JP2018186020A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery which can suppress deformation of an electrode due to an increase in internal pressure and can be easily reduced in size and weight. A secondary battery (1) has an electrode assembly (11) in which a plurality of electrodes (21, 22, 23) are stacked via a separator (3) and a peripheral portion (20) of the electrode (2). 1 has a seal portion 12 that covers the side peripheral surface 111, and a restraint member 13 that is in contact with the end portion of the electrode assembly 11 in the stacking direction and restrains the electrode assembly 11 in the stacking direction. Further, in the layered space S surrounded by the electrode 2, the electrode 2 adjacent to the electrode 2, and the seal part 12, the interposition part 4 joined to both of the electrodes 2 facing the layered space S is provided. It is provided. [Selection diagram] Figure 1

Description

  The present invention relates to a secondary battery.

  Secondary batteries such as lithium ion secondary batteries and nickel metal hydride storage batteries are used as batteries for vehicles such as forklifts, hybrid cars, and electric cars. This type of secondary battery includes an electrode assembly in which a plurality of electrodes are stacked via a separator, and a restraining member that compresses the electrode assembly in the stacking direction.

  An electrolyte is held between adjacent electrodes in the electrode assembly. If this electrolyte leaks out of the electrode assembly or comes into contact with the outside air, the battery performance may be deteriorated. Therefore, a seal part for suppressing leakage of electrolyte and entry of outside air may be provided at the peripheral part of the electrode (for example, Patent Document 1).

JP 2007-122977 A

  A secondary battery may generate gas during charging and discharging. In the case where the seal portion is provided at the peripheral portion of the electrode, gas is easily accumulated in a layered space surrounded by the adjacent electrode and the seal portion provided at the peripheral portion of the electrode. When the internal pressure of any layered space increases due to gas accumulation, the difference in internal pressure between the layered space and the adjacent layered space increases, and the layered space with a high internal pressure expands. Moreover, since both ends of the electrode assembly are constrained by the restraining member, when one of the layered spaces expands, the adjacent layered space is compressed.

  When the layered space expands or is compressed due to gas accumulation, the electrode that separates the layered space having a high internal pressure from the adjacent layered space is deformed, and the distance between the electrodes may be biased. Such a deviation in the distance between the electrodes is not preferable because it may cause unevenness of the electrode reaction and deteriorate charge / discharge characteristics.

  Conventionally, in order to suppress the deformation of the electrode, constraining members having high rigidity are provided at both ends of the electrode assembly. However, since each electrode included in the electrode assembly is not directly restrained by the restraining member, it is difficult to sufficiently suppress the above-described electrode deformation by the restraining member. Moreover, since the restraining member having high rigidity has a relatively large mass and volume, the mass and volume of the secondary battery are increased.

  The present invention has been made in view of such a background, and an object of the present invention is to provide a secondary battery that can suppress deformation of an electrode due to an increase in internal pressure and can be easily reduced in size and weight.

One aspect of the present invention is an electrode assembly in which a plurality of electrodes are stacked with a separator interposed therebetween,
A seal portion disposed on a peripheral portion of the electrode and covering a side peripheral surface of the electrode assembly;
A constraining member that abuts each end in the stacking direction of the electrode assembly and restrains the electrode assembly in the stacking direction;
The electrode, an electrode adjacent to the electrode, and an interposition part disposed in a layered space surrounded by the seal part,
The interposition part is in a secondary battery which is interposed between the electrodes in a state where the two electrodes facing the layered space are separated from each other and joined to each of the electrodes.

  The secondary battery has an interposition portion arranged in a layered space surrounded by an electrode, an electrode adjacent to the electrode, and a seal portion. The interposition part is interposed between the electrodes in a state where the two electrodes facing the layered space are separated from each other, and is joined to each of these electrodes.

