Nonaqueous electrolyte secondary battery

Abstract

The non-aqueous electrolyte secondary battery has a wound electrode body provided with a negative electrode (12) in which a negative electrode mixture layer (32) is formed on a negative electrode core (30), and the negative electrode (12) has a non-facing portion (12a) that does not face the positive electrode with the separator interposed therebetween on the inner end side in the winding direction of the electrode body. The non-facing section (12a) has, on at least one surface of the negative electrode core (30), a mixture non-facing section (12c) on which the negative electrode mixture layer (32) is formed, and in the mixture non-facing section (12c), the length in the winding direction of the negative electrode mixture layer (32a) formed on the inner peripheral surface (30a) of the negative electrode core (30) is 0.3 cycles or more along the winding direction of the mixture non-facing section (12c). The length in the winding direction of the negative electrode mixture layer (32b) formed on the outer peripheral surface (30b) of the negative electrode core (30) is 2 / 3 or less of the length in the winding direction of the negative electrode mixture layer (32a) formed on the inner peripheral surface (30a) of the negative electrode core (30).

Description

Technical Field

[0001] The present application relates to a non-aqueous electrolyte secondary battery. Background Art

[0002] In recent years, nonaqueous electrolyte secondary batteries including an electrode body in which a positive electrode and a negative electrode are arranged to face each other with a separator interposed therebetween have been widely used as secondary batteries with high output and high energy density.

[0003] For example, Patent Document 1 discloses a non-aqueous electrolyte secondary battery comprising a wound electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween, wherein the negative electrode comprises a non-opposing portion wound for more than 1.25 turns from the inner end in the winding direction of the wound electrode body so as not to face the positive electrode with the separator interposed therebetween, and the non-opposing portion comprises, on at least one surface, a negative electrode mixture layer forming portion in which the negative electrode mixture layer is continuously formed from the outer end in the winding direction to the inner side in the winding direction, and the negative electrode mixture layer forming portion is wound for more than 0.75 turns.

[0004] The circularity of the winding core of the electrode body can be improved by providing a non-opposing portion that does not face the positive electrode at the inner end of the electrode body in the winding direction as in Patent Document 1. This can maintain the air venting property of the winding core, thereby achieving battery safety.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2018 / 116876 Summary of the invention

[0008] However, in a non-aqueous electrolyte secondary battery having a wound electrode body, when the electrode body expands during charge and discharge cycles, stress is locally applied to the center of the electrode body, causing the electrode plate at the facing portion of the positive electrode and the negative electrode to deform, resulting in deviations in the charge depth within the electrode plate surface.

[0009] Therefore, an object of the present application is to provide a non-aqueous electrolyte secondary battery capable of suppressing deformation of the electrode plate at the portion where the positive electrode and the negative electrode face each other while maintaining the circularity of the winding core portion of the electrode body.

[0010] The non-aqueous electrolyte secondary battery of the present application is characterized in that it comprises an electrode body formed by winding a positive electrode and a negative electrode sandwich having a negative electrode mixture layer formed on a negative electrode core body with a separator therebetween, the negative electrode having a non-opposing portion that does not face the positive electrode sandwich with the separator therebetween on the inner end side in the winding direction of the electrode body, the non-opposing portion having a mixture non-opposing portion on at least one surface of the negative electrode core body from the outer end in the winding direction of the non-opposing portion toward the inner side in the winding direction where the negative electrode mixture layer is formed, in the mixture non-opposing portion, a length in the winding direction of the negative electrode mixture layer formed on the inner peripheral surface of the negative electrode core body facing the radial inner side of the electrode body is a length of more than 0.3 turns along the winding direction of the mixture non-opposing portion, and a length in the winding direction of the negative electrode mixture layer formed on the outer peripheral surface of the negative electrode core body facing the radial outer side of the electrode body is less than 2 / 3 of a length in the winding direction of the negative electrode mixture layer formed on the inner peripheral surface of the negative electrode core body.

[0011] According to the present application, a nonaqueous electrolyte secondary battery can be provided which can suppress deformation of the electrode plate at the portion where the positive electrode and the negative electrode face each other while maintaining the circularity of the winding core portion of the electrode body. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery as an example of an embodiment.

[0013] Figure 2 It is schematically indicated Figure 1 FIG. 2 is a diagram of a portion of an electrode body on the inner end side in the winding direction, taken along the AA cross section.

[0014] Figure 3 It is a schematic cross-sectional view showing the structure of the negative electrode on the inner end side in the winding direction of the electrode body.

