JPH0832754B2 - Polymer solid electrolyte - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a solid polymer electrolyte used for primary batteries, secondary batteries, electrochromic displays, electrochemical sensors, iontophoresis, capacitors and other electrochemical devices. is there.

Conventional technology and its problems Conventional polymer solid electrolytes are mainly composed of a cross-linked network of polyether having a molecular weight of less than 2000. In particular, those obtained by crosslinking a polyether modified with a diacrylate or dimethacrylate have a drawback of low flexibility. Therefore, when it is used in a battery or the like, it is easily broken by an external force, which causes a short circuit or the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and has as its object to provide a polymer solid electrolyte having excellent mechanical strength and high ionic conductivity.

In order to achieve the above object, the present invention provides a mixture of a dimethacrylic acid ester or / and a diacrylic acid ester of a copolymer of ethylene oxide and propylene oxide and a monomethacrylic acid ester of a polyether or / and a monoacrylic acid ester. The polymer solid electrolyte is characterized in that the reacted crosslinked network polymer contains an ionic salt, and the copolymer has a molecular weight of 2,000 to 30,000.

The above polymer solid electrolyte is a copolymer of ethylene oxide and propylene oxide which is a random copolymer and / or a block copolymer.

Also, the molar content of propylene oxide in the copolymer is 30
The above-mentioned polymer solid electrolyte having a molybdenum of not more than%.

Further, the above-mentioned polymer solid electrolyte in which the polyether is one or a mixture selected from polyethylene glycol, polypropylene glycol, a copolymer of ethylene oxide and propylene oxide.

Further, the above-mentioned polymer solid electrolyte contains a compound capable of dissolving the ionic salt together with the ionic salt.

Also, the formation of the crosslinked network is the above-mentioned polymer solid electrolyte by irradiation with heat, actinic rays, or ionizing radiation.

Examples Hereinafter, details of the present invention will be described with reference to Examples.

Example 1 70 parts by weight of a dimethacrylic acid ester of a copolymer of ethylene oxide and propylene oxide (containing 20 mol% of propylene oxide, molecular weight: 4200) was added to a monomethacrylic acid ester of methoxylated polyethylene glycol (molecular weight: 25
0) 30 parts by weight was added to make a uniform liquid. This solution and a solution prepared by mixing 9.5 parts by weight of lithium perchlorate with 100 parts by weight of dimethoxyethane are further added, and then 2 parts by weight of benzophenone and 2 parts by weight of triethylamine as a photopolymerization initiator are added and mixed. Cast on top to evaporate the dimethoxyethane. Then, the film was irradiated with a 1 KW ultraviolet lamp in an argon stream from a distance of 15 cm for 30 seconds to obtain a 100 μm film. The ionic conductivity of this membrane was 8 × 10 ⁻⁶ Scm ⁻¹ at 25 ° C. as measured by the complex impedance method.

As a result of bending by 180 ° as a flexibility test, no crack was generated.

Separately, a copolymer of ethylene oxide and propylene oxide (containing 20 mol% of propylene oxide) having a molecular weight of dimethacrylic acid esters of 450, 1100, 2100 and 10,000 was used to obtain a film having a thickness of 100 μm at the same composition ratio. . The results are shown in Table 1.

Example 2 In Example 1, 5 parts by weight of azobisisobutyronitrile was added in place of benzophenone, and a uniform mixed solution was cast, and dimethoxyethane was evaporated. Then 80
Heated at ° C for 1 hour. For molecular weight 4,200,
It has a thickness of 100 μm and its characteristics are ionic conductivity of 7 × 1.
It did not crack even in a 180 ° bending test at 0 ^-6 Scm ^-1 (25 ° C).

Example 3 The same as Example 1 except that a monomethacrylic ester of a methoxylated product of a block copolymer of ethylene oxide and propylene oxide (containing 25 mol% of propylene oxide and a molecular weight of 400) was used in place of the methoxylated polyethylene glycol. did. Molecular weight 4200
No. 1 had a thickness of 100 μm, had an ionic conductivity of 1 × 10 ⁻⁵ Scm ⁻¹ (25 ° C.) and did not crack in the 180 ° bending test.

