JP6935056B2 - Power storage element - Google Patents

Description

The present invention relates to a power storage element including an electrode body in which a single-wafer-shaped second electrode is arranged between the folded first electrodes.

Conventionally, a lithium ion secondary battery (hereinafter, simply referred to as “battery”) in which one of the negative electrode plate and the positive electrode plate is laminated in a zigzag shape has been known (see Patent Document 1). Specifically, as shown in FIG. 17, this battery is configured by alternately stacking a negative electrode plate 101, a positive electrode plate 104, and a separator 107 inserted between both electrode plates 101 and 104. It is an electrode laminate.

The negative electrode plate 101 is in close contact with the separator 107 on both sides, and is an electrode plate (with a long electrode plate) made of a long flexible material that is alternately folded in the longitudinal direction at predetermined intervals and laminated in a zigzag shape. ). The long electrode plate 101 of the negative electrode has a negative electrode active material layer 103 formed on both sides of the copper foil 102.

The separator 107 is a battery separator made of a long insulating film and capable of transferring charges in the thickness direction thereof. The separator 107 is folded in contact with both sides of the long electrode plate 101 of the negative electrode. Specifically, the separator 107 wraps the portion of the copper foil 102 of the long electrode plate 101 on which the negative electrode active material layer 103 is formed from both sides. That is, the long electrode plate 101 and the separator 107 that wraps both sides thereof are integrated to form an integrally long object 108.

The positive electrode plate 104 is a large number of strip-shaped electrode plates (referred to as strip-shaped electrode plates) that are in close contact with the separator 107 on both sides and are independent of each other. Each strip-shaped electrode plate 104 of the positive electrode has a positive electrode active material layer 106 formed on both sides of the aluminum foil 105.

Then, a large number of strip-shaped electrode plates 104 are alternately laminated from both sides of the integrally long object 108 composed of the long electrode plate 101 and the separator 107 to form the battery 100. That is, when laminating one integrated long object 108 and a large number of strip-shaped electrode plates 104, the integrated elongated object 108 is folded in a zigzag manner, and the strip-shaped electrode plates 104 are inserted from both sides between them to form an integrated long object. The battery 100 has a structure sandwiched between objects 108.

In the above battery 100, the integrally long object 108 is folded in a state where a force for bending inward with respect to the edge (edge corner portion) of the strip-shaped electrode plate 104 is applied at the folded portion. The negative electrode active material layer 103 may be cracked at or near the edge (edge corner portion) of the strip-shaped electrode plate 104 at the folded-back portion (see reference numeral 109 in FIG. 17).

Japanese Unexamined Patent Publication No. 2014-103082

Therefore, in the present embodiment, the first electrode is caused by applying a bending force with respect to the edge of the region in contact with the member including the second electrode at the folded portion of the member including the first electrode. It is an object of the present invention to provide a power storage element in which the active material layer of the above is hard to break.

The power storage element of this embodiment is
An electrode body including a long first member including a first electrode having an active material layer and a second member including a second electrode having a polarity different from that of the first electrode is provided.
The first member has a folded portion including a pair of parallel or substantially parallel flat portions and a turn portion connecting the ends of the pair of flat portions on one side in the first direction.
The second member is arranged at least between a pair of flat portions of the folded portion.
The turn portion is a portion on one side of the reference position, which is the position of the one-sided edge of the first direction in the region where the second member contacts in the folded portion.
The length dimension of the turn portion along the longitudinal direction of the first member is the reference of the second member in the second direction in which the flat portions of the pair of flat portions are lined up. It is larger than the length dimension of the first member when it is arranged along a semicircle whose diameter is the dimension at the position.

As described above, when the length dimension of the turn portion is arranged along the semicircular arc whose diameter is the dimension of the second member in the second direction, the length dimension of the first member (for example, α in FIG. 10). If it is larger than (see), a force that bends inward of the turn portion with the reference position of the first member as a base point is not applied or is difficult to be applied to the first member. Therefore, a force (for example, see the arrow in FIG. 13) is applied so that the first member bends inward of the turn portion with the edge of the region in contact with the second member as the base point. The occurrence of cracks in the active material layer of one electrode is suppressed.

In the power storage element,
In the second member, the edge position on one side of the first direction of the region in contact with the folded portion on the outside of each flat portion in the second direction is the same as or the reference position in the first direction. It is arranged so as to face the flat portion so as to be on the other side from the reference position.
In the second direction, the turn portion has a part of the turn portion with one flat portion of the pair of flat portions and the second member facing the one flat portion from the outside. Spreads in the direction of the boundary surface of the first reference surface extending in the direction of the boundary surface of the above, and the other flat portion of the pair of flat portions and the second member facing the other flat portion from the outside. It may be curved so as to exceed at least one reference plane of the second reference plane.