[0015] Figure 4 It is a diagram for explaining the evaluation method of electrode plate deformation. DETAILED DESCRIPTION

[0016] Hereinafter, an example of an embodiment of the nonaqueous electrolyte secondary battery of the present application will be described in detail.

[0017] Figure 1 It is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery as an example of an embodiment. Figure 1The non-aqueous electrolyte secondary battery 10 shown includes a wound electrode body 14 formed by winding a positive electrode 11 and a negative electrode 12 with a separator 13 interposed therebetween, a non-aqueous electrolyte, insulating plates 18a and 18b respectively disposed above and below the electrode body 14, and a battery case 15 as an outer packaging body. The battery case 15 is composed of a case body 16 that accommodates the electrode body 14, the non-aqueous electrolyte, etc., and a sealing body 17 that seals the opening of the case body 16. The battery case 15 is not limited to a cylindrical or square metal case, and may be, for example, a resin case formed by laminating resin sheets (so-called laminated type) or the like.

[0018] The non-aqueous electrolyte includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous solvent may be, for example, esters, ethers, nitriles, amides, and mixed solvents of two or more thereof. The non-aqueous solvent may also contain a halogen-substituted substance in which at least a portion of hydrogen in the solvent is replaced with a halogen atom such as fluorine. The electrolyte salt may be, for example, a lithium salt such as LiPF6.

[0019] The outer shell body 16 is, for example, a metal container in a cylindrical shape with a bottom. A gasket 27 is provided between the outer shell body 16 and the sealing body 17 to ensure the airtightness of the inside of the battery. The outer shell body 16 has, for example, a protrusion 21 for supporting the sealing body 17, which is obtained by protruding a part of the side surface inward. The protrusion 21 is preferably formed in an annular shape along the circumferential direction of the outer shell body 16, and the sealing body 17 is supported by its upper surface.

[0020] The sealing body 17 has a structure in which a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25 and a cover 26 are stacked in order from the electrode body 14 side. The components constituting the sealing body 17 have, for example, a disc shape or a ring shape, and the components except the insulating member 24 are electrically connected to each other. The lower valve body 23 and the upper valve body 25 are connected to each other at their respective central portions, and an insulating member 24 is sandwiched between their respective peripheral portions. When the internal pressure of the non-aqueous electrolyte secondary battery 10 rises due to heat caused by an internal short circuit, for example, the lower valve body 23 is deformed and broken in a manner that pushes the upper valve body 25 toward the cover 26 side, thereby blocking the current path between the lower valve body 23 and the upper valve body 25. When the internal pressure rises further, the upper valve body 25 breaks, and gas is discharged from the opening of the cover 26.

[0021] Figure 1In the non-aqueous electrolyte secondary battery 10 shown, the positive electrode lead 19 mounted on the positive electrode 11 extends toward the sealing body 17 side through the through hole of the insulating plate 18a, and is connected to the lower surface of the filter 22 as the bottom plate of the sealing body 17 by welding or the like. Thus, the cover 26 as the top plate of the sealing body 17 electrically connected to the filter 22 becomes the positive terminal. In addition, the negative electrode lead 20a connected to the negative electrode 12 on the winding start side of the electrode body 14 and the negative electrode 20b connected to the negative electrode 12 on the winding end side of the electrode body 14 extend toward the bottom side of the outer shell body 16 through the insulating plate 18b, and are connected to the bottom inner surface of the outer shell body 16 by welding or the like. Thus, the outer shell body 16 becomes the negative terminal.

[0022] Figure 2 It is schematically indicated Figure 1 FIG. 2 is a diagram of a portion of an electrode body on the inner end side in the winding direction, taken along the AA cross section. Figure 2 In order to facilitate understanding of the configuration relationship, the negative electrode 12 is represented by a solid line, the positive electrode 11 is represented by a dotted line, and the separator 13 is represented by a single-dot chain line. Figure 2 In the figure, the gap between the positive electrode 11, the negative electrode 12, and the separator 13 is exaggeratedly shown. The electrode body 14 is formed by winding the positive electrode 11 and the negative electrode 12 with the separator 13 interposed therebetween. Specifically, the strip-shaped positive electrode 11, the strip-shaped negative electrode 12, and a pair of strip-shaped separators 13 are stacked in the order of one separator 13, the positive electrode 11, the other separator 13, and the negative electrode 12, and the stack is wound into a spiral shape, thereby manufacturing the electrode body 14. In the electrode body 14, the length direction of each electrode becomes the winding direction, and the width direction of each electrode becomes the winding axis direction.

