Non-aqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery (10) characterized by comprising: an electrode body (14); a bottomed cylindrical outer can (20) containing a first metal material; and a closure body (30) that closes an opening portion (24) of the outer can (20), an annular groove (23) recessed toward a radial inner side of the outer can being provided in a side surface of the outer can (20) on the opening portion (24) side, a protective member (40) containing a second metal material being provided inside the annular groove (23) and abutting against at least a part of a surface of the annular groove (23), the second metal material having a melting point lower than a melting point of the first metal material and being 500°C or lower.

Description

Technical Field

[0001] This disclosure relates to non-aqueous electrolyte secondary batteries. Background Technology

[0002] Previously, a non-aqueous electrolyte secondary battery was known, comprising: an electrode body having a positive electrode and a negative electrode; a bottomed cylindrical outer can for housing the electrode body; and a sealing body for sealing the opening of the outer can. The sealing body is supported on the upper surface of an annular groove provided on the side of the outer can and is riveted to the opening of the outer can, thereby fixing it to the upper part of the outer can.

[0003] Patent Document 1 discloses a non-aqueous electrolyte secondary battery in which an insulating coating layer is provided on the entire side of the outer can, including the interior of an annular groove. Furthermore, Patent Document 1 describes how the coating layer can suppress short circuits caused by dust from the metal material constituting the outer can during the manufacturing process.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2005-071710 Summary of the Invention

[0007] However, in non-aqueous electrolyte secondary batteries, for example, in cases where an external short circuit occurs while the battery is charging, a large current may be applied to the electrodes, causing them to overheat abnormally. This leads to gas buildup inside the battery, increasing internal pressure and potentially damaging the outer casing. If the outer casing is damaged, gas will eject from the damaged area, making this undesirable from a battery safety perspective.

[0008] Furthermore, the inventors' research indicates that damage to the outer casing when the battery malfunctions sometimes occurs within the annular groove provided in the outer casing. Therefore, suppressing damage to the annular groove when the battery malfunctions is an important issue.

[0009] A non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure is characterized by comprising: an electrode body having a positive electrode and a negative electrode, a non-aqueous electrolyte, a bottomed cylindrical outer can containing the electrode body and the non-aqueous electrolyte and containing a first metal material, and a sealing body sealing the opening of the outer can; an annular groove recessed radially inward toward the outer can is provided on the side of the outer can; and a protective member containing a second metal material is provided inside the annular groove, which abuts against at least a portion of the surface of the annular groove; the melting point of the second metal material is lower than that of the first metal material and is below 500°C.

[0010] According to the non-aqueous electrolyte secondary battery as one embodiment of this disclosure, damage to the annular groove can be suppressed when the battery malfunctions. As a result, a highly safe non-aqueous electrolyte secondary battery can be provided. Attached Figure Description

[0011] Figure 1 This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery as an example of an implementation method.

[0012] Figure 2 It is Figure 1 An enlarged view of the annular groove located near the outer packaging tank.

[0013] Figure 3 This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery, which is another example of the embodiment. It is an enlarged view of the vicinity of the annular groove provided in the outer packaging tank.

[0014] Figure 4 This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery, which is another example of the embodiment. It is an enlarged view of the vicinity of the annular groove provided in the outer packaging tank. Detailed Implementation

[0015] Hereinafter, an example of an embodiment of the non-aqueous electrolyte secondary battery according to the present disclosure will be described in detail 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, alternative combinations of the constituent elements of the embodiments described below are included in the present disclosure.

[0016] Figure 1 This is an axial cross-sectional view of a non-aqueous electrolyte secondary battery 10, as an example of an embodiment. (See attached image.) Figure 1 As shown, the non-aqueous electrolyte secondary battery 10 includes an electrode body 14, a non-aqueous electrolyte (not shown), and an outer container 20 for housing the electrode body 14 and the non-aqueous electrolyte. The outer container 20 is a bottomed cylindrical metal container with an opening on one axial side, and the opening 24 of the outer container 20 is sealed by a sealing body 30. Hereinafter, the sealing body 30 side of the non-aqueous electrolyte secondary battery 10 in the axial (height direction) direction will be designated as "upper," and the bottom 21 side of the outer container 20 in the axial direction will be designated as "lower."

