JP6879897B2 - Secondary battery - Google Patents

Description

The present invention relates to a secondary battery, for example, a secondary battery in which a lid is welded to a case in which a power generator is housed.

In recent years, the demand for secondary batteries has been increasing, and the demand for improving the productivity of secondary batteries is increasing. Therefore, the structure of the secondary battery is disclosed in Patent Document 1. As shown in Patent Document 1, in a secondary battery, the power generator is housed in a case in a state where the power generator is housed in a bag-shaped insulating film. Then, the case and the lid are joined by laser welding so that the opening of the case is covered with the lid while the power generator is housed in the case. However, in this laser welding process, if the energy bee invades the main body member, the generator may be damaged. Therefore, Patent Document 2 discloses a technique for preventing the energy beam from entering the case.

In the battery described in Patent Document 2, the battery case is inserted into the opening and a bottomed square tubular body member having a rectangular opening including a pair of long sides of the opening and a pair of short sides of the opening. The opening is closed, and has a pair of lid long sides facing the pair of opening long sides and a pair of lid short sides facing each other of the pair of opening short sides. It has a rectangular plate-shaped lid member. Then, the long side of the opening and the long side of the lid, and the short side of the opening and the short side of the lid are welded by the energy beam. Further, among the openings of the main body member, the pair of opening short sides project inward over the entire opening short sides, and the short sides supporting the lid short sides of the lid member, respectively. It has an inner protruding portion, and the pair of long side portions of the opening project inward over the entire long side portion of the opening, and are lower than the inner protruding portion of the short side in the depth direction of the main body member. It has a long side inner protruding portion that is separated from the lid long side portion of the lid member.

Japanese Unexamined Patent Publication No. 2016-91787 Japanese Unexamined Patent Publication No. 2014-78331

However, when the case and the lid are joined by laser welding, a part of the lid or the member of the case heated by the energy beam may be scattered as spatter. This spatter may enter the insulating film that houses the generator. That is, the techniques described in Patent Documents 1 and 2 can sufficiently prevent spatter from entering the insulating film, and have an internal problem.

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent foreign matter such as spatter from entering the insulating film.

One aspect of the secondary battery of the present invention is a secondary battery having a case in which a power generator is housed and a lid bonded to the upper part of the case by welding, and the case is housed in the power generator. When the case is viewed in cross-sectional view from the side surface on the short side, the width of the generator storage portion is wider than that of the generator storage portion, the opening to which the lid is joined, and the wall of the generator storage portion. The wall surface is formed to be continuous, and has a slope portion formed so that one end is connected to the power generation body storage portion and the other end is opened to the same width as the opening portion, and the power generation body is formed. Is housed in the power generation body storage portion in a state of being housed in a bag-shaped insulating film that insulates the power generation body and the case, and one end of the slope portion is a wall surface of the power generation body storage portion and the insulation film. And the power generator is provided at a position closer to the opening than the deviation point where the generator is separated from the close contact state, and the opening end of the insulating film is closer to the opening than one end of the slope portion and It is provided at a position not in contact with the lid.

Since the secondary battery according to the present invention has the above configuration, a trap space composed of the wall surface of the case and the insulating film is formed immediately below the outer periphery of the opening of the case. Foreign matter such as spatter that invades the case through the gap created between them can be trapped in the trap space.

The secondary battery of the present invention can prevent foreign matter generated in the assembling process from entering the inside of the insulating film.

It is a figure explaining the appearance of the secondary battery which concerns on Embodiment 1. FIG. FIG. 5 is a cross-sectional view seen from the short side side surface of the secondary battery according to the first embodiment. It is sectional drawing seen from the short side side side of the secondary battery which concerns on a comparative example.

Embodiment 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In order to clarify the explanation, the following description and drawings have been omitted or simplified as appropriate. In each drawing, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary.

FIG. 1 shows an external view of the secondary battery 1 according to the first embodiment. As shown in FIG. 1, the secondary battery 1 according to the first embodiment has a case 10 and a lid 20. The lid 20 is provided on the upper part of the case 10. Further, the lid 20 is provided with a positive electrode pole column 21P and a negative electrode pole pillar 21N which serve as terminals for taking out electric power from the generator housed in the case 10.

The case 10 has a rectangular shape in which a short side portion and a long side portion are combined in a top view. Further, the case 10 is formed so that the width of the opening into which the lid 20 is fitted is wider than the width of the bottom when viewed from the side surface on the short side. The overhanging portion (the portion having the width of the opening) of the case 10 and the other portion (the width of the bottom portion) are connected by the slope portion 11. This slope portion, which will be described in detail later, is provided on the upper side (the side closer to the lid) than the half of the case 10.

