Non-aqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery (10) includes: an electrode body (14) in which a positive electrode and a negative electrode are wound with a separator interposed therebetween; and an exterior can (15). A first electrode, which is one of the positive electrode and the negative electrode, has: a core body; and a lamination part in which a mixture layer is laminated on at least one surface of the core body; and has an uncoated part which is provided at an end part positioned closer to one side in the axial direction than the lamination part and in which the mixture layer is not laminated. The uncoated part is joined to a collector plate (52). The collector plate (52) and the exterior can (15) are joined by a joining part (60) on the outer peripheral side of a bottom part (15b) of the exterior can (15).

Description

Non-aqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery.

[0002] Conventionally, as described in Patent Document 1, as a non-aqueous electrolyte secondary battery, an uncoated portion where the paste layer of the core of the negative electrode is not laminated is projected from the axial end portion of the electrode body, and the projected uncoated portion and the current collector plate are joined by welding. In this configuration, the flat plate portion provided at the center of the current collector plate and the center portion of the bottom of the outer can are joined by welding.

[0003] International Publication No. 2023 / 145680

[0004] In the configuration described in Patent Document 1, there is room for improvement in terms of suppressing the deterioration of battery performance over a long period. In particular, in recent years, due to the increase in the capacity of secondary batteries, the diameter of the outer can has a tendency to increase. In this case, as the battery is repeatedly charged and discharged, the internal pressure of the outer can may increase due to the gas generated from the electrode body, and the bottom of the outer can may bulge outward. As a result, the current collector plate may be deformed so that the joint portion between the bottom of the outer can and the current collector plate moves away from the uncoated portion of the electrode body, and there is a possibility that the joint between the current collector plate and the uncoated portion may be disengaged. Since this disengagement of the joint may lead to a deterioration of battery performance, there is room for improvement.

[0005] Therefore, an object of the present disclosure is to provide a non-aqueous electrolyte secondary battery capable of suppressing the disengagement of the joint between the current collector plate and the electrode body due to the bulge of the bottom of the outer can.

[0006] The non-aqueous electrolyte secondary battery according to the present disclosure includes a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator disposed between the positive electrode and the negative electrode, and an electrode body in which the positive electrode and the negative electrode are wound through the separator, and a bottomed cylindrical outer can that houses the electrode body. One of the positive electrode and the negative electrode, which is the first electrode, has a core and a laminated portion in which a paste layer is laminated on at least one surface of the core, and is provided at an end portion located on one side in the axial direction with respect to the laminated portion, and has an uncoated portion where the paste layer is not laminated. The uncoated portion is joined to a current collector plate, and the current collector plate and the outer can are joined on the outer peripheral side of the bottom of the outer can.

[0007] According to this disclosure, an unpainted portion provided at the axial end of the electrode body is joined to the current collector plate, and the current collector plate and the outer casing are joined on the outer circumference of the bottom of the outer casing. Due to repeated charging and discharging of the secondary battery, the bottom of the outer casing bulges significantly outward in the radially inward portion. In this case, the configuration of this disclosure can prevent the joint between the current collector plate and the bottom of the outer casing from separating from the unpainted portion of the electrode body. This also prevents deformation that would cause the current collector plate to separate from the unpainted portion, thus preventing the joint between the current collector plate and the electrode body from coming loose due to the bulging of the bottom of the outer casing.

