JP7362682B2 - secondary battery - Google Patents

Description

The present invention relates to a secondary battery in which, for example, a wound body obtained by stacking a positive electrode sheet, a negative electrode sheet, and a separator is housed in a battery case.

Some secondary batteries include a case in which a wound body in which a positive electrode sheet, a negative electrode sheet, and a separator are laminated is housed as a power body. In such a secondary battery, an electrolytic solution is injected into the case and permeates into the active material layer (or composite material layer) coated on the positive electrode sheet and the negative electrode sheet that constitute the wound body. A technique for permeating this electrolytic solution into an active material layer is disclosed in Patent Document 1.

The electricity storage device described in Patent Document 1 includes an electrode including an electrode current collector having a plurality of through holes and an electrode mixture layer provided thereon, and an electrode that is connected to the electrode current collector and transmits ions to the electrode mixture layer. an ion supply source, and the electrode current collector is provided with a first region having a predetermined through-hole aperture ratio, and a second region having a through-hole aperture ratio larger than the first region. It is characterized by

Japanese Patent Application Publication No. 2010-040370

However, the secondary battery described in Patent Document 1 has a laminated structure in which a plurality of positive electrode sheets, negative electrode sheets, and separators are laminated, and cannot be directly applied to a secondary battery using a wound body as a power body. Specifically, in the wound body, the penetration path of the electrolyte is at two end portions that are perpendicular to the winding direction of the wound body, and the penetration path is narrower than in the case of a laminate. In addition, when welding the bus bar, which is the path for power extraction, with the wound body, both ends of the wound body, which are the path for the electrolyte to penetrate, are crushed and welded, which further limits the size of the path for the electrolyte to penetrate. There is a problem. That is, in a secondary battery having a wound body as a power body, there is a problem that the permeation path of the electrolyte is restricted and it takes a long time for the electrolyte to permeate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the permeability of an electrolyte in a secondary battery.

One embodiment of the secondary battery of the present invention includes a wound body in which a positive electrode sheet, a negative electrode sheet, and a separator are laminated and wound, and an active material corresponding to the polarity of each sheet among the positive electrode sheet and the negative electrode sheet. a bus bar that is electrically connected to an uncoated current collector foil, the current collector foil and the bus bar are joined to each other at a welding portion, and the current collector foil has a winding of the wound body. A slit passing through the plurality of layers of the current collector foil is selectively provided in a region from the lower end of the welding part to at least a height between the upper and lower ends of the welding part when the direction parallel to the direction is the up-down direction. It will be done.

In the secondary battery of the present invention, the slit constitutes a path for supplying the electrolyte to the region where penetration of the electrolyte is prevented by the weld.

According to the secondary battery of the present invention, the permeability of the electrolyte of the secondary battery can be improved.

1 is a schematic diagram of a secondary battery according to Embodiment 1. FIG. FIG. 3 is a diagram illustrating a permeation route of an electrolytic solution in the secondary battery according to the first embodiment. FIG. 3 is a diagram illustrating a liquid injection process in the secondary battery according to the first embodiment. FIG. 3 is a diagram illustrating a permeation route of an electrolytic solution in a secondary battery according to a second embodiment. FIG. 7 is a diagram illustrating a permeation route of an electrolytic solution in a secondary battery according to a third embodiment. FIG. 7 is another diagram illustrating a permeation route of an electrolytic solution in the secondary battery according to the third embodiment.

For clarity of explanation, the following description and drawings are omitted and simplified as appropriate. Further, in each drawing, the same elements are denoted by the same reference numerals, and redundant explanation will be omitted as necessary.
In the following, regarding the secondary battery according to the embodiment, a power unit that is housed in the case of the battery cell of the secondary battery will be explained, but it should be noted that the secondary battery is the part that is covered by the case. is necessary.

Embodiment 1
FIG. 1 shows a schematic diagram of a secondary battery 1 according to the first embodiment. In FIG. 1, only the wound body and bus bar of the secondary battery 1 housed in the case are shown. As shown in FIG. 1, the secondary battery 1 according to the first embodiment includes a wound body 10, a positive bus bar 21, and a negative bus bar 22. In addition, the wound body 10 is a state in which a positive electrode sheet coated with a positive electrode active material (or a positive electrode composite material), a negative electrode sheet coated with a negative electrode active material (or a negative electrode composite material), and a separator are stacked. It is wound with.

A positive current collector foil 11 and a negative current collector foil 12 are provided at two ends of the wound body 10 perpendicular to the winding direction. The positive electrode current collector foil 11 is a metal foil that is not coated with a positive electrode active material among the positive electrode sheets. The negative electrode current collector foil 12 is a metal foil that is not coated with a negative electrode active material among the negative electrode sheets. The positive bus bar 21 is electrically connected to the positive current collector foil 11 by welding, and the negative bus bar 22 is electrically connected to the negative current collector foil 12 by welding. At this time, in the secondary battery 1, the current collecting foils and the bus bar are joined in a state where the current collecting foils overlapped in the wound state are crushed together. In FIG. 1 , the welded portion 31 is the joint between the positive bus bar 21 and the positive current collector foil 11 . In addition, a welded portion 32 was used as a joint between the negative bus bar 22 and the negative current collector foil 12 .