[0017] The electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and has a structure in which the positive electrode 11 and negative electrode 12 are wound into a spiral shape, sandwiching the separator 13. The positive electrode 11, negative electrode 12, and separator 13 are all strip-shaped elongated bodies, which are alternately stacked radially on the electrode body 14 by being wound into a spiral shape. To prevent lithium deposition, the negative electrode 12 is formed to be one size larger than the positive electrode 11. That is, the negative electrode 12 is formed to be longer than the positive electrode 11 in both the length and width directions (short side direction). The separator 13 is formed to be at least one size larger than the positive electrode 11, and two separators are arranged to sandwich the positive electrode 11. The non-aqueous electrolyte secondary battery 10 includes insulating plates 16 and 17 respectively disposed above and below the electrode body 14.

[0018] The positive electrode 11 has a positive electrode core and a positive electrode additive layer formed on the positive electrode core. For the positive electrode core, a metal foil stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a thin film formed by depositing this metal on the surface can be used. The positive electrode additive layer contains a positive electrode active material, a conductive agent, and a binder, and is preferably formed on both sides of the positive electrode core, except for the exposed portion (not shown) where the positive electrode lead 18 is soldered. The positive electrode 11 can be manufactured, for example, by coating the positive electrode core with a positive electrode additive slurry containing a positive electrode active material, a conductive agent, and a binder, allowing the coating to dry, and then compressing it to form a positive electrode additive layer on both sides of the positive electrode core.

[0019] The positive electrode mixture layer contains 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 elements constituting the lithium metal composite oxide are, 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. Preferably, it contains at least one selected from Co, Ni, and Mn. Examples of preferred composite oxides include lithium metal composite oxides containing Ni, Co, and Mn, and lithium metal composite oxides containing Ni, Co, and Al.

[0020] Examples of conductive agents included in the positive electrode binder layer include carbon black such as acetylene black and Ketjen black, graphite, carbon nanotubes (CNTs), carbon nanofibers, and graphene. Examples of binders included in the positive electrode binder layer include fluorinated resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins. Alternatively, these resins can be used in combination with carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0021] The negative electrode 12 has a negative electrode core and a negative electrode binder layer formed on the negative electrode core. The negative electrode core can be a foil of a metal that is stable within the potential range of the negative electrode 12, such as copper or a copper alloy, or a thin film of the same metal disposed on its surface. The negative electrode binder layer contains a negative electrode active material, a binder, and a conductive agent as needed, and is preferably formed on both sides of the negative electrode core except for the exposed portion of the negative electrode core to which the negative electrode lead 19 is soldered (not shown). The negative electrode 12 can be manufactured as follows: a negative electrode binder slurry containing a negative electrode active material and a binder is coated on the surface of the negative electrode core, the coating is dried, and then compressed to form a negative electrode binder layer on both sides of the negative electrode core.

[0022] In the negative electrode composite layer, the negative electrode active material typically includes a carbon material that reversibly absorbs and releases lithium ions. Preferred examples of carbon materials include natural graphite such as flake graphite, block graphite, and amorphous graphite, as well as artificial graphite such as blocky graphite (MAG) and graphitized mesophase carbon microspheres (MCMB). Alternatively, materials containing at least one of elements alloyed with Li, such as Si and Sn, or materials containing these elements can also be used as the negative electrode active material. Among these, composite materials containing Si are preferred.

[0023] As a preferred example of a Si-containing composite material, materials in which Si particles are dispersed in a SiO2 phase or a silicate phase such as lithium silicate, or materials in which Si particles are dispersed in an amorphous carbon phase, are also included. A conductive layer, such as a carbon coating, is formed on the surface of the particles in this composite material.

[0024] Similar to the positive electrode binder layer, the binder in the negative electrode binder layer can also be fluoropolymers, PAN, polyimide, acrylic resins, polyolefins, etc., with styrene-butadiene rubber (SBR) being preferred. Furthermore, the negative electrode binder layer preferably contains CMC or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol (PVA), etc. A combination of SBR and CMC or its salts, PAA or its salts, etc., is preferred. The negative electrode binder layer may contain conductive agents such as CNTs.

[0025] The separator 13 can be a porous sheet with ion permeability and insulation. Specific examples of porous sheets include microporous films, woven fabrics, and nonwoven fabrics. The preferred material for the separator 13 is polyolefin such as polyethylene or polypropylene, or cellulose. The separator 13 can be a single-layer structure or a multi-layer structure. Alternatively, a resin layer with high heat resistance, such as an aromatic polyamide resin, can be formed on the surface of the separator 13. A filler layer containing inorganic filler can be formed at the interface between the separator 13 and at least one of the positive electrode 11 and the negative electrode 12.

