POWER STORAGE CELL

The power storage cell includes a wound electrode body, a case, an internal gasket (a seal member), a positive electrode terminal (an external terminal), and a positive electrode connecting portion (a connecting member). The case includes a peripheral wall portion, a lower lid (first lid portion), and an upper lid (second lid portion). The lower lid has an exhaust valve for exhausting the gas in the case. A through hole (second through hole) is formed in the upper lid (second lid). The positive electrode connecting portion includes a columnar portion extending in the Z direction so as to penetrate the through hole of the upper lid and the through hole (first through hole) of the inner gasket. The inner gasket is disposed so as to cover the through hole from the inside of the case.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to Japanese Patent Application No. 2023-139164 filed on Aug. 29, 2023, incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to a power storage cell.

2. Description of Related Art

WO2022/065211 discloses a cylindrical battery provided with a can bottom valve that opens when the internal pressure of an outer can increases.

SUMMARY

In a conventional power storage cell such as that described in WO2022/065211, an exhaust gas may be discharged (leaked) from the side opposite to the side on which the can bottom valve is provided. In this case, the exhaust gas is not efficiently discharged from the can bottom valve (exhaust valve).

The present disclosure has been made in order to address the above issue, and an object thereof is to provide a power storage cell capable of efficiently discharging an exhaust gas from an exhaust valve.

An aspect of the present disclosure provides a power storage cell including:a wound electrode body that includes a first electrode and a second electrode;a case that houses the wound electrode body;a seal member housed in the case and having a first through hole;an external terminal; anda connecting member that electrically connects the external terminal and the first electrode.
The case includesa peripheral wall portion disposed on an outer peripheral side of the wound electrode body and extending in a cylindrical shape along an axial direction of the wound electrode body,a first lid portion that closes one end of the peripheral wall portion in the axial direction, and a second lid portion that closes the other end of the peripheral wall portion in the axial direction.
The first lid portion includes an exhaust valve for discharging a gas in the case.
The second lid portion has a second through hole through which an inside of the case communicates with an outside of the case.
The connecting member includes a columnar portion that extends in the axial direction so as to penetrate the second through hole of the second lid portion and the first through hole of the seal member.
The seal member is disposed so as to cover the second through hole from the inside of the case.

In the power storage cell according to the aspect of the present disclosure, as described above, the first lid portion is provided with the exhaust valve, and the second through hole of the second lid portion is covered by the seal member from the inside of the case. Accordingly, the seal member suppresses the exhaust gas generated from the wound electrode body being leaked from the second lid portion side to the outside of the case. Accordingly, the exhaust gas can be efficiently discharged from the exhaust valve of the first lid portion.

In the power storage cell according to the above aspect, preferably, the connecting member further includes a plate-shaped portion connected to the columnar portion inside the case.

The plate-shaped portion may be disposed so as to extend across the axial direction on a side opposite of the external terminal from the seal member.
With such a configuration, the plate-shaped portion can be easily disposed on the inner side of the case (on the wound electrode body side) with respect to the sealing member. As a result, the plate-shaped portion and the first electrode can be easily electrically connected in the case.

In this case, preferably,the seal member is sandwiched between the second lid portion and the plate-shaped portion in the axial direction.
With such a configuration, it is possible to suppress a gap being formed between the seal member and each of the second lid portion and the plate-shaped portion. As a result, it is possible to suppress the exhaust gas being leaked from the second lid portion side to the outside of the case.

Preferably, the power storage cell according to the above aspect further includesan insulating member disposed so as to cover the second through hole of the second lid portion from the outside of the case.
The second lid portion may be electrically connected to the second electrode.
The insulating member may be configured tohave a third through hole through which the columnar portion penetrates, andbe disposed so as to insulate the second lid portion and the external terminal.
With such a configuration, the second through hole is covered by the insulating member, and thus it is possible to suppress the exhaust gas being leaked from the second through hole to the outside of the case. In addition, since the third through hole is provided in the insulating member, the columnar portion can be introduced into the inside of the case while the insulating member is insulating the second lid portion and the external terminal.

In this case,a thickness of the seal member in the axial direction may be greater than a thickness of the insulating member in the axial direction.
With such a configuration, the gap (space) in the case can be easily filled by the seal member compared to when the thickness of the seal member is equal to or less than the thickness of the insulating member. As a result, it is possible to suppress the exhaust gas being leaked from the seal member side to the outside of the case.

According to the present disclosure, an exhaust gas can be efficiently discharged from an exhaust valve provided in a case of a power storage cell.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof will not be repeated.

