JP3161881B2 - Oligoethyleneoxy polyphosphazenes having cyclic carbonate groups and their production and use - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel oligoethyleneoxypolyphosphazene having a cyclic carbonate group, a process for producing the same, and a use thereof. The compounds of the present invention can be used as electrolytes in electrochemical devices such as all-solid primary and secondary batteries, solid-state display devices, sensors, and capacitors.

[0002]

2. Description of the Related Art Conventionally, liquid electrolytes have been used for electrochemical devices such as primary batteries, secondary batteries, and electrochromic display elements. However,
The liquid electrolyte has a problem of long-term reliability because the liquid electrolyte easily leaks to the outside of the component and elution of the electrode substance is apt to occur. On the other hand, the solid electrolyte does not have the above-mentioned problems, and therefore can simplify the structure of the device, and furthermore, the weight is reduced by thinning,
There are advantages such as miniaturization is possible.

[0003] These features meet the demand for smaller and lighter, more flexible shapes, and higher reliability of various electronic components with the development of electronics. Solid electrolyte materials include inorganic substances such as those described in Tetsuichi Kudo and Kazuo Fueki, "Solid Ionics" (Kodansha Scientific, 1986), for example, stabilized zirconia,
Silver iodide, silver rubidium iodide, β-alumina and the like are well known. Some of these inorganic solid electrolytes include
Some exhibit ionic conductivity comparable to liquid electrolytes, but have the fatal drawback of low decomposition voltage, and are often difficult to mold and form into any shape, and have properties as a material Is extremely insufficient. On the other hand, organic polymers are lighter, have viscoelasticity, and are more flexible than inorganic materials, and have the characteristics of being excellent in moldability and workability.As a polymer solid electrolyte, for example, Naoya Ogata, Polyethers such as poly (ethylene oxide) and poly (propylene oxide), as described in “Conductive Polymers”, pp. 95 to 150 (Kodansha Scientific, 1990).
Polyesters such as poly (ethylene succinate) and poly (β-propiolactone), poly (ethylene imine),
Matrix polymers such as polyimines such as poly (N-methylethyleneimine) have been reported. Further, a solid electrolyte composition comprising a combination of the matrix polymer and an inorganic ionic salt such as lithium and sodium, and a composition using such a composition are disclosed in, for example,
Nos. 169873, 2-295070, 3-129603 and the like have been reported. However, these polymer solid electrolytes have only a considerably lower ionic conductivity than conventional organic liquid electrolytes using, for example, a mixed liquid of propylene carbonate and dimethoxyethane.

On the other hand, as an attempt to obtain a polymer solid electrolyte having high ionic conductivity, a polymer solid electrolyte using poly (phosphazene) having poly (ethylene oxide) having a low molecular weight introduced into a side chain has been disclosed in Japanese Patent Laid-Open No. 61-1986. No. 254626, poly (phosphazene) with an organic group containing an amide bond in the side chain
Japanese Patent Application Laid-Open No. 63-186766 discloses a polymer solid electrolyte using poly (phosphazene) having a branched low molecular weight poly (alkylene oxide) introduced into a side chain. No. 252762. However, although these polymer solid electrolytes have good film-forming properties, they have not yet reached a level comparable to the ionic conductivity of the aforementioned organic liquid electrolyte.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a novel polyphosphazene having a cyclic carbonate group in a side chain as a polymer solid electrolyte having excellent ion conductivity, a method for producing the same, and a use thereof.

[0006]

The present invention relates to an oligoethyleneoxy polyphosphazene having a cyclic carbonate group on a side chain substituent represented by the formula (I).

[0007]

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[Wherein X and Y are the same or different,
It represents group (A) or group (B).

[0009]

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—O (CH ₂ CH ₂ O) kR (B) R represents a methyl group, an ethyl group, a propyl group, or an allyl group, which may be the same or different. h, and
k indicates the average number of repetitions of the ethyleneoxy unit, and 0 ≦ h ≦ 15 and 0 ≦ k ≦ 15, respectively. m is 3 to 200
Indicates an integer of 000. However, in at least one of the m repeating units, one of X and Y is a group (A), and the other is a group (B). ]

The polyphosphazene of the present invention is, for example, a polyphosphonitrile chloride represented by the general formula (II)
I) and the compound of the general formula (IV) are reacted once to obtain a substitution reaction product, and then the acetonide group on the side chain substituent is hydrolyzed to form a diol derivative, followed by a ring closure reaction And introducing a carbonate group.

[0012]

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(In the formula, m is an integer of 3 to 200,000.)

MO (CH ₂ CH ₂ O) kR (III) (where k represents the average number of repeating ethyleneoxy units, and 0 ≦ k ≦ 15. M represents an alkali metal.)

[0015]

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(Where h represents the average number of repeating ethyleneoxy units, and 0 ≦ h ≦ 15. M represents an alkali metal.)

The present invention also relates to a battery using the above-mentioned oligoethyleneoxypolyphosphazene having a cyclic carbonate group of the present invention.

