JP2019053820A - Power storage element - Google Patents

Abstract

To provide a power storage element in which a stress in a turn part of an electrode body folded in a zigzag is suppressed.SOLUTION: A power storage element comprises an electrode body having a long first member including a first electrode 21, and a second member 26 that includes a second electrode 22 of which a polarity is different from that of the first electrode. The first member includes a first surface and a second surface opposite to the first surface, and includes at least one folding part including a pair of flat parts 233 in which both first surfaces are faced and a turn part 234 connecting both end parts. The second member is arranged between the pair of flat parts. The turn part includes a thin position that a part of the surface of an inner side of the folding part is recessed to a surface in an outer side from the other position, and a gap is formed in between the turn part and the second member.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a power storage device including an electrode body in which a second electrode is disposed between folded first electrodes.

  Conventionally, a lithium ion secondary battery (hereinafter simply referred to as “battery”) in which one electrode plate of a negative electrode plate and a positive electrode plate is stacked in a zigzag manner is known (see Patent Document 1). Specifically, as shown in FIG. 19, this battery is configured by alternately stacking negative electrode plates 101, positive electrode plates 104, and separators 107 inserted between both electrode plates 101 and 104. Electrode stack.

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

  The separator 107 is a battery separator made of a long insulating film and capable of moving charges in the thickness direction. The separator 107 is folded in contact with both surfaces of the negative electrode plate 101. Specifically, the separator 107 wraps the portion of the copper foil 102 of the long electrode plate 101 where 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 integral long object 108.

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

  A battery 100 is configured by alternately laminating a plurality of strip-shaped electrode plates 104 from both sides of an integrated long object 108 including a long electrode plate 101 and a separator 107. That is, when laminating a single long piece 108 and a large number of strip-shaped electrode plates 104, the long piece 108 is folded in a zigzag manner, and the strip-shaped electrode plates 104 are inserted from both sides to be integrated long. The battery 100 has a structure sandwiched between the objects 108.

  In the battery 100 described above, stress is easily generated in the turn portion of the integrally long object 108 folded in a zigzag manner. Specifically, the volume of the long electrode plate 101 increases with the expansion of the active material, etc., but in the turn portion, the long electrode plate 101 with the increased volume has a small escape allowance, so that the stress is increased. Prone to occur. In particular, the greater the thickness of the integral long object 108, the more pronounced the stress generated in the turn portion.

JP 2014-103082 A

  In view of this, an object of the present embodiment is to provide a power storage device that can suppress stress generated in the turn portion in the folded portion of the first member including the first electrode.

The electricity storage device of this embodiment is
An electrode body having a long first member including a first electrode and a second member including a second electrode having a polarity different from that of the first electrode;
The first member has a first surface and a second surface opposite to the first surface, and a pair of flat portions in which the first surfaces are opposed to each other, and the pair of flat surfaces Having at least one folded part including a turn part connecting the ends of the parts,
The second member is disposed between the pair of flat portions,
The turn portion has a thin-walled portion in which a part of the inner surface of the folded portion is recessed toward the outer surface from other portions,
A gap is formed between the turn portion and the second member.

  According to this configuration, in the first member, the turn portion of the folded portion has a thin portion, so that stress generated in the turn portion can be suppressed.

In the storage element,
The edge on the turn part side of the second member may be located at a position overlapping the thin portion as seen from the direction in which the pair of flat parts are arranged.

  In this way, the edge of the second member is thin when viewed from the direction in which the pair of flat portions are arranged between the folded portions where the thin portion and the thick portion (the portion other than the thin portion) are formed. In the second member (see, for example, FIG. 11), in the second member, the end position of the portion pressed (clamped) by the thick portion, that is, the thick portion of the folded portion A slight step is generated at the boundary position between the thin portion and the thin portion, thereby effectively suppressing the displacement of the second member between the folded portions.

In addition, the power storage element is
A case for accommodating the electrode body;
The electrode body is accommodated in the case in a state where an area overlapping with an end position of the thin portion is pressed from both sides in the direction in which the pair of flat portions are aligned as viewed from the direction in which the pair of flat portions are aligned. May be.

  According to such a configuration, in the second member, a large force is applied to the end position of the portion that is pressed (clamped) by the thick portion of the folded portion (that is, the end portion position of the thin portion). The positional deviation of the second member between the folded portions can be more reliably suppressed.

In the storage element,
The first electrode may include a metal foil and an active material layer superimposed on an inner surface of the metal foil in a region corresponding to the thin portion.

  If the metal foil is exposed so as to face the second member in the thin portion, the dendrite is easily generated and grown due to current concentration in the metal foil. However, according to the above configuration, since the surface facing the inside of the metal foil is covered with the active material layer in the region corresponding to the thin-walled portion, the current concentration in the portion is prevented, whereby the metal Generation | occurrence | production of the said dendrite in foil, the growth, etc. can be suppressed.

  In addition, since there is a gap between the turn part and the second member, the second member extends toward the back of the turn part due to expansion and contraction associated with charge / discharge of the second electrode included in the second member. Or move. The current concentration can be suppressed by covering the surface of the metal foil facing the second member side in the region corresponding to the thin-walled portion with the active material layer.

