14 is exposed. For example... Figure 2 As shown, the exposed portion 14a of the negative current collector is located on the innermost circumference of the electrode body 2, and the exposed portion 14b of the negative current collector is located on the outermost circumference of the electrode body 2. For Figure 2Regarding the radially outer surface (outer surface) 15 of the electrode body 2 of the exposed negative current collector portion 14b shown, the negative current collector 14 is exposed for a length of at least one circumference around the outer periphery of the electrode body 2, forming the outermost peripheral surface 2a of the electrode body 2. It should be noted that the elements forming the outermost peripheral surface 2a of the electrode body 2 are determined according to the design of the electrode body 2. For example, if the negative active material layer 16 extends to the outermost periphery of the electrode body 2, then the surface of the extended portion of the negative active material layer 16 and the outer surface 15 of the exposed negative current collector portion 14b become the outermost peripheral surface 2a of the electrode body 2. Furthermore, if the outermost periphery of the electrode body 2 is designed as a spacer, then the radially outer surface of the electrode body 2 at the outermost periphery of the spacer becomes the outermost peripheral surface 2a of the electrode body 2. Additionally, if the outermost periphery of the electrode body 2 is designed as a positive electrode 11, then the radially outer surface of the electrode body 2 at the outermost periphery of the positive electrode 11 becomes the outermost peripheral surface 2a of the electrode body 2.

[0029] In this embodiment, the outer surface 15 of the exposed negative current collector 14b becomes the outermost peripheral surface 2a of the electrode body 2. In this case, it is desirable for the outer surface 15 of the exposed negative current collector 14b to contact the inner wall of the housing body 5. Thus, the housing body 5 can be configured as the negative terminal. Alternatively, in this embodiment, instead of the structure where the outer surface 15 of the exposed negative current collector 14b contacts the inner wall of the housing body 5, or in combination with it, one end of the negative electrode 12 (e.g., the exposed negative current collector 14a) is connected to the negative terminal connector, and the other end is connected to the housing body 5 (e.g., the bottom). Using this structure, the housing body 5 can be configured as the negative terminal.

[0030] In manufacturing a non-aqueous electrolyte secondary battery, as described later, a dinitrile-containing compound is coated on the outermost peripheral surface 2a of the electrode body 2, or a dinitrile-containing compound is coated on the inner wall of the battery case 3. Therefore, in the non-aqueous electrolyte secondary battery 1 of this embodiment, the outermost peripheral surface 2a of the electrode body 2 (… Figure 2The nitrogen concentration A1 originating from dinitrile compounds in the outer surface 15) of the exposed portion 14b of the negative electrode current collector and the nitrogen concentration B originating from dinitrile compounds in the internal region located inside the outermost peripheral surface 2a of the electrode body 2 satisfy the relationship A1 > B, and / or the nitrogen concentration A2 originating from dinitrile compounds in the inner wall of the battery case 3 and the nitrogen concentration B originating from dinitrile compounds in the internal region located inside the outermost peripheral surface 2a of the electrode body 2 satisfy the relationship A2 > B. The internal region located inside the outermost peripheral surface 2a of the electrode body 2 refers to the region radially inward of the outermost peripheral surface 2a of the electrode body 2. Furthermore, the term "originating from dinitrile compounds" refers to the dinitrile compound itself or the decomposition products of the dinitrile compound resulting from charge-discharge reactions, etc. That is, in this embodiment, compared with the inner region located inside the outermost peripheral surface 2a of the electrode body 2, the dinitrile compound and the decomposition products of the dinitrile compound are more present on the outermost peripheral surface 2a of the electrode body 2 and / or the inner wall of the battery box 3.

[0031] If a dinitrile compound is added to the non-aqueous electrolyte as in the conventional manner, it decomposes during charging and discharging, forming a film of the decomposition products of the dinitrile compound on the outermost peripheral surface 2a of the electrode body 2, the internal region, and the inner wall of the battery case 3. This film can suppress the dissolution of metal components from the outermost peripheral surface 2a of the electrode body 2 and the battery case 3 into the non-aqueous electrolyte. By suppressing this dissolution of metals into the non-aqueous electrolyte, effects such as suppressing the reduction of charge-discharge cycle characteristics can be achieved. However, since the film formed in the negative electrode active material layer and the like in the internal region of the electrode body 2 is resistive, the initial resistance of the battery increases.

