JP2022158284A - flat battery - Google Patents

Abstract

To provide a flat battery with excellent sealing performance.SOLUTION: A flat battery disclosed herein includes a battery container and a power generation element housed in the battery container. The battery container includes an outer can having a bottom portion and a peripheral wall portion, a sealing body, and an annular gasket disposed between the outer can and the sealing body. The outer peripheral side of the gasket is in contact with the inner surface of the peripheral wall of the outer can. The gasket is made of a resin having a tensile modulus of elasticity of 1000 MPa or more as a base material, and the surface of the outer peripheral side of the gasket is composed of a resin having a lower tensile modulus of elasticity than that of the base material.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present application relates to a flat battery with excellent sealing properties.

2. Description of the Related Art Conventionally, flat-shaped batteries called coin-shaped batteries and button-shaped batteries have been known. Such a flat battery uses a battery container formed by interposing a gasket between the outer can and the sealing member and crimping the open end of the outer can inward. In this way, in the flat battery, the battery container is sealed and hermetically sealed by disposing a gasket between the outer can and the sealing member and crimping the gasket.

However, in flat batteries in which the battery container is sealed with a gasket, the gas and electrolyte solution generated by the electrochemical reaction of the battery leak from a small gap in the sealing part, which reduces battery performance and safety. It may be damaged.

Various proposals have been made to solve the above problems. A sealed battery has been proposed which is flexible and coated with a second resin layer formed by chemical vapor deposition.

JP-A-5-121058

However, the effect of the sealed battery proposed in Patent Literature 1 was confirmed by applying it to a cylindrical battery, and further study is required to apply it to a flat battery. Therefore, when the present inventors conducted a structural analysis of a flat battery using an outer can and a gasket, it was found that the contact pressure between the outer can and the gasket could be improved if certain conditions were met. It was found that a flat battery with improved leakage resistance can be realized.

The present application has been made under the above circumstances, and provides a flat battery with excellent sealing properties.

A flat battery of the present application includes a battery container and a power generating element housed in the battery container, the battery container comprising an outer can having a bottom portion and a peripheral wall portion, a sealing body, and the outer can. and an annular gasket disposed between the sealing body, the outer peripheral side of the gasket is in contact with the inner surface of the peripheral wall portion of the outer can, and the gasket is a resin having a tensile modulus of elasticity of 1000 MPa or more. is used as a base material, and the surface portion on the outer peripheral side of the gasket is made of a resin having a lower tensile modulus than that of the base material.

According to the present application, it is possible to provide a flat battery with excellent sealing properties.

FIG. 1 is a cross-sectional view schematically showing a flat battery of the embodiment. FIG. 2 is an enlarged view of part A in FIG. FIG. 3A is a partial cross-sectional view showing structure 1 before caulking in structural analysis using the outer can and gasket, and FIG. 3B shows structure 2 before caulking in structural analysis using the outer can and gasket. It is a partial cross-sectional view. 4A is a diagram showing the results of calculation of the contact pressure between the outer can and the gasket by changing the tensile elastic modulus of the surface resin of structure 1, and FIG. FIG. 10 is a diagram showing the results of calculating the contact pressure between the outer can and the gasket with different ratios. FIG. 5A is a cross-sectional view of structure 1 with ref crimped, and FIG. 5B is a cross-sectional view of structure 1 with case 1-1 crimped. 6A is a cross-sectional view of structure 2 with ref crimped, and FIG. 6B is a cross-sectional view of structure 2 with case 2-1 crimped. 7A is a diagram showing the results of calculation of the maximum contact pressure between the outer can and the gasket by changing the tensile elastic modulus of the surface resin of structure 1, and FIG. FIG. 5 is a diagram showing the results of calculating the maximum contact pressure between the outer can and the gasket while changing the tensile modulus. 8A is a diagram showing the results of calculating the contact pressure integral value between the outer can and the gasket by changing the tensile elastic modulus of the surface resin of structure 1, and FIG. FIG. 10 is a diagram showing the results of calculation of the contact pressure integral value between the outer can and the gasket while changing the tensile modulus of elasticity of . 9A to 9D are diagrams in which the overall thickness of the end portion T of the structure 1 is 0.3 mm, and the thickness of the surface portion of the end portion T is varied from 0.05 to 0.2 mm. FIG. 10A shows the relationship between the tensile modulus of elasticity of the surface resin and the thickness of the surface portion of structure 1 shown in FIGS. FIG. 10B is a diagram showing relative ratios, and FIG. 10B shows the tensile elastic modulus and surface thickness of the surface resin of structure 1 shown in FIGS. FIG. 10 is a diagram showing the relationship in relative ratios with the ref gasket as a reference. FIG. 11A shows the results of calculating the maximum contact pressure between the outer can and the gasket by using two types of base materials, PP and PPS, for the gasket of structure 1 and changing the tensile elastic modulus of the surface resin of each. FIG. 11B shows the integral of the contact pressure between the outer can and the gasket by using two types of base materials, PP and PPS, for the gasket of structure 1 and changing the tensile elastic modulus of the resin on each surface. It is a figure which shows the result of having calculated the value. FIG. 12A shows the structure 1 gasket using two types of base materials, PP and PPS, and changing the ratio of the tensile modulus of the resin of each surface portion to the tensile modulus of the base material. 12B is a diagram showing the results of calculating the maximum contact pressure of the base material and the surface resin in relative ratios based on the same tensile modulus, and FIG. Using two types of PPS, the ratio of the tensile elastic modulus of each surface resin to the tensile elastic modulus of the base material was changed, and the integral of the contact pressure between the outer can and the gasket was calculated. FIG. 4 is a diagram showing a relative ratio based on the case where the tensile elastic modulus of the resin of the surface portion is equal.

