JP2021168284A - Power storage element - Google Patents

Abstract

To provide a power storage element with a wound electrode body, in which deviation in pressure applied to the electrode body is suppressed.SOLUTION: A power storage element comprises: an electrode body 2 in which a positive electrode 23 and a negative electrode 24 are wound around in a state overlapping a belt-like separator 25; and a case which houses the electrode body. A length of the separator in a winding direction is greater than a length of the negative electrode in the winding direction. The electrode body is a wound body having a major axis and a minor axis. A terminal end 234 located on the farthest on a winding-end side of the positive electrode in the winding direction is located further on a winding-start side in the winding direction than a terminal end 244 located on the outermost peripheral side of the negative electrode in the winding direction. In the winding direction, a terminal edge 245 of the negative electrode is located between a position overlapping a terminal edge 235 of the positive electrode and a position P which is opposite across a winding axis to the terminal edge of the positive electrode in the minor axis direction of the electrode body. When viewed from the minor axis direction of the electrode body, a terminal edge 255 located on the outermost peripheral side in the winding direction of the separator is located between the terminal edge of the terminal end of the positive electrode and the terminal edge of the negative electrode.SELECTED DRAWING: Figure 6

Description

The present invention relates to a power storage element provided with a wound electrode body.

Conventionally, a wound electrode body is known as an electrode body used for a secondary battery (see, for example, Patent Document 1). In the electrode body 102, as shown in FIG. 14, a long sheet-shaped positive electrode 123 and a negative electrode 124 are respectively wound so as to be overlapped with each other via two long sheet-shaped separators 126 and 127. .. The electrode body 102 has an elliptical shape having a major axis and a minor axis when viewed from the winding axis direction. Further, the electrode body 102 has R portions located at both ends in the major axis direction.

When the electrode body 102 is viewed from the winding axis direction, the positive electrode winding end portion 1230 and the negative electrode winding end portion 1240 are R portions located on one side of the electrode body 102 on one side in the major axis direction. It is arranged with the. When the electrode body 102 is viewed from the winding axis direction, the separator winding ends 1260 and 1270 are arranged at the other end of the electrode body 102 in the major axis direction.

Japanese Patent No. 6202347

In the electrode body, a step due to these ends may be formed at the positive electrode winding end portion, the negative electrode winding end portion, or the portion where the separator winding end is arranged. As a result, when the electrode body is housed in the case and pressure is applied to the portion of the electrode body in which the step is formed from the outside, the pressure received by the step portion and the portion around the step portion. Can be different. The bias of the pressure applied to the electrode body may deteriorate the battery performance.

Therefore, an object of the present embodiment is to provide a power storage element provided with a wound electrode body and suppressing the bias of the pressure applied to the electrode body.

The power storage element of this embodiment is
An electrode body in which a band-shaped first electrode and a second electrode having different polarities are wound so as to overlap the band-shaped separator,
A case for accommodating the electrode body is provided.
The length of the separator in the winding direction is longer than the length of the second electrode in the winding direction.
The electrode body is a winding body having a major axis and a minor axis when the electrode body is viewed from the winding axis direction.
The end portion of the first electrode located on the most winding end side in the winding direction is located closer to the winding start side in the winding direction than the end portion located on the most winding end side of the second electrode in the winding direction. death,
In the winding direction, the end edge of the end portion of the second electrode is short of the position where it overlaps with the end edge of the end portion of the first electrode and the end edge of the end portion of the first electrode. Located between the position on the opposite side of the winding shaft in the radial direction,
When viewed from the minor axis direction of the electrode body, the terminal edge of the terminal portion located on the winding end side of the separator in the winding direction is the terminal edge of the terminal portion of the first electrode and the terminal edge of the second electrode. It is located between the end edge of the end part.

According to this configuration, the end portion of the separator suppresses the difference in the thickness of the electrode body in the minor axis direction due to the difference in the position of the end portion of each electrode, so that the uniformity of the width of the electrode body is improved. , The bias of the pressure applied to the electrode body can be suppressed.

In the power storage element,
The separator is provided so as to sandwich the first electrode or the second electrode in between.
When the electrode body is viewed from the winding axis direction,
In the winding direction, the end edges of both end portions of the first electrode or the separator sandwiching the second electrode are arranged at the same position on the winding end side of the second electrode. In addition, when viewed from the minor axis direction of the electrode body, it may be located between the terminal edge of the terminal portion of the first electrode and the terminal edge of the terminal portion of the second electrode.

According to such a configuration, both end portions of the separator sandwiching the first electrode and the second electrode sandwich the second electrode, and suppress the difference in the thickness of the electrode body in the minor axis direction due to the difference in the positions of the end portions of the respective electrodes. Can be done.

Further, in the power storage element,
The first electrode and the second electrode each have a sheet-shaped conductive portion and an active material layer that overlaps the conductive portion.
When the electrode body is viewed from the winding axis direction,
The active material layer of the first electrode is arranged at the terminal portion of the first electrode.
The active material layer of the second electrode may be arranged at a portion overlapping the end portion of the first electrode in the winding direction of the second electrode.