[0032] On the other hand, in the case where A1, A2, and B satisfy the relationships A1 > B and / or A2 > B, as in the non-aqueous electrolyte secondary battery of this embodiment, a state is formed in which there is a large amount of film containing the decomposition products of dinitrile compounds formed on the outermost peripheral surface 2a of the electrode body 2 and the inner wall of the battery case 3, and a small amount of film containing the decomposition products of dinitrile compounds formed in the internal region of the electrode body 2. If this state is achieved, the dissolution of metal components from the outermost peripheral surface 2a of the electrode body 2 and the battery case 3 into the non-aqueous electrolyte can be suppressed. Furthermore, since it is difficult for a film containing resistive components to form in the negative electrode active material layer or the like in the internal region of the electrode body 2, the increase in the initial resistance of the battery can also be suppressed.

[0033] Preferably, the ratio (B / A1) of the nitrogen concentration B originating from the dinitrile compound in the internal region inside the outermost peripheral surface 2a of the electrode body 2 to the nitrogen concentration A1 originating from the dinitrile compound in the innermost peripheral surface 2a of the electrode body 2 is 0.5 or less. Furthermore, it is preferable that the ratio (B / A2) of the nitrogen concentration B originating from the dinitrile compound in the internal region inside the outermost peripheral surface 2a of the electrode body 2 to the nitrogen concentration A2 originating from the dinitrile compound on the inner wall of the battery case 3 is 0.5 or less. By satisfying the above range, compared to cases where the above range is not satisfied, it is possible to suppress the dissolution of metal into the non-aqueous electrolyte or suppress the increase in the initial resistance of the battery.

[0034] For the nitrogen concentration A1 originating from dinitrile compounds on the outermost peripheral surface 2a of electrode 2, or the nitrogen concentration A2 originating from dinitrile compounds on the inner wall of battery case 3, considering factors such as suppressing the dissolution of metal into the non-aqueous electrolyte, the concentration is preferably in the range of 2 to 20 atomic percent, more preferably in the range of 2 to 10 atomic percent. Furthermore, for the nitrogen concentration B originating from dinitrile compounds in the internal region located inside the outermost peripheral surface 2a of electrode 2, considering factors such as suppressing the increase in the initial resistance of the battery, the concentration is preferably 1 atomic percent or less, preferably zero. The method for determining the nitrogen concentration originating from dinitrile compounds is described in Example 1.

[0035] The negative current collector 14 may be made of a foil of a metal such as copper that is stable in the potential range of the negative electrode 12, or a film of the metal disposed on the surface.

[0036] The negative electrode active material layer 16 may include, for example, negative electrode active material, binder material, etc.

[0037] As a negative electrode active material, there are no particular limitations as long as the material can adsorb and release lithium ions. Examples include carbon materials such as graphite, non-graphitized carbon, readily graphitized carbon, fibrous carbon, coke, and carbon black; metals alloyed with Li such as Si and Sn; metal compounds containing Si and Sn; and lithium-titanium composite oxides. From the perspective of achieving high battery capacity, the negative electrode active material may include carbon and Si materials, with the Si compound preferably accounting for 5.5% or more of the total mass of the negative electrode active material. Examples of Si materials include SiO₂. x (0.5≤x≤1.6) etc.

[0038] Examples of adhesives include fluorinated resins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, styrene-butadiene rubber (SBR), acrylonitrile-butadiene (NBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (PAA-Na, PAA-K, etc., and also partially neutralized salts), and polyvinyl alcohol (PVA). These can be used individually or in combination of two or more.

[0039] The negative electrode 12 can be made, for example, by preparing a negative electrode slurry containing negative electrode active material, binder material, etc., coating the negative electrode slurry onto the negative electrode current collector 14 and drying it to form a negative electrode active material layer 16, and then calendering the negative electrode active material layer.

[0040] The positive electrode 11 includes a positive current collector 18 and a positive active material layer 20 disposed on the positive current collector 18. For example... Figure 2 As shown, the positive electrode active material layer 20 is preferably disposed on both sides of the positive electrode current collector 18. It should be noted that, although the explanation in the figure is omitted, the positive electrode 11 has a positive electrode current collector exposed portion on the positive electrode current collector 18, where the positive electrode active material layer 20 is not disposed, but rather the positive electrode current collector 18 is exposed. Furthermore, one end of the positive electrode current collector exposed portion is connected to the positive electrode connector, and the other end is connected to the inner wall of the sealing body 6. Thus, the sealing body 6 becomes the terminal of the positive electrode 11.

