JP7695638B2 - Electrode body and storage element - Google Patents

Description

The present invention relates to an electrode body in which electrodes are wound, and an energy storage element that includes this electrode body.

Lithium ion secondary batteries have been known that include a wound electrode assembly in which a positive electrode sheet and a negative electrode sheet are wound with a separator interposed therebetween (see Patent Document 1).

In this lithium-ion secondary battery, the wound electrode body needs to be stored in the battery case with the positive electrode sheet, negative electrode sheet, and separator in close contact with each other. For this reason, when manufacturing the wound electrode body, the positive electrode sheet, negative electrode sheet, and separator are wound into a cylindrical shape, and then pressed to flatten the shape, thereby causing the positive electrode sheet, negative electrode sheet, and separator to be in close contact with each other.

However, in lithium-ion secondary batteries used in electric vehicles and the like, high-density electrode sheets (positive and negative electrode sheets) with a high basis weight are wound up into dozens of turns, and the rolled electrode body, which has been flattened by pressing, may deform as it tries to return to its original cylindrical shape, resulting in gaps being formed between the rolled positive and negative electrode sheets and separator.

When such gaps occur in the wound electrode body, the diffusion distance of lithium ions inside the wound electrode body increases, and resistance increases. As a result, the battery performance of a lithium ion secondary battery using a wound electrode body in which such gaps occur decreases.

JP 2010-198987 A

Therefore, the present embodiment aims to provide an electrode body that can suppress the occurrence of gaps between electrodes in a wound body in which the electrodes are wound, and an energy storage element that includes this electrode body.

The electrode body of this embodiment is
a wound body having a wound electrode;
a shape retaining portion having at least one sheet-like member harder than the electrode and retaining the shape of the wound body;
the at least one sheet-like member has a first surface and a second surface that is a reverse surface of the first surface, is disposed along an 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 ends of the electrodes in the winding direction to each other,
The pair of joined ends have the first surfaces facing each other.

With this configuration, even before the electrode body is placed in the case, the shape-retaining portion suppresses deformation of the wound body, thereby suppressing the occurrence of gaps between the electrodes due to deformation of the wound body.

In the electrode body,
The wound body has a separator wound in a state overlapping the electrode,
The pair of end portions may sandwich the separator in a state where a part of the separator is exposed to the outside.

With this configuration, the electrode body is housed in a case together with the electrolyte, and the electrolyte is supplied to the inside of the wound body (toward the center of the winding) through the exposed portion of the separator.

In addition, in the electrode body,
At least one of the pair of ends has a hole penetrating in a thickness direction,
A portion of the separator may be exposed to the outside through the hole.

With this configuration, the electrode body is housed in the case together with the electrolyte, and the electrolyte is supplied to the inside of the wound body (toward the center of the winding) through the separator (the portion of the separator) exposed to the outside through the hole.

In addition, the energy storage element of this embodiment has
Any one of the above electrode bodies;
and a case that houses the electrode body together with an electrolyte.

With this configuration, the shape of the wound body (electrode body) is maintained by the shape retention section, so that the occurrence of gaps between the electrodes due to deformation of the wound body during the manufacture of the energy storage element, etc., is suppressed. This suppresses increases in resistance and other problems caused by gaps occurring between the electrodes in the electrode body, and as a result, performance degradation in the energy storage element including the electrode body is suppressed.

In the energy storage element,
the case has a rectangular parallelepiped or cubic shape having a size corresponding to the electrode body, and accommodates the electrode body such that a winding axis of the electrode body is aligned with a direction in which a pair of opposing wall portions of the rectangular parallelepiped or cubic shape face each other;
The pair of ends of the shape-retaining portion of the electrode body may be located between a curved portion where the outer circumferential surface of the wound body is curved and a corner of the case opposite the curved portion.

In this way, by arranging the pair of ends in the case by utilizing the gap (space) that occurs between the curved portion and the corner of the case, the decrease in energy density within the case is suppressed. In other words, regardless of whether the pair of ends are arranged, by arranging the pair of ends between the curved portion where a gap is formed and the corner of the case, the decrease in energy density caused by the area (volume) that the pair of ends occupy within the case, which occurs when the pair of ends are arranged in other positions, is suppressed.

As described above, this embodiment can provide an electrode body that can suppress the occurrence of gaps between electrodes in a wound body in which the electrodes are wound, and an energy storage element that includes this electrode body.

