Seal member

Abstract

To prevent electrolyte from leaking out of a battery case.SOLUTION: A seal member for closing an opening of a battery case that contains an electrode body and an electrolyte, includes: a first seal member; and a second seal member provided on a surface of the first seal member, having a lower electrolyte permeability than the first seal member and a lower hardness than the first seal member. The first seal member is made of PFA, and the second seal member is made of EPDM.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a sealing member.

Background Art

[0002] As a secondary battery having a structure sealed so that the internal electrolyte does not leak, for example, there is a battery disclosed in Patent Document 1. This battery includes a battery case that houses an electrode body and an electrolyte, and an opening of which is covered with a lid body. A positive electrode terminal and a negative electrode terminal are disposed on the lid body, and these terminals are fixed to the lid body by deforming a protruding portion protruding outside the lid body by caulking. Between the tip of the caulked protruding portion and the lid body, an insulating gasket and a conductive plate for connecting the terminal to an external terminal are disposed. Further, the positive electrode terminal and the negative electrode terminal are located inside the case and have a flange portion joined to a current collecting terminal. A sealing member formed of ethylene propylene rubber in a ring shape is disposed in a compressed state between the flange portion and the lid body. In the battery disclosed in Patent Document 1, the sealing member is brought into close contact with the lid body and the flange portion by the repulsive force of the compressed sealing member, and sealing performance is ensured so that the electrolyte does not leak.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The paths through which the electrolyte in the battery case leaks are classified into a path through the sealing member and a path through the interface between the sealing member and the lid body. Since the above-described ethylene propylene rubber has a property of permeating the electrolyte, the electrolyte may permeate through the sealing member exceeding the allowable amount of leakage even when compressed, and may leak outside the case.

[0005] The present invention has been made in view of the above, and an object thereof is to suppress leakage of the electrolytic solution in the battery case to the outside.

Means for Solving the Problems

[0006] The sheet member according to the present invention is a seal member that closes an opening of a battery case that houses an electrode body and an electrolytic solution, and includes a first seal member and a second seal member provided on the surface of the first seal member, the second seal member having a lower degree of permeability of the electrolytic solution than the first seal member and a lower hardness than the first seal member.

Effects of the Invention

[0007] The seal member according to the present invention has an effect of being able to suppress leakage of the electrolytic solution in the battery case to the outside.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited by the embodiments described below. In the description of the drawings, the same or corresponding elements are appropriately denoted by the same reference numerals. Further, it should be noted that the drawings are schematic, and the dimensional relationships of the respective elements may be different from the actual ones. There may also be portions where the dimensional relationships and ratios are different between the drawings.

[0010] FIG. 1 is a schematic cross-sectional view of a rectangular battery 1 according to an embodiment. The battery 1 is, for example, a lithium-ion battery, which is a secondary battery capable of charging and discharging. The battery 1 is used, for example, as a power source for vehicles such as hybrid vehicles and electric vehicles. The battery 1 includes a rectangular parallelepiped battery case 10, a positive electrode terminal 11, a negative electrode terminal 12, and an electrode body 120.

[0011] The electrode body 120 is formed by laminating a sheet-like positive electrode sheet 131, a sheet-like negative electrode sheet 141, and two sheet-like separators in the same manner as a wound electrode body of a well-known lithium-ion battery, and then winding the positive electrode sheet 131 and the negative electrode sheet 141 while slightly shifting them, and pressing and stretching the obtained product from the side direction to obtain a flat-shaped electrode body.

[0012] The materials and members constituting the electrode body 120 may be the same as those of the electrode body of a conventional lithium-ion battery, and there is no particular limitation. For example, the positive electrode sheet 131 is formed by applying a positive electrode active material layer for a lithium-ion battery on a positive electrode current collector that is a long aluminum foil. The positive electrode active material layer is formed of a positive electrode active material, a conductive agent, and a binder. Further, the negative electrode sheet 141 is formed by applying a negative electrode active material layer for a lithium-ion battery on a negative electrode current collector that is a long copper foil. The negative electrode active material layer is formed of a negative electrode active material, a binder, and a thickener. In addition, examples of the sheet-like separator used together with the positive electrode sheet 131 and the negative electrode sheet 141 include those made of a porous polyolefin resin. By shifting and winding the positive electrode sheet 131 and the negative electrode sheet 141, as shown in FIG. 1, a part of the end of the positive electrode sheet 131 and a part of the end of the negative electrode sheet 141 protrude outward from the part where the separator is wound.

[0013] The battery case 10 is formed of, for example, aluminum, and includes a box-shaped main body 101 with an open upper side and a lid 102. The lid 102 is a component that closes the opening of the main body 101. The lid 102 is formed in a plate-like and rectangular shape, and after the electrode body 120 is housed in the main body 101, it is welded to the main body 101 by, for example, laser welding.

[0014] Further, the lid 102 is provided with a non-return type safety valve 102a that breaks when the internal pressure of the battery case 10 reaches a predetermined pressure near the center in the longitudinal direction. Near this safety valve 102a, a liquid injection hole 102b penetrating the lid 102 is provided. The liquid injection hole 102b is a hole for injecting the electrolytic solution into the battery case 10. This liquid injection hole 102b is closed by a closing member 102c in a negative pressure state where the inside of the battery case 10 is depressurized below atmospheric pressure. Also, the lid 102 is provided with a positive electrode terminal 11 on one end side in the longitudinal direction and a negative electrode terminal 12 on the other end side.

[0015] FIG. 2 is a perspective view showing the assembled state of various components assembled to the lid 102. In FIG. 2, the state where the positive electrode terminal 11 is disassembled is shown on the left side, and the state where the negative electrode terminal 12 is assembled to the lid 102 is shown on the right side.