In the power storage element,
The second electrode may be arranged outside the first electrode and may be thinner than the first electrode.

According to such a configuration, the difference in the thickness of the electrode body in the minor axis direction due to the difference in the position of the end portion of each electrode tends to be large, so that the effect that the end portion of the separator suppresses this difference in thickness is more remarkable. It will be something like that.

In the power storage element,
When the electrode body is viewed from the winding axis direction,
The end portion of the second electrode and the end portion of the first electrode are arranged on one side in the minor axis direction.
The end portion of the separator may be arranged at a position opposite to the end portion of the second electrode with the winding shaft in the minor axis direction.

According to such a configuration, since the separator extends from the position where it overlaps with the end portion of the second electrode to the opposite side across the winding shaft in the minor axis direction, it is possible to fill the step due to the end portion of the second electrode. ..

According to the power storage element of the present embodiment, it is possible to provide a power storage element provided with a wound electrode body and suppressing the bias of the pressure applied to the electrode body.

FIG. 1 is a perspective view of a power storage element according to the present embodiment. FIG. 2 is a side view of the power storage element. FIG. 3 is a plan view of the power storage element. FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. FIG. 5 is a perspective view for explaining an electrode body of the power storage element. FIG. 6 is a schematic view for explaining the electrode body of the power storage element. FIG. 7 is an enlarged view for explaining the electrode body of the power storage element. FIG. 8 is a schematic diagram for explaining an electrode body of the power storage element according to the comparative example. FIG. 9 is a schematic view for explaining an electrode body of the power storage element according to the comparative example. FIG. 10 is a schematic diagram for explaining an electrode body of the power storage element according to the comparative example. FIG. 11 is a schematic view for explaining the electrode body of the power storage element according to the modified example. FIG. 12 is a schematic view for explaining the electrode body of the power storage element according to the modified example. FIG. 13 is a perspective view of a power storage device including the power storage element. FIG. 14 is a schematic diagram for explaining an electrode body of a conventional power storage element.

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 to 7. In the present embodiment, a rechargeable secondary battery will be described as an example of the power storage element. The name of each component (each component) of the present embodiment is that of the present embodiment, and may be different from the name of each component (each component) in the background technology.

The power storage element of this embodiment is a non-aqueous electrolyte secondary battery. More specifically, the power storage element is a lithium ion secondary battery that utilizes the electron transfer that occurs with the movement of lithium ions. This type of power storage element supplies electrical energy. The power storage element may be used alone or in combination of two or more. Specifically, the power storage element is used alone when the required output and the required voltage are small. On the other hand, when at least one of the required output and the required voltage is large, the power storage element is used in the power storage device in combination with another power storage element. In the power storage device, the power storage element used in the power storage device supplies electrical energy.

As shown in FIGS. 1 to 4, the power storage element includes an electrode body 2 and a case 3 for accommodating the electrode body 2. In addition to the electrode body 2 and the case 3, the power storage element 1 of the present embodiment includes an external terminal 4 arranged outside the case 3 that conducts with the electrode body 2, and the electrode body 2 and the outside. A current collector 5 or the like that conducts the terminal 4 is provided.

As shown in FIG. 5, the electrode body 2 has a structure in which a band-shaped first electrode and a second electrode having different polarities are wound so as to overlap with the band-shaped separator 25. The electrode body 2 of the present embodiment is a laminated body 22 in which a positive electrode 23 as a first electrode and a negative electrode 24 as a second electrode are laminated in a state of being insulated from each other, and is a laminated body 22 and a wound laminated body 22. , Equipped with. In the electrode body 2, the separator 25 is wound around the outer peripheral portion of the electrode body 2. Lithium ions move between the positive electrode 23 and the negative electrode 24 in the electrode body 2, so that the power storage element 1 is charged and discharged.

Further, the electrode body 2 is a winding body having a major axis and a minor axis when the electrode body is viewed from the winding axis direction. The electrode body 2 of the present embodiment has a flat tubular shape. The electrode body 2 has R portions as folded portions at both ends in the major axis direction.

The laminated body 22 is formed by winding the positive electrode 23 and the negative electrode 24 in a laminated (stacked) state. In the laminated body 22, each electrode has a sheet-shaped conductive portion and an active material layer that overlaps the conductive portion.

As shown in FIG. 7, the positive electrode 23 has a metal foil 230 which is a sheet-shaped conductive portion, and a positive electrode active material layer 231 which overlaps the metal foil. The metal foil 230 is strip-shaped. The metal foil 230 of the present embodiment is, for example, an aluminum foil. Further, the positive electrode 23 has a positive electrode uncoated portion (a portion where the positive electrode active material layer 231 is not formed) 232 of the positive electrode active material layer 231 at one edge portion in the width direction, which is the lateral direction of the band shape. (See FIG. 5). The portion of the positive electrode 23 on which the positive electrode active material layer 231 is formed is referred to as a positive electrode coating portion 233.

The positive electrode active material layer 231 has a positive electrode active material and a binder.