FIG. 1 is a perspective view of an energy storage element according to the present embodiment. FIG. 2 is an exploded perspective view of the energy storage element. FIG. 3 is a vertical cross-sectional view of the energy storage element. FIG. 4 is a diagram for explaining the configuration of the wound body. FIG. 5 is a cross-sectional view of the electrode body taken along the line VV in FIG. FIG. 6 is a schematic diagram for explaining the manufacturing method of the electrode assembly, which is a schematic diagram before heat pressing. FIG. 7 is a schematic diagram for explaining the manufacturing method of the electrode assembly, and is a schematic diagram showing the electrode assembly in the heat press state. FIG. 8 is a vertical cross-sectional view of an energy storage element according to another embodiment. FIG. 9 is a partially enlarged view of an electrode assembly according to another embodiment. FIG. 10 is a partially enlarged view of an electrode assembly according to another embodiment. FIG. 11 is a schematic diagram of an electricity storage device including the electricity storage element.

One embodiment of the present invention will be described below with reference to Figs. 1 to 7. Examples of energy storage elements include primary batteries, secondary batteries, and capacitors. In this embodiment, a chargeable and dischargeable secondary battery will be described as an example of an energy storage element. Note that the names of the components (elementary components) in this embodiment are those used in this embodiment and may differ from the names of the components (elementary components) in the background art.

The energy storage element of this embodiment is a non-aqueous electrolyte secondary battery. More specifically, the energy storage element is a lithium ion secondary battery that utilizes electron transfer that occurs with the transfer of lithium ions. This type of energy storage element supplies electrical energy. Energy storage elements are used singly or in multiples. Specifically, an energy 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 energy storage element is used in combination with other energy storage elements in an energy storage device. In the energy storage device, the energy storage element used in the energy storage device supplies electrical energy.

As shown in Figs. 1 to 3, the energy storage element 1 comprises an electrode body 2 and a case 3 that houses the electrode body 2. The energy storage element 1 also comprises an external terminal 4 attached to the case 3 with at least a portion of it exposed to the outside or an external terminal formed by a portion of the case 3, and a current collector 5 that provides electrical continuity between the electrode body 2 and the external terminal 4. The energy storage element 1 also comprises an insulating member 6 and the like that is disposed between the electrode body 2 and the case 3. In this embodiment, the external terminal 4 is attached to the case 3.

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

The wound body 20 is composed of wound electrodes (positive electrode 21 and negative electrode 22) and a separator 23, and in the wound body 20, the positive electrode 21 and the negative electrode 22 are alternately stacked with the separator 23 interposed therebetween. In this wound body 20, the positive electrode 21 and the negative electrode 22 are stacked in a state 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.

The positive electrode 21 has a strip-shaped metal foil 211 and a positive electrode active material layer 212 that is overlaid on the metal foil 211. The positive electrode active material layer 212 is overlaid 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 in this embodiment is, for example, an aluminum foil.

The negative electrode 22 has a strip-shaped metal foil 221 and a negative electrode active material layer 222 that is overlaid on the metal foil 221. The negative electrode active material layer 222 is overlaid on the metal foil 221 with the other edge portion (uncovered portion) of the metal foil 221 in the width direction (opposite the uncovered portion of the metal foil 211 of the positive electrode 21) exposed. The metal foil 221 in this embodiment is, for example, a copper foil.

The separator 23 is an insulating member and is disposed between the positive electrode 21 and the negative electrode 22. This insulates the positive electrode 21 and the negative electrode 22 from each other in the wound body 20. The separator 23 also holds the electrolyte in the case 3. This allows lithium ions to move between the positive electrodes 21 and the negative electrodes 22 that are alternately stacked with the separator 23 in between when the energy storage element 1 is charged or discharged.

The separator 23 is strip-shaped and is made of a porous film _of , for example, polyethylene, polypropylene, cellulose, polyamide, etc. The separator 23 of this embodiment is formed by providing an inorganic layer containing inorganic particles such as _SiO2 particles, _Al2O3 particles, boehmite (alumina hydrate), etc., on a substrate formed of a porous film. The substrate of the separator 23 of this embodiment is made of, for example, polyethylene.

