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

Abstract

Provided is a nonaqueous electrolyte secondary battery capable of inhibiting an increase in initial resistance when an isocyanate group-containing compound is added to a nonaqueous electrolyte. A nonaqueous electrolyte secondary battery of one embodiment of the present application includes a jelly-roll type electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, a nonaqueous electrolyte, and a battery case in which the jelly-roll type electrode body and the nonaqueous electrolyte are accommodated, and the concentration A1 of nitrogen elements from an isocyanate group-containing compound at the outermost circumferential surface of the jelly-roll type electrode body and the concentration B of nitrogen elements from the isocyanate group-containing compound in an internal region inside the outermost circumferential surface 2a of the jelly-roll type electrode body satisfy the relation 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 and high-energy-density rechargeable batteries, have been widely used. They have a positive electrode, a negative electrode, 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 Document 1 proposes a non-aqueous electrolyte secondary battery using a non-aqueous electrolyte containing a diisocyanate compound. According to Patent Document 1, by using a non-aqueous electrolyte containing a diisocyanate compound, the amount of gas generated during high-temperature storage is suppressed, the amount of battery expansion is suppressed, and the reduction in charge-discharge cycle characteristics is suppressed.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2007-242411 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, adding isocyanate-containing compounds to non-aqueous electrolytes can suppress the decrease in battery charge-discharge cycle characteristics, but on the other hand, there is a problem of initial increase in battery resistance.

[0009] Therefore, the object of the present invention is to provide a non-aqueous electrolyte secondary battery and a method thereof capable of suppressing the initial resistance increase when an isocyanate-containing compound is added to a non-aqueous electrolyte.

[0010] means for solving problems

[0011] As one aspect of the present invention, a non-aqueous electrolyte secondary battery 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 casing for housing the wound electrode body and the non-aqueous electrolyte, wherein the nitrogen concentration A1 of the isocyanate-containing compound on the outermost peripheral surface of the wound electrode body and the nitrogen concentration B of the isocyanate-containing compound in the internal region that is inside the outermost peripheral surface of the wound electrode body satisfy the relationship A1 > B.

[0012] Furthermore, as one aspect of the present invention, a non-aqueous electrolyte secondary battery includes: 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 casing that houses the wound electrode body and the non-aqueous electrolyte. The nitrogen concentration A2 from the isocyanate-containing compound in the inner wall of the battery casing and the nitrogen concentration B from the isocyanate-containing compound in the inner region that is inside the outermost peripheral surface of the wound electrode body satisfy the relationship A2 > B.

[0013] In addition, a method for manufacturing a non-aqueous electrolyte secondary battery according to one aspect of the present invention includes: a step of coating the outermost peripheral surface of a wound electrode body formed by winding a positive electrode and a negative electrode with a spacer between them with a spacer; and a step of housing the wound electrode body coated with the above-mentioned isocyanate-containing compound and the non-aqueous electrolyte in a battery casing, wherein the above-mentioned isocyanate-containing compound is a compound represented by chemical formula 1: XN=C=O or chemical formula 2: O=C=NXN=C=O (where X is: an aliphatic hydrocarbon group of C1 to C12, optionally having heteroatoms; or an aromatic hydrocarbon group of C6 to C20, optionally having heteroatoms).

[0014] Furthermore, as an aspect of the present invention, a method for manufacturing a non-aqueous electrolyte secondary battery includes: a step of coating an isocyanate-based compound onto the inner wall of a battery casing; and a step of housing a wound electrode body formed by winding a positive electrode and a negative electrode with a spacer in the battery casing coated with the isocyanate-based compound, wherein the isocyanate-based compound is a compound represented by chemical formula 1: XN=C=O or chemical formula 2: O=C=NXN=C=O (where X is: an aliphatic hydrocarbon group of C1 to C12, optionally having heteroatoms; or an aromatic hydrocarbon group of C6 to C20, optionally having heteroatoms).