[0026] The positive electrode 11 is connected to the positive lead 18, and the final winding side of the negative electrode 12 is connected to the negative lead 19. The positive lead 18 extends to the sealing body 30 through the through hole in the insulating plate 16, and the negative lead 19 extends to the bottom 21 of the outer can 20 through the outside of the insulating plate 17. The positive lead 18 is connected to the lower surface of the internal terminal plate 31 of the sealing body 30 by welding or the like, making the sealing body 30 the positive terminal. The negative lead 19 is connected to the inner surface of the bottom 21 of the metal outer can 20 by welding or the like, making the outer can 20 the negative terminal.

[0027] Non-aqueous electrolytes have lithium-ion conductivity. Non-aqueous electrolytes can be liquid electrolytes (electrolytes) or solid electrolytes.

[0028] Liquid electrolytes (electrolytes) consist of a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of non-aqueous solvents include esters, ethers, nitriles, amides, and mixtures of two or more of these. Examples of non-aqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and mixtures thereof. The non-aqueous solvent may contain halogen substitutes (e.g., fluoroethylene carbonate) formed by replacing at least a portion of the hydrogen atoms in these solvents with halogen atoms such as fluorine. Examples of electrolyte salts include lithium salts such as LiPF6.

[0029] As a solid electrolyte, examples include solid or gel-like polymer electrolytes and inorganic solid electrolytes. As an inorganic solid electrolyte, materials known in all-solid-state lithium-ion secondary batteries (e.g., oxide-based solid electrolytes, sulfide-based solid electrolytes, halogen-based solid electrolytes, etc.) can be used. Polymer electrolytes may contain, for example, lithium salts and a matrix polymer, or non-aqueous solvents, lithium salts, and a matrix polymer. As a matrix polymer, for example, a polymer material that gels by absorbing non-aqueous solvents is used. Examples of polymer materials include fluoropolymers, acrylic resins, and polyether resins.

[0030] The outer can 20 is a bottomed cylindrical container with an opening on one axial side. The outer can 20 has a bottom 21 and a side portion 22 that forms the side of the non-aqueous electrolyte secondary battery 10. The side portion 22 is the part of the outer can 20 other than the bottom 21, and includes the annular groove 23 and the opening 24 described later.

[0031] The outer container 20 contains a metallic material (a first metallic material). Examples of the first metallic material include iron, stainless steel, aluminum, aluminum alloys, and nickel. In this embodiment, the outer container 20 is made of steel, with iron as its main component.

[0032] The annular groove 23 is a portion of the side panel 22 that is recessed radially inward, and is formed in an annular shape along the circumference of the outer can 20. The annular groove 23 supports the sealing body 30 on its upper surface. The annular groove 23 can be formed, for example, by spinning a portion of the side panel 22 radially inward to form an annular shape. The width (axial length) of the annular groove 23 is not particularly limited, and is, for example, 0.1 mm or more and 2.0 mm or less. Furthermore, the depth (radial length) of the annular groove 23 is not particularly limited, and is, for example, 0.5 mm or more and 5.0 mm or less. A protective member 40 is provided inside the annular groove 23, as detailed later.

[0033] The opening 24 is a region in the side portion 22 that is higher than the annular groove 23, forming the opening of the outer can 20. When the sealing body 30 is riveted and fixed to the outer can 20, the opening 24 is bent radially inward. Thus, the opening 24 has: an opening side portion 25, which forms part of the side of the non-aqueous electrolyte secondary battery 10 and covers the outer peripheral surface of the gasket 34; and a riveting portion 26, which forms part of the upper surface of the non-aqueous electrolyte secondary battery 10 and extends radially inward. In this embodiment, the radially inner end of the riveting portion 26 is located radially outer than the radially inner end of the gasket 34. That is, a part of the upper surface of the gasket 34 is not covered by the riveting portion 26.

[0034] The sealing body 30 is a circular plate-shaped component equipped with a safety valve. The sealing body 30 has a structure in which an inner terminal plate 31, an insulating member 32, and an outer terminal plate 33 are stacked sequentially from the electrode body 14 side.