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 stacked in a state where the positive electrode active material layer 212 and the negative electrode active material layer 222 are shifted in the width direction so that they overlap in the thickness direction (stacking direction). At this time, the non-coated portion of the positive electrode 21 does not overlap with the non-coated portion of the negative electrode 22. That is, the non-coated portion of the positive electrode 21 protrudes in the width direction (direction perpendicular to the stacking direction) from the overlapping region of the positive electrode 21 and the negative electrode 22, and the non-coated portion of the negative electrode 22 protrudes in the width direction (opposite to the protruding direction of the non-coated portion of the positive electrode 21) from the overlapping region of the positive electrode 21 and the negative electrode 22. In the wound body 20, the positive electrode 21, the negative electrode 22, and the separator 23 are stacked so as to have the above-mentioned positional relationship (relative position). In addition, in the wound body 20 of this embodiment, the uncoated laminated portion 24 in the wound body 20 (electrode body 2) is formed by a portion where only the uncoated portion of the positive electrode 21 or the uncoated portion of the negative electrode 22 is laminated.

The non-coated laminated portion 24 is provided on each electrode of the electrode body 2 (wound body 20). That is, the non-coated laminated portion 24 in which 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 in which 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.

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

Each of the two sheet-like members 250 has a first surface S1 and a second surface S2 which is the back surface (opposite surface) of the first surface S1. In this embodiment, each sheet-like member 250 is a rectangular sheet whose longitudinal direction is the circumferential direction of the wound body 20, and the width dimension of the sheet-like member 250 is the same as or slightly larger than the width dimension of the separator 23. In this embodiment, the sheet-like member 250 is formed from a thermosetting resin that is resistant to the electrolyte, such as phenolic resin, melamine resin, or epoxy resin, and the thickness dimension of the sheet-like member 250 is 0.1 to 10 mm.

The two sheet-like members 250 are arranged along the outer circumferential surface of the wound body 20 with their first surfaces S1 facing the wound body 20, and corresponding end portions 251 of the sheet-like members 250 adjacent to each other in the circumferential direction of the wound body 20 (i.e., the winding direction of the electrodes 21, 22 in the wound body 20) are joined together to form the shape-retaining portion 25. At this time, the pair of joined end portions 251 face each other with their first surfaces S1 facing each other.

In the shape-retaining portion 25 of this embodiment, a pair of ends 251 are joined (glued, etc.) via an adhesive layer 252 formed of a thermoplastic resin resistant to the electrolyte, such as polyethylene, acrylic resin, or polyester. On the other hand, the portion 253 of the sheet-like member 250 excluding both circumferential ends 251 (the portion constituting the shape-retaining portion main body 25A, i.e., the portion arranged along the circumferential surface of the wound body 20 with the first surface S1 facing the wound body 20) is in contact with the circumferential surface of the wound body 20 but is not joined (glued, adhered, etc.) to the circumferential surface.

The joint 25B formed by the pair of ends 251 and the adhesive layer 252 extends from the top of the portion (curved portion) 20R where the electrodes 21, 22 and the separator 23 are stacked in a curved state in the wound body 20, that is, from the portion located at the outermost side of the curved portion 20R when viewed from the direction of the winding axis C of the wound body 20.

Returning to Figures 1 to 3, the case 3 has a rectangular or cubic shape with a size corresponding to the electrode body 2, and houses the electrode body 2 so that the winding axis C of the electrode body 2 (wound body 20) is aligned with the opposing direction of a pair of opposing walls (short wall portions) 314 in the rectangular or cubic shape. Specifically, the case 3 has a case body 31 with an opening, and a cover plate 32 that blocks (closes) the opening of the case body 31. The case 3 houses the electrolyte in its internal space together with the electrode body 2. For this reason, the case 3 is formed of a metal that is resistant to the electrolyte. The case 3 in this embodiment is formed of, for example, aluminum or an aluminum-based metal material such as an aluminum alloy.

Here, the electrolyte is a non-aqueous electrolyte. The electrolyte is obtained by dissolving an electrolyte salt in an organic solvent. The organic solvent is, for example, a cyclic carbonate ester such as propylene carbonate and ethylene carbonate, or a chain carbonate such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The electrolyte salt is LiClO ₄ , LiBF ₄ , LiPF ₆ , or the like. The electrolyte of this embodiment is a mixed solvent prepared by adjusting propylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a ratio of propylene carbonate:dimethyl carbonate:ethyl methyl carbonate=3:2:5, and dissolving 1 mol/L of LiPF ₆ .

The case body 31 comprises a plate-shaped blocking portion 311 and a cylindrical body portion (peripheral wall) 312 connected to the periphery of the blocking portion 311.

The blocking portion 311 is a portion that is located at the bottom end of the case body 31 when the case body 31 is placed with the opening facing upward (i.e., it becomes the bottom wall of the case body 31 when the opening faces upward). The blocking portion 311 is rectangular when viewed from the normal direction of the blocking portion 311.