  In the secondary battery, when the internal pressure of any layered space increases due to gas accumulation, the layered space tends to expand as described above. However, since both of the electrodes facing the layered space are joined to the interposition part, the increase in the distance between the electrodes can be regulated by the interposition part. Therefore, the interposition part can suppress expansion of the layered space due to an increase in internal pressure.

  Further, when any one of the layered spaces tries to expand, the adjacent layered space is compressed. However, since an intervening portion is provided between the two electrodes facing the layered space so as to be separated from each other, the distance between the electrodes due to compression of the layered space is reduced. Reduction can also be regulated. Therefore, the interposition part can suppress compression of the layered space accompanying the increase in internal pressure.

  And since the interposition part is arrange | positioned in each layered space, expansion | swelling and compression of the layered space accompanying an internal pressure rise can be suppressed in any layered space. Therefore, the secondary battery can effectively suppress the deformation of the electrodes due to the increase in internal pressure, and thus can suppress the increase in the deviation of the distance between the electrodes.

  In addition, since the secondary battery can suppress the expansion of the layered space due to the increase in internal pressure in any layered space, the rigidity of the restraint member is conventionally improved while ensuring the effect of suppressing the deformation of the electrode due to the increase in internal pressure. Can be lower. As a result, the secondary battery can be easily reduced in size and weight.

  Thus, according to the said secondary battery, the deformation | transformation of the electrode by an internal pressure rise can be suppressed, and size reduction and weight reduction can be performed easily. Moreover, the said secondary battery can suppress the increase in the deviation of the distance between electrodes, and can also suppress the nonuniformity of electrode reaction and the deterioration of charging / discharging characteristics.

3 is a cross-sectional view showing the main parts of a secondary battery in Example 1. FIG. FIG. 2 is an enlarged view of the vicinity of an interposition part in FIG. 1. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. It is explanatory drawing of the operation | work which laminates | stacks an electrode and a separator in the manufacturing method of the secondary battery of Example 1. FIG. In Example 2, it is sectional drawing which shows the principal part of the secondary battery which has the interposed part which penetrated the separator. FIG. 10 is a cross-sectional view (a cross-sectional view corresponding to FIG. 3) showing a main part of a secondary battery having two interposition parts in Example 3. FIG. 10 is a cross-sectional view (a cross-sectional view corresponding to FIG. 3) showing a main part of a secondary battery having five interposition parts in Example 3.

  In the secondary battery, the electrode assembly has a stacked structure in which a plurality of electrodes are stacked with separators interposed therebetween. The electrode may be in any form as long as it can constitute a single cell in which the positive electrode and the negative electrode face each other via a separator in the electrode assembly. For example, as a positive electrode, a foil electrode in which a positive electrode active material layer is disposed on one or both sides of a metal foil as a current collector, or a porous material in which a positive electrode active material is held in a metal porous body as a current collector An electrode or the like can be employed. Moreover, as a negative electrode, the foil electrode etc. by which the negative electrode active material layer is arrange | positioned on the single side | surface or both surfaces of metal foil as a collector can be employ | adopted.

  Since a foil electrode including a metal foil and an active material layer disposed on at least one surface of the metal foil has lower rigidity than the porous electrode described above, conventionally, the electrode of the electrode accompanying an increase in the internal pressure of the layered space is used. Deformation was easy to occur. On the other hand, in the secondary battery, since the expansion and compression of the layered space can be regulated by the interposition part, the deformation of the electrode can be suppressed even when a foil electrode having a low electrode rigidity is used. .

  Moreover, when using a foil electrode as an electrode, the thickness of an electrode can be easily made thin compared with a porous electrode. Therefore, the secondary battery including the foil electrode can easily increase the number of electrodes per volume as compared with the secondary battery including the porous electrode. As a result, the power density and energy density of the secondary battery can be improved.

  Furthermore, a bipolar electrode having a metal foil as a current collector, a positive electrode active material layer disposed on the front side of the metal foil, and a negative electrode active material layer disposed on the back side is employed as the electrode. You can also. In this case, a plurality of single cells can be connected in series with a simple configuration in which bipolar electrodes are stacked. As a result, the electromotive force of the secondary battery can be further increased.