Here, in the secondary battery 1 according to the first embodiment, the lid 20 is joined to the case 10 by laser welding. Before the joining step of the lid 20, a gap is formed between the case 10 and the lid 20. This gap is formed between the long side side of the case 10 and the lid when the case 10 is viewed from above (when viewed from the lid side). When there is such a gap, foreign matter such as spatter accumulated in the equipment of the process in the repeated laser welding process may enter the case 10 through this gap. In the secondary battery 1 according to the first embodiment, the foreign matter is trapped by the trap space provided in the case 10 to prevent problems caused by the foreign matter. In the following description, spatter enters as an example of foreign matter, but the foreign matter is not limited to spatter.

Therefore, referring to the cross-sectional view of the secondary battery 1 according to the first embodiment as viewed from the side surface on the short side, the position of the slope portion 11 of the secondary battery 1 according to the first embodiment and the structure of the case 10 are described. This will be described in detail. Therefore, FIG. 2 shows a cross-sectional view of the secondary battery according to the first embodiment as viewed from the short side side surface.

As shown in FIG. 2, in the secondary battery 1 according to the first embodiment, the power generator 30 is housed in the case 10. Further, the power generator 30 is housed in the case 10 in a state of being housed in the bag-shaped insulating film 31. In FIG. 2, the portion of the case 10 in which the generator 30 is housed is designated as the generator storage portion 13. The power generator 30 is a part of a wound body in which sheets of a positive electrode night, a separator, and a negative electrode night are stacked and wound. The outermost circumference of this wound body serves as a separator. Further, the insulating film 31 is thicker than the separator constituting the power generator 30. The insulating film 31 is, for example, a resin film such as polypropylene. The thickness of the insulating film is about 50 to 200 μm.

Here, the relationship between the wound body and the power generator will be described. In the secondary battery 1, sheets of a positive electrode overnight, a separator, and a negative electrode overnight are stacked and wound to form a wound body. The portion of the positive electrode foil to which the active material is applied, the region of the negative electrode foil to which the active material is applied, and the separator are overlapped with each other to form the power generator 30. Further, the wound body is formed so that the region of the positive electrode foil to which the active material is not applied protrudes from the power generator 30, and a current collector plate is attached to this protruding portion, and the electrode of the current collector plate secondary battery is attached. It is connected to the pole pillar that becomes the terminal. Further, the wound body is formed so that the region of the negative electrode foil to which the active material is not applied protrudes from the power generator 30, and a current collector plate is attached to this protruding portion, and the electrode of the current collector plate secondary battery is attached. It is connected to the pole pillar that becomes the terminal.

The case 10 has a relationship of W1> W2 when the width of the opening covered with the lid 20 is W1 and the width of the bottom is W2. Then, in the case 10, the wall surfaces of the portions having different widths are connected by the slope portion 11. Further, in the secondary battery 1 according to the first embodiment, the position of the open end of the insulating film 31 is closer to the lid 20 than the end A of the slope portion 11 on the generator storage portion 13 side and does not come into contact with the lid 20. Set to position. In FIG. 2, the length of the insulating film 31 protruding from the end A on the side of the generator housing portion 13 of the slope portion 11 is defined as H1. This length H1 is, for example, about 2 to 7 mm, and is preferably a length that allows the user to stand in the vertical direction (direction orthogonal to the lid 20) as much as possible. This is because if the length of the insulating film 31 is such that it cannot stand, it will stick to the case 10 on the slope portion 11 side, or the film will stick to the generator 30, and the trap space 12, which will be described later, will not be formed. is there.

Here, the position of the end portion A on the side of the generator housing portion 13 of the slope portion 11 will be described in detail. In the secondary battery 1 according to the first embodiment, the insulating film 31 and the power generator 30 are housed in the case 10, and the power generator storage unit 13 is predetermined with respect to the surface of the case 10 in the long side direction. Pressure is applied to bring the wall surface of the case 10, the insulating film 31, and the power generator 30 into close contact with each other. In this pressing step, the power generator 30 rises toward the lid 20 side. In FIG. 2, after this pressing step, the divergence point at which the wall surface of the power generation body storage portion 13, the insulating film 31 and the power generation body 30 are separated from the close contact state is defined as B. The end portion A of the slope portion 11 on the generator storage portion 13 side is set so as to be located on the lid 20 side of the dissociation point B.

Here, the relationship between the end portion A of the slope portion 11 and the deviation point B will be described in more detail. The flat portion of the generator 30 (for example, the generator storage portion 13 below the deviation point B) needs to be pressed in order to improve battery performance and the like. However, when the dissociation point B is above the end portion A, a trap space exists next to the flat portion of the generator 30, and thus a foreign matter exists, and there is a high possibility that the foreign matter is pressed together. .. If a pressing force is applied to the flat portion while the foreign matter is sandwiched in this way, the possibility of a short circuit in the generator increases. Further, when the end portion A is below the deviation point B, there is also a process difficulty that it is difficult to apply a pressing force to the flat portion. Further, when the end portion A is above the deviation point A, the case 10 and the insulating film 31 are in close contact with each other in the region below the trap space 12, so that foreign matter is unlikely to be mixed in the portion where the pressing force is applied. Become.

