Electrode body and energy storage element

Abstract

To provide an electrode body capable of suppressing the occurrence of gaps between electrodes in a wound body in which the electrodes are wound, and a power storage element including the electrode body.SOLUTION: An electrode body includes a wound body 20 having a wound electrode, and a shape-retaining portion 25 having at least one sheet-like member 250 harder than the electrode and maintaining the shape of the wound body, and the at least one sheet-shaped member has a first surface S1 and a second surface S2 that is the back surface of the first surface, and a pair of end portions 25B, which surround the wound body in the winding direction and are joined to each other, have their first surfaces opposed to each other, by arranging the electrode along the outer peripheral surface of the wound body with the first surface facing the wound body, and joining the ends of the electrodes in the winding direction.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to an electrode body in which electrodes are wound, and a power storage element including the electrode body.

Background Art

[0002] Conventionally, a lithium-ion secondary battery including a wound electrode body in which a positive electrode sheet, a negative electrode sheet, and a separator are wound through the separator has been known (see Patent Document 1).

[0003] In this lithium-ion secondary battery, it is necessary to house the wound electrode body in a battery case with the positive electrode sheet, the negative electrode sheet, and the separator in close contact. For this reason, when manufacturing the wound electrode body, after the positive electrode sheet, the negative electrode sheet, and the separator are wound into a cylindrical shape, they are pressed to be flattened so that the positive electrode sheet, the negative electrode sheet, and the separator are in close contact.

[0004] However, in a lithium-ion secondary battery used in an electric vehicle or the like, since a high-areal density and high-density electrode sheet (positive electrode sheet and negative electrode sheet) is wound dozens of turns, the wound electrode body flattened by pressing tries to return to its original cylindrical shape and is deformed, and a gap may occur between the wound positive electrode sheet, negative electrode sheet, and separator.

[0005] When such a gap occurs in the wound electrode body, the diffusion distance of lithium ions inside the wound electrode body increases and the resistance increases. For this reason, in a lithium-ion secondary battery using the wound electrode body in which the gap has occurred, the battery performance deteriorates.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Therefore, an object of the present embodiment is to provide an electrode body capable of suppressing the generation of a gap between electrodes in a wound body in which the electrodes are wound, and a power storage element including the electrode body.

Means for Solving the Problems

[0008] The electrode body of the present embodiment includes a wound body having wound electrodes, and a shape-retaining portion having at least one sheet-like member harder than the electrodes and maintaining the shape of the wound body. The at least one sheet-like member has a first surface and a second surface which is the back surface of the first surface, and is arranged along the outer peripheral surface of the wound body with the first surface facing the wound body, and surrounds the wound body in the winding direction by joining the ends of the electrodes in the winding direction to each other. The joined pair of ends have the first surfaces facing each other.

[0009] According to such a configuration, even in a state before the electrode body is placed in a case, the deformation of the wound body is suppressed by the shape-retaining portion, and thereby the generation of a gap between the electrodes due to the deformation of the wound body is suppressed.

[0010] In the electrode body, the wound body has a separator wound in a state overlapping with the electrodes, and the pair of ends may sandwich the separator with a part of the separator exposed to the outside.

[0011] According to such a configuration, when the electrode body is housed in a case together with an electrolytic solution, the electrolytic solution is supplied to the inside (winding center portion side) of the wound body through the exposed portion of the separator.

[0012] Further, in the electrode body, at least one of the pair of ends has a hole penetrating in the thickness direction, and A part of the separator may be exposed to the outside through the hole.

[0013] According to such a configuration, when the electrode body is housed in the case together with the electrolytic solution, the electrolytic solution is supplied to the inside (winding center portion side) of the wound body through the separator (a part of the separator) exposed to the outside from the hole.

[0014] Further, the energy storage element of the present embodiment includes any one of the above electrode bodies, and a case that houses the electrode body together with the electrolytic solution.

