JP7352857B2 - Energy storage element - Google Patents

Description

The present invention relates to a power storage element including a plurality of wound electrode bodies.

2. Description of the Related Art Conventionally, a secondary battery including a plurality of wound electrode assemblies has been known (see Patent Document 1). Specifically, the secondary battery includes a plurality of electrode assemblies, a case, and a cap assembly.

Each electrode assembly can be formed by stacking and winding a first electrode plate 510, a separator 530, and a second electrode plate 520 formed in a thin plate shape or membrane shape as shown in FIG.

The first electrode plate 510 includes a foil-shaped first electrode current collector 511 and a first electrode active material layer 512 coated on both sides of the first electrode current collector 511 . Further, the first electrode current collector 511 is formed with a first electrode uncoated portion 511a that is not coated with the first electrode active material layer. Further, the second electrode plate 520 includes a foil-shaped second electrode current collector 521 and a second electrode active material layer 522 coated on both surfaces of the second electrode current collector 521. Further, the second electrode current collector 521 is formed with a second electrode uncoated portion 521a that is not coated with the second electrode active material layer. Furthermore, the separator 530 is interposed between the first electrode plate 510 and the second electrode plate 520, and is made of a film that prevents short circuits and only allows movement of lithium ions.

As shown in FIGS. 15 and 16, the first electrode assembly 541 has a first electrode uncoated portion 511a and a first electrode uncoated portion 511a on one side of the first electrode assembly 541 and the other side opposite to the one side. It is formed by arranging and winding the first electrode plate 510, separator 530, and second electrode plate 520 so that the two-electrode uncoated portion 521a protrudes. The second electrode assembly 542 and the third electrode assembly 543 have the same configuration as the first electrode assembly 541.

The first electrode assembly 541, the second electrode assembly 542, and the third electrode assembly 543 are arranged adjacent to each other in one direction, that is, in parallel, and fixed together by a fixing tape.

The case 550 includes a bottom portion 551 and a side wall portion 552 extending from the bottom portion 551 to accommodate the electrolyte and the plurality of electrode assemblies 541 to 543. Then, the upper part of the case 550 is opened so that the plurality of electrode assemblies 541 to 543 can pass therethrough.

A plurality of electrode assemblies 541 to 543 are inserted into the interior of the case 550 through the open upper part of the case 550, and after the electrolyte and the like are injected into the interior of the case 550, the open upper part of the case 550 is covered with a cap assembly 560 and sealed, thereby forming a secondary battery 500.

In recent years, it has been desired to improve the energy density within the case 550 even in a secondary battery including a plurality of wound electrode assemblies 541 to 543 as described above.

Japanese Patent Application Publication No. 2011-77026

Therefore, an object of the present embodiment is to provide a power storage element that has a plurality of wound electrode bodies and has improved energy density.

The electricity storage element of this embodiment is
a plurality of electrode bodies wound with electrodes each having a conductive layer and an active material layer stacked on the conductive layer;
a case accommodating the plurality of electrode bodies in a lined state and with adjacent electrode bodies in close contact with each other;
The outermost peripheral part of the electrode in at least one of the adjacent electrode bodies has an outer unformed part without the active material layer on the outer surface of the conductive layer,
The outer unformed portion is arranged at least in a region that is in close contact with an adjacent electrode body.

According to this configuration, since the outer unformed part without an active material layer is arranged on the outer surface of the conductive layer in a region that is in close contact with the adjacent electrode body, the active material layer (for charging and discharging) is disposed on the outer surface of the conductive layer. Compared to the case where there is a non-contributing active material layer), the electrode bodies can be arranged closer to each other by the amount of the active material layer, thereby improving the energy density within the case.

The electricity storage element is
an external terminal attached to the case or constituted by at least a portion of the case;
Each of the electrodes of the adjacent electrode bodies has at least one electrically conductive connection piece extending from the conductive layer to the external terminal,
The at least one connection piece of each of the adjacent electrode bodies is bundled so as to be electrically conductive with each other,
The adjacent electrode bodies may each have the outer unformed portion where the outer surface of the conductive layer is exposed, and the outer surfaces of the conductive layer may be brought into direct contact with each other.

According to this configuration, the connecting pieces that connect the electrodes of each electrode body and the external terminal are also bundled so that they are conductive to each other while adjacent electrode bodies are electrically connected to each other, so that the energy balance of each electrode body is maintained. At the same time, resistance between the external terminal and the wound electrode (specifically, the wound portion of the electrode excluding the connection piece in the electrode body) is suppressed.