[0023] Figure 3 It is a schematic cross-sectional view showing the structure of the negative electrode on the inner end side in the winding direction of the electrode body. Figure 3 In the figure, the positive electrode 11 and the separator 13 are not shown. Figure 3 As shown, the negative electrode 12 includes, for example, a negative electrode core 30 and a negative electrode mixture layer 32 formed on the negative electrode core 30 . Figure 3 The negative electrode mixture layer 32 shown is formed on both sides of the negative electrode core 30, for example, and includes a negative electrode mixture layer 32a and a negative electrode mixture layer 32b. The negative electrode mixture layer 32a is formed on the inner peripheral surface 30a of the negative electrode core 30 facing the radial inner side of the electrode body 14, and the negative electrode mixture layer 32b is formed on the outer peripheral surface 30b of the negative electrode core 30 facing the radial outer side of the electrode body 14. In addition, as Figure 2 As shown, the negative electrode 12 has a non-opposing portion 12a which does not face the positive electrode 11 via the separator 13 at the inner end side in the winding direction which is the winding start side of the electrode body 14. In addition, the negative electrode 12 has an opposing portion 12b which is continuously wound after the non-opposing portion 12a and faces the positive electrode 11 via the separator 13.

[0024] The non-opposing portion 12a includes a mixture non-opposing portion 12c and a core material non-opposing portion 12d disposed on the inner side of the mixture non-opposing portion 12c in the winding direction. Figure 2 In the figure, the mixture non-opposing portion 12c (and the opposing portion 12b) is represented by a thick solid line, and the core material non-opposing portion 12d is represented by a thin solid line. The mixture non-opposing portion 12c is a portion where a negative electrode mixture layer is formed on at least one surface of the negative electrode core body (at least one of the inner peripheral surface 30a and the outer peripheral surface 30b of the negative electrode core body 30) from the outer end (point E3) of the non-opposing portion 12a in the winding direction toward the inner side of the winding direction. In the figure, it is a portion from point E3 along the winding direction to point E2. It should be noted that the outer end (point E3) of the non-opposing portion 12a in the winding direction becomes the opposing portion on the inner side of the winding of the starting end (point D1) of the positive electrode 11 in the winding direction. The core non-opposing portion 12d is a portion where no negative electrode mixture layer is formed on both surfaces of the negative electrode core body from the inner end (point E1) of the non-opposing portion 12a in the winding direction toward the outer side in the winding direction. In the figure, it is a portion from point E1 to point E2 along the winding direction.

[0025] Regarding the mixture non-opposing portion 12c, for example, from the perspective of suppressing deformation of the electrode plate at the portion where the positive electrode 11 and the negative electrode 12 face each other while maintaining the circularity of the winding core portion of the electrode body 14, it is preferred to wind the mixture non-opposing portion 12c in a range of 0.4 turns or more and 0.8 turns or less from the outer end in the winding direction of the non-opposing portion 12a toward the inner side in the winding direction. If the number of winding turns of the mixture non-opposing portion 12c is less than 0.4 turns, the circularity of the winding core portion may be reduced compared to the case of more than 0.4 turns, and if it is greater than 0.8 turns, the effect of suppressing deformation of the electrode plate at the portion where the positive electrode 11 and the negative electrode 12 face each other may be reduced compared to the case of less than 0.8 turns.

[0026] In the present embodiment, in the mixture non-opposing portion 12c, the length (A) of the negative electrode mixture layer 32a formed on the inner peripheral surface 30a of the negative electrode core 30 facing the radial inner side of the electrode body 14 in the winding direction is a length of 0.3 turns or more along the winding direction of the mixture non-opposing portion 12c, and the length (B) of the negative electrode mixture layer 32b formed on the outer peripheral surface 30b of the negative electrode core 30 facing the radial outer side of the electrode body 14 in the winding direction is 2 / 3 or less of the length (A) of the negative electrode mixture layer 32a formed on the inner peripheral surface 30a of the negative electrode core 30 in the winding direction. When the length (A) of the negative electrode mixture layer 32a in the winding direction and the length (B) of the negative electrode mixture layer 32b in the winding direction meet the above ranges, the circularity of the winding core portion located at the center of the electrode body 14 can be maintained compared to the case where the above ranges are not met. In addition, when the electrode body 14 expands with the charge and discharge cycle, even if stress is applied to the center side of the electrode body 14, the friction between the non-opposing portion 12a and the negative electrode on the winding outside of the non-opposing portion 12a is reduced, and the deformation of the electrode plate at the portion where the positive electrode 11 and the negative electrode 12 face each other can be suppressed. Although the description in the figure is omitted, in the mixture non-opposing portion 12c, the negative electrode mixture layer 32 can also be formed only on the inner peripheral surface 30a of the negative electrode core 30 facing the radial inside of the electrode body 14, and not formed on the outer peripheral surface 30b of the negative electrode core 30 facing the radial outside of the electrode body 14. With this configuration, the circularity of the winding core can be maintained, and the deformation of the electrode plate at the portion where the positive electrode 11 and the negative electrode 12 face each other can be suppressed. It should be noted that the negative electrode mixture layer 32 is not limited to being formed on both surfaces of the negative electrode core 30 in the non-opposing portion 12a and the opposing portion 12b, but may be formed on only one surface of the negative electrode core 30 in the non-opposing portion 12a and the opposing portion 12b.