[0015] According to such a configuration, since the shape of the wound body (electrode body) is maintained by the shape-retaining portion, generation of a gap between the electrodes due to deformation of the wound body during manufacturing of the energy storage element or the like is suppressed. As a result, an increase in resistance or the like due to the generation of a gap between the electrodes in the electrode body is suppressed, and as a result, a decrease in performance of the energy storage element including the electrode body is suppressed.

[0016] In the energy storage element, the case has a rectangular parallelepiped shape or a cubic shape with a size corresponding to the electrode body, and houses the electrode body such that the winding axis of the electrode body extends along the facing direction of a pair of opposing wall portions in the rectangular parallelepiped shape or the cubic shape. The pair of end portions in the shape-retaining portion of the electrode body may be located between a curved portion where the outer peripheral surface of the wound body is curved and a corner portion of the case facing the curved portion.

[0017] In this way, by arranging the pair of end portions using the gap (space) generated between the curved portion and the corner portion of the case in the case, a decrease in the energy density in the case is suppressed. That is, by arranging the pair of end portions between the curved portion where the gap is formed and the corner portion of the case regardless of the presence or absence of the arrangement of the pair of end portions, generation of a decrease in the energy density corresponding to the area (volume) occupied by the pair of end portions in the case when arranged at other positions is suppressed.

Advantages of the Invention

[0018] As described above, according to the present embodiment, it is possible to provide an electrode body that can suppress the generation of a gap between electrodes in a wound body in which the electrodes are wound, and a power storage element including this electrode body.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0020] Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 7. Examples of the power storage element include a primary battery, a secondary battery, a capacitor, and the like. In this embodiment, as an example of the power storage element, a rechargeable secondary battery will be described. Note that the names of the constituent members (each constituent element) of this embodiment are those in this embodiment and may be different from the names of the constituent members (each constituent element) in the background art.

[0021] The power storage element of this embodiment is a non-aqueous electrolyte secondary battery. More specifically, the power storage element is a lithium-ion secondary battery that utilizes electron transfer generated by the transfer of lithium ions. This type of power storage element supplies electrical energy. The power storage element is used singly or in plurality. Specifically, the power storage element is used singly when the required output and the required voltage are small. On the other hand, when at least one of the required output and the required voltage is large, the power storage element is combined with other power storage elements and used in a power storage device. In the power storage device, the power storage element used in the power storage device supplies electrical energy.

[0022] As shown in FIGS. 1 to 3, the power storage element includes an electrode body 2 and a case 3 that houses the electrode body 2. Further, the power storage element 1 includes an external terminal 4 that is attached to the case 3 in a state where at least a part thereof is exposed to the outside or an external terminal constituted by a part of the case 3, and a current collector 5 that electrically connects the electrode body 2 and the external terminal 4. Further, the power storage element 1 also includes an insulating member 6 and the like disposed between the electrode body 2 and the case 3. The external terminal 4 of this embodiment is attached to the case 3.

[0023] As shown in FIGS. 4 and 5, the electrode body 2 has a wound body 20 having wound electrodes (a positive electrode 21 and a negative electrode 22), and a shape-retaining portion 25 that maintains the shape of the wound body 20.

[0024] The wound body 20 is composed of wound electrodes (positive electrode 21 and negative electrode 22) and a separator 23. In the wound body 20, the positive electrode 21 and the negative electrode 22 are alternately laminated with the separator 23 interposed therebetween. In this wound body 20, the positive electrode 21 and the negative electrode 22 are laminated in a state of being insulated from each other by the separator 23, and the storage element 1 is charged and discharged by the movement of lithium ions between the positive electrode 21 and the negative electrode 22.

[0025] The positive electrode 21 has a strip-shaped metal foil 211 and a positive electrode active material layer 212 laminated on the metal foil 211. This positive electrode active material layer 212 is laminated on the metal foil 211 with one edge portion (uncovered portion) in the width direction of the metal foil 211 exposed. The metal foil 211 of the present embodiment is, for example, an aluminum foil.