  In addition, when bipolar electrodes are used, the number of single cells can be increased with respect to the total number of electrodes, compared with the case where unipolar electrodes are used. Therefore, when the total number of electrodes is the same, the number of single cells can be increased as compared with the case where unipolar electrodes are used. Further, when the number of single cells is the same, the total number of electrodes can be reduced and the size of the secondary battery in the stacking direction can be further reduced as compared with the case where unipolar electrodes are used.

  A seal portion is disposed on the peripheral edge portion of the electrode. Further, the side peripheral surface of the electrode assembly is covered with a seal portion. By covering the side peripheral surface of the electrode assembly with the seal portion, it is possible to suppress the entry of air or the like from the outside of the electrode assembly into the layered space, or the leakage of the electrolyte or the like from the layered space to the outside. As the seal portion, for example, a material that can be joined by heating such as polyethylene, polypropylene, polyamide, polyphenylene ether, polyphenylene sulfide, or the like can be used.

  A separator is interposed between the positive electrode and the negative electrode in the single cell. As a separator, a well-known separator for secondary batteries, such as a porous resin film and a nonwoven fabric, can be used, for example.

  The interposition part is arrange | positioned in the layered space enclosed by the electrode, the electrode adjacent to the said electrode, and the seal | sticker part arrange | positioned at the peripheral part of the electrode. Various modes can be adopted as the number and positions of the interposition portions and the manner of joining the interposition portions and the electrodes. For example, the number of interposition parts arranged in each layered space may be one, or two or more. Moreover, the number and position of the interposition part can also be changed for every layered space.

  As an aspect of joining the interposition part and the electrode, for example, an aspect in which an adhesive is used as the interposition part and the interposition part and the electrode are bonded can be employed. Further, it is possible to adopt a mode in which the interposition part is press-fitted into each electrode and the interposition part and the electrode are mechanically joined. In addition to these modes, a known bonding mode can be adopted as long as peeling of the intervening portion from the electrode can be suppressed.

  The interposition part may protrude to the electrode side from the surface of the separator in the stacking direction of the electrode assembly. In this case, since the area of an electrode, an interposition part, and a junction part can be made wider, the joint strength of both can be made higher. As a result, peeling of the interposition part from the electrode can be more effectively suppressed, and as a result, deformation of the electrode due to an increase in internal pressure can be suppressed for a longer period.

  Moreover, the interposition part may be solidified in the state containing the separator. Thus, by forming the interposition part and the separator integrally, the effect of the interposition part can be achieved while ensuring electrical insulation between the two electrodes facing the layered space.

  The separator has a through hole penetrating in the stacking direction of the electrode assembly, and the interposition part may be arranged in the through hole. In this case, the interposition part can be easily arranged in the assembly work of the electrode assembly. As a result, the workability in the assembly work of the electrode assembly can be further improved.

  When an electrode having a foil electrode, that is, a metal foil and an active material layer provided on the metal foil is used as the electrode, the interposition part may be bonded to the active material layer. In this case, it is not necessary to expose the metal foil before joining the interposition part to the electrode. Therefore, an electrode can be produced by a simple process.

  Moreover, the interposition part may be joined to the metal foil. For example, when the electrode has an exposed part in which a part of the metal foil is exposed in the layered space, the interposition part can be joined to the exposed part. By directly joining the interposition part and the metal foil, the joining strength can be increased as compared with the case where the interposition part is joined to the active material layer. Therefore, peeling of the interposition part from metal foil can be suppressed more effectively, and the deformation | transformation of the electrode by internal pressure rise can also be suppressed over a long period of time.