In the following, the long side direction of the blocking portion 311 is the X-axis of the Cartesian coordinate system, the short side direction of the blocking portion 311 is the Y-axis of the Cartesian coordinate system, and the normal direction of the blocking portion 311 is the Z-axis of the Cartesian coordinate system.

The body 312 has a rectangular tube shape, more specifically, a flattened rectangular tube shape. The body 312 has a pair of long wall portions 313 extending from the long sides at the periphery of the blocking portion 311, and a pair of short wall portions 314 extending from the short sides at the periphery of the blocking portion 311. That is, the pair of long wall portions 313 face each other at a distance in the Y-axis direction (more specifically, a distance corresponding to the short sides at the periphery of the blocking portion 311), and the pair of short wall portions 314 face each other at a distance in the X-axis direction (more specifically, a distance corresponding to the long sides at the periphery of the blocking portion 311). The short wall portions 314 connect the corresponding ends of the pair of long wall portions 313 (more specifically, facing each other in the Y-axis direction), thereby forming the rectangular tube-shaped body 312.

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

The cover plate 32 is a plate-shaped member that closes the opening of the case body 31. Specifically, the cover plate 32 is a plate-shaped member that has a contour shape that corresponds to the opening periphery 34 of the case body 31 when viewed from the Z-axis direction. In other words, the cover plate 32 is a rectangular plate material that is long in the X-axis direction when viewed from the Z-axis direction.

The cover plate 32 is joined to the case body 31 with the peripheral portion of the cover plate 32 overlapping the opening peripheral portion 34 of the case body 31, thereby forming the case 3. In the case 3 of this embodiment, the opening peripheral portion 34 of the case body 31 and the peripheral portion of the cover plate 32 are joined by welding.

The external terminal 4 is a portion that is electrically connected to an external terminal of another storage element or an external device. The external terminal 4 is formed of a material having electrical conductivity. For example, the external terminal 4 is formed of a metal material with high weldability, 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.

The current collector 5 is disposed in the case 3 and is directly or indirectly connected to the electrode body 2 (wound body 20) so as to be conductive. In this embodiment, the current collector 5 is connected to the electrode body 2 via a clip member 50 so as to be conductive. That is, the energy storage element 1 includes a clip member 50 that connects the electrode body 2 and the current collector 5 so as to be conductive.

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

The current collectors 5 configured as described above are disposed on the positive and negative electrodes of the energy storage element 1. In the energy storage element 1 of this embodiment, the current collectors 5 are disposed on the positive electrode uncoated laminated portion 24 of the wound body 20 and the negative electrode uncoated laminated portion 24 within the case 3. The positive electrode current collector 5 and the negative electrode current collector 5 are formed of different materials. Specifically, the positive electrode current collector 5 is formed of, for example, aluminum or an aluminum alloy, and the negative electrode current collector 5 is formed of, for example, copper or a copper alloy.

The clip member 50 clamps the positive electrodes 21 or negative electrodes 22 stacked in the uncoated laminated portion 24 of the wound body 20 so as to bundle them together. In this way, the clip member 50 reliably establishes electrical continuity between the positive electrodes 21 or the negative electrodes 22 stacked in the uncoated laminated portion 24. The clip member 50 of this embodiment is formed by bending a plate-shaped metal material so that the cross section is U-shaped.

The insulating member 6 is disposed between the case 3 (specifically, the case body 31) and the electrode body 2. The insulating member 6 is formed into a bag shape by folding an insulating sheet-like member cut into a predetermined shape.

Next, the manufacturing method of the electrode body 2 will be explained with reference to Figures 6 and 7.

First, the positive electrode 21, the negative electrode 22, and the separator 23 are wound so that the separator 23 is located between the positive electrode 21 and the negative electrode 22, thereby forming the wound body 20. At this time, the wound body 20 is in a state in which a hollow portion 20a is formed when viewed from the direction of the winding axis C (see FIG. 6).

Next, a shape-retaining portion 25 is formed around the wound body 20. Specifically, two sheet-like members 250 in a state before being thermally cured (soft state) are placed around the wound body 20, and pressing to flatten the wound body 20 and heat pressing to cure each sheet-like member 250 and bond (glue, etc.) the sheet-like members 250 together are performed simultaneously. The details are as follows.

