Secondary battery

Abstract

To provide a secondary battery in which the leak of an electrolyte solution out of an electrode body at charging and discharging can be suppressed.SOLUTION: A secondary battery 10 includes a case 12, an electrode body 30 accommodated in the case 12, in which positive and negative electrode sheets are stacked with a separator 60 therebetween, and an electrolyte solution accommodated in the case 12. The electrode body 30 is formed in a flat shape wound around a winding axis 30L. The separator 60 includes a plurality of extension parts 62 in the same direction as a thickness direction of an electrode main body part 32. The extension part 62 is disposed at a position not overlapping with a terminal welding part of non-coated parts 34, 36 by extending from the electrode main body part 32 to one side and the other side in an axial line direction of the winding axis 30L on both sides in an up-down direction. Tip parts 62A of the extension parts 62 in the extending direction are overlapped and bonded together.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] The following Patent Document 1 discloses a technology related to a secondary battery in which a wound electrode body is housed in a battery case together with an electrolyte. Briefly, in this prior art, the wound electrode body is formed by stacking a positive electrode sheet in which a positive electrode active material layer is formed on a long positive electrode current collector and a negative electrode sheet in which a negative electrode active material layer is formed on a long negative electrode current collector with a separator interposed therebetween, and winding them into a flat shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-33824 A Summary of the Invention [Problem to be solved by the invention]

[0004] In such secondary batteries, when the positive electrode sheet and the negative electrode sheet of the wound electrode body expand and contract as the battery is charged and discharged, the electrolyte is pushed out of the wound electrode body, and there is room for improvement in this regard.

[0005] In consideration of the above, an object of the present invention is to provide a secondary battery capable of preventing an electrolyte from being pushed out of an electrode body during charging and discharging. [Means for solving the problem]

[0006] A secondary battery according to a first aspect of the present invention includes a case, a flat electrode assembly housed in the case, in which positive and negative electrode sheets each having a composite layer coated on a portion of the surface of a sheet-like current collector for each of positive and negative electrodes are stacked with a separator sandwiched therebetween, and the electrode assembly is wound around a winding shaft, an electrolyte housed in the case, and an electrode body constituting a portion of the electrode assembly, which is a portion of the current collector that is not coated with the composite layer, which protrudes along the axial direction of the winding shaft from an electrode main body portion in which the current collector, the composite layer, and the separator are stacked, and which is disposed at a position parallel to the winding shaft with respect to the electrode main body portion. and uncoated portions of positive and negative electrodes, each having a terminal welding portion at a middle portion in a vertical direction perpendicular to the axial direction of the winding shaft and the thickness direction of the electrode main body on one and the other sides in the axial direction, where a collector terminal is welded, wherein the separator has a plurality of extension portions on both sides in the vertical direction, each extending from the electrode main body to one and the other sides in the axial direction of the winding shaft and positioned so as not to overlap with the terminal welding portion, in the same direction as the thickness direction of the electrode main body, and the tip ends of the extension portions are overlapped and joined to each other.

[0007] A second aspect of the secondary battery of the present invention is the secondary battery of the first aspect of the present invention, wherein the extension portion is provided on the outermost peripheral portion of the separator and on at least one of the winding portions of the separator that is located more inner than the outermost peripheral portion.

[0008] A secondary battery according to a third aspect of the present invention is the secondary battery according to the first aspect of the present invention, wherein the extension portion is provided only on the outermost peripheral portion of the separator. Effect of the Invention

[0009] In the secondary battery of the first aspect of the present invention, the separator has a plurality of extensions extending from the electrode body to one side and the other side in the axial direction of the winding shaft on both sides in the up-down direction, in the same direction as the thickness direction of the electrode body, and the leading ends of the extensions in the extension direction are overlapped and joined together. Therefore, when the electrode sheets of the positive and negative electrodes expand and contract with the charging and discharging of the secondary battery, the joining of the extending parts of the separator and their leading ends essentially prevents (or almost does not extrude) the electrolyte from both sides in the up-down direction of the electrode body. In other words, it is possible to suppress the electrolyte from being extruded out of the electrode body during the charging and discharging of the secondary battery.

[0010] In the secondary battery according to the second aspect of the present invention, since the extension portion is provided on the outermost peripheral portion of the separator, it is possible to prevent the electrolyte from being pushed out from the electrode body on the outer peripheral side of the electrode body. Furthermore, since the extension portion is provided on at least one of the winding portions located on the inner side of the outermost peripheral portion of the separator, it is possible to prevent the electrolyte present on the inner side of the at least one winding portion from being pushed out.