[0015] Invention Effects

[0016] 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 initial rise in resistance when an isocyanate-containing compound is added to a non-aqueous electrolyte. Attached Figure Description

[0017] Figure 1 This is a perspective view showing the appearance of a non-aqueous electrolyte secondary battery according to an embodiment.

[0018] Figure 2 It is along Figure 1 A cross-sectional view of a non-aqueous electrolyte secondary battery with line L1-L1 in the diagram. Detailed Implementation

[0019] 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 in the drawings.

[0020] Figure 1 This is a perspective view showing the appearance of a non-aqueous electrolyte secondary battery according to an embodiment. Figure 2 It is along Figure 1 A cross-sectional view of a non-aqueous electrolyte secondary battery with line L1-L1 in the diagram.

[0021] The non-aqueous electrolyte secondary battery 1 of this embodiment includes: an electrode body 2, a non-aqueous electrolyte (not shown), and a battery casing 3.

[0022] The battery casing 3 houses the electrode body 2, non-aqueous electrolyte, etc., and is, for example, constructed by including a casing body 5 with an opening and a sealing body 6 that seals the opening of the casing body 5. The casing body 5 is, for example, a bottomed cylindrical metal outer can, with a groove 5c formed on the upper part of the casing body 5 that protrudes inward along the circumferential direction. The sealing body 6 is supported in the groove 5c and seals the opening of the casing body 5. To ensure the airtightness of the battery interior, a sealing gasket is preferably provided between the casing body 5 and the sealing body 6.

[0023] Figure 2 The electrode body 2 shown is a wound electrode body (hereinafter referred to as wound electrode body 2) formed by winding the positive electrode 11 and the negative electrode 12 together with a spacer. However, in Figure 2 The spacer disposed between the positive electrode 11 and the negative electrode 12 is not shown in the figure. 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.

[0024] 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.

[0025] Furthermore, the negative electrode 12 has negative electrode active material layer 16 not disposed on the negative electrode current collector 14, and negative electrode current collector exposed portions 14a and 14b exposed on the negative electrode current collector 14. The negative electrode current collector exposed portion 14a is as follows: Figure 2 As shown, the negative electrode current collector exposed portion 14b is located on the innermost circumference of electrode body 2, while the negative electrode current collector exposed portion 14b is located on the outermost circumference of electrode body 2. Figure 2The outer radial surface (outer surface) 15 of the electrode body 2 in the exposed negative current collector portion 14b shown is formed by the negative current collector 14 extending at least one circumference around the outer periphery of the electrode body 2, thus 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 to be a spacer, then the outer radial surface of the electrode body 2 in 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 to be a positive electrode 11, then the outer radial surface of the electrode body 2 in the outermost periphery of the positive electrode 11 becomes the outermost peripheral surface 2a of the electrode body 2.

[0026] 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 preferable that the outer surface 15 of the exposed negative current collector 14b contacts the inner wall of the housing body 5. Thus, the housing body 5 can be used as the negative terminal 12. 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, the housing body 5 can be used as the negative terminal by connecting one end of the negative electrode tab to the negative electrode 12 (e.g., the exposed negative current collector 14a) and the other end to the housing body 5 (e.g., the bottom).