As shown in FIG. 6, two sheet-like members 250 having a thermoplastic resin layer (adhesive layer) 252 on the first surface S1 side of both end portions 251 are arranged so that the first surfaces S1 face each other and the rolled body 20 is located between them.

7, a pair of first press plates P1 sandwich the portions 253 of the two sheet-like members 250 that cover the wound body 20 and heat press them. In this embodiment, the heat press is performed for 5 seconds at a temperature of 220° C. and a pressure of 2 MPa. As a result, the wound body 20 is pressed until it is sufficiently flattened and the hollow portion 20a is sufficiently crushed, and the portions of the two sheet-like members 250 to which heat is applied by the first press plate P1 are hardened (thermosetting), forming the shape-retaining body 25A. In FIG. 7, the first press plate P1 is in contact only with the flattened portions of the wound body 20, but the first press plate P1 may be in contact with the entire portion of the sheet-like member 250 that corresponds to the shape-retaining body 25A (i.e., the curved portion as well). The first press plate P1 may be pressed until the hollow portion 20a disappears, or may be pressed to the extent that only a small amount remains.

At the same time as the heat pressing by the pair of first press plates P1, a pair of second press plates P2 sandwiches and heat presses one end 251 of the two sheet-like members 250, which have the adhesive layers 252 facing each other, and a pair of third press plates P3 sandwiches and heat presses the other end 251 of the two sheet-like members 250, which have the adhesive layers 252 facing each other. As a result, the opposing one end 251 hardens (thermally hardens) and the adhesive layers 252 adhere to each other. The opposing other end 251 hardens (thermally hardens) and the adhesive layers 252 adhere to each other (see FIG. 7). At this time, the adhesive layers 252 arranged on each of the opposing end portions 251 are bonded together by the heat press, i.e., they form one adhesive layer 252.

After the heat pressing with each of these press plates P1, P2, and P3, the shape-retaining portion 25 is cooled sufficiently, completing the electrode body 2 with the shape-retaining portion 25 around the wound body 20.

According to the electrode body 2 described above, even before the electrode body 2 is placed in the case 3, the shape-retaining portion 25 suppresses deformation of the wound body 20 (in the case of this embodiment, for example, deformation in which the flat wound body returns to the state before pressing, i.e., deformation in which the hollow portion 20a expands in the Y-axis direction), thereby suppressing the occurrence of gaps between the electrodes 21 and 22 due to deformation of the wound body 20.

In addition, because the shape of the wound body 20 (electrode body 2) is maintained by the shape retention portion 25, the occurrence of gaps between the electrodes 21, 22 due to deformation of the wound body 20 during the manufacture of the energy storage element 1, etc., is suppressed, and thus an increase in resistance caused by the occurrence of gaps between the electrodes 21, 22 in the electrode body 2 is suppressed. As a result, the performance degradation of the energy storage element 1 including the electrode body 2 is suppressed.

The electrode body of the present invention and the energy storage element including the electrode body are not limited to the above-mentioned embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the configuration of one embodiment can be added to the configuration of another embodiment, and part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Furthermore, part of the configuration of one embodiment can be deleted.

The specific configuration of the shape-retaining section 25 is not limited. For example, the shape-retaining section 25 in the above embodiment has two sheet-like members 250, but may have one sheet-like member 250 or may have three or more sheet-like members 250. When the shape-retaining section 25 has one sheet-like member 250, both ends of the sheet-like member 250 are joined to each other with their first surfaces S1 facing each other to form the joint section 25B, and when the shape-retaining section 25 has three or more sheet-like members 250, the ends 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 their first surfaces S1 facing each other to form the joint section 25B.

In addition, 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 another portion of the curved portion 20R, or from a flat portion of the wound body 20 (the portion where the electrodes 21, 22 and the separator 23 are stacked in a flat state: the portion between the two curved portions 20R in the wound body 20).

When the joint 25B protrudes from another part (other than the apex) of the curved part 20R, it may be located between the curved part (part with a curved outer circumferential surface) 20R of the wound body 20 and the corner of the case 3 facing the curved part 20R, for example, as shown in FIG. 8. In this way, the joint 25B (a pair of ends 251) is located using the gap (space) that occurs between the curved part 20R and the corner of the case 3 in the case 3, thereby suppressing the decrease in energy density in the case 3. That is, regardless of whether the joint 25B is located or not, the joint 25B is located between the curved part 20R and the corner of the case 3 where the gap is formed, thereby suppressing the occurrence of a decrease in energy density (more specifically, a decrease in energy density by the area (volume) occupied by the joint 25B in the case 3) that occurs when the joint 25B is located in another position.

