JP7813673B2 - Battery cell - Google Patents

Description

The present invention relates to a battery cell.

In recent years, various battery cell structures, such as lithium-ion secondary battery cells, have been developed. For example, the battery cell described in Patent Document 1 comprises a battery element, two lid materials, and an exterior film. The two lid materials cover both longitudinal ends of the battery element. A tab electrically connected to the battery element extends from each lid material. The exterior film is wrapped around the battery element in the longitudinal direction.

JP 2011-108623 A

For example, in the battery cell described in Patent Document 1, wrinkles can form in the exterior film due to distortion of the exterior film's shape. However, if wrinkles in the exterior film are present around the battery element of the exterior film, the wrinkles can be transferred to the battery element. This can affect the characteristics of the battery cell.

One object of the present invention is to stabilize the characteristics of a battery cell. Other objects of the present invention will become apparent from the description herein.

One aspect of the present invention is as follows.
[1]
A battery element;
a tab electrically connected to the battery element via a current collector aggregate portion drawn out from the battery element;
a cover material that covers one end of the battery element and through which the tab is pulled out;
an exterior film at least partially wrapped around the battery element;
Equipped with
a wrinkle in the exterior film is present around the gathering portion of the current collector in the exterior film.
[2]
The battery cell according to [1], wherein the size of the lid member is larger than the size of the battery element when viewed from the pull-out direction of the tab.
[3]
The battery cell according to [1], wherein the size of the lid member is smaller than the size of the battery element when viewed from the pull-out direction of the tab.

The above-described aspects of the present invention make it possible to stabilize the characteristics of the battery cell.

FIG. 2 is a front perspective view of a battery cell according to the embodiment. FIG. 2 is an enlarged front perspective view of a portion of a battery cell according to an embodiment. FIG. 2 is a right side view of the battery cell according to the embodiment. 4 is a schematic cross-sectional view taken along the line AA in FIG. 3. 5A to 5C are diagrams for explaining a first example of a method for manufacturing a battery cell according to an embodiment. 10A to 10C are diagrams for explaining a second example of a method for manufacturing a battery cell according to an embodiment. FIG. 10 is a front perspective view of a battery cell according to a modified example.

Embodiments and variations of the present invention will be described below with reference to the drawings. In all drawings, similar components will be designated by similar reference numerals, and descriptions will be omitted where appropriate.

Figure 1 is a front perspective view of a battery cell 10 according to an embodiment. Figure 2 is an enlarged front perspective view of a portion of the battery cell 10 according to an embodiment. Figure 3 is a right side view of the battery cell 10 according to an embodiment. Figure 4 is a schematic cross-sectional view taken along line A-A in Figure 3. For the sake of explanation, Figure 3 shows the exterior film 300 in a see-through state.

For the purpose of explanation, each figure is labeled with the X, Y, and Z directions. The X direction indicates the front-to-rear direction of the battery cell 10. The Y direction is perpendicular to the X direction. The Y direction indicates the left-to-right direction of the battery cell 10. The Z direction is perpendicular to both the X and Y directions. The Z direction indicates the up-to-down direction of the battery cell 10. The direction indicated by the arrow indicating the X direction, the direction indicated by the arrow indicating the Y direction, and the direction indicated by the arrow indicating the Z direction are the rearward, leftward, and upward directions, respectively. However, the relationships between the X direction, Y direction, Z direction, front-to-rear direction, left-to-right direction, and up-to-down direction of the battery cell 10 are not limited to this example.

Note that the white circle with an X indicating the X, Y, or Z direction indicates that the direction from the front to the back of the paper is the direction indicated by the arrow indicating that direction.

The battery cell 10 comprises a battery element 100, a positive electrode tab 110, a negative electrode tab 120, a front cover material 210, a rear cover material 220, and an exterior film 300. The exterior film 300 has a wound portion 302 and a pulled-out portion 304.