Further, in the power storage element,
An electrolyte,
A case for accommodating the electrolytic solution and the electrode body,
The first electrode includes the metal foil disposed over the entire region in the longitudinal direction at the folded portion, and the active layer that is overlapped over the entire region in the longitudinal direction of the surface of the metal foil facing the inside of the folded portion. A material layer,
In the longitudinal direction, the density of the portion corresponding to the thin portion of the active material layer may be higher than the density of other portions.

  As described above, when the active material layer is disposed in the turn part, the stress associated with the expansion and contraction is generated in the turn part due to the expansion and contraction of the active material layer accompanying charging and discharging of the power storage element. The expansion and contraction amount of the active material layer accompanying the charge / discharge is suppressed by increasing the density of the active material layer in the thin-walled portion and reducing the liquid permeability of the electrolyte solution. It is possible to suppress the generation of stress associated with.

  As mentioned above, according to this embodiment, the electrical storage element which can suppress the stress which arises in the turn part in the folding | turning part of the 1st member containing a 1st electrode can be provided.

FIG. 1 is a perspective view of a power storage device according to this embodiment. FIG. 2 is an exploded perspective view of the power storage element. 3 is a cross-sectional view taken along the line III-III in FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. FIG. 5 is a perspective view for explaining the electrode body. 6 is a schematic cross-sectional view at the position VI-VI in FIG. FIG. 7 is a diagram for explaining the configuration of the negative electrode. FIG. 8 is a diagram for explaining the configuration of the negative electrode. FIG. 9 is a perspective view for explaining the structure of the negatively folded negative electrode. FIG. 10 is a perspective view for explaining the folded portion. FIG. 11 is an enlarged cross-sectional view of the turn portion of the electrode body and its periphery. FIG. 12 is a diagram for explaining the configuration of the second member including the positive electrode and the separator. FIG. 13 is a diagram for explaining the configuration of the second member including the positive electrode and the separator. FIG. 14 is a schematic diagram for explaining a region that is easily compressed in the electrode body. FIG. 15 is a diagram illustrating a boundary portion between a flat portion and a turn portion in an electrode body according to another embodiment. FIG. 16 is a diagram illustrating a boundary portion between a flat portion and a turn portion in an electrode body according to 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 cross-sectional view schematically showing a stack structure of a conventional battery.

  Hereinafter, an embodiment of a power storage device according to the present invention will be described with reference to FIGS. Examples of the power storage element include a primary battery, a secondary battery, and a capacitor. In the present embodiment, a chargeable / dischargeable secondary battery will be described as an example of a power storage element. In addition, the name of each component (each component) of this embodiment is a thing in this embodiment, and may differ from the name of each component (each component) in background art.

  The electricity storage device of this embodiment is a nonaqueous electrolyte secondary battery. More specifically, the power storage element is a lithium ion secondary battery that utilizes electron transfer that occurs as lithium ions move. This type of power storage element supplies electrical energy. One or a plurality of power storage elements are used. Specifically, the storage element is used singly when the required output and the required voltage are small. On the other hand, when at least one of a required output and a required voltage is large, the power storage element is used in a power storage device in combination with another power storage element. In the power storage device, a 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. In addition, the power storage element 1 includes a case 3 that houses the electrode body 2, an external terminal 4 that is attached to the case 3 with at least a portion exposed to the outside, and a current collector that connects the electrode body 2 and the external terminal 4. And a body 5. The power storage device 1 also includes an insulating member 6 and the like disposed between the electrode body 2 and the case 3. In each figure, in order to show the structure, the configuration of the electrode body 2 is schematically shown, such as exaggerating the thickness of the electrodes that constitute the electrode body 2.

  As shown in FIGS. 5 and 6, the electrode body 2 includes a long first member including the first electrode 21 and a second electrode 22 including a second electrode 22 having a polarity different from that of the first electrode 21. Member 26. In the electrode body 2 of the present embodiment, the first electrode 21 is a negative electrode, and the second electrode 22 is a positive electrode. The first member includes only the negative electrode 21, and the second member 26 includes the positive electrode 22 and the separator 25.

  As illustrated in FIGS. 7 and 8, the negative electrode 21 includes a metal foil 211 and a negative electrode active material layer 212 that is stacked on both surfaces 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 this embodiment is a copper foil, for example. As shown in FIG. 9, the negative electrode 21 has a long strip shape and has at least one folded portion 23 folded at the turn portion 234. Specifically, it is as follows.

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

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

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

  The negative electrode active material layer 212 may further include a conductive additive such as ketjen black (registered trademark), acetylene black, or graphite. The negative electrode active material layer 212 of this embodiment does not have a conductive additive.

  As shown in FIG. 10, the folded portion 23 includes a first surface 231 that is a valley-folded surface and a second surface that is a mountain-folded surface (that is, a surface opposite to the first surface 231). Each of the flat surfaces 233 includes a pair of flat portions 233 and the first surfaces 231 face each other, and a turn portion 234 that connects the ends of the pair of flat portions 233. The negative electrode 21 of the present embodiment is in a zigzag folded state (bellows shape) in which the turn-up portions 234 face each other and the adjacent folded portions 23 are continuous with a part (flat portion 233) in common.