A feature of the present invention is that the basic structure is based on a polyphosphazene in which an oligoethyleneoxy side chain having high ionic affinity is arranged on an inorganic polymer skeleton having a main chain of phosphonitrile having excellent flexibility and low-temperature characteristics. By introducing a highly polar cyclic carbonate group into the polymer, the dissociation of the electrolyte salt is promoted, and the number of mobile ions is increased to obtain a solid polymer electrolyte having excellent ion conductivity.

Hereinafter, the present invention will be described in detail. The oligoethyleneoxy polyphosphazene having a cyclic carbonate group on the side chain substituent represented by the general formula (I) used in the present invention is synthesized as follows. That is, a dichlorophosphonitrile polymer obtained by ring-opening polymerization of hexachlorotriphosphonitrile is prepared by adding an alkali metal alcoholate of a corresponding oligoethylene glycol monoalkyl ether and a corresponding oligoethylene glycol monopropyl acetonide prepared in advance. It can be produced by performing a quantitative reaction. The reaction can be carried out by mixing the components at about 10 ° C. or lower using a conventional organic solvent, for example, tetrahydrofuran, diglyme, toluene, etc., and subsequently heating and refluxing for several hours. Sodium or the like can be used. The acetonide compound thus obtained is hydrolyzed according to a conventionally known method to obtain a diol derivative as shown in the following formula (V).

[0020]

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(Where h represents the average number of repeating ethyleneoxy units, and 0 ≦ h ≦ 15)

For example, "The New Experimental Chemistry Course" edited by The Chemical Society of Japan.
14 ", pages 2495 to 2516, Maruzen (1978), in the presence of a mineral acid such as hydrochloric acid, acetic acid, p-toluenesulfonic acid, or an acid such as an ion exchange resin (H ⁺ type). Can be hydrolyzed. The diol derivative thus obtained can be converted into an oligoethyleneoxy polyphosphazene having a target cyclic carbonate group according to a conventionally known method. The ring closure reaction as shown in the following formula (VI) is described in “The 4th Edition Experimental Chemistry Course 20”, edited by The Chemical Society of Japan, No. 272.
Page 276, Maruzen (1992) and the like.

[0023]

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(Where h represents the average number of repeating ethyleneoxy units, and 0 ≦ h ≦ 15)

For example, a method based on a transesterification reaction using dimethyl carbonate, diethyl carbonate or the like, a method based on a ring closure reaction using phosgene, diphosgene, triphosgene, methyl chloroformate, ethyl chloroformate, p-nitrophenyl chloroformate and the like. And the like. The inorganic salt or the like generated by the reaction is finally removed from the polymer and used for the polymer solid electrolyte.

The thus obtained polymer of the present invention has excellent adhesion to the negative and positive electrode members, and is dissolved in an ether solvent such as dimethoxyethane and tetrahydrofuran.
By drying after coating, a thin film can be easily formed.

Among the organic solid electrolytes of the present invention, in particular, a solid electrolyte comprising an oligoethyleneoxy polyphosphazene having an allyl group, or a mixture thereof, and an electrolyte salt increases the mechanical strength of the electrolyte membrane by crosslinking. It is possible to Crosslinking can be performed by a usual method, that is, a method by heating, a method by irradiation with ultraviolet rays, or the like. Furthermore, it is also possible to prepare a solid electrolyte membrane by adding a solvent. As the solvent, for example, dimethoxyethane, ethoxymethoxyethane, diethoxyethane, dimethoxypropane, alkoxypolyalkylene ether,
Linear or cyclic ethers such as dioxane, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, methoxytetrahydrofuran, ethyl acetate, γ-butyrolactone, γ-valerolactone, δ-valerolactone, diethyl carbonate, diethyl carbonate, ethylene carbonate,
Propylene carbonate, linear or cyclic esters such as butylene carbonate, acetonitrile, nitriles such as methoxypropionitrile, methylpyrrolidone, cyclic amides such as cyclohexylpyrrolidone, sulfolane, or phosphate esters, or a mixture thereof. Can be used.

The electrolyte salt used in the battery using the oligoethyleneoxy polyphosphazene having a cyclic carbonate group of the present invention is not particularly limited, but the cation has at least Li ⁺ , Na ⁺ , K ⁺ , Cs ⁺ , and Ag. ⁺ , And the anions are BF ₄ ⁻ , AlCl ₄ ⁻ , PF ₆ ⁻ , As
_{^{F 6 -, ClO 4 -,}} CF 3 SO 3 -, Cl -, Br -, I -, SC
N ^- one or more electrolyte salts selected from the group of, for example,
LiBF ₄ , LiAlCl ₄ , LiPF ₆ , LiAsF ₆ , LiCl
O ₄ , LiCF ₃ SO ₃ , LiF, LiCl, LiBr, LiI,
LiSCN, NaBr, NaI, NaSCN, KI, NaSC
N, AgNO _{3 and the} like can be suitably used. Li
ClO ₄ , LiCF ₃ SO ₃ , LiBF _{4 and the} like are particularly preferable.