[0041] A foil of a metal that is stable in the potential range of the positive electrode 11, such as aluminum, or a film of the metal disposed on the surface, can be used as the positive electrode current collector 18.

[0042] The positive electrode active material layer 20 may include, for example, a positive electrode active material, a binder, a conductive material, etc.

[0043] Examples of lithium transition metal oxides containing transition metal elements such as Co, Mn, and Ni can be cited as positive electrode active materials. For example, Li0.05 is a lithium transition metal oxide. x CoO2, Li x NiO2, Li x MnO2, Li x Co y Ni l-y O2, Li x Co y M l-y O z Li x Ni l- y M y O z Li x Mn2O4, Li x Mn2-y M y O4, LiMPO4, Li2MPO4F (M: at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3). They can be used individually or in combination. From the perspective of achieving high battery capacity, the positive electrode active material preferably contains Li. x NiO2, Li x Co y Ni l-y O2, LixNi l-y M y O z (M: at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3) and other lithium nickel composite oxides.

[0044] Conductive materials include, for example, carbon black (CB), acetylene black (AB), Ketjen black, and carbon-based particles such as graphite. They can be used alone or in combination of two or more.

[0045] Examples of adhesive materials include fluorinated resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. They can be used alone or in combination of two or more.

[0046] The positive electrode 11 can be manufactured, for example, by coating a positive electrode slurry containing positive electrode active material, binder material, conductive material, etc. onto the positive electrode current collector 18 and drying it to form a positive electrode active material layer 20, and then calendering the positive electrode active material layer 20.

[0047] For example, porous sheets with ion permeability and insulation properties can be used as spacers. Specific examples of porous sheets include microporous films, woven fabrics, and nonwoven fabrics. Suitable materials for spacers include olefin resins such as polyethylene and polypropylene, and cellulose. Spacers can be laminates having cellulose fiber layers and thermoplastic resin fiber layers such as olefin resins. Alternatively, multilayer spacers containing polyethylene and polypropylene layers can also be used, as well as components with aromatic polyamide resins, ceramics, or other materials coated on the surface of the spacer.

[0048] The non-aqueous electrolyte contains an electrolyte salt and a non-aqueous solvent to dissolve the electrolyte salt. The electrolyte salt is preferably a lithium salt. Examples of lithium salts include LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiCF3SO3, LiCF3CO2, Li(P(C2O4)F4), and LiPF6. 6-x (C n F 2n+1 ) x (1 < x < 6, n is 1 or 2), LiB 10 Cl 1o LiCl, LiBr, LiI, lithium chloroborane, lower aliphatic carboxylic acids, Li₂B₄O₇, Li(B(C₂O₄)F₂) and other borates, LiN(SO₂CF₃)₂, LiN(C₁F₂) 21+ 1SO2)(C m F 2m+1 Imidamine salts such as SO2 (where m is an integer greater than or equal to 0) are used. Lithium salts can be used alone or in combination. Among these, LiPF6 is preferred from the viewpoint of ionic conductivity and electrochemical stability. The preferred concentration of the lithium salt is 0.8–1.8 mol per 1 L of non-aqueous solvent.

[0049] For example, esters, ethers, nitrile solvents such as acetonitrile, amide solvents such as dimethylformamide, and mixtures of two or more of these solvents can be used as non-aqueous solvents. Non-aqueous solvents may contain halogen substitutes in which at least a portion of the hydrogen atoms of these solvents are replaced by halogen atoms such as fluorine.

[0050] Examples of the aforementioned esters include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate; chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate; cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone; and chain carboxylic acid esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate.

[0051] Examples of the aforementioned ethers include 1,3-dioxane, 4-methyl-1,3-dioxane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-epoxybutane, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-eucalyptol, crown ethers and other cyclic ethers, 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, and dihexyl ether. Ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether, o-dimethoxybenzene, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and other chain ethers.

[0052] Fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorochain carbonates, and fluorochain carboxylic acid esters such as methyl fluoropropionate (FMP) are preferred as the above-mentioned halogen substitutes.