Further, in the electricity storage element,
The electrode body is
a pair of flat parts facing each other across the winding center of the electrode body;
a pair of curved parts connecting the ends of the pair of flat parts and facing each other across the winding center,
The innermost peripheral part of the electrode has an inner unformed part without an active material layer on the inner surface of the conductive layer,
The inner unformed portion may be arranged at the curved portion.

According to this configuration, since there is no active material layer on the inner surface of the electrode at the innermost circumference where the curvature at the curved portion is greatest, cracking of the active material layer in the electrode body can be suitably prevented.

Further, in the electricity storage element,
The electrode includes a positive electrode and a negative electrode,
The active material layer includes a positive electrode active material layer and a negative electrode active material layer,
In the positive electrode, the positive electrode active material layer is stacked on both sides of the conductive layer,
In the negative electrode, the negative electrode active material layer is stacked on both sides of the conductive layer,
The inner unformed portion may be arranged at least at the innermost peripheral portion of the positive electrode.

According to this configuration, the active material is placed in the area where the active material layer is most likely to break in the wound electrode body (i.e., on the inner surface of the conductive layer at the innermost circumference where the curvature at the curved part of the positive electrode is the largest). By not disposing the layer, cracking of the active material layer in the electrode body can be effectively prevented.

In the electricity storage element,
In the positive electrode curved portion included in the curved portion of the positive electrode, the positive electrode active material layer may be present on the outer surface of the conductive layer, and the positive electrode active material layer may not be present on the inner surface of the conductive layer.

At the curved part, the positive electrode active material layer overlaid on the outer surface of the positive electrode conductive layer becomes smaller than the negative electrode active material layer overlaid on the inner surface of the negative electrode conductive layer disposed outside thereof (circumferential length). However, the positive electrode active material layer stacked on the inner surface of the positive electrode conductive layer is larger than the negative electrode active material layer stacked on the outer surface of the negative electrode conductive layer disposed inside the positive electrode active material layer ( (The circumferential length becomes larger). Therefore, as in such a configuration, electrodeposition occurs due to the fact that the positive electrode active material layer becomes larger than the negative electrode active material layer due to the absence of the positive electrode active material layer on the inner surface of the conductive layer of the positive electrode at the curved portion. can be suppressed.

As described above, according to the present embodiment, it is possible to provide a power storage element that has a plurality of wound electrode bodies and has improved energy density.

FIG. 1 is a perspective view of a power storage element according to this embodiment. FIG. 2 is an exploded perspective view of the power storage element. FIG. 3 is a sectional view taken along line III-III in FIG. FIG. 4 is a perspective view of the electrode body. FIG. 5 is a diagram for explaining the configuration of the electrode body. FIG. 6 is a diagram for explaining a positive electrode, a negative electrode, and a separator. FIG. 7 is a schematic cross-sectional view for explaining the positive electrode, the negative electrode, and the separator. FIG. 8 is a diagram for explaining an electrode body according to another embodiment. FIG. 9 is a schematic diagram for explaining an electrode body according to another embodiment. FIG. 10 is a schematic diagram for explaining an electrode body according to another embodiment. FIG. 11 is a schematic diagram for explaining an electrode body according to another embodiment. FIG. 12 is a schematic diagram for explaining an electrode body according to another embodiment. FIG. 13 is a schematic diagram of a power storage device including the power storage element. FIG. 14 is a diagram showing a stacked state of a first electrode plate, a separator, and a second electrode plate that constitute a conventional electrode assembly. FIG. 15 is a perspective view showing a state in which a plurality of the electrode assemblies are lined up. FIG. 16 is a cross-sectional view of a conventional secondary battery.

Hereinafter, one embodiment of a power storage element according to the present invention will be described with reference to FIGS. 1 to 7. Power storage elements include primary batteries, secondary batteries, capacitors, and the like. In this embodiment, a chargeable and 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 in this embodiment, and may differ from the name of each component (each component) in background art.

The electricity storage element of this embodiment is a non-aqueous electrolyte secondary battery. More specifically, the power storage element is a lithium ion secondary battery that utilizes electron transfer that occurs with the movement of lithium ions. This type of storage element supplies electrical energy. A single power storage element or a plurality of power storage elements are used. Specifically, a single power storage element is used when the required output and 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 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 electrical energy.

As shown in FIGS. 1 to 3, the power storage element includes a plurality of electrode bodies 2 (five in this embodiment) around which electrodes are wound, and a plurality of electrode bodies 2 arranged in a line and adjacent to each other. A case 3 that accommodates the electrode bodies 2 in close contact with each other is provided. The power storage element 1 also includes an external terminal 4 that is attached to the case 3 with at least a portion exposed or configured by at least a portion of the case 3, and a current collector that connects the electrode body 2 and the external terminal 4. An insulating member 6 and the like arranged between the body 5, the plurality of electrode bodies 2, and the case 3 are also provided. The external terminal 4 of this embodiment is attached to the case 3.