According to such a configuration, when the second member outside the flat portion tries to move along the flat portion to one side of the first direction from the reference position, the reference plane (first) in the second direction. Since the movement of the second member is hindered by abutting against the turn portion beyond the reference plane or the second reference plane), the displacement of the second member to one side in the first direction can be suppressed. ..

Further, in the power storage element,
An abutting member that comes into contact with the turn portion from the outside in the first direction may be provided.

According to such a configuration, the contact member regulates the extension of the turn portion in the first direction, so that the inside of the turn portion is set from the edge of the region where the first member contacts the second member. It is possible to more reliably suppress the application of a force that bends toward.

Further, in the power storage element,
The first member includes a first folded portion folded so as to open one side in the first direction, and a second folded portion folded so as to open the other side in the first direction. Is in a zigzag state in which
The turn portions adjacent to each other in the second direction may not be in contact with each other.

According to such a configuration, a force for bending the inside of the turn portion from the edge of the region where the first member contacts the second member is applied from the adjacent turn portion, that is, to the adjacent turn portion. By being pressed, it is possible to prevent the force caused by the pressing from being applied.

In the power storage element,
A separator included in the second member, comprising a separator arranged between the first member and the second electrode.
At the turn portion of the first member, the active material layer may be exposed without being covered by the separator.

When a force is applied that bends the active material layer from a portion not covered by the separator as a base point, cracking of the active material layer becomes remarkable at the portion. However, according to the above configuration, although the active material layer is exposed at the turn portion of the first member, a force that bends inward of the turn portion with the reference position of the first member as a base point is applied to the first member. Since it does not or is difficult to add, the occurrence of cracks in the active material layer at the reference position and its vicinity can be suppressed.

Further, the power storage element of this embodiment is
An electrode body including a long first member including a first electrode having an active material layer and a second member including a second electrode having a polarity different from that of the first electrode is provided.
The first member has a folded portion including a pair of parallel or substantially parallel flat portions and a turn portion connecting the ends of the pair of flat portions on one side in the first direction.
The second member is arranged at least between a pair of flat portions of the folded portion.
The turn portion is a portion on one side of the reference position, which is the position of one end edge of the first direction in the region where the second member contacts in the folded portion, and is among the pair of flat portions. A first reference surface extending in the direction of the boundary surface between one flat portion and the second member facing the one flat portion from the outside, and the other flat portion of the pair of flat portions. Each of the pair of flat portions has a part of the turn portion on at least one reference surface of the second reference surface extending in the direction of the boundary surface with the second member facing the other flat portion from the outside. It is curved so as to cross in the second direction where the flat parts are lined up.

According to such a configuration, at least at the reference position on the side where the turn portion exceeds the reference plane (at least one of the first reference plane and the second reference plane), the turn portion of the turn portion is based on the reference position of the first member. Since a force that bends inward is not applied to or difficult to apply to the first member, the first member bends toward the inside of the turn portion with the edge of the area in contact with the second member as the base point. The occurrence of cracking of the active material layer of the first electrode due to the application of force (for example, see the arrow in FIG. 13) is suppressed.

Based on the above, according to the present embodiment, a force is applied to the folded portion of the member including the first electrode so as to bend the folded portion of the member including the second electrode with respect to the edge of the region in contact with the member including the second electrode. It is possible to provide a power storage element in which the active material layer of one electrode is hard to break.

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 taken along the line IV-IV 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 schematic cross-sectional view for explaining the turn portion of the electrode body. FIG. 11 is a diagram for explaining the configuration of the sheet-fed member including the positive electrode and the separator. FIG. 12 is a diagram for explaining the configuration of the sheet-fed member including the positive electrode and the separator. FIG. 13 is a schematic diagram for explaining the force applied to the turn portion. FIG. 14 is a schematic view showing the configuration of the electrode body according to another embodiment. FIG. 15 is a schematic view showing the configuration of the electrode body according to another embodiment. FIG. 16 is a perspective view of a power storage device including the power storage element. FIG. 17 is a cross-sectional view schematically showing a laminated structure of a conventional battery.