[0053] The manufacturing method of the non-aqueous electrolyte secondary battery of this embodiment includes: the outermost peripheral surface 2a of a wound electrode body 2 obtained by winding a positive electrode 11 and a negative electrode 12 with a spacer in between. Figure 2 The manufacturing method of this embodiment includes a process of coating the outer surface 15 (of the exposed negative electrode current collector 14b) with a dinitrile-based compound, and a process of housing the wound electrode body 2 coated with the dinitrile-based compound and the non-aqueous electrolyte in the battery case 3. In this embodiment, before housing the wound electrode body 2 coated with the dinitrile-based compound and the non-aqueous electrolyte in the battery case 3, a process of coating the inner wall of the battery case 3 with the dinitrile-based compound may be included. Subsequently, by charging and discharging the non-aqueous electrolyte secondary battery obtained using the manufacturing method of this embodiment, a non-aqueous electrolyte secondary battery can be obtained in which the nitrogen concentration A1 derived from the dinitrile-based compound on the outermost peripheral surface 2a of the wound electrode body 2 and the nitrogen concentration B derived from the dinitrile-based compound in the inner region of the wound electrode body 2 relative to the outermost peripheral surface 2a satisfy the relationship A1 > B.

[0054] The manufacturing method of the non-aqueous electrolyte secondary battery of this embodiment includes: a step of coating the inner wall of the battery case 3 with a dinitrile-based compound, and a step of accommodating a wound electrode body 2, which is obtained by winding a positive electrode 11 and a negative electrode 12 with a spacer in between, in the battery case 3 coated with the dinitrile-based compound, and a non-aqueous electrolyte. In the manufacturing method of this embodiment, before accommodating the wound electrode body 2 and the non-aqueous electrolyte in the battery case 3 coated with the dinitrile-based compound, it is possible to have a coating applied to the outermost peripheral surface 2a of the wound electrode body 2. Figure 2The process involves coating the outer surface 15) of the exposed negative electrode current collector 14b with a dinitrile compound. By charging and discharging the non-aqueous electrolyte secondary battery obtained using the manufacturing method of this embodiment, a non-aqueous electrolyte secondary battery can be obtained in which the nitrogen concentration A2 derived from the dinitrile compound on the inner wall of the battery case 3 and the nitrogen concentration B derived from the dinitrile compound in the internal region of the wound electrode body 2 located inside the outermost peripheral surface 2a satisfy the relationship A2 > B.

[0055] In the above manufacturing method, it is preferable not to coat the inner region of the wound electrode body 2 that is inside the outermost peripheral surface 2a with a dinitrile compound. However, if the inner region of the wound electrode body 2 that is inside the outermost peripheral surface 2a is coated with a dinitrile compound, it is preferable to coat it with a smaller amount of dinitrile compound than the amount coated on the outermost peripheral surface 2a of the wound electrode body 2.

[0056] In the above manufacturing method, when coating the inner wall of the battery case 3 with a dinitrile compound, the dinitrile compound can be coated on both the inner wall of the case body 5 and the inner wall of the sealing body 6, preferably at least on the inner wall of the case body 5. This is because the metal of the case body 5, which is in contact with the non-aqueous electrolyte, is easily dissolved.

[0057] The dinitrile compound used in the above manufacturing method is not particularly limited as long as it has two nitrile groups in one molecule. However, for example, from the perspective of effectively suppressing metal dissolution, it is preferable to include a compound represented by the chemical formula NC-X-CN (where X is a C1-C12 aliphatic hydrocarbon group (which may have heteroatoms) or a C6-C20 aromatic hydrocarbon group (which may have heteroatoms)). The aliphatic hydrocarbon group can be either chain-like or cyclic, and the chain-like aliphatic hydrocarbon group can be either straight-chain or branched.

[0058] For the aliphatic hydrocarbon groups, the carbon number is preferably in the range of C1 to C12, more preferably in the range of C2 to C10, for example, from the perspective of effectively suppressing the dissolution of metals into non-aqueous electrolytes. Furthermore, for the aromatic hydrocarbon groups, the carbon number is preferably in the range of C6 to C20, more preferably in the range of C8 to C18, for example, from the perspective of effectively suppressing the dissolution of metals into non-aqueous electrolytes.

[0059] Examples of aliphatic hydrocarbon groups include alkyl, alkenyl, and alkynyl groups. Examples of aromatic hydrocarbon groups include phenyl, tolyl, benzyl, and phenethyl groups.