[0008] This is an axial cross-sectional view of the non-aqueous electrolyte secondary battery of the embodiment. This is a perspective view of the electrode body constituting the non-aqueous electrolyte secondary battery of the embodiment. This is a perspective view of the electrode body and current collector plate shown in Figure 1, viewed from below. This is a view of the electrode body and current collector plate of Figure 1, viewed from below in the axial direction. (a) is an axial cross-sectional view of the bottom side when the bottom of the outer casing shown in Figure 1 is bulging outwards, and (b) is a view of the bottom of the outer casing, viewed from below in the axial direction. This is a schematic diagram showing the joint between the current collector plate and the outer casing in the embodiment. This is a schematic diagram showing the relationship between the joint between the current collector plate and the outer casing and the bottom when the bottom of the outer casing is bulging outwards in the embodiment. This is a diagram corresponding to Figure 6 in the comparative example of the non-aqueous electrolyte secondary battery. This is a diagram corresponding to Figure 7 in the comparative example of the non-aqueous electrolyte secondary battery. This is a schematic diagram showing another example of the arrangement of the joint between the current collector plate and the outer casing in the embodiment. This is a schematic diagram showing another example of the arrangement of the joint between the current collector plate and the outer casing in the embodiment. This is a schematic diagram of a current collector plate viewed from below in the axial direction, showing the arrangement of the joint between the current collector plate and the bottom of the outer casing in a non-aqueous electrolyte secondary battery in another embodiment. This diagram corresponds to Figure 12 in another embodiment of the non-aqueous electrolyte secondary battery.

[0009] Hereinafter, embodiments of the non-aqueous electrolyte secondary battery according to this disclosure will be described in detail with reference to the drawings. It is intended from the outset that new embodiments can be constructed by appropriately combining the characteristic features of the embodiments and modifications described below. In the following embodiments, the same components are denoted by the same reference numerals in the drawings, and redundant explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios such as length, width, and height of each component do not necessarily match between different drawings. In this specification, the axial opening side of the outer casing 15 of the non-aqueous electrolyte secondary battery 10 is referred to as "upper," and the axial bottom side is referred to as "lower." That is, the bottom of the outer casing 15 is described as the lower end. The secondary battery of this disclosure is not necessarily limited to those in which the bottom of the outer casing is located vertically downward when in use. For example, the bottom of the outer casing may be configured to be vertically above the opening of the outer casing when in use. Furthermore, this disclosure is not limited to the embodiments and modifications described below, and various improvements and changes are possible within the scope of the claims of this application and their equivalents.

[0010] Figure 1 is an axial cross-sectional view of the non-aqueous electrolyte secondary battery 10 according to the embodiment. Figure 2 is a perspective view of the electrode body 14 constituting the non-aqueous electrolyte secondary battery 10. Figure 3 is a perspective view of the electrode body 14 and current collector plate 52 shown in Figure 1, viewed from below. Figure 4 is a view of the electrode body 14 and current collector plate 52 viewed from below in the axial direction. Hereafter, the non-aqueous electrolyte secondary battery 10 will be referred to as secondary battery 10.

[0011] As shown in Figure 1, the secondary battery 10 comprises a wound electrode body 14, a non-aqueous electrolyte (not shown), an outer casing 15, and a sealing body 16. The wound electrode body 14 has a positive electrode 11, a negative electrode 12, and a separator 13, and as shown in Figure 2, the positive electrode 11 and the negative electrode 12 are wound in a spiral shape via the separator 13. The outer casing 15 is a bottomed cylindrical, more specifically a bottomed cylindrical, container for the electrode body 14 and the non-aqueous electrolyte. In the following description, the case in which the negative electrode 12 corresponds to the first electrode and the positive electrode 11 corresponds to the second electrode will be explained, but a configuration in which the positive electrode 11 corresponds to the first electrode and the negative electrode 12 corresponds to the first electrode is also possible. In this case, the unpainted portion provided at the axial end of the positive electrode 11 is joined to the current collector plate 52, which will be described later and is located below it.

[0012] The non-aqueous electrolyte has ionic conductivity (e.g., lithium ion conductivity). The non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (non-aqueous electrolyte solution), but may also be a solid electrolyte using a gel-like polymer or the like. The secondary battery 10 is preferably a lithium-ion battery. The electrolyte salt may be, for example, LiBF ４ LiPF ６ Lithium salts such as the above are used. Non-aqueous solvents include, for example, esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), as well as ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain halogen-substituted products in which at least some of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine.