[0035] The internal terminal plate 31 is a metal plate comprising a thick-walled portion 31A that connects to the positive electrode lead 18, and a thin-walled central portion 31B that separates from the thick-walled portion 31A when the internal pressure of the battery exceeds a predetermined threshold. A plurality of vent holes 31C are formed in the thick-walled portion 31A.

[0036] The insulating member 32 insulates the portion except for the connection between the inner terminal plate 31 and the outer terminal plate 33. An opening 32A is formed in the radial center of the insulating member 32, and a vent 32B is formed in the portion that overlaps with the vent 31C of the inner terminal plate 31.

[0037] The outer terminal plate 33 forms part of the upper surface of the non-aqueous electrolyte secondary battery 10, and is disposed opposite to the inner terminal plate 31, sandwiching the insulating member 32. The outer terminal plate 33 has a thin-walled portion 33A that breaks when the internal pressure of the non-aqueous electrolyte secondary battery 10 exceeds a predetermined threshold. The outer terminal plate 33 is connected to the central portion 31B of the inner terminal plate 31 by welding or the like at its radial center. In addition, the radially outer side of the outer terminal plate 33 is sandwiched between the riveted portion 26 and the annular groove 23 formed by bending the opening of the outer can 20 inward by means of a gasket 34.

[0038] When the non-aqueous electrolyte secondary battery 10 malfunctions and its internal pressure rises, the generated high-temperature gas pushes the internal terminal plate 31 upwards, causing it to break. The central portion 31B separates from the thick-walled portion 31A, and the external terminal plate 33 deforms, protruding outwards from the battery. This cuts off the current path at the sealing body 30. Furthermore, if the internal pressure of the non-aqueous electrolyte secondary battery 10 rises further after the current path is cut off, the thin-walled portion 33A of the external terminal plate 33 breaks, forming a gas outlet on the external terminal plate 33.

[0039] It should be noted that the structure of the sealing body 30 is not limited to Figure 1 The structure shown. The sealing body 30 may also have, for example, a convex cover that covers the outer terminal plate 33.

[0040] The gasket 34 is a flexible insulating component that electrically isolates the sealing body 30 (as the positive terminal) from the outer can 20 (as the negative terminal) and ensures the airtightness of the interior of the outer can 20 by being compressed in the vertical direction. The material of the gasket 34 is not particularly limited as long as it is a compressible insulating material; for example, polypropylene (PP), polyphenylene sulfide (PPS), polyethylene (PE), polybutylene terephthalate (PBT), perfluoroalkoxyalkane (PFA), polytetrafluoroethylene (PTFE), and polyamide (PA) can be used.

[0041] Next, further reference Figure 2 and Figure 3 The protective component 40 is described in detail. Figure 2 It is Figure 1 The enlarged view of the vicinity of the annular groove 23 is a schematic representation of the shape of the protective member 40.

[0042] like Figure 2 As shown, a protective member 40 made of metal is provided inside the annular groove 23. In this embodiment, the protective member 40 has a linear shape and extends along the circumference of the outer can 20. Furthermore, the protective member 40 is disposed in approximately the entire area inside the annular groove 23 by being wound multiple times around the annular groove 23, and abuts against the upper surface 23A and the lower surface 23B of the annular groove 23.

[0043] The inventors' research indicates that when the electrode body 14 abnormally heats up, gas is generated inside the battery. As the internal pressure of the battery increases, damage to the outer casing 20 sometimes occurs in the area where the annular groove 23 is formed. The detailed mechanism is not yet certain, but it is believed that when the electrode body 14 abnormally heats up, sparks generated on the outer periphery of the electrode body 14 sometimes come into contact with the annular groove 23, causing an excessive temperature rise near the annular groove 23 and resulting in damage to the outer casing 20 in the area where the annular groove 23 is formed.

[0044] The protective member 40 contains a second metal material, which is different from the first metal material constituting the outer can 20 (steel in this embodiment), and is arranged to abut against the upper surface 23A and lower surface 23B of the annular groove 23. Here, the melting point of the second metal material constituting the protective member 40 is lower than that of the first metal material constituting the outer can 20 and is below 500°C. Because the protective member 40 contains the second metal material, when the temperature near the annular groove 23 rises excessively due to abnormal heating of the electrode body 14, the second metal material preferentially melts. As a result, the heat absorption effect caused by melting can suppress the temperature rise near the annular groove 23, and can suppress damage to the annular groove 23 when the battery malfunctions. It should be noted that the protective member 40 is preferably composed mainly of the second metal material. Here, the main component refers to the component with the highest mass percentage in the material constituting the protective member 40. The protective member 40 more preferably contains 80% or more of the second metal material by mass. In this embodiment, the protective member 40 is composed solely of the second metal material.