[0027] In the mixture non-opposing portion 12c, the length (A) of the negative electrode mixture layer 32a formed on the inner peripheral surface 30a of the negative electrode core body 30 in the winding direction is more preferably 0.7 turns or more and 1.0 turns or less along the winding direction of the mixture non-opposing portion 12c. In addition, in the mixture non-opposing portion 12c, the length (B) of the negative electrode mixture layer 32b formed on the outer peripheral surface 30b of the negative electrode core body 30 in the winding direction is more preferably 0.3 turns or more and 0.6 turns or less along the winding direction of the mixture non-opposing portion 12c. When the length (A) of the winding direction of the negative electrode mixture layer 32a and the length (B) of the winding direction of the negative electrode mixture layer 32b satisfy the above ranges, the deformation of the electrode plate at the portion where the positive electrode 11 and the negative electrode 12 face each other can be further suppressed compared to the case where the above ranges are not satisfied.

[0028] Preferably, as in the present embodiment, the non-opposing portion 12a has a core non-opposing portion 12d. With respect to the core non-opposing portion 12d, for example, in consideration of ensuring the installation space of the negative electrode lead, it is preferred that the core non-opposing portion 12d is wound from the inner end (point E2) of the mixture non-opposing portion 12c in the winding direction toward the inner side of the winding direction for more than 0.5 turns. Figure 1 The negative electrode lead 20a shown is preferably connected to the negative electrode core 30 provided at the core non-opposing portion 12d of the non-opposing portion 12a by welding or the like. That is, the negative electrode lead 20a is preferably connected to the negative electrode core 30 at the inner end side of the winding direction of the electrode body 14. For example, by collecting current at two locations based on the negative electrode lead 20b provided at the outer end side of the winding direction of the electrode body 14 and the negative electrode lead 20a provided at the inner end side of the winding direction, the resistance component of the battery can be reduced. In addition, the negative electrode core 30 at the outer end side of the winding direction of the electrode body 14 can also be made to contact the outer shell body 16. In this way, the resistance component of the battery can be further reduced.

[0029] The negative electrode core 30 constituting the negative electrode 12 can be made of a foil of a metal such as copper or copper alloy that is stable in the potential range of the negative electrode, or a film having the metal disposed on the surface. The thickness of the negative electrode core 30 is, for example, in the range of 10 μm to 50 μm.

[0030] In addition, the negative electrode mixture layer 32 constituting the negative electrode 12 includes, for example, a negative electrode active material, a binder, etc. The thickness of the negative electrode mixture layer 32 is, for example, in the range of 10 μm to 100 μm. For example, a negative electrode mixture slurry including a negative electrode active material, a binder, etc. is applied to the negative electrode core body, and after the coating is dried, the negative electrode mixture layer 32 is formed on the negative electrode core body 30 by rolling, thereby the negative electrode 12 can be manufactured.

[0031] The negative electrode active material contained in the negative electrode mixture layer 32 is not particularly limited as long as it can reversibly absorb and release lithium ions, and examples thereof include carbon materials and Si-based materials. From the perspective of increasing the capacity of the battery, the negative electrode active material preferably contains a Si-based material.

[0032] The carbon material may be, for example, a conventionally known carbon material used as a negative electrode active material, for example, natural graphite such as flaky graphite, bulk graphite, and earthy graphite, and artificial graphite such as bulk artificial graphite (MAG) and graphitized mesocarbon microbeads (MCMB).

[0033] The Si-based material includes, for example, a lithium ion conductive phase and Si particles dispersed in the lithium ion conductive phase. The lithium ion conductive phase includes, for example, at least one of a silicon oxide phase, a silicate phase, and a carbon phase.

