JP3254686B2 - Polymer solid electrolyte - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a solid polymer electrolyte using a copolymer of a phosphazene compound and an oligoalkylene glycol.

[0002]

2. Description of the Related Art In recent years, polymer solid electrolytes have attracted attention as new ion conductors replacing conventional electrolyte solutions from the viewpoint of application to all solid state secondary batteries. In order to increase the ionic conductivity of these solid polymer electrolytes,
It is desirable that the glass transition point of the polymer be low. Therefore, a polymer solid electrolyte using phosphazene as a polymer has recently been proposed. "Journal of American Chemical Society (J. Am. Che
m. Soc), Vol. 106, p. 6854, 1984 "
Describes an example in which an AgSO ₃ CF ₃ salt is melted in polyphosphazene having an oligooxyethylene chain in a side chain to obtain an ion conductivity of about 10 ⁻³ s / cm at 70 ° C. Further, in Japanese Patent Application Laid-Open No. 2-169628,
Using a Li salt of an oligoalkyleneoxy polyphosphazene having a fluoroalkyl sulfone group in a side chain, 30
A method for obtaining an ion conductivity of about 10 ⁻⁵ s / cm at ° C. is disclosed.

[0003]

However, in the conventional polymer solid electrolyte, even the example having the best ionic conductivity is in the range of 10 ^-4 to 10 ^-5 s / cm at room temperature, and can be put to practical use. However, there is a problem that a large current cannot be supplied.

Accordingly, an object of the present invention is to provide a solid polymer electrolyte having a high ionic conductivity at room temperature.

[0005]

The gist of the present invention is that triphosphazene represented by the following general formula (I) and general formula (II)
And a polymer solid electrolyte comprising a complex of a solid solvent in which a substituent represented by the general formula (III) is introduced as a phosphorus side chain of a copolymer with an oligoalkylene glycol represented by the formula (I) and an alkali metal salt: It is to be.

Embedded image HO- (R ₁ -O) _m -H (II) R ₂ -O- (R ₃ -O) _n- (III) (where X is halogen, R ₁ and R ₃ are (CH ₂ ) ₂ ,
Or CH (CH ₃ ) CH ₂ and R ₂ have 1 to 10 carbon atoms
And m and n represent an integer of 1 or more. )

As a method for synthesizing the copolymer of triphosphazene and oligoalkylene glycol used in the present invention, the following method is exemplified. First, an oligoalkylene glycol is dissolved in an organic solvent such as 1,4-dioxane (DIOX) or THF, and N is used to convert the terminal OH group into Na.
Reagents such as aH, Na naphthalene, and Na benzophenone are added and stirred well. This solution is combined with triphosphazene and the catalyst tetraethylammonium bromide (T
EAB) is gradually added to a solution in which an organic solvent such as DIOX or THF is dissolved.
Let react for ~ 10 hours.

The molecular weight of the above copolymer in the present invention is preferably not so large, and is preferably 50,000 or less. This is because if the molecular weight of the copolymer is large, it is difficult to perform thermal motion, and high ionic conductivity cannot be exhibited when the copolymer is combined with an alkali metal salt. Therefore, when synthesizing the copolymer, it is desirable to adjust the reaction ratio between triphosphazene and oligoalkylene glycol. That is, when the reaction ratio of triphosphazene is low, all halogens react with glycol to form a high molecular weight compound, and when the reaction ratio of triphosphazene is too high, crosslinking by glycol does not proceed, and a liquid low molecular weight compound is formed. can get. Therefore, the reaction ratio of triphosphazene to oligoalkylene glycol is preferably in the range of 1: 0.6 to 1: 2. The average molecular weight of the oligoalkylene glycol used in synthesizing such a copolymer is preferably in the range of 100 to 1,000.

The method of reacting the above copolymer with a monoalkyl oligoalkylene glycol having a substituent represented by the general formula (III) is not particularly limited. A method in which an OH group is converted into Na and reacted. In order to completely react the monoalkyl oligoalkylene glycol with the halogen remaining in the copolymer, it is preferable to add the monoalkyl oligoalkylene glycol in an excess of about 1.1 times the molar amount of the copolymer. The molecular weight of the monoalkyl oligoalkylene glycol is preferably not too large, and is preferably in the range of 100 to 1500. When the molecular weight is large, the movement of the alkali metal ion in the solid polymer electrolyte due to thermal motion becomes small. Such a phosphazene-oligoalkylene glycol copolymer in which a monoalkyloxy oligoalkyleneoxy group is introduced as a side chain of phosphorus is used as a solid solvent of a polymer solid electrolyte.

