Electricity storage unit

Abstract

The present disclosure provides a power storage cell in which the occurrence of cracks in an electrode mixture layer is suppressed. A power storage cell is provided with an electrode body formed by winding a sheet body around a winding axis, the sheet body including an electrode sheet and a separator, the electrode sheet including a collector plate and an electrode mixture layer formed on the collector plate, and a case in which the electrode body is housed. The electrode sheet has a plurality of grooves which extend in the direction of the winding axis and in which the electrode mixture layer is not formed, the grooves are formed in the direction in which the electrode sheet extends, and the interval between the grooves on the inner side of the winding is smaller than the interval between the grooves on the outer side of the winding.

Description

Technical Field

[0001] The present disclosure relates to a power storage unit. Background Art

[0002] Japanese Patent Application Laid-Open No. 2001-6749 discloses a lithium secondary battery having a wound internal electrode body composed of a positive electrode metal foil and a negative electrode metal foil with a separator interposed therebetween. The internal electrode body is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet. Utility Model Content

[0003] The electrode body of the lithium secondary battery configured as described above is formed by winding the individual sheets.

[0004] For example, the winding radius is smaller near the winding center of the electrode assembly. Consequently, the winding radius of the positive electrode mixture layer of the positive electrode sheet is also smaller near the winding center, causing the positive electrode mixture layer to peel and / or crack. Furthermore, similar issues arise in the negative electrode mixture layer of the negative electrode sheet.

[0005] The present disclosure has been made in view of the above-mentioned problems, and an object of the present disclosure is to provide a power storage cell in which cracks and the like are suppressed from occurring in an electrode mixture layer.

[0006] [1] A power storage unit comprising:

[0007] The electrode body is formed by winding the sheet around the winding axis, and

[0008] a casing housing the electrode assembly,

[0009] The sheet body comprises an electrode sheet and a diaphragm,

[0010] The electrode sheet includes a current collector plate and an electrode mixture layer formed on the current collector plate.

[0011] The electrode sheet has a groove portion extending in the winding axis direction and not forming the electrode mixture layer.

[0012] The groove portion is formed in a plurality of ways in the direction in which the electrode sheet extends.

[0013] The intervals between the grooves on the inner side of the roll are smaller than the intervals between the grooves on the outer side of the roll.

[0014] [2] The power storage unit according to [1],

[0015] The electrode body has a starting end portion of the wound body of the electrode body and a terminal end portion of the wound body of the electrode body,

[0016] The intervals between the grooves increase from the starting end portion toward the ending end portion.

[0017] [3] The power storage unit according to [1] or [2],

[0018] The groove width of the groove portion on the inner side of the roll is smaller than the groove width of the groove portion on the outer side of the roll.

[0019] [4] The power storage unit according to any one of [1] to [3],

[0020] The electrode sheet includes a positive electrode sheet and a negative electrode sheet,

[0021] The positive electrode sheet includes a positive electrode collector plate and a positive electrode mixture layer formed on the positive electrode collector plate.

[0022] The positive electrode sheet has a positive electrode groove portion extending in the winding axis direction and not formed with the positive electrode mixture layer.

[0023] The negative electrode plate includes a negative electrode collector plate and a negative electrode mixture layer formed on the negative electrode collector plate.

[0024] The negative electrode sheet has a negative electrode groove portion extending in the winding axis direction and not formed with the negative electrode mixture layer.

[0025] The positive electrode groove portion and the negative electrode groove portion are formed to face each other.

[0026] [5] The power storage unit according to [4],

[0027] The groove width of the negative electrode groove portion is smaller than the groove width of the opposite positive electrode groove portion.

[0028] According to the electricity storage cell of the present disclosure, it is possible to suppress the occurrence of cracks and the like in the electrode mixture layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings, wherein the same reference numerals denote the same elements.

[0030] Figure 1 It is a cross-sectional view showing the power storage cell 1 according to the present embodiment.

[0031] Figure 2 It is a perspective view schematically showing the electrode body 10 .

[0032] Figure 3 It is a plan view showing the positive electrode sheet 22 .

[0033] Figure 4 It is a plan view showing the negative electrode sheet 24 .

[0034] Figure 5 This is a development view showing a state in which the sheet body 20 is developed and the sheets are arranged side by side.