Each of the plurality of electrode bodies 2 is configured by winding an electrode 20 having a conductive layer 211 and an active material layer 212 overlaid on the conductive layer 211, as shown in FIGS. 4 and 5. . In each electrode body 2 of this embodiment, the electrode 20 is wound to form a flat wound body. That is, each electrode body 2 has a pair of flat parts 2F facing each other with the winding center C of the electrode body 2 in between, and a pair of flat parts 2F connecting the ends of the pair of flat parts 2F and facing each other with the winding center C in between. It has a pair of curved parts 2C. Below, the direction in which the winding center C extends is defined as the X-axis of the orthogonal coordinate system, the direction in which the pair of flat parts 2F face each other is defined as the Y-axis of the orthogonal coordinate system, and the direction in which the pair of curved parts 2C face each other is defined as the orthogonal coordinate system. Let it be the Z axis of

In the electrode body 2 of this embodiment, the dimension in the X-axis direction is 60 to 90 mm, the dimension in the Y-axis direction is 3 to 7 mm, and the dimension in the Z-axis direction is 100 to 150 mm.

In these plurality of electrode bodies 2, the outermost peripheral portion α ₀ (see FIGS. 6 and 7) of the electrode 20 in at least one of the adjacent electrode bodies 2 is active on the outer surface of the conductive layer 211. It has an outer unformed portion 213 without the material layer 212. In the electricity storage element 1 of this embodiment, the electrode 20 of each electrode body 2 has an outer unformed portion 213 at the outermost circumferential portion α ₀ . This outer unformed portion 213 is arranged in a region of the outermost peripheral portion α ₀ of the electrode 20 that is in close contact with at least the adjacent electrode body 2 . The outer unformed portion 213 of this embodiment is provided throughout the outermost circumferential portion _α0 .

The electrode 20 has at least one connecting piece 22 that extends from the conductive layer 211 to the external terminal 4 and has conductivity. Specifically, the electrode 20 includes a strip-shaped electrode main body 21 and a connecting piece 22 extending from one end of the electrode main body 21 in the longitudinal direction. This electrode 20 includes a positive electrode 23 and a negative electrode 24. The lithium ions move between the positive electrode 23 and the negative electrode 24, thereby charging and discharging the electricity storage element 1. The specific configurations of the positive electrode 23 and the negative electrode 24 are as follows.

The positive electrode 23 includes a metal foil 231 and a positive electrode active material layer 232 overlaid on the metal foil 231. The metal foil 231 has a strip-shaped foil main body 2311 that is the conductive layer 211 of the positive electrode 23, and a rectangular positive electrode connection piece 2312 extending from one end of the foil main body 2311 in the longitudinal direction. The positive electrode connection piece 2312 of this embodiment extends from one end of the foil main body 2311 in the longitudinal direction and one end in the width direction. The metal foil 231 of this embodiment is, for example, aluminum foil.

In this positive electrode 23, positive electrode active material layers 232 are stacked on both sides of a foil body 2311, and these foil bodies 2311 and two positive electrode active material layers 232 stacked on both sides of the foil body 2311 are the positive electrode body of the positive electrode 23. 230 (electrode body 21) (see FIG. 6).

Specifically, in the positive electrode main body 230, the surface facing outward in the rolled state of the foil main body 2311 (i.e., the surface facing the opposite side to the winding center C side in the electrode body 2: the outer surface) 2311A, the outermost peripheral portion A positive electrode active material layer 232 is stacked over the entire area except _α1 . In the positive electrode body 230, on the surface 2311B of the foil body 2311 facing inward in the wound state (i.e., the surface facing the winding center C side of the electrode body 2: the inner surface), the flat portion of the electrode body 2 is A positive electrode active material layer 232 is stacked on each of the parts corresponding to 2F, and there is no positive electrode active material layer 232 in each part (positive electrode curved part) corresponding to the curved part 2C. That is, on the inner surface 2311B of the foil body 2311, the positive electrode active material layer 232 is intermittently coated in the longitudinal direction (see FIG. 7).

The positive electrode active material layer 232 of this embodiment is made of a compound capable of intercalating and deintercalating lithium ions, such as lithium cobalt oxide or a nickel cobalt manganese ternary active material. Further, the length of the positive electrode main body 230 (dimension in the long direction) is 1000 to 3000 mm, the width (dimension in the short direction) is 100 to 140 mm, and the thickness is 0.1 to 0.3 mm. .