  In other words, the negative electrode 21 has a folded portion (first folded portion) 23A that is folded back so that one side in a predetermined direction (left-right direction in FIG. 9) is opened, and the other side in the predetermined direction is opened. In this state, the folded portions (second folded portions) 23B that are folded are alternately folded. When attention is paid to one folded portion (first folded portion) 23A, the first folded portion 23A and the adjacent folded portion (second folded portion in FIG. 9) (second folded portion) 23B 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 made common.

  In this case, as shown in FIG. 9, in the flat portion 233A when paying attention to the first folded portion 23A, the surface on the valley folded surface side in the first folded portion 23A is the first surface 231A, and the opposite side The surface (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 the second folded portion 23B is focused, the surface on the valley folded surface side in the second folded portion 23B is the first. The surface 231 </ b> B on the opposite side (the surface on the mountain fold side) is the second surface 232 </ b> B. That is, in the flat portions 233A and 233B shared by 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 when the first folded portion 23A is focused on. One surface (surface facing the folded portion 23) 231 and the second surface (surface facing the opposite direction in the folded portion) 232 are reversed.

  Specifically, as shown in FIG. 9, in the negative electrode 21, the flat portions 233 and the turn portions 234 are alternately formed by alternately folding the strip-shaped negative electrodes 21 at predetermined intervals in the longitudinal direction. . That is, in the long negative electrode 21, the mountain fold and the valley fold are alternately repeated at the position of the mountain fold line 21A and the position of the valley fold line 21B alternately set at predetermined intervals in the longitudinal direction shown in FIG. As a result, the spelling is folded. Accordingly, 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 being arranged in parallel or substantially in parallel, and each of the plurality of turn portions 234 being adjacent to each other. The ends of the flat portion 233 on the one end side in the longitudinal direction are alternately connected to the ends on the other end side.

  Moreover, in this strip-shaped negative electrode 21, as shown in FIG.7 and FIG.8, the area | region (area | region used as the turn part 234 when folded) 210 and the area | region (folded back) containing the mountain fold line 21A are included. In the negative electrode active material layer 212 on the surface side that becomes the inner side when folded, a groove extending in the short direction of the negative electrode 21 is formed. In other words, the turn portion 234 of the folded portion 23 has a thin portion in which a part of the inner surface (region 210) of the folded portion 23 is recessed toward the outer surface from other portions. In the negative electrode 21 of the present embodiment, the entire turn portion 234 is a thin portion.

  In the negative electrode 21 of the present embodiment, in the region 210, the groove is formed on both surfaces of the negative electrode 21 (that is, each of the negative electrode active material layers 212 stacked on both surfaces of the metal foil 211) (FIG. 7). And FIG. 8). This groove is formed by compressing the region 210 of the negative electrode active material layer 212 in the thickness direction after the negative electrode active material is applied to the metal foil 211 to form the negative electrode active material layer 212 having a certain thickness. ing. That is, in the negative electrode active material layer 212, the density of the portion (that is, the region 210) corresponding to the turn portion (thin portion) 234 is higher than the density of the other portion (the portion corresponding to the flat portion 233). . Then, the folded portion 23 is formed by folding the negative electrode 21 at the position of the groove with the edge of the second member 26 in contact with the groove provided in the region 210 of the negative electrode 21. At this time, the edge of the second member 26 on the turn part 234 side is located inside the turn part 234 as shown in FIG. A gap γ is formed between the turn part 234 and the end of the second member 26.

  In the following, the direction in which the flat portions 233 are arranged is the X-axis direction in the orthogonal coordinate system, and the direction in which the turn portions 234 are arranged with respect to the flat portion 233 (the left-right direction in FIG. 9) is the Y-axis direction in the orthogonal coordinate system. The direction in which the turning axis S of the turn portion 234 extends (see FIG. 9) is taken as the Z-axis direction of the orthogonal coordinate system.

  As shown in FIGS. 7, 9, and 10, each of the plurality of flat portions 233 protrudes from a rectangular flat portion main body 2331 and one side that forms a rectangular outline of the flat portion main body 2331 (this book The example embodiment includes a negative electrode tab 2332 (extending in the Z-axis direction from the edge in the Z-axis direction). The flat portion main body 2331 of the present embodiment has a rectangular shape that is long in the Y-axis direction. In the flat portion main body 2331, both surfaces of the metal foil 211 are covered with the negative electrode active material layer 212 except for the end on the negative electrode tab 2332 side, and the metal foil 211 is exposed on the negative electrode tab 2332. That is, the negative electrode tab 2332 does not have the negative electrode active material layer 212.

  In the zigzag folded negative electrode 21, 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 formed from one end (right side in FIG. 9) in the Y-axis direction at one end (upper side in FIG. 9) of the flat portion main body 2331 in the Z-axis direction. 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 via the external terminals 4 and the current collector 5 (see FIG. 3). The bundle of negative electrode tabs 2332 of this embodiment is connected to the current collector 5 by welding.