An embodiment of the flat battery of the present application includes a battery container and a power generation element housed in the battery container, the battery container comprising an outer can having a bottom surface portion and a peripheral wall portion, a sealing body, and the An annular gasket is arranged between the outer can and the sealing member, the outer peripheral side of the gasket is in contact with the inner surface of the peripheral wall portion of the outer can, and the gasket has a tensile modulus of elasticity of 1000 MPa. The above-mentioned resin is used as a base material, and the surface portion on the outer peripheral side of the gasket is made of a resin having a lower tensile modulus than that of the base material.

The flat battery of the present embodiment can improve the contact state between the outer can and the gasket, have excellent airtightness and anti-leakage properties, and improve the sealing performance by providing the above configuration. Moreover, the above configuration is derived from the results of structural analysis using an armored can and a gasket, which will be described later.

In the battery industry, a flat battery whose diameter is larger than its height is called a coin battery or a button battery, but there is no clear difference between the coin battery and the button battery. However, the flat battery of the present embodiment includes both coin batteries and button batteries.

The flat battery of this embodiment will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a flat battery according to this embodiment, and FIG. 2 is an enlarged view of part A in FIG. In the flat battery 10 shown in FIG. 1, a power generating element formed by stacking a positive electrode 11, a separator 12 and a negative electrode 13 is accommodated in a battery container composed of an outer can 14, a sealing member 15, and an annular gasket 16. configured. The sealing body 15 is fitted to the opening of the outer can 14 via a gasket 16 , and the open end 14 a of the outer can 14 is crimped inwardly, whereby the gasket 16 contacts the sealing body 15 . By contacting them, the opening of the outer can 14 is sealed, and the inside of the battery has a sealed structure. Further, the bottom surface of the gasket 16 is compressed by the open end 15a of the sealing member 15 by crimping the open end 14a of the outer can 14, thereby realizing a strong sealing structure.

In the flat-type battery of this embodiment, as shown in FIG. It is in contact with the inner surface of 14c. Further, the gasket 16 is made of a resin R1 having a tensile modulus of elasticity of 1000 MPa or more as a base material, and the outer peripheral side and the bottom surface of the gasket 16 are both made of a resin R2 having a lower tensile modulus than the base material. It is configured.

In this embodiment, the outer peripheral side and bottom side surface portions of the gasket 16 are both made of the resin R2 having a lower tensile modulus than the base material. Only the portion may be made of resin R2 having a lower tensile modulus than the base material.

The thickness of the portion of the gasket 16 made of a resin having a lower tensile modulus than the base material is preferably 0.05 to 0.2 mm, more preferably 0.1 to 0.15 mm. Moreover, the tensile modulus of the resin, which has a lower tensile modulus than the base material of the gasket 16, is preferably 250 to 600 MPa. If the tensile modulus of elasticity of the resin is lower than 250 MPa, the contact pressure between the outer can and the gasket may decrease and the sealing performance may be impaired. It is preferable to Furthermore, the tensile modulus of the resin whose tensile modulus is lower than that of the base material of the gasket 16 is preferably 70% or less, more preferably 50% or less, of the tensile modulus of the base material. preferable.