[0013] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated linear carbonates, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP). In terms of suppressing the deterioration of the charge-discharge cycle characteristics of the secondary battery or improving the input characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% by mass or more and 15% by mass or less of FEC.

[0014] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0015] As shown in Figure 2, six positive electrode tabs, which are current-collecting tabs, are joined to the positive electrode 11 and electrically connected. Each positive electrode tab 20 is a conductive member for electrically connecting the positive electrode core that constitutes the positive electrode 11 to the positive electrode terminal, and extends from the upper end of the positive electrode core of the electrode body 14 to one side (upwards) in the axial direction.

[0016] The negative electrode 12 is formed to be slightly larger than the positive electrode 11 in order to suppress lithium deposition, and is longer than the positive electrode 11 in both the longitudinal and widthwise (short-side) directions. The two separators 13 are also formed to be at least slightly larger than the positive electrode 11 and are arranged to sandwich the positive electrode 11. The separators 13 protrude upward above the positive electrode 11 and the negative electrode 12, while the negative electrode 12 protrudes downward above the positive electrode 11 and the separators 13.

[0017] The negative electrode 12 has an uncoated negative electrode portion 41 at its lower axial end, extending from the beginning end to the end end in the longitudinal direction of the elongated negative electrode 12, where the negative electrode mixture layer 42 is not provided on the negative electrode core body 40. Therefore, the lower axial end of the electrode body 14 is composed of the exposed core portion of the negative electrode 12. The negative electrode 12 may also constitute the beginning end of the electrode body 14. However, generally, the separator 13 extends beyond the beginning end of the negative electrode 12, and the beginning end of the separator 13 becomes the beginning end of the electrode body 14. On the other hand, in this example, the negative electrode 12 constitutes the end end of the electrode body 14. Therefore, the negative electrode 12 extends beyond the end end of the separator 13. The exposed surface of the negative electrode core body 40 exposed on the outer circumferential surface of the negative electrode 12 contacts the inner circumferential surface of the outer can 15 and is electrically connected. Furthermore, the separator 13 may extend beyond the winding end of the negative electrode 12, and the winding end of the separator 13 may become the winding end of the electrode body 14.

[0018] The positive electrode 11 has a strip-shaped positive electrode core and positive electrode mixture layers formed on both sides of the positive electrode core. For the positive electrode core, for example, a metal foil such as aluminum, or a film with the metal arranged on its surface, can be used. A preferred positive electrode core is a metal foil mainly composed of aluminum or an aluminum alloy. The thickness of the positive electrode core is, for example, 10 μm or more and 30 μm or less.

[0019] The positive electrode mixture layer preferably contains a positive electrode active material, a conductive agent, and a binder. The positive electrode 11 is manufactured by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) to both sides of the positive electrode core, followed by drying and rolling.

[0020] Examples of positive electrode active materials include lithium-containing transition metal oxides containing transition metal elements such as Co, Mn, and Ni. While lithium-containing transition metal oxides are not particularly limited, they generally have the formula Li １＋ｘ MO ２ It is preferable that the composite oxide is represented by the formula (wherein -0.2 < x ≤ 0.2, and M includes at least one of Ni, Co, Mn, and Al).

[0021] Examples of the conductive agents mentioned above include acetylene black (AB), carbon black (CB) such as Ketjenblack, and carbon materials such as graphite. Examples of the binders mentioned above include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, and polyolefin resins. These resins may also be used in combination with carboxymethylcellulose (CMC) or its salts, polyethylene oxide (PEO), etc. These may be used individually or in combination of two or more types.

[0022] In the deployed state of the positive electrode 11, there are multiple uncoated positive electrode portions at multiple longitudinal positions (for example, six positions) where the surface of the metal constituting the positive electrode core is exposed in part in the width direction. The uncoated positive electrode portions are the parts to which the positive electrode tabs 20 are joined, and are the parts on the surface of the positive electrode core where the positive electrode mixture layer has not been formed. The multiple positive electrode tabs 20 are joined to the multiple uncoated positive electrode portions, for example, by ultrasonic welding. The positive electrode tabs 20 are covered with insulating tape (not shown), thereby preventing short circuits between the positive electrode 11 and the negative electrode 12.