[0034] The silicate phase preferably contains at least one element of the Group 2 elements of the periodic table to which alkali metal elements such as lithium, sodium, potassium, rubidium, cesium, and francium, beryllium, magnesium, calcium, strontium, barium, and radium belong, from the perspective of high lithium ion conductivity. Among them, the silicate phase is preferably a silicate phase containing lithium (hereinafter sometimes referred to as a lithium silicate phase) from the perspective of high lithium ion conductivity.

[0035] Lithium silicate phase is represented by the formula: Li 2z SiO 2＋z (0<z<2). From the viewpoints of stability, ease of production, lithium ion conductivity, etc., z preferably satisfies the relationship of 0<z<1, and more preferably z=1 / 2.

[0036] Si-based materials, such as SiO x (preferably in the range of 0<x<2, more preferably in the range of 0.5≤x≤1.6). The Si-based material in which Si particles are dispersed in the carbon phase is represented by the general formula Si x C y (Preferably, the range of 0<x≤1 and 0<y≤1) is represented.

[0037] A conductive layer covered with conductive carbon can be formed on the surface of the Si-based material. The conductive layer can be formed, for example, by a CVD method using acetylene, methane, etc.; a method of mixing coal tar, petroleum asphalt, phenolic resin, etc. with a silicon-based active material and performing a heat treatment, etc. As a heat treatment device for heat treatment, for example, a hot air furnace, a hot press, a lamp, a mantle heater, a ceramic heater, a rotary furnace, etc. can be used. In addition, a conductive layer can also be formed by fixing a conductive filler such as carbon black to the particle surface of the Si-based material using a bonding material.

[0038] The content of the Si-based material is preferably 5% by mass or more based on the total mass of the negative electrode mixture layer 32 , for example, from the viewpoint of increasing the capacity of the battery.

[0039] Examples of negative electrode active materials include carbon materials and Si-based materials, and other materials that can reversibly store and release lithium ions, such as Sn, alloys containing Sn, Sn-based materials such as tin oxide, and Ti-based materials such as lithium titanate.

[0040] Examples of the binder include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide-based resins, acrylic resins, polyolefin-based resins, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC) or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol (PVA), polyethylene oxide (PEO), and the like.

[0041] The positive electrode 11 has a positive electrode core and a positive electrode mixture layer formed on the surface of the positive electrode core. The positive electrode mixture layer is preferably formed on both sides of the positive electrode core. The positive electrode core can use a foil of a metal such as aluminum that is stable in the potential range of the positive electrode 11, a film having the metal configured on the surface, and the like. The positive electrode mixture layer, for example, includes a positive electrode active material, a binder, a conductive agent, and the like. For example, a positive electrode mixture slurry including a positive electrode active material, a binder, a conductive agent, and the like is applied to the positive electrode core, and after the coating is dried, it is rolled to form a positive electrode mixture layer on both sides of the positive electrode core, thereby making the positive electrode 11.

[0042] Examples of the positive electrode active material contained in the positive electrode mixture layer include lithium transition metal oxides containing transition metal elements such as Co, Mn, and Ni. For example, lithium transition metal oxides are Li x CoO2、Li x NiO2、Li x MnO2、Li x Co y Ni 1-y O2、Li x Co y M 1-y O z , Li x Ni 1-y M y O z , Li x Mn2O4、Li x Mn 2-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 alone or in combination. From the perspective of achieving a high capacity of a non-aqueous electrolyte secondary battery, 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 (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) etc. Inorganic particles such as tungsten oxide, aluminum oxide, and compounds containing lanthanide elements may be fixed to the surface of the lithium transition metal oxide particles.

[0043] Examples of the conductive agent contained in the positive electrode mixture layer include carbon black (CB), acetylene black (AB), Ketjen black, carbon nanotubes (CNT), graphene, graphite and other carbon materials. Examples of the binder contained in the positive electrode mixture layer include the same binders as those in the case of the negative electrode 12 .

[0044] For example, the spacer 13 may be a porous sheet having ion permeability and insulation. Specific examples of porous sheets include microporous films, woven fabrics, nonwoven fabrics, etc. Suitable materials for the spacer include olefin resins such as polyethylene and polypropylene, cellulose, etc. The spacer 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. In addition, it may be a multilayer spacer including a polyethylene layer and a polypropylene layer, or a spacer having a material such as an aramid resin or ceramics coated on the surface of the spacer 13 may be used.