Hereinafter, an embodiment of the power storage element according to the present invention will be described with reference to FIGS. 1 to 13. The power storage element includes a primary battery, a secondary battery, a capacitor, and the like. In the present embodiment, a rechargeable secondary battery will be described as an example of the power storage element. The name of each component (each component) of the present embodiment is that of the present embodiment, and may be different from the name of each component (each component) in the background technology.

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 the electron transfer that occurs with the movement of lithium ions. This type of power storage element supplies electrical energy. The power storage element may be used alone or in combination of two or more. 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 electrical energy.

As shown in FIGS. 1 to 5, the power storage element includes a long first member including the first electrode 21 and a second member including a second electrode 22 having a polarity different from that of the first electrode 21. 26, and an electrode body 2 having the above. Further, the power storage element 1 collects electricity by connecting the case 3 accommodating the electrode body 2, the external terminal 4 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 has a body 5. Further, the power storage element 1 also includes an insulating member (contact member) 6 or the like arranged between the electrode body 2 and the case 3. Further, in each figure, the configuration of the electrode body 2 is schematically shown by exaggerating the thickness of the electrodes and the like constituting the electrode body 2 in order to show the structure.

The electrode body 2 of the present embodiment has a first member including a negative electrode 21, and a second member 26 including a positive electrode 22 and a separator 25. That is, in the electrode body 2 of the present embodiment, the first electrode is the negative electrode 21, the second electrode is the positive electrode 22, and the first member includes only the negative electrode 21.

As shown in FIGS. 5 to 8, the negative electrode 21 has a metal foil 211 and a negative electrode active material layer 212 stacked 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. The negative electrode 21 has a long strip shape and has a folded portion 23 (see FIG. 8). A second member 26 is arranged between the folded-back portions 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, polymethylmethacrylate, 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-back portion 23 has a first surface 231 which is a valley fold side surface and a second surface which is a mountain fold side surface (that is, a surface opposite to the first surface 231). It includes a pair of flat portions 233 having 232 respectively and having the first surfaces 231 facing each other, and a turn portion 234 connecting the ends of the pair of flat portions 233. The negative electrode 21 of the present embodiment is in a continuous zigzag state (bellows-like shape) in a state in which adjacent folded portions 23 have a part (flat portion 233) in common with the turn portions 234 facing in the opposite direction. That is, in FIG. 8, 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). The flat portions 233A and 233B between the turn portion 234A of the first folded portion 23A and the turn portion 234B of the second folded portion 23B are shared.

In this case, in the flat portion 233A when focusing on the first folded portion 23A, the surface on the valley fold surface side of the first folded portion 23A is the first surface 231A, and the surface on the opposite side (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 fold surface side is the first. The surface 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 the folded portion 23) 231 and the second surface (the surface facing the opposite direction in the folded portion 23) 232 are reversed.

Returning to FIGS. 5 to 7, 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 elongated 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 elongated 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 lined up is the X-axis direction (second 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 the Cartesian coordinate system. In the Y-axis direction (first direction), the direction in which the turn axis S of the turn portion 234 extends (see FIG. 8) is the Z-axis direction of the Cartesian coordinate system.

As shown in FIGS. 7 to 9, each of the plurality of flat portions 233 protrudes from one side forming 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). It has a negative electrode tab 2332 (which extends in the Z-axis direction from the edge in the Z-axis direction). The flat portion 233 of the present embodiment is a portion of the folded portion 23 that is in contact with the second member 26. The flat portion main body 2331 of the flat portion 233 has a rectangular shape that is long in the Y-axis direction. In the flat portion main body 2331, both sides of the metal foil 211 are covered with the negative electrode active material layer 212 leaving the end portion on the negative electrode tab 2332 side, and the metal foil 211 is exposed in the negative electrode tab 2332. That is, the negative electrode tab 2332 does not have the negative electrode active material layer 212.

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. 9) at one end in the Z-axis direction (upper side in FIG. 9) 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 welded to the current collector 5.

Each of the plurality of turn portions 234 is a portion of the zigzag-folded negative electrode 21 in which the strip-shaped negative electrode 21 is swiveled (turned) around the turn axis S (see FIG. 8) extending in the Z-axis direction. The turn portion 234 of the present embodiment is a portion outside the reference position B, which is the position of the edge in the X-axis direction of the region where the second member 26 contacts the folded portion 23 (see FIG. 10). Also in this turn portion 234, both sides of the metal foil 211 are covered with the negative electrode active material layer 212, leaving the end portion on the negative electrode tab 2332 side. Specifically, it is as follows. Since the configuration of each turn portion 234 is the same, the description will be focused on one folded portion 23.