[0060] Aliphatic and aromatic hydrocarbon groups can have heteroatoms that substitute for hydrogen or carbon atoms. There are no particular limitations on the heteroatoms; examples include boron, silicon, nitrogen, sulfur, fluorine, chlorine, and bromine.

[0061] Examples of dinitrile-containing compounds include adiponitrile, succinic anionyl nitrile, glutaronitrile, malononitrile, heptanilide, octanilide, nonadionitrile, decanadionitrile, undecanedionitrile, dodecanedionitrile, fumaric acid, 3-hexenedionitrile, maleic acid, 1,12-dicyanododecane, tetramethylsuccinic anionyl nitrile, 2-methylglutaronitrile, 2,4-dimethylglutaronitrile, 2,2,4,4-tetramethylglutaronitrile, 1,4-dicyanopentane, 2,5-dimethyl-2,5-hexanedicarboxynitrile, 2,6-dicyanoheptane, 2,7-dicyanoctane, 2,8-dicyanonane, 1,6-dicyanodecane, methylmalononitrile, ethylmalononitrile, isopropylmalononitrile, tert-butylmalononitrile, methylsuccinic anionyl nitrile, 2,2-dimethylsuccinic anionyl nitrile, 2,3-dimethylsuccinic anionyl nitrile, trimethylbutanediol, etc. Dinitrile, tetramethylbutadionitrile, 3,3'-oxodipropionitrile, 3,3'-thiodipropionitrile, 3,3'-[1,2-ethylenedioxydipropionitrile]dipropionitrile, 3,3'-bis(ethylenedioxy)dipropionitrile, phthalonitrile, isophthalonitrile, terephthalonitrile, 1,2-dicyanocyclobutane, 1,1-dicyanoethyl acetate, 2,3-dicyanohydroquinone, 4,5-dicyanoimidazolium, 2,4-dicyano-3-methylpentanediamide, 9-dicyanomethylene-2,4,7-trinitrofluorene, 2,6-dicyanotoluene, etc. These can be used alone or in combination of two or more.

[0062] Example

[0063] The present invention will be further illustrated below with reference to embodiments; however, the present invention is not limited to these embodiments.

[0064] <Example>

[0065] [The production of the positive electrode]

[0066] Lithium nickel cobalt oxide (LiNi) containing aluminum is used. 0.88 Co 0.09 Al 0.03 O2) was used as the positive electrode active material. 100 parts by mass of the above-mentioned positive electrode active material, 1 part by mass of acetylene black, and 0.9 parts by mass of polyvinylidene fluoride were mixed in N-methyl-2-pyrrolidone (NMP) solvent to prepare a positive electrode slurry. This slurry was coated on both sides of a 15 μm thick aluminum foil. After drying the coating, it was calendered using calendering rollers, thereby producing a positive electrode with positive electrode active material layers formed on both sides of the positive electrode current collector. The produced positive electrode was cut to a size of 57.6 mm wide and 679 mm long for use.

[0067] [Making the negative electrode]

[0068] A mixture of 95 parts by mass of graphite powder and 5 parts by mass of Si oxide was used as the negative electrode active material. A negative electrode slurry was prepared by dispersing 100 parts by mass of the negative electrode active material, 1 part by mass of carboxymethyl cellulose (CMC), and 1 part by mass of styrene-butadiene rubber (SBR) in water. This slurry was coated on both sides of an 8 μm thick copper foil. After drying the coating, it was calendered using calendering rollers to create a negative electrode with negative electrode active material layers formed on both sides of the negative electrode current collector. The fabricated negative electrode was then cut to a size of 58.6 mm wide and 662 mm long for use.

[0069] [Preparation of non-aqueous electrolytes]

[0070] LiPF6 was dissolved in a non-aqueous solvent containing ethylene carbonate (EC), methyl ethyl carbonate (MEC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75, at a concentration of 1.4 mol / L, and then 3% by mass of ethylene carbonate (VC) was added.