[0026] The negative electrode 22 has a strip-shaped metal foil 221 and a negative electrode active material layer 222 laminated on the metal foil 221. This negative electrode active material layer 222 is laminated on the metal foil 221 with the other edge portion (uncovered portion) in the width direction of the metal foil 221 (on the side opposite to the uncovered portion of the metal foil 211 of the positive electrode 21) exposed. The metal foil 221 of the present embodiment is, for example, a copper foil.

[0027] The separator 23 is an insulating member and is disposed between the positive electrode 21 and the negative electrode 22. Thereby, in the wound body 20, the positive electrode 21 and the negative electrode 22 are insulated from each other. Further, the separator 23 holds the electrolytic solution in the case 3. Thereby, during charging and discharging of the storage element 1, lithium ions can move between the positive electrode 21 and the negative electrode 22 that are alternately laminated with the separator 23 interposed therebetween.

[0028] This separator 23 is strip-shaped and is composed of, for example, a porous membrane such as polyethylene, polypropylene, cellulose, polyamide, etc. The separator 23 of the present embodiment is formed by providing an inorganic layer containing inorganic particles such as SiO2 particles, Al2O3 particles, and boehmite (aluminum hydrate) on a base material formed by a porous membrane. The base material of the separator 23 of the present embodiment is formed of, for example, polyethylene.

[0029] The dimension of the separator 23 in the width direction (X-axis direction) is larger than the width of the negative electrode active material layer 222. The separator 23 is disposed between the positive electrode 21 and the negative electrode 22 which are overlapped in a state where they are displaced in the width direction so that the positive electrode active material layer 212 and the negative electrode active material layer 222 overlap in the thickness direction (lamination direction). At this time, the non-coated portion of the positive electrode 21 and the non-coated portion of the negative electrode 22 do not overlap. That is, the non-coated portion of the positive electrode 21 protrudes in the width direction (a direction orthogonal to the lamination direction) from the region where the positive electrode 21 and the negative electrode 22 overlap, and the non-coated portion of the negative electrode 22 protrudes in the width direction (a direction opposite to the protruding direction of the non-coated portion of the positive electrode 21) from the region where the positive electrode 21 and the negative electrode 22 overlap. In the wound body 20, the positive electrode 21, the negative electrode 22, and the separator 23 are laminated so as to have the above-described positional relationship (relative position). Further, in the wound body 20 of the present embodiment, the non-coated laminated portion 24 in the wound body 20 (electrode body 2) is constituted by a portion where only the non-coated portion of the positive electrode 21 or the non-coated portion of the negative electrode 22 is laminated.

[0030] The non-coated laminated portion 24 is provided at each electrode of the electrode body 2 (wound body 20). That is, the non-coated laminated portion 24 where only the non-coated portion of the positive electrode 21 is laminated constitutes the non-coated laminated portion of the positive electrode in the electrode body 2, and the non-coated laminated portion 24 where only the non-coated portion of the negative electrode 22 is laminated constitutes the non-coated laminated portion of the negative electrode in the electrode body 2.

[0031] The conformal portion 25 has at least one sheet-like member 250 that is harder than the electrodes (the positive electrode 21 and the negative electrode 22). The conformal portion 25 of the present embodiment has two sheet-like members 250. This conformal portion 25 has a conformal portion main body 25A that surrounds the periphery of the wound body 20, and a joining portion 25B that joins the two sheet-like members 250 to each other. This conformal portion main body 25A is composed only of the sheet-like member 250 and has a shape along the outer peripheral surface of the wound body 20. The joining portion 25B is composed of an end portion 251 of the sheet-like member 250 and an adhesive layer 252, and is a strip-like piece that protrudes from the conformal portion main body 25A and extends along the curved portion of the conformal portion main body 25A.

[0032] Each of the two sheet-like members 250 has a first surface S1 and a second surface S2 that is the back surface (opposite surface) of the first surface S1. Each sheet-like member 250 of the present embodiment is a rectangular sheet whose longitudinal direction is the circumferential direction of the wound body 20, and the dimension in the width direction of the sheet-like member 250 is the same as or slightly larger than the dimension in the width direction of the separator 23. The sheet-like member 250 of the present embodiment is formed of a thermosetting resin having resistance to the electrolytic solution, such as a phenolic resin, a melamine resin, or an epoxy resin, and the thickness dimension of the sheet-like member 250 is 0.1 to 10 mm.