The preferred configuration of the flat battery of the present embodiment is also derived from the results of structural analysis using the outer can and the gasket.

Structural analysis using an outer can and a gasket will be described below.

<Structural analysis software>
In this structural analysis, general-purpose structural analysis software "LS-DYNA" manufactured by Livermore Software Technology was used.

<Structural analysis structure>
Two types of structures shown in FIG. 3 were used as structures before crimping for structural analysis. However, FIG. 3 shows a partial cross-sectional view in which FIG. 2 is turned upside down. In the structure 1 shown in FIG. 3A, only the surface portion 16b on the outer peripheral side of the gasket 16 on the outer can 14 is made of a resin having a tensile elastic modulus different from that of the base material 16a of the gasket 16. FIG. In structure 2 shown in FIG. 3B, both outer peripheral side and bottom side surface portions 16b and 16c of the gasket 16 on the outer can 14 are made of a resin having a tensile modulus different from that of the base material 16a of the gasket 16. It is what is done. 3A and 3B, the overall thickness of the end portion T of the gasket 16 was set to 0.3 mm, and the thickness of the surface portion 16b of the end portion T was set to 0.1 mm.

<Effect 1 of tensile elastic modulus of surface resin>
FIG. 4A is a diagram showing the results of calculating the contact pressure between the outer can and the gasket by changing the tensile elastic modulus of the resin of the surface portion of Structure 1 above. FIG. 4B is a diagram showing the results of calculating the contact pressure between the outer can and the gasket by changing the tensile elastic modulus of the surface resin of Structure 2 above.

In FIGS. 4A and 4B, a gasket made only of a resin with a tensile modulus of elasticity of 1372 MPa is used as a reference (ref), the base material is made of a resin with a tensile elasticity of 1372 MPa, and the surface portion (thickness 0.1 mm) is tensioned. Case 1-1 and case 2-1 are cases in which a gasket made of a resin with an elastic modulus of 300 MPa is used, the base material is made of a resin with a tensile elastic modulus of 1372 MPa, and the surface portion (thickness 0.1 mm) has a tensile elastic modulus of 2000 MPa. Case 1-2 and case 2-2 show the cases where a gasket made of the resin of . In FIG. 4A, the horizontal axis indicates the length of the contact portion between the outer can and the gasket from point a to point b in FIG. 3A, and the vertical axis indicates the contact pressure between the outer can and the gasket. In FIG. 4B, the horizontal axis indicates the length of the contact portion between the outer can and the gasket from point a to point b in FIG. 3B, and the vertical axis indicates the contact pressure between the outer can and the gasket. Polypropylene (PP) is assumed as the resin having a tensile modulus of 1372 MPa.

FIG. 5A is a cross-sectional view of structure 1 with ref crimped, and FIG. 5B is a cross-sectional view of structure 1 with case 1-1 crimped. 4A, peak 1 (P1) indicates the contact pressure near P1 in FIGS. 5A and 5B, peak 2 (P2) indicates the contact pressure near P2 in FIGS. 5A and 5B, and peak 3 (P3 ) shows the contact pressure near P3 in FIGS. 5A and 5B.

FIG. 6A is a cross-sectional view of the structure 2 with the ref crimped, and FIG. 6B is a cross-sectional view of the structure 2 with the case 2-1 crimped. In FIG. 4B, peak 1 (P1) indicates the contact pressure near P1 in FIGS. 6A and 6B, peak 2 (P2) indicates the contact pressure near P2 in FIGS. 6A and 6B, and peak 3 (P3 ) shows the contact pressure near P3 in FIGS. 6A and 6B.

From FIGS. 4A and 4B, for ref, case 1-1 in which the surface portion on the outer peripheral side of the gasket is made of a resin having a lower tensile modulus than the base material, and the outer peripheral side and the bottom side of the gasket It can be seen that the contact pressure between the outer can and the gasket at P1 is improved in case 2-1, in which the surface portion is made of a resin having a lower tensile modulus than the base material.