[0071] [Fabrication of Non-Aqueous Electrolyte Secondary Batteries]

[0072] An aluminum positive electrode lead is installed in the positive current collector, and a nickel-copper-nickel negative electrode lead is installed in the negative current collector. A polyethylene spacer is sandwiched between the positive and negative electrodes, and the electrodes are wound together to create a wound electrode body. Adiponitrile at a mass of 0.1% relative to the injected non-aqueous electrolyte is coated onto the exposed portion of the negative current collector, which forms the outermost circumference of the electrode body, using a brush coating method. Insulating plates are placed above and below the wound electrode body. The negative electrode lead is soldered to the main body of the casing, and the positive electrode lead is soldered to the sealing body. The electrode body is then housed within the casing body. Afterward, non-aqueous electrolyte is injected into the casing body under reduced pressure. The open end of the casing body is then riveted with a gasketed sealing body, thus creating a non-aqueous electrolyte secondary battery. The battery capacity is 3300mAh.

[0073] <Comparative Example 1>

[0074] Except that adiponitrile was not coated on the outer peripheral surface of the wound electrode body, a non-aqueous electrolyte secondary battery was fabricated in the same manner as in the example.

[0075] <Comparative Example 2>

[0076] Except that adiponitrile was not coated on the outer peripheral surface of the wound electrode body and 0.1% by mass of adiponitrile was added to the non-aqueous electrolyte of the example, a non-aqueous electrolyte secondary battery was made in the same manner as in the example.

[0077] <Comparative Example 3>

[0078] Except that the outer peripheral surface of the wound electrode body was not coated with adiponitrile and 1% by mass of adiponitrile was added to the non-aqueous electrolyte of the example, a non-aqueous electrolyte secondary battery was made in the same manner as in the example.

[0079] [Method for determining the concentration of dissolved Fe]

[0080] After placing the non-aqueous electrolyte secondary batteries of the examples and comparative examples at 25°C for 24 hours, holes were made in the battery case, and the non-aqueous electrolyte inside the secondary batteries was extracted using a centrifuge. Nitric acid was added to the extracted non-aqueous electrolyte for dilution, and the resulting non-aqueous electrolyte was used as the test sample. The amount of Fe (μg) in the test sample was determined using an inductively coupled plasma (ICP) luminescence spectrophotometer. The amount of Fe per unit mass of non-aqueous electrolyte (μg / g) was defined as the leached Fe concentration. The lower this value, the more suppressed the dissolution of metal into the non-aqueous electrolyte.

[0081] [Determination of initial resistance]

[0082] At an ambient temperature of 25°C, the non-aqueous electrolyte secondary batteries of the examples and comparative examples were charged to 4.2V with a constant current of 990mA (0.3It), and then charged with a constant voltage of 4.2V at a constant voltage with a termination current of 66mA to adjust the state of charge (SOC) to 100%. Subsequently, at an ambient temperature of 25°C, the AC impedance was measured, and the resistance value at 1kHz was set as the initial resistance.

[0083] [Determination of nitrogen concentration derived from dinitrile compounds]

[0084] Each battery with its initial resistance measured was subjected to constant current discharge at 1650 mA (0.5 It) to 3.0 V at an ambient temperature of 25°C. Then, under an argon atmosphere, each battery was disassembled, and the negative electrode current collector, which forms the outermost circumferential surface of the electrode body, was cut out. Additionally, the negative electrode on the innermost circumferential surface of the electrode body (the center of the electrode core) was cut out. These were then introduced into an X-ray photoelectron analysis (ESCA) device without contact with the atmosphere to measure the nitrogen concentration. The measured nitrogen concentration at this time is the nitrogen concentration in the film containing decomposition products such as dinitrile compounds. The nitrogen concentration on the outermost circumferential surface of the electrode body is defined as A, representing the nitrogen concentration originating from dinitrile compounds on the outermost circumferential surface of the electrode body. The nitrogen concentration at the negative electrode on the innermost circumferential surface of the electrode body is defined as B, representing the nitrogen concentration originating from dinitrile compounds in the internal region of the electrode body. The nitrogen concentration ratio (B / A) was calculated. It should be noted that for determining the nitrogen concentration in the internal region of the electrode, if it is known that the battery does not contain dinitrile compounds, any one location within the internal region of the electrode can be designated as the measurement site. However, if it is unclear whether the battery contains dinitrile compounds, multiple locations (preferably 10-15 locations) within the internal region of the electrode should be designated as measurement sites. Furthermore, the highest nitrogen concentration among all measurement sites within the internal region of the electrode should be used.

[0085] Table 1 summarizes the results of leached Fe concentration, initial resistance, and nitrogen element concentration ratio (B / A) for the examples and comparative examples.