[0023] The constituent material of the positive electrode tab 20 is not particularly limited. Preferably, the positive electrode tab 20 is made of a metal mainly composed of aluminum.

[0024] Next, the configuration of the negative electrode 12 will be explained using Figure 2. The negative electrode 12 has a strip-shaped negative electrode core 40 and a laminated portion 43 (Figure 2) on which a negative electrode mixture layer 42 is formed on at least one side of the negative electrode core 40. For the negative electrode core 40, for example, a metal foil such as copper, or a film with the metal arranged on its surface, can be used. The thickness of the negative electrode core 40 is, for example, 5 μm or more and 30 μm or less.

[0025] The negative electrode mixture layer 42 preferably contains a negative electrode active material and a binder. The negative electrode 12 is manufactured by, for example, applying a negative electrode mixture slurry containing a negative electrode active material, a binder, and water to both sides of the negative electrode core, and then drying and rolling it.

[0026] The negative electrode active material is not particularly limited as long as it can reversibly intercept and release lithium ions. For example, carbon materials such as natural graphite and artificial graphite, metals that alloy with lithium such as Si and Sn, or alloys and composite oxides containing these can be used. The binder contained in the negative electrode active material layer is, for example, the same resin as in the case of the positive electrode 11. When preparing the negative electrode mixture slurry with an aqueous solvent, styrene-butadiene rubber (SBR), CMC or its salts, polyacrylic acid or its salts, polyvinyl alcohol, etc. can be used. These may be used individually or in combination of two or more.

[0027] A porous sheet having ion permeability and insulating properties is used for the separator 13 (Figure 2). Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the separator 13 is preferably an olefin resin such as polyethylene or polypropylene. The thickness of the separator 13 is, for example, 10 μm to 50 μm. The separator 13 is becoming thinner as batteries increase in capacity and power output. The separator 13 has a melting point of, for example, 130°C to 180°C.

[0028] Furthermore, in the unfolded state of the negative electrode 12, the lower end, which is one end in the width direction, has an uncoated negative electrode portion 41 over its entire length, where the negative electrode mixture layer 42 is not formed. As a result, in the wound state of the electrode body 14, the negative electrode 12 is provided at an end located below the laminated portion 43, on one axial side, and has an uncoated negative electrode portion 41 where the negative electrode mixture layer is not laminated. The uncoated negative electrode portion 41 is provided over its entire length, from the beginning end to the end end of the winding. The uncoated negative electrode portion 41 is joined to the current collector plate 52, which is joined to the bottom 15b of the outer casing 15, as described later.

[0029] Then, with the outermost surface of the negative electrode 12, which is the outermost surface of the electrode body 14, the outermost uncoated portion of the negative electrode core 40 (not shown) is positioned, and tape (not shown) is attached to the outermost surface.

[0030] In the example shown in Figure 1, the battery case is composed of an outer casing 15 and a sealing body 16. The sealing body 16 is formed by stacking an upper metal terminal cap sealing plate 27 and a lower metal current collector plate 50 having a through hole 50a, with a metal plate 51 sandwiched between them in the vertical direction. The sealing plate 27 is hat-shaped with its center bulging upwards. The outer casing 15 has an annular groove 35 formed by recessing the upper end of the cylindrical portion radially inward along its entire circumference. The sealing body 16 is fitted inward through the opening at the upper end of the cylindrical portion 15a of the outer casing 15 via a gasket 28, and while locked to the upper surface of the groove 35, the upper end of the cylindrical portion 15a is crimped radially inward. In this way, the sealing body 16 is crimped and fixed to the inside of the opening end of the outer casing 15 via the outer gasket 28.