The battery element 100 has a substantially rectangular parallelepiped shape. The longitudinal direction of the battery element 100 is substantially parallel to the X direction. The length of the battery element 100 in the X direction is not limited to, but is, for example, 300 mm or more and 500 mm or less, and preferably 450 mm or less. The lateral direction of the battery element 100 is substantially parallel to the Z direction. The length of the battery element 100 in the Z direction is not limited to, but is, for example, 90 mm or more and 130 mm or less, and preferably 120 mm or less. The thickness direction of the battery element 100 is substantially parallel to the Y direction. The thickness of the battery element 100 in the Y direction is not limited to, but is, for example, 20 mm or more and 50 mm or less, and preferably 45 mm or less. However, the shape of the battery element 100 is not limited to this example.

The battery element 100 includes at least one positive electrode (not shown), at least one negative electrode (not shown), and at least one separator (not shown). For example, multiple positive electrodes and multiple negative electrodes are stacked alternately in the Y direction. At least a portion of the separator is located between adjacent positive electrodes and negative electrodes in the Y direction. For example, multiple sheet-like separators may each be located between adjacent positive electrodes and negative electrodes in the Y direction. Alternatively, a single sheet-like separator may have a zigzag shape that passes through the area between adjacent positive electrodes and negative electrodes in the Y direction. Alternatively, the positive electrode, negative electrode, and separator may be wound so that the separator is located between the positive electrode and negative electrode. In one example, the positive electrode, negative electrode, and separator are wound with both surfaces of one of the positive and negative electrodes covered by the separator. In another example, a stack including multiple unit stacks each including a positive electrode, a separator, and a negative electrode in this order may be wound. However, the winding structure of the positive electrode, negative electrode, and separator is not limited to these examples.

As shown in FIG. 3, the positive electrode tab 110 is disposed in front of the battery element 100. The rear end of the positive electrode tab 110 is electrically connected to the positive electrode current collector 102a. The positive electrode current collector 102a is pulled forward from the positive electrode 102. This electrically connects the positive electrode tab 110 to multiple positive electrodes 102. As shown in FIG. 4, multiple positive electrode current collectors 102a are aggregated between the battery element 100 and the front cover member 210. In other words, a grouping of multiple positive electrode current collectors 102a exists between the battery element 100 and the positive electrode tab 110. The Y-direction width of the grouping of multiple positive electrode current collectors 102a narrows as it moves forward from the battery element 100. Note that in FIG. 4, the multiple positive electrode current collectors 102a pulled out from the battery element 100 and aggregated are schematically illustrated as a triangular shape.

As shown in FIG. 3, the negative electrode tab 120 is disposed at the rear of the battery element 100. The front end of the negative electrode tab 120 is electrically connected to the negative electrode current collector 104a. The negative electrode current collector 104a is pulled out rearward from the negative electrode 104. This allows the negative electrode tab 120 to be electrically connected to multiple negative electrodes 104. As in the example shown in FIG. 4, a grouping of multiple negative electrode current collectors 104a exists between the battery element 100 and the negative electrode tab 120.

The front cover member 210 covers the front end of the battery element 100. The front cover member 210 is made of, for example, resin, metal, etc. The front end of the positive electrode tab 110 extends forward from the front surface of the front cover member 210. When viewed from the front, the front cover member 210 has a substantially rectangular shape. When viewed from the front, the longitudinal direction of the front cover member 210 is substantially parallel to the Z direction, and the lateral direction of the front cover member 210 is substantially parallel to the Y direction.

The rear lid member 220 covers the rear end of the battery element 100. The rear lid member 220 is made of, for example, resin, metal, etc. The rear end of the negative electrode tab 120 extends rearward from the rear surface of the rear lid member 220. When viewed from the rear, the rear lid member 220 has a substantially rectangular shape. When viewed from the rear, the longitudinal direction of the rear lid member 220 is substantially parallel to the Z direction, and the lateral direction of the rear lid member 220 is substantially parallel to the Y direction.

As shown in Figures 1 and 2, the wound portion 302 has a generally cylindrical shape that opens both forward and backward. The front lid member 210 is disposed inside the front opening of the wound portion 302. The rear lid member 220 is disposed inside the rear opening of the wound portion 302. The wound portion 302 is wrapped around the battery element 100, front lid member 210, and rear lid member 220 in the X direction once. As a result, the front lid member 210, rear lid member 220, and wound portion 302 form a storage space 500 that stores the battery element 100. The storage space 500 contains the battery element 100 as well as an electrolyte (not shown). Note that the manner in which the wound portion 302 wraps around the battery element 100 is not limited to the example described above.

