Nonaqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery (10) according to one embodiment of the present disclosure is provided with: an electrode body (14) in which a positive electrode (11) and a negative electrode (12) are wound with a separator (13) therebetween; a bottomed cylindrical outer can (20) that houses the electrode body (14); a sealing body (19) that seals the opening of the outer can (20); an insulating plate (16) positioned between the electrode body (14) and the bottom (21) of the outer can (20); and a spacer (28) positioned between the insulating plate (16) and the bottom (21) of the outer can (20), the sealing body (19) having a relief valve for releasing the internal pressure when the internal pressure of the outer can (20) rises to a predetermined level or more, and the spacer (28) having a plurality of grooves (29) extending in one direction on at least one surface of the insulating plate (16) side. The plurality of grooves (29) are formed at intervals from each other in another direction orthogonal to the one direction.

Description

Technical Field

[0001] The present disclosure relates to a nonaqueous electrolyte secondary battery. Background Art

[0002] Conventionally, non-aqueous electrolyte secondary batteries, such as lithium-ion secondary batteries, are known. These batteries include an electrode assembly (wound body) formed by winding a positive electrode and a negative electrode with a separator interposed therebetween, and an outer canister for storing the electrode assembly and an electrolyte solution. Patent Documents 1 and 2 disclose non-aqueous electrolyte secondary batteries in which a space is provided below the battery by forming a step at the bottom of the outer canister.

[0003] Prior art literature

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-57245

[0005] Patent Document 2: Japanese Patent No. 4321027 Summary of the Invention

[0006] In non-aqueous electrolyte secondary batteries, when the battery overheats abnormally, it is crucial to smoothly discharge the high-temperature gases inside the battery. However, repeated charge and discharge cycles cause the negative electrode active material to expand and contract, causing the electrode assembly to expand in the vertical direction of the battery. This can block the high-temperature gas exhaust path at the bottom of the battery, potentially preventing smooth exhaust.

[0007] The non-aqueous electrolyte secondary batteries disclosed in Patent Documents 1 and 2 have a space provided at the bottom of the battery. However, in the structures disclosed in Patent Documents 1 and 2, when the electrode body expands in the longitudinal direction of the battery due to charging and discharging, stress tends to concentrate on the step difference portion formed at the bottom of the outer can. If stress concentration occurs, the positive and negative electrode plates constituting the electrode body will deform, potentially causing an internal short circuit. Therefore, the purpose of the present disclosure is to provide a non-aqueous electrolyte secondary battery that can suppress internal short circuits and smoothly discharge high-temperature gases inside the battery to the outside of the battery when the battery is abnormally heated.

[0008] A non-aqueous electrolyte secondary battery according to a technical solution of the present disclosure comprises: an electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween; an outer can in a bottomed cylindrical shape for housing the electrode body; a sealing body for sealing an opening of the outer can; an insulating plate located between the electrode body and the bottom of the outer can; and a spacer located between the insulating plate and the bottom of the outer can, wherein the sealing body has a safety valve for releasing the internal pressure of the outer can when the internal pressure of the outer can rises above a specified level, and the spacer has a plurality of grooves extending in one direction on a surface on the side of the insulating plate, and the plurality of grooves are arranged at intervals from each other in other directions orthogonal to the one direction.

[0009] In addition, another technical solution of the present invention is a non-aqueous electrolyte secondary battery comprising: an electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween; an outer can with a bottom and a cylindrical shape for accommodating the electrode body; a sealing body for sealing the opening of the outer can; and an insulating plate located between the electrode body and the bottom of the outer can, the sealing body having a safety valve for releasing the internal pressure of the outer can when the internal pressure of the outer can rises above a specified level, and a plurality of grooves extending in one direction are provided on at least one of a surface on the bottom side of the outer can and an inner surface of the bottom of the outer can, the plurality of grooves being arranged at intervals from each other in other directions orthogonal to the one direction.

[0010] According to the nonaqueous electrolyte secondary battery of the present disclosure, it is possible to suppress internal short circuits and, when the battery generates abnormal heat, to smoothly discharge high-temperature gas inside the battery to the outside of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view of a nonaqueous electrolyte secondary battery as an example of an embodiment.

[0012] Figure 2 yes Figure 1 A plan view of an insulating plate included in a non-aqueous electrolyte secondary battery.

[0013] Figure 3 It is a top view of an insulating plate as another example of the embodiment.

[0014] Figure 4 It is a top view of an insulating plate as another example of the embodiment.

[0015] Figure 5 yes Figure 1 A plan view of a separator included in a non-aqueous electrolyte secondary battery.

[0016] Figure 6 is Figure 1 An enlarged perspective view of a groove formed in a separator included in a non-aqueous electrolyte secondary battery.

[0017] Figure 7 is a cross-sectional view of a nonaqueous electrolyte secondary battery as another example of the embodiment.

[0018] Figure 8 is a cross-sectional view of a nonaqueous electrolyte secondary battery as another example of the embodiment. DETAILED DESCRIPTION

[0019] An example of an embodiment of a non-aqueous electrolyte secondary battery according to the present disclosure is described in detail below with reference to the accompanying drawings. The embodiment described below is merely an example, and the present disclosure is not limited to the following embodiment. In addition, solutions formed by selectively combining the components of the embodiments described below are also included in the present disclosure.

[0020] The following illustrates a cylindrical battery in which a wound electrode body is housed in a bottomed cylindrical outer can. However, the outer can of the battery is not limited to a cylindrical outer can. For example, it may be a square outer can (square battery), a coin-shaped outer can (coin-shaped battery), or an outer can composed of a laminated sheet including a metal layer and a resin layer (laminated battery).