<Influence 2 of tensile modulus of surface resin>
FIG. 7A is a diagram showing the results of calculating the maximum contact pressure (P1 in FIG. 4A) between the outer can and the gasket by changing the tensile modulus of the resin of the surface portion of Structure 1 above. FIG. 7B is a diagram showing the results of calculating the maximum contact pressure (P1 in FIG. 4B) between the outer can and the gasket while changing the tensile elastic modulus of the resin of the surface portion of Structure 2 above.

From FIG. 7A, it can be seen that in structure 1, the contact pressure can be improved by about 50% compared to ref by setting the tensile elastic modulus of the surface resin to 300 MPa. Further, from FIG. 7B, it can be seen that by setting the tensile elastic modulus of the surface resin to around 500 MPa, the contact pressure can be improved compared to ref.

<Effect 3 of tensile elastic modulus of surface resin>
FIG. 8A is a diagram showing the results of calculating the contact pressure integral value (total area of the graph of FIG. 4A) between the outer can and the gasket while changing the tensile elastic modulus of the surface resin of Structure 1 above. FIG. 8B is a diagram showing the results of calculating the contact pressure integral value (total area of the graph of FIG. 4B) between the outer can and the gasket while changing the tensile elastic modulus of the surface resin of Structure 2 above.

From FIGS. 8A and 8B, it can be seen that the contact pressure integral value increases as the tensile elastic modulus of the surface portion decreases.

<Relationship between the tensile elastic modulus of the surface resin and the thickness of the surface>
FIGS. 9A to 9D are diagrams in which the overall thickness of the end portion T of the structure 1 is 0.3 mm, and the thickness of the surface portion of the end portion T is varied from 0.05 to 0.2 mm.

FIG. 10A shows the relationship between the tensile modulus of elasticity of the surface resin and the thickness of the surface portion of structure 1 shown in FIGS. It is the figure shown by the relative ratio. In addition, FIG. 10B shows the relationship between the tensile modulus of elasticity and the thickness of the surface portion of the resin on the surface portion of Structure 1 shown in FIGS. It is a diagram showing a reference relative ratio.

From FIG. 10A showing the maximum contact pressure, when the overall thickness of the gasket is 0.3 mm, the thickness of the surface portion in Structure 1 is preferably 0.05 mm or more, and more preferably 0.1 mm or more. , preferably 0.2 mm or less, and more preferably 0.15 mm or less. Also, from FIG. 10B showing the contact pressure integral value, when the overall thickness of the gasket is 0.3 mm, it seems that the thickness of the surface portion in structure 1 is preferably 0.1 to 0.2 mm. be

<Study of surface resin>
From FIG. 10A described above, it can be seen that when the overall thickness of the gasket is 0.3 mm, the tensile elastic modulus of the surface resin is preferably 250 to 600 MPa. Specific resins having a tensile modulus in the range of 250 to 600 MPa include, for example, tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (PFA, 310 to 350 MPa), tetrafluoroethylene/hexafluoropropylene copolymer ( FEP, 350 MPa), polytetrafluoroethylene (PTFE, 410 MPa), and the like.

As the resin-based material having a tensile modulus of elasticity of 250 to 600 MPa, a mixed material of resin and rubber can be used. Examples of resins used in the mixed material include polyolefin resins such as polypropylene (PP) and polyethylene (PE); fluorine resins such as PFA and tetrafluoroethylene-ethylene copolymer (ETFE); polyphenylene sulfide (PPS) and the like. is mentioned. Examples of rubbers used in the mixed material include natural rubber (3 to 30 MPa), nitrile rubber (5 to 25 MPa), ethylene/propylene rubber (5 to 20 MPa), chloroprene rubber (5 to 25 MPa), silicone rubber ( 4 to 10 MPa), fluorine rubber (7 to 20 MPa), ethylene/vinyl acetate rubber (7 to 20 MPa), and the like. The tensile modulus of the mixed material can be adjusted by changing the mixing ratio of the resin and the rubber.