[0027] However, when manufacturing a non-aqueous electrolyte secondary battery, as described later, an isocyanate-containing compound is coated on the outermost peripheral surface 2a of the electrode body 2, or an isocyanate-containing compound is coated on the inner wall of the battery casing 3. Therefore, in the non-aqueous electrolyte secondary battery 1 of this embodiment, the outermost peripheral surface 2a of the electrode body 2 (on the inner wall of the battery casing 3) is coated with an isocyanate-containing compound. Figure 2The nitrogen concentration A1 from the isocyanate-containing compound on the outer surface 15) of the exposed portion 14b of the negative electrode current collector satisfies the relationship A1 > B with the nitrogen concentration B from the isocyanate-containing compound in the internal region inside the outermost peripheral surface 2a of the electrode body 2, and / or the nitrogen concentration A2 from the isocyanate-containing compound in the inner wall of the battery casing 3 satisfies the relationship A2 > B with the nitrogen concentration B from the isocyanate-containing compound in the internal region inside the outermost peripheral surface 2a of the electrode body 2. The internal region inside the outermost peripheral surface 2a of the electrode body 2 refers to the region where the outermost peripheral surface 2a of the electrode body 2 is radially inward. Furthermore, "from the isocyanate-containing compound" refers to the isocyanate-containing compound itself, or decomposition products of the isocyanate-containing compound resulting from charge-discharge reactions, etc. That is, in this embodiment, compared with the inner region where the outermost peripheral surface 2a of the electrode body 2 is the inside, the isocyanate-containing compound and the decomposition products of the isocyanate-containing compound are present in greater quantities on the outermost peripheral surface 2a of the electrode body 2 and / or the inner wall of the battery casing 3.

[0028] If, as in the past, isocyanate-containing compounds are added to a non-aqueous electrolyte, they decompose during charge and discharge. A film of the decomposition products of the isocyanate-containing compounds forms on the outermost peripheral surface 2a of the electrode body 2, the internal region, and the inner wall of the battery casing 3. This film suppresses the dissolution of metal from the outermost peripheral surface 2a of the electrode body 2 and the battery casing 3, thus suppressing the decrease in charge-discharge cycle characteristics. However, the film formed in the negative electrode active material layer and the like in the internal region of the electrode body 2 becomes a resistive component, thus causing an initial increase in the battery's resistance.

[0029] On the other hand, in the non-aqueous electrolyte secondary battery of this embodiment, when A1, A2, and B satisfy the relationship A1 > B and / or A2 > B, the following state is achieved: there is a large amount of film formed on the outermost peripheral surface 2a of the electrode body 2 and the inner wall of the battery casing 3 containing decomposition products of isocyanate-based compounds, while there is a small amount of film formed on the internal region of the electrode body 2 containing decomposition products of isocyanate-based compounds. In this state, the dissolution of metal from the outermost peripheral surface 2a of the electrode body 2 and the battery casing 3 is suppressed. Consequently, it is less likely 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. Therefore, the initial rise in battery resistance is also suppressed.

[0030] The ratio (B / A1) of the nitrogen concentration B from the isocyanate-containing compound in the internal region inside the outermost peripheral surface 2a of the electrode body 2 to the nitrogen concentration A1 from the isocyanate-containing compound in the same region is preferably 0.5 or less. Furthermore, the ratio (B / A2) of the nitrogen concentration B from the isocyanate-containing compound in the internal region inside the outermost peripheral surface 2a of the electrode body 2 to the nitrogen concentration A2 from the isocyanate-containing compound in the inner wall of the battery casing 3 is preferably 0.5 or less. By satisfying the above range, compared to cases where the above range is not satisfied, the decrease in the charge-discharge cycle characteristics of the battery is suppressed, or the increase in the initial resistance of the battery is suppressed.

[0031] For example, from the perspective of suppressing the decrease in the charge-discharge cycle characteristics of the battery, the nitrogen concentration A1 from the isocyanate-containing compound on the outermost peripheral surface 2a of the electrode body 2, or the nitrogen concentration A2 from the isocyanate-containing compound in the inner wall of the battery casing 3, is preferably in the range of 2 to 20, more preferably in the range of 2 to 10. Furthermore, for example, from the perspective of suppressing the initial rise in battery resistance, the nitrogen concentration B from the isocyanate-containing compound in the internal region inside the outermost peripheral surface 2a of the electrode body 2 is preferably 1 atomic percent or less, preferably zero. The method for measuring the nitrogen concentration from the isocyanate-containing compound is described in Example 1.