  In each of the plurality of turn portions 234, the belt-shaped negative electrode 21 is swung (turning direction) in the zigzag negative electrode 21 with the axis extending in the Z-axis direction as a swivel axis S (see FIG. 9) (in other words, swiveling) It is a part that is curved around the axis S). Also in the turn part 234, both surfaces of the metal foil 211 are covered with the negative electrode active material layer 212. That is, in the turn part 234, the negative electrode active material layer 212 is overlaid on the surface of the metal foil 211 facing the inside of the turn part 234 (second member 26 side). Further, the negative electrode active material layer 212 is also superimposed on the surface of the metal foil 211 facing the outside of the turn part 234.

  This turn part 234 is thinner than the flat part 233 (thickness dimension is small). That is, the turn part 234 is a thin part in the negative electrode 21 (folded part 23), and the flat part 233 is a thick part in the negative electrode 21 (folded part 23) (see FIG. 8).

  As illustrated in FIGS. 5, 6, 12, and 13, the positive electrode 22 includes a metal foil 221 and a positive electrode active material layer 222 that is stacked on both surfaces of the metal foil 221. That is, the positive electrode 22 includes one metal foil 221 and a pair of positive electrode active material layers 222. The metal foil 221 of this embodiment is, for example, an aluminum foil. The positive electrode 22 is disposed between the flat portions 233 adjacent to each other in the X-axis direction in the zigzag negative electrode 21. For this reason, the electrode body 2 of this embodiment has a plurality of positive electrodes 22.

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

The positive electrode active material of this embodiment is a lithium metal oxide, for example. 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 , LiaNixCoyMnzO ₂ etc.), LiaMeb ( XOc) d (Me represents one or more transition metals, and X represents, for example, P, Si, B, V) (LiaFebPO ₄ , LiaMnbPO 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 include a conductive additive such as ketjen black (registered trademark), acetylene black, or graphite. The positive electrode active material layer 222 of this embodiment has acetylene black as a conductive additive.

  Specifically, each of the plurality of positive electrodes 22 includes a positive electrode main body (electrode main body) 223 and a positive electrode tab (extending piece) 224 extending from the periphery of the positive electrode main body 223. Specifically, each of the plurality of positive electrodes 22 protrudes from a rectangular positive electrode main body (electrode main body) 223 and one side constituting the rectangular outline of the positive electrode main body 223 (in the example of the present embodiment, in the Z-axis direction). Positive electrode tab 224 (extending in the Z-axis direction from the edge). The positive electrode main body 223 of the present embodiment has a rectangular shape that is long in the Y-axis direction. In the positive electrode body 223, the entire area of both surfaces of the metal foil 221 is covered with the positive electrode active material layer 222, 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 main body 223 is smaller in the Z-axis direction than the negative electrode active material layer 212 of the flat portion 233 facing in the X-axis direction (specifically, facing through the separator 25).

  In the electrode body 2, the positive electrode tab 224 of each positive electrode 22 overlaps when viewed from the X-axis direction. In the positive electrode 22 of the present embodiment, each positive electrode tab 224 includes the position of the negative electrode tab 2332 on the other end in the Y-axis direction (the upper side in FIG. 5) of the positive electrode body 223 in the Z-axis direction (upper side in FIG. 5). Is extending in the Z-axis direction from the end on the opposite side (left side in FIG. 5). The positive electrode tabs 224 extending from each of the plurality of positive electrode bodies 223 are bundled and connected via the external terminals 4 and the current collector 5. The bundle of the positive electrode tabs 224 of the present embodiment is connected to the current collector 5 by welding similarly to the bundle of the negative electrode tabs 2332 (see FIG. 3).

  The separator 25 is an insulating member and is disposed between the negative electrode 21 and the positive electrode 22. Thereby, in the electrode body 2, the negative electrode 21 and the positive electrode 22 are insulated from each other. The separator 25 holds the electrolytic solution in the case 3. Thereby, at the time of charging / discharging of the electrical storage element 1, a lithium ion becomes movable between the negative electrode 21 and the positive electrode 22 which oppose on both sides of the separator 25.

The separator 25 has a band shape, and is constituted by a porous film such as polyethylene, polypropylene, cellulose, polyamide, and the like. In the separator 25 of the present embodiment, an inorganic layer containing inorganic particles such as SiO ₂ particles, Al ₂ O ₃ particles, boehmite (alumina hydrate) is provided on a substrate formed of a porous film. It is formed with. The base material of the separator 25 of this 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 main body 223 so as to be sandwiched in the X-axis direction. As shown in FIGS. 5, 12, and 13, the separator 25 is a rectangular shape that is folded back at the center in the longitudinal direction so that the positive electrode 22 is sandwiched between the three sides (excluding the turn portion) ( Each edge) is joined (adhered, welded, etc.). At this time, the positive electrode tab 224 protrudes from the folded separator 25 (see FIG. 5), and the joining is performed avoiding the positive electrode tab 224.

