Energy storage cell

Abstract

To provide a power storage cell in which shortage of an electrolyte in a negative electrode can be suppressed.SOLUTION: The power storage cell includes an electrode body 100, a cell case, and an electrolyte. The electrode body 100 includes: a plurality of electrodes 110, 120 arranged along one direction; and a separator 130 formed in a winding pattern for insulating a plurality of electrodes from one another. The separator 130 includes: a plurality of inclusions 132b intervening between a pair of electrodes; an upper folded part 132b; and a lower folded part 132a. The electrodes have a plurality of positive electrodes 110 and a plurality of negative electrodes 120. The negative electrodes 120 are arranged on the lower folded part 132c. The void rate of the lower folded part 132c is smaller than the void rate of the upper folded part 132a.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an energy storage cell. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2014-67619 discloses a secondary battery including an electrode assembly including a plurality of electrodes and separators disposed between the electrodes, and a case that accommodates the electrode assembly and an electrolyte. The separator is formed in a zigzag shape. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-67619 Summary of the Invention [Problem to be solved by the invention]

[0004] In the secondary battery described in JP 2014-67619 A, the electrolyte is released from the negative electrode during charging and discharging, and there is a concern that the electrolyte may become insufficient in the negative electrode.

[0005] An object of the present disclosure is to provide an electricity storage cell that can suppress a shortage of electrolyte in a negative electrode. [Means for solving the problem]

[0006] An energy storage cell according to one aspect of the present disclosure includes an electrode assembly, a cell case that houses the electrode assembly, and an electrolyte solution housed in the cell case. The electrode assembly includes a plurality of electrodes arranged side by side in one direction, and a separator that is formed in a zigzag shape and provides insulation between each of the plurality of electrodes. The separator includes a plurality of intervening portions interposed between a pair of electrodes that are adjacent to each other in the one direction, an upper end of one of the plurality of intervening portions, and an upper end of one of the plurality of intervening portions that is adjacent to each other in the one direction. and a lower fold portion connecting a lower end of one of the plurality of intervening portions to a lower end of a portion of the plurality of intervening portions adjacent to the one intervening portion on the other side in the one direction, the plurality of electrodes including a plurality of positive electrodes and a plurality of negative electrodes, the negative electrodes being disposed on the lower fold portion, and the porosity of the lower fold portion being smaller than the porosity of the intervening portion. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to provide an energy storage cell that can suppress a shortage of electrolyte in the negative electrode. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view schematically illustrating a storage cell according to an embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view of the storage cell shown in FIG. [Figure 3] FIG. [Figure 4] FIG. 2 is a plan view of the separator before it is formed into a zigzag shape. [Figure 5] 10A and 10B are perspective views schematically illustrating a process of connecting an electrode tab and a current collecting tab. [Figure 6] 10A and 10B are perspective views schematically illustrating a process of bending an electrode tab and a current collecting tab. [Figure 7] FIG. 10 is a perspective view schematically showing a step of inserting the electrode body into the case body. [Figure 8] FIG. 10 is a perspective view schematically showing a modified example of the electrode body. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present disclosure will be described with reference to the accompanying drawings, in which the same or corresponding elements are designated by the same reference numerals.

[0010] Fig. 1 is a perspective view schematically illustrating a storage cell according to an embodiment of the present disclosure, and Fig. 2 is a cross-sectional view of the storage cell shown in Fig. 1.

[0011] As shown in FIGS. 1 and 2, the energy storage cell 1 includes an electrode assembly 100, a cell case 200, an electrolyte (not shown), a pair of external terminals 300, a pair of connecting members 400, and an insulating member 500.

[0012] Fig. 3 is a cross-sectional view of the electrode assembly. As shown in Fig. 3, the electrode assembly 100 includes a plurality of electrodes 110, 120, a separator 130, and an insulating film 140 (see Fig. 7).

[0013] 3, the plurality of electrodes 110, 120 are arranged side by side in one direction (the left-right direction in FIG. 3). The plurality of electrodes 110, 120 includes a plurality of positive electrodes 110 and a plurality of negative electrodes 120.

[0014] Each positive electrode 110 is formed in a rectangular shape that is long in the width direction (a direction perpendicular to both one direction and the up-down direction). Each positive electrode 110 has a positive electrode current collector foil 112 and positive electrode active material layers 114 provided on both sides of the positive electrode current collector foil 112. As shown in FIGS. 2 and 5, the positive electrode current collector foil 112 has a positive electrode tab 112p on which the positive electrode active material layer 114 is not provided. The positive electrode tab 112p protrudes toward one side in the width direction (a direction perpendicular to the plane of the paper in FIG. 3).