[0011] In the secondary battery of the third aspect of the present invention, the extension portion is provided only on the outermost peripheral portion of the separator, so that the electrolyte can be prevented from being pushed out of the electrode body on the outer peripheral side of the electrode body, and during manufacturing, the ends of the extension portions in the extension direction can be joined in a short period of time. [Brief description of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing in a simplified form a secondary battery according to a first embodiment. [Diagram 2] 2 is a schematic diagram for explaining the configuration of an electrode body in the secondary battery of FIG. 1. [Diagram 3] 2 is a diagram showing an electrode assembly in the secondary battery of FIG. 1, viewed from the same direction as in FIG. 1. [Figure 4] FIG. 4 is an image diagram showing the separator in an expanded state before being wound. [Diagram 5] 5 is a diagram showing an electrode body in a secondary battery according to a second embodiment, viewed from the same direction as in FIG. 3. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] [First embodiment] A secondary battery 10 according to a first embodiment will be described with reference to Figures 1 to 4. The secondary battery 10 described below is, for example, a lithium-ion secondary battery cell constituting a battery stack used as an on-board power source for an electric vehicle or the like.

[0014] 1 shows a simplified cross-sectional view of a secondary battery 10. The secondary battery 10 has a case 12, an electrode body 30 housed in the case 12, an electrolyte (not shown) housed in the case 12, an insulating film 16 disposed in the case 12 to cover the electrode body 30, and a lid assembly 18 provided on the upper side of the case 12.

[0015] The case 12 is made of metal (aluminum alloy, for example), and is formed into a rectangular box shape that is open at the top and long in the width direction of the battery (direction of arrow W). The electrode body 30 has an electrode main body portion 32 that forms the middle portion in the width direction, and positive and negative uncoated portions 34, 36 provided on both sides in the width direction. Details of the electrode body 30 will be described later. The insulating film 16 is formed into a bag shape. The electrode body 30 is stored in the insulating film 16.

[0016] The lid assembly 18 has a lid member 20, positive and negative current collecting terminals 22, 24 for inputting and outputting electric power from the electrode body 30, and external terminals 26, 28 for external connection. The lid member 20 is formed in a rectangular plate shape that is long in the battery width direction. The lid member 20 is attached so as to close the opening of the case 12. The external terminals 26, 28 are electrically connected to the corresponding positive and negative current collecting terminals 22, 24.

[0017] FIG. 2 shows a schematic diagram for explaining the configuration of the electrode body 30. In FIG. 2, the dimensional ratio of each component is changed from that in FIG. 1 in order to easily show the configuration. The electrode body 30 shown in FIG. 2 is formed by stacking positive and negative electrode sheets 40, 50, in which composite layers 44, 54 are applied to a part of the surface of sheet-shaped positive and negative electrode collectors 42, 52, sandwiching a separator 60, and is wound around a winding axis 30L to form a flat shape. The electrode body 30 is arranged so that the axial direction of the winding axis 30L is the same as the battery width direction (arrow W direction). In the electrode body 30, the electrode main body 32 is formed by stacking the current collectors 42, 52, the composite layers 44, 54, and the separator 60.

[0018] Two separators 60 are provided. In the drawing, the separator 60 that is to be disposed at the outermost periphery of the electrode body 30 is indicated by the reference numeral 60 followed by "60X" in parentheses. The separator 60 is made of an insulating resin material such as polypropylene. A large number of minute holes are formed in the separator 60. The shape of the separator 60 will be described later.

[0019] The positive electrode current collector 42 constituting a part of the positive electrode sheet 40 is made of, for example, a foil of an aluminum alloy or the like. A composite layer 44 is applied to both sides of the current collector 42 except for a part along one edge in the width direction. The composite layer 44 is configured to contain at least an active material that constitutes the positive electrode. The negative electrode current collector 52 constituting a part of the negative electrode sheet 50 is made of, for example, a foil of a copper alloy. A composite layer 54 is applied to both sides of the current collector 52 except for a part along the other edge in the width direction. The composite layer 54 is configured to contain at least an active material that constitutes the negative electrode.