As shown in FIG. 10, one of the pair of flat portions 233 to which the turn portion 234 is connected (upper side in FIG. 10) and the flat portion 233A of the other flat portion 233A from the outside (upper side in FIG. 10). The virtual surface extending in the direction of the boundary surface with the second member 26 facing the second member 26 is set as the first reference surface R1, and is outside (outside) the other flat portion 233B (lower side in FIG. 10) and the other flat portion 233B. The virtual surface extending in the direction of the boundary surface with the second member 26 facing from the lower side in FIG. 10) is referred to as the second reference surface R2. In this case, the turn portion 234 is curved so that a part of the turn portion 234 exceeds at least one of the reference planes R1 and R2 in the X-axis direction. The turn portion 234 of the present embodiment is curved so as to exceed both the first reference plane R1 and the second reference plane R2 in the X-axis direction. This is the length dimension of the turn portion 234 and is the length dimension along the longitudinal direction of the negative electrode 21 (from the boundary between one flat portion 233A and the turn portion 234 (reference position B), the other flat portion 233B and the turn. The negative electrode 21 (length dimension to the boundary (reference position B) with the portion 234) is arranged along a semi-arc having the thickness dimension (dimension in the X-axis direction) of the second member 26 as the diameter. It is larger than the length dimension of (see the portion α indicated by the two-point chain line in FIG. 10). Here, "the negative electrode 21 when arranged along the semi-circular arc" is assumed that the negative electrode 21 is arranged along the semi-circular arc, and the negative electrode 21 is actually arranged along the semi-circular arc. It does not mean that it has been done.

In the electrode body 2 of the present embodiment, the turn portions 234 adjacent to each other in the X-axis direction are not in contact with each other, but may be in contact with each other.

The insulating member 6 is in contact with each turn portion 234 having such a shape from the outside in the Y-axis direction. As a result, the curved shape of each turn portion 234 is maintained, that is, it is prevented that each turn portion 234 extends in the Y-axis direction (see the portion β indicated by the alternate long and short dash line in FIG. 10). Each turn portion 234 of the present embodiment is formed by being pressed toward the flat portion 233 by the insulating member 6 from a state of extending in the Y-axis direction (see the portion β indicated by the alternate long and short dash line in FIG. 10). There is.

As described above, the first member of the present embodiment includes only the negative electrode 21. Therefore, the active material layer (negative electrode active material layer 212) of the first member (negative electrode 21) is exposed to the second member 26. That is, in the electrode body 2 of the present embodiment, the negative electrode active material layer 212 of each flat portion 233 and the negative electrode active material layer 212 of each turn portion 234 are exposed to the second member 26.

As shown in FIGS. 5, 6, 11, and 12, the positive electrode 22 has a metal foil 221 and a positive electrode active material layer 222 that is 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 the present 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 , LiaMnbPO 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 protrudes from one side forming the rectangular contour of the positive electrode body 223 and the rectangular contour of the positive electrode body 223 (in the example of the present embodiment, from the edge in the Z-axis direction). It has a positive electrode tab 224 (extending in the Z-axis direction). The positive electrode body 223 of the present embodiment has a rectangular shape that is long in the Y-axis direction. In the positive electrode body 223, both sides of the metal foil 221 are covered with the positive electrode active material layer 222, leaving the end on the positive electrode tab 224 side, and the metal foil 221 is exposed in the positive electrode tab 224. That is, the positive electrode tab 224 does not have the positive electrode active material layer 222.

The positive electrode active material layer 222 in the positive electrode body 223 faces the YZ planes (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 each other via the separator 25). Small in the (planar) direction including. 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 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 one end edge 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 welded to the current collector 5 in the same manner as the bundle of the negative electrode tab 2332 (see FIG. 3).

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 with the separator 25 in between.

The separator 25 is strip-shaped and is made 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 covers 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. 5, 11 and 12, the separator 25 has a rectangular shape, which is folded back at the central portion in the elongated direction so as to sandwich the positive electrode 22 between them, and has three sides excluding the fold portion. (Each edge) is joined (adhesive, welded, etc.). At this time, the positive electrode tab 224 protrudes from the folded separator 25 (see FIG. 5), and the bonding is performed while avoiding the positive electrode tab 224.

The separator 25 in a state of sandwiching the positive electrode 22 has a rectangular shape when viewed from the X-axis direction, the dimension in the Z-axis direction is larger than the dimension of the flat portion 233 of the negative electrode 21, and the dimension in the Y-axis direction is also the flat portion. Greater than 233 dimensions. As described above, 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 second member 26.