Example 4 In Example 1, propylene carbonate was used instead of dimethoxyethane. Further, propylene carbonate was left in the film without being evaporated. The other conditions were the same as in Example 1. The results are shown in Table 2.

Example 5 In Example 4, a film having a thickness of 100 μm was obtained by irradiating with 10 Mrad of an electron beam instead of using the photoinitiator benzophenone. Ionic conductivity is 3 × 10 ^-4 Scm ^-1 (25 ° C) for molecular weight of 4200 and 180 °
No cracking occurred in the bending test.

Example 6 In Example 5, a copolymer of ethylene oxide and propylene oxide (containing 20 mol% of propylene oxide,
A diacrylate ester was used in place of the dimethacrylate ester having a molecular weight of 4200).

All conditions were the same except that the electron beam was irradiated at 5 Mrad. A film thickness of 100 μm was obtained. Ionic conductivity is 2 × 10
^{It was -4} Scm ^-1 , and cracking did not occur even in the 180 ° bending test.

Flexibility and strength can be increased by increasing the molecular weight of the copolymer. However, if the molecular weight is too high, the reaction rate will decrease and the productivity will deteriorate. Further, since it is easily crystallized, the conductivity is lowered, which is a problem. Therefore, the molecular weight is 2,000 to 30,000, preferably 2,000 to 5,
000 is the best.

The copolymer of ethylene oxide and propylene oxide is preferably a random or / and block copolymer because it lowers the crystallinity, and the molar content of propylene oxide is most preferably 30 mol% or less.

The ionic salts are LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiC.
F ₃ SO ₃ , LiPF ₆ , LiI, LiBr, LiSCN, NaI, Li ₂ B ₁₀ Cl ₁₀ , LiCF ₃ C
O ₂ , NaBr, NaSCN, KSCN, MgCl ₂ , Mg (ClO ₄ ) ₂ , (CH ₃ ) ₄ NBF ₄ ,
(CH ₃ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (C ₂ H ₅ ) ₄ NI, (C ₃ H ₇ ) ₄ NBr, (n
-C ₄ H ₉ ) ₄ NClO ₄ , (nC ₄ H ₉ ) ₄ NI, (nC ₅ H ₁₁ ) ₄ NI are preferred but not limited.

Further, the compound capable of dissolving the ionic salt,
Tetrahydrofuran, 2-methyltetrahydrofuran,
1,3-dioxolane, 4,4-dimethyl-1,3-dioxolane, γ-butyrolactone, ethylene carbonate, propylene carbonate, butylene carbonate, sulfolane, 3-methylsulfolane, tert.-butyl ether, i
Examples include, but are not limited to, so-butyl ether, 1,2 dimethoxyethane, 1,2-ethoxymethoxyethane, methyl diglyme, methyl triglyme, methyl tetraglyme, ethyl glyme, ethyl diglyme.

EFFECTS OF THE INVENTION As described above, since a polymer solid electrolyte having excellent mechanical strength and high ionic conductivity can be provided, its industrial value is extremely large.

Claims (4)

[Claims] 1. A dimethacrylate or / and a diacrylate of a copolymer of ethylene oxide and propylene oxide, and one or a mixture selected from polyethylene glycol, polypropylene glycol, and a copolymer of ethylene oxide and propylene oxide. A polymer solid electrolyte, wherein the crosslinked network polymer obtained by reacting a mixture of monomethacrylic acid ester and / or monoacrylic acid ester contains an ionic salt, and the molecular weight of the copolymer is 2000 to 30,000. 2. The polymer solid electrolyte according to claim 1, wherein the copolymer of ethylene oxide and propylene oxide is a random copolymer and / or a block copolymer. 3. The polymer solid electrolyte according to claim 1, which contains a compound capable of compatibilizing an ionic salt together with the ionic salt. 4. The polymer solid electrolyte according to claim 1, wherein the crosslinked network is formed by irradiation with heat, actinic rays, or ionizing radiation.