[0020] The positive electrode uncoated portion 34, which is a part of the positive electrode current collector 42 and is not coated with a composite layer, protrudes from the electrode main body 32 along the axial direction of the winding shaft 30L. The positive electrode uncoated portion 34 is disposed on one side of the electrode main body 32 in the axial direction of the winding shaft 30L, and is provided in a plurality of portions in the same direction as the thickness direction of the electrode main body 32. The protruding tip end portions of the uncoated portion 34 are bundled and stacked to form a foil collecting portion 34X (see FIG. 1). FIG. 3 shows the electrode body 30 as viewed from the same direction as FIG. 1. As shown in FIG. 3, the foil collecting portion 34X is provided with a terminal welding portion 34A (portion surrounded by a two-dot chain line) to which the positive electrode current collecting terminal 22 (see FIG. 1) is welded in the middle portion in the up-down direction (direction of arrow A) perpendicular to the axial direction of the winding shaft 30L and the thickness direction of the electrode main body 32.

[0021] As shown in FIG. 2, the negative electrode uncoated portion 36, which is a part of the negative electrode current collector 52 and is not coated with a composite layer, protrudes from the electrode main body 32 along the axial direction of the winding axis 30L. The negative electrode uncoated portion 36 is disposed on the other side of the axial direction of the winding axis 30L with respect to the electrode main body 32, and is provided in a plurality of portions in the same direction as the thickness direction of the electrode main body 32, and the protruding tip sides of the uncoated portions 36 are bundled and stacked to form a foil collecting portion 36X (see FIG. 1). As shown in FIG. 3, the foil collecting portion 36X is provided with a terminal welding portion 36A (portion surrounded by a two-dot chain line) to which the negative electrode current collecting terminal 24 (see FIG. 1) is welded in the middle part in the up-down direction (see arrow A) perpendicular to the axial direction of the winding axis 30L and the thickness direction of the electrode main body 32.

[0022] The separator 60 also has a plurality of extension parts 62 extending from the electrode main body 32 to one side and the other side in the axial direction of the winding shaft 30L on both sides in the up-down direction (see arrow A) and disposed at positions not overlapping with the terminal welding parts 34A, 36A in the same direction as the thickness direction of the electrode main body 32. The extension parts 62 are provided on the outermost peripheral part 60Z of the separator 60, and as an example, are provided on all circumferential parts of the separator 60 located on the inner periphery side of the outermost peripheral part 60Z.

[0023] The tip ends 62A in the extension direction of each of the multiple extension portions 62 are disposed further outward in the battery width direction than the outer ends in the battery width direction of the uncoated portions 34, 36. The tip ends 62A in the extension direction of the multiple extension portions 62 provided in the same direction as the thickness direction of the electrode main body 32 are overlapped and joined to each other. The tip ends 62A of such extension portions 62 are joined to each other by welding (thermal welding), and the number of welding points is four in total.

[0024] In addition, in Figure 3, among the multiple extension portions 62 of the separator 60, the extension portion 62 that is arranged on the upper side in the vertical direction (see arrow A) is indicated by a "62U" in parentheses after the reference symbol 62 (similar to other figures), and among the multiple extension portions 62 of the separator 60, the extension portion 62 that is arranged on the lower side in the vertical direction (see arrow A) is indicated by a "62D" in parentheses after the reference symbol 62 (similar to other figures).

[0025] Fig. 4 shows an image of the separator 60 in an unfolded state before being wound. A main body 64, which is a portion of the separator 60 shown in Fig. 4 excluding the extension portion 62, constitutes a part of the electrode main body 32 (see Fig. 3). In other words, the widthwise dimension C of the main body 64 is the dimension in the battery widthwise direction (arrow W direction) of the portion of the separator 60 that constitutes the electrode main body 32 shown in Fig. 3. Also, the dimension in the battery widthwise direction (arrow W direction) of the electrode body 30 shown in Fig. 3 becomes longer according to the widthwise dimension D of the separator 60 shown in Fig. 4.

[0026] The extension portion 62 (62U) arranged on the upper side in Fig. 3 is U-shaped with an open lower side when viewed in the axial direction of the winding shaft 30L. That is, in Fig. 3, half of the total length of the extension portion 62 (62U) arranged on the upper side along the winding circumferential direction is visible. The extension portion 62 (62D) arranged on the lower side is U-shaped with an open upper side when viewed in the axial direction of the winding shaft 30L. That is, in Fig. 3, half of the total length of the extension portion 62 (62D) arranged on the lower side along the winding circumferential direction is visible.

