Electrolyte sealing material

Abstract

An electrolyte sealing material, which is an ethylene-propylene copolymer rubber composition in which PTFE and / or titanium dioxide is compounded in ethylene-propylene copolymer rubber, wherein the compounding amount of PTFE and / or titanium dioxide in the total amount of the filler is 10% by weight or more. The electrolyte sealing material has high gas barrier properties, excellent electrical insulation, resistance to electrolyte, and the compound in the rubber is not extracted by the electrolyte, and the electrolyte sealing material is suitable for use as a sealing material used in various batteries such as lithium-ion batteries, nickel-hydrogen batteries, and the like, electrolytic capacitors, double-layer capacitors, and the like.

Description

Technical Field

[0001] This invention relates to electrolyte sealing materials. More specifically, it relates to electrolyte sealing materials suitable for use as sealing materials in batteries, electrolytic capacitors, double-layer capacitors, and the like. Background Technology

[0002] Ethylene-propylene copolymer rubbers, such as ethylene-propylene copolymer rubbers [EPM] or ethylene-propylene-nonconjugated diene copolymer rubbers [EPDM], are widely used in various sealing components (O-rings, gaskets, etc.) due to their excellent heat resistance, cold resistance, water resistance, and oil resistance.

[0003] Recently, in applications such as automotive electronics and lighting, the operating environments for batteries and capacitors have become increasingly high-temperature-dependent, thus requiring these components to possess superior heat resistance. Furthermore, a major factor determining the lifespan of batteries and capacitors is the degradation of their properties caused by the evaporation of the electrolyte from the rubber seals. This evaporation rate increases to some extent at high temperatures. Therefore, to achieve both heat resistance and long lifespan for batteries and capacitors, rubber materials with excellent gas barrier properties are also needed.

[0004] Currently, electrolyte sealing materials used in lithium-ion batteries and similar products are required to exhibit high gas barrier properties. Furthermore, they must also possess excellent electrical insulation, be resistant to electrolytes, and not adversely affect battery operation due to the extraction of rubber complexes by the electrolyte. Specifically, the permissible extraction amount of rubber complexes is an extremely small amount, around 5 ppm. Therefore, only chemically stable MT carbon black, which does not extract free sulfur, can be used as a filler material for rubber applications.

[0005] In addition, to prevent short circuits in the circuit, starting with the battery, the inherent volume resistivity is required to be 10 ohms. 14 With an insulation value of over Ω·cm, EPDM polymers are used as rubber materials for electrolyte seals in lithium-ion batteries and the like.

[0006] On the other hand, as filler materials compounded in rubber, there are conductive filler materials and insulating filler materials. As insulating filler materials compounded in rubber, silicon dioxide is generally used, but it dissolves under the action of hydrogen fluoride generated by the electrolyte and lacks chemical stability, so it cannot be used as an electrolyte sealing material.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent Application Publication No. 2002-069254 Summary of the Invention

[0010] The technical problem that the invention aims to solve

[0011] The present invention was made in view of the above-mentioned problems and provides an electrolyte sealing material suitable for use in lithium-ion batteries, etc., which solves the following problems: high gas barrier properties, excellent electrical insulation and resistance to electrolyte, and the complexes in the rubber are not extracted by the electrolyte.

[0012] Solution for solving the problem

[0013] The objective of this invention is achieved through an electrolyte sealing material, which is an ethylene-propylene copolymer rubber composition in which PTFE and / or titanium dioxide are incorporated into the ethylene-propylene copolymer rubber, wherein the amount of PTFE and / or titanium dioxide in the total filler material is 10% by weight or more.

[0014] Invention Effects

[0015] The electrolyte sealing material of the present invention achieves excellent results by combining PTFE and / or titanium dioxide, which have electrical insulation, electrolyte resistance and electrolyte extraction resistance, as a filler in a specified proportion in an ethylene-propylene copolymer rubber. That is, it satisfies the desired insulation and does not have an adverse effect on battery operation. Detailed Implementation

[0016] As an ethylene-propylene copolymer rubber, ethylene-propylene-non-conjugated diene ternary copolymer rubber polymer [EPDM] is preferred. As the non-conjugated diene, small amounts of dicyclopentadiene, 1,4-hexadiene, dicyclooctadiene, methylene norbornene, vinyl norbornene, ethylidene norbornene, etc., can be copolymerized. Its Mooney viscosity (ML) 1+4 The temperature (at 125°C) is approximately 25–80, preferably approximately 25–70. Here, as EPDM, commercially available products can be used directly or in combination, such as JSR product EP331 and Mitsui Chemicals product EPT-4010M.