[0021] Figure 1 1 is a diagram schematically showing a cross section of a non-aqueous electrolyte secondary battery (hereinafter referred to as a battery) 10 as an example of an embodiment. Figure 1 As shown, the battery 10 includes an electrode body 14, a non-aqueous electrolyte (not shown), and an outer can 20 for storing the electrode body 14 and the non-aqueous electrolyte. The electrode body 14 includes a positive electrode 11, a negative electrode 12, and a separator 13, and has a structure in which the positive electrode 11 and the negative electrode 12 are wound in a spiral shape with the separator 13 interposed therebetween. The outer can 20 is a metal container with a bottom and a cylindrical shape that is open on one side in the axial direction, and the opening of the outer can 20 is blocked by a sealing body 19. In this embodiment, the sealing body 19 has a safety valve that releases the internal pressure of the outer can 20 when the internal pressure of the outer can 20 rises to or above a specified level, and the details will be described later. In the following, the sealing body 19 side of the battery 10 in the axial direction (height direction) is set as "upper", and the bottom 21 side of the outer can 20 in the axial direction is set as "lower".

[0022] The non-aqueous electrolyte has lithium ion conductivity and may be a liquid electrolyte (electrolyte) or a solid electrolyte.

[0023] Liquid electrolyte (electrolyte) contains non-aqueous solvent and electrolyte salt dissolved in the non-aqueous solvent. Non-aqueous solvent can use esters, ethers, nitriles, amides and mixed solvents of two or more thereof, etc. As an example of non-aqueous solvent, ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixed solvents thereof, etc. can be cited. Non-aqueous solvent can contain halogen substitution (such as fluoroethylene carbonate, etc.) in which at least a portion of hydrogen of these solvents is substituted with halogen atoms such as fluorine. Electrolyte salt, for example, uses lithium salts such as LiPF6.

[0024] As a solid electrolyte, for example, a solid or gel-like polymer electrolyte, an inorganic solid electrolyte, etc. can be used. As an inorganic solid electrolyte, well-known materials in all-solid lithium-ion secondary batteries, etc. (such as oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. The polymer electrolyte, for example, comprises a lithium salt and a matrix polymer, or comprises a non-aqueous solvent, a lithium salt, and a matrix polymer. As the matrix polymer, for example, a polymer material that absorbs a non-aqueous solvent and gels is used. As polymer materials, fluororesins, acrylic resins, polyether resins, etc. can be cited.

[0025] The positive electrode 11, negative electrode 12, and separator 13 that constitute the electrode body 14 are all strip-shaped elongated bodies, which are alternately stacked in the radial direction of the electrode body 14 by being wound into a spiral. In order to prevent the precipitation of lithium, the negative electrode 12 is formed to be one circle larger than the positive electrode 11. In other words, the negative electrode 12 is formed to be longer than the positive electrode 11 in the length direction and the width direction (short side direction). The separator 13 is formed to be at least one circle larger than the positive electrode 11, and two sheets are arranged in a manner of sandwiching the positive electrode 11. The battery 10 has a first insulating plate 15 and a second insulating plate 16, which are respectively arranged above and below the electrode body 14.

[0026] The positive electrode 11 includes a positive electrode core 40 and a positive electrode mixture layer 41 formed on the positive electrode core 40. The positive electrode core 40 can be made of a foil of a metal that is stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, with a thin film of the metal disposed on the surface. The positive electrode mixture layer 41 contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 can be manufactured, for example, by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, and a binder to the positive electrode core 40, drying the coating, and then compressing it to form the positive electrode mixture layers 41 on both sides of the positive electrode core 40.

[0027] The positive electrode mixture layer 41 contains a particulate lithium metal composite oxide as the positive electrode active material. The lithium metal composite oxide is a composite oxide containing metal elements such as Co, Mn, Ni, and Al in addition to Li. The metal element constituting the lithium metal composite oxide is, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. Among them, it is preferred that it contains at least one selected from Co, Ni, Al, and Mn. As an example of a preferred composite oxide, a lithium metal composite oxide containing Ni, Co, and Mn and a lithium metal composite oxide containing Ni, Co, and Al can be cited.

[0028] Examples of the conductive agent contained in the positive electrode mixture layer 41 include carbon black such as acetylene black and Ketjen black, graphite, carbon nanotubes (CNTs), carbon nanofibers, and carbon materials such as graphene. Examples of the binder contained in the positive electrode mixture layer 41 include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. Furthermore, these resins may be used in combination with carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), and the like.

[0029] The negative electrode 12 includes a negative electrode core 50 and a negative electrode mixture layer 51 formed on the negative electrode core 50. The negative electrode core 50 can be made of a foil of a metal that is stable within the potential range of the negative electrode 12, such as copper or a copper alloy, with a thin film of the metal disposed on the surface. The negative electrode mixture layer 51 contains a negative electrode active material, a binder, and, if necessary, a conductive agent. The negative electrode 12 can be manufactured by applying a negative electrode mixture slurry containing a negative electrode active material and a binder to the surface of the negative electrode core 50, drying the coating, and then compressing it to form the negative electrode mixture layer 51 on both surfaces of the negative electrode core 50.

[0030] The negative electrode mixture layer 51 preferably contains a carbon material and a silicon-containing material as the negative electrode active material. The inclusion of a silicon-containing material facilitates achieving both high capacity and excellent cycle characteristics. For example, the negative electrode mixture layer 51 may contain at least one of an element that alloys with Li, such as Sn, and a material containing the element, as the negative electrode active material.

[0031] From the perspective of high capacity, the content of silicon-containing material is preferably 10% by mass or more of the total mass of the negative electrode active material, more preferably 12% by mass or more, and even more preferably 15% by mass or more. Generally, silicon-containing materials have a larger expansion rate during charge and discharge than carbon materials. Therefore, if charge and discharge are repeated, the electrode body 14 expands in the vertical direction of the battery, and the exhaust path of the high-temperature gas at the bottom of the battery is easily blocked. In this embodiment, since a spacer 28 with multiple grooves 29 is provided, an exhaust path for high-temperature gas can be ensured at the bottom of the battery, and the details will be described later. Therefore, when a silicon-containing material is included as the negative electrode active material, the effect of the present disclosure becomes more significant.