The outer peripheral surface of the front lid member 210 in the X direction and the inner peripheral surface of the front opening of the wrapping portion 302 in the X direction are joined to each other, for example, by heat fusion. This forms the front sealing portion 510.

The outer peripheral surface of the rear lid member 220 in the X direction and the inner peripheral surface of the rear opening of the wrapped portion 302 in the X direction are joined to each other, for example, by heat fusion. This forms the rear sealing portion 520.

1 and 2, when viewed from the front, the pull-out portion 304 is pulled out from the upper left corner of the battery element 100 of the wound portion 302. Specifically, as shown in FIG. 2, the pull-out portion 304 includes a first pull-out portion 304a and a second pull-out portion 304b. The first pull-out portion 304a is pulled out from one of the circumferential ends of the wound portion 302 in the X direction. The second pull-out portion 304b is pulled out from the other circumferential end of the wound portion 302 in the X direction. The first pull-out portion 304a and the second pull-out portion 304b are joined to each other by, for example, heat sealing. This forms a side sealing portion 530 when viewed from the front. The pull-out portion 304 is folded along the top surface of the battery element 100. However, the pull-out portion 304 does not have to be folded. Furthermore, the folding shape of the drawer portion 304 is not limited to the shape described in the embodiment.

As shown in FIG. 3, the exterior film 300 has a front portion 310, a rear portion 320, and a central portion 330. The front portion 310 is located around the X-direction periphery of the aggregated portion of the positive electrode current collector 102a. The rear portion 320 is located around the X-direction periphery of the aggregated portion of the negative electrode current collector 104a. The central portion 330 is located between the front portion 310 and the rear portion 320 in the X-direction. The central portion 330 is located around the X-direction periphery of the battery element 100.

In the exterior film 300, wrinkles are not present in the central portion 330, but are present in at least one of the front portion 310 and the rear portion 320. Distortion of the shape of the exterior film 300 can cause wrinkles to form in the exterior film 300. If wrinkles are present in the central portion 330, they can be transferred to the battery element 100. This can affect the characteristics of the battery cell 10. For example, uneven spacing between the positive and negative electrodes can occur in the wrinkled areas, resulting in variations in ionic resistance. As another example, uneven spacing between the positive and negative electrodes can accelerate deterioration in areas where the resistance between the positive and negative electrodes is relatively low compared to other areas. It can be relatively difficult to remove wrinkles from the exterior film 300. In this embodiment, even if wrinkles form in the central portion 330, the wrinkles are moved to at least one of the front portion 310 and the rear portion 320. Wrinkles present in the front portion 310 or the rear portion 320 are unlikely to affect the characteristics of the battery cell 10. Therefore, in this embodiment, it is possible to stabilize the characteristics of the battery cell 10. Furthermore, in this embodiment, the space formed on the inner surface of the front portion 310 or rear portion 320 by the wrinkles can be used as a space for storing electrolyte or a space for storing gas.

Wrinkles in the exterior film 300 can occur, for example, due to the difference in size between the battery element 100 and the front cover material 210 or rear cover material 220 when viewed from the X direction.

In one example, the size of the front cover member 210 may be larger than the size of the battery element 100 when viewed in the X direction. For example, the length of the front cover member 210 in the Y direction may be longer than the thickness of the battery element 100 in the Y direction. For example, a battery module may be formed by stacking multiple battery cells 10 in the Y direction. In this example, a compression pad may be placed between the central portions 330 of adjacent battery cells 10 in the Y direction. In this battery module, the length of the front cover member 210 in the Y direction may be longer than the thickness of the battery element 100 in the Y direction by an amount equivalent to the thickness of the compression pad in the Y direction. This allows multiple battery cells 10 to be stacked stably in the Y direction. As in the example described above, the size of the rear cover member 220 may be larger than the size of the battery element 100 when viewed in the X direction.