[0033] With each of the two sheet-like members 250 having the first surface S1 facing the wound body 20, they are arranged along the outer peripheral surface of the wound body 20, and the corresponding end portions 251 of the adjacent sheet-like members 250 in the circumferential direction of the wound body 20 (that is, the winding direction of the electrodes 21 and 22 in the wound body 20) are joined to each other, thereby forming the conformal portion 25. At this time, the pair of joined end portions 251 have the first surfaces S1 facing each other.

[0034] In the conforming portion 25 of the present embodiment, the pair of end portions 251 are joined (adhered, etc.) via an adhesive layer 252 formed of a thermoplastic resin having resistance to an electrolytic solution such as polyethylene, acrylic resin, or polyester. On the other hand, the portion of the sheet-like member 250 excluding the both end portions 251 in the circumferential direction (the portion constituting the conforming portion main body 25A, that is, the portion arranged along the circumferential surface of the winding body 20 with the first surface S1 facing the winding body 20) 253 is in contact with the circumferential surface of the winding body 20, but is not joined (adhered, stuck, etc.) to the circumferential surface.

[0035] The joint portion 25B constituted by the pair of end portions 251 and the adhesive layer 252 extends from the top of the portion (curved portion) 20R where the respective electrodes 21, 22 and the separator 23 are laminated in a curved state in the winding body 20, that is, the portion located on the outermost side of the curved portion 20R when viewed from the direction of the winding axis C of the winding body 20.

[0036] Returning to FIGS. 1 to 3, the case 3 has a rectangular parallelepiped shape or a cubic shape with a size corresponding to the electrode body 2, and houses the electrode body 2 (winding body 20) such that the winding axis C of the electrode body 2 (winding body 20) extends along the opposing direction of a pair of opposing wall portions (short wall portions) 314 in the rectangular parallelepiped or cubic shape. Specifically, the case 3 has a case body 31 having an opening and a cover plate 32 that closes (seals) the opening of the case body 31. The case 3 houses an electrolytic solution in the internal space together with the electrode body 2. For this reason, the case 3 is formed of a metal having resistance to the electrolytic solution. The case 3 of the present embodiment is formed of an aluminum-based metal material such as aluminum or an aluminum alloy, for example.

[0037] Here, the electrolytic solution is a non-aqueous electrolytic solution. The electrolytic solution is obtained by dissolving an electrolyte salt in an organic solvent. The organic solvent is, for example, cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The electrolyte salt is LiClO4, LiBF4, LiPF6, etc. The electrolytic solution of the present embodiment is obtained by dissolving 1 mol / L of LiPF6 in a mixed solvent in which propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are adjusted at a ratio of propylene carbonate:dimethyl carbonate:ethyl methyl carbonate = 3:2:5.

[0038] The case body 31 includes a plate-shaped closing portion 311 and a cylindrical body portion (peripheral wall) 312 connected to the periphery of the closing portion 311.

[0039] The closing portion 311 is a portion located at the lower end of the case body 31 when the case body 31 is arranged with the opening facing upward (that is, the bottom wall of the case body 31 when the opening faces upward). The closing portion 311 is rectangular when viewed from the normal direction of the closing portion 311.

[0040] Hereinafter, the long side direction of the closing portion 311 is defined as the X axis of the rectangular coordinate system, the short side direction of the closing portion 311 is defined as the Y axis of the rectangular coordinate system, and the normal direction of the closing portion 311 is defined as the Z axis of the rectangular coordinate system.