The positive electrode active material is, for example, a lithium metal oxide. Specifically, the positive electrode active material, for _{example, Li a Me b O c (} Me represents one or more transition metal) complex oxide represented by _{(Li a Co y O 2,} Li a Ni w _{O 2, Li a Mn z O} 4, Li a Ni w Co y Mn z O 2 , _{etc.), Li l Me m (XO} n) p (Me represents one or more transition metals, X is for example P , Si, B, a polyanion compounds represented by the representative of the _{V) (Li a Fe b PO} 4, Li a Mn b PO 4, Li a Mn b SiO 4, Li a Co b PO 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 231 is, for example, polyvinylidene fluoride (PVdF), a copolymer of ethylene and vinyl alcohol, polymethyl methacrylate, polyethylene oxide, polypropylene oxide, polyvinyl alcohol, polyacrylic acid, poly. It is methacrylic acid and styrene-butadiene rubber (SBR). The binder of this embodiment is polyvinylidene fluoride.

The positive electrode active material layer 231 may further have a conductive auxiliary agent such as Ketjen Black (registered trademark), acetylene black, and graphite. The positive electrode active material layer 231 of the present embodiment has acetylene black as a conductive auxiliary agent.

The negative electrode 24 has a metal foil 240 which is a sheet-shaped conductive portion, and a negative electrode active material layer 241 which overlaps the metal foil 240 (see FIG. 7). The thickness of the negative electrode 24 is substantially the same as the thickness of the positive electrode 23. The metal foil 240 is strip-shaped. The metal foil 240 of the present embodiment is, for example, a copper foil. The negative electrode 24 has a negative electrode uncoated portion (a portion where the negative electrode active material layer is not formed) of the negative electrode active material layer at the edge portion of the positive electrode uncoated portion 232 in the width direction, which is the short side of the band shape. ) 242 (see FIG. 5). The width of the negative electrode coating portion (the portion where the negative electrode active material layer is formed) 243 of the negative electrode 24 is larger than the width of the positive electrode coating portion 233.

The negative electrode active material layer 241 has a negative electrode active material and a binder.

The negative electrode active material may be, for example, a carbon material such as graphite, non-graphitized carbon, and easily graphitized carbon, lithium titanate, or silicon (Si) and tin (Sn) that alloy with lithium ions. It is a material. The negative electrode active material of the present embodiment is non-graphitized carbon.

The binder used for the negative electrode active material layer 241 is the same as the binder used for the positive electrode active material layer 231. The binder of this embodiment is polyvinylidene fluoride.

The negative electrode active material layer 241 may further have a conductive auxiliary agent such as Ketjen Black (registered trademark), acetylene black, and graphite. The negative electrode active material layer 241 of the present embodiment does not have a conductive auxiliary agent.

In the electrode body 2 of the present embodiment, the positive electrode 23 and the negative electrode 24 configured as described above are wound in a state of being insulated by the separator 25. That is, in the electrode body 2 of the present embodiment, the laminated body 22 of the positive electrode 23, the negative electrode 24, and the separator 25 is wound. Further, in the electrode body 2 of the present embodiment, the negative electrode 24 is arranged outside the positive electrode 23. Specifically, the negative electrode 24 is arranged outside the positive electrode 23 in the stacking direction.

The separator 25 is a member having an insulating property. Further, the separator 25 is arranged between the positive electrode 23 and the negative electrode 24. As a result, in the electrode body 2 (specifically, the laminated body 22), the positive electrode 23 and the negative electrode 24 are insulated from each other. Further, the separator 25 holds the electrolytic solution in the case 3. As a result, when the power storage element 1 is charged and discharged, lithium ions move between the positive electrode 23 and the negative electrode 24, which are alternately laminated with the separator 25 in between.

As shown in FIG. 6, the length of the separator 25 in the winding direction is longer than the length of the negative electrode 24 in the winding direction. The separator 25 of the present embodiment is provided so as to sandwich the positive electrode 23 or the negative electrode 24 in between. More specifically, the separator 25 includes a first separator 26 and a second separator 27 that sandwich the positive electrode 23 or the negative electrode 24 in between. The first separator 26 and the second separator 27 are separate bodies.

Further, the separator 25 of the present embodiment is formed of, for example, polyethylene. The hardness of the separator 25 is softer than that of the positive electrode 23 and the negative electrode 24.

The width of the separator (dimension of the strip shape in the lateral direction) is slightly larger than the width of the negative electrode coating portion 243 (see FIG. 5). The separator 25 is arranged between the positive electrode 23 and the negative electrode 24 which are overlapped with each other in a state where the covering portions 233 and 243 are displaced in the width direction so as to overlap each other. At this time, the positive electrode uncoated portion 232 and the negative electrode uncoated portion 242 do not overlap. That is, the positive electrode uncoated portion 232 protrudes in the width direction from the region where the positive electrode 23 and the negative electrode 24 overlap, and the negative electrode uncoated portion 242 extends in the width direction from the overlapping region of the positive electrode 23 and the negative electrode 24 (positive electrode uncoated portion). It protrudes in the direction opposite to the protruding direction of 232). The electrode body 2 is formed by winding the positive electrode 23, the negative electrode 24, and the separator 25 in a laminated state, that is, the laminated body 22.

