JP6970912B2 - A power storage element and a power storage device including a power storage element - Google Patents

Description

The present invention relates to a power storage element including an electrode body in which a first electrode and a second electrode are overlapped with each other via a separator, and a power storage device including the power storage element.

Conventionally, as shown in FIG. 19, a square lithium secondary battery 500 in which a plurality of electrode plates 504 in which a positive electrode plate 501 and a negative electrode plate 502 are laminated via a separator 503 is housed in a battery case 505 has been known. (See Patent Document 1). In this square lithium secondary battery 500, the positive electrode plate 501, the negative electrode plate 502, and the separator 503 have a rectangular shape having the same size. Further, the selvage portions 501a of the positive electrode plate 501 are assembled, connected to the lead terminal 506, and connected to the positive electrode terminal 507. Similarly, in the negative electrode plate 502, the respective selvage portions 502a are assembled, connected to the lead terminal 508, and connected to the battery case 505 that also serves as the negative electrode terminal.

In this square lithium secondary battery 500, the positive electrode plate 501, the negative electrode plate 502, and the separator 503 are all the same size, so that the separator 503 shrinks due to heat or the like, or the positive electrode plate 501 shifts due to vibration or the like. , The positive electrode plate 501 is likely to come into contact with the negative electrode plate 502 and cause a short circuit.

Therefore, in order to prevent the short circuit, as shown in FIGS. 20 and 21, in the electrode laminated body 604 in which the flat plate-shaped positive electrode 601 and the negative electrode 602 and the separator 603 are laminated, the separator 603 is attached to the positive electrode 601 and the negative electrode 602. It is conceivable to prevent a short circuit due to the displacement by increasing the size and configuring the electrode laminate 604 so that the peripheral edge portion of the separator 603 is located outside the peripheral edges of the positive electrode 601 and the negative electrode 602 over the entire circumference (Patent Document). 2).

However, when the peripheral edge portion of the separator 603 is located outside the peripheral edges of the positive electrode 601 and the negative electrode 602 over the entire circumference, the volume of the electrode laminated body 604 increases (specifically, the portion that does not contribute to charge / discharge in the electrode laminated body 604). The volume increase) increases, and the energy density in the electrode laminated battery provided with the electrode laminated body 604 decreases.

Japanese Unexamined Patent Publication No. 04-167375 Japanese Unexamined Patent Publication No. 2012-209072

Therefore, in the present embodiment, a power storage element capable of suppressing contact between the first electrode and the second electrode when the separator contracts while suppressing an increase in the volume of the entire electrode body, and a power storage device including the power storage element. The purpose is to provide.

The power storage element of this embodiment is
It has a first electrode, a separator, and a second electrode having a polarity different from that of the first electrode, and includes an electrode body in which the first electrode and the second electrode overlap each other via the separator.
The first electrode has a first electrode body and a first extension piece extending from the peripheral edge of the first electrode body.
The second electrode has a second electrode body and a second extension piece extending from the peripheral edge of the second electrode body.
Each edge of the separator in the first direction in which the first extension piece extends is outside the corresponding edge of the first electrode body in the first direction.
The first extension piece extends to a position where the portion including the tip thereof protrudes from the edge of the separator.
The dimension of the separator in the first direction is larger than the dimension of the second electrode body in the first direction.
The second edge of the separator in the first direction opposite to the first edge on the side where the first extension piece protrudes is the corresponding edge of the second electrode body. Is in the same position as.

According to such a configuration, since the dimension of the separator in the first direction is larger than the dimension of the first direction of the second electrode body, the second end edge is made the same as the corresponding end edge of the second electrode body. One end edge (the end edge on the protruding side of the first extending piece) can be projected from the corresponding end edge of the second electrode body toward the protruding direction side of the first extending piece, whereby when the separator contracts. The contact between the first extending portion (first electrode) and the second electrode body (second electrode) can be suppressed. Moreover, since the second edge of the separator is at the same position as the corresponding edge of the second electrode body, the peripheral edge of the separator is located outside the peripheral edge of the second electrode body over the entire circumference. Volume increase is suppressed.

In the power storage element,
The electrode body includes the first wall portion and the second wall portion facing the first wall portion at a distance, and accommodates the electrode body between the first wall portion and the second wall portion. Equipped with a case
The first end edge of the separator may be in direct or indirect contact with the first wall, and the second edge of the separator may be in direct or indirect contact with the second wall.

According to such a configuration, since the first end edge and the second end edge of the separator are in direct or indirect contact with the facing wall portions (first wall portion and second wall portion) in the case, the first one. Even if the case vibrates in the direction opposite to the first wall portion and the second wall portion, the separator is unlikely to be displaced. As a result, the contact between the extension piece and the second electrode can be more reliably suppressed.

In this case, in the power storage element,
The inner surface of the first wall portion facing the inside of the case may include a recess provided at a position corresponding to the first extension piece.

According to this configuration, the first extension piece is arranged in the recess, so that the separator is damaged by the first extension portion sandwiched between the first wall portion and the first end edge of the separator. It can be suppressed. That is, when the first wall portion of the separator is not provided with a recess, when the first end edge of the separator abuts on the first wall portion of the case, the first extending portion becomes the first wall portion and the first end edge. The edge (edge corner portion) of the first extension piece comes into contact with the separator by being sandwiched between the two, and by providing the recess and arranging the first extension piece in the recess, the said The contact of the edge of the first extension piece with the separator can be suppressed, and damage to the separator due to this contact can be suppressed.

In the power storage element,
The second electrode body is folded so that one side of the second direction orthogonal to the first direction is opened and the first folded portion is folded so that the other side of the second direction is opened. It is a zigzag state in which the second folded part is alternately arranged.
The first electrode is provided on the inside of the first folded portion and the inside of the second folded portion so that the extending direction of the first extending piece is along the extending direction of the turn axis of each folded portion. Placed in
The separator arranged between the first electrode and the second electrode in each folded portion of the first folded portion and the second folded portion is a biaxially stretched separator. May be good.