Next, the compounding of the solid solvent with the alkali metal salt will be described. The solid solvent is a volatile organic solvent such as 1,2-dimethoxyethane (DME), THF,
Dissolve or swell in chloroform, anisole, nitromethane, etc. In addition, the side chain oxygen atom 4 ~
A solution obtained by dissolving an alkali metal ion corresponding to one per 40 in a solvent of the same kind is added. Air dry volatile organic solvents,
Alternatively, the residue is dried under reduced pressure, and the residue becomes a composite polymer solid electrolyte. If the number of alkali metal ions is more than one for four oxygen atoms, it becomes difficult for ions to move. If the number of alkali metal ions is less than one for 40 oxygen atoms, the ions themselves are small and the conductivity is reduced.

The kind of the alkali metal salt is not particularly limited. For example, LiCF ₃ SO ₃ , LiPF ₆ , LiC
10 ₄ , LiI, LiBF ₄ , LiSCN, NaCF ₃
SO ₃ , NaPF ₆ , NaClO ₄ , NaI, NaBF
₄ , NaAsF ₆ , KCF ₃ SO ₃ , KPF ₆ , KCl
O ₄ , KI and the like can be mentioned. However, it is recommended to use LiCF ₃ SO ₃ , LiClO ₄ , Li
I, NaCF ₃ SO ₃ , NaClO ₄ , NaI, KCF
₃ SO ₃ , KClO ₄ and KI.

The above-mentioned solid polymer electrolyte can be applied to batteries, capacitors, antistatic agents, electrochromic displays, and the like.

[0012]

The solid polymer electrolyte of the present invention has good mechanical strength by introducing a phosphazene group into a polyether chain, and the oligoether introduced into the side chain of the phosphazene disturbs the structure of the copolymer. Therefore, it is estimated that the glass transition point decreases and the ionic conductivity increases. Next, the present invention will be described in detail with reference to examples.

[0013]

EXAMPLE 1 5 g of commercially available hexachlorocyclotriphosphazene was added to DI
OX was dissolved in 300 ml. This has a molecular weight of about 550
Of both ends of 7.9 g of oligoethylene glycol of NaH
200 ml of a DIOX solution of NaOH that had been converted into Na with the solution was added dropwise over about 30 minutes, mixed well, and then mixed with TEAB 0.1.
75 g was added and stirred at 80 ° C. for 8 hours. After cooling the reaction solution to room temperature, the end of 40 g of monomethyl oligoethylene glycol having a molecular weight of about 350 was similarly converted to Na, and 300 ml of a DIOX solution was added dropwise over about 30 minutes. After mixing well, 0.35 g of TEAB was added. Then 8
Stirred at 0 ° C. for 8 hours. After removing DIOX under reduced pressure, 800 ml of distilled water was added to the residue, mixed well, the precipitate was separated by filtration, the product was further washed with water, dried at 100 ° C. for 24 hours, and triphosphazene and polyethylene were removed. A solid solvent that was a glycol copolymer was obtained. Elemental analysis of this solid solvent showed that the results shown in Table 1 were obtained, indicating that the reaction was carried out at a ratio of triphosphazene, oligoethylene glycol and monomethyl oligoethylene glycol of 1: 1: 4. Take 2.0 g of this and add DME
And further added 0.30 g of LiCF ₃ SO _3, stirred well, and allowed to stand for one day. 80 ° C under reduced pressure
To obtain a rubbery solid electrolyte. Table 2 shows the ionic conductivity of this solid electrolyte at 25 ° C. measured by the impedance method.

Example 2 In place of LiCF ₃ SO ₃ used in Example 1, NaCF was used.
_A solid electrolyte was prepared in the same manner as in Example 1 except that 0.31 g of ₃ SO ₃ was used. When the ionic conductivity at 25 ° C. of the solid electrolyte was measured by an impedance method,
The results are shown in Table 2.

Example 3 Instead of LiCF ₃ SO ₃ used in Example 1, LiI
A solid electrolyte was prepared in the same manner as in Example 1 except that 0.24 g was used. Table 2 shows the ionic conductivity of the solid electrolyte measured at 25 ° C. by an impedance method.