[0017] As an electrically insulating filler compounded in ethylene-propylene copolymer rubber, at least one of PTFE (polytetrafluoroethylene) and titanium dioxide is used at a proportion of 10% by weight or more of the total filler material. From the perspective of ensuring the normal physical properties of the sealing material, it is preferable to use it at a proportion of 45% by weight or more of the total filler material. If the electrically insulating filler material is used at a proportion of less than 10% by weight of the total filler material, the volume resistivity becomes low. Furthermore, even if the electrically insulating filler material is used at the prescribed proportion of the total filler material, when compounded with fillers other than PTFE or titanium dioxide, such as barium sulfate or mica, as shown in Comparative Examples 1 and 2 described later, the water extraction resistance cannot be satisfied. Here, the total filler material refers to the total amount of both electrically insulating and conductive fillers.

[0018] In ethylene-propylene copolymer rubbers, MT carbon black, which is chemically stable and does not extract free sulfur, can be used as a conductive filler in a proportion of typically 150 parts by weight or less, preferably 50 to 150 parts by weight, and more preferably 75 to 125 parts by weight relative to 100 parts by weight of the ethylene-propylene copolymer rubber. By using a specified amount of MT carbon black, the normal physical properties of the resulting sealing material can be ensured. Therefore, PTFE and / or titanium dioxide can be combined at a proportion of approximately 10 to 30% by weight of the total filler material. It should be noted that if MT carbon black is used in proportions exceeding the above range, it may be difficult to ensure a proper seal.

[0019] In rubber compositions where the above-mentioned components are essential, organic peroxides are generally used as crosslinking agents. Examples of organic peroxides include tert-butyl peroxide, dicumyl peroxide, 2,5-dimethyl-2,5-di-tert-butylperoxyhexane, 2,5-dimethyl-2,5-di-tert-butylperoxy-3-hexyne, tert-butylcumyl peroxide, 1,3-di-tert-butylperoxyisopropylbenzene, 2,5-dimethyl-2,5-dibenzoylperoxyhexane, peroxy ketal, and peroxy ester.

[0020] As peroxy ketal, for example, 4,4-di(tert-butylperoxy)valerate, 2,2-di(tert-butylperoxy)butane, 2,2-di[4,4-di(tert-butylperoxy)cyclohexyl]propane, 1,1-di(tert-butylperoxy)cyclohexane, di(3,5,5-trimethylhexanoyl)peroxide, 1,1-di(tert-hexylperoxy)cyclohexane, 1,1-di(tert-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butylperoxy)-2-methylcyclohexane, etc.

[0021] In addition, peroxide esters such as tert-butyl peroxide, tert-butyl peracetate, tert-hexyl peroxide, tert-butyl peroxy-2-ethylhexyl monocarbonate, tert-butyl peroxy-laurate, tert-butyl peroxy-isopropyl monocarbonate, tert-butyl peroxy-3,5,5-trimethylhexanoate, tert-butyl peroxy-maleate, and tert-hexyl peroxy-isopropyl monocarbonate can be used.

[0022] The crosslinking agent can be added at a ratio of about 0.5 to 10 parts by weight, preferably about 0.8 to 5 parts by weight, relative to 100 parts by weight of ethylene-propylene copolymer rubber. Within this range, foaming during crosslinking can be prevented, thus preventing molding. In addition, due to the good crosslinking density, sufficient physical properties are easily obtained.

[0023] In addition, crosslinking accelerators may be included as needed. Common crosslinking accelerators include triallyl isocyanurate, triallyl cyanurate, liquid polybutadiene, N,N'-m-phenylenebismaleimide, and trimethylolpropane trimethacrylate. Adding appropriate amounts of crosslinking accelerators can improve crosslinking efficiency, thereby enhancing heat resistance and mechanical properties.

[0024] In addition to the above-mentioned components, other compounding agents commonly used in the rubber industry, such as acid absorbers, processing aids, plasticizers, lubricants, and anti-aging agents, may be added to the rubber composition as needed, provided that they do not hinder the purpose of the present invention.

[0025] Rubber compositions can be prepared by mixing various materials using a mixing mill such as a single-screw extruder, twin-screw extruder, open roll mill, Banbury mixer, kneader, or high-shear mixer.

[0026] Its cross-linking molding can be carried out by a primary cross-linking at about 150 to 220°C for about 1 to 60 minutes, and by an oven cross-linking (secondary cross-linking) at about 120 to 200°C for about 1 to 24 hours as needed.