Further, the positive electrode main body 230 has an outer unformed portion 2301 in which the positive electrode active material layer 232 is not formed on the outer surface 2311A of the positive electrode main body 230 at the outermost peripheral portion _α1 (see FIGS. 4 and 7). In the electrode body 2 of this embodiment, since the positive electrode 23 is located at the outermost periphery, the outer unformed portion 2301 of the positive electrode 23 constitutes the outer unformed portion 213 of the electrode body 2. That is, in the electrode body 2 of this embodiment, the outer unformed portion 2301 of the positive electrode 23 is provided throughout the outermost circumferential portion α ₁ of the positive electrode 23 .

In the positive electrode 23 described above, the portion of the electrode 20 that corresponds to the electrode body 21 is the positive electrode body 230, and the portion of the electrode 20 that corresponds to the connection piece 22 is the positive electrode connection piece 2312.

The negative electrode 24 includes a metal foil 241 and a negative electrode active material layer 242 overlaid on the metal foil 241. The metal foil 241 has a strip-shaped foil main body 2411 that is a conductive layer of the negative electrode 24, and a rectangular negative electrode connection piece 2412 extending from one end of the foil main body 2411 in the longitudinal direction. The negative electrode connection piece 2412 of this embodiment extends from the other end in the width direction (the end opposite to the part where the positive electrode connection piece 2312 extends) at one end in the longitudinal direction of the foil main body 2411. There is. The metal foil 241 of this embodiment is, for example, copper foil.

In this negative electrode 24, negative electrode active material layers 242 are stacked on both sides of the foil body 2411, and these foil bodies 2411 and the two negative electrode active material layers 242 stacked on both sides of the foil body 2411 are the negative electrode body of the negative electrode 24. 240 (electrode body 21) (see FIG. 6).

The negative electrode active material layer 242 of this embodiment is made of a compound capable of intercalating and deintercalating lithium ions, such as graphite and amorphous carbon. Further, the length (long dimension) of the negative electrode main body 240 is 1000 to 3000 mm, the width (short dimension) is 100 to 150 mm, and the thickness is 0.1 to 0.3 mm. .

In the electrode body 2 of the present embodiment, the innermost circumferential portion β ₂ of the negative electrode 24 is located inside the innermost circumferential portion β ₁ of the positive electrode 23 . That is, in the electrode body 2 of this embodiment, the innermost circumferential portion β ₀ of the electrode 20 constituting the electrode body 2 is constituted by the innermost circumferential portion β ₂ of the negative electrode 24 .

In each electrode body 2 of the present embodiment, the positive electrode 23 and the negative electrode 24 configured as described above are wound while being insulated by a separator 25. That is, in each electrode body 2 of this embodiment, the positive electrode 23, the negative electrode 24, and the separator 25 are wound in a laminated state. Note that the separator 25 is not arranged on the outermost periphery of each electrode body 2.

The separator 25 is an insulating member and is disposed between the positive electrode 23 and the negative electrode 24. Thereby, in the electrode body 2, the positive electrode 23 and the negative electrode 24 are insulated from each other. Furthermore, the separator 25 holds the electrolyte within the case 3. This allows lithium ions to move between positive electrodes 23 and negative electrodes 24 that are alternately stacked with separators 25 in between when charging and discharging electricity storage element 1 . Further, the width direction (short side direction) dimension of the separator 25 is larger than the width direction dimensions of the positive electrode 23 and the negative electrode 24 .

This separator 25 has a band shape and is made of, for example, a porous membrane of polyethylene, polypropylene, cellulose, polyamide, or the like. The separator 25 of this embodiment includes an inorganic layer containing inorganic particles such as ₂ SiO particles, ₃ Al ₂ O particles, and boehmite (alumina hydrate) on a base material formed of a porous membrane. It is formed of. The base material of the separator 25 of this embodiment is formed of polyethylene, for example.

As shown in FIGS. 2 and 3, the plurality of electrode bodies 2 each configured as described above are arranged in the Y-axis direction so that the flat portions 2F face each other. At this time, the outer unformed portions 213 (2301) of adjacent electrode bodies 2 are brought into close contact (in contact) with each other. That is, the metal foils 231 (more specifically, the foil bodies 2311) of the positive electrodes 23 of adjacent electrode bodies 2 are brought into contact with each other. Thereby, the positive electrodes 23 of adjacent electrode bodies 2 are electrically connected to each other.