[0027] In Fig. 4, the multiple extensions 62 (62U) arranged on the upper side after winding are set to have a length in a direction perpendicular to the extending direction (vertical direction in Fig. 4) that is slightly longer as the extensions 62 (62U) are arranged closer to the outer periphery when the separator 60 is wound (details not shown). Similarly, the multiple extensions 62 (62D) arranged on the lower side after winding are set to have a length in a direction perpendicular to the extending direction (vertical direction in Fig. 4) that is slightly longer as the extensions 62 are arranged closer to the outer periphery when the separator 60 is wound (details not shown). These settings correspond to the fact that the radius of the portion that becomes a curved portion in the wound state (the arc-shaped portion when viewed in the axial direction of the winding axis 30L (see Fig. 3)) becomes larger as the extensions 62 are arranged closer to the outer periphery.

[0028] (Action and effect) Next, the operation and effects of this embodiment will be described.

[0029] In the secondary battery 10 shown in FIG. 1, as shown in FIG. 3, the separator 60 has a plurality of extensions 62 extending from the electrode main body 32 to one side and the other side in the axial direction of the winding shaft 30L on both sides in the vertical direction (see the direction of the arrow A) in the same direction as the thickness direction of the electrode main body 32, and the tip ends 62A in the extension direction of the plurality of extensions 62 are overlapped and joined together. Therefore, when the electrode sheets 40 and 50 (see FIG. 2) of the positive and negative electrodes expand and contract with the charging and discharging of the secondary battery 10 shown in FIG. 1, the extensions 62 of the separator 60 and the joining of the tip ends 62A thereof cause the electrolyte present on both sides in the vertical direction of the electrode body 30 to be basically not pushed out of the electrode body 30 (or is hardly pushed out at all). That is, it is possible to suppress the electrolyte from being pushed out of the electrode body 30 during the charging and discharging of the secondary battery 10. As a result, high-rate deterioration can be suppressed, and the occurrence of electrolyte drying up (insufficient amount of electrolyte held by the electrode body 30) can be suppressed.

[0030] High-rate degradation occurs when high-rate charging and discharging (high-rate charging and discharging) is performed continuously, and is a degradation phenomenon in which the internal resistance of a secondary battery increases due in part to a bias in the concentration distribution of lithium ions inside the electrode body. High-rate degradation occurs because low-salt electrolyte leaks out of the electrode body during high-rate charging, and high-salt electrolyte leaks out of the electrode body during high-rate discharging.

[0031] In addition, in this embodiment, since the extension portion 62 is provided on the outermost portion 60Z of the separator 60, it is possible to prevent the electrolyte from being pushed out from the electrode body 30 on the outer peripheral side of the electrode body 30. Furthermore, since the extension portion 62 is provided on all circumferential portions of the separator 60 that are located on the inner side of the outermost portion 60Z, it is possible to prevent the electrolyte present on the inner side of each circumferential portion of the separator 60 from being pushed out.

[0032] [Second embodiment] Next, a secondary battery according to a second embodiment of the present invention will be described with reference to FIG. 5. FIG. 5 shows an electrode body 70 in a secondary battery according to the second embodiment as viewed from the same direction as FIG. 3. As shown in FIG. 5, the electrode body 70 is different from the secondary battery 10 according to the first embodiment (see FIG. 1) in that, instead of the uncoated parts 34, 36 (see FIG. 3, etc.) of the first embodiment, the electrode body 70 is provided with uncoated parts 72, 74 provided only in the middle part in the up-down direction (see arrow A) on both sides in the width direction of the electrode body 70, and in that, instead of the extension part 62 (see FIG. 3, etc.) of the separator 60 of the first embodiment, the separator 80 is provided with an extension part 82 having a smaller extension amount along the axial direction of the winding shaft 30L than the extension part 62. The other configurations are the same as those of the first embodiment. The same reference numerals are used for the same components as those of the first embodiment, and the description thereof will be omitted as appropriate.