Example 4 The procedure of Example 1 was repeated, except that 14.4 g of oligoethylene glycol having a molecular weight of about 1000 was used instead of the oligoethylene glycol having a molecular weight of about 550 used in Example 1. A solid electrolyte was prepared. When the elemental analysis of this solid solvent was performed, the results shown in Table 1 were obtained, and it was found that triphosphazene, oligoethylene glycol, and monomethyl oligoethylene glycol were reacted at a ratio of 1: 1: 4. In addition, 25 of this solid electrolyte
Table 2 shows the ionic conductivity at ° C. measured by the impedance method.

Example 5 In place of LiCF ₃ SO ₃ used in Example 4, NaCF was used.
_A solid electrolyte was prepared in the same manner as in Example 4 except that 0.31 g of ₃ SO ₃ was used. When the ionic conductivity at 25 ° C. of the solid electrolyte was measured by an impedance method,
The results are shown in Table 2.

Example 6 In place of LiCF ₃ SO ₃ used in Example 4, LiCl ₃
In the same manner as in Example 4 except that 0.24 g of O ₄ was used,
A solid electrolyte was prepared. The ionic conductivity of this solid electrolyte at 25 ° C. was measured by the impedance method.
It became like.

Example 7 A solid solvent and a solid were prepared in the same manner as in Example 1 except that 6.4 g of oligopropylene glycol having a molecular weight of about 445 was used in place of the oligoethylene glycol having a molecular weight of about 550 used in Example 1. An electrolyte was prepared. When the elemental analysis of this solid solvent was performed, the results shown in Table 1 were obtained, and it was found that triphosphazene, oligoethylene glycol, and monomethyl oligoethylene glycol were reacted at a ratio of 1: 1: 4. Table 2 shows the ionic conductivity of this solid electrolyte measured at 25 ° C. by the impedance method.

Example 8 In place of LiCF ₃ SO ₃ used in Example 7, NaCF was used.
_A solid electrolyte was produced in the same manner as in Example 7, except that 0.31 g of ₃ SO ₃ was used. When the ionic conductivity at 25 ° C. of the solid electrolyte was measured by an impedance method,
The results are shown in Table 2.

Example 9 In place of monomethyl oligoethylene glycol having a molecular weight of about 350 used in Example 1, 6.9 g of 2,2-methoxyethoxyethanol and 42.9 g of monomethyl oligoethylene glycol having a molecular weight of about 750 were used. In the same manner as in Example 1, a solid solvent and a solid electrolyte were produced. When the elemental analysis of this solid solvent was performed, the results shown in Table 1 were obtained, and the ratio of triphosphazene, oligoethylene glycol, 2,2-methoxyethoxyethanol, and monomethyl oligoethylene glycol was 1: 1: 2: 2.
It turned out that it reacted. In addition, the solid electrolyte 2
Table 2 shows the ionic conductivity at 5 ° C. measured by the impedance method.

Example 10 In place of LiCF ₃ SO ₃ used in Example 9, NaCF was used.
_A solid electrolyte was produced in the same manner as in Example 9 except that 0.31 g of ₃ SO ₃ was used. When the ionic conductivity at 25 ° C. of the solid electrolyte was measured by an impedance method,
The results are shown in Table 2.

Example 11 The ionic conductivity of the solid electrolyte produced in Example 1 was measured by an impedance method while changing the temperature, and the result was as shown in FIG. FIG. 1 shows the temperature characteristics of the ionic conductivity of the solid electrolyte. The ordinate represents the ionic conductivity in log, and the abscissa represents the Arrhenius plot in which the temperature is represented by 1000 / T. Represents the activation energy.

Example 12 A solid electrolyte was prepared by changing the concentration of the alkali metal salt LiCF ₃ SO ₃ used in Example 1, and the relationship between the alkali metal salt concentration and the ionic conductivity at room temperature was examined. FIG.
It became like. FIG. 2 shows the relationship between the ratio of the number of oxygen atoms of ethylene oxide to the number of alkali metal ions in the solid solvent and the ionic conductivity. The ordinate represents the ionic conductivity, and the abscissa represents the alkali metal salt. It represents the ratio of the number of alkali metal salt ions, which is the concentration, to the number of oxygen atoms in ethylene oxide. Here, the concentration showing the maximum ionic conductivity at room temperature is when the number of oxygen atoms of ethylene oxide is 24 times the number of alkali metal atoms, and the value of the ionic conductivity is 2.0 × 10 ⁻⁴ s. / Cm.