The position of the positive electrode connection piece 2312 in each electrode body 2 in the X-axis direction is the same. Further, the position of the negative electrode connecting piece 2412 in each electrode body 2 in the X-axis direction is the same. Therefore, when a plurality of electrode bodies 2 are lined up in the Y-axis direction so that the flat parts 2F face each other, the positive electrode connection pieces 2312 of each electrode body 2 are lined up in the Y-axis direction, and the negative electrode connection pieces 2412 are also lined up in the Y-axis direction. Arranged in the Y-axis direction. The positive electrode connection pieces 2312 of the plurality of electrode bodies 2 are bundled so as to be electrically conductive with each other, and connected to the external terminal 4 via the current collector 5. Further, the respective negative electrode connecting pieces 2412 of the plurality of electrode bodies 2 are also bundled so as to be electrically conductive with each other, and are connected to the external terminal 4 via the current collector 5 (see FIG. 3). The bundle of positive electrode connection pieces 2312 and the bundle of negative electrode connection pieces 2412 of this embodiment are connected to the current collector 5 by welding.

As shown in FIGS. 1 to 3, the case 3 includes a case body 31 having an opening, and a lid plate 32 that covers (closes) the opening of the case body 31. This case 3 is made of metal that is resistant to electrolyte. The case 3 of this embodiment is made of, for example, aluminum or an aluminum-based metal material such as an aluminum alloy.

The electrolyte is a non-aqueous electrolyte. The electrolytic solution is obtained by dissolving an electrolyte salt in an organic solvent. The organic solvent is, for example, cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethylmethyl carbonate. Electrolyte salts include LiClO ₄ , LiBF ₄ , and LiPF ₆ . The electrolytic solution of this embodiment is a mixed solvent of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate adjusted in a ratio of ethylene carbonate: dimethyl carbonate: ethyl methyl carbonate = 3:2:5, and 1 mol/L of LiPF6 _. is dissolved.

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

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

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 long sides at the periphery of the closing portion 311 and a pair of short wall portions 314 extending from short sides at the periphery of the closing portion 311 . That is, the pair of long walls 313 face each other with an interval in the Y-axis direction (specifically, the interval corresponding to the short side of the periphery of the closing part 311), and the pair of short walls 314 face each other with an interval in the X-axis direction. (More specifically, they face each other with an interval corresponding to the long side of the periphery of the closing portion 311). The rectangular cylindrical body 312 is formed by connecting the short wall portions 314 to the corresponding (more specifically, opposing in the Y-axis direction) ends of the pair of long wall portions 313.

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

In Case 3 of this embodiment, the inner dimension in the X-axis direction is 120 to 150 mm, the inner dimension in the Y-axis direction is 20 to 25 mm, and the inner dimension in the Z-axis direction is 80 to 90 mm.

In the case 3 configured in this way, a plurality of electrode bodies 2 are provided, each of the flat portions 2F of each electrode body 2 being parallel (substantially parallel) to the long wall portion 313, and a pair of curved portions of each electrode body 2. The portion 2C is housed in a state covered with the insulating member 6 so as to face the closing portion 311 and the cover plate 32 (see FIGS. 2 and 3). At this time, the case 3 accommodates the plurality of electrode bodies 2 in a state where the plurality of electrode bodies 2 are entirely compressed (pressed) in the Y-axis direction.

The cover plate 32 is a plate-shaped member that closes the opening of the case body 31. The lid plate 32 of this embodiment is a rectangular plate member that is long in the X-axis direction when viewed from the Z-axis direction. The peripheral edge of the lid plate 32 overlaps the opening peripheral edge 34 of the case body 31 so as to close the opening of the case body 31. With the opening peripheral portion 34 and the cover plate 32 superimposed, the boundary between the cover plate 32 and the case body 31 is welded, thereby forming the case 3.

The external terminal 4 is a part that is 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. For example, the external terminal 4 is formed of a metal material with high weldability, such as an aluminum-based metal material such as aluminum or an aluminum alloy, or a copper-based metal material such as copper or a copper alloy.

The insulating member 6 is arranged between the case 3 (specifically, the case body 31) and the plurality of electrode bodies 2. The insulating member 6 is formed into a bag shape as shown in FIG. 2 by folding an insulating sheet-like member cut into a predetermined shape.

According to the above power storage element 1, the outer unformed portion 213 where the active material layer 212 is not formed on the outer surface of the conductive layer 211 in a region that is in close contact with the adjacent electrode body 2 (in the example of this embodiment, the outer unformed portion 213 of the foil body 2311 Since the outer unformed portion 2301) without the positive electrode active material layer 232 is disposed on the outer surface 2311A (see FIG. 4), the active material layer 202 (active material layer that does not contribute to charging and discharging) is disposed on the outer surface. Compared to a certain case, it is possible to arrange a plurality of electrode bodies 2 as many as the number of active material layers 212. Thereby, the energy density within the case 3 can be improved.

