JP6017884B2 - Battery sealing material - Google Patents

Description

  The present invention relates to a battery sealing material.

  In the terminal extraction part of the sealed battery, the sealing material is compressed by crimping and deforming the current collecting terminal in a state where the sealing material is arranged around the current collecting terminal extending from the inside of the case. A caulking structure is employed in which the current collecting terminal is fastened to the case (see, for example, Patent Document 1).

  Since the battery is filled with an electrolytic solution, the sealing material is required to have resistance to the electrolytic solution used. For example, Patent Document 1 exemplifies polyolefin resins such as PP and PE, fluorine resins such as PFA and PTFE, or polymer materials such as PPS, polyimide resin, polyamideimide resin, PEEK, and PES.

JP 2010-282848 A

Among the above materials, PFA having low moisture permeability and excellent moldability has attracted attention as the next sealing material. However, there is a problem to be solved such as considering thermal damage to the PFA because the vicinity of the terminal becomes high temperature (90 ° C. or higher, which is the glass transition temperature of the PFA) when the battery generates heat or when the battery is manufactured.
The present invention provides a battery sealing material in consideration of thermal damage to the PFA when PFA is adopted as the material of the sealing material.

The battery sealing material of the present invention seals the inside of the case by closing the opening of the case for housing the electrode body with a lid, takes out the terminal to the outside through the lid, and seals between the terminal and the lid. A sealing material for a battery used for a sealed battery in which the terminal is fixed to a lid via a sealing material by caulking the terminal in a state where the material is arranged, and the material of the sealing material is PFA The PFA has a specific gravity of 2.15 or more and at least the surface roughness of the seal part is 0.05 [μm] or less.
The sealing portion of the sealing material is a contact portion with the terminal and refers to a portion that receives deformation force due to the caulking. In the sealing material, the surface roughness of the entire outer peripheral portion including the sealing portion may be 0.05 [μm] or less.

  ADVANTAGE OF THE INVENTION According to this invention, the battery sealing material which considered the thermal damage to PFA at the time of employ | adopting PFA as a material of a sealing material can be provided.

It is a figure which shows a sealed battery. It is a graph which shows the relationship between specific gravity of PFA, and a recovery rate. It is a graph which shows the relationship between the surface roughness of PFA and the compression rate required for sealing. It is a flow which shows the manufacturing method of a sealed battery.

FIG. 1 shows a schematic configuration of a sealed battery 1.
The sealed battery 1 houses an electrode body 3 serving as a power generation element, an electrolytic solution, and the like in a case 2. The lid 4 is welded to the opening surface of the case 2, whereby the opening of the case 2 is closed and sealed.

Outside the lid 4, external terminals 5 for external connection are provided. Each external terminal 5 is fixed to the lid 4 while being insulated via an insulating resin 6. The external terminal 5 is connected to the electrode body 3 by a current collecting terminal 7.
The current collecting terminal 7 is joined to the electrode body 3 in the case 2, taken out through the lid 4, and connected to the external terminal 5. Similarly, the current collecting terminal 7 is fixed in an insulated state with respect to the lid 4 via the insulating resin 6 and the gasket 8.

More specifically, a part of the current collecting terminal 7 protrudes toward the outside of the cover 4 in a state of penetrating the cover 4, the gasket 8, the insulating resin 6 and a part of the external terminal 5, and its tip is caulked. As a result, the lid 4 and the external terminal 5 are fastened via the insulating member 6 and the gasket 8.
In this way, a part of the current collecting terminal 7 is deformed to form the joint 10, and a compressive force is applied to the gasket 8 by the pressing force during caulking. By compressing the gasket 8, the sealing performance of the joint 10 is ensured.

As described above, the gasket 8 functions as a sealing material for the terminal extraction portion of the sealed battery 1.
The gasket 8 is made of PFA (tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin). In order for the gasket 8 made of PFA to function as a sealing material, it is necessary to maintain the sealing performance under the use conditions of the sealed battery 1 (particularly, high temperature conditions such as when the battery is heavily loaded).

As the PFA used as the material of the gasket 8 of the present embodiment, a PFA having a specific gravity of 2.15 or more and at least a surface roughness of the seal portion of 0.05 [μm] or less is used.
First, by setting the specific gravity to 2.15 or more, the crystallinity of PFA is increased to reduce the softening phenomenon of the amorphous part at high temperature. At the same time, by making the surface roughness 0.05 [μm] or less, effective compression at the time of caulking and fastening is realized, and sealing performance can be secured even at a low compression rate. In this way, both heat resistance and sealing properties necessary for the gasket 8 are achieved.
That is, the contradiction of decreasing the recovery rate of the gasket 8 by increasing the crystallinity of the PFA is to reduce the surface roughness of the gasket 8 (smooth the surface) and to reduce the surface pressure at the time of caulking. Sealing at a low compression rate is achieved by keeping the degree of application constant.