[0045] Example

[0046] Hereinafter, the present application will be further described using examples; however, the present application is not limited to these examples.

[0047] <Example 1>

[0048] [Production of positive electrode]

[0049] 100 parts by mass of LiNi 0.88 Co 0.09 Al 0.03 O2, 1 part by mass of acetylene black (AB) and 0.9 part by mass of polyvinylidene fluoride (PVDF) are mixed, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) is added to prepare a positive electrode mixture slurry. Then, the positive electrode mixture slurry is applied to both sides of an aluminum foil with a thickness of 15 μm, and the coating is dried. Thereafter, the coating is rolled using a roller, and then cut into a specified electrode size to produce a positive electrode with a positive electrode mixture layer formed on both sides of the positive electrode core. In the central part of the longitudinal direction of the positive electrode, an exposed portion where the positive electrode mixture layer is not formed and the positive electrode core is exposed is provided, and an aluminum positive electrode lead is welded to the exposed portion.

[0050] [Production of negative electrode]

[0051] 92 parts by mass of graphite powder, 6 parts by mass of Si-based materials, 1 part by mass of sodium carboxymethylcellulose (CMC-Na) and 1 part by mass of styrene butadiene rubber (SBR) dispersion were mixed, and an appropriate amount of water was added to prepare a negative electrode mixture slurry. Then, the negative electrode mixture slurry was applied to both sides of a copper foil with a thickness of 8 μm, and the coating was dried. Thereafter, the coating was rolled using a roller, and then cut into a specified electrode size to produce a negative electrode with a negative electrode mixture layer formed on both sides of the negative electrode core. At both ends of the negative electrode in the longitudinal direction, a negative electrode core exposed portion where the negative electrode core is exposed without forming a negative electrode mixture layer is provided, and a nickel negative electrode lead is welded to each negative electrode core exposed portion.

[0052] [Electrode body production]

[0053] The positive electrode and the negative electrode are wound into a spiral shape with a separator sandwiched therebetween to produce a wound electrode body. The number of windings of the electrode body is set to 18 turns based on the positive electrode. In addition, the non-opposing portion of the negative electrode mixture is wound 0.3 turns from the outer end of the non-opposing portion in the winding direction toward the inner side in the winding direction. In the non-opposing portion of the mixture, the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body facing the radial outer side of the electrode body and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body facing the radial inner side of the electrode body are set to be 0.2 turns and 0.3 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0054] [Preparation of non-aqueous electrolyte]

[0055] To 100 parts by mass of a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 3:7 was added 5 parts by mass of vinylene carbonate (VC), and lithium hexafluorophosphate (LiPF6) was dissolved at a concentration of 1.5 mol / L to prepare a non-aqueous electrolyte.

[0056] [Manufacturing of non-aqueous electrolyte secondary batteries]

[0057] Insulating plates were placed above and below the electrode body, and the electrode body was housed in the outer shell. The negative electrode lead was welded to the bottom of the outer shell, and the positive electrode lead was welded to the sealing body. After injecting a non-aqueous electrolyte into the outer shell, the opening of the outer shell was sealed with a sealing body through a gasket, and then left to stand in a constant temperature bath at 60°C for 15 hours to produce a non-aqueous electrolyte secondary battery.

[0058] <Example 2>

[0059] A non-aqueous electrolyte secondary battery was manufactured using the same method as in Example 1, except that the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 0.2 turns and 0.8 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0060] <Example 3>

[0061] A non-aqueous electrolyte secondary battery was manufactured using the same method as in Example 1, except that the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 0.3 turns and 0.45 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0062] <Example 4>

[0063] A non-aqueous electrolyte secondary battery was manufactured using the same method as in Example 1, except that the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 0.3 turns and 0.8 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0064] <Example 5>

[0065] A non-aqueous electrolyte secondary battery was manufactured using the same method as in Example 1, except that the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 0.5 and 0.8 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0066] <Example 6>

[0067] A non-aqueous electrolyte secondary battery was manufactured using the same method as in Example 1, except that the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 0.3 turns and 1.25 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0068] <Example 7>

[0069] A non-aqueous electrolyte secondary battery was manufactured using the same method as in Example 1, except that the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 0.8 turns and 1.6 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0070] <Comparative Example 1>

[0071] A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1, except that the amount of Si-based material added was replaced from 6 parts by mass to 4 parts by mass, and the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 0.2 turns and 0.2 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0072] <Comparative Example 2>

[0073] A non-aqueous electrolyte secondary battery was manufactured using the same method as in Example 1, except that the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 0.5 turns and 0.5 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0074] <Comparative Example 3>

[0075] A non-aqueous electrolyte secondary battery was manufactured using the same method as in Example 1, except that the length (B) of the negative electrode mixture layer formed on the outer surface of the negative electrode core body in the non-opposing portion of the mixture and the length (A) of the negative electrode mixture layer formed on the inner surface of the negative electrode core body in the winding direction were set to 1.25 turns and 1.25 turns respectively along the winding direction of the non-opposing portion of the mixture.