Furthermore, in the power storage element 1 of this embodiment, the energy density within the case 3 is improved by accommodating five wound-type electrode bodies 2 with a small number of turns in the case 3. Specifically, it is as follows.

In a wound-type electrode body that is constructed by winding an electrode with a connecting piece extending from the longitudinal end, current can only be collected from the longitudinal end (connecting piece) of the electrode. However, due to resistance problems, it has been difficult to put an electrode body with a large number of turns into practical use. That is, a large power storage element (for example, a square with a size of about 90 mm x 150 mm x 25 mm) is equipped with a wound-type electrode body formed by winding an electrode with a connecting piece extending from the end in the longitudinal direction. It has been difficult to put this type of energy storage device into practical use.

However, like the electricity storage element 1 of this embodiment, by arranging a plurality of electrode bodies 2 with a small number of turns (for example, about 10 turns) in the case 3, when collecting current in each electrode body 2, This makes it possible to increase the size of the power storage element 1.

In addition, in a power storage element equipped with a wound-type electrode body formed by winding an electrode with a connecting piece extending from the end in the longitudinal direction, the electrode with the maximum energy density (theoretical value) The number of fields (maximum value) can be determined by calculation. In the power storage element 1 of this embodiment, the energy density in the case 3 is maximum when five electrode bodies 2 are housed in the case 3.

Furthermore, in the power storage element 1 of the present embodiment, the respective connection pieces 22 (positive electrode connection piece 2312, negative electrode connection piece 2412) of adjacent electrode bodies 2 are bundled so as to be electrically conductive with each other, and The outer surfaces of the conductive layers 211 of the outer unformed portion 213 (in the example of this embodiment, the outer surfaces 2311A of the foil bodies 2311 of the outer unformed portion 2301) are brought into direct contact with each other. In this way, in the power storage element 1 of this embodiment, the electrode bodies 230, 240 and the external Since the connecting pieces 2312 and 2412 that conduct electricity with the terminal 4 are also bundled together so that they are electrically conductive with each other, the energy balance of each electrode body 2 is achieved, and the resistance between the external terminal 4 and the electrode bodies 230 and 240 is reduced. It can be suppressed.

Generally, in the power storage element 1, when the electrode 20 is bent, the positive electrode active material layer 232 is more likely to break than the negative electrode active material layer 242. Therefore, in the positive electrode 23 of this embodiment, the inner unformed portion 2313 is arranged in a region corresponding to the curved portion 2C of the innermost peripheral portion _β1 of the positive electrode 23. In this way, in the wound type electrode body 2, the conductive layer ₂₁₁ (foil By not disposing the positive electrode active material layer 232 on the inner surface 2311B of the main body 2311), cracking of the active material layer 212 (the positive electrode active material layer 232 and the negative electrode active material layer 242) in the electrode body 2 can be effectively prevented. It will be done.

In the wound electrode body 2, in the curved portion 2C, the positive electrode active material layer 232 superimposed on the outer surface 2311A of the conductive layer 211 (foil main body 2311) of the positive electrode 23 is a conductive layer of the negative electrode 24 disposed outside of the positive electrode active material layer 232. It is smaller (the length dimension in the circumferential direction is smaller) than the negative electrode active material layer 242 overlaid on the inner surface of the layer 211 (foil main body 2411). On the other hand, the positive electrode active material layer 232 stacked on the inner surface 2311B of the conductive layer 211 (foil body 2311) of the positive electrode 23 is stacked on the outer surface of the conductive layer 211 (foil body 2411) of the negative electrode 24 disposed inside thereof. It is larger than the overlapping negative electrode active material layer 242 (the length in the circumferential direction is larger). Therefore, in the electrode body 2 of this embodiment, the positive electrode active material layer 232 is not arranged on the inner surface 2311B of the foil main body 2311 in each of the portions corresponding to the curved portions 2C (positive electrode curved portions). The occurrence of electrodeposition caused by the positive electrode active material layer 232 being larger than the negative electrode active material layer 242 is suppressed.

Note that the power storage element of the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention. For example, the configuration of another embodiment can be added to the configuration of one embodiment, and a part of the configuration of one embodiment can be replaced with the configuration of another embodiment. Additionally, some of the configurations of certain embodiments may be deleted.