Further, the separator 25 of the present embodiment has a base material layer 250 and an inorganic layer 251 provided on one surface of the base material layer 250 and harder than the base material layer 250 (see FIG. 7). Further, each base material layer 250 of the pair of separators 25 sandwiching the negative electrode 24 is opposed to the negative electrode 24. Since the base material layer 250 that sandwiches the negative electrode 24 in a state of facing the negative electrode 24 has a shape that conforms to the shape of the negative electrode 24, the insulating property between the positive electrode 23 and the negative electrode 24 can be improved.

The base material layer 250 is composed of, for example, a porous film such as polyethylene, polypropylene, cellulose, or polyamide. The inorganic layer 251 is an _{inorganic layer containing inorganic particles such as SiO 2} particles, Al ₂ O ₃ particles, and boehmite (alumina hydrate).

The case 3 houses the electrode body 2 (see FIG. 4). The case 3 of the present embodiment has a case main body 31 having an opening and a lid plate 32 that closes (closes) the opening of the case main body 31. Further, in the case 3, in addition to the electrode body 2, the electrolytic solution, the current collector 5, and the like are housed in the internal space 33.

Further, the case 3 is formed of a metal having resistance to an electrolytic solution. Case 3 of the present embodiment is formed of, for example, aluminum or an aluminum-based metal material such as an aluminum alloy. The case 3 may be formed of a metal material such as stainless steel and nickel, or a composite material in which a resin such as nylon is adhered to aluminum.

The electrolytic solution is a non-aqueous electrolyte solution. 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 ethyl methyl carbonate. Electrolyte salts are LiClO ₄ , LiBF _{4 , LiPF 6} , and the like.

The case body 31 is a plate-shaped closing portion 311 having a closing portion 311 having an inner surface facing the inside of the case 3 and an outer surface facing the outside of the case 3, and a body portion 312 connected to the peripheral edge of the closing portion 311. It is provided with a tubular body portion 312 extending toward the inner surface side of the closing portion 311 and surrounding the inner surface.

The closing portion 311 is located at the lower end of the case body 31 when the case body 31 is arranged so that the opening faces upward (that is, becomes the bottom wall of the case body 31 when the opening faces upward). ) The part. The closed portion 311 has a rectangular shape in the normal direction of the closed portion 311. The four corners of the closing portion 311 are arcuate.

In the following, as shown in FIG. 1, the long side direction of the closed portion 311 is the X-axis direction, the short side direction of the closed portion 311 is the Y-axis direction, and the normal direction of the closed portion 311 is the Z-axis direction.

The body portion 312 of the present embodiment has a square tubular shape. Specifically, the body portion 312 has a flat square tube shape. The body portion 312 has a pair of long wall portions 313 extending from the long side at the peripheral edge of the closed portion 311 and a pair of short wall portions 314 extending from the short side at the peripheral edge of the closed portion 311. That is, the pair of long wall portions 313 face each other with an interval in the Y-axis direction (specifically, the interval corresponding to the short side at the peripheral edge of the closed portion 311), and the pair of short wall portions 314 are spaced in the X-axis direction. (Specifically, they face each other with an interval corresponding to the long side at the peripheral edge of the closed portion 311). A square tubular body portion 312 is formed by connecting the corresponding (specifically, Y-axis direction) end portions of the short wall portion 314 to each other of the pair of long wall portions 313.

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

The lid plate 32 is a plate-shaped member that closes the opening of the case body 31. Specifically, the lid plate 32 comes into contact with the case body 31 so as to close the opening of the case body 31. The lid plate 32 is a rectangular plate material that is long in the X-axis direction when viewed in the Z-axis direction. Further, the four corners of the lid plate 32 are arcuate.

The lid plate 32 has a gas discharge valve 321 capable of discharging the gas in the case 3 to the outside. The gas discharge valve 321 discharges gas from the inside of the case 3 to the outside when the internal pressure of the case 3 rises to a predetermined pressure. The gas discharge valve 321 of the present embodiment is provided at the center of the lid plate 32 in the X-axis direction.

The external terminal 4 is a portion that is electrically connected to an external device, an external terminal of another power storage element, or the like. The external terminal 4 is formed of a conductive member. For example, the external terminal 4 is formed of steel such as aluminum, copper, iron, stainless steel, chrome molybdenum steel, or other high-strength conductive metal.

The current collector 5 is arranged in the case 3 and is directly or indirectly connected to the electrode body 2 so as to be energized (see FIG. 4).