[0032] The carbon material functioning as the negative electrode active material is, for example, at least one selected from natural graphite, artificial graphite, soft carbon, and hard carbon. Among these, the carbon material is preferably at least artificial graphite such as bulk artificial graphite (MAG) and graphitized mesocarbon microbeads (MCMB), natural graphite such as flaky graphite, bulk graphite, and earthy graphite, or a mixture thereof. The volume-based D50 of the carbon material is, for example, 1 μm to 30 μm, preferably 5 μm to 25 μm.

[0033] From the perspective of high capacity, the content of silicon-containing material is preferably 5% by mass or more of the total mass of the negative electrode active material, more preferably 8% by mass or more, and further preferably 10% by mass or more. Generally, silicon-containing materials have a larger volume change during charge and discharge than carbon materials. Therefore, in the case of containing silicon-containing material as the negative electrode active material, if charge and discharge are repeated, the electrode body 14 further expands in the up and down directions of the battery, and the exhaust path of the high-temperature gas is easily blocked. In this embodiment, since a spacer 28 having a plurality of grooves 29 is provided at the lower part of the battery, the exhaust path of the high-temperature gas can be ensured, and the details will be described later. Therefore, in the case of containing silicon-containing material as the negative electrode active material, the effect of the present disclosure becomes more significant.

[0034] Preferred silicon-containing materials (composite materials) are composite particles comprising an ion-conducting phase, a Si phase dispersed within the ion-conducting phase, and a conductive layer covering the surface of the ion-conducting phase. The ion-conducting phase is, for example, at least one selected from a silicate phase, an amorphous carbon phase, a silicide phase, and a silicon oxide phase. The Si phase is formed by dispersing Si in fine particles. The ion-conducting phase is a continuous phase composed of a collection of particles finer than the Si phase. The conductive layer is composed of a material with a higher conductivity than the ion-conducting phase and forms a good conductive path in the negative electrode mixture layer 51.

[0035] An example of a preferred composite material containing Si is a composite material having a sea-island structure in which fine Si is dispersed substantially uniformly in an amorphous silicon oxide phase, and is represented as a whole by the general formula SiO x Composite particles represented by (0<x≤2). The main component of silicon oxide may be silicon dioxide. The content ratio (x) of oxygen to Si is, for example, 0.5≤x<2.0, preferably 0.8≤x≤1.5.

[0036] The binder contained in the negative electrode mixture layer 51 is the same as that in the positive electrode mixture layer 41. Fluorine-containing resins, PAN, polyimide, acrylic resins, polyolefins, etc. can be used, but styrene-butadiene rubber (SBR) is preferably used. In addition, the negative electrode mixture layer 51 preferably contains CMC or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol (PVA), etc. Among them, SBR and CMC or its salts, PAA or its salts, etc. are preferably used in combination. The negative electrode mixture layer 51 may also contain a conductive agent such as CNT.

[0037] The separator 13 uses a porous sheet having ion permeability and insulation. Specific examples of the porous sheet include microporous films, woven fabrics, non-woven fabrics, and the like. The material of the separator 13 is preferably a polyolefin such as polyethylene or polypropylene, or cellulose. The separator 13 may be a single-layer structure or a multi-layer structure. Furthermore, a heat-resistant resin layer such as an aromatic polyamide resin may be formed on the surface of the separator 13. A filler layer containing an inorganic filler may be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.

[0038] The positive electrode lead 17 is connected to the positive electrode 11, and the negative electrode lead 18 is connected to the winding end of the negative electrode 12. The positive electrode lead 17 extends through the through-hole of the first insulating sheet 15 to the sealing body 19, while the negative electrode lead 18 extends from the outside of the second insulating sheet 16 to the bottom 21 of the outer can 20. The positive electrode lead 17 is connected to the lower surface of the internal terminal plate 24 of the sealing body 19 by welding or the like, and the sealing body 19 serves as the positive electrode terminal. The negative electrode lead 18 is connected to the inner surface of the bottom 21 of the metal outer can 20 by welding or the like, and the outer can 20 serves as the negative electrode terminal.

[0039] The outer can 20 is a metal container with a bottomed cylindrical shape and an open vertical side. The outer can 20 has a bottom 21 and a side wall 22. The side wall 22 is the portion of the outer can 20 excluding the bottom 21 and is formed with a groove 23, which will be described later.

[0040] A gasket 27 is provided between the outer can 20 and the sealing body 19 to ensure the airtightness of the interior of the battery and the insulation between the outer can 20 and the sealing body 19. A groove 23 is formed in the outer can 20, in which a portion of the side wall 22 extends inward and supports the sealing body 19. The groove 23 is preferably formed in an annular shape along the circumference of the outer can 20, and supports the sealing body 19 on its upper surface. The sealing body 19 is fixed to the upper part of the outer can 20 by the groove 23 and the open end of the outer can 20 riveted to the sealing body 19.

[0041] The sealing member 19 is a disc-shaped component equipped with a safety valve. The sealing member 19 has a structure in which an internal terminal plate 24, an insulating member 25, and a rupture plate 26 are stacked in this order from the electrode body 14 side. The internal terminal plate 24 is a metal plate consisting of a thick outer peripheral portion 24A for connecting to the positive lead 17, and a thinner central portion 24B that separates from the outer peripheral portion 24A when the internal pressure of the battery exceeds a predetermined threshold. Multiple vent holes 24C are formed in the outer peripheral portion 24A.

[0042] The rupture plate 26 is arranged opposite to the internal terminal plate 24 via the insulating component 25. An opening portion 25A is formed in the radial center portion of the insulating component 25, and a vent hole 25B is formed in the portion overlapping with the vent hole 24C of the internal terminal plate 24. The rupture plate 26 has a valve portion 26A that ruptures when the internal pressure of the battery 10 exceeds a predetermined threshold value, and the valve portion 26A is connected to the central portion 24B of the internal terminal plate 24 by welding or the like. The insulating component 25 insulates the portion other than the connection portion between the central portion 24B and the valve portion 26A. In addition, the outer peripheral portion of the rupture plate 26 surrounding the valve portion 26A is retained between the rivet portion formed by bending the opening of the outer can 20 inward and the groove portion 23 via a gasket 27.