[0045] The melting point of the second metal material contained in the protective member 40 is lower than that of the first metal material contained in the outer can 20 and is below 500°C, preferably below 400°C, and more preferably below 300°C. By lowering the melting point of the second metal material contained in the protective member 40, the temperature rise near the annular groove 23 when the battery malfunctions can be further suppressed.

[0046] The second metallic material contained in the protective member 40 preferably includes at least one selected from the group consisting of tin, lead, and zinc. By including at least one selected from the group consisting of tin, lead, and zinc, it is easy to make the melting point of the second metallic material below 500°C. The second metallic material can be an alloy containing at least two selected from the group consisting of tin, lead, and zinc. An example of the second metallic material constituting the protective member 40 is an alloy material such as solder.

[0047] As described above, the protective member 40 has a linear shape. In this embodiment, the protective member 40 has a generally circular cross-sectional shape. The size of the protective member 40 is not particularly limited as long as it can be inserted into the annular groove 23; for example, the diameter of the line is 0.1 mm or more and 2.0 mm or less. It should be noted that the cross-sectional shape of the protective member 40 is not limited to a circular shape, but may also be an elliptical or rectangular shape.

[0048] In this embodiment, the protective member 40 is disposed in approximately the entire area inside the annular groove 23. That is, the ratio of the area of ​​the protective member 40 inside the annular groove 23 to the area of ​​the space of the annular groove 23 is 80% or more. By setting the ratio of the area of ​​the protective member 40 to the area of ​​the space of the annular groove 23 to 80% or more, the volume of the protective member 40 can be ensured, and the heat absorption effect caused by the melting of the protective member 40 when the electrode body 14 is abnormally heated can be improved. As a result, the temperature rise near the annular groove 23 can be further suppressed, and damage to the annular groove 23 when the battery malfunctions can be further suppressed. It should be noted that the area of ​​the space of the annular groove 23 in the axial cross-section of the outer can 20 refers to the area surrounded by the imaginary line α along the outer surface of the side portion 22 of the outer can 20 and the wall of the annular groove 23.

[0049] In the axial cross-sectional view of the outer can 20, the ratio of the area of ​​the protective member 40 to the area of ​​the annular groove 23 is preferably 85% or more, more preferably 90% or more. By increasing the ratio of the area of ​​the protective member 40 to the area of ​​the annular groove 23, the heat absorption effect caused by the melting of the protective member 40 when the electrode body 14 is abnormally heated can be further improved. Alternatively, the ratio of the area of ​​the protective member 40 to the area of ​​the annular groove 23 can also be substantially 100%, that is, the protective member 40 is arranged in such a way that it fills the entire annular groove 23.

[0050] It should be noted that the above embodiments can be appropriately modified without prejudice to the purpose of this disclosure. For example, in the above embodiments, the protective member 40 has a linear shape, but it is not limited to this as long as the shape of the protective member 40 abuts against at least a portion of the surface of the annular groove. The protective member 40 may also be a plate-shaped member having a top-view annular shape or a top-view arc shape. For example, the protective member 40 may also be composed of two plate-shaped members having a top-view semi-circular shape, and fixed to the annular groove 23 by being inserted into the annular groove 23 from the radially outer side of the outer can 20.

[0051] Furthermore, in the above embodiment, the protective member 40 is configured to abut against both the upper surface 23A and the lower surface 23B of the annular groove 23. However, the protective member 40 may also contact only either the upper surface 23A or the lower surface 23B of the annular groove 23. It should be noted that when the battery abnormally heats up, the lower surface 23B of the annular groove 23 tends to experience a temperature rise more easily than the upper surface 23A. Therefore, the protective member 40 preferably abuts against at least the lower surface 23B of the annular groove 23.

[0052] Additionally, for example, such as Figure 3 and Figure 4 As shown, the protective member 40 can also be configured to cover at least a portion of the surface of the annular groove 23. Figure 3 In the example shown, the protective member 40 is arranged to cover substantially the entire surface of the annular groove 23. Figure 4 In the example shown, the protective member 40 is configured to cover the lower surface 23B of the annular groove 23.