Inside each folded portion, the separator tends to shrink in the direction in which the turn axis extends (first direction: see, for example, FIG. 8) (it shrinks significantly compared to the second direction), but the first edge of the separator (first extension). Since the protruding end edge of the protruding piece) protrudes from the corresponding edge of the second electrode body to the protruding side of the first extending piece in the first direction, the separator contracts significantly in the extending direction of the turn axis. Even so, the contact of the first extension piece with the second electrode body is more reliably suppressed. That is, inside each folded portion of the second electrode body in the zigzag state, a portion close to both ends of the separator in the second direction (that is, a portion that is turned around the turn axis) of each folded portion. , And the vicinity of the portion where the turn portions are adjacent to each other: for example, the region α in FIG. It becomes remarkable (larger) than the shrinkage amount of the separator in the direction. Therefore, in such a configuration, the separator is formed on the turn axis by projecting the first end edge of the separator (the end edge on the protruding side of the first extension piece) to the outside of the corresponding end edge of the second electrode body. It prevents the first extension piece from coming into contact with the second electrode body when it is greatly contracted in the extending direction.

Further, in the power storage element,
A case for accommodating the electrode body is provided.
The separator is a biaxially stretched separator.
The case accommodates the electrode body in a state where at least a predetermined region of the electrode body is pressed from both sides in the direction in which the first electrode and the second electrode overlap.
The predetermined region may be a region of the electrode body that is orthogonal to the first direction and corresponds to both ends of the first electrode body in a direction along the first electrode.

According to such a configuration, inside each folded portion of the second electrode body, the region corresponding to both ends of the first electrode body in the second direction is compressed, whereby both ends of the separator in the second direction are squeezed. Since the separator is firmly sandwiched between the two-electrode body and the first electrode body, the separator tends to shrink in the direction in which the turn axis of the folded portion extends (first direction) rather than in the second direction (it shrinks significantly compared to the second direction). Since the first end edge of the separator (the end edge on the protruding side of the first extension piece) protrudes outward from the corresponding end edge of the second electrode body, even if the separator contracts significantly in the first direction, The contact of the first extension piece with the second electrode body is surely suppressed.

Further, the power storage device of another embodiment is
A plurality of energy storage elements according to any one of the above, wherein the first electrode and the second electrode are arranged in a direction in which the first electrode and the second electrode overlap each other.
A holding member for holding the plurality of power storage elements, and
Each of the plurality of power storage elements has a case for accommodating the electrode body.
Each separator of the plurality of power storage elements is a biaxially stretched separator.
The holding member is the plurality of power storage elements so that at least a predetermined region of the electrode body is pressed from both sides in the direction in which the first electrode and the second electrode overlap each other through the case in each power storage element. Hold,
The predetermined region is a region of the electrode body that is orthogonal to the first direction and corresponds to both ends of the first electrode body in a direction along the first electrode.

According to such a configuration, inside each folded portion of each second electrode of the plurality of power storage elements, a predetermined region of the electrode body (a direction orthogonal to the first direction and along the first electrode body (second direction). ), Since the area corresponding to both ends of the first electrode body is compressed, the separator tends to shrink in the extending direction (first direction) of the turn axis of the folded portion (largely shrinks compared to the second direction). Since the first end edge of the separator (the end edge on the protruding side of the first extension piece) protrudes outward from the corresponding end edge of the second electrode body in the electrode body of each storage element, the separator is the first. Even if it contracts significantly in the direction, the contact of the first extension piece with the second electrode body is surely suppressed. Moreover, in each power storage element, since the second edge of the separator is at the same position as the corresponding edge of the second electrode body, the peripheral edge of the separator is located outside the peripheral edge of the second electrode body over the entire circumference. The volume increase is suppressed as compared with the case where the volume is increased.

Based on the above, according to the present embodiment, the power storage element capable of suppressing the contact between the first electrode and the second electrode when the separator contracts while suppressing the volume increase of the entire electrode body, and the power storage element. A power storage device can be provided.

FIG. 1 is a perspective view of a power storage element according to the present embodiment. FIG. 2 is an exploded perspective view of the power storage element. FIG. 3 is a cross-sectional view taken along the line III-III of FIG. FIG. 4 is a cross-sectional view of the IV-IV position of FIG. FIG. 5 is a perspective view for explaining the electrode body. FIG. 6 is a schematic cross-sectional view at the VI-VI position of FIG. FIG. 7 is a diagram for explaining the configuration of the negative electrode. FIG. 8 is a perspective view for explaining the configuration of the negative electrode in the zigzag state. FIG. 9 is a perspective view for explaining the folded-back portion. FIG. 10 is a diagram for explaining the configuration of a sheet-fed member including a positive electrode and a separator. FIG. 11 is a diagram for explaining the configuration of a sheet-fed member including a positive electrode and a separator. FIG. 12 is a diagram for explaining the positional relationship between the positive electrode, the negative electrode, and the separator in the electrode body. FIG. 13 is a cross-sectional view taken along the longitudinal direction of the lid plate. FIG. 14 is a schematic diagram for explaining a region that is easily pressed in the electrode body. FIG. 15 is a schematic diagram for explaining the configuration of the electrode body of another embodiment. FIG. 16 is a schematic view showing the configuration of the electrode body of another embodiment. FIG. 17 is a perspective view of a power storage device including the power storage element. FIG. 18 is an exploded perspective view of the power storage device. FIG. 19 is a partial cross-sectional view for explaining the configuration of the electrode plate group of the conventional square lithium secondary battery. FIG. 20 is an exploded perspective view showing the configuration of a conventional electrode laminate. FIG. 21 is a perspective view of the electrode laminate.

Hereinafter, an embodiment of the power storage element according to the present invention will be described with reference to FIGS. 1 to 14. The power storage element includes a primary battery, a secondary battery, a capacitor and the like. In this embodiment, a rechargeable secondary battery will be described as an example of the power storage element. The names of the constituent members (each constituent element) of the present embodiment are those in the present embodiment, and may be different from the names of the respective constituent members (each constituent element) in the background art.

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 movement of lithium ions. This type of power storage element supplies electrical energy. The power storage element may be used alone or in a plurality. Specifically, the power storage element is used alone 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 used in the power storage device in combination with another power storage element. In the power storage device, the power storage element used in the power storage device supplies electric energy.

As shown in FIGS. 1 to 4, the power storage element includes an electrode body 2. Further, the power storage element 1 is a current collector that connects the case 3 that houses the electrode body 2, the external terminal 4 that is attached to the case 3 with at least a part exposed to the outside, and the electrode body 2 and the external terminal 4. It is equipped with a body 5. Further, the power storage element 1 also includes an insulating member 6 or the like arranged between the electrode body 2 and the case 3. In each figure, in order to show the structure, the structure of the electrode body 2 is schematically shown, for example, the thickness of the electrodes and the like constituting the electrode body 2 is exaggerated.