In the secondary battery 1 according to the first embodiment, a slit 41 is provided in the positive electrode current collector foil 11. Further, a slit 42 is provided in the negative electrode current collector foil 12. The slits 41 and 42 extend from the lower ends of the welds 31 and 32 to at least the height between the upper and lower ends of the welds 31 and 32 when the vertical direction is parallel to the winding direction of the wound body 10. This is a hole that selectively penetrates multiple layers of current collector foil. Furthermore, the slits 41 and 42 are formed at least between the bus bar and the region of the wound body coated with the active material. In the example shown in FIG. 1, the slits 41 and 42 have a plurality of holes having a vertically elongated shape. Furthermore, the slits 41 and 42 are formed in a region extending from a position below the lower end of the welded portions 31 and 32 to a height exceeding the upper end.

Here, the liquid injection path formed by the slits 41 and 42 will be explained. Therefore, FIG. 2 is a diagram illustrating the permeation route of the electrolyte in the secondary battery 1 according to the first embodiment. Note that since the configuration of the slit is the same on both the positive bus bar 21 side and the negative bus bar 22 side, only the configuration on the positive bus bar 21 side is shown in FIG. In addition, when extracting power from the wound body 10 using the positive electrode bus bar 21, a plurality of positive electrodes are wound at the same position at the welding part 31 where the positive electrode bus bar 21 and the positive electrode current collector foil 11 are joined. The current collecting foils 11 are bundled together. Therefore, the injection path through which the electrolytic solution permeates into the wound body 10 from the welded portion 31 is cut off.

In particular, FIG. 2 shows a state in which the water level of the electrolytic solution is lower than the upper end LU of the welded portion 31 as the electrolytic solution permeates into the wound body. As shown in FIG. 2, in the secondary battery 1 according to the first embodiment, the electrolyte is absorbed into the positive electrode current collector foil 11 from a portion below the lower end LD of the welded portion 31. The electrolytic solution absorbed by the positive electrode current collector foil 11 is sucked upward by the capillary phenomenon generated by the slits 41. Then, the sucked up electrolyte is absorbed into the wound body 10. In other words, in the secondary battery 1 according to the first embodiment, even if there is a part where the welded part 31 blocks the penetration path of the electrolytic solution, the slit 41 allows the electrolytic solution to pass through the part of the welded part 31 on the side of the wound body 10. By sucking up the electrolyte, absorption of the electrolyte to the side of the welding part 31 and the upper part of the welding part 31 is promoted.

Next, a liquid injection process in the secondary battery 1 according to the first embodiment will be explained. FIG. 3 shows a diagram illustrating a liquid injection process in the secondary battery according to the first embodiment. As a comparative example, FIG. 3 also shows a liquid injection process in a secondary battery without slits 41 and 42. As shown in FIG. 3, in the liquid injection step, an electrolytic solution is injected into the case housing the wound body 10 at stage ST1. In this stage ST1, in the comparative example, there is no electrolyte permeation path due to the welds 31 and 32, so the electrolyte permeates into the wound body 10 at the height portion corresponding to the welds 31 and 32 more than in other parts. I'll be late.

Subsequently, in stage ST2, the electrolytic solution further penetrates into the wound body 10, and the level of the electrolytic solution in the case decreases. In this stage ST2, the penetration of the electrolyte into the wound body 10 is further progressed than in stage ST1, but in the comparative example, there is a large difference in the penetration speed between the lateral parts of the welds 31 and 32 and the other parts. Become. On the other hand, in the secondary battery 1 according to the first embodiment, there is no difference in the rate of penetration of the electrolytic solution into the wound body 10 between the lateral portions of the welds 31 and 32 and other portions even at stage ST2.

Subsequently, in stage ST3, the electrolyte penetrates into the wound body 10 further than in stage ST2, and the level of the electrolyte in the case decreases. At this stage ST3, in the comparative example, the penetration of the electrolytic solution into the upper center of the wound body 10 is considerably slower than in the secondary battery 1 according to the first embodiment. In stage ST4, where the electrolyte penetrates further than stage ST3, in the secondary battery 1 according to the first embodiment, the electrolyte penetrates into the entire wound body 10, whereas in the comparative example, the electrolyte penetrates into the upper center. A portion remains where the electrolyte has not penetrated.

From the above description, in the secondary battery 1 according to the first embodiment, slits 41 and 42 for sucking up the electrolyte are provided in the regions of the welded parts 31 and 32 on the wound body 10 side. As a result, the secondary battery 1 according to the first embodiment prevents a decrease in the permeation rate of the electrolyte due to the welding portions 31 and 32 blocking the permeation path of the electrolyte, and prevents the permeation of the electrolyte. The time required can be shortened.