[0015] Each negative electrode 120 is formed in a rectangular shape that is long in the width direction. Each negative electrode 120 has a negative electrode current collector foil 122 and a negative electrode active material layer 124 provided on both sides of the negative electrode current collector foil 122. As shown in Figs. 2 and 5, the negative electrode current collector foil 122 has a negative electrode tab 122n on which the negative electrode active material layer 124 is not provided. The negative electrode tab 122n protrudes toward the other side in the width direction.

[0016] The separator 130 provides insulation between the positive electrode 110 and the negative electrode 120. The separator 130 is made of an insulating material and has minute voids that allow ions to pass through. As shown in Fig. 3, the separator 130 is formed in a zigzag shape.

[0017] As shown in FIG. 4, the separator 130 has a separator body 132 and a side covering portion 134.

[0018] The separator body 132 has a rectangular shape before being folded in a zigzag shape. The separator body 132 is disposed between the electrodes 110, 120 while being folded in a zigzag shape. The separator body 132 has a plurality of intervening portions 132a, a plurality of upper folded portions 132b, a plurality of lower folded portions 132c, and an outermost covering portion 132d.

[0019] Each intervening portion 132a is interposed between a pair of electrodes 110, 120 adjacent to each other in one direction. In other words, each intervening portion 132a has the function of insulating between the positive electrode 110 and the negative electrode 120. Each intervening portion 132a is formed of a rectangular region.

[0020] Each upper folded portion 132b connects the upper end of one of the plurality of intervening portions 132a to the upper end of another of the plurality of intervening portions 132a that is adjacent to the one intervening portion 132a on one side in one direction. In this embodiment, the upper folded portion 132b is disposed above the positive electrode 110.

[0021] Each lower folded portion 132c connects the lower end of one of the plurality of intervening portions 132a to the lower end of another of the plurality of intervening portions 132a that is adjacent to the one intervening portion on the other side in one direction. In this embodiment, the lower folded portion 132c is disposed below the negative electrode 120. In other words, the negative electrode 120 is disposed on the lower folded portion 132c. The porosity of the lower folded portion 132c is smaller than the porosity of the intervening portions 132a. For example, the porosity of the lower folded portion 132c is 10% to 30%, and the porosity of the intervening portions 132a is 40% to 60%. The porosity is measured, for example, by mercury intrusion porosimetry.

[0022] In this embodiment, the bottom folded portion 132c is provided with a gap filler 136 that fills gaps in the separator 130. The gap filler 136 preferably has a property of repelling electrolyte (liquid repellency). Examples of the gap filler 136 include PVdF (polyvinylidene fluoride), CMC (carboxymethyl cellulose), and polyimide. In FIG. 3, a dot pattern is applied to the gap filler 136. The vertical dimension of the gap filler 136 is preferably set to 1 mm or more.

[0023] The gap filling material 136 may be applied in advance by gravure coating (intermittent coating) to portions of the separator body 132 that will become the lower folded portions 132c when the separator body 132 is formed into a zigzag shape, and then dried to provide the gap filling material 136 in the lower folded portions 132c. Alternatively, after the separator body 132 is formed into a zigzag shape, the lower folded portions 132c may be immersed in a container that contains the gap filling material 136, and then dried to provide the gap filling material 136 in the lower folded portions 132c.

[0024] The outermost covering portion 132d collectively covers the upper folded portions 132b and the lower folded portions 132c. More specifically, the outermost covering portion 132d collectively covers all of the electrodes 110, 120, all of the intervening portions 132a, all of the upper folded portions 132b, and all of the lower folded portions 132c while being wound around a central axis parallel to the width direction. An end 132e (see FIGS. 3 and 4) of the outermost covering portion 132d is set in a range that does not overlap with the positive electrode active material layer 114 and the negative electrode active material layer 124 in one direction. In this embodiment, the end 132e of the outermost covering portion 132d is provided below the electrodes 110, 120.

[0025] The side covering portion 134 faces both ends of the electrodes 110, 120 in the width direction. In FIG. 3, the side covering portion 134 is indicated by a two-dot chain line. The side covering portion 134 is connected to the lower folded portion 132c. In this embodiment, as shown in FIG. 4, the side covering portion 134 protrudes from the end of the separator body 132 in the longitudinal direction of the separator body 132 in a direction perpendicular to the longitudinal direction. The side covering portion 134 is connected to all of the lower folded portions 132c arranged in one direction. The side covering portion 134, together with the lower folded portion 132c, forms a storage space S (see FIG. 3) below the negative electrode 120 that stores the electrolyte. The side covering portion 134 may be provided with a gap filler that fills gaps in the separator 130.