As shown in FIGS. 5 and 6, the electrode body 2 has a first electrode 22, a separator 25, and a second electrode 21 having a polarity different from that of the first electrode 22. In the electrode body 2, the first electrode 22 and the second electrode 21 overlap each other via the separator 25. The electrode body 2 of the present embodiment has a sheet-fed member 26 having a first electrode 22 and a separator 25 sandwiching the first electrode 22, and the thickness of the sheet-fed member 26 having a polarity different from that of the first electrode 22. It has a second electrode 21 that sandwiches the single-wafer-shaped member 26 in the radial direction. In the electrode body 2, the first electrode 22 is a positive electrode and the second electrode 21 is a negative electrode.

As shown in FIG. 7, the negative electrode 21 has a metal foil 211 and a negative electrode active material layer 212 laminated on both sides of the metal foil 211. That is, the negative electrode 21 has one metal foil 211 and a pair of negative electrode active material layers 212. The metal foil 211 of the present embodiment is, for example, a copper foil. As shown in FIG. 8, the negative electrode 21 has a long strip shape and has a folded portion 23.

The negative electrode active material layer 212 has a negative electrode active material and a binder.

The negative electrode active material is, for example, a carbon material such as graphite, non-graphitized carbon, and easily graphitized carbon, or a material that undergoes an alloying reaction with lithium ions such as silicon (Si) and tin (Sn). The negative electrode active material of this embodiment is graphite.

The binder used for the negative electrode active material layer 212 is, for example, polyvinylidene fluoride (PVDF), a copolymer of ethylene and vinyl alcohol, methyl polymethacrylate, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid. Acid, styrene-butadiene rubber (SBR). The binder of this embodiment is polyvinylidene fluoride.

The negative electrode active material layer 212 may further have a conductive auxiliary agent such as Ketjen Black (registered trademark), acetylene black, and graphite. The negative electrode active material layer 212 of the present embodiment does not have a conductive auxiliary agent.

As shown in FIG. 9, the folded portion 23 is a first surface 231 which is a surface on the valley fold side and a second surface which is a surface on the mountain fold side (that is, a surface opposite to the first surface 231). It includes a pair of flat portions 233 each having 232 and having the first surfaces 231 facing each other, and a turn portion 234 connecting the ends of the pair of flat portions 233 to each other. The negative electrode 21 of the present embodiment is in a continuous zigzag state (bellows shape) in a state in which the adjacent folded portions 23 have a part (flat portion 233) in common with the turned portions 234 facing in the opposite direction.

In other words, the negative electrode 21 has a folded-back portion (first folded-back portion) 23A folded so that one side in a predetermined direction (left-right direction in FIG. 8) is opened, and the other side in the predetermined direction is opened. It is in a zigzag state in which the folded-back portions (second folded-back portions) 23B are alternately arranged. Then, when focusing on one folded portion (first folded portion) 23A, the first folded portion 23A and the folded portion (second folded portion) 23B next to it (on the rear side in FIG. 8) are first. The flat portions 233A and 233B between the turn portion 234A of the folded portion 23A and the turn portion 234B of the second folded portion 23B are shared.

In this case, as shown in FIG. 8, in the flat portion 233A when focusing on the first folded portion 23A, the surface of the first folded portion 23A on the valley folding surface side is the first surface 231A, and the surface on the opposite side thereof. The surface (the surface on the mountain fold side) is the second surface 232A. On the other hand, in the flat portion 233B (flat portion 233B shared with the flat portion 233A of the first folded portion 23A) when focusing on the second folded portion 23B, the surface of the second folded portion 23B on the valley folding surface side is the first. The surface 231B on the opposite side (the surface on the mountain fold side) is the second surface 232B. That is, in the flat portions 233A and 233B that are common to the first folded portion 23A and the second folded portion 23B, the first folded portion 23A and the second folded portion 23B are focused on. The first surface (the surface facing each other in the folded portion 23) 231 and the second surface (the surface facing in the opposite direction in the folded portion 23) 232 are opposite to each other.

Returning to FIGS. 2 to 9, specifically, in the negative electrode 21, the flat portion 233 and the turn portion 234 are alternately formed by alternately folding the strip-shaped negative electrode 21 in the long direction at predetermined intervals. There is. That is, the long negative electrode 21 alternately repeats mountain folds and valley folds at the positions of the mountain fold lines 21A and the valley fold lines 21B which are alternately set at predetermined intervals in the longitudinal direction shown in FIG. As a result, it becomes a zigzag fold state. As a result, the negative electrode 21 has a plurality of flat portions 233 and a plurality of turn portions 234, each of the plurality of flat portions 233 is arranged in parallel or substantially parallel, and each of the plurality of turn portions 234 is adjacent to each other. The ends of the flat portion 233 on one end side in the long direction and the ends on the other end side are alternately connected to each other.

In the following, the direction in which the flat portions 233 are arranged is defined as the X-axis direction in the Cartesian coordinate system, and the direction in which the turn portion 234 is arranged with respect to the flat portion 233 (the left-right direction in FIG. 8) is defined as the Y-axis direction in the Cartesian coordinate system. The direction in which the turn axis S of the turn portion 234 extends (see FIG. 8) is defined as the Z-axis direction in the Cartesian coordinate system.

Each of the plurality of flat portions 233 protrudes from one side constituting the rectangular flat portion main body 2331 and the rectangular contour of the flat portion main body 2331 (in the example of the present embodiment, Z from the end edge in the Z-axis direction). It has a negative electrode tab (second extension piece) 2332, which extends in the axial direction. The flat portion main body 2331 of the present embodiment has a rectangular shape long in the Y-axis direction. In the flat portion main body 2331, the entire surface of both surfaces of the metal foil 211 is covered with the negative electrode active material layer 212, and in the negative electrode tab 2332, the metal foil 211 is exposed. That is, the negative electrode tab 2332 does not have the negative electrode active material layer 212. In the negative electrode 21 of the present embodiment, the flat portion main body 2331 and the turn portion 234 are alternately connected to form a negative electrode main body (second electrode main body).

In the negative electrode 21 in the zigzag state, the negative electrode tabs 2332 of the flat portions 233 overlap each other when viewed from the X-axis direction. In the negative electrode 21 of the present embodiment, each negative electrode tab 2332 is Z from one end in the Y-axis direction (right side in FIG. 8) at one end in the Z-axis direction (upper side in FIG. 8) of the flat portion main body 2331. It extends in the axial direction. The negative electrode tabs 2332 extending from each of the plurality of flat portion main bodies 2331 are bundled and connected to the external terminal 4 via the current collector 5 (see FIG. 3). The bundle of the negative electrode tabs 2332 of the present embodiment is connected to the current collector 5 by welding. The bundle of the negative electrode tabs 2332 may be connected to the current collector 5 by crimping.

