JPH0725839B2 - Polymer solid electrolyte - Google Patents

Description

The present invention relates to a polymer solid electrolyte, and more particularly to a polymer solid electrolyte suitable as an antistatic material, a battery and a material for other electrochemical devices.

[Conventional technology]

In order to apply the solid electrolyte to antistatic materials, batteries and electrochemical devices, not only it has good ionic conductivity, but also excellent film-forming property and good storage stability. It is also necessary that the material be easy to manufacture. However, a solid electrolyte satisfying all such required performances has not been developed so far.

For example, Na-β-Al ₂ O ₃ or Na ₁₊ xZr ₂ P _3- xSixO ₁₂ (0 ≦
It is known that inorganic solid electrolytes such as x ≦ 3) have good ionic conductivity [MS Whittingham et al., Journal of Chemical Physic].
s), 54, 414 (1971), A. Clearfield et al., Solid State Ionics, 9/10, 895 (1983)]
However, it has a fatal defect that mechanical strength is extremely weak and workability to a flexible film is poor.

Polyethylene oxide (hereinafter abbreviated as PEO) are salts of various periodic table I a or Group II a group belonging to the metal ion, for example _{LiCF 3 SO 3, LiI, LiClO} 4, NaI, NaCF 3 SO 3, KCF 3 SO 3
Etc. form a complex that functions as a solid electrolyte and exhibit relatively good ionic conductivity [eg Fast Ion Transport in Solid (P. Vashista) et al.
d), p. 131 (1979)], and also possesses viscoelasticity and flexibility peculiar to polymers, and has good processability and storage stability.

However, the ionic conductivity of PEO has a large temperature dependence, and shows good ionic conductivity at 60 ° C or higher, but the ionic conductivity deteriorates significantly at around room temperature, and it has the versatility of being usable in a wide temperature range. It was difficult to incorporate it into a certain product.

As a method for overcoming the problem that the ionic conductivity of such a PEO-based solid electrolyte is significantly deteriorated at around room temperature, JP-A-62-139266 discloses that PEO having a normal molecular weight has a molecular weight of
A method has been proposed in which low molecular weight PEO of 1,000 or less is mixed and used. However, this method has not yet provided an essential solution to the conventional problems. That is, when a large amount of low molecular weight PEO was mixed, the ionic conductivity near room temperature was improved, but the film-forming property was remarkably deteriorated, making it difficult to form a film.

Furthermore, the method of introducing a low molecular weight PEO into the side chain of polyphosphazene is DFS Shriver.
r) et al. by the Journal of American Chemical Socie
ty), 106, 6854 (1984), but it is difficult to mass-produce this material and it is not suitable for practical use.
Also, the ionic conductivity at low temperatures near room temperature was insufficient.

Furthermore, low molecular weight PEO was introduced into a part of the polysiloxane,
A thin film of this material was used by Watanabe et al., Journal of Power Sources, 20
Vol. 32, p. 327 (1987), but this material was low in ionic conductivity due to the low introduction rate of low molecular weight PEO, and could not be put to practical use.

As a method of improving ionic conductivity by using low molecular weight PEO, a method of introducing a low molecular weight PEO into a side chain of a vinyl polymer by an ester bond has been reported by DJ Banister et al.
r), vol. 25, p. 1600 (1984). However, this material was inferior in film-forming property and had insufficient ionic conductivity near room temperature.

Further, a material obtained by impregnating a cross-linked matrix of an acryloyl compound having PEO as a side chain with low molecular weight PEO is disclosed in JP-A-63
-135477. However, this material also has a problem that the ionic conductivity cannot be sufficiently increased, and this material is also not applicable to a practical device.

[Problems to be Solved by the Invention]

As described above, in the conventional solid electrolyte composed of PEO and alkali metal, the two problems that the ionic conductivity around room temperature is extremely low or the film forming property is significantly inferior cannot be satisfied at the same time, It has been desired to develop a solid electrolyte capable of simultaneously solving these two problems.

Therefore, an object of the present invention is to provide a novel solid electrolyte that exhibits high ionic conductivity even near room temperature and is excellent in film-forming property.