[0016] The lid 102 is provided with through holes 102d penetrating vertically at both ends in the longitudinal direction. On the upper surface side of the lid 102, a first insulator 115 having insulation is disposed. This first insulator 115 is provided with a through hole 115a having substantially the same inner diameter as the through hole 102d in the lid 102, and a recess 115b in which the head portion 111a of a bolt 111 having conductivity projects upward and fits. And on the upper surface of the first insulator 115, a connecting member 112 having conductivity is disposed so as to sandwich the head portion 111a of the bolt 111 fitted in the recess 115b.

[0017] The connecting member 112 is provided with a first through-hole 112a having substantially the same inner diameter as the through-hole 102d in the lid portion 102, and a second through-hole 112b having substantially the same inner diameter as the outer diameter of the screw portion 111b and through which the screw portion 111b passes.

[0018] On the lower surface side of the lid portion 102, a current collector plate 113, a second insulator 116, and a seal member 117 are arranged. The seal member 117 has a disc shape and is provided with a through-hole 117a having substantially the same inner diameter as the through-hole 102d.

[0019] FIG. 3 is a cross-sectional view of the seal member 117. The seal member 117 is composed of a first seal member 117b and a second seal member 117c. The first seal member 117b is formed of, for example, PFA (perfluoroalkoxy alkane). Note that the first seal member 117b may be formed of PTFE (polytetrafluoroethylene). The upper and lower surfaces of the first seal member 117b are coated with the second seal member 117c. The second seal member 117c is, for example, EPDM (ethylene propylene diene rubber). Note that the side surface of the first seal member 117b may also be coated with the second seal member 117c.

[0020] The permeability of the first seal member 117b measured by the cup method in an environment of 80°C is 0.017 to 0.021 mg / cm 2 ·h when the first seal member 117b is formed of PFA, and the permeability of the second seal member 117c measured by the cup method in an environment of 80°C is 0.503 to 0.615 mg / cm 2 ·h when the second seal member 117c is formed of EPDM. Note that these permeabilities are an example, and the permeability varies depending on the environment and the type of electrolyte.

[0021] The second insulator 116 is provided with a through-hole 116a having an inner diameter larger than the outer diameter of the seal member 117. The current collector plate 113 is arranged below the second insulator 116 and the seal member 117.

[0022] The lower part of the current collector plate 113 that constitutes the positive electrode terminal 11 is connected to the positive electrode sheet 131, and the lower part of the current collector plate 113 that constitutes the negative electrode terminal 12 is connected to the negative electrode sheet 141. Also, on the upper part of the current collector plate 113, a flat part 113b that is in surface contact with the lower surface of the seal member 117 is provided. Further, on the upper surface of this flat part 113b, a cylindrical rivet part 113a having an outer diameter substantially the same as the inner diameter of the through hole 102d is provided.

[0023] This rivet part 113a is passed through the through holes 117a, 116a, 102d, 115a, and the first through hole 112a, and by crushing the upper end part of the rivet part 113a that protrudes above the connecting member 112, as shown on the right side in FIG. 2, each member is fastened.

[0024] Note that the thickness of the seal member 117 is slightly thicker than the thickness of the part where the through hole 116a is provided in the second insulator 116. Therefore, when the above-described members are fastened, the seal member 117 is compressed, the upper surface of the seal member 117 contacts the lower surface of the lid part 102, and the lower surface of the seal member 117 contacts the upper surface of the flat part 113b. Thereby, the through hole 102d is sealed by the compressed seal member 117.

[0025] FIG. 4 is an enlarged cross-sectional view of the vicinity of the assembled seal member 117. The path through which the electrolytic solution in the battery case 10 permeates the seal member 117 has a path through the first seal member 117b and a path through the interface between the seal member 117 and the lid part 102, as indicated by the arrows in FIG. 4.

[0026] For example, when the seal member 117 is formed only of PFA, since the transparency is lower than that of EPDM, the permeation of the electrolytic solution can be reduced compared to the case where it is formed only of EPDM. However, while the Shore hardness of EPDM is generally A68, the Shore hardness of PFA is generally D64, which is harder. Therefore, the allowable amount of compression is small, and if over-compression occurs, the seal member 117 may crack. Further, when the seal member 117 is formed only of PFA, if the surface of the PFA is rough, it is impossible to prevent the electrolytic solution from passing through the interface between the seal member 117 and the lid portion 102.

[0027] In the present embodiment, on the upper and lower surfaces of the first seal member 117b formed of PFA, there is a second seal member 117c made of EPDM that is softer than PFA. The second seal member 117c, which is made of EPDM and has a lower degree of permeation of the electrolytic solution than PFA and is softer than PFA, fills the space between the surface of the first seal member 117b made of PFA and the lid portion 102. Therefore, compared to the case where the seal member 117 is formed only of PFA, the permeation of the electrolytic solution through the seal member 117 can be suppressed, and the leakage of the electrolytic solution in the battery case 10 to the outside can be suppressed.

Explanation of Signs

[0028] 1 Battery 10 Battery case 113 Current collector 113a Rivet portion 115 First insulator 116 Second insulator 117 Seal member 117b First seal member 117c Second seal member 120 Electrode body 131 Positive electrode sheet 141 Negative electrode sheet

Claims

【Claim 1】 A seal member for closing an opening of a battery case that houses an electrode body and an electrolytic solution, a first seal member, a second seal member provided on the surface of the first seal member, having a lower degree of permeability to the electrolytic solution than the first seal member and a lower hardness than the first seal member, The seal member comprising.

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