[0043] The valve portion 26A includes a joint portion provided in the radial center and protruding toward the inside of the battery, and a thin-walled portion formed around the joint portion, and is formed in the radial center of the rupture plate 26. The joint portion of the valve portion 26A passes through the opening 25A of the insulating component 25 and is joined to the central portion 24B. When an abnormality occurs in the battery 10 and the internal pressure rises, the rupture plate 26 is pressed upward by the generated high-temperature gas, the internal terminal plate 24 ruptures, the central portion 24B separates from the outer peripheral portion 24A, and the valve portion 26A deforms to protrude toward the outside of the battery. As a result, the current path in the sealing body 19 is cut off. Furthermore, after the current path is cut off, when the internal pressure of the battery 10 further rises, the thin-walled portion of the valve portion 26A ruptures, forming a gas discharge port on the rupture plate 26.

[0044] In addition, the structure of the sealing body 19 is not limited to Figure 1 The sealing member 19 may have a laminated structure including two valve members, or may have a convex sealing member cover covering the valve member.

[0045] The battery 10 further includes a first insulating plate 15 disposed between the electrode body 14 and the sealing member 19, a second insulating plate 16 disposed between the electrode body 14 and the bottom 21, and a spacer 28 located between the second insulating plate 16 and the bottom 21. In this embodiment, a plurality of grooves 29 are formed on the upper surface of the spacer 28, details of which will be described later.

[0046] The first insulating plate 15 prevents electrical conduction between the negative electrode 12 and the sealing member 19. The shape of the first insulating plate 15 is not particularly limited and may be the same as or different from the shape of the second insulating plate 16 described later.

[0047] Figures 2 to 4A top view showing an example of the second insulating plate 16. The second insulating plate 16 prevents conduction between the positive electrode 11 and the outer can 20. In addition, the second insulating plate 16 plays a role in ensuring an exhaust path when the gas generated inside the battery is discharged to the outside through the safety valve. In this embodiment, the second insulating plate 16 has a circular plate shape. The diameter of the second insulating plate 16 is, for example, slightly smaller than the diameter of the inner surface of the bottom 21. In addition, the second insulating plate 16 is not limited to a circular plate shape, and the outer periphery of the second insulating plate 16 may also have a polygonal shape. In addition, a cutout may be formed in a portion of the outer periphery of the second insulating plate 16.

[0048] The second insulating plate 16 has an opening. The ratio of the area of ​​the opening to the total area of ​​the second insulating plate 16, i.e., the opening ratio, is preferably 10% or more, more preferably 15% or more. In this case, it is easy to ensure an exhaust path when the high-temperature gas generated inside the battery is discharged to the outside of the battery. In addition, the opening ratio of the second insulating plate 16 is preferably 50% or less, more preferably 40% or less. In this case, the strength of the second insulating plate 16 can be ensured, and the deformation and rupture of the second insulating plate 16 due to the expansion of the electrode body 14 accompanying charging and discharging can be suppressed. Therefore, an example of a preferred range of the opening ratio of the second insulating plate 16 is 10% or more and 50% or less, more preferably 15% or more and 40% or less.

[0049] The thickness of the second insulating plate 16 can be, for example, not less than 0.1 mm and not more than 1.0 mm. By setting the thickness of the second insulating plate 16 to be not less than 0.1 mm, deformation of the second insulating plate 16 can be suppressed, thereby enabling smooth discharge of high-temperature gas from the lower portion of the battery. By setting the thickness of the second insulating plate 16 to be not more than 1.0 mm, stress concentration on the electrode body 14 caused by the step difference of the second insulating plate 16 can be suppressed, thereby enabling smooth discharge of high-temperature gas from the lower portion of the battery. The thickness of the second insulating plate 16 is preferably not less than 50% and not more than 500% of the depth of the groove 29 formed in the spacer 28 described later, and more preferably not less than 150% and not more than 400%.

[0050] From the perspective of ensuring the strength of the second insulating plate 16, the Young's modulus of the second insulating plate 16 at 25°C is preferably 10 GPa or greater, more preferably 20 GPa or greater. The upper limit of the Young's modulus of the second insulating plate 16 at 25°C is, for example, 200 GPa. The Young's modulus is measured at 25°C using a compression method (e.g., an ORIENTECH Tensilon universal testing machine). The sample for measuring the Young's modulus can be prepared by cutting the second insulating plate 16 into a predetermined size, or separately using the same material as the second insulating plate 16.

[0051] The material of the second insulating plate 16 is not particularly limited, but is preferably a resin such as polypropylene (PP), polyethylene (PE), or nylon (PA).

[0052] Here, Figures 2 to 4 The shape of the second insulating plate 16 shown will be described.

[0053] Figure 2 The second insulating plate 16 shown has a first opening 16A formed within a range including the center α of the second insulating plate 16, and no openings other than the first opening 16A are formed. Figure 2 In the example shown, the first opening 16A has a substantially circular shape. The diameter D of the first opening 16A is 16A For example, the diameter D of the second insulating plate 16 is 16 In addition, the first opening 16A may have a substantially polygonal shape, for example.

[0054] As described above, the first opening 16A is preferably formed in a range including the center α of the second insulating plate 16, for example, in the middle of the second insulating plate 16. The first opening 16A is a passage for high-temperature gas and is used as a hole for passing a welding rod when the negative electrode lead 18 is welded to the inner surface of the bottom 21. Figure 2 In the illustrated example, the center of the first opening 16A coincides with the center of the second insulating plate 16 .

[0055] Figure 3 The second insulating plate 16 shown has a first opening 16A formed within a range including the center α of the second insulating plate 16 and a plurality of second openings 16B formed around the first opening 16A. Figure 3 In the example shown, six second openings 16B having a smaller diameter than the first openings 16A are formed in the second insulating plate 16. The number of second openings 16B is not particularly limited and may be less than six. The formation of second openings 16B creates multiple high-temperature gas exhaust paths, allowing for smoother exhaust of high-temperature gas from within the battery.