[0053] It should be noted that when the protective member 40 is configured to cover at least a portion of the surface of the annular groove 23, the protective member 40 preferably covers an area of ​​25% or more of the surface of the annular groove 23, and more preferably covers an area of ​​50% or more of the surface of the annular groove 23. By covering an area of ​​25% or more of the surface of the annular groove 23 with the protective member 40, it is easier to suppress the temperature rise near the annular groove 23 when the battery abnormally heats up.

[0054] Furthermore, in the above embodiment, the protective member 40 disposed in the annular groove 23 is made only of a second metal material with a melting point of 500°C or less, but the protective member 40 may also contain materials other than the second metal material. Examples of materials other than the second metal material include metal materials with a melting point exceeding 500°C and resin materials.

[0055] Example

[0056] The present disclosure is further illustrated below by way of examples, but the present disclosure is not limited to these examples.

[0057] <Example>

[0058] [The production of the positive electrode]

[0059] Using aluminum-containing lithium nickel cobalt oxide (LiNi 0.88 Co 0.09 Al 0.03 O2) was used as the positive electrode active material. 100 parts by weight of the positive electrode active material, 1.0 part by weight of acetylene black as a conductive agent, and 0.9 parts by weight of polyvinylidene fluoride (PVDF) as a binder were mixed in a dispersion medium of N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. Next, the positive electrode slurry was coated onto both sides of a positive electrode current collector formed from aluminum foil. After drying, a specified electrode size was cut, and the electrode was rolled using rollers to obtain a strip-shaped positive electrode. Additionally, an exposed portion of the positive electrode current collector without the positive electrode slurry layer was formed along a portion of the positive electrode's length. The aluminum positive electrode lead was fixed to this exposed portion of the positive electrode current collector using ultrasonic welding.

[0060] [Making the negative electrode]

[0061] As the negative electrode active material, a mixture of 90 parts by mass of graphite powder and 10 parts by mass of Si oxide is used. A negative electrode slurry is prepared by mixing 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. Next, this negative electrode slurry is coated onto both sides of a negative electrode current collector formed from copper foil. After drying, a predetermined electrode size is cut, and the electrode is rolled using a roller to obtain a strip-shaped negative electrode. Furthermore, an exposed portion of the negative electrode current collector without the negative electrode slurry layer is formed at one end along the length of the negative electrode. A nickel negative electrode lead is fixed to this exposed portion of the negative electrode current collector by ultrasonic welding.

[0062] [Electrode fabrication]

[0063] The positive and negative electrodes, sandwiched together with a separator, are wound into a spiral shape to create a wound electrode body. It should be noted that the separator is a heat-resistant layer formed on one side of a microporous membrane made of polyethylene, in which polyamide and alumina fillers are dispersed.

[0064] [Preparation of non-aqueous electrolytes]

[0065] A non-aqueous electrolyte was prepared by dissolving LiPF6 in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DMC) in a volume ratio of 3:3:4 (25°C) at a concentration of 1.2 mol / L.

[0066] [Construction of a non-aqueous electrolyte secondary battery]

[0067] A metal can, made of bottomed cylindrical steel with a diameter of φ21mm and a height of 70mm, is used as the outer can. With insulating plates positioned above and below the electrode body, the electrode body is housed within the outer can, and the negative electrode lead is soldered to the bottom of the outer can. Then, the outer can is spun to form an annular groove. The width (axial length) of the annular groove is set to 0.4mm, and the depth (radial length) of the annular groove is set to 2.0mm.

[0068] Next, an internal terminal plate is placed with a gasket sandwiched in the annular groove, and a positive lead is ultrasonically welded to the upper surface of the internal terminal plate. After degassing, an external terminal plate is placed on the internal terminal plate, and the external and internal terminal plates are welded together. The sealing body is then fixed to the upper part of the outer can by riveting the upper end of the outer can. Finally, a solder wire (composition: Sn 99%, Ag 0.3%, Cu 0.7%, melting point: approximately 230°C, manufactured by HOZAN, HS-341), approximately circular in cross-section (diameter: 0.3 mm), is wound around the annular groove in such a manner that it covers the entire area of ​​the annular groove. Based on the length of the wound solder wire, the ratio of the area of ​​the protective member in the axial cross-section of the outer can to the area of ​​the annular groove is calculated, and the result is 85%.