The power storage cell100includes a wound electrode body1, a case2, a positive electrode terminal3, a positive electrode connecting portion4, an external gasket5, an internal gasket6, and a negative electrode current collector plate7. Each of the external gasket5and the internal gasket6has an insulating property. The positive electrode terminal3and the internal gasket6are examples of the “external terminal” and the “seal member” of the present disclosure, respectively. The external gasket5and the positive electrode connecting portion4are examples of the “insulating member” and the “connecting member” of the present disclosure, respectively.

The wound electrode body1is accommodated in the case2. The case2includes an upper lid2a, a lower lid2b, and a peripheral wall portion2c. The peripheral wall portion2cis disposed on the outer periphery of the wound electrode body1. The peripheral wall portion2cextends in a cylindrical shape along the axial direction (Z direction) of the wound electrode body1. That is, the case2has a cylindrical shape. The wound electrode body1is wound so as to have a cylindrical shape in the same manner as the case2. That is, the power storage cell100is a cylindrical battery. The case2is made of copper, aluminum, or the like. Further, the upper lid2aand the lower lid2bare exemplary of the “second lid portion” and the “first lid portion”, respectively. The Z direction is an example of the “axial direction” of the present disclosure.

The upper lid2acloses the opening2kon Z1side of the peripheral wall portion2c. Specifically, the outer peripheral edge2eof the upper lid2ais welded to Z1end2dof the peripheral wall portion2c. The welded portion2fbetween the upper lid2aand the peripheral wall portion2c(see the hatched portion inFIG.2) is formed in an annular shape along the outer peripheral edge2e. The welded portion2fis formed, for example, by irradiating the laser from Z1toward a part of the upper lid2a(the vicinity of the outer peripheral edge2e) corresponding to the end2d. InFIG.1, the welded portion2fis omitted for the sake of simplicity. In addition, the opening2kis an exemplary “other end” of the present disclosure.

The upper lid2ahas a through hole2gthat communicates the inside and the outside of the case2. The through hole2gis formed in the center of the upper lid2a. The through hole2ghas a circular shape when viewed from Z1(seeFIG.2). The through hole2ghas a length L1(seeFIG.2). Note that the through hole2gis an exemplary “second through hole” disclosed herein.

The lower lid2bcloses Z2opening2lof the peripheral wall portion2c. Specifically, the outer peripheral edge2iof the lower lid2bis welded to Z2end2hof the peripheral wall portion2c. Thus, the welded portion2jbetween the lower lid2band the peripheral wall portion2c(see the hatched portion inFIG.3) is formed in an annular shape along the outer peripheral edge2i. The welded portion2jis formed, for example, by irradiating the laser from Z2toward a part of the lower lid2b(the vicinity of the outer peripheral edge2i) corresponding to the end2h. InFIG.1, the welded portion2jis omitted for the sake of simplicity. In addition, the opening2lis an exemplary “one end” of the present disclosure.

The lower lid2bhas an exhaust valve8for exhausting the gases in the case2. The exhaust valve8is configured to discharge gas from the case2when the internal pressure of the case2becomes equal to or higher than a predetermined threshold value. The exhaust valve8is provided at the center of the lower lid2b(seeFIG.3).

The wound electrode body1includes a positive electrode sheet10, a negative electrode sheet20, and a separator30. The separator30is provided between the positive electrode sheet10and the negative electrode sheet20. The separator30separates the positive electrode sheet10and the negative electrode sheet20from each other while allowing ions (for example, lithium ions) to move back and forth between the positive electrode sheet10(positive electrode active material) and the negative electrode sheet20(negative electrode active material). The wound electrode body1includes an electrode plate group in which a positive electrode sheet10and a negative electrode sheet20are wound with a separator30interposed therebetween. The positive electrode sheet10and the negative electrode sheet20are examples of the “first electrode” and the “second electrode” of the present disclosure, respectively.

As shown inFIG.4, the wound electrode body1is wound such that the positive electrode sheet10, the negative electrode sheet20, and the separator30surround the winding axis a. The wound electrode body1is formed by winding an electrode sheet in which the negative electrode sheet20, the separator30, the positive electrode sheet10, and the separator30are stacked in this order from the outer peripheral side around the winding axis a. InFIG.4, a state in which the winding of the wound electrode body1is slightly unwound is illustrated so that the winding state of the wound electrode body1can be easily understood.

Referring again toFIG.1, the positive electrode terminal3is exposed by being provided outside the case2. The positive electrode terminal3is made of aluminum. The positive electrode terminal3is provided on Z1face of the external gasket5disposed on the upper lid2aof the case2.