In each of the plurality of turn portions 234, in the negative electrode 21 in the zigzag state, the band-shaped negative electrode 21 is swiveled with the axis extending in the Z-axis direction as the turn axis S (see FIG. 8) (in other words, around the turn axis S). It is a part (turning direction). Also in this turn portion 234, both sides of the metal foil 211 are covered with the negative electrode active material layer 212.

As shown in FIGS. 5, 6, 10, and 11, the positive electrode 22 has a metal foil 221 and a positive electrode active material layer 222 laminated on both sides of the metal foil 221. That is, the positive electrode 22 has one metal foil 221 and a pair of positive electrode active material layers 222. The metal foil 221 of the present embodiment is, for example, an aluminum foil. The positive electrode 22 is arranged between the flat portions 233 adjacent to each other in the X-axis direction in the negative electrode 21 in the zigzag state. Therefore, the electrode body 2 of the present embodiment has a plurality of positive electrodes 22.

The positive electrode active material layer 222 has a positive electrode active material and a binder.

The positive electrode active material of this embodiment is, for example, a lithium metal oxide. Specifically, the positive electrode active material is, for example, a composite oxide represented by LiaMebOc (Me represents one or more transition metals) (LiaCoyO ₂ , LiaNixO ₂ , LiaMnzO ₄ , LiaMnzO _{4, LiaNixCoyMnzO 2,} etc.), LiaMeb ( XOc) d (Me represents one or more transition metals, X represents, for example, P, Si, B, V) polyanionic compounds (LiaFebPO ₄ , LiaMnbPO ₄ , LiaMnbSiO ₄ , LiaMnbSiO ₄ , LiaCobPO 4 F, etc.) ). The positive electrode active material of this embodiment is LiNi _1/3 Co _1/3 Mn _1/3 O ₂ .

The binder used for the positive electrode active material layer 222 is the same as the binder used for the negative electrode active material layer 212. The binder of this embodiment is polyvinylidene fluoride.

The positive electrode active material layer 222 may further have a conductive auxiliary agent such as Ketjen Black (registered trademark), acetylene black, and graphite. The positive electrode active material layer 222 of the present embodiment has acetylene black as a conductive auxiliary agent.

Specifically, each of the plurality of positive electrodes 22 has a positive electrode main body (first electrode main body) 223 and a positive electrode tab (first extension piece) 224 extending from the peripheral edge of the positive electrode main body 223. Specifically, each of the plurality of positive electrodes 22 protrudes from one side forming the rectangular contour of the positive electrode body (first electrode body) 223 and the rectangular contour of the positive electrode body 223 (in the example of the present embodiment, the Z axis). It has a positive electrode tab 224, which extends in the Z-axis direction from the edge in the direction. The positive electrode body 223 of the present embodiment has a rectangular shape long in the Y-axis direction. In the positive electrode main body 223, the entire surface of both surfaces of the metal foil 221 is covered with the positive electrode active material layer 222, and in the positive electrode tab 224, the metal foil 221 is exposed. That is, the positive electrode tab 224 does not have the positive electrode active material layer 222. An insulating layer containing an insulator such as inorganic particles may be formed at the base of the positive electrode tab 224 (a region adjacent to the positive electrode active material layer 222).

The positive electrode active material layer 222 in the positive electrode body 223 faces the YZ plane (Y-axis and Z-axis) from the negative electrode active material layer 212 of the flat portion 233 facing in the X-axis direction (specifically, facing through the separator 25). Small in the direction (including the plane). That is, the positive electrode active material layer 222 of the positive electrode main body 223 faces the negative electrode active material layer 212 of the flat portion 233 in the entire area, and the negative electrode active material layer 212 of the flat portion 233 is the positive electrode main body 223 in the region excluding the peripheral portion. It faces the positive electrode active material layer 222.

In the electrode body 2, the positive electrode tabs 224 of each positive electrode 22 overlap each other when viewed from the X-axis direction. In the positive electrode 22 of the present embodiment, each positive electrode tab 224 is the position of the negative electrode tab 2332 with respect to the flat portion main body 2331 at the other end in the Z-axis direction (upper side in FIG. 5) of the positive electrode main body 223 in the Y-axis direction. Opposite side: extends in the Z-axis direction from the end (left side in FIG. 5). The positive electrode tabs 224 extending from each of the plurality of positive electrode main bodies 223 are bundled and connected to the external terminal 4 via the current collector 5. The bundle of the positive electrode tab 224 of the present embodiment is connected to the current collector 5 by welding, similarly to the bundle of the negative electrode tab 2332 (see FIG. 3). The bundle of the positive electrode tabs 224 may be connected to the current collector 5 by crimping.

The separator 25 is an insulating member and is arranged between the negative electrode 21 and the positive electrode 22. As a result, in the electrode body 2, the negative electrode 21 and the positive electrode 22 are insulated from each other. Further, the separator 25 holds the electrolytic solution in the case 3. As a result, when the power storage element 1 is charged and discharged, lithium ions can move between the negative electrode 21 and the positive electrode 22 that face each other across the separator 25.

The separator 25 is strip-shaped and is composed of, for example, a porous membrane such as polyethylene, polypropylene, cellulose, or polyamide. In the separator 25 of the present embodiment _{, an inorganic layer containing inorganic particles such as SiO 2} particles, Al ₂ O ₃ particles, and boehmite (alumina hydrate) is provided on a base material formed of a porous film. Is formed of. The base material of the separator 25 of the present embodiment is formed of, for example, polyethylene.

The separator 25 of the present embodiment is biaxially stretched. That is, the separator 25 is a biaxially stretched film. The biaxially stretched separator 25 usually has a porous structure oriented in multiple directions. That is, the longitudinal directions of the holes formed in the biaxially stretched separator 25 are usually not aligned in one direction. The separator 25 sandwiches the positive electrode 22. Specifically, the separator 25 covers the entire positive electrode body 223 so as to sandwich it in the X-axis direction. As shown in FIGS. 10 and 11, the separator 25 is formed by folding a rectangular shape at the central portion in the long direction so as to sandwich the positive electrode 22 between them, and the three sides (each end) excluding the crease portion. The edges) are joined (adhesive, welded, etc.). With the separator 25 sandwiching the positive electrode 22, each end edge 251, 252 of the separator 25 in the Z-axis direction is outside the corresponding end edge of the positive electrode body 223. The peripheral edge of the separator 25 of the present embodiment is outside the peripheral edge of the positive electrode body 223 (see FIG. 12). In this state, the positive electrode tab 224 extends to a position where the portion including the tip thereof protrudes from the edge of the separator 25 (see FIG. 12).