In the electrode body 2 of the above embodiment, the outermost circumferential portion α ₁ of the positive electrode 23 constitutes the outermost circumferential portion α ₀ of the electrode 20 in the electrode body 2, and the innermost circumferential portion β ₀ of the electrode 20 in the electrode body 2 constitutes the negative electrode 24. (see FIG. ₇ ), but the structure is not limited to this. For example, the outermost circumferential portion α ₀ of the electrode 20 in the electrode body 2 may be constituted by the outermost circumferential portion α ₂ of the negative electrode 24 . Furthermore, the innermost circumferential portion β ₁ of the positive electrode 23 may constitute the innermost circumferential portion β ₀ of the electrode 20 in the electrode body 2 .

The electrode body ₂ of the above embodiment has an active material layer 212 (negative _electrode active material layer 242 ) (that is, there is no inner non-formed portion where the active material layer 212 is not formed on the inner surface of the conductive layer 211), but the structure is not limited to this. The electrode body 2 may have the inner unformed portion at the innermost peripheral portion _β0 . In this case, it is preferable that the inner unformed portion is provided in an area corresponding to at least the curved portion 2C in the innermost peripheral portion _β0 . According to this configuration, since there is no active material layer 212 on the inner surface of the electrode 20 at the innermost circumference where the curvature at the curved portion 2C is largest in the electrode body 2, cracks in the active material layer 212 in the electrode body 2 are prevented. Suitably prevented.

In the power storage element 1 of the embodiment described above, each electrode body 2 is housed in the case 3 with the winding center C along the X-axis direction (the direction in which the short wall portions 314 face each other in the case 3). Not limited to configuration. For example, as shown in FIG. 8, each electrode body 2A may be housed in the case 3 with the winding center C along the Z-axis direction (the direction in which the closing part 311 and the cover plate 32 face each other in the case 3). good.

In the plurality of electrode bodies 2A shown in FIG. 8, the positive electrode connecting piece 2312 extends in the Z-axis direction (width direction) from the long side (end in the width direction) of the positive electrode main body 230 (foil main body 2311), and the negative electrode connecting piece 2412 extends in the Z-axis direction (width direction) from the long side (end portion in the width direction) of the negative electrode body 240 (foil body 2411). In this case, a plurality of positive electrode connection pieces 2312 extend from one positive electrode main body 230, and these plurality of positive electrode connection pieces 2312 are lined up in the Y-axis direction. Further, a plurality of negative electrode connection pieces 2412 extend from one negative electrode main body 240, and these plurality of negative electrode connection pieces 2412 are lined up in the Y-axis direction. That is, in each electrode body 2 of the above embodiment, one connection piece 22 extends from one electrode 20, but the configuration is not limited to this, and as in the example shown in FIG. The connecting piece 22 may be extended.

Further, the electrode body 2 of the above embodiment and the electrode body shown in FIG. 8 may be housed in the case 3 in a mixed state. That is, the winding centers C of the plurality of electrode bodies do not all have to face the same direction.

Further, in the power storage element 1 of the above embodiment, the separator 25 is not arranged on the outermost periphery of the electrode body 2, but the structure is not limited to this. A separator 25 may be arranged at the outermost periphery of the electrode body 2. In this case, as shown in FIG. 9, the separator 25 may be arranged around the entire outermost periphery of each electrode body 2 in the energy storage element 1, or as shown in FIG. The electrode body 2 in which the separator 25 is disposed and the electrode body 2 in which the separator 25 is not disposed on the outermost periphery (the electrode body 2 of the above embodiment) may coexist.

Furthermore, as shown in FIG. 11, the separator 25 disposed on the outermost periphery of the electrode body 2 is disposed on a part of the outermost periphery of the electrode body 2 (in the example shown in FIG. 11, a half area in the circumferential direction). You can leave it there. In this case, it is preferable that the separator 25 of at least one electrode body 2 is located in a region where adjacent electrode bodies 2 are in contact with each other. With this configuration, it is possible to prevent the metal foils 231, 241, etc. from breaking when adjacent electrode bodies 2 are displaced from each other within the case 3.

Further, in the electrode body 2, the separators 25 are arranged to sandwich the electrode 20, and the separators 25 on both sides of the electrode 20 extend from the outer peripheral end 20A of the electrode 20 (electrode body 21), and the separators 25 in the separators 25 The portions extending from the outer circumferential end portion 20A of 20 (portions shown in smoke in FIG. 12) may be connected to each other. As a result, even if the separator 25 contracts in the longitudinal direction (circumferential direction) due to heat or the like, the outer circumferential end 20A of the electrode 20 is not exposed (that is, it is covered by the separator 25), so that the outer circumference of the electrode 20 Short circuits caused by the side end portion 20A coming into contact with other parts can be reliably prevented. Note that the extending portions of the separator 25 may be connected to each other by a known method such as adhesion or welding.