[0026] The insulating film 140 covers the peripheral and bottom surfaces of the plurality of electrodes 110, 120 and the separator 130. In Fig. 7, the insulating film 140 has a dotted pattern.

[0027] The cell case 200 houses the electrode assembly 100. The cell case 200 houses an electrolyte (not shown). The cell case 200 is sealed. The cell case 200 has a case body 210 and a lid 220.

[0028] The case body 210 has an opening that opens upward. The case body 210 is made of a metal such as aluminum. As shown in FIG. 2, the case body 210 has a bottom wall 212 and a peripheral wall 214. The bottom wall 212 is formed in a rectangular, flat plate shape. The peripheral wall 214 stands upright from the bottom wall 212. The peripheral wall 214 is formed in a square cylindrical shape. The length of the peripheral wall 214 in the width direction is longer than the length of the peripheral wall 214 in the thickness direction. The length of the peripheral wall 214 in the height direction is longer than the length of the peripheral wall 214 in the thickness direction.

[0029] The lid 220 closes the opening of the case body 210. The lid 220 is connected to the opening by welding or the like. The lid 220 is formed in a flat plate shape. The lid 220 is made of a metal such as aluminum. The lid 220 has a pressure release valve 222 and a sealing member 224.

[0030] Pressure release valve 222 is formed in the center of lid 220. Pressure release valve 222 is formed to rupture when the internal pressure of cell casing 200 reaches or exceeds a predetermined pressure. When pressure release valve 222 ruptures, gas within cell casing 200 is released to the outside of cell casing 200 through pressure release valve 222, thereby reducing the internal pressure of cell casing 200.

[0031] The sealing member 224 seals a liquid filling port h formed in the lid 220. The liquid filling port h is a through-hole for injecting an electrolyte into the cell case 200 during the manufacturing process of the energy storage cell 1. The liquid filling port h is sealed by the sealing member 224 after the electrolyte is injected into the case body 210 through the liquid filling port h.

[0032] A pair of external terminals 300 are fixed on the cell case 200. One of the pair of external terminals 300 is a positive electrode external terminal, and the other is a negative electrode external terminal. Each external terminal 300 is fixed to the upper surface of the lid 220 via an upper insulating part 510, which will be described later. Each external terminal 300 is made of a metal such as aluminum. Each external terminal 300 is formed, for example, in the shape of a rectangular parallelepiped. A bus bar (not shown) is connected to each external terminal 300 by welding or the like.

[0033] The pair of connecting members 400 connect the plurality of electrode tabs 112p, 122n to the external terminals 300. One connecting member 400 connects the plurality of positive electrode tabs 112p to the positive electrode external terminals 300, and the other connecting member 400 connects the plurality of negative electrode tabs 122n to the negative electrode external terminals 300. Since the pair of connecting members 400 have substantially the same structure, only one of the connecting members 400 will be described below.

[0034] The connecting member 400 includes a current collecting tab 410 , a sub-tab 420 , and a connecting pin 430 .

[0035] The current collecting tab 410 has a side portion 412 and an upper portion 414. The side portion 412 is located on a side of the electrode assembly 100 in the width direction. The upper portion 414 is located above the electrode assembly 100. The upper portion 414 extends from the upper end of the side portion 412 toward the inside in the width direction.

[0036] The subtabs 420 connect the multiple positive electrode tabs 112p to the current collecting tab 410. One end 422 of the subtab 420 is connected to the multiple positive electrode tabs 112p by welding or the like, and the other end 424 of the subtab 420 is connected to the side portion 412 of the current collecting tab 410 by welding or the like.

[0037] The connecting pin 430 connects the current collecting tab 410 and the external terminal 300. The connecting pin 430 connects the upper part 414 and the external terminal 300. Specifically, the lower end of the connecting pin 430 is inserted into a through hole provided in the upper part 414 and connected to the upper part 414 by welding or the like, and the upper end of the connecting pin 430 is inserted into a through hole provided in the external terminal 300 and connected to the external terminal 300 by welding, crimping or the like.

[0038] The insulating member 500 provides insulation between the cell casing 200 and the connecting member 400. The insulating member 500 has an upper insulating portion 510, a lower insulating portion 520, an insulator 530, and an insulating plate 540.