<Influence of material of base material 1>
In FIG. 11A, two types of base materials, PP (tensile modulus: 1372 MPa) and PPS (tensile modulus: 3300 MPa), are used for the base material of the gasket of structure 1, and the tensile modulus of resin on the surface of each is changed. FIG. 10 is a diagram showing the results of calculating the maximum contact pressure between the outer can and the gasket using In FIG. 11B, two types of base materials, PP (tensile modulus: 1372 MPa) and PPS (tensile modulus: 3300 MPa), are used for the base material of the gasket of structure 1, and the tensile modulus of the resin on each surface is changed. FIG. 10 is a diagram showing the result of calculating the contact pressure integral value between the outer can and the gasket using In structure 1, as described above, the overall thickness of the end portion T of the gasket is set to 0.3 mm, and the thickness of the surface portion of the end portion T is set to 0.1 mm.

From FIGS. 11A and 11B, it can be estimated that a resin having a tensile elastic modulus in the range of about 1000 to 3500 MPa can be used as the base material resin. Examples of resins other than PP and PPS having a tensile modulus in the range of about 1000 to 3500 MPa include methacrylic resin (PMMA, 3000 MPa), polycarbonate (PC, 2880 MPa), MC nylon (3500 MPa), nylon 66 (2900 MPa), Examples include polyacetal (3500 MPa), polyvinylidene fluoride (PVDF, 2140 MPa), and the like.

Two or more kinds of the resin forming the base material can be molded and used. For example, the base material may have a core-shell structure, a resin having a relatively high tensile modulus among the resins of the base material may be used for the core portion, and a resin having a relatively low tensile modulus may be used for the shell portion.

<Influence of Base Material Material 2>
FIG. 12A shows the relationship between the tensile modulus of elasticity of the base material and the resin of each surface part, using two types of base materials, PP (tensile modulus: 1372 MPa) and PPS (tensile modulus: 3300 MPa), for the gasket of Structure 1 above. FIG. 10 is a graph showing the results of calculating the maximum contact pressure between the outer can and the gasket by changing the ratio of the tensile elastic moduli of the base material and the resin of the surface portion as a relative ratio based on the case where the tensile elastic moduli are equal. . FIG. 12B shows the relationship between the tensile modulus of elasticity of the base material and the resin of each surface part using two types of base materials, PP (tensile modulus: 1372 MPa) and PPS (tensile modulus of elasticity: 3300 MPa), for the gasket of Structure 1 above. The result of calculating the contact pressure integral value between the outer can and the gasket by changing the ratio of the tensile modulus of elasticity is shown in the relative ratio based on the case where the tensile modulus of the base material and the surface resin are the same. be. In structure 1, as described above, the overall thickness of the end portion T of the gasket was set to 0.3 mm, and the thickness of the surface portion of the end portion T was set to 0.1 mm.

12A and 12B, in order to increase the contact pressure between the outer can and the gasket, it is necessary to set the tensile modulus of the resin forming the surface portion on the outer peripheral side of the gasket to a value of 70% or less of the tensile modulus of the base material. It can be seen that the value is preferably 50% or less, and more preferably 50% or less.

REFERENCE SIGNS LIST 10 Flat battery 11 Positive electrode 12 Separator 13 Negative electrode 14 Outer can 14a Open end 14b Peripheral wall 14c Bottom surface 15 Sealing member 15a Open end 16 Gasket 16a Base material 16b Outer peripheral surface of gasket 16c Bottom surface of gasket Department

Claims (5)

A flat battery including a battery container and a power generation element housed in the battery container,
The battery container includes an outer can having a bottom portion and a peripheral wall portion, a sealing body, and an annular gasket disposed between the outer can and the sealing body,
The outer peripheral side of the gasket is in contact with the inner surface of the peripheral wall portion of the outer can,
The gasket is made of a resin having a tensile modulus of 1000 MPa or more as a base material,
A flat battery, wherein a surface portion on the outer peripheral side of the gasket is made of a resin having a lower tensile modulus than the base material. 2. The flat battery according to claim 1, wherein the portion made of resin having a lower tensile modulus than the base material has a thickness of 0.05 to 0.2 mm. 3. The flat battery according to claim 1, wherein the resin having a lower tensile modulus than the base material has a tensile modulus of 250 to 600 MPa. 4. The flat battery according to claim 1, wherein the tensile elastic modulus of the resin having a lower tensile elastic modulus than that of the base material is 70% or less of the tensile elastic modulus of the base material. The bottom side of the gasket is in contact with the inner surface of the bottom portion of the outer can,
The flat battery according to any one of claims 1 to 4, wherein the surface portion of the gasket on the bottom side is also made of a resin having a lower tensile modulus than the base material.

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