[0041] The body portion 312 has a rectangular tube shape, more specifically, a flat rectangular tube shape. The body portion 312 has a pair of long wall portions 313 extending from the long sides at the periphery of the closing portion 311 and a pair of short wall portions 314 extending from the short sides at the periphery of the closing portion 311. That is, the pair of long wall portions 313 face each other with a space therebetween in the Y-axis direction (specifically, a space corresponding to the short side at the periphery of the closing portion 311), and the pair of short wall portions 314 face each other with a space therebetween in the X-axis direction (specifically, a space corresponding to the long side at the periphery of the closing portion 311). The rectangular tube-shaped body portion 312 is formed by connecting the corresponding (specifically, facing in the Y-axis direction) ends of the pair of long wall portions 313 with the short wall portions 314, respectively.

[0042] As described above, the case body 31 has a rectangular tube shape (i.e., a bottomed rectangular tube shape) with one end in the opening direction (Z-axis direction) closed. In this case body 31, the electrode body 2 is accommodated with the winding axis C direction oriented in the X-axis direction (the direction in which the pair of short wall portions 314 face each other) (see FIG. 2).

[0043] The cover plate 32 is a plate-like member that closes the opening of the case body 31. Specifically, the cover plate 32 is a plate-like member having a contour shape corresponding to the opening peripheral portion 34 of the case body 31 when viewed from the Z-axis direction. That is, the cover plate 32 is a rectangular plate material that is long in the X-axis direction when viewed from the Z-axis direction.

[0044] The case 3 is formed by joining the cover plate 32 to the case body 31 in a state where the peripheral portion of the cover plate 32 is overlapped with the opening peripheral portion 34 of the case body 31. In the case 3 of the present embodiment, the opening peripheral portion 34 of the case body 31 and the peripheral portion of the cover plate 32 are joined by welding.

[0045] The external terminal 4 is a portion that is electrically connected to the external terminal of another power storage element or an external device or the like. The external terminal 4 is formed of a conductive member. For example, the external terminal 4 is formed of a highly weldable metal material such as an aluminum-based metal material such as aluminum or an aluminum alloy, or a copper-based metal material such as copper or a copper alloy.

[0046] The current collector 5 is disposed within the case 3 and is directly or indirectly connected to the electrode body 2 (wound body 20) so as to be electrically conductive. The current collector 5 of the present embodiment is connected to the electrode body 2 through a clip member 50 so as to be electrically conductive. That is, the power storage element 1 includes a clip member 50 that electrically connects the electrode body 2 and the current collector 5.

[0047] The current collector 5 is formed of a conductive member. The current collector 5 is disposed along the inner surface of the case 3. The current collector 5 of the present embodiment electrically connects the external terminal 4 and the clip member 50. Specifically, the current collector 5 has a first connection portion 51 that is electrically connected to the external terminal 4, a second connection portion 52 that is electrically connected to the electrode body 2, and a bent portion 53 that connects the first connection portion 51 and the second connection portion 52. In the current collector 5, the bent portion 53 is disposed near the boundary between the cover plate 32 and the short wall portion 314 within the case 3, the first connection portion 51 extends from the bent portion 53 along the cover plate 32, and the second connection portion 52 extends from the bent portion 53 along the short wall portion 314. The second connection portion 52 of the present embodiment is joined to the clip member 50 by, for example, ultrasonic welding.

[0048] The current collector 5 configured as described above is disposed on the positive electrode and the negative electrode of the power storage element 1, respectively. In the power storage element 1 of the present embodiment, the current collector 5 is disposed on the non-coated laminated portion 24 of the positive electrode and the non-coated laminated portion 24 of the negative electrode of the wound body 20 within the case 3, respectively. The current collector 5 for the positive electrode and the current collector 5 for the negative electrode are formed of different materials. Specifically, the current collector 5 for the positive electrode is formed of, for example, aluminum or an aluminum alloy, and the current collector 5 for the negative electrode is formed of, for example, copper or a copper alloy.

[0049] The clip member 50 sandwiches the positive electrode 21 or the negative electrode 22 laminated in the non-coated laminated portion 24 of the wound body 20 so as to bundle them. Thereby, the clip member 50 surely electrically connects the positive electrodes 21 or the negative electrodes 22 laminated in the non-coated laminated portion 24. The clip member 50 of the present embodiment is formed by bending a plate-shaped metal material so that the cross section is U-shaped.