In the power storage element 1 having the above configuration, the terminal portion 234 located on the most winding end side in the winding direction of the positive electrode 23 is wound more than the terminal portion 244 located on the most winding end side in the winding direction of the negative electrode 24. It is located on the winding start side in the direction (see FIG. 6). Further, in the winding direction, the terminal edge 245 of the terminal portion 244 of the negative electrode 24 overlaps the terminal edge 235 of the terminal portion 234 of the positive electrode 23 and the electrode body 2 with respect to the terminal edge 235 of the terminal portion 234 of the positive electrode 23. In the minor axis direction (Y-axis direction), the position P on the opposite side of the winding axis (from the winding axis of the electrode body to both ends in the major axis direction (Z-axis direction) of the electrode body) Assuming a virtual surface that connects the apex of the R portion) and extends in the winding axis direction (X-axis direction), the position P that is plane symmetric with the terminal edge 235 of the terminal portion 234 of the positive electrode 23 with respect to this virtual surface. ) Is located between. The position overlapping the terminal edge 235 of the terminal portion 234 of the positive electrode 23 is a position overlapping the terminal edge 235 of the positive electrode 23 when viewed from the short side. In the power storage element 1 of the present embodiment, the terminal edge 245 of the negative electrode 24 is located between the position where it overlaps with the terminal edge 235 of the terminal portion 234 of the positive electrode 23 and the folded-back portion (R portion) of the electrode.

Further, the base material layer 250 sandwiching the negative electrode 24 facing the negative electrode 24 has a shape (step) along the step of the electrode due to the end portion 244 of the negative electrode 24, for example, when viewed from the winding axis direction. It has a shape). The sandwiching base material layer 250 has a shape (a shape having a step) along a step between the negative electrode uncoated portion 242 and the negative electrode coated portion 243 when viewed from the minor axis direction (Y-axis direction) of the electrode body 2. It has become.

Further, when viewed from the minor axis direction (Y-axis direction) of the electrode body 2, the end edge 255 of the end portion 254 located on the most winding end side in the winding direction of the separator 25 is the end of the end portion 234 of the positive electrode 23. It is located between the edge 235 and the end edge 245 of the end portion 244 of the negative electrode 24. In the power storage element 1 of the present embodiment, when the electrode body 2 is viewed from the winding axis direction, the terminal edges 255 (specifically, the terminal edges 254 of both end portions 254 of the separator 25 sandwiching the negative electrode 24 in the winding direction). , The terminal edge 265 of the terminal portion 264 of the first separator 26 and the terminal edge 275) of the terminal portion 274 of the second separator 27 are arranged at the same position on the winding end side of the negative electrode 24. When viewed from the minor axis direction (Y-axis direction) of the electrode body 2, it is located between the terminal edge 235 of the positive electrode 23 and the terminal edge 245 of the negative electrode 24.

In the electrode body 2 of the present embodiment, when the electrode body 2 is viewed from the winding axis direction, the positive electrode active material layer 231 is arranged at the terminal portion 234 of the positive electrode 23 (see FIG. 7). Further, when viewed from the winding axis direction, the negative electrode active material layer 241 is arranged at a portion overlapping the terminal portion 234 of the positive electrode 23 in the winding direction of the negative electrode 24.

Further, when the electrode body 2 is viewed from the winding axis direction, the terminal portion 244 of the negative electrode 24 and the terminal portion 234 of the positive electrode 23 are arranged on one side in the minor axis direction (see FIG. 6). Further, when the electrode body 2 is viewed from the winding axis direction, the terminal portion 254 of the separator 25 is arranged on the opposite side of the terminal portion 244 of the negative electrode 24 with the winding shaft in the minor axis direction sandwiched.

In the power storage element 1 of the present embodiment, when the electrode body 2 is viewed from the winding axis direction, the start end edge 257 of the start end portion 256 located on the most winding start side in the winding direction of the separator 25 (specifically, the first The start edge 267 of the start end portion 266 of the separator 26 and the start end edge 277) of the start end portion 276 of the second separator 27 are the start end edge 237 of the start end portion 236 located on the most winding start side in the winding direction of the positive electrode 23, and , The negative electrode 24 is arranged at a position different from that of the start end edge 247 of the start end portion 246 located on the most winding start side in the winding direction. The length of the negative electrode 24 in the winding direction is longer than the length of the positive electrode 23 in the winding direction and shorter than the length of the separator 25 in the winding direction. Therefore, the separator 25 can reliably insulate between the positive electrode 23 and the negative electrode 24.

In the power storage element 1 of the present embodiment, the positive electrode active material layer 231 is arranged in the entire area of the positive electrode 23 in the winding direction. That is, the positive electrode active material layer 231 is arranged in the entire area from the start end portion 236 to the end end portion 234 of the positive electrode 23. Further, the negative electrode active material layer 241 is arranged over the entire area of the negative electrode 24 in the winding direction. That is, the negative electrode active material layer 241 is arranged in the entire area from the start end portion 246 to the end end portion 244 of the negative electrode 24.

In the power storage element 1 of the present embodiment, the amount of change in the thickness of the negative electrode 24 during expansion is ΔT1, and the position of the terminal portion 234 of the positive electrode 23 is in the minor axis direction (Y-axis direction) of the electrode body 2 with respect to the terminal portion 234. When the number of separators arranged on the outside is N and the amount of change in the thickness of the separator 25 during compression is ΔT2, ΔT1 <N × ΔT2. Therefore, the separator 25 can absorb the amount of change in the thickness of the negative electrode 24 located on the outermost side of the electrode body 2 during expansion, and as a result, the current distribution of the electrode body 2 approaches uniform and the output characteristics are improved. ..