[0027] Example

[0028] The present invention will now be described in detail through specific embodiments. It should be noted that the present invention, including its effects, is not limited to these embodiments.

[0029] Example 1

[0030]

[0031]

[0032] The above components were mixed using a closed kneader and open rollers, compressed at 180°C for 6 minutes, and then cross-linked in an oven at 150°C for 1 hour to obtain a test piece with a thickness of 2 mm. The obtained test piece was used to determine its normal physical properties, volume resistivity, water extraction test, and electrolyte immersion test.

[0033] Normal physical properties: JIS K6251 corresponding to ISO 37,

[0034] Standard 6253 corresponding to ISO 7619-1

[0035] Intrinsic volume resistivity: JIS 6271 standard corresponding to ISO 14309

[0036] The double-ring electrode method was used to measure the voltage under an applied voltage of 500V to prevent short circuits in the circuit, starting with the battery.

[0037] Requirement 10 14 Insulation above Ω·cm

[0038] Water extraction test: The test piece was immersed in ion-exchanged water at 90°C for 70 hours to obtain an aqueous extract. The aqueous extract was then subjected to quantitative analysis of anions using ion chromatography. The total amount of all anions detected relative to the weight of the immersed test piece was evaluated.

[0039] Electrolyte seals require water extractability of less than 5 ppm.

[0040] Electrolyte immersion test: In a mixture of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate in a volume ratio of 3 / 4 / 3, LiPF4 is mixed to a LiPF4 concentration of 1 mol / L. Using the resulting test solution, based on JIS K6258 corresponding to ISO 1817, the test piece is immersed at 90°C for 250 hours. The volume change rate is evaluated. The electrolyte seal requires a volume change rate of less than 10%.

[0041] Example 2

[0042] In Example 1, the amount of MT carbon black was changed to 70 parts by weight and the amount of titanium dioxide was changed to 16.7 parts by weight.

[0043] Example 3

[0044] In Example 1, the amount of MT carbon black was changed to 52.5 parts by weight and the amount of titanium dioxide was changed to 25 parts by weight, respectively.

[0045] Example 4

[0046] In Example 1, MT carbon black was not used; the amount of titanium dioxide was changed to 50 parts by weight and the amount of peroxide sulfide was changed to 4.5 parts by weight.

[0047] Example 5

[0048] In Example 1, 14 parts by weight of PTFE (Daikin Industries, Ltd. product Rubron L-5F) were used instead of titanium dioxide.

[0049] Comparative Example 1

[0050] In Example 1, 10 parts by weight of barium sulfate (Sakai Chemical Industry product Bariace B-54) were used instead of titanium dioxide.

[0051] Comparative Example 2

[0052] In Example 1, 10 parts by weight of mica (Sanshin Mica product FNS) were used instead of titanium dioxide.

[0053] Comparative Example 3

[0054] In Example 1, the amount of MT carbon black was changed to 92 parts by weight and the amount of titanium dioxide was changed to 6.3 parts by weight.

[0055] Comparative Example 4

[0056] In Example 1, titanium dioxide was not used, and the amount of MT carbon black was changed to 105 parts by weight.

[0057] Comparative Example 5

[0058] In Example 5, the amount of PTFE was changed to 6.3 parts by weight.

[0059] The results obtained in the above embodiments and comparative examples, together with the proportion of insulating filler, are shown in the table below.

[0060] surface

[0061] Industrial availability

[0062] The sealing material obtained from the electrolyte sealing material of the present invention exhibits resistance to electrolyte and resistance to electrolyte extraction, and is therefore suitable for use as a sealing material in various batteries such as lithium-ion batteries and nickel-metal hydride batteries, electrolytic capacitors, double-layer capacitors, etc.

Claims

1. An electrolyte sealing material, characterized by comprising: The electrolyte sealing material is an ethylene-propylene copolymer rubber composition in which PTFE and / or titanium dioxide and MT carbon black are compounded as a filler material in ethylene-propylene copolymer rubber, the compounding amount of PTFE and / or titanium dioxide in the total amount of the filler material is 10% by weight or more and 32.3% by weight or less, The MT carbon black is compounded in a proportion of 150 parts by weight or less with respect to 100 parts by weight of ethylene-propylene copolymer rubber, The ethylene-propylene copolymer rubber is EPDM.

2. The electrolyte sealing material according to claim 1, which is a molding material of a sealing material used in a battery.

3. An electrolyte sealing member which is a crosslinked molded product of the electrolyte sealing material according to claim 2.

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