[0032] The negative electrode current collector 14 may be made of a foil of a metal such as copper that is stable within the potential range of the negative electrode 12, or a film of the metal disposed on the surface.

[0033] The negative electrode active material layer 16 may contain, for example, negative electrode active material, binder, etc.

[0034] As a negative electrode active material, there are no particular limitations as long as it can absorb and release lithium ions. Examples include carbon materials such as graphite, non-graphitizable carbon, easily graphitizable 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.

[0035] Examples of adhesives include: fluorinated resins, polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, styrene-butadiene rubber (SBR), nitrile rubber (NBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts (PAA-Na, PAA-K, etc., and partially neutralized salts), polyvinyl alcohol (PVA), etc. They can be used alone or in combination of two or more.

[0036] The negative electrode 12 can be made, for example, by preparing a negative electrode slurry containing negative electrode active material, binder, 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 calendering the negative electrode active material layer.

[0037] 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, omitting the description in the figures, the positive electrode 11 has a positive electrode current collector exposed portion where the positive electrode active material layer 20 is not disposed on the positive electrode current collector 18. Furthermore, one end of the positive electrode tab is connected to the positive electrode current collector exposed portion, 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.

[0038] The positive current collector 18 can be a foil of a metal such as aluminum that is stable within the potential range of the positive electrode 11, or a film of the metal disposed on the surface.

[0039] The positive electrode active material layer 20 may include, for example, a positive electrode active material, a binder, a conductive agent, etc.

[0040] 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 1-y O2, Li x Co y M 1-y O2, Li x Ni 1- y M y O2, Li x Mn2O4, Li x Mn 2-y M yO4, 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). These 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 1-y O2, Li x Ni 1-y M y O z (At least one of M, 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.

[0041] Conductive agents include, for example, carbon black (CB), acetylene black (AB), Ketjen black, graphite, and other carbon-based particles. They can be used alone or in combination of two or more.

[0042] Examples of adhesives 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.

[0043] The positive electrode 11 can be made, for example, by coating a positive electrode slurry containing positive electrode active material, binder, conductive agent, 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.

[0044] For example, porous sheets with ion-permeable and insulating properties can be used as spacers. Specific examples of porous sheets include microporous films, woven fabrics, and nonwoven fabrics. Preferably, polyethylene, polypropylene, or other olefin-based resins, or cellulose are used as materials for the spacers. The spacer can be a laminate containing a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin-based resin. Alternatively, a multilayer spacer containing a polyethylene layer and a polypropylene layer can be used, or a spacer with an aromatic polyamide resin, ceramic, or other material coated on its surface can also be used.

[0045] The non-aqueous electrolyte comprises an electrolyte salt and a non-aqueous solvent for dissolving 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 10 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 l and m are integers 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 concentration of the lithium salt is preferably set to an average of 0.8–1.8 mol per 1 L of non-aqueous solvent.

[0046] Non-aqueous solvents may include, for example, esters, ethers, nitrile solvents such as acetonitrile, amide solvents such as dimethylformamide, and mixtures of two or more of these solvents. Non-aqueous solvents may also contain halogen-substituted derivatives in which at least a portion of the hydrogen atoms of these solvents are replaced by halogen atoms such as fluorine.

[0047] 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.

[0048] Examples of the aforementioned ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, 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, dihexyl ether, and ethylethylene. Chain ethers such as methyl 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, etc.

[0049] As the halogen substitutes mentioned above, fluorocyclic carbonates such as fluoroethylene carbonate (FEC), fluorochain carbonates, and fluorochain carboxylic acid esters such as methyl fluoropropionate (FMP) are preferred.