The amount of change in the thickness of the separator 25 during compression ΔT2 is calculated by using the compressibility after washing and drying the separator 25 taken out by disassembling the product cell and then performing a creep test to measure the compressibility. Will be done. The amount of change ΔT1 in the thickness of the negative electrode 24 during expansion is the thickness of the negative electrode 24 in the discharged state (SOC = 0%) of the power storage element 1 (product cell) and the negative electrode 24 in the charged state (SOC = 100%) of the product cell. Corresponds to the difference from the thickness of.

The amount of change ΔT1 in the thickness of the negative electrode 24 when expanded is measured as follows, for example, in a configuration in which the negative electrode 24 is located outside the positive electrode 23. After discharging the product cell to a discharged state (SOC = 0%), the product cell is disassembled, the positive electrode 23 and the negative electrode 24 are taken out, and each electrode is washed and dried. Then, the thickness of the negative electrode 24 is measured. Next, a small test cell is prepared using the extracted electrode, and the test cell is charged to a charged state (SOC = 100%). Further, after disassembling the test cell, cleaning and drying each electrode, the thickness of the electrode of the negative electrode 24 is measured, and the difference in the thickness of the negative electrode 24 is defined as the amount of change in the thickness of the negative electrode 24 during expansion ΔT1. The test cell is charged and discharged with the upper limit of the nominal voltage (recommended voltage range for use) of the product cell set to SOC = 100% and the lower limit set to SOC = 0%.

In the conventional electrode body 2, as shown in FIGS. 8 to 10, when the electrode body 2 is viewed from the minor axis direction (Y-axis direction), the terminal edge 255 of the separator 25 is the terminal edge 235 of the positive electrode 23 and the negative electrode. It was not located at any location except between it and the terminal edge 245 of 24. Therefore, in the conventional power storage element, the width of the electrode body 2 varies widely due to the difference in the thickness of the electrode body 2 in the minor axis direction due to the difference in the positions of the terminal portion 234 of the positive electrode 23 and the terminal portion 244 of the negative electrode 24. Therefore, the pressure applied to the electrode body 2 was biased.

On the other hand, according to the power storage element 1, the terminal edge 255 of the separator 25 is located between the terminal edge 235 of the positive electrode 23 and the terminal edge 245 of the negative electrode 24 (see FIG. 6). As a result, the terminal portion 254 of the separator 25 suppresses the difference in the thickness of the electrode body 2 in the minor axis direction due to the difference in the positions of the terminal portion 234 of the positive electrode 23 and the terminal portion 244 of the negative electrode 24, thereby suppressing the difference in the thickness of the electrode body 2. Since the uniformity of the width of the electrode body 2 is improved, the bias of the pressure applied to the electrode body 2 can be suppressed.

Specifically, the thickness of the portion of the electrode body 2 located on the winding end side in the winding direction with respect to the terminal portion 234 of the positive electrode 23 in the minor axis direction (for example, the thickness of the portion indicated by β in FIG. 6) is determined by the electrode. It is thinner by the thickness of the positive electrode 23 than the thickness of the normal portion of the body 2 in the minor axis direction (for example, the thickness of the portion indicated by α in FIG. 6). In the power storage element 1, the terminal portion 254 of the separator 25 fills this difference in thickness, so that the electrode body 2 in the minor axis direction is caused by the difference in the positions of the terminal portion 234 of the positive electrode 23 and the terminal portion 244 of the negative electrode 24. The difference in thickness is suppressed.

According to the power storage element 1 of the present embodiment, both end edges 235 of the separator 25 sandwiching the positive electrode 23 and the negative electrode 24 are arranged outside the negative electrode 24 in the same position and are also electrodes. When viewed from the minor axis direction of the body 2, since it is located between the terminal edge 235 of the positive electrode 23 and the terminal edge 245 of the negative electrode 24, both terminal portions 254 of the separator 25 sandwiching the positive electrode 23 and the negative electrode 24 are , The difference in the thickness of the electrode body 2 in the minor axis direction due to the difference in the positions of the terminal portion 234 of the positive electrode 23 and the terminal portion 244 of the negative electrode 24 can be suppressed.

Further, in the power storage element 1 of the present embodiment, when viewed from the winding axis direction, the terminal portion 244 of the negative electrode 24 and the terminal portion 234 of the positive electrode 23 are arranged on one side in the minor axis direction, and the terminal portion of the separator 25 is arranged. The 254 is arranged at a position opposite to the end portion 244 of the negative electrode 24 with the winding shaft in the radial direction, that is, in the minor axis direction from the position where the separator 25 overlaps the end portion 244 of the negative electrode 24. Since it extends to the opposite side of the winding shaft, it is possible to fill the step due to the terminal portion 244 of the negative electrode 24.