[Means for Solving the Problems]

As a result of intensive studies to solve the above problems, the present inventors have found that at least a monomer represented by the following general formula [I] and / or [II] belongs to at least Group Ia or IIa of the periodic table. It has been solved by a polymer solid electrolyte characterized by being polymerized by heating in the presence of salts of metal ions and lactones to form a polymer matrix.

General formula [I] General formula (II) (In the formula, R ₁ and R ₅ represent a hydrogen atom, an alkyl group, a chlorine atom or a cyano group, and R ₂ and R ₄ represent a lower alkylene group. R ₃ represents a hydrogen atom, an alkyl group, an alkenyl group or an aryl group. , An aralkyl group, a —CO—R ₆ group or a —SO ₂ —R ₆ group, R ₆ represents an alkyl group, an alkenyl group, an aryl group or an aralkyl group, and L represents a z-valent linking group, p,
q is independently an integer of 1 to 30, and z is an integer of 2 or more. ) The polymer compound used in the present invention has a polyalkylene oxide group in its side chain, and thus has a high dielectric constant,
Although it has the ability to dissolve and dissociate the supporting electrolyte, surprisingly, by impregnating the polymer compound used in the present invention with a lactone having high ion conductivity, the ion conductivity near room temperature is surprisingly increased. This is a significant increase compared to the conventionally known PEO polymer solid electrolyte material.

The general formulas [I] and [II] will be described in detail below.

R ₁ and R ₅ may be the same or different and each represents a hydrogen atom, an alkyl group, a chlorine atom or a cyano group, preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms.
R ₂ and R ₄ each independently represent a linear or branched alkylene group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms.
Is a linear or branched alkylene group, particularly preferably --CH ₂ CH _2-, or Is. R ₃ represents a hydrogen atom, an alkyl group which may have a substituent having 1 to 12 carbon atoms, an alkenyl group, an aryl group, an aralkyl group, -CO-R ₆ group or -SO ₂ -R ₆ group, R ₆ represents an alkyl group having 1 to 11 carbon atoms, an alkenyl group, an aryl group or an aralkyl group, and these groups may have a substituent.

Among the groups represented by R ₃ or R ₆ , examples of the substituent of the alkyl group and the alkenyl group are a halogen atom, a cyano group, a sulfo group, a hydroxy group, a carboxyl group, an alkyl group,
Aryl group, aralkyl group, acyloxy group, acylamino group, amino group, sulfonamide group, alkoxy group,
Aryloxy group, alkylthio group, arylthio group, carbamoyl group, sulfamoyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, alulesulfonyl group, alkoxysulfonyl group,
Examples thereof include an aryloxysulfonyl group, a carbamoylamino group, a sulfamoylamino group, a carbamoyloxy group, an alkoxycarbonylamino group and an aryloxycarbonylamino group.

Examples of the substituent of the aryl group and the aralkyl group of R ₃ or R ₆ include an alkyl group having 1 to 20 carbon atoms, a substituted alkyl group,
Halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), hydroxyl group, carboxy group, sulfo group,
Acylamino group (eg, acetamide, benzamide), sulfonamide group, carbamoyl group, acyloxy group, alkoxycarbonyl group, acyl group, alkoxy group (eg methoxy), aryloxy group (eg phenoxy), nitro group, formyl group, alkylsulfonyl Group and arylsulfonyl group.
Examples of the group capable of substituting for the alkyl group include an alkoxy group, an aryloxy group, an alkoxycarbonyl group, an acylamino group, a carbamoyl group, an acyloxy group, an acyl group, and a nitro group. You may.

R ₃ is preferably a hydrogen atom, an alkyl group which may have a substituent having 1 to 8 carbon atoms, an alkenyl group or an aryl group, and examples thereof include a hydrogen atom, methyl, ethyl, hexyl and —CH ₂ CF. ₃ , allyl, phenyl and the like.

p and q are each independently an integer of 1 to 30, preferably 1 to 20, and more preferably 2 to 16. z is 2
It is an integer of the above or more, and preferably an integer of 2 to 4.