[0076] [Circularity of the winding core of the electrode body]

[0077] The non-aqueous electrolyte secondary batteries of each embodiment and each comparative example were observed in cross section near the winding center of the electrode body using an X-ray CT device (manufactured by Shimadzu Corporation, SMX-225CT FPD HR). Thereafter, the length (circumference) of the innermost circumference of the positive electrode and the area surrounded by the innermost circumference of the positive electrode were measured, and the circularity of the winding core of the electrode body was calculated (4π×area / (circumference^2)).

[0078] [Evaluation of plate deformation]

[0079] The non-aqueous electrolyte secondary battery of each embodiment and each comparative example was charged at a constant current of 0.3It until the battery voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current reached 0.02It. Thereafter, it was discharged at a constant current of 1.0It until the battery voltage reached 2.7V. This charge and discharge was defined as one cycle, and 500 cycles were performed while inserting a 20-minute rest period between each cycle. After 500 cycles, the non-aqueous electrolyte secondary battery was charged at a constant current of 0.3It until the battery voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current reached 0.02It to set it to a charged state. An X-ray CT device (manufactured by Shimadzu Corporation, SMX-225CT FPD HR) was used to observe the cross-section of the non-aqueous electrolyte secondary battery in the charged state near the winding center of the electrode body. Thereafter, as Figure 4 As shown, when deformation (bending) of the electrode plate (at least one of the positive electrode 11 and the negative electrode 12) at an angle θ of 150° or less was confirmed at the portion where the positive electrode and the negative electrode faced each other, it was determined that the electrode plate was deformed, and the presence or absence of electrode plate deformation was evaluated. The number of batteries evaluated was 20.

[0080] The evaluation results of the circularity of the winding core of the electrode assembly and the electrode plate deformation of each example and each comparative example are summarized in Table 1. The evaluation results of the circularity of the winding core of the electrode assembly are relatively shown with the circularity of the winding core of the electrode assembly of Comparative Example 3 as the reference (100%).

[0081] [Table 1]

[0082]

[0083] In Comparative Examples 1 to 3, although the circularity of the winding core of the electrode body is as high as 85% or more, the pole plate deformation is more than 6 / 20, which is a high incidence. On the other hand, in Examples 1 to 7, the circularity of the winding core is all above 89%, which can be said to maintain a high circularity. In addition, in Examples 1 to 7, the pole plate deformation is less than 4 / 20, which is a low incidence. According to these results, in the non-opposing portion of the negative electrode mixture, by making the length of the winding direction of the negative electrode mixture layer formed on the inner circumferential surface of the negative electrode core body more than 0.3 turns along the winding direction of the non-opposing portion of the mixture, and the length of the winding direction of the negative electrode mixture layer formed on the outer circumferential surface of the negative electrode core body is less than 2 / 3 of the length of the winding direction of the negative electrode mixture layer formed on the inner circumferential surface of the negative electrode core body, it is possible to maintain the circularity of the winding core of the electrode body while suppressing the deformation of the pole plate at the portion where the positive electrode and the negative electrode face each other.

[0084] [appendix] (1)

[0086] A non-aqueous electrolyte secondary battery comprises an electrode body formed by winding a positive electrode and a negative electrode sandwich having a negative electrode mixture layer formed on a negative electrode core with a separator interposed therebetween, and a non-aqueous electrolyte.

[0087] The negative electrode has a non-opposing portion that does not face the positive electrode through the separator at the inner end side of the winding direction of the electrode body.

[0088] The non-opposing portion includes, on at least one surface of the negative electrode core body, a mixture non-opposing portion where the negative electrode mixture layer is formed from an outer end of the non-opposing portion in a winding direction toward an inner side in a winding direction.

[0089] In the mixture non-opposing portion, the length in the winding direction of the negative electrode mixture layer formed on the inner peripheral surface of the negative electrode core body facing the radial inner side of the electrode body is more than 0.3 turns along the winding direction of the mixture non-opposing portion.