[0050] The insulating member 6 is disposed between the case 3 (specifically, the case body 31) and the electrode body 2. This insulating member 6 is formed in a bag shape by bending a sheet-like member having insulation that has been cut into a predetermined shape.

[0051] Next, a method for manufacturing the electrode body 2 will be described with reference to FIGS. 6 and 7 as well.

[0052] First, a wound body 20 is formed by winding a positive electrode 21, a negative electrode 22, and a separator 23 such that the separator 23 is positioned between the positive electrode 21 and the negative electrode 22. At this time, the wound body 20 has a hollow portion 20a formed therein when viewed from the direction of the winding axis C (see FIG. 6).

[0053] Next, a shape-retaining portion 25 is formed around the wound body 20. Specifically, two sheet-like members 250 in a state before being thermoset (flexible state) are disposed around the wound body 20, and a press for flattening the wound body 20 and a heat press for curing each sheet-like member 250 and joining (adhering, etc.) the sheet-like members 250 to each other are performed simultaneously. Specifically, it is as follows.

[0054] As shown in FIG. 6, two sheet-like members 250 having a layer (adhesive layer) 252 of a thermoplastic resin on the first surface S1 side of both end portions 251 are disposed such that the first surfaces S1 face each other and the wound body 20 is positioned therebetween.

[0055] Subsequently, as shown in FIG. 7, a pair of first press plates P1 sandwich and heat-press a portion 253 that covers the winding body 20 in the two sheet-like members 250. In the present embodiment, heat-pressing is performed at a temperature of 220° C. and a pressure of 2 MPa for 5 seconds. As a result, the portion of the two sheet-like members 250 where heat is applied by the first press plates P1 is cured (thermally cured) in a state where the winding body 20 is sufficiently flattened and the hollow portion 20a is sufficiently crushed, and the shape-retaining portion main body 25A is formed. In FIG. 7, the first press plates P1 are in contact only with the portion where the winding body 20 is flattened and flattened, but the first press plates P1 may be in contact with the entire portion corresponding to the shape-retaining portion main body 25A in the sheet-like member 250 (that is, also with the curved portion). Further, the first press plates P1 may press until the hollow portion 20a disappears, or may press to such an extent that a slight amount remains.

[0056] Also, simultaneously with the heat-pressing by the pair of first press plates P1, a pair of second press plates P2 sandwich and heat-press one end portions 251 of the two sheet-like members 250 where the adhesive layers 252 face each other, and a pair of third press plates P3 sandwich and heat-press the other end portions 251 of the two sheet-like members 250 where the adhesive layers 252 face each other. As a result, the opposing one end portions 251 are cured (thermally cured) and the adhesive layers 252 are adhered to each other. Also, the opposing other end portions 251 are cured (thermally cured) and the adhesive layers 252 are adhered to each other (see FIG. 7). At this time, the adhesive layers 252 arranged at the respective opposing end portions 251 are adhered by heat-pressing to become integrated, that is, they constitute one adhesive layer 252.

[0057] After the heat-pressing by each of these press plates P1, P2, and P3, when the shape-retaining portion 25 has sufficiently cooled, the electrode body 2 provided with the shape-retaining portion 25 around the winding body 20 is completed.

[0058] According to the above electrode body 2, even before the electrode body 2 is placed in the case 3, the deformation of the wound body 20 (in the case of this embodiment, for example, the deformation such that the flat wound body returns to the state before pressing, that is, the hollow portion 20a expands in the Y-axis direction) is suppressed by the shape-retaining portion 25. As a result, the generation of a gap between the electrodes 21 and 22 due to the deformation of the wound body 20 is suppressed.

[0059] In addition, since the shape of the wound body 20 (electrode body 2) is maintained by the shape-retaining portion 25, the generation of a gap between the electrodes 21 and 22 due to the deformation of the wound body 20 is suppressed during the manufacture of the energy storage element 1 or the like. As a result, an increase in resistance or the like caused by the generation of a gap between the electrodes 21 and 22 in the electrode body 2 is suppressed. As a result, a decrease in performance of the energy storage element 1 including the electrode body 2 is suppressed.