  Examples of intervening parts include polyolefins such as polyethylene (PE) and polypropylene (PP); acrylic resins; fluororesins such as polytetrafluoroethylene (PTFE); styrene butadiene rubber (SBR), ethylene propylene diene rubber (EPDM), and the like. It is possible to use an insulator that is excellent in durability against strong alkali and can be bonded to an electrode by heating, such as synthetic rubber.

  A restraining member is in contact with the end of the electrode assembly in the stacking direction. The electrode assembly is restrained in the stacking direction by a restraining member. As a material of the restraining member, for example, a metal such as aluminum, an aluminum alloy, or a stainless alloy can be used.

  In producing the secondary battery, first, an electrode is prepared by a conventional method, and a seal portion is disposed on the peripheral portion of the electrode. Next, interposing portions are arranged in the layered space while alternately laminating electrodes and separators, and the interposed portions are brought into contact with both electrodes facing the layered space to produce a laminate.

  The operation of laminating the electrode and the separator and the operation of arranging the interposition portion in the layered space may be performed in any order as long as the laminated body having the above configuration can be finally obtained. For example, by providing an intervening portion in the separator in advance and alternately laminating the separator and the electrode, the laminate can be produced. In this case, the laminate can be produced by a simple operation of alternately laminating electrodes and separators.

  Moreover, a laminated body can also be produced by providing a through hole penetrating in the thickness direction in the separator in advance and alternately laminating electrodes and the separator while disposing an interposition portion in the through hole.

  Next, by compressing the laminated body in the laminating direction while heating, the forming operation of the seal portion and the joining operation of the interposition portion to each electrode can be performed collectively to produce an electrode assembly. Then, a secondary battery can be obtained by arrange | positioning a restraining member to the both ends in the lamination direction of an electrode assembly.

(Example 1)
Examples of the secondary battery will be described with reference to the drawings. As shown in FIG. 1, the secondary battery 1 includes an electrode assembly 11 in which a plurality of electrodes 2 (21, 22, 23) are stacked via a separator 3, and a peripheral portion 20 of the electrode 2. A seal portion 12 that covers the side peripheral surface 111 of the assembly 11 and a restraining member 13 that abuts the end portion in the stacking direction of the electrode assembly 11 and restrains the electrode assembly 11 in the stacking direction. Further, the interposition part 4 is arranged in the layered space S surrounded by the electrode 2, the electrode 2 adjacent to the electrode 2, and the seal part 12. The interposition part 4 is interposed between the electrodes 2 in a state where the two electrodes 2 facing the layered space S are separated from each other, and is joined to each of these electrodes 2.

  The electrode assembly 11 of this example includes, as the electrode 2, termination electrodes 21 and 23 disposed at both ends in the stacking direction, and a plurality of bipolar electrodes 22 disposed between the termination electrode 21 and the termination electrode 23. doing.

  The bipolar electrode 22 includes a metal foil 24 having a rectangular shape, a positive electrode active material layer 25p provided on the front side surface of the metal foil 24, and a negative electrode active material layer 25n provided on the back side surface. As shown in FIGS. 1 and 3, the peripheral edge portion 20 of the bipolar electrode 22 is covered with the seal portion 12. The positive electrode active material layer 25 p is provided in a region inside the seal portion 12 on the front side surface of the metal foil 24. The negative electrode active material layer 25 n is provided in a region inside the seal part 12 on the back side surface of the metal foil 24. Although not shown in the drawing, the active material layer 25 (25p, 25n) of this example is a porous body including a large number of active material particles.

  Of the two termination electrodes 21 and 23, the first termination electrode 21 disposed at one end in the stacking direction has the same configuration as the bipolar electrode 22 except that it does not have the positive electrode active material layer 25p. Further, the second termination electrode 23 disposed at the other end in the stacking direction has the same configuration as the bipolar electrode 22 except that it does not have the negative electrode active material layer 25n.