L represents a z-valent linking group. When z = 2, L is an alkylene group, an arylene group, an aralkylene group, -O-, -S.
-, Or, these represent a combined linking group. When z = 2, preferred examples of L include —CH ₂ —, CH _{2 2} ,
CH _{2 3} , CH _{2 4} , _{-CH 2 -O-CH 2 -,} - CH 2 CH 2 -O-CH 2 CH 2 -, —CH ₂ —NH—CH ₂ —, CH _{2 2} NHCH _{2 2} , And so on. These groups preferably have 1 to 16 carbon atoms, and these groups may have a substituent. Examples of the substituent include the substituents described for R ₃ .

When z = 3, L is represented by the following general formula [III].

General formula (III) Where A is And R ₈ represents a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or an alkoxy group. L ₂ , L ₃ and L ₄ may be the same or different and have the same meaning as L when z = 2. b, c, and d are 0 or 1 each independently.

When z = 3, a preferable example of L is Etc. These groups may have a substituent, and examples of the substituent include the substituents described for R ₃ .

When z = 4, L is represented by the following general formula [IV].

General formula (IV) Where B is And L ₄ , L ₅ , L ₆ , and L ₇ may be the same or different, and have the same meaning as L when z = 2. t, u,
v and w are 0 or 1 each independently.

As a preferable example of L when z = 4, The polymer compound used in the present invention may contain a repeating unit derived from another monomer component in addition to the repeating unit derived from the general formulas [I] and / or [II]. Examples of other monomer components include acrylic acid, α-
Chloroacrylic acid, α-alacrylic acid (eg, methacrylic acid), amides or esters derived from these acrylic acids (eg, acrylamide, methacrylamide, n-butylacrylamide, t-butylacrylamide, diacetoneacrylamide, methyl) Acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, t-butyl acrylate, iso-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate and β -Hydroxymethacrylate), vinyl esters (eg vinyl acetate, vinyl propionate and vinyl laurate), acrylonitrile , Methacrylonitrile, aromatic vinyl compounds (eg styrene and its derivatives such as vinyltoluene, divinylbenzene, vinylacetopheninone and sulfostyrene), itaconic acid, citraconic acid, crotonic acid, vinylidene chloride, vinyl alkyl ethers (eg vinyl). Ethyl ether), maleic acid ester, N-vinyl-2-pyrrolidone, N-vinylpyridine and 2- and 4-vinylpyridine.

Further, as examples of the copolymerizable monomer _{CH 2 = CH-COOCH 2 nOCO} -CH = CH 2 (n = 2~12), CH 2 = CH-COOCH 2 CH 2 OCH 2 CH 2 OCO-CH = CH ₂ However, the present invention is not limited to these.

The polymer compound used in the present invention contains at least one repeating unit derived from the general formula [I] or [II], and preferably the repeating unit derived from the general formula [I] and the general formula [II] ] And a repeating unit derived from

The repeating unit derived from the general formula (I) is preferably contained in the polymer compound in an amount of 50 mol% or more. More preferably, it is 90 mol% or more.

The repeating unit derived from the general formula [II] is contained in the polymer compound in an amount of preferably 0.5 to 50 mol%, more preferably 1 to 10 mol%.

The polymer compound used in the present invention has the general formula [I]
Alternatively, it may have a plurality of at least one repeating unit derived from [II].

Examples of the monomer represented by the general formula [I] are shown below.
It is not limited to these.

Examples of the monomer represented by the general formula [II] are shown below,
It is not limited to these.

The polymer compound used in the present invention is formed by heat polymerization of a corresponding monomer.

When a polymer compound is formed by heat polymerization of corresponding monomers, the polymerization time can be shortened by adding 0.01 to 5 mol% of a polymerization initiator to all the monomers. Examples of the polymerization initiator include azobis compounds, peroxides, hydroperoxides, redox catalysts, etc., such as potassium persulfate, ammonium persulfate, tert-butyl peroctoate, benzoyl peroxide, isopropyl percarbonate, 2,4-dichlorobenzoyl peroxide. Examples thereof include oxide, methyl ethyl ketone peroxide, cumene hydroperoxide, dicumyl peroxide, azobisisobutyronitrile, and 2,2'-azobis (2-amidinopropane) hydrochloride.