The separator 25 in a state of sandwiching the positive electrode 22 has a rectangular shape when viewed from the X-axis direction, and the dimension in the Z-axis direction is larger than the dimension in the Z-axis direction of the flat portion main body 2331 (negative electrode main body) of the negative electrode 21. Further, the dimension of the separator 25 in the Y-axis direction is larger than the dimension of the flat portion main body 2331 in the Y-axis direction, but is a size that does not protrude from the inside of the folded portion 23. In the electrode body 2 of the present embodiment, the positive electrode 22 and the separator 25 in a state of sandwiching the positive electrode 22 constitute the single-wafer-shaped member 26.

In the following, the end edge of the separator 25 (single-leaf member 26) on the side where the positive electrode tab 224 protrudes (one side in the Z-axis direction) is referred to as the first end edge 251 and is opposite to the first end edge (Z-axis). The edge on the other side of the direction) is referred to as the second edge 252. Further, a pair of end edges connecting the first end edge and the second end edge of the single-wafer-shaped member 26 (separator 25) is referred to as a third end edge 253.

In the electrode body 2, the first end edge 251 of the separator 25 is outside the corresponding edge (upper end of the flat portion 233 in FIG. 12) 235 (upper side in FIG. 12) of the negative electrode 21, and the second edge 252 is. , The corresponding edge of the negative electrode 21 (the lower end of the flat portion 233 in FIG. 12) 236. That is, the dimension of the separator 25 in the Z-axis direction is larger than the dimension of the flat portion 233 of the negative electrode 21 in the Z-axis direction, and the second edge of the separator 25 is at the same position as the corresponding edge of the negative electrode 21. The first end edge 251 of 25 is located (projected) outward in the Z-axis direction from the corresponding end edge of the negative electrode 21. Further, in the electrode body 2, one of the third end edges 253 of the separator 25 is in contact with the turn portion 234, and the other is the open end edge of the folded portion 23 (on the left side in the example shown in FIG. 12). It is in the same position as the edge).

Further, the first end edge 251 and the second end edge 252 of the separator 25 are in direct or indirect contact with the inner surface of the case 3. The first end edge 251 and the second end edge 252 of the present embodiment are in contact with the inner surface of the case 3 via the insulating member 6 (that is, indirectly) (see FIG. 4).

Returning to FIGS. 1 to 4, the case 3 includes a lid plate (first wall portion) 32 and a closed portion (second wall portion) 311 facing the lid plate 32 at intervals, and the lid plate 32. The electrode body 2 is accommodated between the closure portion 311 and the closure portion 311. Specifically, the case 3 has a case main body 31 having an opening and a lid plate 32 that closes (closes) the opening of the case main body 31. In this case 3, the internal space is defined by the case body 31 and the lid plate 32. The case 3 houses the electrolytic solution together with the electrode body 2 in this internal space.

This electrolytic solution is a non-aqueous electrolyte solution. This 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 ethylmethyl carbonate. Electrolyte salts are LiClO ₄ , LiBF _{4 , LiPF 6} , and the like. _{The electrolytic solution of the present embodiment contains 1 mol / L LiPF 6} in a mixed solvent prepared by adjusting ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a ratio of ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 3: 2: 5. Is dissolved.

Case 3 is formed of a metal having resistance to the above electrolytic solution. Case 3 of the present embodiment is formed of, for example, aluminum or an aluminum-based metal material such as an aluminum alloy.

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

The closing portion 311 is located at the lower end of the case main body 31 when the case main body 31 is arranged in a posture with the opening facing upward (that is, with the bottom wall portion of the case main body 31 when the opening faces upward). It is a part. The closed portion 311 of the present embodiment has a rectangular shape.

The body portion 312 has a square tube shape, more specifically, a flat square tube shape. The body portion 312 has a pair of long wall portions 313 extending from the long side at the peripheral edge of the closed portion 311 and a pair of short wall portions 314 extending from the short side at the peripheral edge of the closed portion 311. A square tubular body portion 312 is formed by connecting the end portions of the short wall portion 314 corresponding to each other (specifically, facing each other in the X-axis direction) of the pair of long wall portions 313.

As described above, the case body 31 has a square tube shape (that is, a bottomed square tube shape) in which one end in the opening direction (Z-axis direction) is closed.

The lid plate 32 is a member that closes the opening of the case body 31. As shown in FIG. 13, the inner surface 320 of the lid plate 32 facing the inside (internal space side) of the case 3 includes a first recess (recess) 321 provided at a position corresponding to the positive electrode tab 224. The inner surface 320 also includes a second recess 322 provided at a position corresponding to the negative electrode tab 2332. The contour shape of the lid plate 32 corresponds to the opening peripheral edge portion 310 (see FIG. 2) of the case body 31.

The lid plate 32 of the present embodiment is a plate-shaped member, and the plate thickness of the portion where the first recess 321 and the second recess 322 are provided is also constant or substantially constant. That is, the outer surface (the surface opposite to the inner surface 320) 325 of the lid plate 32 includes the first convex portion 326 at the position corresponding to the first concave portion 321 and the second convex portion 327 at the position corresponding to the second concave portion 322. including.

The depth of the first recess 321 and the second recess 322 is such that the bundled positive electrode tab 224 or the bundled negative electrode tab 2332 fits, that is, the bundle of the positive electrode tabs 224 connected to the external terminal 4, or the bundle of the positive electrode tabs 224 connected to the external terminal 4. The bundle of the negative electrode tabs 2332 connected to the external terminal 4 is set to a size that can be located outside (upper side in FIG. 3) of the first end edge 251 of the separator 25.

In the case 3 configured as described above, each flat portion 233 of the negative electrode 21 is parallel (substantially parallel) to the long wall portion 313 (that is, each turn portion 234 faces the short wall portion 314). The electrode body 2 covered with the insulating member 6 is housed (see FIGS. 2 to 4). At this time, the case 3 accommodates the electrode body 2 in a state where the entire electrode body 2 is pressed (pressed) in the X-axis direction. Then, the first end edge 251 of the separator 25 of the electrode body 2 abuts on the lid plate 32 (specifically, a portion of the inner surface 320 excluding the first recess 321 and the second recess 322) via the insulating member 6. The two-end edge 252 is in contact with the closing portion 311 via the insulating member 6.