  The termination electrodes 21 and 23 and the bipolar electrode 22 are arranged such that the positive electrode active material layers 25p and the negative electrode active material layers 25n are alternately arranged in the stacking direction. Further, the separator 3 is interposed between the positive electrode active material layer 25p and the negative electrode active material layer 25n. Thereby, between the metal foils 24, a single cell in which the positive electrode active material layer 25p as the positive electrode and the negative electrode active material layer 25n as the negative electrode face each other through the separator 3 is configured. In the electrode assembly 11 of this example, a plurality of single cells are electrically connected in series via the metal foil 24.

  As shown in FIG. 1, the side peripheral surface 111 of the electrode assembly 11 is covered with a seal portion 12. Further, the peripheral portion 20 of each electrode 2, that is, the active material layer 25 (25p, 25n) is not provided in the seal portion 12, and the portion where the metal foil 24 is exposed is held.

  The electrode assembly 11 has a plurality of layered spaces S surrounded by the electrode 2, the electrode 2 adjacent to the electrode 2, and the seal portion 12. In the layered space S, the separator 3 and the interposition part 4 are arranged.

  As shown in FIG. 3, the separator 3 has a rectangular shape in plan view as viewed from the stacking direction of the electrode assembly 11. The separator 3 of this example is a nonwoven fabric composed of polyolefin resin fibers.

  The interposition part 4 is arranged at the center of the separator 3 in a plan view as viewed from the stacking direction of the electrode assembly 11. As shown in FIG. 1 and FIG. 2, the interposition part 4 of this example is solidified in a state including the separator 3, and is joined to each of the positive electrode active material layer 25p and the negative electrode active material layer 25n facing the separator 3. Has been. Further, as shown in FIG. 2, the interposition part 4 protrudes closer to the electrode 2 than the surface 31 of the separator 3 in the stacking direction of the electrode assembly 11. In addition, the interposition part 4 of this example is comprised from the polypropylene. Further, in FIG. 1, for the sake of convenience, the interposition part 4 is simplified and described so that the interposition part 4 has the same thickness as the separator 3.

  Metal restraining members 13 are disposed at both ends of the electrode assembly 11 in the stacking direction. The restraining member 13 is held by a holding plate (not shown) in contact with the metal foil 24 of the termination electrodes 21 and 23. The secondary battery 1 of the present example can electrically connect the electrode assembly 11 and an external circuit (not shown) via the restraining member 13.

  The secondary battery 1 of this example can be manufactured by the following procedures, for example. First, the active material layer 25 (25p, 25n) is applied to the metal foil 24, and the termination electrodes 21 and 23 and the bipolar electrode 22 are produced. Subsequently, the seal part 12 is arrange | positioned in the peripheral part 20 of these electrodes 21-23.

  Separately from the preparation of the electrodes 21 to 23 described above, the separator 3 is prepared, and the interposition part 4 is arranged in the center thereof. Although not shown in the drawing, in this example, the separator 3 is solidified, and the interposition part 4 having a shape protruding from the surface 31 of the separator 3 toward the electrode 2 is formed. Examples of a method for forming such an interposition part 4 include the following methods. First, after the interposition part 4 is dissolved in a solvent, this solution is dropped on the center of the separator 3, and the solution is permeated in the thickness direction of the separator 3. Thereafter, by drying the separator 3 and removing the solvent, the interposition part 4 solidified in a state including the separator 3 can be formed.

  Further, instead of the method described above, the intervening portion 4 that has been melted in advance may be allowed to penetrate into the center of the separator 3. In this case, after the molten intervening portion 4 has penetrated in the thickness direction, the intervening portion 4 is cooled and solidified to form the solidified intervening portion 4 including the separator 3. it can.

  The electrodes 21 to 23 prepared as described above and the separators 3 are alternately laminated to produce a laminate 110 shown in FIG. Then, by compressing in the stacking direction while heating the stacked body 110 (FIG. 4, arrow 112), the seal portions 12 are welded together, and the positive electrode active material layer 25p and the negative electrode active material layer are melted while the interposition portion 4 is melted. Press fit into each of 25n.