In another example, the size of the front cover member 210 may be smaller than the size of the battery element 100 when viewed in the X direction. For example, the Y-direction length of the front cover member 210 may be shorter than the Y-direction thickness of the battery element 100. For example, a battery module may be formed by stacking multiple battery cells 10 in the Y direction. In this example, if the Y-direction length of the front cover member 210 is shorter than the Y-direction thickness of the battery element 100, contact and interference between adjacent front cover members 210 in the Y direction can be suppressed. Furthermore, due to the tolerance of the Y-direction thickness of the battery element 100, the actual Y-direction thickness of the battery element 100 may be thinner than the designed Y-direction thickness of the battery element 100. Even in this case, when the Y-direction length of the front cover member 210 is shorter than the Y-direction thickness of the battery element 100, multiple battery cells 10 can be stably stacked in the Y direction to form a battery module.

Figure 5 is a diagram illustrating a first example of a method for manufacturing a battery cell 10 according to an embodiment. In this first example, the battery cell 10 is manufactured as follows.

First, the battery element 100 is manufactured. The battery element 100 has at least one positive electrode, at least one negative electrode, and at least one separator.

Next, the positive electrode tab 110 and the front cover member 210 are joined together. Similarly, the negative electrode tab 120 and the rear cover member 220 are joined together. Next, the positive electrode tab 110 and the positive electrode current collector 102a are joined together. Similarly, the negative electrode tab 120 and the negative electrode current collector 104a are joined together. However, the positive electrode tab 110 and the positive electrode current collector 102a may be joined together before the positive electrode tab 110 and the front cover member 210 are joined together. Similarly, the negative electrode tab 120 and the negative electrode current collector 104a may be joined together before the negative electrode tab 120 and the rear cover member 220 are joined together.

Next, the exterior film 300 is wrapped around the battery element 100, front cover member 210, and rear cover member 220 in the X direction. This forms a wrapped portion 302 around the battery element 100, front cover member 210, and rear cover member 220 in the X direction. In addition, the excess length of the exterior film 300 is pulled out from the wrapped portion 302 as a pulled-out portion 304.

Next, the outer peripheral surface of the front lid member 210 in the X direction and the inner peripheral surface of the front opening of the wrapped portion 302 in the X direction are joined together by heat fusion, thereby forming the front sealed portion 510. Next, the outer peripheral surface of the rear lid member 220 in the X direction and the inner peripheral surface of the rear opening of the wrapped portion 302 in the X direction are joined together by heat fusion, thereby forming the rear sealed portion 520.

Next, as shown in FIG. 5, electrolyte is injected into the storage space 500 through the injection opening 304c. The injection opening 304c is formed by the gap between the first drawer portion 304a and the second drawer portion 304b.

Next, the storage space 500 is vacuum-sealed. Specifically, after evacuating the storage space 500 through the liquid inlet opening 304c, the first and second drawn-out portions 304a and 304b are joined together by heat sealing to form the side sealing portion 530. When the storage space 500 is evacuated, wrinkles may form in the exterior film 300. If wrinkles exist in the central portion 330, they are moved to at least one of the front portion 310 and the rear portion 320.

Then, fold the drawer portion 304 along the top surface of the battery element 100.

In this way, the battery cell 10 is manufactured.

Figure 6 is a diagram illustrating a second example of a method for manufacturing a battery cell 10 according to an embodiment. This second example is similar to the first example described above, except for the following points.

First, the battery element 100 is manufactured in the same manner as in the first example. Next, the positive electrode tab 110 and the front cover member 210 are joined together in the same manner as in the first example. Also, the negative electrode tab 120 and the rear cover member 220 are joined together. Next, the positive electrode tab 110 and the positive electrode current collector 102a are joined together in the same manner as in the first example. Also, the negative electrode tab 120 and the negative electrode current collector 104a are joined together.