[0050] The manufacturing method of the non-aqueous electrolyte secondary battery of this embodiment includes: the outermost peripheral surface 2a (on the positive electrode 11 and the negative electrode 12, which are wound with a spacer between them) of a wound electrode body 2. Figure 2 The manufacturing method of this embodiment includes a step of coating the outer surface 15 (of the exposed negative electrode current collector 14b) with an isocyanate-based compound; and a step of housing the wound electrode body 2 coated with the isocyanate-based compound and the non-aqueous electrolyte in the battery casing 3. In this embodiment, before housing the wound electrode body 2 coated with the isocyanate-based compound and the non-aqueous electrolyte in the battery casing 3, a step of coating the inner wall of the battery casing 3 with the isocyanate-based compound can be performed. Furthermore, the manufacturing method of this embodiment can produce a non-aqueous electrolyte secondary battery in which the nitrogen concentration A1 from the isocyanate-based compound on the outermost peripheral surface 2a of the wound electrode body 2 and the nitrogen concentration B from the isocyanate-based compound in the internal region (inner side of the outermost peripheral surface 2a) satisfy the relationship A1 > B.

[0051] The manufacturing method of the non-aqueous electrolyte secondary battery of this embodiment includes: a step of coating the inner wall of the battery casing 3 with an isocyanate-based compound; and a step of housing a wound electrode body 2 formed by winding a positive electrode 11 and a negative electrode 12 with a spacer in the battery casing 3 coated with the isocyanate-based compound, and a non-aqueous electrolyte. In the manufacturing method of this embodiment, before housing the wound electrode body 2 and the non-aqueous electrolyte in the battery casing 3 coated with the isocyanate-based compound, it is possible to have a coating applied to the outermost peripheral surface 2a of the wound electrode body 2 (in... Figure 2The process involves coating the outer surface 15) of the exposed negative electrode current collector 14b with an isocyanate-based compound. Through the manufacturing method of this embodiment, a non-aqueous electrolyte secondary battery can be obtained in which the nitrogen concentration A2 from the isocyanate-based compound in the inner wall of the battery casing 3 and the nitrogen concentration B from the isocyanate-based compound in the internal region inner to the outermost peripheral surface 2a of the wound electrode 2 satisfy the relationship A2 > B.

[0052] In the above manufacturing method, it is preferable not to coat the internal region, which is inside the outermost peripheral surface 2a of the wound electrode body 2, with an isocyanate-containing compound. However, if the internal region, which is inside the outermost peripheral surface 2a of the wound electrode body 2, is coated with an isocyanate-containing compound, it is preferable to have a smaller amount of the isocyanate-containing compound coated on the outermost peripheral surface 2a of the wound electrode body 2.

[0053] In the above manufacturing method, when coating the inner wall of the battery casing 3 with an isocyanate-based compound, the isocyanate-based compound can be coated on both the inner wall of the casing body 5 and the inner wall of the sealing body 6, but it is preferable to coat at least the inner wall of the casing body 5 with the isocyanate-based compound. This is because metals are easily dissolved from the casing body 5, which is in contact with the non-aqueous electrolyte.

[0054] The diisocyanate compound used in the above manufacturing method is not particularly limited as long as it has at least one isocyanate group in one molecule. For example, from the viewpoint of effectively suppressing the degradation of the charge-discharge cycle characteristics of the battery, it is preferable to include a compound represented by chemical formula 1: XN=C=O or chemical formula 2: O=C=NXN=C=O (where X is: an aliphatic hydrocarbon group of C1 to C12, optionally having heteroatoms; or an aromatic hydrocarbon group of C6 to C20, optionally having heteroatoms). The aliphatic hydrocarbon group can be chain-like or cyclic, and the chain-like aliphatic hydrocarbon group can be linear or branched.

[0055] For example, from the perspective of effectively suppressing the reduction of the charge-discharge cycle characteristics of the battery, the number of carbon atoms in the aliphatic hydrocarbon group is preferably in the range of C1 to C12, and more preferably in the range of C2 to C10. Furthermore, from the perspective of effectively suppressing the reduction of the charge-discharge cycle characteristics of the battery, the number of carbon atoms in the aromatic hydrocarbon group is preferably in the range of C6 to C20, and more preferably in the range of C8 to C18.