As shown in FIG. 10, the second member 26 is arranged between the flat portions 233 adjacent to each other in the X-axis direction and outside the outermost flat portion 233 in the X-axis direction. As a result, the positive electrode 22 is in a state of facing each surface of the flat portion 233 of the negative electrode 21.

Returning to FIGS. 1 to 4, 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. Specifically, the electrolyte is obtained by dissolving the electrolyte salt in an organic solvent. The organic solvent is, for example, cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. 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 that is resistant to the above electrolyte. 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 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 cylindrical body portion 312 is formed by connecting the end portions of the short wall portion 314 corresponding to the pair of long wall portions 313 (specifically, facing each other in the X-axis direction).

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 case body 31 accommodates the electrode body 2 so that 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). (See FIG. 4).

The lid plate 32 is a member that closes the opening of the case body 31. The contour shape of the lid plate 32 is a shape corresponding to the opening peripheral edge portion 310 (see FIG. 2) of the case main body 31. That is, the lid plate 32 is a rectangular plate material long in the Y-axis direction.

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 attached to the lid plate 32 in a state where at least a part thereof is exposed to the outside of the case 3.

The insulating member 6 is made of an insulating resin. Specifically, the insulating member 6 is formed in a bag shape in which the lid plate 32 side is opened by bending a sheet-shaped member having an insulating property cut into a predetermined shape (see FIG. 2). The insulating member 6 of the present embodiment has a bag shape along the case body 31. In the bag-shaped insulating member 6, each flat portion 233 of the negative electrode 21 and the second member 26 are substantially parallel to a portion (wall-shaped portion facing the X-axis direction) corresponding to the long wall portion 313 of the insulating member 6. The electrode body 2 is accommodated so that each turn portion 234 faces a portion (a wall-shaped portion facing the Y-axis direction) corresponding to the short wall portion 314 of the insulating member 6. At this time, each turn portion 234 of the electrode body 2 before accommodation is in a state of extending in the Y-axis direction (part β indicated by the alternate long and short dash line in FIG. 10), but is accommodated in the bag-shaped insulating member 6. Each turn portion 234 is pushed inward (on the flat portion 233 side) by the insulating member 6 and is curved so as to exceed the first reference surface R1 and the second reference surface R2 in the X-axis direction. Then, the insulating member 6 continues to abut (press) from the outside with respect to each turn portion 234 curved so as to exceed the first reference surface R1 and the second reference surface R2 in the X-axis direction. The curved state of the turn portion 234 is maintained.

Like the above power storage element 1, the negative electrode 21 is arranged along a semi-arc in which the length dimension of the turn portion 234 is the dimension (thickness dimension) in the X-axis direction of the second member 26. By making it larger than the length dimension (see α in FIG. 10), the turn is made with the reference position B of the negative electrode 21 (the edge position in the X-axis direction of the region of the negative electrode 21 in contact with the second member 26) as the base point. A bending force (see the arrow in FIG. 13) that bends inside the portion 234 is not applied to or difficult to be applied to the negative electrode 21. The details are as follows.

In an electrode body or the like in which a single-wafer-shaped electrode (positive electrode 22 in the example of the present embodiment) is arranged between the folded portions of the electrode in the zigzag state (negative electrode 21 in the example of the present embodiment), the electrode when folded in a zigzag state is used. Depending on the tension applied and the state of pressing the sheet-fed electrode arranged between the folded parts against the folds (folds of the folded parts), the turn part is formed at the boundary between the flat part and the turn part of the electrode that is zigzag folded. It is easy to generate a force that bends inward. Therefore, in the electrode body 2 of the present embodiment, the negative electrode 21 (the portion indicated by the alternate long and short dash line in FIG. 10) along the semi-arc having the length dimension of the turn portion 234 and the thickness dimension of the second member 26 as the diameter. By making it larger than the length dimension of α), it is possible to prevent the generation of a force that bends inward of the turn portion 234 at or near the reference position B of the negative electrode 21.

Therefore, in the power storage element 1 of the present embodiment, the negative electrode active material layer 212 is cracked due to the negative electrode 21 being bent toward the inside of the turn portion 234 with the edge C of the second member 26 or its vicinity as a base point. Is suppressed.

In the power storage element 1 of the present embodiment, each turn portion 234 is curved so that a part thereof exceeds both the reference planes of the first reference plane R1 and the second reference plane R2 in the X-axis direction. ..