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

For example, when the electrode body 2 is viewed from the winding axis direction, the start end edge 267 of the start end portion 266 of the first separator 26 and the start end edge 277 of the start end portion 276 of the second separator 27 are aligned at the same position. It may be arranged on the winding start side of the start end edge 237 of the positive electrode 23 and the start end edge 247 of the negative electrode 24. Further, in the electrode body 2, the start end edge 237 of the positive electrode 23 and the start end edge 247 of the negative electrode 24 are arranged at different positions when the electrode body 2 is viewed from the winding axis direction. Specifically, the starting edge 247 of the negative electrode 24 is arranged on the winding start side of the positive electrode 23 when the electrode body 2 is viewed from the winding axis direction.

The starting end portion 236 of the positive electrode active material layer 231, the starting end portion 246 of the negative electrode active material layer 241 and the starting end portion 256 of the separator 25 are respectively viewed from the minor axis direction (Y-axis direction) of the electrode body 2. The positions of the start ends are aligned. Further, when viewed from the minor axis direction (Y-axis direction) of the electrode body 2, the positions of the starting end portion of the positive electrode active material layer 231 and the starting end portion of the negative electrode active material layer 241 are aligned.

In this power storage element 1, the terminal portion 234 of the positive electrode 23, the terminal portion 244 of the negative electrode 24, and the terminal portion 254 of the separator 25 are all located on the winding axis side of the center of curvature of the R portion of the electrode body 2. doing. Further, the start end portion 236 of the positive electrode 23, the start end portion 246 of the negative electrode 24, and the start end portion 256 of the separator 25 are all located on the winding axis side of the center of curvature of the R portion of the electrode body 2.

In the above embodiment, the separator 25 is wound around the outer peripheral portion of the electrode body 2, but the separator may be wound around a plurality of times. For example, as shown in FIG. 11, it is conceivable that the separator 25 is wound around the outer peripheral portion of the electrode body 2 twice.

Further, in the above embodiment, the thickness of the positive electrode 23 and the thickness of the negative electrode 24 are substantially the same, but may be different. For example, it is conceivable that the thickness of the negative electrode 24 is thinner than the thickness of the positive electrode 23. In this case, the difference in thickness of the electrode body 2 in the minor axis direction due to the difference in the positions of the terminal portion 234 of the positive electrode 23 and the terminal portion 244 of the negative electrode 24 tends to be large, so that the terminal portion 254 of the separator 25 has this thickness. The effect of suppressing the difference becomes more remarkable.

In the above embodiment, the terminal edge 265 of the first separator 26 and the terminal edge 275 of the second separator 27 are aligned at the same position in the winding direction, but may not be aligned at the same position. In this case, the terminal edge 265 of the first separator 26 or the terminal edge 275 of the second separator 27 may be located between the terminal edge 235 of the positive electrode 23 and the terminal edge 245 of the negative electrode 24.

In the above embodiment, the negative electrode active material layer 241 is arranged in the entire area in the winding direction of the negative electrode 24, but may be arranged in a part of the negative electrode 24 in the winding direction. For example, it is conceivable that the negative electrode active material layer 241 is not arranged at the terminal portion 244 of the negative electrode 24. That is, when viewed from the minor axis direction of the electrode body, the end portion of the negative electrode active material layer 241 in the winding direction may overlap with the end portion of the positive electrode active material layer 231 in the winding direction. In this case, since the thickness of the terminal portion 244 of the negative electrode 24 is thin, the difference in thickness between the terminal portion 234 of the positive electrode 23 and the terminal portion 244 of the negative electrode 24 tends to be large, but this difference can be suppressed by the separator 25.

In the above embodiment, the end edge 245 of the negative electrode 24 has a position where it overlaps with the end edge 235 of the end portion 234 of the positive electrode 23 (a position where it overlaps when viewed from the minor axis direction) and an R portion (a position where the electrode is folded back). Although it was located between them, as shown in FIG. 12, the position opposite to the R portion and the terminal edge 235 of the positive electrode 23 with respect to the winding shaft in the minor axis direction (Y-axis direction) of the electrode body 2. It may be located between and. That is, even if the terminal edge 245 of the negative electrode 24 and the terminal edge 255 of the separator 25 are both located on the opposite sides of the winding shaft of the electrode body 2 in the Y-axis direction with respect to the terminal edge 235 of the positive electrode 23. good.

In the above embodiment, the terminal edge 265 of the first separator 26 and the terminal edge 275 of the second separator 27 are aligned at the same position in the winding direction, but may be arranged at different positions. In this case, only one of the terminal edge 265 of the first separator 26 and the terminal edge 275 of the second separator 27 is the terminal edge 235 of the positive electrode 23 and the terminal of the negative electrode 24 when viewed from the minor axis direction of the electrode body 2. It may be located between the edges 245. The start end edge 267 of the first separator 26 and the start end edge 277 of the second separator 27 are aligned at the same position in the winding direction, but may be arranged at different positions.

In the above embodiment, the first separator 26 and the second separator 27 that sandwich the positive electrode 23 or the negative electrode 24 are separate bodies, but they may be integrated (one continuous separator).