[0090] The winding length of the negative electrode mixture layer formed on the outer peripheral surface of the negative electrode core body toward the radial outer side of the electrode body is less than 2 / 3 of the winding length of the negative electrode mixture layer formed on the inner peripheral surface of the negative electrode core body. (2)

[0092] According to the non-aqueous electrolyte secondary battery described in (1) above, wherein, in the above-mentioned mixture non-opposing portion, the length of the negative electrode mixture layer formed on the inner circumferential surface of the above-mentioned negative electrode core body in the winding direction is greater than 0.7 turns and less than 1.0 turns along the winding direction of the above-mentioned mixture non-opposing portion, and the length of the negative electrode mixture layer formed on the outer circumferential surface of the above-mentioned negative electrode core body in the winding direction is greater than 0.3 turns and less than 0.6 turns along the winding direction of the mixture non-opposing portion. (3)

[0094] The nonaqueous electrolyte secondary battery according to (1) or (2), wherein the non-opposing portion comprises a core material non-opposing portion where the negative electrode mixture layer is not formed on both surfaces of the negative electrode core body.

[0095] The core material non-opposing portion is wound more than 0.5 turns from the inner end in the winding direction of the mixture non-opposing portion toward the inner side in the winding direction. (4)

[0097] The nonaqueous electrolyte secondary battery according to the above (3) includes a negative electrode lead connected to the negative electrode core body at the core material non-opposing portion. (5)

[0099] The nonaqueous electrolyte secondary battery according to any one of (1) to (4) above, wherein the negative electrode mixture layer contains a Si-based material.

[0100] The content of the Si-based material is 5% by mass or more based on the total mass of the negative electrode mixture layer.

[0101] Description of Reference Numerals

[0102] 10 non-aqueous electrolyte secondary battery, 11 positive electrode, 12 negative electrode, 12a non-opposing portion, 12b opposing portion, 12c mixture non-opposing portion, 12d core material non-opposing portion, 13 separator, 14 electrode body, 15 battery case, 16 case body, 17 sealing body, 18a, 18b insulating plate, 19 positive electrode lead, 20a, 20b negative electrode lead, 21 protrusion, 22 filter, 23 lower valve body, 24 insulating member, 25 upper valve body, 26 cover, 27 gasket, 30 negative electrode core body, 30a inner peripheral surface, 30b outer peripheral surface, 32, 32a, 32b negative electrode mixture layer.

Claims

1. A non-aqueous electrolyte secondary battery comprising an electrode body formed by winding a positive electrode and a negative electrode sandwich having a negative electrode mixture layer formed on a negative electrode core with a separator interposed therebetween, and a non-aqueous electrolyte, The negative electrode has a non-opposing portion on the inner end side of the electrode body in the winding direction that does not face the positive electrode through the separator. The non-opposing portion includes, on at least one surface of the negative electrode core body, a mixture non-opposing portion where the negative electrode mixture layer is formed from an outer end of the non-opposing portion in the winding direction toward an inner side in the winding direction. In the mixture non-opposing portion, the length in the winding direction of the negative electrode mixture layer formed on the inner peripheral surface of the negative electrode core body facing the radial inner side of the electrode body is more than 0.3 turns along the winding direction of the mixture non-opposing portion, The winding length of the negative electrode mixture layer formed on the outer peripheral surface of the negative electrode core body toward the radial outer side of the electrode body is less than 2 / 3 of the winding length of the negative electrode mixture layer formed on the inner peripheral surface of the negative electrode core body.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein In the non-opposing portion of the mixture, the length of the negative electrode mixture layer formed on the inner circumferential surface of the negative electrode core in the winding direction is greater than 0.7 turns and less than 1.0 turns along the winding direction of the non-opposing portion of the mixture, and the length of the negative electrode mixture layer formed on the outer circumferential surface of the negative electrode core in the winding direction is greater than 0.3 turns and less than 0.6 turns along the winding direction of the non-opposing portion of the mixture.

3. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein: The non-opposing portion includes a core material non-opposing portion on both surfaces of the negative electrode core body where the negative electrode mixture layer is not formed. The core material non-opposing portion is wound more than 0.5 turns from the inner end of the mixture non-opposing portion in the winding direction toward the inner side in the winding direction. 4 . The nonaqueous electrolyte secondary battery according to claim 3 , further comprising a negative electrode lead connected to the negative electrode core body at the core material non-opposing portion.

5. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein: The negative electrode mixture layer includes Si-based materials, The content of the Si-based material is 5 mass % or more relative to the total mass of the negative electrode mixture layer.

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