Therefore, when the second member 26 adjacent to the flat portion 233 tries to move along the flat portion 233 toward the turn portion 234 side from the reference position B, each reference plane (first) in the X-axis direction. The movement of the second member 26 is hindered by abutting on the turn portion 234 that exceeds the reference surface R1 and the second reference surface R2). Therefore, the misalignment of the second member 26 toward the turn portion 234 can be suppressed.

Further, the power storage element 1 of the present embodiment includes an insulating member (contact member) 6 that comes into contact with the turn portion 234 from the outside in the Y-axis direction. Therefore, the insulating member 6 regulates the extension of the turn portion 234 in the Y-axis direction (see the wavy line in FIG. 10), whereby the negative electrode 21 is in the reference position (the Y-axis of the region in contact with the second member 26). It is possible to more reliably suppress the application of a force that bends toward the inside of the turn portion 234 with the edge in the direction as the base point. Moreover, by restricting the extension of the turn portion 234 in the Y-axis direction, a part of the turn portion 234 exceeds the reference plane (first reference plane R1, second reference plane R2) in the X-axis direction. The curved state of the portion 234 is maintained, and as a result, the misalignment of the second member 26 toward the turn portion 234 side is more reliably suppressed.

Further, in the power storage element 1 of the present embodiment, since the turn portions 234 adjacent to each other in the X-axis direction are not in contact with each other in the electrode body 2, the turn portions 234 are bent inward with the reference position B of the negative electrode 21 as the base point. It is possible to prevent the force from being applied from the adjacent turn portion 234. That is, it is possible to prevent the force caused by the pressing from being applied by being pressed by the adjacent turn portion 234.

If the turn portions adjacent to each other in the X-axis direction are separate members (discontinuous), even if the adjacent turn portions come into contact with each other, they easily escape in the direction away from each other and the influence of stress is small. In addition, when the negative electrode 21 in the zigzag state, that is, the negative electrode 21 is composed of one member in which a plurality of turn portions 234 are connected via the flat portion 233, the contact between the adjacent turn portions 234 is achieved. The effect of stress caused by is increased. Therefore, in the electrode body 2 of the present embodiment, the generation of stress due to the contact is suppressed by not contacting the turn portions 234 adjacent to each other in the X-axis direction.

Further, in the turn portion 234 of the negative electrode 21 of the present embodiment, the negative electrode active material layer 212 is not covered with the separator 25 and is exposed. As described above, when a force is applied such that the negative electrode active material layer 212 is bent from the portion not covered by the separator 25 as a base point, the negative electrode active material layer 21 is markedly cracked at the portion.

Also in the power storage element 1 of the present embodiment, the negative electrode active material layer 212 is exposed at the turn portion 234 of the negative electrode 21. However, in the power storage element 1 of the present embodiment, since a force that bends inward of the turn portion 234 with the reference position of the negative electrode 21 as a base point is not applied or is difficult to be applied to the negative electrode 21, the negative electrode activity in the reference position and its vicinity thereof is not applied. The occurrence of cracks in the material layer 212 is effectively suppressed.

The power storage element of the present invention is not limited to the above embodiment, and it goes without saying 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 negative electrode when the length dimension of the turn portion 234 is arranged along a semicircular arc α whose diameter is the dimension at the reference position B of the second member 26 in the X-axis direction. It is larger than the length dimension of 21, but is not limited to this configuration. For example, the length dimension of the turn portion 234 is smaller than the length dimension of the negative electrode 21 when arranged along a semicircular arc α having the dimension at the reference position B of the second member 26 in the X-axis direction as the diameter. Also, the turn portion 234 may be curved so that a part thereof exceeds at least one reference plane of the first reference plane R1 and the second reference plane R2 in the X-axis direction. According to this configuration, at least at the reference position B on the side where the turn portion 234 exceeds the reference plane (at least one of the first reference plane R1 and the second reference plane R2), the reference position B of the negative electrode 21 is used as a base point. A force that bends inside the turn portion 234 is not applied to or difficult to be applied to the negative electrode 21. Therefore, the negative electrode 21 is caused by the application of a force (for example, see the arrow in FIG. 13) that bends the negative electrode 21 toward the inside of the turn portion 234 with the edge of the region in contact with the second member 26 as the base point. The occurrence of cracks in the negative electrode active material layer 212 of 21 is suppressed.