[0056] Examples of aliphatic hydrocarbon groups include alkyl, alkenyl, and ynyl groups. Examples of aromatic hydrocarbon groups include phenyl, tolyl, benzyl, and phenethyl groups.

[0057] 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.

[0058] Examples of diisocyanate compounds represented by the above general formula include: methyl isocyanate, ethyl isocyanate, propyl isocyanate, isopropyl isocyanate, butyl isocyanate, tert-butyl isocyanate, pentyl isocyanate, hexyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, vinyl isocyanate, allyl isocyanate, ethynyl isocyanate, propynyl isocyanate, monomethylene diisocyanate, dimethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, heptamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, decamethylene diisocyanate, dodecamethylene diisocyanate, propane 1,3-diisocyanate, 1,4-butene diisocyanate, 1,5-pentene diisocyanate, 1 5-Diisocyanate-2-methylpentane, 1,6-diisocyanate-2-hexene, 1,6-diisocyanate-3-hexene, toluene diisocyanate, xylene diisocyanate, toluene diisocyanate, 1,2-bis(methyl isocyanate)cyclohexane, 1,3-bis(methyl isocyanate)cyclohexane, 1,4-bis(methyl isocyanate)cyclohexane, 1,2-diisocyanate, 1,3-diisocyanate, Cyclohexane 1,4-diisocyanate, dicyclohexylmethane-1,1'-diisocyanate, dicyclohexylmethane-2,2'-diisocyanate, dicyclohexylmethane-3,3'-diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, bicyclo[2.2.1]heptane-2,5-dimethylbis(methylisocyanate), bicyclo[2.2.1]heptane-2,6-dimethylbis(methylisocyanate), etc. These compounds can be used alone or in combination of two or more.

[0059] Example

[0060] The present invention will be further illustrated below by way of examples, but the present invention is not limited to these examples.

[0061] <Example>

[0062] [The production of the positive electrode]

[0063] As the positive electrode active material, lithium nickel cobalt oxide (LiNi) containing aluminum is used. 0.88 Co 0.09 Al 0.03O2). 100 parts by weight of the above-mentioned positive electrode active material, 1 part by weight of acetylene black, and 0.9 parts by weight of polyvinylidene fluoride were mixed in N-methyl-2-pyrrolidone (NMP) solvent to prepare a positive electrode slurry. This slurry was coated onto both sides of a 15 μm thick aluminum foil. After drying the coating, it was calendered using calendering rollers to create a positive electrode with positive electrode active material layers formed on both sides of the positive electrode current collector. The prepared positive electrode was cut into pieces with a width of 57.6 mm and a length of 679 mm for use.

[0064] [Making the negative electrode]

[0065] As the negative electrode active material, a mixture was prepared by mixing graphite powder to a concentration of 95 parts by mass and Si oxide to a concentration of 5 parts by mass. 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 cut into pieces with a width of 58.6 mm and a length of 662 mm for use.

[0066] [Preparation of non-aqueous electrolytes]

[0067] The product is prepared by dissolving LiPF6 at a concentration of 1.4 mol / L in a non-aqueous solvent obtained by mixing ethylene carbonate (EC), ethyl methyl carbonate (MEC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75, and then adding 3% by mass of ethylene carbonate (VC).

[0068] [Fabrication of Non-Aqueous Electrolyte Secondary Batteries]

[0069] An aluminum positive electrode lead is attached to the positive current collector, and a nickel-copper-nickel negative electrode lead is attached to the negative current collector. A polyethylene spacer is placed between the positive and negative electrodes, and the electrodes are wound together to create a wound electrode body. Hexamethylene diisocyanate (HMDI) in an amount of 0.1% by mass 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 welded to the main body of the casing, and the positive electrode lead is welded to a sealing body, housing the electrode body within the casing body. Then, non-aqueous electrolyte is injected into the casing body under reduced pressure. The open end of the casing body is riveted with a sealing gasket, thus creating a non-aqueous electrolyte secondary battery. The battery capacity is 3300 mAh.