[Specific gravity]
Increasing the specific gravity of PFA means increasing the crystallinity by decreasing the proportion of the amorphous part of PFA.
In this embodiment, by increasing the specific gravity of the PFA to a predetermined value or more, deterioration such as sag that may occur when the periphery of the terminal take-out portion of the sealed battery 1 becomes equal to or higher than the glass transition temperature of the PFA is prevented. Yes.

FIG. 2 shows the results of an endurance test performed on PFA having different specific gravities.
The endurance test consists of (1) the PFA of this embodiment with a specific gravity of 2.15, the conventional PFA (A) with a specific gravity of 1.8, and the conventional PFA (B) with a specific gravity of 1.75. Prepare gaskets composed of each PFA, (2) Recovery rate after compression of each gasket 30% and left in a temperature atmosphere at 100 ° C. for 4 hours (return to original size / compression) Measured size x 100).

As shown in FIG. 2, it can be seen that the recovery rate is greatly increased (about 35%) by setting the specific gravity to 2.15 or more. In the conventional cases (A) and (B), it can be seen that the recovery rate is as low as about 25%, and the recovery rate after exposure to high temperature conditions is low.
This is due to abrupt softening due to glass transition of the amorphous part of PFA. In order to obtain a sufficient recovery rate after exposure to a high temperature atmosphere, the specific gravity should be at least 2.15 or more. It turns out that is preferable.

[Surface roughness]
The surface roughness of the gasket 8 is an index indicating the degree of contact between the gasket 8 and the lid 4 at the time of caulking, and the smaller the surface, the more even the surface can be contacted.
In this embodiment, by reducing the surface roughness of the gasket 8 and improving the compression efficiency by improving the contact with the lid 4, it is possible to secure a seal at a low compression rate and to prolong the service life. Has also contributed.

FIG. 3 shows the relationship between the surface roughness and the compression rate necessary for sealing.
The compression rate necessary for sealing (sealability) is determined by the amount of He gas leak, and the minimum compression rate that satisfies this is defined as “compression rate necessary for sealing”. In the leak test, the gasket 8 of the present embodiment has a surface roughness of 0.05 [μm], and the conventional gasket has a surface roughness of 0.5 [μm], and is caulked and fastened to the lid under the same conditions. The amount of He gas leak was measured.

As shown in FIG. 3, it can be seen that by setting the surface roughness to 0.05 [μm] or less, the compression rate required for sealing can be lowered (about 2%). On the other hand, in the conventional gasket, the required compression rate is as high as about 8%. If the compression ratio required for sealing is high, when the gasket material is PFA with a specific gravity of 2.15 or more, it is necessary to increase the caulking load, which may adversely affect peripheral members such as warping of the lid. It is not preferable.
Accordingly, it can be seen that the surface roughness is preferably at least 0.05 [μm] or less in order to ensure sealing performance at a low compression rate.

FIG. 4 shows a part of the manufacturing process of the sealed battery.
In the manufacturing process of the sealed battery 1, the current collector terminal 7 is joined to the electrode body 3, and the current collector terminal 7 is caulked and fastened to the lid 4 with the gasket 8 disposed around the current collector terminal 7. A manufacturing process, sealing process in which the electrode body 3 is housed in the case 2 and the lid 4 is welded and sealed, and a cell drying process in which the battery cell is exposed to a high temperature atmosphere of 90 ° C. or more to dry the electrode body 3 After being sequentially performed, appropriate post-processes such as initial charging and aging processing are performed.

  Thus, the sealed battery 1 has a state where it is exposed to a high-temperature atmosphere at the time of manufacture in addition to at the time of use. In the present embodiment, PFA having a specific gravity of 2.15 or more and a surface roughness of 0.05 [μm] or less is used as the material of the gasket 8, so that it also has seal durability (heat resistance) at the manufacturing stage.

  1: Sealed battery, 2: Case, 4: Cover, 6: Insulating member, 7: Current collecting terminal, 8: Gasket (sealing material)

Claims (1)

Seal the inside of the case by closing the opening of the case containing the electrode body with a lid,
A sealed type in which the terminal is fixed to the lid via the sealing material by taking out the terminal to the outside via the lid and caulking the terminal in a state where the sealing material is disposed between the terminal and the lid. A battery sealing material used for a battery,
The material of the sealing material is only tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer resin (PFA), and the PFA has a specific gravity of 2.15 or more and at least the surface roughness of the seal portion (10-point average roughness). (Rz)) is 0.05 [μm] or less.

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