In the power storage element 1 of the above embodiment, the second member 26 includes the separator 25, but the configuration is not limited to this. The first member may include a separator 25, i.e., the first member may include a negative electrode 21 and a separator 25. In this case, the long separator 25 sandwiches the long negative electrode 21. Further, both the first member and the second member 26 may include the separator 25. That is, when the separator 25 is arranged along the long electrode, the separator 25 is included in the first member, and when the separator 25 is arranged along the rectangular electrode, the separator 25 is included. The separator 25 is included in the second member.

In the power storage element 1 of the above embodiment, the inorganic particle layer is formed on one side of the base material in the separator 25, but the present invention is not limited to this configuration. Inorganic particle layers may be formed on both sides of the base material in the separator 25. Further, an inorganic particle layer containing inorganic particles may be formed on the surface of the negative electrode active material layer 212 or the surface of the positive electrode active material layer 222. At this time, when the inorganic particle layer is arranged along the long electrode, the inorganic particle layer is included in the first member, and the inorganic particle layer is arranged along the rectangular electrode. The inorganic particle layer is included in the second member.

In the power storage element 1 of the above embodiment, the extension of the turn portion 234 in the Y-axis direction is regulated by the insulating member 6, but the configuration is not limited to this. For example, the extension of the turn portion 234 in the Y-axis direction may be restricted by wrapping an insulating tape or the like around the electrode body 2.

In the power storage element 1 of the above embodiment, the turn portion 234 is curved so as to exceed the reference planes of both the first reference plane R1 and the second reference plane R2 in the X-axis direction, but the configuration is limited to this. Not done. Each turn portion 234 may be curved so as to exceed only one of the reference planes of the first reference plane R1 and the second reference plane R2. Further, the turn portion 234 of a plurality of turn portions 234 may not exceed the reference planes R1 and R2. Further, all the turn portions 234 do not have to be curved so as to exceed the same reference planes R1 and R2. That is, there may be a turn portion 234 that exceeds only the first reference surface R1, a turn portion 234 that exceeds only the second reference surface R2, or a turn portion 234 that exceeds both reference surfaces R1 and R2. You may.

In the power storage element 1 of the above embodiment, the inside of the turn portion 234 is hollow, but the configuration is not limited to this. For example, as shown in FIG. 14, the core member 7 may be arranged inside the turn portion 234. The core member 7 may be made of a resin such as polyethylene, polypropylene, polystyrene, or polyphenylene sulfide. The core member 7 shown in FIG. 14 has a solid cylindrical shape, but is not limited to this configuration. The core member may have a hollow cylindrical shape. When the core member has a hollow cylindrical shape, it may be configured by winding a resin film into a cylindrical shape. As long as a part of the turn portion 234 can maintain a shape exceeding the reference surfaces R1 and R2, the specific configuration of the core member is not limited.

Further, in the power storage element 1 of the above embodiment, one electrode (the negative electrode 21 in the example of the above embodiment) is in a zigzag state, but the configuration is not limited to this. In the electrode body 2, one electrode may have at least one folded-back portion 23.

For example, specifically, as shown in FIG. 15, the electrode body 2 may have a plurality of folded portions 23, each of which is composed of an independent negative electrode 21. Even with this configuration, the length dimension of the turn portion 234 is larger than the length dimension of the negative electrode 21 along the semi-arc having the thickness dimension of the second member 26 as the diameter, so that the reference position B (negative electrode) of the negative electrode 21 is formed. A force that bends inward of the turn portion 234 with respect to the edge position in the X-axis direction of the region in contact with the second member 26 in 21 is not applied to or difficult to be applied to the negative electrode 21 (folded portion 23). .. Therefore, it is possible to suppress the occurrence of cracking of the negative electrode active material layer 212 of the negative electrode 21 due to the negative electrode 21 bending toward the inside of the turn portion with the edge of the positive electrode 22 or the second member 26 as the base point.

In the power storage element 1 of the above embodiment, the positive electrode 22 is entirely covered with the separator 25, but the present invention is not limited to this configuration. The end face of the positive electrode 22 in the Y-axis direction may be open (that is, not covered with the separator 25).

In the power storage element 1 of the above embodiment, the negative electrode 21 is in a zigzag state and the positive electrode 22 is in a single-wafer shape (strip shape), but the configuration is not limited to this. The positive electrode 22 may be in a zigzag state, and the negative electrode 21 may be in a single-wafer shape.

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 to this. For example, the present invention can be applied to various secondary batteries, other primary batteries, and power storage elements of capacitors such as electric double layer capacitors.