[0056] The second openings 16B may be formed randomly around the first opening 16A, but are preferably formed at equal intervals in a concentric circle centered on the first opening 16A from the perspective of increasing the strength of the second insulating plate 16 and improving the flow of high-temperature gas. Figure 3 In the example shown, six second openings 16B having the same shape and size are formed on an imaginary circle β centered on the center α of the second insulating plate 16. Figure 3In the example shown, the first opening 16A and the second opening 16B have a substantially circular shape, but the present invention is not limited thereto. The first opening 16A and the second opening 16B may have a substantially polygonal shape, for example.

[0057] Figure 4 The second insulating plate 16 shown has a first opening 16A formed within a range including the center α of the second insulating plate 16 and a plurality of elongated third openings 16C formed radially from the center of the first opening 16A in the outer diameter direction. Figure 4 In the example shown, six third openings 16C are formed in the second insulating plate 16. The number of the third openings 16C is not particularly limited and may be less than six. The width W of the third opening 16C is 16C There is no particular limitation, but for example, the diameter D of the first opening 16A is 16A more than 5% and less than 20% of the total amount.

[0058] Further reference below Figure 5 and Figure 6 , the spacer 28 will be described in detail. Figure 5 is a plan view showing the upper surface side of the spacer 28, Figure 6 2 is an enlarged perspective view showing the groove formed on the upper surface side of the spacer 28. Figure 5 In FIG. 1 , the region where the groove 29 is formed is indicated by dotted hatching.

[0059] The spacer 28 is disposed between the second insulating sheet 16 and the bottom portion 21. In this embodiment, the spacer 28 is disposed so as to sandwich the negative electrode lead 18 with the bottom portion 21. However, it may be disposed below the negative electrode lead 18. When the spacer 28 is disposed below the negative electrode lead 18, the negative electrode lead 18 and the spacer 28 are welded. In this embodiment, the spacer 28 and the bottom portion 21 are not fixed together. However, the lower surface of the spacer 28 may be fixed to the bottom portion 21 by bonding, welding, or the like.

[0060] The spacer 28 may be made of a resin such as polypropylene (PP) or polyethylene (PE), but is preferably made of a metal such as aluminum or stainless steel from the viewpoint of ensuring the strength of the spacer 28 .

[0061] In this embodiment, the spacer 28 has a disk shape. The diameter of the spacer 28 is, for example, slightly smaller than the diameter of the inner surface of the bottom portion 21. Furthermore, the spacer 28 is not limited to a disk shape; the outer periphery of the spacer 28 may also have a polygonal shape. Furthermore, a notch may be formed in a portion of the outer periphery of the spacer 28.

[0062] An opening 28A is formed at the center γ of spacer 28. Opening 28A serves as a hole for passing a welding rod when welding negative lead 18 to the inner surface of base 21. In this embodiment, the center of opening 28A coincides with the center γ of spacer 28. The number of openings 28A formed in spacer 28 is not limited to one; two or more openings may be formed. Furthermore, if spacer 28 is positioned below negative lead 18, opening 28A may not be formed in spacer 28.

[0063] The size of the opening 28A is not particularly limited; for example, the diameter of the opening 28A is 30% of the diameter of the spacer 28. Furthermore, from the perspective of easily welding the negative electrode lead 18 to the bottom portion 21, the shape of the opening 28A is preferably substantially the same as that of the first opening 16A formed in the second insulating plate 16.

[0064] The thickness of the spacer 28 is preferably 0.3 mm or more, more preferably 0.5 mm or more. In this case, the strength of the spacer 28 can be ensured, and the deformation and rupture of the spacer 28 caused by the expansion of the electrode body 14 during charging and discharging can be suppressed. In addition, the thickness of the spacer 28 is preferably 2.5 mm or less, more preferably 2.0 mm or less. In this case, the reduction in battery capacity caused by the reduction in the volume of the electrode body 14 can be suppressed. Therefore, an example of a preferred range of the thickness of the spacer 28 is 0.3 mm or more and 2.5 mm or less, more preferably 0.5 mm or more and 2.0 mm or less.

[0065] like Figure 1 and Figure 5 As shown, on the upper surface of the spacer 28, a plurality of grooves extending in one direction are spaced apart from each other in other directions perpendicular to the one direction. By arranging the grooves 29 on the upper surface of the spacer 28, even when the electrode body 14 expands in the vertical direction of the battery 10 due to charging and discharging, a gap 30 can be formed between the second insulating plate 16 and the spacer 28 through the grooves 29. As a result, the high-temperature gas existing in the lower part of the battery flows into the grooves 29 from the opening formed in the second insulating plate 16 or the outside of the second insulating plate 16. In addition, the high-temperature gas flowing into the grooves 29 passes through the space 31 in the central part of the electrode body 14 (see Figure 1 ) is guided to the upper portion of the battery 10 and discharged to the outside of the battery via a safety valve provided on the sealing body 19. Furthermore, by providing a plurality of grooves 29 on the upper surface of the separator 28, the stress applied to the electrode body 14 when the electrode body 14 expands in the vertical direction of the battery 10 due to charge and discharge is dispersed. As a result, internal short circuits caused by deformation of the electrode plates of the positive electrode 11 and the negative electrode 12 constituting the electrode body 14 can be suppressed.

[0066] The grooves 29 are preferably arranged at equal intervals in other directions perpendicular to the one direction in which they extend. In this case, high-temperature gas can be exhausted to the outside of the battery more smoothly, and when the electrode body 14 expands in the vertical direction, the stress applied to the electrode body 14 is more easily dispersed. The interval L between the grooves 29 is 29 There is no particular limitation, and for example, the width W of the groove 29 is 29 The interval L of the groove 29 is greater than 30% and less than 120%. 29 An example is 0.4 mm or more and 1.2 mm or less.

[0067] The groove 29 may be arranged only in a portion of the upper surface of the spacer 28 in a plan view. However, from the viewpoint of significantly exerting the effects of the present disclosure, the groove 29 is preferably arranged over the entire upper surface of the spacer 28 .