The external terminal 4 is a portion electrically connected to an external terminal of another power storage element, an external device, or the like. Therefore, the external terminal 4 is formed of a conductive member. Further, the external terminal 4 is formed of a metal material having high weldability. For example, the external terminal 4 of the positive electrode is formed of an aluminum-based metal material such as aluminum or an aluminum alloy, and the external terminal 4 of the negative electrode is formed of a copper-based metal material such as copper or a copper alloy. The external terminal 4 of the present embodiment is a portion defined by the first convex portion 326 and the first concave portion 321 of the lid plate 32, or the second portion of the lid plate 32, with at least a part exposed to the outside of the case 3. It is attached to a portion defined by a protrusion 327 and a second recess 322.

The insulating member 6 is formed of an insulating resin. Specifically, as shown in FIGS. 2 to 4, the insulating member 6 is formed in a bag shape by bending a sheet-shaped member having an insulating property cut into a predetermined shape. The insulating member 6 of the present embodiment has a bag shape along the case 3, and the positions corresponding to the first recess 321 and the second recess 322 are opened.

According to the above-mentioned power storage element 1, since the dimension of the separator 25 in the Z-axis direction is larger than the dimension of the negative electrode body (flat portion body 2331) in the Z-axis direction, the second end edge 252 is used as the negative electrode body (flat portion body 2331). By making it the same as the corresponding end edge of, the first end edge (the end edge on the protruding side of the positive electrode tab 224) 251 is projected from the corresponding end edge of the negative electrode body toward the protruding direction side of the positive electrode tab 224, that is, It can be projected outward from the corresponding edge. This makes it possible to suppress contact between the positive electrode tab 224 and the negative electrode main body (flat portion main body 2331) when the separator 25 is shrunk. Moreover, since the second edge 252 of the separator 25 is at the same position as the corresponding edge of the negative electrode body, the peripheral edge of the separator 25 is located outside the peripheral edge of the negative electrode body (flat portion body 2331) over the entire circumference. The volume increase of the electrode body 2 is suppressed as compared with the case of the above. Further, when the negative electrode 21 and the positive electrode 22 sandwiched between the separators 25 are overlapped with each other, the second edge 252 of the separator 25 is made the same as the corresponding edge of the negative electrode main body (flat portion main body 2331). The negative electrode 21, the separator 25, and the positive electrode 22 can be aligned with respect to the two-end edge 252. Further, in a state where these are aligned, the first end edge of the separator 25 (the edge on the protruding side of the positive electrode tab 224) 251 is the protruding direction of the positive electrode tab 224 from the corresponding edge of the negative electrode main body (flat portion main body 2331). It can be projected to the side.

Here, "at the same position as the corresponding edge" is not limited to the exact same position, but includes a margin within a reasonable range (specifically, a manufacturing error within 1 mm, etc.). Needless to say.

In the power storage element 1 of the present embodiment, the first end edge 251 of the separator 25 indirectly abuts on the lid plate 32, and the second end edge 252 of the separator 25 indirectly abuts on the closing portion 311. As described above, since the first end edge 251 and the second end edge 252 of the separator 25 are indirectly in contact with the facing wall portions (cover plate 32 and closing portion 311) in the case 3, the storage capacity of the present embodiment is stored. In the element 1, even if the case 3 vibrates in the Z-axis direction (the direction opposite to the lid plate 32 and the closing portion 311), the separator 25 (single-leaf member 26) is unlikely to be displaced. As a result, the contact between the positive electrode tab 224 and the negative electrode main body (flat portion main body 2331) can be more reliably suppressed.

Further, in the power storage element 1 of the present embodiment, the inner surface 320 of the lid plate 32 includes a first recess 321 provided at a position corresponding to the positive electrode tab 224. Therefore, by arranging the positive electrode tab 224 in the first recess 321, the separator 25 is damaged by the positive electrode tab 224 sandwiched between the lid plate 32 and the first end edge 251 of the separator 25 (for example, the positive electrode). (The separator 25 is cut off by hitting the edge of the tab 224, etc.) can be suppressed. The details are as follows.

When the first recess 321 is not provided on the inner surface 320 of the lid plate 32, when the first end edge 251 of the separator 25 comes into contact with the lid plate 32 of the case 3, the positive electrode tab 224 is the lid plate 32 and the first end of the separator 25. It is sandwiched between the edge 251 and the edge 251. In this case, the edge (edge corner portion) of the positive electrode tab 224 comes into contact with the separator 25, but since the positive electrode tab 224 is a very thin metal foil 221, the separator 25 is easily damaged such as torn. Therefore, in the power storage element 1 of the present embodiment, the first recess 321 is provided on the inner surface 320 of the lid plate 32, and the bundle of the positive electrode tabs 224 is arranged in the first recess 321 to form the positive electrode tab 224. The contact of the edge with the separator 25 is suppressed. As a result, in the power storage element 1 of the present embodiment, damage to the separator 25 due to contact with the positive electrode tab 224 can be suppressed.

The inner surface 320 of the lid plate 32 also includes a second recess 322 provided at a position corresponding to the negative electrode tab 2332. Therefore, by arranging the negative electrode tab 2332 in the second recess 322, damage to the separator 25 by the negative electrode tab 2332 sandwiched between the lid plate 32 and the first end edge 251 of the separator 25 can be suppressed.

In the power storage element 1 of the present embodiment, the separator 25 is biaxially stretched, and the single-wafer-shaped member 26 is arranged inside each folded-back portion 23. Therefore, inside each folded portion 23 of the negative electrode 21, the separator 25 of the single-wafer-shaped member 26 tends to shrink in the Z-axis direction (direction in which the turn axis S of the folded portion 23 extends) (in the Y-axis direction) for the following reasons. Shrinks significantly compared to).

In each folded portion 23 of the negative electrode 21 in the zigzag state, the thickness dimension of the turn portion 234 and its vicinity in the X-axis direction is slightly larger than the thickness dimension of the pair of flat portions 233 in the X-axis direction. Therefore, when the electrode body 2 is housed in the case 3 and is pressed (pressed) from the case 3 (a pair of long wall portions 313) in the X-axis direction, the single-wafer-shaped member 26 is inside each folded-back portion 23. Both ends in the Y-axis direction (that is, the portion of each folded portion 23 near the turn portion 234 and the portion where the turn portion 234 is adjacent in the X-axis direction: see the region α in FIG. 14) are compressed in the X-axis direction. .. As a result, the contraction of the separator 25 in the Y-axis direction is suppressed, but the compression does not act so much on the contraction in the Z-axis direction, so that the amount of contraction increases. As a result, the shrinkage amount of the separator 25 in the extending direction (Z-axis direction) of the turn axis S of the folded portion 23 becomes remarkable (larger) than the shrinkage amount of the separator 25 in the Y-axis direction.