[0060] Note that the electrode body of the present invention and the energy storage element including the electrode body are not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Further, a part of the configuration of one embodiment can be deleted.

[0061] The specific configuration of the shape-retaining portion 25 is not limited. For example, the shape-retaining portion 25 of the above embodiment has two sheet-like members 250, but may have one sheet-like member 250 or three or more sheet-like members 250. When the shape-retaining portion 25 has one sheet-like member 250, both ends of the sheet-like member 250 are joined to each other with the first surfaces S1 facing each other to form a joining portion 25B. When there are three or more sheet-like members 250, the end portions 251 of the sheet-like members 250 adjacent to each other in the circumferential direction (winding direction) of the wound body 20 are joined to each other with the first surfaces S1 facing each other to form a joining portion 25B.

[0062] Also, in the shape-retaining portion 25 of the above embodiment, the joint portion 25B protrudes from the top of the curved portion 20R of the wound body 20, but it may protrude from other portions of the curved portion 20R, or may protrude from the flat portion of the wound body 20 (the portion where the respective electrodes 21, 22, and separator 23 are laminated in a flat state: the portion between the two curved portions 20R in the wound body 20).

[0063] When the joint portion 25B protrudes from other portions (portions other than the top) of the curved portion 20R, for example, as shown in FIG. 8, it may be located between the curved portion 20R (the portion where the outer peripheral surface is curved) of the wound body 20 and the corner portion of the case 3 facing the curved portion 20R. In this way, by arranging the joint portion 25B (the pair of end portions 251) using the gap (space) generated between the curved portion 20R and the corner portion of the case 3 in the case 3, a decrease in the energy density in the case 3 can be suppressed. That is, by arranging the joint portion 25B between the curved portion 20R where the gap is formed and the corner portion of the case 3 regardless of the presence or absence of the arrangement of the joint portion 25B, the occurrence of a decrease in the energy density (specifically, the decrease in the energy density corresponding to the region (volume) occupied by the joint portion 25B in the case 3) when arranged at other positions can be suppressed.

[0064] Also, the joint portion 25B of the shape-retaining portion 25 does not have to extend straight outward from the outer peripheral surface of the wound body 20 (in the example of the above embodiment, in the radial direction of the curved portion 20R as viewed from the direction of the winding axis C). The joint portion 25B may be curved, bent, etc. in the middle, or may extend in the winding direction along the outer peripheral surface of the wound body 20.

[0065] Further, the joint portion 25B of the shape-retaining portion 25 may sandwich the separator 23 with a part of the separator 23 exposed to the outside (outside the electrode body 2). Specifically, as shown in FIG. 9, a pair of end portions 251 may sandwich the separator 23 such that a part of the separator 23 protrudes (is exposed) outward from the edge of the joint portion 25B. Also, as shown in FIG. 10, at least one of the pair of end portions 251 constituting the joint portion 25B may have a hole (through-hole) 251a penetrating in the thickness direction of the end portion 251, and a part of the separator 23 (that is, a part of the portion of the separator 23 sandwiched between the pair of end portions 251) may be exposed to the outside through the through-hole 251a.

[0066] In the electrode body 2 of the above embodiment, since the shape-retaining portion 25 made of resin covers the outermost peripheral separator 23 of the wound body 20, even when the electrode body 2 is housed in the case 3 together with the electrolytic solution, the contact area of the separator 23 with the electrolytic solution is small. However, if a part of the separator 23 is exposed outside the electrode body 2 as described above, when the electrode body 2 is housed in the case 3 together with the electrolytic solution, the electrolytic solution is sufficiently supplied to the inside (the winding center portion side) of the wound body 20 through the exposed portion of the separator 23.

[0067] Also, the adhesive layer 252 of the pair of end portions 251 constituting the joint portion 25B is made of a thermoplastic resin, but is not limited to this configuration and may be made of an adhesive containing a thermoplastic resin. Further, the adhesive layer 252 may be made of a reaction-type adhesive, a pressure-sensitive adhesive, or the like.