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

The joint 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, the pair of ends 251 may sandwich the separator 23 so that a part of the separator 23 protrudes (is exposed) outward from the edge of the joint 25B. As shown in FIG. 10, at least one of the pair of ends 251 constituting the joint 25B may have a hole (through hole) 251a penetrating in the thickness direction of the end 251, and a part of the separator 23 (i.e., a part of the part of the separator 23 sandwiched between the pair of ends 251) may be exposed to the outside through the through hole 251a.

In the electrode body 2 of the above embodiment, the shape-retaining portion 25 made of resin covers the separator 23 at the outermost periphery of the wound body 20, so even if the electrode body 2 is housed in the case 3 together with the electrolyte, the contact area of the separator 23 with the electrolyte is small. However, if a portion of the separator 23 is exposed to the outside of the electrode body 2 as described above, the electrode body 2 is housed in the case 3 together with the electrolyte, and the electrolyte is sufficiently supplied to the inside of the wound body 20 (the winding center side) through the exposed portion of the separator 23.

The adhesive layer 252 of the pair of ends 251 that constitute the joint 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. The adhesive layer 252 may also be made of a reactive adhesive, a pressure-sensitive adhesive, etc.

The material constituting the sheet-like member 250 constituting the shape retention section 25 is not limited to thermosetting resin. For example, the sheet-like member 250 may be made of a photocurable resin.

In addition, 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 adhesive or the like, but this configuration is not limited thereto. The shape-retaining portion main body 25A may be joined to the outer peripheral surface of the wound body 20 by adhesive or the like.

In the above embodiment, the storage element is described as being used as a chargeable and dischargeable non-aqueous electrolyte secondary battery (e.g., a lithium ion secondary battery), but the type and size (capacity) of the storage element are arbitrary. In the above embodiment, a lithium ion secondary battery is described as an example of a storage element, but the present invention is not limited to this. For example, the present invention can be applied to storage elements of various secondary batteries, as well as other primary batteries and capacitors such as electric double layer capacitors.

The energy storage element (e.g., a battery) 1 may be used in an energy storage device 11 (a battery module when the energy storage element is a battery) as shown in FIG. 11. The energy storage device 11 has at least two energy storage elements 1 and a bus bar member 12 that electrically connects the two (different) energy storage elements 1 to each other. In this case, the technology of the present invention may be applied to at least one energy storage element 1.

1...electric 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 ends), 250...sheet-like member, 251...end portion, 251a...through hole (hole), 252...adhesive layer, 3...Case, 31...Case body, 311...Closure, 312...Body, 313...Long wall, 314...Short wall, 32...Cover plate, 34...Opening periphery, 4...External terminal, 5...Current collector, 50...Clip member, 51...First connection, 52...Second connection, 53...Bent portion, 6...Insulating member, 11...Electric storage device, 12...Busbar member, C...Winding shaft, P1...First press plate, P2...Second press plate, P3...Third press plate, S1...First surface, S2...Second surface

Claims (5)

An electrode assembly housed in a case together with an electrolyte,
a wound body having a wound sheet-like electrode;
a shape retaining section having at least one sheet-like member that is harder than the electrode and therefore less likely to deform, and that retains the shape of the wound body;
the at least one sheet-like member has a first surface and a second surface that is a reverse surface of the first surface, is disposed along an 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 ends of the electrodes in the winding direction to each other,
An electrode body, wherein the pair of joined ends have the first surfaces facing each other. The wound body has a separator wound in a state overlapping the electrode,
The electrode assembly according to claim 1 , wherein the pair of end portions sandwich the separator in a state where a portion of the separator is exposed to the outside. At least one of the pair of ends has a hole penetrating in a thickness direction,
The electrode assembly according to claim 2 , wherein a portion of the separator is exposed to the outside through the hole. An electrode assembly according to any one of claims 1 to 3,
and a case that houses the electrode body together with an electrolyte. the case has a rectangular parallelepiped or cubic shape having a size corresponding to the electrode body, and accommodates the electrode body such that a winding axis of the electrode body is aligned with a direction in which a pair of opposing wall portions of the rectangular parallelepiped or cubic shape face each other;
The storage element according to claim 4 , wherein the pair of ends of the shape-retaining portion of the electrode body are located between a curved portion in which the outer circumferential surface of the wound body is curved and a corner of the case opposite the curved portion.