[0035] Figure 6 Yes Figure 5 A cross-sectional view of the positive electrode sheet 22, the negative electrode sheet 24, the separator 21 and the separator 23. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the drawings, identical or corresponding parts are denoted by the same reference numerals, and their description will not be repeated.

[0037] Figure 1 1 is a cross-sectional view showing an electric storage cell 1 according to this embodiment. The electric storage cell 1 includes a cylindrical electrode body 10 formed around a winding axis O, a case 11 , a positive electrode current collecting member 12 , a negative electrode current collecting member 13 , insulating members 14 and 15 , and a positive electrode terminal 16 .

[0038] Furthermore, in Figure 1 In the diagrams, “Z” indicates the direction in which the winding axis O extends. “Z1” indicates one direction in the Z direction. “Z2” indicates the other direction in the Z direction. “R” indicates the radial direction of the electrode body 10 .

[0039] The housing 11 includes a top plate 17, a bottom plate 18, and a peripheral wall 19. The housing 11 is formed of a metal material. The top plate 17 is located at one end of the housing 11, and the bottom plate 18 is located at the other end of the housing 11. The peripheral wall 19 is disposed between the top plate 17 and the bottom plate 18.

[0040] The through-hole 7 is formed in the top plate 17. The insulating member 14 is arranged on the outer surface of the top plate 17, and the through-hole is formed in the insulating member 14.

[0041] Insulating member 15 includes top plate 2 and peripheral wall 3 provided on the outer peripheral edge of top plate 2. Top plate 2 is disposed on the inner surface of top plate 17. Peripheral wall 3 is disposed on the inner peripheral surface of peripheral wall 19. Top plate 17 has a through hole formed therein.

[0042] Positive terminal 16 includes a plate 50 and a shaft 51. Plate 50 is disposed on insulating member 14. Shaft 51 is connected to plate 50 and is formed to extend in the Z2 direction. Shaft 51 passes through through-hole 7 formed in insulating member 14 and a through-hole formed in insulating member 15, and is inserted into housing 11.

[0043] The positive current collecting member 12 is disposed on the Z2 direction side relative to the insulating member 15. The positive current collecting member 12 is formed in a plate shape, and the lower end of the shaft 51 is welded to the upper surface of the positive current collecting member 12. The positive current collecting member 12 is formed of, for example, aluminum.

[0044] The negative electrode current collecting member 13 is disposed on the inner surface of the bottom plate 18. The negative electrode current collecting member 13 is formed in a plate shape and is made of a metal material such as copper.

[0045] The electrode assembly 10 is disposed between the positive electrode current collecting member 12 and the negative electrode current collecting member 13 in the case 11 .

[0046] The electrode body 10 includes a first end 5 located on the Z1 side, with a positive electrode current collecting member 12 disposed at the first end 5. The electrode body 10 includes a second end 6 located on the Z2 side, with a negative electrode current collecting member 13 disposed at the second end 6. The electrode body 10 is hollow and has a hollow portion 43 formed therein. The hollow portion 43 is formed at a position passing through the winding axis O.

[0047] Figure 2 : is a perspective view schematically showing the electrode assembly 10. The electrode assembly 10 includes a sheet 20 formed so as to surround a winding axis O. Note that "D" is the direction in which the sheet 20 extends in the wound electrode assembly 10.

[0048] The sheet body 20 is formed long in the winding direction D of the electrode assembly 10 . The sheet body 20 includes a separator 21 , a positive electrode sheet 22 , a separator 23 , and a negative electrode sheet 24 .

[0049] Figure 3 It is a plan view showing the positive electrode sheet 22 . Figure 3 The positive electrode sheet 22 shown is unwound from the electrode assembly 10. The positive electrode sheet 22 includes long sides 30 and 31 and short sides 32 and 33. The long sides 30 and 31 extend in the direction L1, which is the direction in which the positive electrode sheet 22 extends. The L1 direction corresponds to the winding direction D when the electrode assembly 10 is wound. The long side 30 is located at the first end 5 of the wound electrode assembly 10, and the long side 31 is located at the second end 6 of the wound electrode assembly 10.