[0031] An insulating plate 18 is provided on the upper side of the electrode body 14. The six positive electrode tabs 20 extend towards the sealing body 16 through through holes in the insulating plate 18, pass through through holes 50a in the current collector plate 50, and are joined by being sandwiched between the current collector plate 50 and the metal plate 51. In the secondary battery 10, the sealing plate 27, which is electrically connected to the current collector plate 50 and the metal plate 51, becomes the positive electrode terminal.

[0032] Furthermore, as shown in Figures 3 and 4, a current collector plate 52 is positioned below the electrode body 14. The unpainted portion 41 of the negative electrode formed at the lower end of the negative electrode 12 is pressed against the upper surface of the current collector plate 52 while tilted radially inward, and joined by welding. The current collector plate 52 is also joined to the bottom 15b of the outer casing 15. At this time, the current collector plate 52 and the bottom 15b of the outer casing 15 are joined on the outer circumference side of the bottom 15b. This prevents the current collector plate 52 and the electrode body 14 from coming loose due to bulging of the bottom 15b, as will be described later. The negative electrode 12 is also electrically connected to the outer casing 15, which serves as the negative electrode terminal, via the current collector plate 52.

[0033] The current collector plate 52 is made of a metal such as nickel or a nickel alloy. The current collector plate 52 is plate-shaped and has a plurality of arms 53 that extend outward radially from the center. In the illustrated example, the current collector plate 52 is formed in a cross shape with four arms 53, but there can be three or five or more arms 53. The plurality of arms 53 are connected by a flat connecting plate portion 54 provided in the center. Furthermore, each arm 53 has a projection 55 that protrudes toward the electrode body 14 and extends radially, extending from the base end to the tip of the arm 53. For example, the projection 55 has a rectangular cross-sectional shape perpendicular to the longitudinal direction. The projection 55 is pressed against the unpainted negative electrode portion 41 which is tilted radially inward and joined to the unpainted negative electrode portion 41. For example, with the protruding portion 55 pressed against the uncoated portion 41 of the negative electrode, a laser beam is shone from the arm portion 53 on the side opposite the uncoated portion 41 of the negative electrode towards the bottom of the groove forming the protruding portion 55. As a result, the uncoated portion 41 of the negative electrode and the protruding portion 55 are joined by laser welding.

[0034] Furthermore, each arm portion 53 is provided with a tip plate portion 56 at its radially outer end, the tip plate portion 56 having a circumferential width greater than that of the middle portion of the arm portion 53. At least one of the multiple arm portions 53, or the tip plate portion 56 of all of the arm portions 53, is joined to the bottom portion 15b of the outer container 15. Because the tip plate portion 56 is elongated in the circumferential direction, it becomes easier to weld the bottom portion 15b and the arm portion 53 from the outside of the bottom portion 15b. It also makes it easier to increase the welding strength by increasing the number of welding points. In the illustrated example, the tip plate portion 56 is trapezoidal in shape, with the circumferential length of the tip being greater than the circumferential length of the base end, but it is not limited to this, and various shapes can be adopted.

[0035] When joining the tip plate portion 56 and the bottom portion 15b, for example, the tip plate portion 56 and the bottom portion 15b are joined by laser welding by irradiating a laser beam from the outside of the bottom portion 15b while the lower surface of the tip plate portion 56 is in contact with the inner surface of the bottom portion 15b.

[0036] In this example, as described above, the current collector plate 52 and the bottom portion 15b of the outer casing 15 are joined on the outer circumference of the bottom portion 15b. More specifically, as shown in Figure 1, when the bottom portion 15b is divided into a radially inner region IN and a radially outer region OUT with respect to the center O, which is the center of the bottom, the radially outer region OUT and the current collector plate 52 are joined by a joint 60 formed by welding or the like. In Figure 1, the joint 60 is shown by a thick solid line.

[0037] Furthermore, through diligent analysis, the inventors discovered that the bottom portion 15b tends to bulge significantly outward within the circle passing through the outermost edge of the thin-walled portion. As a result, they found that it is preferable for the joint portion 60 between the current collector plate 52 and the bottom portion 15b to be positioned outside this circle.