Therefore, in the power storage element 1 of the present embodiment, the first end edge of the separator 25 (the edge on the protruding side of the positive electrode tab 224) 251 is projected outward from the corresponding edge of the negative electrode body (flat portion body 2331). Therefore, even if the separator 25 contracts significantly in the Z-axis direction, it is possible to prevent the positive electrode tab 224 from coming into contact with the negative electrode body (see FIG. 12).

Here, the first end edge portion of the separator 25 (the portion protruding from the end edge corresponding to the first end edge 251 of the negative electrode 21) 2510 (see FIG. 12) is not sandwiched by the folded portion 23 of the negative electrode 21. Therefore, it is more likely to shrink than the second end edge portion (the portion including the second end edge 252) sandwiched between the folded portions 23 of the negative electrode 21. In particular, among the first end edge portions 2510, the portion on the side where the folded portion 23 is open (the side opposite to the turn portion 234) is more likely to shrink. However, the first end edge of the separator 25 (the end edge on the protruding side of the positive electrode tab 224) 251 is arranged sufficiently outside the corresponding end edge 235 of the negative electrode body (flat portion body 2331), so that the first end edge is arranged. Even if the portion 2510 contracts significantly, it is possible to effectively prevent the positive electrode tab 224 from coming into contact with the negative electrode body.

It should be noted that the power storage element of the present invention is not limited to the above embodiment, and it is needless to say that 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. In addition, some of the configurations of certain embodiments can be deleted.

In the power storage element 1 of the above embodiment, the electrode body 2 has a configuration having a zigzag negative electrode 21 and a single-wafer-shaped positive electrode 22, but is not limited to this configuration. For example, as shown in FIG. 15, the electrode body 2 may have a configuration in which a single-wafer-shaped negative electrode 21 and a single-wafer-shaped positive electrode 22 are laminated (so-called stack type). In this case, the separator 25 sandwiches at least one of the negative electrode 21 and the positive electrode 22. Further, as shown in FIG. 16, the electrode body 2 has a plurality of folded portions 23, each of which is composed of an independent negative electrode 21, and is inside each folded portion 23 and between adjacent folded portions 23. The structure may be such that the single-wafer-shaped member 26 is arranged.

In the power storage element 1 of the above embodiment, both ends of the sheet-fed member 26 in the Z-axis direction are in contact with the case 3 via the insulating member 6. Specifically, the first end edge 251 and the second end of the separator 25 The edge 252 is in contact with the lid plate 32 and the closing portion 311 via the insulating member 6, but the configuration is not limited to this. One end edge of the sheet-fed member 26 in the Z-axis direction (for example, the first end edge 251 of the separator 25) may not be in direct or indirect contact with the case 3.

In the power storage element 1 of the above embodiment, the separator 25 of the single-wafer-shaped member 26 is biaxially stretched, but is not limited to this configuration. The separator 25 may be uniaxially stretched. The uniaxially stretched separator 25 usually has a porous structure oriented in one direction (stretching direction). That is, the longitudinal directions of the holes formed in the uniaxially stretched separator 25 are usually aligned in one direction. The uniaxially stretched separator tends to shrink in the stretching direction, but does not easily shrink in the direction orthogonal to the stretching direction. Therefore, it is preferable that the separator 25 is arranged so that the stretching direction coincides with the Y-axis direction. Further, when the negative electrode 21 in the zigzag state is used, it is particularly preferable that the separator 25 is arranged so that the stretching direction coincides with the Y-axis direction. By using the negative electrode 21 in the zigzag state, the portion close to the turn portion 234 and the portion where the turn portion 234 is adjacent to each other in the X-axis direction are pressed in the X-axis direction. As a result, the shrinkage of the separator 25 in the Y-axis direction is suppressed, and the shrinkage in the Z-axis direction orthogonal to the stretching direction is suppressed. As a result, it is possible to prevent the positive electrode tab 224 from coming into contact with the negative electrode 21.

In the power storage element 1 of the above embodiment, the case 3 presses the entire electrode body 2 in the X-axis direction, but the case 3 is not limited to this configuration. The electrode body 2 may be pressed at least in a region corresponding to both ends of the positive electrode body 223 in the Y-axis direction (for example, a region overlapping when viewed from the X-axis direction) inside the case 3. This compression may be performed by the case 3 or by a member arranged inside the case 3.

For example, the case 3 may be embossed to form a convex portion protruding from the inner surface of the case 3 toward the electrode body 2, and the convex portion may press the electrode body 2. Further, the electrode body 2 may be compressed by increasing the thickness of the region corresponding to the portion of the insulating member 6 housed in the case 3 where the electrode body 2 is desired to be compressed. Further, the electrode body 2 may be pressed by attaching an insulating tape to the outer periphery of the electrode body 2. In this case, it is preferable to attach the insulating tape so that the outer peripheral dimension of the electrode body 2 becomes smaller after the insulating tape is attached than before the insulating tape is attached.

Further, in the above embodiment, the case where the power storage element is used as a chargeable / dischargeable non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) has been described, but the type and size (capacity) of the power storage element are arbitrary. Is. Further, in the above embodiment, the 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 can be applied to various secondary batteries, other primary batteries, and storage elements of capacitors such as electric double layer capacitors.

The power storage element (for example, a battery) 1 of the above embodiment may be used for a power storage device (battery module when the power storage element is a battery) 11 as shown in FIGS. 17 and 18, for example. The power storage device 11 has a plurality of power storage elements 1, a plurality of adjacent members 12 adjacent to the power storage element 1, a holding member 13 that collectively holds the plurality of power storage elements 1 and the plurality of adjacent members 12, and different power storage elements. A bus bar 14 for connecting the external terminals 4 of 1 to each other so as to be conductive is provided. Further, the power storage device 11 also includes an insulator 15 and the like arranged between the plurality of power storage elements 1 and the holding member 13.

