Electrode body

Abstract

To provide an electrode body capable of suppressing a shortage of electrolyte at the center of an electrode in the width direction.SOLUTION: An electrode body includes a plurality of electrodes arranged in one direction, and a separator 130 that insulates the electrodes from each other. The separator 130 has a central region R1 located at the center in a width direction perpendicular to both the one direction and the up-down direction, and an outer region R2 located outside the central region in the width direction. The porosity of the central region R1 is greater than the porosity of the outer region R2.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an electrode assembly. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2022-100813 discloses a so-called stacked electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked with separators interposed therebetween. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-100813 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electrode assembly described in JP 2022-100813 A, the electrolyte is released from the electrode during charging and discharging, causing the electrolyte to move to the ends in the width direction. This raises the concern that the electrolyte may be insufficient in the center of the electrode in the width direction. This is particularly noticeable during high-rate charging and discharging.

[0005] An object of the present disclosure is to provide an electrode assembly that can suppress a shortage of electrolyte at the center of the electrode in the width direction. [Means for solving the problem]

[0006] An electrode body according to one aspect of the present disclosure comprises a plurality of electrodes arranged in a line in one direction, and a separator that provides insulation between each of the plurality of electrodes, the separator having a central region located in the center in a width direction perpendicular to both the one direction and the up-down direction, and an outer region located outside the central region in the width direction, and the porosity in the central region is greater than the porosity in the outer region. [Effects of the Invention]

[0007] According to the present disclosure, an electrode assembly can be provided that can suppress a shortage of electrolyte at the center of the electrode in the width direction. [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] FIG. 10 is a plan view showing a modified example of the separator before it is formed into a zigzag shape. 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, a pair of external terminals 300, a pair of connecting members 400, and an insulating member 500.

[0012] 3 is a cross-sectional view of the electrode assembly 100. As shown in FIG. 3, the electrode assembly 100 includes a plurality of electrodes 110, 120 and a separator .

[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] FIG. 4 is a plan view of the separator 130 before it is formed into a zigzag shape. As shown in FIG. 4, the separator 130 has a rectangular shape before it is formed into a zigzag shape. The separator 130 is disposed between the electrodes 110, 120 while being formed into a zigzag shape. The separator 130 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. Note that in FIG. 4, the portions that will become the folded portions 132b, 132c when formed into a zigzag shape are indicated by diagonal lines.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] As shown in FIG. 4, the separator 130 has a central region R1 and an outer region R2.

[0023] The central region R1 is located at the center in the width direction (left-right direction in FIG. 4). The outer regions R2 are located outside the central region R1 in the width direction. The ratio of the length W1 of the central region R1 in the width direction to the length W of the separator 130 in the width direction is set to, for example, about 40% to 70%.

[0024] The porosity of the central region R1 is greater than the porosity of the outer region R2. For example, the porosity of the central region R1 is 50% or more and 70% or less, and the porosity of the outer region R2 is 30% or more and less than 50%. The porosity is measured, for example, by mercury intrusion porosimetry.

[0025] In this embodiment, the outer region R2 is provided with a gap filler 136 that has a property of repelling electrolyte (liquid repellency) and fills gaps in the separator 130. Examples of the gap filler 136 include PVdF (polyvinylidene fluoride), CMC (carboxymethyl cellulose), and polyimide. In FIG. 4, the gap filler 136 has a dotted pattern.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] A pair of connecting members 400 (see FIG. 2) connect the multiple electrode tabs 112p, 122n to the external terminals 300. One connecting member 400 connects the multiple positive electrode tabs 112p to the positive electrode external terminals 300, and the other connecting member 400 connects the multiple 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.

[0033] The connecting member 400 includes a current collecting tab 410 , a sub-tab 420 , and a connecting pin 430 .

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Next, the manufacturing process of the energy storage cell 1 will be described with reference to FIG. 5 and other figures.

[0043] First, a roller (not shown) is used to fold the separator 130, which has the gap filler 136 in the outer region R2, into a zigzag shape, while alternately arranging the electrodes 110, 120 between a pair of interposition portions 132a. The roller is formed in a crown shape. That is, the roller is formed in a shape that increases in diameter from the end portion toward the center in the direction of the roller's rotation axis. In this way, when the separator 130 is zigzag folded, wrinkles are prevented from forming in the center of the separator 130 in the width direction (the direction parallel to the roller's rotation axis).

[0044] Then, after the outermost covering portion 132d of the separator 130 is wound, the end 132e is connected to the outermost covering portion 132d by an appropriate means.

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

[0046] Next, the peripheral and bottom surfaces of the multiple electrodes 110, 120 and separator 130 are collectively covered with an insulating film (not shown), and then the electrode assembly 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 assembly 100 of this embodiment, the porosity of the separator 130 in the central region R1 is greater than the porosity of the outer regions R2, so that the electrolyte is effectively retained in the central region R1. This prevents a shortage of electrolyte in the central portions of the electrodes 110, 120 in the width direction.