[0068] The total area of ​​the grooves 29 is preferably 30% or more of the area of ​​the inner surface of the bottom 21 when viewed from above, and more preferably 40% or more. In this case, when the electrode body 14 expands in the up and down directions, the stress applied to the electrode body 14 is further dispersed. In addition, the total area of ​​the grooves 29 is preferably 70% or less of the area of ​​the inner surface of the bottom 21, and more preferably 60% or less. In this case, it is easy to ensure the exhaust path of the high-temperature gas, and the high-temperature gas inside the battery can be discharged more smoothly. Therefore, an example of a preferred range of the total area of ​​the grooves 29 is 30% or more and 70% or less of the area of ​​the inner surface of the bottom 21, and more preferably 40% or more and 60% or less of the area of ​​the inner surface of the bottom 21.

[0069] The number of protrusions 30 between adjacent grooves 29 is preferably 5 or more per 1 cm in other directions orthogonal to one direction when viewed from above, and more preferably 10 or more. In this case, it is easy to ensure the exhaust path of the high-temperature gas, and the high-temperature gas inside the battery can be discharged more smoothly. In addition, the number of protrusions 30 is preferably 25 or less per 1 cm in other directions, and more preferably 20 or less. In this case, when the electrode body 14 expands in the up and down directions, the stress applied to the electrode body 14 is more easily dispersed. Thus, an example of a preferred range of the number of protrusions 30 per 1 cm in other directions is 5 or more and 25 or less, and more preferably 10 or more and 20 or less.

[0070] like Figure 6 As shown, the width of the groove 29 is substantially constant in the depth direction of the groove 29. In other words, the side surface 32 of the groove 29 is formed perpendicular to the surface of the spacer 28. The shape of the groove 29 is not limited to this, and the side surface 32 may be inclined so that the width of the groove 29 becomes narrower as it goes downward in the depth direction.

[0071] In this embodiment, the depth of the groove 29 is uniform in the plane, but it is not limited to this. For example, the depth of the groove 29 may be uniform as it approaches the center γ of the spacer 28 (see Figure 5 ), making grooves 29 deeper. During repeated charge and discharge, electrode body 14 tends to expand more at the winding start side than at the winding end side. Therefore, by deepening grooves 29 as they approach the center γ of separator 28, gaps 30 are more easily formed at the winding start side of electrode body 14, allowing for smooth discharge of high-temperature gas from within battery 10.

[0072] The depth of the groove 29 is preferably 0.2 mm or more, more preferably 0.3 mm or more. In this case, it is easy to ensure the exhaust path of the high-temperature gas, and the high-temperature gas inside the battery can be discharged more smoothly. In addition, the depth of the groove 29 is preferably 0.7 mm or less, more preferably 0.6 mm or less. In this case, the reduction in battery capacity due to the reduction in the volume of the electrode body 14 can be suppressed. Therefore, an example of a preferred range of the depth of the groove 29 is 0.2 mm or more and 0.7 mm or less, more preferably 0.3 mm or more and 0.6 mm or less.

[0073] Figure 7 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery 10X as another example of the embodiment. Components identical to those of the nonaqueous electrolyte secondary battery 10 are denoted by the same reference numerals as those of the nonaqueous electrolyte secondary battery 10 , and their descriptions are omitted.

[0074] like Figure 7 As shown, the nonaqueous electrolyte secondary battery 10X differs from the nonaqueous electrolyte secondary battery 10 in that the separator 28 is not provided. Furthermore, in the nonaqueous electrolyte secondary battery 10X, a plurality of grooves 29 are formed on the inner surface of the bottom 21 of the outer can 20. By forming the grooves 29 in the bottom 21 without providing the separator 28, the effects of the present disclosure can be achieved while suppressing an increase in manufacturing costs.

[0075] From the viewpoint of ensuring the strength of the bottom portion 21 , the depth of the groove 29 is preferably 60% or less, and more preferably 50% or less, of the thickness of the bottom portion 21 .

[0076] Figure 8 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery 10Y as another example of the embodiment. Components identical to those of the nonaqueous electrolyte secondary battery 10 are denoted by the same reference numerals as those of the nonaqueous electrolyte secondary battery 10 , and their descriptions are omitted.

[0077] like Figure 8As shown, the nonaqueous electrolyte secondary battery 10Y differs from the nonaqueous electrolyte secondary battery 10 in that the spacer 28 is not provided. Furthermore, in the nonaqueous electrolyte secondary battery 10Y, a plurality of grooves 29 are formed on the lower surface of the second insulating plate 16. As with the nonaqueous electrolyte secondary battery 10X, by forming the grooves 29 in the second insulating plate 16 and omitting the spacer 28, the effects of the present disclosure can be achieved while suppressing an increase in manufacturing costs.

[0078] From the viewpoint of ensuring the strength of the second insulating plate 16 , the depth of the groove 29 is preferably 60% or less, and more preferably 50% or less, of the thickness of the second insulating plate 16 .

[0079] Example

[0080] Hereinafter, the present disclosure will be further described with reference to examples, but the present disclosure is not limited to these examples.

[0081] <Example 1>

[0082] [Production of positive electrode]

[0083] Using aluminum-containing lithium nickel cobalt oxide (LiNi 0.88 Co 0.09 Al 0.03 O2) as the positive electrode active material. 100 parts by mass of LiNi 0.88 Co 0.09 Al 0.03 O2, 1.0 parts by mass of acetylene black as a conductive agent, and 0.9 parts by mass of polyvinylidene fluoride (PVDF) as a binder are mixed in a dispersion medium of N-methylpyrrolidone (NMP) to prepare a positive electrode mixture slurry. This mixture is evenly coated on both sides of a 15μm thick aluminum foil positive electrode core. The NMP is then removed in a dryer at 100-150°C, and then compressed using a roller press to produce a positive electrode plate.

[0084] [Production of negative electrode]

[0085] Mix 70 parts by mass of graphite powder and 30 parts by mass of Si oxide. Mix 100 parts by mass of the negative electrode active material, 1 part by mass of CMC as a thickener, and 1 part by mass of styrene-butadiene rubber as a binder in water to prepare a negative electrode mixture slurry. Apply the negative electrode mixture slurry to both sides of the negative electrode core made of 8 μm thick copper foil to form a negative electrode mixture layer. After drying, compress the negative electrode with a compression roller to a thickness of 0.160 mm to produce the negative electrode.