The positive electrode connecting portion4includes a columnar portion4aand a positive electrode current collector plate4b. The columnar portion4ais connected to the positive electrode terminal3. The columnar portion4ais provided so as to extend along the Z-direction. The columnar portion4aconnects the positive electrode terminal3and the positive electrode current collector plate4b. The columnar portion4aextends from the positive electrode terminal3to the inside of the case2through the through hole2gof the upper lid2a. Note that the positive electrode current collector plate4bis an exemplary “plate-shaped portion” disclosed herein.

The positive electrode current collector plate4bis accommodated in the case2. The positive electrode current collector plate4bis welded to Z2end4cof the columnar portion4a.

The positive electrode current collector plate4bis disposed so as to intersect (orthogonally) the positive electrode terminal3with respect to the internal gasket6in the Z-direction on the other side (Z2side). Specifically, the positive electrode current collector plate4bis disposed so as to be in close contact with Z2face of the internal gasket6.

The external gasket5is provided outside the case2. Specifically, the external gasket5is sandwiched between the positive electrode terminal3and the upper lid2aof the case2. Thus, the positive electrode terminal3and the case2(upper lid2a) are insulated from each other.

A through hole5a(seeFIG.7) is formed in the external gasket5. The columnar portion4aextends from the positive electrode terminal3to the positive electrode current collector plate4bthrough the through hole5a. The through hole5ais an exemplary “third through hole” of the present disclosure.

The internal gasket6is provided inside the case2. Specifically, the internal gasket6is disposed between the upper lid2aof the case2and the positive electrode current collector plate4b. Thus, the upper lid2aof the case2and the positive electrode current collector plate4bare insulated from each other.

A through hole6ais formed in the internal gasket6. The through hole6ais provided at the center of the internal gasket6when viewed along the Z-direction. The columnar portion4aextends from the positive electrode terminal3to the positive electrode current collector plate4bthrough the through hole6a.

The internal gasket6also includes a protrusion6b. The protrusion6bprotrudes Z2from the outer peripheral edge of the internal gasket6. The protrusion6bis provided so as to shield the positive electrode current collector plate4band the peripheral wall portion2c. Thus, the positive electrode current collector plate4band the peripheral wall portion2care insulated from each other. The through hole6ais an exemplary “first through-hole” of the present disclosure.

The negative electrode current collector plate7is housed in the case2. The negative electrode current collector plate7is welded to a negative electrode uncoated portion21b, which will be described later, of the negative electrode sheet20. The negative electrode current collector plate7contacts the lower lid2bof the case2.

A through hole7ais formed in the negative electrode current collector plate7. The through hole7ais provided at a position overlapping the exhaust valve8in the Z-direction. As a result, the exhaust gases can be easily guided to the exhaust valve8through the through hole7a.

FIG.5is a plan view of the positive electrode current collector plate4b. The positive electrode current collector plate4bhas a disk-shape. The positive electrode current collector plate4bincludes a central portion4c, a spoke4d, an outer peripheral edge portion4e, and a piece portion4f.

The central portion4cis provided at the center of the positive electrode current collector plate4b. The columnar portion4ais joined to the central portion4c. The spoke4dis provided so as to extend radially outward from the central portion4c. Six spokes4dare provided at equal angular intervals around the central portion4cof the positive electrode current collector plate4b.

The outer peripheral edge portion4eis provided on the outer peripheral edge of the positive electrode current collector plate4b. Each of the six spokes4dconnects the outer peripheral edge portion4eand the central portion4c. The spoke4dis formed to bend in the Z-direction. The central portion4cof the positive electrode current collector plate4bis largest in the Z-direction.

Through holes4gare formed between circumferentially adjacent spokes4d. That is, six through holes4gare formed. A piece portion4fis provided inside each of the six through hole4g. Each of the six piece portions4fis connected to the outer peripheral edge portion4eby the connecting portion4h. Each of the six piece portions4fis welded to the positive electrode current collector plate4b. Note that each of the six piece portions4fhas a tapered shape toward the radially inner side.

FIG.6is a plan view of the negative electrode current collector plate7. The negative electrode current collector plate7has a disk shape. The negative electrode current collector plate7includes a central portion7b, a spoke7c, an outer peripheral edge portion7d, and a piece portion7c.

The central portion7bis provided at the center of the negative electrode current collector plate7. The spoke7cis provided so as to extend radially outward from the central portion7b. The through hole7ais provided in the central portion7b. Six spoke7care provided at equal angular intervals around the central portion7bof the negative electrode current collector plate7.