[0049] As shown in FIG. 6, the central region R1 of the separator 130 may be provided with a plurality of slits S, each extending in the vertical direction and spaced apart in the width direction. Each slit S is formed, for example, by laser irradiation. The distance between a pair of adjacent slits S in the width direction and the length of each slit S are set so that the porosity in the central region R1 is approximately 50% to 70%. The electrode assembly 100 in this embodiment has a rectangular parallelepiped shape, i.e., a structure in which rectangular central regions R1 are arranged in one direction. Therefore, designing the pitch of each slit S and the like is easier than with an electrode assembly (wound body) formed in a cylindrical shape. The slits S are set to a size that ensures insulation between adjacent electrodes 110, 120. When a plurality of slits S are provided in the central region R1 of the separator 130, a gap filler 136 may be provided in the outer region R2 of the separator 130, as in the above embodiment.

[0050] The electrode assembly 100 may further include a liquid retention member (not shown) capable of retaining an electrolyte. The liquid retention member is made of, for example, a porous material. The liquid retention member is provided at the ends of the multiple electrodes 110, 120 and separator 130 in the width direction (below the electrode tabs 112p, 122n).

[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] A plurality of electrodes arranged in one direction; a separator for insulating each of the plurality of electrodes from each other; The separator is a central region located at the center in a width direction perpendicular to both the one direction and the up-down direction; an outer region located outside the central region in the width direction, The electrode body, wherein the porosity in the central region is greater than the porosity in the outer region.

[0053] In this electrode assembly, the porosity of the separator in the central region is greater than the porosity in the outer regions, so the electrolyte is effectively retained in the central region, thereby preventing a shortage of electrolyte in the central portion of the electrode in the width direction.

[0054] [Aspect 2] The electrode assembly according to aspect 1, wherein the length of the plurality of electrodes and the separator in the width direction is longer than the length of the plurality of electrodes and the separator in the up-down direction.

[0055] In this embodiment, the liquid is effectively retained in the central portion in the width direction.

[0056] [Aspect 3] 3. The electrode assembly according to aspect 1 or 2, wherein the outer region is provided with a gap filler that has electrolyte-repellent properties and fills gaps in the separator.

[0057] In this embodiment, the movement of the electrolyte from the central region to the outer regions in the width direction is suppressed, so that the shortage of the electrolyte at the central portion of the electrode in the width direction is more reliably suppressed.

[0058] [Aspect 4] The electrode assembly according to any one of aspects 1 to 3, wherein the central region is provided with a plurality of slits that extend in the up-down direction and are spaced apart in the width direction.

[0059] In this embodiment, the electrolyte is effectively held in each slit provided in the central region, so that shortage of electrolyte at the central portion of the electrode in the width direction is more reliably prevented.

[0060] [Aspect 5] 5. The electrode assembly according to any one of aspects 1 to 4, wherein the separator is formed in a zigzag shape.

[0061] [Aspect 6] The electrode assembly according to any one of aspects 1 to 5; a cell case that accommodates the electrode assembly; an electrolyte filled in the cell casing.

[0062] 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]

[0063] 1 storage cell, 100 electrode body, 110 positive electrode, 112 positive current collecting foil, 112p positive electrode tab, 114 positive electrode active material layer, 120 negative electrode, 122 negative current collecting foil, 122n negative electrode tab, 130 separator, 132a interposition portion, 132b upper folded portion, 132c lower folded portion, 132d outermost coating portion, 136 gap filling material, 200 cell case, 210 case body, 220 lid, 300 external terminal, 400 connecting member, 410 current collecting tab, 420 sub-tab, 430 connecting pin, 500 insulating member, 510 upper insulating portion, 520 lower insulating portion, 530 insulator, 540 insulating plate, R1 central region, R2 outer region.

Claims

1. A plurality of electrodes arranged in one direction; a separator for insulating each of the plurality of electrodes from each other; The separator is a central region located at the center in a width direction perpendicular to both the one direction and the up-down direction; an outer region located outside the central region in the width direction, the porosity in the central region is greater than the porosity in the outer region; The electrode body has a plurality of slits in the central region, each extending in the vertical direction and arranged at intervals in the width direction.

2. The electrode assembly according to claim 1 , wherein the length of the plurality of electrodes and the separator in the width direction is longer than the length of the plurality of electrodes and the separator in the up-down direction.

3. The electrode assembly according to claim 1 , wherein the outer region is provided with a gap filler that has electrolyte-repellent properties and fills gaps in the separator.

4. A plurality of electrodes arranged in one direction; a separator for insulating each of the plurality of electrodes from each other; The separator is a central region located at the center in a width direction perpendicular to both the one direction and the up-down direction; an outer region located outside the central region in the width direction, the porosity in the central region is greater than the porosity in the outer region; The electrode assembly, wherein the separator is formed in a zigzag shape.

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