[0033] The uncoated parts 72, 74 are configured similarly to the uncoated parts 34, 36 (see FIG. 3, etc.) of the first embodiment, except that they are provided only in the middle parts in the up-down direction (see arrow A) on both sides in the width direction of the electrode body 70, and include terminal welding parts 34A, 36A (parts surrounded by two-dot chain lines). The uncoated parts 72, 74 of this embodiment are sometimes referred to as horizontal tabs. The separator 80 is configured substantially similarly to the separator 60 (see FIG. 3, etc.) of the first embodiment, except that the extension part 82 has a smaller extension amount along the axial direction of the winding shaft 30L than the extension part 62 of the separator 60 of the first embodiment (both see FIG. 3, etc.). The extension part 82 is disposed at a position avoiding the uncoated parts 72, 74, and does not overlap with the uncoated parts 72, 74 in this embodiment. The tip ends 82A in the extending direction of the plurality of extending portions 82 provided in the same direction as the thickness direction of the electrode body 32 are overlapped and joined by welding (thermal welding).

[0034] The second embodiment described above also provides substantially the same functions and effects as the first embodiment.

[0035] [Modifications of the first and second embodiments] 1 to 5, the extensions 62, 82 are provided on the outermost portions 60Z, 80Z of the separators 60, 80 and are provided on all circumferential portions located on the inner side of the outermost portions 60Z, 80Z of the separators 60, 80, but as a modification of the first and second embodiments, a configuration in which the extensions of the separators are provided only on the outermost portions of the separators can be adopted. In such a modification, it is possible to prevent the electrolyte from being pushed out of the electrode body on the outer peripheral side of the electrode body, and during manufacturing, it is possible to join (by welding, as an example) the tip ends of the extensions in the extension direction in a short time.

[0036] As another variation of the first and second embodiments, the extension portion may be provided on the outermost portion of the separator and on at least one, but not all, of the circumferential portions of the separator that are located more inward than the outermost portion.

[0037] Note that, although the effect of preventing the electrolyte from being pushed out of the electrode body during charging and discharging of the secondary battery is inferior to that of the first and second embodiments and their above-mentioned modifications, another modification may be adopted in which the extension portion is not provided on the outermost portion of the separator, but is provided on at least one of the circumferential portions of the separator that is located more inward than the outermost portion.

[0038] In addition, in the first and second embodiments described above, the tip ends 62A, 82A in the extension direction of the extension portions 62, 82 provided in the same direction as the thickness direction of the electrode main body 32 are overlapped and joined by welding, but they may be joined using an adhesive instead of welding.

[0039] The above-described embodiment and the multiple modified examples can be implemented in appropriate combinations.

[0040] While one example of the present invention has been described above, the present invention is not limited to the above, and it goes without saying that the present invention can be implemented in various modified forms without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0041] 10 Secondary battery 12 cases 22 Current collector terminal 24 Current collector terminal 30 Electrode body 30L winding shaft 32 Electrode body 34 Uncoated area 34A Terminal Welding 36 Uncoated area 36A Terminal Welding 40 Electrode sheet 42 Current collector 44 Mixed material layer 50 Electrode Sheet 52 Current collector 54 Mixed material layer 60 Separator 60Z Outermost part of separator 62 Extension part 62A Tip 70 Electrode body 72 Uncoated area 74 Uncoated area 80 Separator 80Z Outermost part of separator 82 Extension 82A Tip A Vertical direction

Claims

1. Case and a flat electrode body housed in the case, in which positive and negative electrode sheets each having a composite layer applied to a portion of a surface of a sheet-like positive and negative electrode current collector are laminated with a separator sandwiched therebetween, and the electrode body is wound around a winding axis; An electrolyte contained in the case; uncoated portions of positive and negative electrodes constituting a part of the electrode body, which are a part of the current collector and are not coated with the composite layer, protruding along the axial direction of the winding shaft from an electrode main body in which the current collector, the composite layer, and the separator are laminated, and in which terminal welding portions are provided at one and the other sides of the electrode main body in the axial direction of the winding shaft, at intermediate portions in a vertical direction perpendicular to the axial direction of the winding shaft and a thickness direction of the electrode main body, to which a current collecting terminal is welded; A secondary battery having The separator has a plurality of extension portions on both sides in the vertical direction that extend from the electrode main body portion to one side and the other side in the axial direction of the winding shaft and are positioned so as not to overlap with the terminal welding portion, in the same direction as the thickness direction of the electrode main body portion, and the tip ends of the extension portions in the extension direction are overlapped and joined to each other.

2. The secondary battery according to claim 1 , wherein the extension portion is provided on an outermost peripheral portion of the separator and on at least one of the winding portions of the separator that is located radially more inward than the outermost peripheral portion.

3. The secondary battery according to claim 1 , wherein the extension is provided only on an outermost peripheral portion of the separator.

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