[0086] [Table 1]

[0087]

[0088] As shown in Table 1, the initial resistance of the embodiments is the same as that of Comparative Example 1 and lower than that of Comparative Examples 2 and 3. Furthermore, the dissolved Fe concentration of the embodiments is lower than that of Comparative Examples 1 to 3. Therefore, it can be said that, according to the embodiments, the dissolution of metal into the non-aqueous electrolyte can be suppressed, and the initial resistance of the battery can also be suppressed.

[0089] Explanation of reference numerals in the attached figures

[0090] 1 Non-aqueous electrolyte secondary battery, 2 Electrode body (wound electrode body), 2a Outermost circumferential surface, 3 Battery box, 5 Box body, 5c Tank, 6 Sealing body, 11 Positive electrode, 12 Negative electrode, 14 Negative electrode current collector, 14a, 14b Exposed parts of negative electrode current collector, 15 Outer surface, 16 Negative electrode active material layer, 18 Positive electrode current collector, 20 Positive electrode active material layer.

Claims

1. A non-aqueous electrolyte secondary battery, It comprises a wound electrode body formed by winding a positive electrode and a negative electrode with a spacer between them, a non-aqueous electrolyte, and a battery case for containing the wound electrode body and the non-aqueous electrolyte. The nitrogen concentration A1 derived from dinitrile compounds on the outermost peripheral surface of the wound electrode body and the nitrogen concentration B derived from dinitrile compounds in the inner region of the wound electrode body relative to the outermost peripheral surface satisfy the relationship A1 > B. The dinitrile-containing compound is a compound represented by the chemical formula NC-X-CN, where X is an aliphatic hydrocarbon group of C1 to C12 or an aromatic hydrocarbon group of C6 to C20, and the aliphatic hydrocarbon group and the aromatic hydrocarbon group may or may not have heteroatoms.

2. A non-aqueous electrolyte secondary battery, It comprises a wound electrode body formed by winding a positive electrode and a negative electrode with a spacer between them, a non-aqueous electrolyte, and a battery case for containing the wound electrode body and the non-aqueous electrolyte. The nitrogen concentration A2 derived from dinitrile compounds on the inner wall of the battery box and the nitrogen concentration B derived from dinitrile compounds in the inner region of the wound electrode body relative to the outermost peripheral surface satisfy the relationship A2 > B. The dinitrile-containing compound is a compound represented by the chemical formula NC-X-CN, where X is an aliphatic hydrocarbon group of C1 to C12 or an aromatic hydrocarbon group of C6 to C20, and the aliphatic hydrocarbon group and the aromatic hydrocarbon group may or may not have heteroatoms.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The ratio of the nitrogen concentration B in the inner region of the wound electrode to the nitrogen concentration A1 in the outermost peripheral surface of the wound electrode, i.e., B / A1, is 0.5 or less.

4. The non-aqueous electrolyte secondary battery according to claim 2, wherein, The ratio of the nitrogen concentration B in the internal region of the wound electrode to the nitrogen concentration A2 in the inner wall of the battery box, i.e., B / A2, is less than 0.

5.

5. The method for manufacturing the non-aqueous electrolyte secondary battery according to claim 1, The manufacturing method has the following characteristics: The process of coating the outermost circumferential surface of a wound electrode body, obtained by winding the positive and negative electrodes with a spacer between them, and... The process of housing the wound electrode body coated with the dinitrile compound and the non-aqueous electrolyte in a battery case. The dinitrile-containing compound is a compound represented by the chemical formula NC-X-CN, where X is an aliphatic hydrocarbon group of C1 to C12 or an aromatic hydrocarbon group of C6 to C20, and the aliphatic hydrocarbon group and the aromatic hydrocarbon group may or may not have heteroatoms.

6. The method for manufacturing the non-aqueous electrolyte secondary battery according to claim 2, The manufacturing method has the following characteristics: The process of coating the inner wall of the battery box with a dinitrile compound, and The process of housing a wound electrode body, which is formed by winding a positive electrode and a negative electrode with a spacer between them, and a non-aqueous electrolyte in a battery case coated with the aforementioned dinitrile compound. The dinitrile-containing compound is a compound represented by the chemical formula NC-X-CN, where X is an aliphatic hydrocarbon group of C1 to C12 or an aromatic hydrocarbon group of C6 to C20, and the aliphatic hydrocarbon group and the aromatic hydrocarbon group may or may not have heteroatoms.

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