[0050] The positive electrode sheet 22 includes a positive electrode current collector plate 25 and a positive electrode mixture layer 26. The positive electrode current collector plate 25 is formed of a metal material such as aluminum or an aluminum alloy.

[0051] The positive electrode mixture layer 26 includes a positive electrode active material, a binder, etc. The positive electrode active material includes, for example, LiCoO 2 , LiNo 2 , LiMn 2 O 4 , etc. The thickness of the positive electrode mixture layer 26 is, for example, not less than 0.1 μm and not more than 1000 μm.

[0052] The positive electrode mixture layer 26 can be formed on both the front and back sides of the positive electrode collector plate 25, or on one side. The positive electrode sheet 22 has a positive electrode groove portion 27 extending in the direction of the winding axis O, on which the positive electrode mixture layer 26 is not formed. A plurality of positive electrode groove portions 27 are formed in the direction in which the positive electrode sheet 22 extends. The positive electrode mixture layer 26 is separated by a plurality of positive electrode groove portions 27. In the case where the positive electrode mixture layer 26 is formed on both the front and back sides of the positive electrode collector plate 25, the positive electrode groove portions 27 can be formed on the positive electrode mixture layer 26 on the front and back sides, or on one side. In the case where the positive electrode groove portions 27 are formed on one side, this side is preferably formed on the side that becomes the outer side of the roll.

[0053] Figure 4 It is a plan view showing the negative electrode sheet 24 . Figure 4 The negative electrode sheet 24 shown is unwound from the state wound around the electrode assembly 10. The negative electrode sheet 24 includes long sides 36 and 37 and short sides 38 and 39. The long sides 36 and 37 extend in the direction L2, which is the direction in which the negative electrode sheet 24 extends. The L2 direction corresponds to the winding direction D when the electrode assembly 10 is wound. The long side 36 is located at the first end 5 of the wound electrode assembly 10, and the long side 37 is located at the second end 6 of the wound electrode assembly 10.

[0054] The negative electrode sheet 24 includes a negative electrode current collector plate 34 and a negative electrode mixture layer 35. The negative electrode current collector plate 34 is made of a metal material such as copper.

[0055] The negative electrode mixture layer 35 includes a negative electrode active material, a binder, etc. The negative electrode active material is, for example, graphite, etc. The thickness of the negative electrode mixture layer 35 is, for example, not less than 0.1 μm and not more than 1000 μm.

[0056] The negative electrode mixture layer 35 can be formed on both the front and back sides of the negative electrode collector plate 34, or on one side. The negative electrode sheet 24 has a negative electrode groove portion 40 extending in the direction of the winding axis O, on which the negative electrode mixture layer 35 is not formed. A plurality of negative electrode groove portions 40 are formed in the direction in which the negative electrode sheet 24 extends. The negative electrode mixture layer 35 is separated by a plurality of negative electrode groove portions 40. In the case where the negative electrode mixture layer 35 is formed on both the front and back sides of the negative electrode collector plate 34, the negative electrode groove portions 40 can be formed on the negative electrode mixture layer 35 on the front and back sides, or on one side. In the case where the negative electrode groove portion 40 is formed on one side, this side is preferably formed on the side that becomes the outer side of the roll.

[0057] exist Figure 1 In the Z direction, the length of the negative electrode mixture layer 35 is formed to be longer than the length of the positive electrode mixture layer 26 .

[0058] Figure 5This is a developed view showing the sheet body 20 unfolded and arranged side by side. The sheet body 20 is formed by stacking the separator 23 on the negative electrode sheet 24, stacking the positive electrode sheet 22 on the separator 23, and stacking the separator 21 on the positive electrode sheet 22. Furthermore, the positions of the negative electrode sheet 24 and the positive electrode sheet 22 may be reversed.

[0059] The diaphragm 21 and the diaphragm 23 are formed long. The diaphragm 21 includes long sides 70 and 71 and short sides 72 and 73. The diaphragm 23 includes long sides 75 and 76 and short sides 77 and 78.

[0060] exist Figure 5 In FIG. 4 , the electrode assembly 10 includes an electrode mixture layer 45 including a positive electrode mixture layer 26 and a negative electrode mixture layer 35 . The electrode assembly 10 has a starting end S of the wound body of the electrode assembly 10 and an ending end E of the wound body of the electrode assembly 10 .