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

1 ... power storage element, 2 ... electrode body, 21 ... negative electrode (first electrode), 21A ... mountain fold line, 21B ... valley fold line, 211 ... metal foil, 212 ... negative electrode active material layer, 22 ... positive electrode (second) (Electrodes), 221 ... Metal foil, 222 ... Positive electrode active material layer, 223 ... Positive electrode body, 224 ... Positive electrode tab, 23 ... Folded part, 23A ... First folded part, 23B ... Second folded part, 231, 231A, 231B ... First surface, 232, 232A, 232B ... Second surface, 233, 233A, 233B ... Flat part, 2331 ... Flat part body, 2332 ... Negative electrode tab, 234, 234A, 234B ... Turn part, 25 ... Separator, 26 ... Second member, 3 ... Case, 31 ... Case body, 310 ... Opening peripheral edge, 311 ... Closing part, 312 ... Body part, 313 ... Long wall part, 314 ... Short wall part, 32 ... Lid plate, 4 ... External terminal, 6 ... Insulating member (contact member), 11 ... Power storage device, 12 ... Bus bar member, 100 ... Battery, 101 ... Negative electrode plate, Long electrode plate, 102 ... Copper foil, 103 ... Negative electrode active material layer, 104 ... Positive electrode plate, strip-shaped electrode plate, 105 ... Aluminum foil, 106 ... Positive electrode active material layer, 107 ... Separator, 108 ... Integrated long object, 109 ... Part that abuts on the edge of the strip-shaped electrode plate, B ... Reference Position, C ... Edge, R1 ... First reference plane, R2 ... Second reference plane, S ... Turn axis, α ... Semi-arc whose diameter is the thickness of the second member at the reference position, β ... Turn part in the extended state

Claims (6)

An electrode body including a long first member including a first electrode having an active material layer and a second member including a second electrode having a polarity different from that of the first electrode is provided.
The first member has a folded portion including a pair of parallel or substantially parallel flat portions and a turn portion connecting the ends of the pair of flat portions on one side in the first direction.
The second member is arranged at least between a pair of flat portions of the folded portion.
The turn portion is a portion on one side of the reference position, which is the position of the one-sided edge of the first direction in the region where the second member contacts in the folded portion.
The length dimension of the turn portion along the longitudinal direction of the first member is the reference of the second member in the second direction in which the flat portions of the pair of flat portions are lined up. A power storage element that is larger than the length dimension of the first member when placed along a semi-circular arc whose diameter is the dimension at the position. In the second member, the edge position on one side of the first direction of the region in contact with the folded portion on the outside of each flat portion in the second direction is the same as or the reference position in the first direction. It is arranged so as to face the flat portion so as to be on the other side from the reference position.
In the second direction, the turn portion has a part of the turn portion with one flat portion of the pair of flat portions and the second member facing the one flat portion from the outside. Spreads in the direction of the boundary surface of the first reference surface extending in the direction of the boundary surface of the above, and the other flat portion of the pair of flat portions and the second member facing the other flat portion from the outside. The power storage element according to claim 1, which is curved so as to exceed at least one reference plane of the second reference plane. The power storage element according to claim 1 or 2, further comprising a contact member that comes into contact with the turn portion from the outside in the first direction. The first member includes a first folded portion folded so as to open one side in the first direction, and a second folded portion folded so as to open the other side in the first direction. Is in a zigzag state in which
The power storage element according to any one of claims 1 to 3, wherein the turn portions adjacent to each other in the second direction are not in contact with each other. A separator included in the second member, comprising a separator arranged between the first member and the second electrode.
The power storage element according to any one of claims 1 to 4, wherein in the turn portion of the first member, the active material layer is not covered with the separator and is exposed. An electrode body including a long first member including a first electrode having an active material layer and a second member including a second electrode having a polarity different from that of the first electrode is provided.
The first member has a folded portion including a pair of parallel or substantially parallel flat portions and a turn portion connecting the ends of the pair of flat portions on one side in the first direction.
The second member is arranged at least between a pair of flat portions of the folded portion.
The turn portion is a portion on one side of the reference position, which is the position of one end edge of the first direction in the region where the second member contacts in the folded portion, and is among the pair of flat portions. A first reference surface extending in the direction of the boundary surface between one flat portion and the second member facing the one flat portion from the outside, and the other flat portion of the pair of flat portions. Each of the pair of flat portions has a part of the turn portion on at least one reference surface of the second reference surface extending in the direction of the boundary surface with the second member facing the other flat portion from the outside. A power storage element that is curved so as to cross in the second direction in which flat parts are lined up.

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