[0039] The upper insulating part 510 is fixed to the upper surface of the lid 220. The upper insulating part 510 is disposed between the lid 220 and the external terminal 300. The upper insulating part 510 has an insertion hole through which the connecting pin 430 is inserted.

[0040] The lower insulating part 520 is fixed to the lower surface of the lid 220. The lower insulating part 520 is disposed between the lid 220 and the upper part 414 and the lower part of the connecting pin 430. The lower insulating part 520 has an insertion hole through which the connecting pin 430 is inserted.

[0041] The insulator 530 is disposed between the connecting pin 430 and the lid 220. The insulator 530 is formed in a cylindrical shape and surrounds the connecting pin 430.

[0042] The insulating plate 540 is fixed to the lower surface of the upper part 414. The insulating plate 540 is disposed above the electrode assembly 100. Through holes are provided in the insulating plate 540 in a portion located below the pressure release valve 222 and a portion located below the liquid injection port h.

[0043] Next, the manufacturing process of the energy storage cell 1 will be described with reference to FIGS.

[0044] First, the separator body 132 is formed in a zigzag shape, with the electrodes 110, 120 alternately arranged between a pair of intervening portions 132a. Then, after the outermost covering portion 132d of the separator body 132 is wound, the side covering portion 134 is folded relative to the separator body 132 and connected to the lower folded portion 132c.

[0045] Next, as shown in Fig. 5, one end 422 of the sub-tab 420 is connected to the multiple electrode tabs 112p, 122n by welding or the like. Thereafter, as shown by the arrow in Fig. 6, one end 422 of the sub-tab 420 and the multiple electrode tabs 112p, 122n are bent so that one end 422 of the sub-tab 420 contacts the side portion 412 of the current collecting tab 410.

[0046] 7, the peripheral and bottom surfaces of the multiple electrodes 110, 120 and separator 130 are collectively covered with insulating film 140, and then the electrode body 100 is inserted into the case body 210. Then, the peripheral edge of the lid 220 is connected to the opening of the case body 210 by welding or the like.

[0047] Thereafter, the electrolyte is supplied into the cell case 200 through the liquid filling port h, and the liquid filling port h is sealed with the sealing member 224.

[0048] As described above, in the electrode body 100 of this embodiment, the negative electrode 120 is disposed on the lower folded portion 132c, and since the porosity of the lower folded portion 132c is smaller than the porosity of the interposed portion 132a, the electrolyte released from the negative electrode 120 during charging and discharging is effectively retained on the lower folded portion 132c. Therefore, the negative electrode 120 absorbs the electrolyte again, thereby preventing a shortage of electrolyte in the negative electrode 120.

[0049] Furthermore, the separator 130 has the side covering portion 134 that, together with the lower folded portion 132c, forms the storage space S, which more reliably prevents a shortage of electrolyte in the negative electrode 120. Furthermore, the side covering portion 134 prevents the lower folded portions 132c from shifting relative to each other, which in turn prevents the intervening portions 132a from shifting relative to each other, making it possible to omit a dedicated member (such as tape) for fixing the separator 130.

[0050] As shown in FIG. 8, the electrode assembly 100 may further include a liquid retention member 150 capable of retaining an electrolyte. The liquid retention member 150 is a member different from the separator 130. The liquid retention member 150 is made of, for example, a porous material. The liquid retention member 150 is provided at the ends of the multiple electrodes 110, 120 and the separator 130 in the width direction. The liquid retention member 150 may also be provided at the upper or lower ends of the multiple electrodes 110, 120 and the separator 130.

[0051] It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0052] [Aspect 1] An electrode body; a cell case that accommodates the electrode assembly; an electrolyte solution contained in the cell case; The electrode body is A plurality of electrodes arranged in one direction; a separator formed in a zigzag shape and insulating each of the plurality of electrodes, The separator is a plurality of intervening portions interposed between the pair of electrodes adjacent to each other in the one direction; an upper folded portion connecting an upper end portion of one of the plurality of intervening portions to an upper end portion of another of the plurality of intervening portions that is adjacent to the one intervening portion on one side in the one direction; a lower folded portion connecting a lower end portion of one of the plurality of intervening portions to a lower end portion of another of the plurality of intervening portions that is adjacent to the one intervening portion on the other side in the one direction, the plurality of electrodes includes a plurality of positive electrodes and a plurality of negative electrodes; the negative electrode is disposed on the lower folded portion, The porosity of the lower folded portion is smaller than the porosity of the interposed portion.