  The separator 25 in a state where the positive electrode 22 is sandwiched 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 a flat portion. It is larger than the size of 233. As described above, in the electrode body 2 of this embodiment, the positive electrode 22 and the separator 25 sandwiching the positive electrode 22 constitute the second member 26.

  As described above, each of the plurality of second members 26 has one end edge in the Y-axis direction (end edge on the turn part 234 side) inside the turn part (thin portion) 234 (back in the Y-axis direction). ) Are disposed between the folded portions 23. In other words, the edge on the turn portion 234 side of each second member 26 is a thin portion (this embodiment) when viewed from the X-axis direction (the direction in which the second member 26 is sandwiched between the folded portions 23). In the example shown in FIG.

  Returning to FIGS. 1 to 4, the case 3 includes 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 the case 3, an internal space is defined by the case main body 31 and the lid plate 32. The case 3 accommodates the electrolyte together with the electrode body 2 in this internal space.

This electrolytic solution is a non-aqueous solution electrolytic solution. This electrolytic solution is obtained by dissolving an electrolyte salt in an organic solvent. Examples of the organic solvent include cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. The electrolyte salt is LiClO ₄ , LiBF ₄ , LiPF ₆ or the like. The electrolytic solution of the present embodiment was prepared by adding 1 mol / L LiPF ₆ to a mixed solvent prepared by adjusting ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at 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 electrolyte. The case 3 of the present embodiment is formed of an aluminum metal material such as aluminum or an aluminum alloy, for example.

  The case main body 31 includes a plate-like closing part 311 and a cylindrical body part (peripheral wall) 312 connected to the periphery of the closing part 311.

  The closing portion 311 is positioned at the lower end of the case body 31 when the case body 31 is arranged with the opening facing upward (ie, the bottom wall portion of the case body 31 when the opening faces upward). Part). The obstruction | occlusion part 311 of this embodiment is rectangular shape.

  The body portion 312 has a rectangular tube shape, more specifically, a flat rectangular tube shape. The body portion 312 has a pair of long wall portions 313 extending from the long side at the periphery of the closing portion 311 and a pair of short wall portions 314 extending from the short side at the periphery of the closing portion 311. 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), a rectangular tube-shaped body portion 312 is formed.

  As described above, the case body 31 has a rectangular tube shape (that is, a bottomed rectangular tube shape) in which one end portion 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. The outline shape of the cover plate 32 is a shape corresponding to the opening peripheral edge 310 (see FIG. 2) of the case main body 31. That is, the lid plate 32 is a rectangular plate material that is long in the Y-axis direction.

  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 accommodated (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.

  In each folded portion 23 of the zigzag folded negative electrode 21, the thickness dimension in the X-axis direction of the turn part 234 and the vicinity thereof is slightly larger than the thickness dimension of the pair of flat portions 233 in the X-axis direction. For this reason, when the electrode body 2 is accommodated in the case 3 and pressed (pressed) in the X-axis direction from the case 3 (the pair of long wall portions 313), the second member is interposed between the folded portions 23. 26, both ends in the Y-axis direction (that is, a portion close to the turn portion 234 of each folded portion 23 and a portion where the turn portion 234 is adjacent in the X-axis direction: see region α in FIG. 14) are pressed in the X-axis direction. The That is, when viewed from the X-axis direction, the electrode body 2 has an end position of the turn portion 234 in the longitudinal direction of the negative electrode 21 (specifically, in the longitudinal direction of the negative electrode 21 (that is, along the long negative electrode 21). In the direction, the region α overlapping with the position where the thickness dimension of the folded portion 23 starts to decrease is accommodated in the case 3 in a state of being pressed from both sides in the X-axis direction.

  The external terminal 4 is a part that is electrically connected to an external terminal of another power storage element or an external device. For this reason, the external terminal 4 is formed of a conductive member. The external terminal 4 is formed of a metal material having high weldability. For example, the positive external terminal 4 is formed of an aluminum-based metal material such as aluminum or an aluminum alloy, and the negative external terminal 4 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 with at least a part thereof exposed to the outside of the case 3.

  The insulating member 6 is made of an insulating resin. Specifically, as shown in FIGS. 2 to 4, the insulating member 6 is formed in a bag shape by bending an insulating sheet-like member cut into a predetermined shape. The insulating member 6 of the present embodiment has a bag shape along the case 3.

  According to the power storage device 1 described above, in the negative electrode 21 (first member), the turn portion 234 of the folded portion 23 has a thin portion, so that stress generated in the turn portion 234 is suppressed. In addition, since the negative electrode active material layer 212 inside the turn portion (thin portion) 234 is thinner than the negative electrode active material layer 212 of the flat portion 233, there is a gap between the negative electrode 21 and the second member 26 in the turn portion 234. γ is formed (see FIG. 11). Thereby, the gas generated at the time of charging / discharging easily escapes to the outside through the gap γ, and the portion of the second member 26 located inside the turn portion 234 through the gap γ or the turn It becomes easy to be supplied to the negative electrode active material layer 212 of the portion 234.