The outer peripheral edge portion7dis provided on the outer peripheral edge of the negative electrode current collector plate7. Each of the six spoke7cconnects the outer peripheral edge portion7dand the central portion7b. The spoke7care formed so as to bend in the Z-direction. The outer peripheral edge portion7dof the negative electrode current collector plate7largest moves (displaces) in the Z-direction.

Through holes7fare formed between circumferentially adjacent spoked7c. That is, six through holes7fare formed. A piece portion7eis provided inside each of the six through hole7f. Each of the six piece portions7eis connected to the outer peripheral edge portion7dby the connecting portion7g. Each of the six piece portions7eis welded to the negative electrode current collector plate7. Note that each of the six piece portions7ehas a tapered shape toward the radially inner side.

As illustrated inFIG.7, the positive electrode sheet10includes a positive electrode current collector11and a positive electrode mixture layer12. The positive electrode current collector11includes a positive electrode coated portion11aand a positive electrode uncoated portion11b. The positive electrode coated portion11ais a portion of the positive electrode current collector11on which the positive electrode mixture layers12are coated. The positive electrode uncoated portion11bis a portion (exposed portion) of the positive electrode current collector11on which the positive electrode mixture layers12are not coated. The positive electrode mixture layers12are coated on both surfaces of the positive electrode coated portion11ain the radial direction (R direction).

The positive electrode uncoated portion11bis located Z1the positive electrode coated portion11a. Specifically, the positive electrode uncoated portion11bprotrudes Z1from the positive electrode coated portion11a. The positive electrode mixture layer12is in close contact with the separator30.

The positive electrode current collector11is made of, for example, aluminum. The positive electrode mixture layer12is formed by coating a positive electrode slurry on the surface of the positive electrode current collector11and drying the slurry. The positive electrode slurry is a slurry prepared by kneading a material (a positive electrode active material, a binder, or the like) of the positive electrode mixture layer12and a solvent. The positive electrode mixture layer12is in close contact with the separator30. The thickness t12of the positive electrode mixture layers12is, for example, 0.1 μm or more and 1000 μm or less.

The positive electrode uncoated portion11bis bent radially inward by being in contact with the positive electrode current collector plate4bdisposed on Z1side. The positive electrode current collector plate4bis positively charged by being contacted with the positive electrode uncoated portion11b. The positive electrode uncoated portion11bis welded to the positive electrode current collector plate4b. As a result, the positive electrode current collector plate4bis positively charged. In addition, the positive electrode terminal3electrically connected to the positive electrode current collector plate4bby the columnar portion4ais positively charged. That is, the positive electrode terminal3and the positive electrode sheet10are electrically connected by the positive electrode connecting portion4.

As illustrated inFIG.8, the negative electrode sheet20includes a negative electrode current collector21and a negative electrode mixture layer22. The negative electrode current collector21includes a negative electrode coated portion21aand a negative electrode uncoated portion21b. The negative electrode coated portion21ais a portion of the negative electrode current collector21on which the negative electrode mixture layers22are coated. The negative electrode uncoated portion21bis a portion (exposed portion) of the negative electrode current collector21on which the negative electrode mixture layers22are not coated. The negative electrode mixture layers22are coated on both surfaces of the negative electrode coated portion21ain the radial direction (R direction).

The negative electrode uncoated portion21bis located Z2the negative electrode coated portion21a. Specifically, the negative electrode uncoated portion21bprotrudes Z2from the negative electrode coated portion21a. The negative electrode mixture layer22is in close contact with the separator30.

The negative electrode current collector21is made of, for example, copper. The negative electrode mixture layer22is formed by coating a negative electrode slurry on the surface of the negative electrode current collector21and drying the negative electrode slurry. The negative electrode slurry is a slurry prepared by kneading a material (a negative electrode active material, a binder, or the like) of the negative electrode mixture layer22and a solvent. The thickness t22of the negative electrode mixture layers22is, for example, 0.1 μm or more and 1000 μm or less.

The negative electrode uncoated portion21bis bent radially inward by being brought into contact with the negative electrode current collector plate7disposed Z2. The negative electrode current collector plate7is negatively charged by contacting the negative electrode uncoated portion21b. As a result, the lower lid2bcontacting the negative electrode current collector plate7is negatively charged. That is, the negative electrode current collector plate7electrically connects the negative electrode sheet20and the lower lid2bof the case2. Further, since the lower lid2b, the peripheral wall portion2c, and the upper lid2aare electrically connected to each other, each of the peripheral wall portion2cand the upper lid2ais negatively charged.