By setting the end portion A of the slope portion 11 on the generator housing portion 13 side, the protrusion amount H1 of the insulating film 31, and the width W1 on the opening side of the case as described above, the case 10 has a trap space. 12 is formed.

In the example shown in FIG. 2, the slope portion 11 is a wall surface formed so as to be continuous with the wall of the generator housing portion 13, one end of which is connected to the generator storage portion 13 and the other end of which is the same as the opening. It is formed to open to the width. Then, between the opening of the case 10 and the other end of the slope portion 11, a wall surface 14 substantially orthogonal to the lid 20 is formed when the case is viewed in cross section from the side surface on the short side. By providing the wall surface 14 between the opening of the case 10 and the other end of the slope portion 11, the trap space 12 can be widened and the trapping ability of the spatter DST can be improved. However, it is also possible to eliminate the wall surface between the opening of the case 10 and the other end of the slope portion 11.

From the above description, in the secondary battery 1 according to the first embodiment, in the state before the lid 20 is laser-welded to the case 10, a gap is formed between the case 10 and the lid 20. Foreign matter may enter the case 10. However, in the secondary battery 1 according to the first embodiment, the trap space 12 is provided directly under the gap formed between the case 10 and the lid 20, and a foreign matter is tentatively introduced from the gap between the case 10 and the lid 20. Even if it enters the inside of 10, the foreign matter can be trapped in the trap space 12 to prevent the foreign matter from entering the portion of the wall surface of the case 10 to which the pressing force is applied. Further, in the secondary battery 1 according to the first embodiment, since the insulating film 31 constitutes one of the wall surfaces forming the trap space 12, foreign matter such as a spatter DST is between the insulating film 31 and the generator 30. It is possible to prevent it from entering. Even if foreign matter enters the region of the generator housing 13 where the pressing force is applied between the insulating film 31 and the case 10, since the insulating film 31 is thicker than the separator, it is between the insulating film 31 and the separator. The secondary battery 1 according to the first embodiment also has an effect that a short circuit is less likely to occur than when a foreign substance is mixed in the secondary battery 1.

Here, as a comparative example, mixing of spatter DST in a secondary battery that does not have the trap space 12 of the secondary battery 1 according to the first embodiment will be described. FIG. 3 shows a cross-sectional view of the secondary battery according to the comparative example as viewed from the side surface on the short side. As shown in FIG. 3, when there is no trap space 12, if spatter DST occurs in the process of welding the lid 20 to the case 10, there is no gap between the case 10 and the insulating film 31, so that the spatter DST is an insulating film. It gets in between 31 and the generator 30. Then, in that state, when pressure is applied to the wall surface of the case 10 in the pressing process, the power generation body 30 rises, and the spatter DST enters between the power generation body 30 and the wall surface of the insulating film 31 or the power generation body storage portion 13. Pressure may be applied to the case 10.

However, in the secondary battery 1 according to the first embodiment, by trapping the sputtered DST in the trap space 12, it is possible to prevent the sputtered DST from coming into contact with the separator of the generator 30 in the pressing step. Further, in the secondary battery 1 according to the first embodiment, even when the spatter DST enters below the trap space 12, the spatter DST enters between the insulating film 31 and the wall surface of the generator housing portion 13. .. Since the insulating film 31 is a member thicker than the separator of the power generation body 30, it is possible to prevent the sputter DST from touching the separator of the power generation body 30.

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit.

1 Rechargeable battery 10 Case 11 Slope part 12 Trap space 13 Power generator storage part 14 Wall surface 20 Lid 21P Positive electrode pole 21N Negative pole pole 30 Power generator 31 Insulation film

Claims (4)

A secondary battery having a case in which a power generator is housed and a lid joined by welding to the upper part of the case.
The case is
The generator storage unit in which the generator is stored and
When the case is viewed in cross section from the side surface on the short side, the opening is wider than the generator housing portion and the lid is joined to the case.
A wall surface formed so as to be continuous with the wall of the power generation body storage part, one end of which is connected to the power generation body storage part, and the other end of which is formed so as to open to the same width as the opening. Have,
The power generator is housed in the power generator storage unit in a state of being housed in a bag-shaped insulating film that insulates the power generator and the case.
One end of the slope portion is provided at a position closer to the opening than the wall surface of the generator housing portion, the insulating film, and the dissociation point at which the generator is separated from the close contact state.
A secondary battery provided at a position where the opening end of the insulating film is closer to the opening than one end of the slope portion and is not in contact with the lid. The divergence point is a state in which the surface of the power generation storage portion in the long side direction of the case is pressed from both sides, and the wall surface of the power generation storage portion, the insulating film, and the power generation body are in close contact with each other. The secondary battery according to claim 1, which is in a state of being separated from the battery. The secondary battery according to claim 1, wherein a wall surface substantially orthogonal to the lid is formed between the opening and the other end of the slope when the case is viewed in cross section from the side surface on the short side. The secondary battery according to claim 1, wherein the insulating film is thicker than the separator constituting the power generator.

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