  The melted interposition part 4 enters the pores of the positive electrode active material layer 25p and the negative electrode active material layer 25n, which are porous bodies, by the compression of the stacked body 110. Thereby, in the stacking direction of the electrode assembly 11, the interposition part 4 having a shape protruding from the surface 31 of the separator 3 to the electrode 2 side is formed, and the interposition part 4 is joined to each electrode 2 (21 to 23). be able to. And after making the restraint member 13 contact | abut to the termination | terminus electrodes 21 and 23, the secondary battery 1 can be obtained by inject | pouring electrolyte in each layered space S from the liquid inlet which is not shown in figure.

  Next, the effect of the secondary battery 1 of this example is demonstrated. The secondary battery 1 has an interposition part 4 arranged in a layered space S surrounded by an electrode 2, an electrode 2 adjacent to the electrode 2, and a seal part 12. Further, the interposition part 4 is interposed between the electrodes 2 in a state where the two electrodes 2 facing the layered space S are separated from each other, and is joined to each of these electrodes 2.

  Therefore, when the internal pressure in any one of the layered spaces S rises due to gas accumulation, the interposition part 4 increases the distance between the electrodes 2 in the layered space S, or in the layered space S adjacent to the layered space S. Reduction of the distance between the electrodes 2 can be restricted. Therefore, the interposition part 4 can suppress the expansion of the layered space S due to the increase in internal pressure and the compression of the layered space S accompanying the increase in internal pressure.

  Moreover, since the interposition part 4 is arrange | positioned in each layered space S, the expansion | swelling and compression of the layered space S can be suppressed in any layered space S. Therefore, the secondary battery 1 can effectively suppress the deformation of the electrode 2 due to the increase in internal pressure, and thus can suppress an increase in the deviation of the distance between the electrodes 2.

  Moreover, since the secondary battery 1 can suppress the expansion of the layered space S due to the increase in internal pressure in any layered space S, the restraining member 13 while ensuring the effect of suppressing the deformation of the electrode 2 due to the increase in internal pressure. The rigidity can be made lower than before. As a result, the secondary battery 1 can be easily reduced in size and weight.

  Moreover, the interposition part 4 of this example protrudes on the electrode 2 side from the surface 31 of the separator 3 in the stacking direction of the electrode assembly 11. Therefore, the area of the joint part between the electrode 2 and the interposition part 4 can be increased. Therefore, the bonding strength between the electrode 2 and the interposition part 4 can be further increased. As a result, peeling of the interposition part 4 from the electrode 2 can be more effectively suppressed, and as a result, deformation of the electrode 2 due to an increase in internal pressure can be suppressed for a longer period.

  Thus, according to the secondary battery 1, the deformation | transformation of the electrode 2 by an internal pressure rise can be suppressed, and size reduction and weight reduction can be performed easily. In addition, the secondary battery 1 can suppress an increase in the deviation of the distance between the electrodes 2, and can also suppress unevenness of electrode reaction and deterioration of charge / discharge characteristics.

  Moreover, the electrode 2 of the secondary battery 1 of this example is a foil electrode having a metal foil 24 and an active material layer 25 disposed on at least one surface of the metal foil 24. Therefore, the number of electrodes 2 per volume of the secondary battery 1 can be easily increased as compared with the case where a porous electrode is used. As a result, the power density and energy density of the secondary battery 1 can be improved.

  Moreover, the secondary battery 1 of this example includes a metal foil 24 as a current collector, a positive electrode active material layer 25p disposed on the front side surface of the metal foil 24, and a negative electrode active material layer disposed on the back side surface. And a bipolar electrode 22 having 25n. Therefore, a plurality of single cells can be connected in series with a simple configuration in which the bipolar electrodes 22 are stacked. As a result, the electromotive force of the secondary battery 1 can be further increased.