[0070] <Comparative Example 1>

[0071] Hexamethylene diisocyanate (HMDI) was not coated on the outer peripheral surface of the wound electrode body. Otherwise, a non-aqueous electrolyte secondary battery was fabricated in the same manner as in the example.

[0072] <Comparative Example 2>

[0073] Hexamethylene diisocyanate (HMDI) was not coated on the outer peripheral surface of the wound electrode body, and 0.1% by mass of hexamethylene diisocyanate (HMDI) was added to the non-aqueous electrolyte of the example. Otherwise, the non-aqueous electrolyte secondary battery was made in the same manner as in the example.

[0074] <Comparative Example 3>

[0075] Hexamethylene diisocyanate was not coated on the outer peripheral surface of the wound electrode body, and 0.5% by mass of hexamethylene diisocyanate was added to the non-aqueous electrolyte of the example. Otherwise, the non-aqueous electrolyte secondary battery was made in the same manner as in the example.

[0076] [Initial resistance measurement]

[0077] 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). Then, they were charged with a constant voltage of 4.2V and a termination current of 66mA to adjust the state of charge (SOC) to 100%. Then, at an ambient temperature of 25°C, the AC impedance was measured, and the resistance value at 0.02Hz was used as the initial resistance.

[0078] [Charge-discharge cycle characteristics]

[0079] The non-aqueous electrolyte secondary batteries of the examples and comparative examples were constant-current charged to 4.2V at an ambient temperature of 25°C with a constant current of 990mA (0.3It), and then constant-voltage charged with a constant voltage of 4.2V and a termination current of 66mA. Next, they were constant-current discharged to 3.0V with a constant current of 990mA (0.3It). This charge-discharge cycle was considered one cycle, and 400 cycles were performed. The capacity retention rate was determined based on the following formula. A higher capacity retention rate indicates that the degradation of charge-discharge cycle characteristics is more suppressed.

[0080] Capacity retention (%) = (Discharge capacity in the 400th cycle / Discharge capacity in the 1st cycle) × 100

[0081] [Determination of nitrogen concentration from isocyanate-containing compounds]

[0082] For each battery after its initial resistance was measured, it was discharged at a constant current of 1650 mA (0.5 It) to 3.0 V at an ambient temperature of 25°C. Then, in an argon atmosphere, each battery was disassembled. The exposed negative electrode current collector on the outermost circumferential surface of the electrode body was cut out, and the negative electrode on the innermost circumferential surface (the center of the electrode core) was also 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 nitrogen concentration on the outermost circumferential surface of the electrode body was taken as the nitrogen concentration A from the isocyanate-containing compound on the outermost circumferential surface of the electrode body, and the nitrogen concentration at the negative electrode on the innermost circumferential surface of the electrode body was taken as the nitrogen concentration B from the isocyanate-containing compound in the internal region of the electrode body. The nitrogen concentration ratio (B / A) was calculated. For the determination of the nitrogen concentration in the internal region of the electrode body, assuming the battery does not contain isocyanate-containing compounds, any part of the internal region of the electrode body can be used as the measurement site. Furthermore, when it is unclear whether the battery contains isocyanate-containing compounds, multiple locations (preferably 10 to 15 locations) within the internal region of the electrode body must be used as measurement sites. Moreover, among the measurement sites within the internal region of the electrode body, the highest nitrogen concentration should be used.

[0083] Table 1 summarizes the results of initial resistance, capacity retention, and nitrogen concentration ratio (B / A) for the examples and comparative examples.

[0084] [Table 1]

[0085]

[0086] As shown in Table 1, the initial resistance of Example 1 is the same as that of Comparative Example 1, and is lower than that of Comparative Examples 2 and 3. Furthermore, the capacity retention rate of Example 1 is the same as that of Comparative Example 3, and is higher than that of Comparative Examples 1 and 2. Therefore, according to Example 1, the increase in initial resistance can be suppressed, and the decrease in charge-discharge cycle characteristics can also be suppressed.