Comparative Example 1 In the same manner as in Example 1 except that 28.7 g of oligoethylene glycol having a molecular weight of 2,000 was used instead of the oligoethylene glycol having a molecular weight of 550 used in Example 1,
A solid solvent and a solid electrolyte were prepared. When the elemental analysis of this solid solvent was performed, the results shown in Table 1 were obtained, and it was found that triphosphazene, oligoethylene glycol, and monomethyl oligoethylene glycol were reacted at a ratio of 1: 1: 4. Table 2 shows the ionic conductivity of this solid electrolyte measured at 25 ° C. by the impedance method.

Comparative Example 2 A solid solvent and a solid electrolyte were prepared in the same manner as in Example 1 except that monomethyl oligoethylene glycol having a molecular weight of about 2,000 was used in place of monomethyl oligoethylene glycol having a molecular weight of 350 used in Example 1. Was prepared. Elemental analysis of this solid solvent gave the results shown in Table 1, where the ratio of triphosphazene, oligoethylene glycol and monomethyl oligoethylene glycol was 1:
It turned out that it reacted by 1: 4. Table 2 shows the ionic conductivity of this solid electrolyte measured at 25 ° C. by the impedance method.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

Solid polymer electrolyte of the present invention exhibits, as a side chain of phosphorus copolymer of Torihosufazen and oligo alkylene glycols, monoalkyl oligo alkylene Oki
Since it is composed of a complex of a solid solvent into which a silicon group has been introduced and an alkali metal salt, it has high ionic conductivity and good temperature characteristics.

[Brief description of the drawings]

FIG. 1 is a graph showing temperature characteristics of ionic conductivity of a solid electrolyte produced in Example 1.

FIG. 2 is a graph showing the relationship between the ratio of the number of oxygen atoms and the number of alkali metal ions in ethylene oxide of the solid electrolyte prepared in Example 1 and the ionic conductivity.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁷ Identification code FI H01M 10/40 H01M 10/40 B

Claims (4)

(57) [Claims] The present invention relates to a triphosphazene represented by the following general formula (I) and a triphosphazene represented by the following general formula (II) having a molecular weight of 100 to 100:
By reacting a monoalkyl oligoalkylene glycol having a molecular weight of 100 to 1500 as a phosphorus side chain of the copolymer with 0 oligoalkylene glycol,
A solid polymer electrolyte comprising a complex of a solid solvent into which a substituent represented by the general formula (III) is introduced and an alkali metal salt. Embedded image (Where X is halogen, R ₁ and R ₃ are (CH ₂ ) ₂ or CH (CH ₃ ) CH ₂ , R ₂ is an alkyl group having 1 to 10 carbon atoms, and m and n are 1 or more. Represents an integer.) 2. A compound according to claim 1, wherein the triphosphazene represented by the general formula (I) and the molecular weight represented by the general formula (II) are 100 to 100.
0 of the oligo alkylene glycol 1: 0.6 to 1:
After obtaining the copolymer by reacting in step 2, the molecular weight is 100 to 1
By reacting 500 monoalkyl oligoalkylene glycols, phosphorus is represented by the general formula (III)
The method for producing a solid polymer electrolyte according to claim 1, further comprising a step of introducing a substituent as a side chain to obtain a solid solvent. 3. The triphosphazene represented by the general formula (I) and the triphosphazene represented by the general formula (II) have a molecular weight of 100 to 100.
By reacting a monoalkyl oligoalkylene glycol having a molecular weight of 100 to 1500 as a phosphorus side chain of the copolymer with 0 oligoalkylene glycol,
A solid solvent for a polymer solid electrolyte into which a substituent represented by the general formula (III) is introduced. Embedded image (Where X is halogen, R ₁ and R ₃ are (CH ₂ ) ₂ or CH (CH ₃ ) CH ₂ , R ₂ is an alkyl group having 1 to 10 carbon atoms, and m and n are 1 or more. Represents an integer.) 4. A compound according to claim 1, wherein the triphosphazene represented by the general formula (I) and the triphosphazene represented by the general formula (II) have a molecular weight of 100 to 100.
0 of the oligo alkylene glycol 1: 0.6 to 1:
After obtaining the copolymer by reacting in step 2, the molecular weight is 100 to 1
By reacting 500 monoalkyl oligoalkylene glycols, phosphorus is represented by the general formula (III)
4. The method according to claim 3, wherein the substituent is introduced as a side chain.
3. The method for producing a solid solvent for a polymer solid electrolyte according to item 1.