[0061] In this Figure 5 In the example shown, the short sides 33 and 39 are located at the starting end S. The short sides 32 and 38 are located at the ending end E. Furthermore, the short sides 33 and 39 may be staggered in the winding direction D. In this case, in the wound state, the side close to the winding axis O becomes the starting end S. Similarly, when the short sides 32 and 38 are staggered in the winding direction D, the side away from the winding axis O becomes the ending end E. Figure 5 In the example shown, the short sides 73 and 78 of the separators 21 and 23 are also located at the starting end S, and the short sides 72 and 73 are also located at the ending end E. Alternatively, the separators 21 and 23 may be formed longer in the winding direction D than the positive electrode sheet 22 and the negative electrode sheet 24 .

[0062] Figure 6 Yes Figure 5 2 shows a cross-sectional view of the positive electrode sheet 22, negative electrode sheet 24, separator 21, and separator 23. The positive electrode current collector plate 25 includes a main surface 80 and a main surface 81. The positive electrode mixture layer 26 includes a single-sided positive electrode mixture layer 82 formed on the main surface 80 and a single-sided positive electrode mixture layer 83 formed on the main surface 81.

[0063] The negative electrode current collector plate 34 includes a main surface 84 and a main surface 85 . The negative electrode mixture layer 35 includes a single negative electrode mixture layer 86 formed on the main surface 84 and a single negative electrode mixture layer 87 formed on the main surface 85 .

[0064] exist Figure 6 In the example shown, the starting end S of the inner side of the wound body is located on the right, and the ending end E of the outer side of the wound body is located on the left. Figure 6 The spacing between the grooves on the right side of the roll is smaller than Figure 6 The spacing between the grooves on the left side of the roll. Figure 6In this case, the inner side of the roll is designated as D1, and the outer side of the roll is designated as D2. However, this is merely an example and is not limited thereto.

[0065] The electrode body 10 is formed so as to surround the periphery of the winding axis O from the starting end portion S. Therefore, in the wound electrode body 10, the curvature of the inner side of the roll is greater than the curvature of the outer side of the roll, and as a result, the bending stress becomes large.

[0066] Therefore, there is a concern that cracks may occur in the electrode mixture layer 45 on the inner side of the roll. On the other hand, in the power storage unit 1 of the present embodiment, the electrode sheet has a plurality of groove portions where the electrode mixture layer 45 is not formed. The interval between the groove portions on the inner side of the roll is smaller than the interval between the groove portions on the outer side of the roll. Therefore, the occurrence of cracks and the like in the electrode mixture layer 45 is suppressed.

[0067] In Figure 6 In the positive electrode sheet 22 shown, the intervals W1, W2, W3 between the positive electrode groove portions 27 on the inner side of the roll are smaller than the intervals W4, W5, W6 between the positive electrode groove portions 27 on the outer side of the roll. In the negative electrode sheet 24, the intervals X1, X2, X3 between the negative electrode groove portions 40 on the inner side of the roll are smaller than the intervals X4, X5, X6 between the negative electrode groove portions 40 on the outer side of the roll.

[0068] The interval between the groove portions preferably becomes larger as it goes from the starting end portion S toward the terminal end portion E. When groove portions are provided in the electrode mixture layer 45, the amount of the active material contained in the electrode mixture layer 45 decreases, and thus the capacity decreases. Therefore, instead of providing groove portions uniformly in the electrode mixture layer 45, groove portions are provided more in the inner side of the roll where the bending stress is large, thereby suppressing the decrease in capacity.

[0069] In Figure 6 In the positive electrode sheet 22 shown, the intervals between the positive electrode groove portions 27 are preferably such that W1 < W2 < W3 < W4 < W5 < W6. In the negative electrode sheet 24, the intervals between the negative electrode groove portions 40 are preferably such that X1 < X2 < X3 < X4 < X5 < X6.

[0070] Preferably, the groove width of the groove portions on the inner side of the roll is smaller than the groove width of the groove portions on the outer side of the roll. Because on the inner side of the roll where the bending stress is large, even if the groove width of the groove portions is small, it is possible to sufficiently suppress the occurrence of cracks and the like in the electrode mixture layer 45. In addition, because even if groove portions are provided, it is possible to sufficiently ensure the area for forming the electrode mixture layer 45.