[0038] Figure 5(a) is an axial cross-sectional view of the bottom 15b side when the bottom 15b of the outer can 15 bulges outward. Figure 5(b) is a view of the bottom 15b of the outer can 15 viewed from below in the axial direction. As shown in Figure 5(b), the bottom 15b is provided with a connecting groove 62 which is formed by including a plurality of linear grooves when viewed from below. The connecting groove 62 is formed by connecting four J-shaped linear grooves 63. As a result, the connecting groove 62 is formed so that a square portion 64 surrounding the center O of the bottom 15b and four arc-shaped portions 65 that curve radially outward in one direction in the circumferential direction from the four corners of the square portion 64 are connected. This connecting groove 62 forms a thin-walled portion 70 on the bottom 15b that is thinner than other parts. The thin-walled portion 70 constitutes an easily breakable section that, when the secondary battery overheats abnormally, causes the bottom portion 15b to rupture due to the increase in internal pressure, thereby releasing the high-temperature gas inside the battery to the outside.

[0039] As shown in Figure 5(b), a circle α, indicated by a dashed line, is defined at the bottom portion 15b, passing through the outermost edge M, which is the radially outermost point from the center O in the thin-walled portion 70, and with the center O as its center. The outermost edge M of the thin-walled portion 70 is near the tip of the arc-shaped portion 65.

[0040] As shown in Figure 5(b), a circular stepped portion 71 is formed on the lower surface of the bottom 15b of the outer can 15, outside the thin-walled portion 70. The portion closer to the center O from the stepped portion 71 is slightly recessed towards the electrode body 14, but the thickness of the bottom 15b does not change due to the stepped portion 71.

[0041] As described above, it is preferable that the joint 60 between the current collector plate 52 and the bottom portion 15b be positioned outside the circle α passing through the outermost edge M of the thin-walled portion 70. This allows the joint 60 to be positioned in a less deformable part of the bottom portion 15b, even when the bottom portion 15b bulges outward due to repeated charging and discharging of the secondary battery. As a result, as will be described later, the detachment of the joint between the current collector plate 52 and the electrode body 14 due to bulging of the bottom portion 15b can be further suppressed.

[0042] FIG. 5(a) shows a cross-section of the bottom 15b side of the outer can 15 when the secondary battery is repeatedly charged and discharged a predetermined number of times or more. As shown in FIG. 5(a), the bottom 15b is greatly deformed inside the circle α starting from the circle α. This was also confirmed from the photograph of the longitudinal section of the secondary battery taken using an X-ray CT device (X-ray computed tomography device) after the secondary battery was repeatedly charged and discharged a predetermined number of times or more by the present inventor.

[0043] In the above, the case where the thin portion 70 is formed by a plurality of linear groove portions has been described. However, the shape of the thin portion is not limited to this. For example, a circular annular groove formed by only one linear groove portion or a C-shaped groove may form the thin portion. The easily breakable portion is also constituted by the annular groove or the C-shaped groove. Further, the thin portion may be formed over the entire predetermined region including the center O. For example, in the bottom 15b, the entire disk portion centered on the center O may be a thin portion having a smaller thickness than the outside of the disk portion. In this case, the outer peripheral circle of the disk portion can also be arranged within the radially outer region OUT. In this case, since the outer peripheral circle of the disk portion passes through the outermost end of the thin portion and is a circle centered on the center O, it is preferable that the joint portion 60 between the current collector plate 52 and the bottom 15b is arranged outside that circle. <​​​​Also, according to the configuration in which the joint portion 60 between the current collector plate 52 and the bottom portion 15b is disposed outside a circle α passing through the outermost end M of the thin portion 70, even when the bottom portion 15b bulges outward due to repeated charge and discharge of the secondary battery, the joint portion 60 can be disposed at a portion of the bottom portion 15b that is less likely to deform. For this reason, it is possible to further suppress the joint portion 60 from separating from the non-coated negative electrode portion 41, and thus it is possible to further suppress the current collector plate 52 from deforming so as to separate from the non-coated negative electrode portion 41. Therefore, it is possible to further suppress the disconnection of the joint between the current collector plate 52 and the electrode body 14 due to the bulge of the bottom portion 15b.