  Further, by using the bipolar electrode 22, the number of single cells can be increased with respect to the total number of electrodes as compared with the case of using a unipolar electrode. Therefore, when the total number of electrodes is the same, the number of single cells can be increased as compared with the case where unipolar electrodes are used. Further, when the number of single cells is the same, the total number of electrodes can be reduced and the size of the secondary battery 1 in the stacking direction can be further reduced as compared with the case where unipolar electrodes are used.

(Example 2)
This example is an example of the secondary battery 102 having the interposition part 402 disposed in the through hole 32 of the separator 302. Of the reference numerals used in and after this embodiment, the same reference numerals as those used in the above-described embodiments indicate the same constituent elements as those in the above-described embodiments unless otherwise specified.

  As shown in FIG. 5, the secondary battery 102 of this example includes, as the electrode 2, termination electrodes 26 and 28 disposed at both ends in the stacking direction of the electrode assembly 11, and between the termination electrode 26 and the termination electrode 28. And a bipolar electrode 27 disposed on the substrate.

  The bipolar electrode 27 includes a rectangular metal foil 24, a positive electrode active material layer 25 p provided on the front side surface of the metal foil 24, and a negative electrode active material layer 25 n provided on the back side surface. Further, the bipolar electrode 27 has an exposed portion 241 where the metal foil 24 is exposed at the center of the positive electrode active material layer 25p and the negative electrode active material layer 25n in a plan view as viewed from the stacking direction of the electrode assembly 11.

  Of the two termination electrodes 26 and 28, the first termination electrode 26 disposed at one end in the stacking direction has the same configuration as the bipolar electrode 27 except that it does not have the positive electrode active material layer 25p. The second termination electrode 28 disposed at the other end in the stacking direction has the same configuration as that of the bipolar electrode 27 except that it does not have the negative electrode active material layer 25n.

  The separator 302 has a rectangular shape in plan view as viewed from the stacking direction of the electrode assembly 11. In addition, a through hole 32 that penetrates the separator 302 in the thickness direction is provided in the center of the separator 302 in a plan view as viewed from the stacking direction of the electrode assembly 11.

  The interposition part 402 has a cylindrical shape and is inserted into the through hole 32 of the separator 302. The end surface of the interposition part 402 is joined to the exposed part 241 of the electrodes 26 to 28 facing the separator 302, respectively. In addition, the interposition part 402 of this example is comprised from the polypropylene.

  In producing the secondary battery 102 of this example, the electrodes 26 to 28 provided with the exposed portion 241, the separator 302 provided with the through hole 32, and the columnar interposed portion 402 are prepared. As a method of forming the exposed portion 241 on the electrodes 26 to 28, for example, after forming the active material layer 25 (25p, 25n) on the metal foil 24, the portion of the active material layer 25 corresponding to the exposed portion 241 is removed. Or, when the active material layer 25 is formed on the metal foil 24, the active material layer 25 is not formed in the portion corresponding to the exposed portion 241 and the active material layer 25 is formed in other portions. There is a way.

  After preparing these members, the electrodes 26 to 28 and the separators 302 are alternately stacked while the interposition portions 402 are disposed in the through holes 32 to produce a stacked body. Thereafter, the electrode assembly 11 can be obtained by compressing in the stacking direction while heating the stack. Others are the same as in the first embodiment.

  As in this example, the exposed portion 241 where the metal foil 24 is exposed is provided on the electrode 2, and the interposed portion 402 is bonded to the active material layer 25 by directly bonding the interposed portion 402 and the metal foil 24 at the exposed portion 241. Compared with the case where it is done, joint strength can be made high. Therefore, peeling of the interposition part 402 from the metal foil 24 can be more effectively suppressed, and deformation of the electrode due to an increase in internal pressure can be suppressed for a longer period. In addition, the secondary battery 102 of this example can achieve the same effects as those of the first embodiment.

Example 3
This example is an example of a secondary battery having a plurality of interposition parts 403 and 404. From the viewpoint of more effectively suppressing the deformation of the electrode 2 due to the increase in internal pressure, it is preferable to arrange the interposition portions 403 and 404 evenly in a plan view as viewed from the stacking direction of the electrode assembly 11.