[0068] Also, the material constituting the sheet-like member 250 constituting the shape-retaining portion 25 is not limited to a thermosetting resin. For example, the sheet-like member 250 may be made of a photocurable resin.

[0069] Also, in the shape-retaining portion 25 of the above embodiment, the shape-retaining portion main body 25A is not joined to the outer peripheral surface of the wound body 20 by adhesion or the like, but is not limited to this configuration. The shape-retaining portion main body 25A may be joined to the outer peripheral surface of the wound body 20 by adhesion or the like.

[0070] Further, in the above-described embodiment, the case where the power storage element is used as a non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) capable of charging and discharging has been described. However, the type and size (capacity) of the power storage element are arbitrary. Also, in the above-described embodiment, a lithium ion secondary battery has been described as an example of the power storage element, but the present invention is not limited thereto. For example, the present invention is applicable to various secondary batteries, other primary batteries, and power storage elements of capacitors such as electric double layer capacitors.

[0071] The power storage element (for example, a battery) 1 may be used in a power storage device (when the power storage element is a battery, a battery module) 11 as shown in FIG. 11. The power storage device 11 includes at least two power storage elements 1 and a bus bar member 12 that electrically connects two (different) power storage elements 1 to each other. In this case, it is sufficient that the technology of the present invention is applied to at least one power storage element 1.

Explanation of Reference Numerals

[0072] 1... Power storage element, 2... Electrode body, 20... Wound body, 20R... Curved portion, 20a... Hollow portion, 21... Positive electrode (electrode), 211... Metal foil, 212... Positive electrode active material layer, 22... Negative electrode (electrode), 221... Metal foil, 222... Negative electrode active material layer, 23... Separator, 24... Non-coated laminated portion, 25... Shape-retaining portion, 25A... Shape-retaining portion main body, 25B... Joint portion (pair of end portions), 250... Sheet-like member, 251... End portion, 251a... Through hole (hole), 252... Adhesive layer, 3... Case, 31... Case main body, 311... Closing portion, 312... Barrel portion, 313... Long wall portion, 314... Short wall portion, 32... Cover plate, 34... Opening peripheral edge portion, 4... External terminal, 5... Current collector, 50... Clip member, 51... First connection portion, 52... Second connection portion, 53... Bent portion, 6... Insulating member, 11... Power storage device, 12... Bus bar member, C... Winding shaft, P1... First pressing plate, P2... Second pressing plate, P3... Third pressing plate, S1... First surface, S2... Second surface

Claims

1. An electrode body housed in a case together with an electrolyte, a wound body having a wound sheet-like electrode, and a shape-retaining portion having at least one sheet-like member that is harder than the electrode and is difficult to deform and that maintains the shape of the wound body. The at least one sheet-like member has a first surface and a second surface that is the back surface of the first surface, and is disposed along the outer peripheral surface of the wound body with the first surface facing the wound body, and the wound body is surrounded in the winding direction by joining the ends of the electrode in the winding direction to each other. The joined pair of ends have the first surfaces facing each other. An electrode body.

2. The wound body has a separator wound in a state overlapping the electrode, and the pair of ends sandwich the separator with a part of the separator exposed to the outside. The electrode body according to claim 1.

3. At least one of the pair of ends has a hole penetrating in the thickness direction, and a part of the separator is exposed to the outside through the hole. The electrode body according to claim 2.

4. An electrode body according to any one of claims 1 to 3, and a case that houses the electrode body together with an electrolyte. A storage element.

5. The case has a rectangular parallelepiped shape or a cubic shape with a size corresponding to the electrode body, and houses the electrode body such that the winding axis of the electrode body extends along the facing direction of a pair of opposing wall portions in the rectangular parallelepiped shape or the cubic shape. The pair of ends in the shape-retaining portion of the electrode body are located between a curved portion where the outer peripheral surface of the wound body is curved and a corner portion of the case facing the curved portion. The storage element according to claim 4.

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