[0046] FIG. 6 is a schematic view showing a joint portion between the current collector plate 52 and the outer can 15 in the embodiment. FIG. 7 is a schematic view showing the relationship between the joint portion 60 between the current collector plate 52 and the outer can 15 and the bottom portion 15b when the bottom portion 15b of the outer can 15 bulges outward in the embodiment.

[0047] In FIG. 6, a case where all of the radially outer ends of the four arm portions 53 and the bottom portion 15b are joined at the joint portion 60 is shown. In FIGS. 6 and 7, the joint portion 60 is shown by a sanded portion. In this case, as shown in FIG. 7, when the secondary battery 10 repeatedly charges and discharges, the inner surface of the bottom portion 15b deforms so as to bulge outward as indicated by the solid line from the two-dot chain line. In this case, this bulge is larger in the radially inner region IN than in the radially outer region OUT. In the embodiment, since the joint portion 60 between the current collector plate 52 and the outer can 15 is disposed in the radially outer region OUT, even when the bottom portion 15b bulges, it is possible to suppress the joint portion 60 from separating from the non-coated negative electrode portion 41. Thereby, it is also possible to suppress the current collector plate 52 from deforming so as to separate from the non-coated negative electrode portion 41, and thus it is possible to suppress the disconnection of the joint between the current collector plate 52 and the electrode body 14.

[0048] Figure 8 is a diagram corresponding to Figure 6 for the comparative example secondary battery 10a. Figure 9 is a diagram corresponding to Figure 7 for the comparative example secondary battery 10a. As shown in Figure 8, in the comparative example, the central part of the current collector plate 52 and the bottom part 15b of the outer casing 15 are joined at the joint 60. In this case, as shown in Figure 9, when the bottom part 15b of the outer casing 15 bulges, the joint 60 also moves outward according to the bulge, and the arm part 53 of the current collector plate 52 tends to separate from the electrode body 14. On the other hand, in the electrode body 14, the outer circumferential surface of the electrode body 14 is strongly pressed against the inner circumferential surface of the cylindrical part of the outer casing 15 due to expansion during charging and discharging, and is fixed in place. In this case, as shown by the dashed frame β, the joint between the arm part 53 and the uncoated negative electrode part 41 of the electrode body 14 is prone to coming loose. According to the above embodiment, such problems can be prevented.

[0049] Figures 10 and 11 are schematic diagrams showing two alternative arrangements of the joint between the current collector plate 52 and the outer casing 15 in an embodiment. In the alternative example shown in Figure 10, the tips of two of the four arms 53 of the current collector plate 52, which are 180 degrees apart in phase, are welded to the bottom 15b of the outer casing 15 at the joint 60.

[0050] In another example shown in Figure 11, the tip of one of the four arms 53 of the current collector plate 52 is welded to the bottom 15b of the outer casing 15 at the joint 60. In this way, some of the arms 53 of multiple arms 53 may be joined to the bottom 15b.

[0051] Figure 12 is a schematic diagram of a current collector plate 52a, viewed from below in the axial direction, showing the arrangement of the joint portion 60 between the current collector plate 52a and the bottom portion 15b of the outer casing 15 (see Figure 1, etc.), which constitute a secondary battery in another embodiment of the present invention. In this example, the current collector plate 52a is an annular plate and is joined to the bottom portion 15b of the outer casing 15 while positioned on the radially outer region of the bottom portion 15b. In this case, the current collector plate 52 and the bottom portion 15b are joined at joint portions 60 at some or more positions in the circumferential direction of the current collector plate 52a. Also, as shown by the dashed frame, the current collector plate 52 and the unpainted negative electrode portion 41 of the electrode body 14 (see Figure 3) are joined at joint portions 66 at some or more positions in the circumferential direction of the current collector plate 52a. In this example, the other configurations and operations are the same as those in Figures 1 to 7.