  Further, in the electricity storage device 1 of the present embodiment, the folded portion 23 in which the thin portion (turn portion 234) and the thick portion (other portions (flat portion 233 in the example of the present embodiment)) are formed. Since the edge of the second member 26 overlaps with the turn portion (thin portion) 234 when viewed from the X-axis direction (see, for example, FIG. 11), the second member 26 has a thick wall. At the end position of the part pressed (clamped) by the part (flat part 233), that is, at the boundary position between the thick part (flat part 233) and the thin part (turn part 234) of the folded part 23 A slight level difference occurs (see symbol β in FIG. 11). Thereby, the position shift of the 2nd member 26 between the folding | returning parts 23 is suppressed effectively. Note that the partial enlarged view of FIG. 11 schematically illustrates the step at the boundary position with emphasis.

  In this case, when viewed from the X-axis direction, the thickness T1 of the portion that overlaps the thin portion of the second member 26 (the turn portion 234 in the example of the present embodiment) is the thickness of the second member 26. The thickness may be larger than the thickness T2 of the portion pressed against the meat portion (flat portion 233 in the example of the present embodiment). Thereby, the position shift of the 2nd member 26 between the folding | returning parts 23 is suppressed more effectively.

  Further, in the power storage device 1 of the present embodiment, the electrode body 2 has the end position (that is, the end portion of the turn portion 234 in the longitudinal direction of the negative electrode 21 as viewed from the X-axis direction (the normal direction of the second member 26)) In the example of the present embodiment, the region α (see FIG. 14) that overlaps the end position of the thin portion is accommodated in the case 3 while being pressed from both sides in the X-axis direction. For this reason, in the second member 26, a large force is applied to the end position of the portion pressed (clamped) by the thick portion (flat portion 233) of the folded portion 23, and as a result, the gap between the folded portions 23 is obtained. Thus, the positional deviation of the second member 26 is more reliably suppressed.

  If the metal foil 211 is exposed so as to face the second member 26 in the turn part 234, the metal foil 211 is likely to generate dendrite and grow due to current concentration. Therefore, in the electricity storage device 1 of the present embodiment, the negative electrode 21 faces the metal foil 211 and the second member 25 side (inside the folded portion 23) in the metal foil 211 in a region corresponding to the turn portion 234. The negative electrode active material layer 212 overlaid on the surface, that is, the surface facing the second member 26 side of the metal foil 211 is covered with the negative electrode active material layer 212 to suppress the current concentration. Thereby, generation | occurrence | production of the said dendrite in the metal foil 211, its growth, etc. are suppressed.

  More specifically, in the electricity storage device 1 of the present embodiment, since there is a gap γ between the turn portion 234 and the second member 26 (see FIG. 11), the positive electrode 22 included in the second member 26 is charged. There is a possibility that the second member 26 extends or moves toward the back of the turn part 234 (toward the upper side in FIG. 11) due to expansion and contraction accompanying discharge. For this reason, the second member 26 approaches the metal foil 211 of the turn part 234, and new problems such as generation and growth of dendrites accompanying current concentration may occur. However, the current concentration is suppressed by covering the surface of the metal foil 211 facing the second member 26 side with the negative electrode active material layer 212 as in the turn part 234 of the present embodiment, and thereby the metal foil. The generation and growth of the dendrite at 211 are suppressed. Furthermore, in the turn part 234 of the present embodiment, the gap γ is reduced by the negative electrode active material layer 212 overlaid on the metal foil 211, whereby the elongation and movement of the second member 26 can be suppressed.

  When the negative electrode active material layer 212 is disposed in the turn part 234 as in the negative electrode 21 of the present embodiment, the negative electrode active material layer 212 expands and contracts as the power storage element 1 is charged / discharged. The accompanying stress is generated in the turn part 234. Therefore, in the power storage device 1 of the present embodiment, the density of the portion corresponding to the turn portion (thin portion) 234 of the negative electrode active material layer 212 in the long direction of the negative electrode 21 (the direction along the long negative electrode 21). Is made higher than the density of other parts (in the example of this embodiment, the flat part 233). As described above, by increasing the density of the negative electrode active material layer 212 of the turn part 234 and reducing the liquid permeability of the electrolytic solution, the amount of expansion and contraction of the negative electrode active material layer 212 accompanying the charge / discharge can be suppressed. Thereby, in the electrical storage element 1 of this embodiment, generation | occurrence | production of the stress accompanying the said expansion / contraction in the turn part 234 can be suppressed.

  In addition, as described above, when the density of the negative electrode active material layer 212 in the turn part 234 is higher than the density of the negative electrode active material layer 212 in the flat part 233, the negative electrode active material layer as in the power storage element 1 of the present embodiment. The binder at 212 is preferably polyvinylidene fluoride. This is because the use of polyvinylidene fluoride as the binder increases the binding force between the negative electrode active material layer 212 and the metal foil 211, thereby preventing the negative electrode active material layer 212 from being peeled off. This is because current concentration due to peeling of the negative electrode active material layer 212 hardly occurs.