Embodiment 2
In the second embodiment, a secondary battery 2 that is a modification of the secondary battery 1 according to the first embodiment will be described. In the description of the second embodiment, the same components as those described in the first embodiment are given the same reference numerals as those in the first embodiment, and the description thereof will be omitted.

FIG. 4 shows a diagram illustrating a permeation route of the electrolyte in the secondary battery 2 according to the second embodiment. FIG. 4 is a diagram showing the structure of a secondary battery 2 according to the second embodiment corresponding to FIG. 2. As shown in FIG. 4, the secondary battery 2 according to the second embodiment has a plurality of slits 51 that are provided so as to extend in a direction inclined with respect to the vertical direction. Note that this inclination is such that the upper part of the slit 51 approaches the region of the wound body 10 that includes the active material layer. Further, a portion of the slit 51 has a length extending from a region below the lower end LD of the welded portion 31 to above the upper end LU of the welded portion 31 .

In this way, by tilting the upper part of the slit 51 in the direction approaching the wound body 10, the length of the slit that sucks up the electrolyte can be made closer than in the first embodiment, so that the time required for the electrolyte to permeate can be made shorter. It can be shorter than the first embodiment.

Embodiment 3
In Embodiment 3, a secondary battery 3 that is a modification of secondary battery 1 according to Embodiment 1 will be described. In the description of Embodiment 3, the same components as those described in Embodiment 1 are given the same reference numerals as in Embodiment 1, and the description thereof will be omitted.

FIG. 5 shows a diagram illustrating the permeation path of the electrolyte in the secondary battery 3 according to the third embodiment. FIG. 5 is a diagram showing the structure of a secondary battery 3 according to Embodiment 3 corresponding to FIG. 2. As shown in FIG. 5, the secondary battery 3 according to the third embodiment has a plurality of slits 61 extending in the horizontal direction orthogonal to the vertical direction. The plurality of slits 61 are provided from a region below the lower end LD of the welded portion 31 to a region between the upper end LU and the lower end LD of the welded portion 31.

Further, FIG. 6 shows another diagram illustrating the permeation route of the electrolyte in the secondary battery according to the third embodiment. FIG. 6 is a side view of the wound body 10 viewed from a direction (from the side of the wound body) perpendicular to the winding direction of the wound body 10. As shown in FIG. 6, the positive electrode current collector foils 11 are bundled at the welded portion 31, and the intrusion path of the electrolyte is blocked. Further, in the wound body 10 to which the bus bar 21 is welded, a gap of about 150 μm is formed between the plurality of positive electrode current collector foils 11 bundled together at the welded portion 31.

In the secondary battery 3 according to the third embodiment, the electrolytic solution sucked into the interior by the slit 61 is sucked up through the gaps formed between the plurality of positive electrode current collector foils 11 by capillary action. Thereby, in the secondary battery 3 according to the third embodiment, the permeation rate of the electrolyte can be increased similarly to the secondary battery 1 according to the first embodiment.

Further, in the secondary battery 3, current flows from the wound body 10 to the positive electrode bus bar 21 via the positive electrode current collector foil 11, but this current flow is in a horizontal direction. Since the slit 61 is a long slit in the horizontal direction, the slit 61 does not easily obstruct the flow of current in the horizontal direction. That is, since the slit 61 is a horizontally long groove, the secondary battery 3 according to the third embodiment can reduce the resistance value when looking at the entire battery.

Note that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit.

1 Secondary battery 2 Secondary battery 3 Secondary battery 10 Wound body 11 Positive electrode current collector foil 12 Negative electrode current collector foil 21 Positive electrode bus bar 22 Negative electrode bus bar 31 Welded part 32 Welded part 41 Slit 42 Slit 51 Slit 61 Slit

Claims (5)

A wound body formed by laminating and winding a positive electrode sheet, a negative electrode sheet, and a separator;
a bus bar in which an active material corresponding to the polarity of each sheet among the positive electrode sheet and the negative electrode sheet is electrically connected to an uncoated current collector foil;
The current collector foil and the bus bar are joined to each other at a welded portion,
The current collector foil has a height from a position below the lower end of the welded portion to at least a height between the upper and lower ends of the welded portion, when the vertical direction is parallel to the winding direction of the wound body. A linearly extending groove passing through the plurality of layers of current collector foil is formed in the area between the bus bar and the area of the wound body coated with the active material. a slit having a
In the secondary battery, the slit is provided in an area excluding the ends of the wound body in the vertical direction . The secondary battery according to claim 1 , wherein the slit is provided so as to extend in the vertical direction. The secondary battery according to claim 1 , wherein the slit is provided so as to extend in a direction inclined with respect to the vertical direction. The secondary battery according to claim 1 , wherein the slit has a plurality of grooves extending in a lateral direction perpendicular to the up-down direction. 5. The current collector foil and the bus bar are joined together in the welded portion in a state where the current collector foils overlapped in the wound body are crushed together. Secondary battery.

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