Typical examples of the polymer compound used in the present invention are shown below, but the invention is not limited thereto.

The metal ions belonging to Group Ia or Group IIa of the periodic table used in the present invention are preferably lithium, sodium, and potassium ions, and typical metal ion salts include LiCF ₃ SO ₃ , LiPF ₆ , and LiClO ₄ , LiI, LiBF ₄ , LiCF ₃ C
_{O 2, LiSCN, NaI, NaCF} 3 SO 3, NaClO 4, NaBF 4, NaAsF 6, K
_{CF 3 SO 3, KSCN, KPF} 6, KClO 4, etc. KAsF ₆ and the like.
The Li salt is more preferable. These are one or two
You may mix 1 or more types.

The ratio of the polymer compound used in the present invention to the metal ion salt is preferably such that the polyalkylene oxide unit is contained in a ratio of 2 to 50 times the unit per mol of the metal ion salt. More preferably, the unit is 6 to 30 times. If the ratio is too high, the glass transition temperature (Tg) will rise and the ionic conductivity will decrease, and if the ratio is too low, the effective ion concentration will decrease and the ionic conductivity will also decrease.

It may also be used as a mixture with other electrolytes such as NBu ₄ BF ₄ .

Examples of lactones used in the present invention include γ-butyrolactone, γ-valerolactone, γ-caprylolactone, crotolactone, γ-caprolactone, δ-valerolactone, Etc. It is preferably γ-butyrolactone. These lactones may be used alone or in combination of two or more.

The lactones are used in an amount of 30 to 300 mol%, preferably 40 to 200 mol%, based on all the monomers.

The polymer electrolyte of the present invention is obtained by incorporating the above metal ion salt and lactone compound together with a monomer and polymerizing them to form a polymer matrix.

When forming the polymer electrolyte of the present invention, a solvent that dissolves both the monomer used in the present invention and the salt of the metal ion may be used. Preferred examples of this solvent include solvents having a boiling point of 100 ° C. or lower, such as acetone, acetonitrile, tetrahydrofuran, methyl ethyl ketone, isopropanol, ethanol and dimethoxyethane.

The general method for forming the polymer electrolyte of the present invention is shown below.

A monomer represented by the general formula [I] and / or [II],
Predetermined amounts of salts of metal ions, lactones, and thermal polymerization initiators belonging to Group Ia or IIa of the periodic table were dissolved in an organic solvent having a boiling point of 100 ° C or lower, and cast on a Teflon plate. This casting liquid is stored in an atmosphere of nitrogen gas or argon gas at 40 to 150 ° C (preferably 50 to 120 ° C) at 0.1 to 1
The reaction is carried out for 0 hours (preferably 0.1 to 3 hours), and further 50 to
It was dried under a reduced pressure of 200 mmHg for 0.5 to 2 hours to obtain a colorless and highly transparent thin film.

〔Example〕

 Hereinafter, the present invention will be described in more detail with reference to examples.

EXAMPLE _{1 CH 2 = CH-COO-} CH 2 CH 2 7 OCH 3 4g (10mmol), CH 2
_{= CH-COO-CH 2 CH} 2 4 OCO-CH = CH 2 0.18g (6 × 10
^-4 mol), LiClO ₄ 0.4 g, γ-butyrolactone 2 ml, and benzoyl peroxide 0.03 g were dissolved in acetone 5 ml and cast on a Teflon plate. This casting liquid was polymerized at 80 ° C. for 3 hours in an argon gas atmosphere, and further dried under reduced pressure of 80 mmHg for 1 hour to obtain a colorless and highly transparent thin film No. (1) shown in Table 2. .

Except for changing the amount of γ-butyrolactone or the type of polymer compound (see Table 1 for the monomers constituting the polymer compound) as shown in Table 2, the same procedure as for thin film No. (1) was performed. The thin films of 2) and (3) were obtained.

Further, in the same manner as above, the thin film Nos. Shown in Table 2 were used.
(4) to (30) were obtained.