The holding member 13 comprises a pair of termination members 131 that sandwich a plurality of power storage elements 1 arranged in the X-axis direction via adjacent members 12 from both sides in the X-axis direction, and a connecting member 132 that connects the pair of termination members 131. Have. In each power storage element 1, at least a predetermined region of the electrode body 2 (a region corresponding to both ends of the positive electrode body 223 in the Y-axis direction (for example, a region overlapping when viewed from the X-axis direction)) of the holding member 13 is in the X-axis direction. A plurality of power storage elements 1 are held so as to be pressed (compressed) from both sides of the case 3 via the case 3. The pressing (compression) on the electrode body 2 may be applied by holding a plurality of power storage elements 1 by the holding member 13, and the power storage element 1 may be arranged in a state where the adjacent member 12 is arranged between the power storage elements 1. And the adjacent member 12 may be added by being held together by the holding member 13.

Even with this configuration, a predetermined region of the single-wafer-shaped member 26 (a region corresponding to both ends of the positive electrode body 223 in the Y-axis direction (X-axis direction) inside each folded-back portion 23 of each negative electrode 21 of the plurality of power storage elements 1). Areas that overlap)) are squeezed. Therefore, the separator 25 of the single-wafer-shaped member 26 tends to shrink in the extending direction (Z-axis direction) of the turn axis S of the folded-back portion 23 (largely shrinks as compared with the predetermined direction). However, in the electrode body 2 of each power storage element 1, the first end edge 251 of the separator 25 is outside the corresponding edge 235 of the negative electrode 21, and the positive electrode 22 is sandwiched by the separator 25 larger than the positive electrode body 223. Even if the separator 25 contracts significantly in the extending direction of the turn axis S, contact with the negative electrode 21 of the positive electrode main body 223 and the positive electrode tab 224 is suppressed.

1 ... power storage element, 2 ... electrode body, 21 ... negative electrode (electrode), 21A ... mountain fold line, 21B ... valley fold line, 211 ... metal foil, 212 ... negative electrode active material layer, 22 ... positive electrode (electrode), 221 ... Metal foil 222 ... Positive electrode active material layer 223 ... Positive electrode body (first electrode body) 224 ... Positive electrode tab (first extension piece), 23 ... Folded part, 23A ... First folded part, 23B ... Second folded part Part, 231, 231A, 231B ... First surface, 232, 232A, 232B ... Second surface, 233, 233A, 233B ... Flat part, 2331 ... Flat part body, 2332 ... Negative electrode tab (second extension piece) , 234, 234A, 234B ... Turn portion, 235 ... Edge of the negative electrode corresponding to the first end edge of the separator, 25 ... Separator, 251 ... First end edge, 2510 ... First end edge, 252 ... Second end Edge, 253 ... Third end edge, 26 ... Sheet-fed member, 3 ... Case, 31 ... Case body, 310 ... Opening peripheral part, 311 ... Closure part, 312 ... Body part, 313 ... Long wall part, 314 ... Short wall part , 32 ... lid plate, 320 ... inner surface of the lid plate, 321 ... first concave portion, 322 ... second concave portion, 326 ... first convex portion, 327 ... second convex portion, 4 ... external terminal, 5 ... current collector, 6 ... Insulation member, 11 ... Power storage device, 12 ... Adjacent member, 13 ... Holding member, 131 ... Termination member, 132 ... Connecting member, 14 ... Bus bar, 15 ... Insulator, 500 ... Square lithium secondary battery, 501 ... Positive electrode Plate, 501a ... Positive electrode plate ear, 502 ... Negative plate, 502a ... Negative plate ear, 503 ... Separator, 504 ... Electrode plate group, 505 ... Battery case, 506 ... Lead terminal, 507 ... Positive terminal, 508 ... Lead terminal, 601 ... positive electrode, 602 ... negative electrode, 603 ... separator, 604 ... electrode laminate, S ... turn axis, α ... region in the electrode body that is easily pressed in the X-axis direction.

Claims (6)

It has a first electrode, a separator, and a second electrode having a polarity different from that of the first electrode, and includes an electrode body in which the first electrode and the second electrode overlap each other via the separator.
The first electrode has a first electrode body and a first extension piece extending from the peripheral edge of the first electrode body.
The second electrode has a second electrode body and a second extension piece extending from the peripheral edge of the second electrode body.
The second electrode body has a first folded portion folded so that one side in the second direction orthogonal to the first direction in which the first extension piece extends is opened, and the other side in the second direction is open. It is a zigzag state in which the second folded portion folded so as to be folded is alternately arranged.
The first electrode is provided on the inside of the first folded portion and the inside of the second folded portion so that the extending direction of the first extending piece is along the extending direction of the turn axis of each folded portion. Placed,
The separator, the end edges of the separator in the first direction is located outside the corresponding edges of said first electrode body in said one direction, and, the portion including a distal end at the first extension piece so as to protrude from the corresponding edge of the separator, sandwiching the entirety of the first electrode body,
The dimension of the separator in the first direction is larger than the dimension of the second electrode body in the first direction.
The second edge of the separator in the first direction opposite to the first edge on the side where the first extension piece protrudes is the corresponding edge of the second electrode body. A power storage element in the same position as. The electrode body includes the first wall portion and the second wall portion facing the first wall portion at a distance, and accommodates the electrode body between the first wall portion and the second wall portion. Equipped with a case
1 The power storage element according to. The power storage element according to claim 2, wherein the inner surface of the first wall portion facing the inside of the case includes a recess provided at a position corresponding to the first extension piece. The separator being disposed in front Symbol each folded portion of the first folded portion and the second folded portion between the first electrode and the second electrode is a biaxially oriented separator , The power storage element according to any one of claims 1 to 3. A case for accommodating the electrode body is provided.
The separator is a biaxially stretched separator.
The case accommodates the electrode body in a state where at least a predetermined region of the electrode body is pressed from both sides in the direction in which the first electrode and the second electrode overlap.
Any of claims 1 to 3, wherein the predetermined region is a region of the electrode body that is orthogonal to the first direction and corresponds to both ends of the first electrode body in a direction along the first electrode. The power storage element according to item 1. The plurality of energy storage elements according to any one of claims 1 to 3, wherein the plurality of energy storage elements are arranged in a direction in which the first electrode and the second electrode overlap each other.
A holding member for holding the plurality of power storage elements, and
Each of the plurality of power storage elements has a case for accommodating the electrode body.
Each separator of the plurality of power storage elements is a biaxially stretched separator.
The holding member is the plurality of power storage elements so that at least a predetermined region of the electrode body is pressed from both sides in the direction in which the first electrode and the second electrode overlap each other through the case in each power storage element. Hold,
The predetermined region is a region of the electrode body that is orthogonal to the first direction and corresponds to both ends of the first electrode body in a direction along the first electrode.

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