[0087] Explanation of reference numerals in the attached figures

[0088] 1. Non-aqueous electrolyte secondary battery; 2. Electrode body (wound electrode body); 2a. Outermost peripheral surface; 3. Battery casing; 5. Casing 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, comprising: A wound electrode body formed by winding the positive and negative electrodes together with a spacer between them. Non-aqueous electrolytes, and A battery casing that houses the wound electrode body and the non-aqueous electrolyte. in, The nitrogen concentration A1 of the decomposition products of isocyanate-containing compounds caused by the charge-discharge reaction on the outermost peripheral surface of the wound electrode body, and the nitrogen concentration B of the decomposition products of isocyanate-containing compounds caused by the charge-discharge reaction in the internal region that is inside the outermost peripheral surface of the wound electrode body, satisfy the relationship A1 > B. The isocyanate-containing compound is a compound represented by chemical formula 1: X-N=C=O or chemical formula 2: O=C=N-X-N=C=O. In the formula, X is: an aliphatic hydrocarbon group of C1~C12, optionally having heteroatoms; or an aromatic hydrocarbon group of C6~C20, optionally having heteroatoms.

2. 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 on the outermost circumferential surface of the wound electrode, B / A1, is less than 0.

5.

3. A non-aqueous electrolyte secondary battery, comprising: A wound electrode body formed by winding the positive and negative electrodes together with a spacer between them. Non-aqueous electrolytes, and A battery casing that houses the wound electrode body and the non-aqueous electrolyte. in, The nitrogen concentration A2 of the decomposition products of isocyanate-containing compounds caused by the charge-discharge reaction in the inner wall of the battery casing, and the nitrogen concentration B of the decomposition products of isocyanate-containing compounds caused by the charge-discharge reaction in the inner region that is the inner side of the outermost peripheral surface of the wound electrode body, satisfy the relationship A2 > B. The isocyanate-containing compound is a compound represented by chemical formula 1: X-N=C=O or chemical formula 2: O=C=N-X-N=C=O. In the formula, X is: an aliphatic hydrocarbon group of C1~C12, optionally having heteroatoms; or an aromatic hydrocarbon group of C6~C20, optionally having heteroatoms.

4. The non-aqueous electrolyte secondary battery according to claim 3, 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 casing, B / A2, is less than 0.

5.

5. The method for manufacturing a non-aqueous electrolyte secondary battery according to claim 1, comprising: The process of coating the outermost circumferential surface of a wound electrode body, formed by winding the positive and negative electrodes with spacers between them, with an isocyanate-based compound applied; and The process of housing the wound electrode body coated with the isocyanate-containing compound and the non-aqueous electrolyte into the battery casing. in, The isocyanate-containing compound is a compound represented by chemical formula 1: X-N=C=O or chemical formula 2: O=C=N-X-N=C=O. In the formula, X is: an aliphatic hydrocarbon group of C1~C12, optionally having heteroatoms; or an aromatic hydrocarbon group of C6~C20, optionally having heteroatoms.

6. The method for manufacturing the non-aqueous electrolyte secondary battery according to claim 3, comprising: The process of coating the inner wall of the battery casing with an isocyanate-based compound; and The process of housing a wound electrode body, formed by winding the positive and negative electrodes with a spacer between them, and a non-aqueous electrolyte in a battery casing coated with the aforementioned isocyanate-containing compound. The isocyanate-containing compound is a compound represented by chemical formula 1: X-N=C=O or chemical formula 2: O=C=N-X-N=C=O. In the formula, X is: an aliphatic hydrocarbon group of C1~C12, optionally having heteroatoms; or an aromatic hydrocarbon group of C6~C20, optionally having heteroatoms.

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