[0086] [Preparation of non-aqueous electrolyte]

[0087] A non-aqueous electrolyte was prepared by dissolving LiPF6 at a concentration of 1.2 mol / L in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a volume ratio of 3:3:4 (25° C.).

[0088] [Fabrication of non-aqueous electrolyte secondary battery]

[0089] After housing a spacer formed with multiple grooves made of nickel steel in an outer can with a bottom made of low-carbon steel and a bottom diameter of 21 mm, the insulating plate, electrode body and non-aqueous electrolyte are housed in the outer can. Then, the outer can is spun to form a groove portion. An internal terminal plate is arranged on the groove portion via a gasket, and the positive electrode lead is ultrasonically welded to the upper surface of the internal terminal plate. Then, after degassing under reduced pressure, a rupture plate is arranged on the internal terminal plate, and the rupture plate and the internal terminal plate are welded. Finally, the upper end of the outer can is riveted to obtain a non-aqueous electrolyte secondary battery. In addition, the inner terminal plate, the rupture plate and the gasket constitute Figure 1 The closure body shown includes a safety valve.

[0090] Here, the details of the spacer are as follows. In addition, the following grooves are formed in the entire area of ​​the upper surface of the spacer. Figure 5 and Figure 6 The morphogenesis shown.

[0091] Diameter: 18mm, thickness: 0.4mm

[0092] Groove depth: 0.2mm

[0093] Groove area: 30% of the inner surface area of ​​the outer tank bottom

[0094] The details of the insulating plate (second insulating plate) provided between the electrode assembly and the bottom of the outer can are as follows. Figure 2 The opening shown.

[0095] Diameter: 28mm, thickness: 0.2mm

[0096] Material: Polypropylene (PP)

[0097] Opening shape: An opening with a diameter of 5 mm is formed in the center of the insulating plate.

[0098] <Example 2>

[0099] A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the separator was changed to the following separator.

[0100] Diameter: 18mm, thickness: 0.4mm

[0101] Groove area: 0.2mm

[0102] Groove area: 70% of the inner surface area of ​​the outer tank bottom

[0103] Comparative Example

[0104] In the production of the non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that no separator was provided.

[0105] [Fire test]

[0106] Three batteries of Examples 1, 2, and the comparative example were prepared, and each was charged at a constant current of 0.2 It at a temperature of 25°C until the battery voltage reached 4.2 V. Constant voltage charging was then performed at 4.2 V until the current value reached 1 / 100 It. Then, constant current discharge was performed at a constant current of 0.2 It until the battery voltage reached 2.5 V. This charge and discharge cycle was repeated 10 times. Then, constant current charging was performed at a constant current of 0.2 It until the battery voltage reached 4.2 V.

[0107] Then, charged batteries were placed in copper tubes equipped with heaters and heated by the heater, causing the batteries to ignite. After the ignition, the sides of the battery cans were visually inspected for cracks. The results are shown in Table 1.

[0108] Table 1

[0109]

[0110] As shown in Table 1, the comparative example battery exhibited ruptures in the can side, whereas no ruptures were observed in the can side during a battery fire in the batteries of Examples 1 and 2. This is presumably because the provision of a spacer with multiple grooves creates a gap at the bottom of the battery, allowing high-temperature gases to be guided through this gap to the top of the battery during a battery fire, where they are then discharged to the outside through the safety valve. On the other hand, the comparative example battery is suspected of not having a sufficient exhaust path at the bottom of the battery. Consequently, high-temperature gases were not adequately discharged to the outside through the safety valve during a battery fire, leading to ruptures in the can side and the release of high-temperature gases from the sides.

[0111] The present disclosure is further illustrated by the following embodiments.

[0112] Technical structure 1: A non-aqueous electrolyte secondary battery, comprising: an electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween; an outer can with a bottomed cylindrical shape to accommodate the electrode body; a sealing body that seals the opening of the outer can; an insulating plate located between the electrode body and the bottom of the outer can; and a spacer located between the insulating plate and the bottom of the outer can, the sealing body having a safety valve for releasing the internal pressure of the outer can when the internal pressure of the outer can rises to or above a specified level, the spacer having a plurality of grooves extending in one direction on a surface on the side of the insulating plate, the plurality of grooves being arranged at intervals from each other in other directions orthogonal to the one direction.

[0113] Technical configuration 2: A non-aqueous electrolyte secondary battery, comprising: an electrode body formed by winding a positive electrode and a negative electrode with a separator interposed therebetween; an outer can in a bottomed cylindrical shape for housing the electrode body; a sealing body for sealing the opening of the outer can; and an insulating plate located between the electrode body and the bottom of the outer can, the sealing body having a safety valve for releasing the internal pressure of the outer can when the internal pressure of the outer can rises above a specified level, the insulating plate having a plurality of grooves extending in one direction on at least one of a surface on the bottom side of the outer can and an inner surface of the bottom of the outer can, the plurality of grooves being arranged at intervals from each other in other directions orthogonal to the one direction.

[0114] Technical Configuration 3: The nonaqueous electrolyte secondary battery according to Technical Configuration 1 or 2, wherein the depth of the plurality of grooves is 0.2 mm or more and 0.7 mm or less.

[0115] Technical Configuration 4: The nonaqueous electrolyte secondary battery according to any one of Technical Configurations 1 to 3, wherein the total area of ​​the plurality of grooves, when viewed from above, is 30% to 70% of the area of ​​the inner surface of the bottom of the outer can.

[0116] Technical Configuration 5: The nonaqueous electrolyte secondary battery according to any one of Technical Configurations 1 to 4, wherein the number of protrusions between adjacent grooves in the other direction is 5 or more and 25 or less per cm when the grooves are viewed from above.