Furthermore, 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 can be changed arbitrarily. It is. Further, in the above embodiment, a 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 is applicable to various secondary batteries, other primary batteries, and power storage elements of capacitors such as electric double layer capacitors.

A power storage element (for example, a battery) 1 may be used in a power storage device (a battery module if the power storage element is a battery) 11 as shown in FIG. 13 . Power storage device 11 includes at least two power storage elements 1 and a bus bar member 12 that electrically connects the two (different) power storage elements 1 to each other. In this case, the technology of the present invention only needs to be applied to at least one power storage element 1.

DESCRIPTION OF SYMBOLS 1... Electricity storage element, 2, 2A... Electrode body, 2C... Curved part, 2F... Flat part, 20... Electrode, 20A... Outer peripheral side end of electrode, 21... Electrode body, 211... Conductive layer, 212... Active material layer , 213... Outer unformed part, 22... Connection piece, 23... Positive electrode (electrode), 230... Positive electrode main body, 2301... Outer unformed part, 231... Metal foil, 2311... Foil main body (conductive layer), 2311A... Outer surface , 2311B...Inner surface, 2312...Positive electrode connection piece, 2313...Inner unformed part, 232...Positive electrode active material layer (active material layer), 24...Negative electrode (electrode), 240...Negative electrode main body, 241...Metal foil, 2411... Foil body (conductive layer), 2412... Negative electrode connection piece, 242... Negative electrode active material layer (active material layer), 25... Separator, 3... Case, 30... Housing part, 31... Case body, 311... Closure part, 312 ...Body part, 313...Long wall part, 314...Short wall part, 32...Lid plate, 34...Opening peripheral part, 4...External terminal, 41...Surface, 5...Current collector, 6...Insulating member, 11...Power storage device , 12... Bus bar member, 500... Secondary battery, 510... First electrode plate, 511... First electrode current collector, 511a... First electrode uncoated part, 512... First electrode active material layer, 520... Second electrode Plate, 521... Second electrode current collector, 521a... Second electrode uncoated portion, 522... Second electrode active material layer, 530... Separator, 541... First electrode assembly, 542... Second electrode assembly, 543... Third electrode assembly, 550... Case, 551... Bottom, 552... Side wall, 560... Cap assembly, C... Winding center, _α0 , _α1 , _α2 ... Outermost circumferential portion, _β0 , _β1 , β ₂ ... Innermost circumferential part

Claims (5)

a plurality of electrode bodies wound with electrodes each having a conductive layer and an active material layer stacked on the conductive layer;
a case accommodating the plurality of electrode bodies in a lined state and with adjacent electrode bodies in close contact with each other;
an external terminal attached to the case or constituted by at least a portion of the case,
The outermost peripheral part of the electrode in at least one of the adjacent electrode bodies has an outer unformed part without the active material layer on the outer surface of the conductive layer,
The outer unformed portion is arranged at least in a region that is in close contact with an adjacent electrode body,
The electrode has a band-shaped electrode body, and a connection piece extending from one longitudinal end of the electrode body in the same direction as the electrode body,
The connection piece is a power storage element electrically connected to the external terminal . Each of the electrodes of the adjacent electrode bodies has at least one electrically conductive connection piece extending from the conductive layer to the external terminal,
The at least one connection piece of each of the adjacent electrode bodies is bundled so as to be electrically conductive with each other,
The power storage element according to claim 1, wherein the adjacent electrode bodies each have the outer non-formed portion where the outer surface of the conductive layer is exposed, and the outer surfaces of the conductive layer are brought into direct contact with each other. The electrode body is
a pair of flat parts facing each other across the winding center of the electrode body;
a pair of curved parts connecting the ends of the pair of flat parts and facing each other across the winding center,
The innermost peripheral part of the electrode has an inner unformed part without an active material layer on the inner surface of the conductive layer,
The power storage element according to claim 1 or 2, wherein the inner unformed portion is arranged in the curved portion. The electrode includes a positive electrode and a negative electrode,
The active material layer includes a positive electrode active material layer and a negative electrode active material layer,
In the positive electrode, the positive electrode active material layer is stacked on both sides of the conductive layer,
In the negative electrode, the negative electrode active material layer is stacked on both sides of the conductive layer,
The electricity storage element according to claim 3, wherein the inner unformed portion is arranged at least at the innermost circumferential portion of the positive electrode. 4 . The positive electrode curved portion included in the curved portion of the positive electrode has the positive electrode active material layer on the outer surface of the conductive layer and does not have the positive electrode active material layer on the inner surface of the conductive layer. The energy storage element described in .