Next, the exterior film 300 is wrapped around the battery element 100, front cover member 210, and rear cover member 220 in the X direction to form the wound portion 302 and the drawn-out portion 304. Next, the outer peripheral surface of the front cover member 210 in the X direction and the inner peripheral surface of the front opening of the wound portion 302 in the X direction are joined together by heat fusion, thereby forming the front sealed portion 510. Next, the outer peripheral surface of the rear cover member 220 in the X direction and the inner peripheral surface of the rear opening of the wound portion 302 in the X direction are joined together by heat fusion, thereby forming the rear sealed portion 520. Next, the first drawn-out portion 304a and the second drawn-out portion 304b are joined together by heat fusion, thereby forming the side sealed portions 530.

Next, as shown in FIG. 6, the electrolyte is injected into the storage space 500 through the liquid injection hole 210a provided in the front cover member 210. The storage space 500 is then vacuum-sealed. Specifically, the storage space 500 is evacuated through the liquid injection hole 210a, and then the liquid injection hole 210a is closed with a specified cover member. Wrinkles may be formed in the exterior film 300 when the storage space 500 is evacuated. If wrinkles exist in the central portion 330, the wrinkles are moved to at least one of the front portion 310 and the rear portion 320. The liquid injection hole may also be provided in the rear cover member 220.

Next, as in the first example, the pull-out portion 304 is folded along the top surface of the battery element 100.

In this way, the battery cell 10 is manufactured.

Figure 7 is a front perspective view of a battery cell 10A according to a modified example. The battery cell 10A according to the modified example is similar to the battery cell 10 according to the embodiment, except for the following points.

In the modified example, the positive electrode tab 110A is pulled out from approximately the center in the Y direction of the front cover member 210. The negative electrode tab 120A is pulled out from approximately the center in the Y direction of the rear cover member. In the modified example, multiple positive electrode current collector aggregates exist between the battery element and the positive electrode tab 110A. Similarly, multiple negative electrode current collector aggregates exist between the battery element and the negative electrode tab 120A. In the modified example, wrinkles exist in the exterior film 300 around these aggregates. Therefore, in the modified example, the characteristics of the battery cell 10A can be stabilized in the same way as in the embodiment.

The above describes embodiments and variations of the present invention with reference to the drawings, but these are merely examples of the present invention, and various configurations other than those described above can also be adopted.

For example, in an embodiment, the positive electrode tab 110 and the negative electrode tab 120 are arranged on opposite sides of the battery element 100 in the X direction. However, both the positive electrode tab 110 and the negative electrode tab 120 may be arranged on only one of the front and rear sides of the battery element 100 in the X direction. In this case, the front and rear ends of the battery element 100 are covered, for example, by two lid materials. Alternatively, only the side of the battery element 100 from which the positive electrode tab 110 and the negative electrode tab 120 are pulled out may be covered by a lid material. In this example, an exterior film 300 may be sealed on the side of the battery element 100 opposite the lid material and folded along the battery element 100.

10, 10A Battery cell 100 Battery element 102 Positive electrode 102a Positive electrode current collector 104 Negative electrode 104a Negative electrode current collector 110, 110A Positive electrode tab 120, 120A Negative electrode tab 210 Front cover material 210a Liquid injection hole 220 Rear cover material 300 Exterior film 302 Wrapping portion 304 Pulled-out portion 304a First pulled-out portion 304b Second pulled-out portion 304c Liquid injection opening 310 Front portion 320 Rear portion 330 Central portion 500 Storage space 510 Front sealing portion 520 Rear sealing portion 530 Side sealing portion

Claims (3)

a battery element having a longitudinal direction parallel to the first direction ;
a tab electrically connected to the battery element via a current collector aggregate portion drawn out from the battery element;
a cover member that covers one end of the battery element on the first direction side and through which the tab is pulled out;
an exterior film at least partially wrapped around the first direction of the battery element;
Equipped with
wrinkles are present in the exterior film around the gathering portion of the current collector in the first direction ,
The wrinkles are not present around the exterior film around the battery element in the first direction,
a battery cell in which the tab and a portion of the exterior film located around the collecting portion of the current collector in the first direction are not connected to each other. The battery cell according to claim 1 , wherein the size of the lid member is larger than the size of the battery element when viewed from the first direction. The battery cell according to claim 1 , wherein the size of the lid member is smaller than the size of the battery element when viewed from the first direction.