[0071] In Figure 6 In the positive electrode sheet 22 shown, it is preferable that the groove widths Y1, Y2, Y3, Y,4 of the positive electrode groove portions 27 on the inner side of the roll are smaller than the groove widths Y5, Y6, Y7 between the positive electrode groove portions 27 on the outer side of the roll. In the negative electrode sheet 24, it is preferable that the groove widths Z1, Z2, Z3, Z4 of the negative electrode groove portions 40 on the inner side of the roll are smaller than the groove widths Z5, Z6, Z7 between the negative electrode groove portions 40 on the outer side of the roll.

[0072] The groove width of the groove portion preferably increases as it goes from the start end portion S toward the terminal end portion E. Because the closer it is to the start end portion S, the greater the bending stress.

[0073] In Figure 6 In the positive electrode sheet 22 shown, the groove width of the positive electrode groove portion 27 is preferably Y1 < Y2 < Y3 < Y4 < Y5 < Y6 < Y7. In the negative electrode sheet 24, the groove width of the negative electrode groove portion 40 is preferably Z1 < Z2 < Z3 < Z4 < Z5 < Z6 < Z7.

[0074] The positive electrode groove portion 27 and the negative electrode groove portion 40 are preferably formed in a manner facing each other. When the negative electrode groove portion 40 is provided in the negative electrode sheet 24, the ratio of the negative electrode groove portion 40 facing the positive electrode sheet 22 increases, and there is a concern about lithium precipitation. Therefore, by forming the positive electrode groove portion 27 and the negative electrode groove portion 40 in a manner facing each other, the ratio of the negative electrode groove portion 40 and the positive electrode sheet 22 facing each other can be suppressed, and thus lithium precipitation can be suppressed.

[0075] In this case, it is preferable that the groove width of the negative electrode groove portion 40 is smaller than the groove width of the positive electrode groove portion 27 facing it. By setting it like this, lithium precipitation can be further suppressed.

[0076] In Figure 6 it is preferable that Y1 > Z1, it is preferable that Y2 > Z2, it is preferable that Y3 > Z3, it is preferable that Y4 > Z4, it is preferable that Y5 > Z5, it is preferable that Y6 > Z6, it is preferable that Y7 > Z7.

[0077] The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The present disclosure is represented by the scope of claims, including meanings equivalent to the scope of claims and all modifications within the scope.

Claims

1. A power storage unit, characterized in that: have: An electrode body formed by winding a sheet around a winding axis, and a casing housing the electrode assembly, The sheet body comprises an electrode sheet and a diaphragm, The electrode sheet includes a current collector plate and an electrode mixture layer formed on the current collector plate. The electrode sheet has a groove portion extending in the winding axis direction and not forming the electrode mixture layer. The groove portion is formed in a plurality of ways in the direction in which the electrode sheet extends. The intervals between the grooves on the inner side of the roll are smaller than the intervals between the grooves on the outer side of the roll.

2. The power storage unit according to claim 1, wherein The electrode body has a starting end portion of the wound body of the electrode body and a terminal end portion of the wound body of the electrode body, The intervals between the grooves increase from the starting end portion toward the ending end portion.

3. The power storage unit according to claim 1, wherein The groove width of the groove portion on the inner side of the roll is smaller than the groove width of the groove portion on the outer side of the roll.

4. The power storage unit according to any one of claims 1 to 3, characterized in that The electrode sheet includes a positive electrode sheet and a negative electrode sheet, The positive electrode sheet includes a positive electrode collector plate and a positive electrode mixture layer formed on the positive electrode collector plate. The positive electrode sheet has a positive electrode groove portion extending in the winding axis direction and not formed with the positive electrode mixture layer. The negative electrode sheet includes a negative electrode collector plate and a negative electrode mixture layer formed on the negative electrode collector plate. The negative electrode sheet has a negative electrode groove portion extending in the winding axis direction and not formed with the negative electrode mixture layer. The positive electrode groove portion and the negative electrode groove portion are formed to face each other.

5. The power storage unit according to claim 4, wherein: The groove width of the negative electrode groove portion is smaller than the groove width of the opposite positive electrode groove portion.

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