[0117] Technical Configuration 6: The nonaqueous electrolyte secondary battery according to any one of Technical Configurations 1 to 5, wherein the plurality of grooves are arranged at equal intervals from each other in the other direction.

[0118] Technical Configuration 7: The nonaqueous electrolyte secondary battery according to any one of Technical Configurations 1 to 6, wherein the insulating plate has a thickness of 0.1 mm to 1.0 mm.

[0119] Technical Configuration 8: The nonaqueous electrolyte secondary battery according to any one of Technical Configurations 1 to 7, wherein the insulating plate has an opening, and an aperture ratio (a ratio of an area of ​​the opening to a total area of ​​the insulating plate) is 10% to 50%.

[0120] Technical Configuration 9: According to the nonaqueous electrolyte secondary battery of Technical Configuration 9, the opening portion includes: a first opening portion formed in a range including the center of the insulating plate; and a plurality of second opening portions formed around the first opening portion.

[0121] Technical Configuration 10: The nonaqueous electrolyte secondary battery according to Technical Configuration 9, wherein the second openings are formed at equal intervals in a concentric circle shape centered on the first opening.

[0122] Technical Configuration 11: The nonaqueous electrolyte secondary battery according to Technical Configuration 8, wherein the opening portion includes: a first opening portion formed within a range including the center of the insulating plate; and a plurality of third opening portions formed radially from the center of the first opening portion.

[0123] Technical Configuration 12: The nonaqueous electrolyte secondary battery according to any one of Technical Configurations 1 to 11, wherein the negative electrode comprises a negative electrode core and a negative electrode mixture layer formed on the negative electrode core, and the negative electrode mixture layer contains a silicon-containing material as the negative electrode active material.

[0124] Technical Configuration 13: The non-aqueous electrolyte secondary battery according to Technical Configuration 12, wherein the content of the silicon-containing material is 10% by mass or more of the total mass of the negative electrode active material.

[0125] Description of Reference Numerals

[0126] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 First insulating plate, 16 Second insulating plate (insulating plate), 16A First opening, 16B Second opening, 16C Third opening, 17 Positive electrode lead, 18 Negative electrode lead, 19 Sealing member, 20 Outer can, 21 Bottom, 22 Side wall, 23 Groove, 24 Internal terminal plate, 24A Outer periphery, 24B Central portion, 24C Vent, 25 Insulating member, 25A Opening, 25B Vent, 26 Rupturable plate, 26A Valve portion, 27 Gasket, 28 Spacer, 28A Opening, 29 Groove, 30 Protrusion, 31 Space, 32 Side, 40 Positive electrode core, 41 Positive electrode mixture layer, 50 Negative electrode core, 51 Negative electrode mixture layer, α and γ centers, β imaginary circle.

Claims

1. A non-aqueous electrolyte secondary battery comprising: The positive electrode and the negative electrode are wound together with a separator; An outer container having a bottom and a cylindrical shape for accommodating the electrode assembly; a sealing body for sealing the opening of the outer can; an insulating plate positioned between the electrode body and the bottom of the outer can; and a spacer located between the insulating plate and the bottom of the outer tank, The sealing body has a safety valve for releasing the internal pressure of the outer tank when the internal pressure rises to a predetermined level or higher. The spacer has a plurality of grooves extending in one direction on the surface of the insulating plate side. The plurality of grooves are arranged at intervals from each other in another direction perpendicular to the one direction.

2. A non-aqueous electrolyte secondary battery comprising: The positive electrode and the negative electrode are wound together with a separator; An outer container having a bottom and a cylindrical shape for accommodating the electrode assembly; a sealing body for sealing the opening of the outer can; and an insulating plate located between the electrode body and the bottom of the outer can, The sealing body has a safety valve for releasing the internal pressure of the outer tank when the internal pressure rises to a predetermined level or higher. The insulating plate has a plurality of grooves extending in one direction on at least one of a surface on the bottom side of the outer can and an inner surface of the bottom of the outer can. The plurality of grooves are arranged at intervals from each other in another direction perpendicular to the one direction.

3. The nonaqueous electrolyte secondary battery according to claim 1 or 2, The depth of the plurality of grooves is greater than or equal to 0.2 mm and less than or equal to 0.7 mm.

4. The nonaqueous electrolyte secondary battery according to claim 1 or 2, When the plurality of grooves are viewed in plan from above, the total area of ​​the plurality of grooves is 30% to 70% of the area of ​​the inner surface of the bottom of the outer can.

5. The nonaqueous electrolyte secondary battery according to claim 1 or 2, When the plurality of grooves are viewed planarly from above, the number of convex portions between adjacent grooves is 5 or more and 25 or less per 1 cm in the other direction.

6. The nonaqueous electrolyte secondary battery according to claim 1 or 2, The plurality of grooves are arranged at equal intervals from one another in the other direction.

7. The nonaqueous electrolyte secondary battery according to claim 1 or 2, The insulating plate has a thickness of 0.1 mm or more and 1.0 mm or less.

8. The nonaqueous electrolyte secondary battery according to claim 1 or 2, The insulating plate has an opening. The ratio of the area of ​​the opening to the total area of ​​the insulating plate, that is, the opening ratio, is 10% or more and 50% or less.

9. The nonaqueous electrolyte secondary battery according to claim 8, The opening has: a first opening formed in a range including the center of the insulating plate; and A plurality of second openings are formed around the first opening.

10. The nonaqueous electrolyte secondary battery according to claim 9, The second openings are formed at equal intervals in a concentric circle shape centered on the first opening.

11. The nonaqueous electrolyte secondary battery according to claim 8, The opening has: a first opening formed in a range including the center of the insulating plate; and A plurality of third openings are formed radially from the center of the first opening.

12. The nonaqueous electrolyte secondary battery according to claim 1 or 2, The negative electrode includes a negative electrode core and a negative electrode mixture layer formed on the negative electrode core. The negative electrode mixture layer contains a silicon-containing material as a negative electrode active material.

13. The nonaqueous electrolyte secondary battery according to claim 12, The content of the silicon-containing material is 10% by mass or more of the total mass of the negative electrode active material.

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