[0052] Figure 13 is a diagram corresponding to Figure 12, showing another example of a secondary battery in the embodiment. In this example, the current collector plate 52b has both ends of an inner plate portion 81 that extends diametrically connected to the inner periphery of an annular outer plate portion 80. In this case, the outer plate portion 80 and the bottom portion 15b of the outer casing 15 (see Figure 1, etc.) are joined by one or more joint portions 60. In addition, the current collector plate 52b and the unpainted negative electrode portion 41 of the electrode body 14 (see Figure 3) are joined by two joint portions 66a located at positions that overlap the outer plate portion 80 and the inner plate portion 81 of the current collector plate 52b. This makes it easy to position the joint portions 66a over a long radial range of the unpainted negative electrode portion 41. In this example, the other configurations and operations are the same as those in Figures 1 to 7.

[0053] In addition, while Figures 1 to 7 describe a configuration in which the positive electrode 11 of the electrode body 14 and the sealing body 16 are joined by a plurality of positive electrode tabs 20, an uncoated positive electrode portion may be formed in a part of the longitudinal direction corresponding to the winding direction of the positive electrode, at a position extending along the entire length in the width direction corresponding to the axial direction, where the positive electrode mixture layer is not formed. Then, the positive electrode tabs connected to this uncoated positive electrode portion may be joined to the sealing body.

[0054] 10, 10a Non-aqueous electrolyte secondary battery (secondary battery), 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Outer can, 15a Cylindrical part, 15b Bottom part, 16 Sealing body, 18 Insulating plate, 20 Positive electrode tab, 27 Sealing plate, 28 Gasket, 40 Negative electrode core, 41 Negative electrode unpainted part, 43 Laminated part, 50 Current collector plate, 51 Metal plate, 52, 52a, 52b Current collector plate, 53 Arm part, 54 Connecting plate part, 55 Protruding part, 56 Tip plate part, 60 Joint part, 62 Connecting groove part, 63 Groove part, 64 Square part, 65 Arc-shaped part, 66, 66a Joint part, 70 Thin-walled part, 71 Stepped part, 80 Outer plate part, 81 Inner plate part.

Claims

1. A non-aqueous electrolyte secondary battery comprising: an electrode body having a strip-shaped positive electrode, a strip-shaped negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode and the negative electrode are wound around the separator; and a bottomed cylindrical outer casing for housing the electrode body, wherein the first electrode, which is one of the positive electrode and the negative electrode, has a core body and a laminated portion on at least one side of the core body on which a composite layer is laminated, and has an uncoated portion provided at an end located axially to one side of the laminated portion, on which the composite layer is not laminated, the uncoated portion is joined to a current collector plate, and the current collector plate and the outer casing are joined on the outer circumference of the bottom of the outer casing.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein a thin-walled portion with a small thickness is formed at the bottom of the outer casing, and the joint between the current collector plate and the bottom is located in the thin-walled portion, passing through the outermost radially outermost end from the center of the bottom, and outside the circle centered at the center of the bottom.

3. The thin-walled portion is formed by at least one linear groove and constitutes an easily breakable portion, as described in claim 2 of the non-aqueous electrolyte secondary battery.

4. The current collector plate is plate-shaped having a plurality of arms extending radially outward from the center, the radially outer end of at least one of the plurality of arms is joined to the bottom, and protruding portions formed on the plurality of arms and projecting toward the electrode body are joined to the uncoated portion, the non-aqueous electrolyte secondary battery according to claim 1.

5. The non-aqueous electrolyte secondary battery according to claim 4, wherein the radially outer end of the arm is provided with a tip plate portion having a circumferential width greater than that of the middle portion of the arm, and the tip plate portion is joined to the bottom portion.

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