[0053] In the electrode assembly of this energy storage cell, the negative electrode is disposed on the lower folded portion, and because the porosity of the lower folded portion is smaller than the porosity of the interposed portion, the electrolyte released from the negative electrode during charging and discharging is effectively retained on the lower folded portion. As a result, the electrolyte is absorbed by the negative electrode, thereby preventing a shortage of electrolyte in the negative electrode.

[0054] [Aspect 2] 2. The energy storage cell according to claim 1, wherein the lower folded portion is provided with a gap filler that fills gaps in the separator.

[0055] In this embodiment, the electrolyte is more reliably held on the lower folded portion.

[0056] [Aspect 3] the separator further includes a side covering portion connected to the lower folded portion and facing both end portions of the plurality of electrodes in a width direction perpendicular to both the one direction and the up-down direction, 3. The energy storage cell according to aspect 1 or 2, wherein the side surface covering portion, together with the lower folded portion, forms a storage space below the negative electrode for storing an electrolyte.

[0057] In this embodiment, the lower folded portion and the side covering portion form a storage space for storing the electrolyte, which more reliably prevents the electrolyte from running short in the negative electrode. Furthermore, since the misalignment between the lower folded portions is suppressed, the misalignment between the interposed portions is also suppressed, making it possible to omit a dedicated member (such as tape) for fixing the separator.

[0058] [Aspect 4] 4. The energy storage cell according to aspect 3, wherein the side surface covering portion is provided with a gap filling material that fills gaps in the separator.

[0059] [Aspect 5] The battery further includes a liquid holding member that is a member different from the separator and is capable of holding an electrolytic solution, 5. The energy storage cell according to any one of aspects 1 to 4, wherein the liquid retention member is provided on at least one of an end of the separator in a vertical direction and an end of the separator in a width direction perpendicular to both the one direction and the vertical direction.

[0060] In this embodiment, the electrolyte released from the negative electrode is held in the liquid holding member, and the negative electrode absorbs the electrolyte, thereby preventing a shortage of electrolyte at the negative electrode.

[0061] It should be noted that the embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims rather than the description of the above embodiments, and further includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0062] 1 storage cell, 100 electrode body, 110 positive electrode, 112 positive electrode current collector foil, 112p positive electrode tab, 114 positive electrode active material layer, 120 negative electrode, 122 negative electrode current collector foil, 122n negative electrode tab, 130 separator, 132 separator body, 132a interposition portion, 132b upper folded portion, 132c lower folded portion, 132d outermost coating portion, 134 side coating portion, 136 void filling material, 140 insulating film, 150 liquid retention member, 200 cell case, 210 case body, 220 lid, 300 external terminal, 400 connecting member, 410 current collector tab, 420 sub-tab, 430 connecting pin, 500 insulating member, 510 upper insulating portion, 520 lower insulating portion, 530 Insulator, 540 Insulating plate, S Reservoir space.

Claims

1. An electrode body; a cell case that accommodates the electrode assembly; an electrolyte solution contained in the cell case; The electrode body is A plurality of electrodes arranged in one direction; a separator formed in a zigzag shape and insulating each of the plurality of electrodes, The separator is a plurality of intervening portions interposed between the pair of electrodes adjacent to each other in the one direction; an upper folded portion connecting an upper end portion of one of the plurality of intervening portions to an upper end portion of another of the plurality of intervening portions that is adjacent to the one intervening portion on one side in the one direction; a lower folded portion connecting a lower end portion of one of the plurality of intervening portions to a lower end portion of another of the plurality of intervening portions that is adjacent to the one intervening portion on the other side in the one direction; a side covering portion that faces both end portions of the plurality of electrodes in a width direction perpendicular to both the one direction and the up-down direction and is connected to the lower folded portion, the plurality of electrodes includes a plurality of positive electrodes and a plurality of negative electrodes; the lower folded portion is disposed below the negative electrode, the porosity of the lower folded portion is smaller than the porosity of the interposed portion, The side covering portion, together with the lower folded portion, forms a storage space below the negative electrode for storing an electrolyte.

2. The energy storage cell according to claim 1 , wherein the lower folded portion is provided with a gap filler that fills gaps in the separator.

3. The energy storage cell according to claim 1 , wherein the side surface covering portion is provided with a gap filling material that fills gaps in the separator.

4. The battery further includes a liquid holding member that is a member different from the separator and is capable of holding an electrolytic solution, The energy storage cell according to claim 1 , wherein the liquid retention member is provided on at least one of an end of the separator in the vertical direction and an end of the separator in the width direction.

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