  In the case where the density of the negative electrode active material layer 212 in the turn part 234 is not higher than the density of the negative electrode active material layer 212 in the flat part 233, sodium carboxymethylcellulose (SBR) -styrene butadiene is used as the binder of the negative electrode active material layer 212. It is preferable to use a copolymer (CMC). This is because when the binder is SBR-CMC, the negative electrode active material layer 212 of the turn part 234 does not have to be higher than the density of the negative electrode active material layer 212 of the flat part 233. This is because a decrease in the binding force with the foil 211 does not occur, so that current concentration due to the peeling of the negative electrode active material layer 212 hardly occurs.

  In the electricity storage device 1 of the present embodiment, in the turn part 234, the negative electrode active material layer 212 inside the metal foil 211 is disposed in the entire area in the Z-axis direction, and an electrolyte (excess electrolyte: Electrolyte solution stored in the lower part of the case 3 without being able to hold the separator 25 is stored. For this reason, when the electricity storage device 1 is arranged with the turn portion 234 extending in the direction of gravity, that is, when the electricity storage device 1 is arranged with the external terminal 4 facing upward, the negative electrode active at the lower end of the turn portion 234. In contact with the material layer 212, the electrolytic solution (excess electrolytic solution) is sucked up by the negative electrode active material layer 212. As a result, the electrolytic solution is suitably supplied to the negative electrode active material layer 212 on the inner peripheral side of the turn part 234 where the electrolytic solution is difficult to permeate.

  In addition, the electrical storage element of this invention is not limited to the said embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention. For example, the configuration of another embodiment can be added to the configuration of a certain embodiment, and a part of the configuration of a certain embodiment can be replaced with the configuration of another embodiment. Furthermore, a part of the configuration of an embodiment can be deleted.

  In the folded portion 23 of the above-described embodiment, the thin portion (the portion in which a part of the inner surface of the folded portion 23 is recessed toward the outer surface) is the turn portion 234 in the longitudinal direction of the negative electrode 21. However, the present invention is not limited to this configuration. The thin part may be provided in a part of the turn part 234 in the longitudinal direction of the negative electrode 21. According to such a configuration, the stress generated in the turn part 234 is suppressed.

  Moreover, in the turn part 234 of the said embodiment, although the negative electrode active material layer 212 of both surfaces of the metal foil 211 is thinner than the negative electrode active material layer 212 of the flat part 233, it is not limited to this structure. For example, in the turn part 234, only the negative electrode active material layer 212 inside the metal foil 211 may be thinner than the negative electrode active material layer 212 of the flat part 233.

  Even with this configuration, in the negative electrode 21 (first member), the turn part 234 of the folded part 23 is thinner than the other part (flat part 233), that is, the negative electrode active material layers 212 on both surfaces of the metal foil 211. Is thinner than the case where it has the same thickness as that of the negative electrode active material layer 212 of the flat portion 233, so that the stress generated in the turn portion 234 is suppressed.

  Also with this configuration, since the negative electrode active material layer 212 inside the turn part 234 is thinner than the negative electrode active material layer 212 of the flat part 233, the gap γ is formed between the negative electrode 21 and the second member 26 in the turn part 234. Is formed. Accordingly, the gas generated during charging / discharging easily escapes to the outside through the gap, and the electrolyte solution passes through the gap and the portion of the second member 26 located inside the turn part 234 or the turn part 234. The negative electrode active material layer 212 is easily supplied.

  In the electrode body 2 of the above-described embodiment, the end edge of the second member 26 on the turn part 234 side is in contact with the inner side surface of the turn part 234, but is not limited to this configuration. The edge of the second member 26 on the turn part 234 side may not be in contact with the inner surface of the turn part 234.

  In the negative electrode 21 (folded portion 23) of the above embodiment, the boundary between the flat portion 233 and the turn portion 234 has a stepped shape, but is not limited to this configuration. For example, as shown in FIGS. 15 and 16, the turn part 234 may have a configuration in which the thickness dimension gradually decreases from the boundary between the flat part 233 and the turn part 234. In this case, in the longitudinal direction of the negative electrode 21, the position (thin end position) where the thickness dimension of the folded portion 23 begins to decrease is the boundary position between the flat portion 233 and the turn portion 234.

  In the electricity storage device 1 of the above embodiment, the case 3 presses the entire electrode body 2 in the X-axis direction, but is not limited to this configuration. The electrode body 2 is only required to be pressed from both sides in the X-axis direction at least in the region 3 overlapping the end position of the turn part 234 when viewed from the X-axis direction inside the case 3 (see FIG. 14). This compression may be performed by the case 3 or may be performed by a member disposed inside the case 3.

  For example, a convex portion that protrudes from the inner surface of the case 3 toward the electrode body 2 may be formed by embossing the case 3, and the electrode body 2 may be pressed by the convex portion. Moreover, you may press the electrode body 2 by enlarging the thickness of the area | region corresponding to the part which wants to press the electrode body 2 among the insulating members 6 accommodated in case 3. FIG. 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, the insulating tape may be applied so that the outer peripheral dimension of the electrode body 2 is smaller after the insulating tape is applied than before the insulating tape is applied.