In the above embodiment, in the separator 25, the inorganic layer 251 is provided on one side of the base material layer 250, but the inorganic layer 251 may be provided on both sides of the base material layer 250. The separator 25 does not have to have the inorganic layer 251 and may be composed of only the base material layer 250, for example.

The starting edge 237 of the positive electrode 23 and the starting edge 247 of the negative electrode 24 may be arranged at different positions in the minor axis direction of the electrode body 2.

Further, in the above embodiment, the case where the power storage element is used as a chargeable / dischargeable non-aqueous electrolyte secondary battery (for example, a lithium ion secondary battery) has been described, but the type and size (capacity) of the power storage element are arbitrary. Is. Further, in the above embodiment, the lithium ion secondary battery has been described as an example of the power storage element, but the present invention is not limited to this. For example, the present invention can be applied to various secondary batteries, other primary batteries, and power storage elements of capacitors such as electric double layer capacitors.

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

1 ... power storage element, 2 ... electrode body, 3 ... case, 4 ... external terminal, 5 ... current collector, 11 ... power storage device, 12 ... bus bar member, 22 ... laminate, 23 ... positive electrode, 24 ... negative electrode, 25 ... Separator, 26 ... 1st separator, 27 ... 2nd separator, 31 ... Case body, 32 ... Lid plate, 33 ... Internal space, 102 ... Electrode body, 123 ... Positive electrode, 124 ... Negative electrode, 126 ... Separator, 127 ... Separator, 230 ... metal foil, 231 ... positive electrode active material layer, 232 ... positive electrode uncoated portion, 233 ... positive electrode coating portion, 234 ... terminal portion, 235 ... terminal edge, 236 ... start end portion, 237 ... start end edge, 240 ... metal foil, 241 ... Negative electrode active material layer, 242 ... Negative electrode uncoated portion, 243 ... Negative electrode coating portion, 244 ... Terminal portion, 245 ... Terminal edge, 246 ... Starting end portion, 247 ... Starting end edge, 250 ... Base material layer, 251 ... Inorganic layer , 254 ... Ending part, 255 ... Ending edge, 256 ... Starting end part, 257 ... Starting end edge, 264 ... Ending part, 265 ... Ending edge, 266 ... Starting end part, 267 ... Starting end edge, 274 ... Ending part, 275 ... Ending edge , 276 ... Start end part, 277 ... Start end edge, 311 ... Closure part, 312 ... Body part, 313 ... Long wall part, 314 ... Short wall part, 321 ... Gas discharge valve, 1230 ... Positive electrode winding end part, 1240 ... Negative electrode winding Turning end, 1260, 1270 ... Separator winding end

Claims (5)

An electrode body in which a band-shaped first electrode and a second electrode having different polarities are wound so as to overlap the band-shaped separator,
A case for accommodating the electrode body is provided.
The length of the separator in the winding direction is longer than the length of the second electrode in the winding direction.
The electrode body is a winding body having a major axis and a minor axis when the electrode body is viewed from the winding axis direction.
The end portion of the first electrode located on the most winding end side in the winding direction is located closer to the winding start side in the winding direction than the end portion located on the most winding end side of the second electrode in the winding direction. death,
In the winding direction, the end edge of the end portion of the second electrode is short of the position where it overlaps with the end edge of the end portion of the first electrode and the end edge of the end portion of the first electrode. Located between the position on the opposite side of the winding shaft in the radial direction,
When viewed from the minor axis direction of the electrode body, the terminal edge of the terminal portion located on the winding end side of the separator in the winding direction is the terminal edge of the terminal portion of the first electrode and the terminal edge of the second electrode. Located between the end edge of the end,
A power storage element characterized by this. The separator is provided so as to sandwich the first electrode or the second electrode in between.
When the electrode body is viewed from the winding axis direction,
In the winding direction, the end edges of both end portions of the first electrode or the separator sandwiching the second electrode are arranged at the same position on the winding end side of the second electrode. The storage storage according to claim 1, which is located between the terminal edge of the terminal end of the first electrode and the terminal edge of the terminal end of the second electrode when viewed from the minor axis direction of the electrode body. element. The first electrode and the second electrode each have a sheet-shaped conductive portion and an active material layer that overlaps the conductive portion.
When the electrode body is viewed from the winding axis direction,
The active material layer of the first electrode is arranged at the terminal portion of the first electrode.
The power storage element according to claim 1 or 2, wherein the active material layer of the second electrode is arranged at a portion overlapping the end portion of the first electrode in the winding direction of the second electrode. The power storage element according to any one of claims 1 to 3, wherein the second electrode is arranged outside the first electrode and is thinner than the first electrode. When the electrode body is viewed from the winding axis direction,
The end portion of the second electrode and the end portion of the first electrode are arranged on one side in the minor axis direction.
One of claims 1 to 4, wherein the end portion of the separator is arranged at a position opposite to the end portion of the second electrode so as to sandwich the winding shaft in the minor axis direction. The power storage element according to.

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