  For example, as shown in FIG. 6, when each layered space S has two interposition portions 403, each of the two regions R1 and R2 equally divided by a virtual line L1 extending in the short side direction of the separator 303 is provided. It is preferable to arrange the interposition part 403 in the. In this case, it is more preferable to arrange the interposition part 403 at the center of each of the above-described regions R1 and R2 in a plan view as viewed from the stacking direction of the electrode assembly.

  For example, as shown in FIG. 7, when each layered space S has five interposition portions 404, the interposition portions 404 extend in the virtual line L <b> 1 extending in the short side direction of the separator 304 and in the long side direction. It is preferable to arrange one at each of the four regions R1 to R4 equally divided by the virtual line L2 and at the center of the separator 304, that is, at the intersection of the virtual line L1 and the virtual line L2. Further, in this case, it is more preferable to dispose the interposition part 404 at the center of each of the regions R1 to R4 and the center of the separator 304 in a plan view as viewed from the stacking direction of the electrode assembly 11.

  The mode of the secondary battery according to the present invention is not limited to the mode of the above-described embodiment, and the configuration can be changed as appropriate without departing from the spirit of the mode. For example, in Example 1 and Example 2, the example of the secondary battery 1 and 102 having the electrode assembly 11 including the bipolar electrodes 22 and 27 is shown, but the active material having the same polarity on both surfaces of the metal foil 24 is shown. A unipolar electrode with layer 25 can also be incorporated into electrode assembly 11. In this case, the positive electrode and the negative electrode may be alternately arranged, and the separators 3 and 302 and the interposition parts 4 and 402 may be disposed between the positive electrode and the negative electrode.

  Moreover, although Example 1 and Example 2 showed the example of the secondary batteries 1 and 102 which have the electrode assembly 11 provided with the foil electrode, it is also possible to incorporate a porous electrode in the electrode assembly 11. is there.

DESCRIPTION OF SYMBOLS 1,102 Secondary battery 11 Electrode assembly 111 Side peripheral surface 12 Seal part 13 Restraining member 2, 21-23, 26-28 Electrode 20 Peripheral part 3, 302, 303, 304 Separator 4, 402, 403, 404 Interposition part S layered space

Claims (6)

An electrode assembly in which a plurality of electrodes are stacked via a separator;
A seal portion disposed on a peripheral portion of the electrode and covering a side peripheral surface of the electrode assembly;
A constraining member that abuts each end in the stacking direction of the electrode assembly and restrains the electrode assembly in the stacking direction;
The electrode, an electrode adjacent to the electrode, and an interposition part disposed in a layered space surrounded by the seal part,
The interposition part is a secondary battery which is interposed between the electrodes in a state where the two electrodes facing the layered space are separated from each other and joined to each of the electrodes.   The secondary electrode according to claim 1, wherein the electrode includes a metal foil and an active material layer disposed on at least one surface of the metal foil.   The secondary battery according to claim 2, wherein the electrode has an exposed portion in which a part of the metal foil is exposed in the layered space, and the interposition portion is joined to the exposed portion.   The electrode assembly includes a termination electrode disposed at both ends in the stacking direction, and a bipolar electrode disposed between the termination electrodes. The bipolar electrode includes a metal foil and the metal foil. The positive electrode active material layer arrange | positioned on the front side surface of this, and the negative electrode active material layer arrange | positioned on the back side surface of the said metal foil, The 2 of any one of Claims 1-3 Next battery.   The secondary battery according to any one of claims 1 to 4, wherein the interposition part protrudes more toward the electrode than the surface of the separator in the stacking direction of the electrode assembly.   The secondary separator according to any one of claims 1 to 5, wherein the separator has a through hole penetrating in the stacking direction of the electrode assembly, and the interposition portion is disposed in the through hole. battery.

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