  Moreover, in the said embodiment, although the case where an electrical storage element was used as a nonaqueous electrolyte secondary battery (for example, lithium ion secondary battery) which can be charged / discharged was demonstrated, the kind and magnitude | size (capacity | capacitance) of an electrical storage element are arbitrary. It is. Moreover, in the said embodiment, although the lithium ion secondary battery was demonstrated as an example of an electrical storage element, it 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, battery) 1 of the above-described embodiment may be used for a power storage device (a battery module in the case where the power storage element is a battery) 11 as illustrated in FIGS. 17 and 18, for example. The power storage device 11 includes a plurality of power storage elements 1, a plurality of adjacent members 12 adjacent to the power storage elements 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 And a bus bar 14 that connects the external terminals 4 to each other in a conductive manner. The power storage device 11 also includes an insulator 15 or the like disposed between the plurality of power storage elements 1 and the holding member 13. In this power storage device 11, the technology of the present invention only needs to be applied to at least one power storage element 1.

  The holding member 13 includes a pair of terminal members 131 that sandwich the plurality of power storage elements 1 arranged in the X-axis direction via the adjacent members 12 from both sides in the X-axis direction, and a connecting member 132 that connects the pair of terminal members 131. Have. The holding member 13 holds the plurality of power storage elements 1 such that at least a predetermined region of the electrode body 2 is pressed (pressed) via the case 3 from both sides in the X-axis direction in each power storage element 1. Here, the predetermined region of the electrode body 2 is a region (specifically, the negative electrode 21) including the end of the thin portion (turn portion 234 in the example of the above embodiment) of each folded portion 23 when viewed from the X-axis direction. A region that overlaps the position where the thickness dimension of the folded portion 23 starts to decrease in the long direction, in other words, a turn portion (thin portion) 234 and a thick portion (a portion other than the thin portion in the folded portion 23). (Region including the boundary of) α (see FIG. 14).

  The pressing (squeezing) to the electrode body 2 may be applied by holding the plurality of power storage elements 1 by the holding member 13, and the power storage element 1 with the adjacent member 12 disposed between the power storage elements 1. And the adjacent member 12 may be added by being held together by the holding member 13.

  Even in such a configuration, in the second member 26 sandwiched between the folded portions 23 of the respective negative electrodes 21 of the plurality of power storage elements 1, the end position of the portion pressed (clamped) by the thick portion, That is, a slight level difference is generated at the boundary position between the thick portion and the thin portion of the folded portion 23, thereby effectively suppressing the displacement of the second member 26 between the folded portions 23. .

  DESCRIPTION OF SYMBOLS 1 ... Power storage element, 2 ... Electrode body, 21 ... Negative electrode (electrode), 21A ... Mountain fold line, 21B ... Valley fold line, 210 ... Area | region used as a turn part when folded, 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, 224 ... positive electrode tab, 23 ... folded portion, 23A ... first folded portion, 23B ... second folded , 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 part, 311 ... Closing part, 312 ... Body part, 313 ... Long wall part, 314 ... Short wall part, DESCRIPTION OF SYMBOLS 2 ... Cover plate, 4 ... External terminal, 5 ... Current collector, 6 ... Insulating member, 11 ... Power storage device, 12 ... Adjacent member, 13 ... Holding member, 131 ... Termination member, 132 ... Connecting member, 14 ... Bus bar, DESCRIPTION OF SYMBOLS 15 ... Insulator, 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 ... Elongate object, S ... Swivel axis, α ... Region overlapping with end position of turn part, β ... Separator step, γ ... Gap

Claims (5)

An electrode body having a long first member including a first electrode and a second member including a second electrode having a polarity different from that of the first electrode;
The first member has a first surface and a second surface opposite to the first surface, and a pair of flat portions in which the first surfaces are opposed to each other, and the pair of flat surfaces Having at least one folded part including a turn part connecting the ends of the parts,
The second member is disposed between the pair of flat portions,
The turn portion has a thin-walled portion in which a part of the inner surface of the folded portion is recessed toward the outer surface from other portions,
The electrical storage element in which the clearance gap is formed between this turn part and said 2nd member.   2. The power storage device according to claim 1, wherein an edge of the second member on a turn portion side is located at a position overlapping the thin portion as viewed from a direction in which the pair of flat portions are arranged. A case for accommodating the electrode body;
The electrode body is accommodated in the case in a state where an area overlapping with an end position of the thin portion is pressed from both sides in the direction in which the pair of flat portions are aligned as viewed from the direction in which the pair of flat portions are aligned. The electrical storage element according to claim 2, wherein   The first electrode according to any one of claims 1 to 3, wherein the first electrode includes a metal foil and an active material layer superimposed on an inner surface of the metal foil in a region corresponding to the thin portion. The electricity storage device described. An electrolyte,
A case for accommodating the electrolytic solution and the electrode body,
The first electrode includes the metal foil disposed over the entire region in the longitudinal direction at the folded portion, and the active layer that is overlapped over the entire region in the longitudinal direction of the surface of the metal foil facing the inside of the folded portion. A material layer,
5. The power storage device according to claim 4, wherein a density of a portion corresponding to the thin portion of the active material layer is higher than a density of another portion in the longitudinal direction.