[0069] <Comparative Example>

[0070] In the fabrication of the non-aqueous electrolyte secondary battery, no protective components are provided. Otherwise, the non-aqueous electrolyte secondary battery is fabricated in the same manner as in Example 1.

[0071] [Evaluation of the battery heating test]

[0072] Three batteries for each of the embodiments and comparative examples were prepared, and each was heated in an oven at 500°C for 10 minutes before heating was stopped. Then, the presence or absence of openings in the annular groove (whether gas was ejected from the annular groove) was evaluated by visually inspecting the outer casing. As a result, no openings were found in any of the three batteries in the embodiments. On the other hand, openings were found in all three batteries in the comparative examples. It is presumed that this is because the protective member in the annular groove suppressed the temperature rise near the annular groove 23 in the event of a battery malfunction.

[0073] This disclosure is further illustrated by the following embodiments.

[0074] Option 1:

[0075] A non-aqueous electrolyte secondary battery comprises: an electrode body having a positive electrode and a negative electrode; a non-aqueous electrolyte; a bottomed cylindrical outer can containing the electrode body and the non-aqueous electrolyte and containing a first metal material; and a sealing body sealing the opening of the outer can. An annular groove recessed radially inward toward the outer can is provided on the side of the outer can. A protective member containing a second metal material is provided inside the annular groove, which abuts against at least a portion of the surface of the annular groove. The melting point of the second metal material is lower than that of the first metal material and is below 500°C.

[0076] Option 2:

[0077] According to the non-aqueous electrolyte secondary battery of Scheme 1, the second metallic material comprises at least one selected from the group consisting of tin, lead and zinc.

[0078] Option 3: The non-aqueous electrolyte secondary battery according to Option 1 or 2, wherein the second metallic material is an alloy comprising at least two selected from the group consisting of tin, lead and zinc.

[0079] Option 4:

[0080] According to any one of Schemes 1 to 3, in the non-aqueous electrolyte secondary battery, the second metal material is solder.

[0081] Option 5:

[0082] According to any one of Schemes 1 to 4, in the non-aqueous electrolyte secondary battery, the protective member has a linear shape and extends circumferentially along the outer can.

[0083] Option 6:

[0084] According to any one of Schemes 1 to 5, in the non-aqueous electrolyte secondary battery, the protective member covers more than 25% of the surface area of ​​the annular groove.

[0085] Option 7:

[0086] According to any one of Schemes 1 to 6, in the non-aqueous electrolyte secondary battery, in the axial cross-section of the outer can, the ratio of the area of ​​the protective member inside the annular groove to the area of ​​the space of the annular groove is 80% or more.

[0087] Explanation of reference numerals in the attached figures

[0088] 10 Non-aqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16, 17 Insulating plate, 18 Positive electrode lead, 19 Negative electrode lead, 20 Outer can, 21 Bottom, 22 Side part, 23 Annular groove, 23A Upper surface, 23B Lower surface, 24 Opening, 25 Opening side part, 26 Riveting part, 30 Sealing body, 31 Internal terminal plate, 31A Thick wall part, 31B Central part, 31C Vent hole, 32 Insulating component, 32A Opening, 32B Vent hole, 33 External terminal plate, 33A Thin wall part, 34 Gasket, 40 Protective component, α Imaginary line.

Claims

1. A non-aqueous electrolyte secondary battery, comprising: Electrode bodies with positive and negative electrodes Non-aqueous electrolytes A bottomed cylindrical outer container for housing the electrode body and the non-aqueous electrolyte containing a first metallic material, and A sealing body that blocks the opening of the outer can. An annular groove, recessed radially inward toward the outer can, is provided on the side of the outer can. A protective member containing a second metallic material is disposed inside the annular groove, which abuts against at least a portion of the surface of the annular groove. The melting point of the second metal material is lower than that of the first metal material and is below 500°C.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The second metallic material comprises at least one selected from the group consisting of tin, lead, and zinc.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The second metallic material is an alloy comprising at least two of the materials selected from the group consisting of tin, lead, and zinc.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The second metallic material is solder.

5. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The protective member has a linear shape and extends circumferentially along the outer can.

6. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The protective member covers more than 25% of the surface area of ​​the annular groove.

7. The non-aqueous electrolyte secondary battery according to claim 1, wherein, In the axial cross-section of the outer can, the ratio of the area of ​​the protective member inside the annular groove to the area of ​​the space of the annular groove is more than 80%.

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