Further, as comparative examples, thin films (A) and (B) composed of the following compound (E-1) described in JP-A-62-47713,
(C) was obtained.

(E-1) ^{* 1} PEO (Mw ≈ 600,000) / ^{* 1} PEO (Mw = 60
0) = 2/1 mixture ( ^{* 1} made by NOF CORPORATION) Further, as comparative examples, thin films (D), (E), (F) composed of the following compounds described in JP-A-63-135477.
It was created.

Thin film (D); (E-2) / PEO (Mw≈200) = 4/1 (weight ratio) Thin film (E); (E-2) / PEO (Mw≈200) = 4/2 (〃) Thin film (F); (E-2) / PEO (Mw ≈ 400) = 4/2 (〃) For the thin film obtained in this way, a sample consisting of stainless steel / thin film / stainless steel is prepared, and at 0.1 Hz to 100,000 Hz The impedance was measured (25 ° C), and the ionic conductivity was obtained from the Cole-Cole plot.

The film forming property was determined by the following method. A thin film was formed on a glass plate by the casting method, and a scratch resistance test was performed using a 1 mm sapphire needle. The load applied to the needle when the film was broken and scratches remained was determined as the scratch strength.

The evaluation results are shown in Table 2.

As can be seen from Table 2, the thin film No. of the present invention No. (1) to (3
0) is superior to the thin films (A) to (C) of the comparative example in both ion conductivity and film-forming property at around room temperature, and is lower than the thin films (D) to (E) of the comparative example at room temperature. It is clear that the ionic conductivity in the vicinity is excellent.

Example 2 CH ₂ = CH-COO-CH ₂ CH _{2 9} OCH ₃ 4g (3 mmol), CH ₂ =
CH-COO-CH ₂ CH _{2 4} OCO-CH = CH ₂ 0.05 g (1.6 x 10
^-4 mol), LiClO ₄ 0.4 g, γ-butyrolactone 2 ml, and azobisisobutyronitrile 10 mg with methyl ethyl ketone
It was dissolved in 5 ml and cast on a Teflon plate.
This casting solution was thermally polymerized at 90 ° C for 2 hours in an argon gas atmosphere, and further 60 ° C under reduced pressure of 105 mmHg at 80 ° C.
A colorless, highly transparent thin film that was dried for a minute and shown in Table 3.
I got No. (31).

Further, by the same operation, the thin film Nos. (32) to (6
4) was obtained (see Table 1 for monomers constituting the polymer compound).

Also, as a comparative example, Polymer, 25 volumes, 1600
The following polymer (E-3) described on page (1984) is dissolved in acetonitrile and then cast, and then acetonitrile is distilled off under reduced pressure to form a thin film (G),
(H) and (I) were obtained.

The thin film thus obtained was evaluated for ionic conductivity and film formability in the same manner as in Example 1.

The results are shown in Table 3.

As can be seen from Table 3, the thin film Nos. (31) to (64) of the present invention
It is clear that is better than the thin films (G), (H), and (I) of the comparative examples in both ion conductivity and film forming property at room temperature.

〔The invention's effect〕

According to the present invention, it is possible to obtain a polymer solid electrolyte having excellent ionic conductivity near room temperature and good film-forming properties.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01B 1/12 Z H01M 6/18 E 10/40 A

Claims (1)

[Claims] 1. At least a monomer represented by the following general formula [I] and / or [II] is added to at least the periodic table I a.
Alternatively, a polymer solid electrolyte characterized by being polymerized by heating in the presence of a salt of a metal ion belonging to Group IIa and a lactone to form a polymer matrix. General formula [I] General formula (II) (In the formula, R ₁ and R ₅ represent a hydrogen atom, an alkyl group, a chlorine atom or a cyano group, and R ₂ and R ₄ represent a lower alkylene group. R ₃ represents a hydrogen atom, an alkyl group, an alkenyl group or an aryl group. , An aralkyl group, a —CO—R ₆ group or a —SO ₂ —R ₆ group, R ₆ represents an alkyl group, an alkenyl group, an aryl group or an aralkyl group, and L represents a z-valent linking group, p,
q is independently an integer of 1 to 30, and z is an integer of 2 or more. )