Here, in the conventional power storage cell, the exhaust gas is discharged (leaked) from the side opposite to the side where the exhaust valve is provided, so that the exhaust gas may not be efficiently discharged from the exhaust valve.

Therefore, in the present embodiment, as shown inFIG.7, the internal gasket6is disposed so as to cover the through hole2gfrom the inside of the case2. Specifically, the internal gasket6is disposed so as to fill a gap S (seeFIG.2) formed between the through hole2gand the columnar portion4awhen viewed from Z1.

The columnar portion4amay be press-fitted into the through hole6aof the internal gasket6. That is, the outer peripheral surface of the columnar portion4aand the inner peripheral surface of the through hole6amay be in close contact with each other. Accordingly, since the columnar portion4aplugs the through hole6a, it is possible to suppress the exhaust gases from being discharged to the outside of the case2through the through hole6a.

Further, although not shown, the internal gasket6has a disk shape when viewed along the Z direction. The internal gasket6has a length L2(seeFIG.1). Further, the through hole6aof the internal gasket6has a circular shape (seeFIG.2) as viewed along the Z-direction. The through hole6ahas a length L3. The through hole5aof the external gasket5has the same configuration as the through hole6a. That is, the through hole5ahas a length L3.

The internal gasket6is sandwiched between the upper lid2aand the positive electrode current collector plate4bin the Z-direction. That is, the internal gasket6is provided such that the surface of the internal gasket6on Z2side is in close contact with the positive electrode current collector plate4bas described above, and the surface of the internal gasket6on Z1side is in close contact with the upper lid2a. That is, no gap is formed between the internal gasket6and the positive electrode current collector plate4band between the internal gasket6and the upper lid2a.

The internal gasket6may be formed of a resin or the like having elasticity. The internal gasket6may be elastically deformed by being pressed by the upper lid2aand the positive electrode current collector plate4bin the Z-direction.

The internal gasket6has a thickness t1in the Z-direction. The external gasket5has a thickness t2in the Z-direction. The minimum value of the thickness t1of the internal gasket6is larger than the maximum value of the thickness t2of the external gasket5. Further, the minimum value of the thickness t1of the internal gasket6is larger than the maximum value of the thickness t3of the upper lid2ain the Z-direction.

The external gasket5is disposed so as to cover the through hole2gof the upper lid2afrom the outer side of the case2. Specifically, the external gasket5is disposed so as to fill a gap S (seeFIG.9) formed between the through hole2gand the columnar portion4awhen viewed from Z2.

The columnar portion4amay be press-fitted into the through hole5aof the external gasket5. That is, the outer peripheral surface of the columnar portion4aand the inner peripheral surface of the through hole5amay be in close contact with each other. Accordingly, since the columnar portion4aplugs the through hole5a, it is possible to suppress the exhaust gases from being discharged to the outside of the case2through the through hole5a.

The external gasket5has a disk shape. The external gasket5has a length L4. The length L4is larger than the length L1of the through hole2gof the upper lid2a.

As described above, in the present embodiment, the internal gasket6is disposed so as to cover the through hole2gon the upper lid2afrom the inside of the case2. Accordingly, since the through hole2gis blocked by the internal gasket6inside the case2, it is possible to suppress the exhaust gas leaking from the through hole2gto the outside of the case2. As a result, the exhaust gas can be efficiently discharged from the exhaust valve8.

In addition, as compared with cases where a case is formed by drawing a metallic plate or the like, the case2is formed using the upper lid2aand the lower lid2b, whereby the manufacturing process and the manufacturing device of the case2can be simplified.

In the above embodiment, the internal gasket6is sandwiched between the upper lid2aand the positive electrode current collector plate4bin the Z-direction. For example, a slight gap may be formed between the internal gasket6and the upper lid2a.

In the above embodiment, the thickness t1of the internal gasket6in the Z direction is larger than the thickness t2of the external gasket5in the Z direction. The thickness t1may be less than or equal to the thickness t2.

In the above embodiment, an example has been described in which the internal gasket (seal member) is provided in close contact with the positive electrode current collector plate (plate-like portion), but the present disclosure is not limited thereto. The inner gasket (seal member) may be provided in close contact with the negative electrode current collector plate (plate-like portion).

In the above embodiment, the upper lid2aand the peripheral wall portion2cand the lower lid2band the peripheral wall portion2care welded to each other. At least one of the above may be connected by crimping.

The embodiments disclosed herein are to be considered in all respects as illustrative and not restrictive. It is intended that the scope of the disclosure be defined by the appended claims rather than the description of the embodiments described above, and that all changes within the meaning and range of equivalency of the claims be embraced therein.