As the positive electrode active material, transition metals, chalcogens, metal oxides, which are significantly different in ionization potential from alkali metals, and those doped with a small amount of alkali metal ions are suitable. Examples of the transition metal include Ni, Sn, Co, and Fe, but Sn is most preferable. Chalcogens include CuS, FeS ₂ , Fe
Se ₂ , TiS ₂ , TiSe ₂ , VS ₂ , VSe ₂ , MoS ₂ , Mo
Se _{2 and the} like are preferable. As the metal oxide, Mn
O ₂ , CoO ₂ , V ₂ O ₅ , MoO ₃ , WO _{3 and the} like are preferred.

On the other hand, as the negative electrode active material, in addition to alkali metals such as lithium, sodium and potassium,
Al, Pb, Sn alloys, graphite, polyacetylene, and the like can be cited as alkali metal doping substances.

The positive electrode and the negative electrode made of these materials are formed into, for example, a thin plate shape, and both are bonded to each other with the above-mentioned polymer solid electrolyte, whereby the solid electrolyte battery of the present invention can be formed.

[0032]

EXAMPLES The present invention will be described below in detail with reference to examples, but it should not be construed that the invention is limited thereto.

Example 1 Hexachlorocyclotriphosphonitrile was put in a polymerization tube, connected to a vacuum line, heated and melted, solidified by cooling, and
After degassing was repeated several times, the tube was sealed under reduced pressure and polymerized at 250 ° C. for about 8 hours. Unreacted hexachlorocyclotriphosphonitrile was removed by sublimation under reduced pressure to obtain a white rubbery dichlorophosphonitrile polymer. 0.25 unit mol of the dichlorophosphonitrile polymer was dissolved in about 500 ml of dioxane.

On the other hand, [ethylene glycol mono (2,2-dimethyl-1,3-dioxane-4-
Ylmethyl) ether] 0.35 mol and methoxyethanol
0.35 mol was dissolved in 500 ml of tetrahydrofuran, and a hexane solution of 0.60 mol of n-butyllithium was added dropwise at 10 ° C. or lower for 30 minutes. After the dichloroxonitrile polymer dioxane solution prepared above was added dropwise to this alcoholate solution at 10 ° C. or lower for about 15 minutes, the reaction solution was heated and refluxed for 5 hours. After completion of the reaction, the reaction solvent was distilled off under reduced pressure, poured into water and neutralized with dilute hydrochloric acid. This polymer aqueous solution is dialyzed against pure water using a cellophane membrane, desalted and purified to remove low-molecular-weight impurities.
0.5 g was obtained.

[0035]

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0.20 unit mol of the polymer obtained above is dissolved in 300 ml of tetrahydrofuran, and 0.1N hydrochloric acid 30
0 ml was added and reacted at 60 ° C. for about 2 hours. After neutralization with an aqueous sodium hydroxide solution, tetrahydrofuran was distilled off under reduced pressure. This polymer aqueous solution was dialyzed against pure water using a cellophane membrane, and desalted and purified to remove low-molecular-weight impurities to obtain 48.5 g of a slightly yellow rubbery substance.

To 0.19 unit mol of the diol derivative obtained above, 1.90 mol of diethyl carbonate and 0.02 mol of potassium carbonate were added and reacted under reflux for 5 hours. After the reaction,
Poured into ether to precipitate the polymer. Further, reprecipitation was repeated to purify the polymer to obtain 48.6 g of a rubbery substance.

The results of various analyzes of this polymer are as follows. In the IR spectrum, absorption of a carbonyl group of a cyclic carbonate group was observed at 1780 cm ^-1 . The result of elemental analysis is the theoretical value (%) calculated from the theoretical structural formula [Formula 12].
C: 38.44, H: 5.74, N: 4.98, P: 11.01,
The analytical values were C: 38.27, H: 5.93, N: 4.81, P: 11.29, and the values were in good agreement.

As a result of the GFC analysis of this polymer shown in FIG. 1, the weight average molecular weight was 137 × 10 ⁴ and Mw / Mn was 11.3. From the above results, it was confirmed that the desired product was obtained.

[0040]

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Example 2 The average value of k of HO (CH ₂ CH ₂ O) kR is about 7, and R is M
The reaction was carried out in the same manner as in Example 1 using an alcohol e (methyl) and an alcohol wherein the average value of h in Chemical formula 13 was about 7. After purification, 48.6 g of a rubbery substance was obtained. The results of various analyzes of this polymer are as follows. In the IR spectrum, absorption of a carbonyl group of a cyclic carbonate group was observed at 1780 cm ^-1 .

[0042]

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On the other hand, in ¹ H-NMR, 3.3 (—CH ₃ ),
_{3.4~3.8 (-CH 2 O -),} 4.0~4.3 (POCH 2 -),
_{4.4~4.5 (-CHC H 2 O -)} , 4.85ppm (-C H CH 2
O-) and ³¹ P-NMR showed a peak based on polyphosphonitrile at -5.2 ppm (vs. 85% phosphoric acid), and the active chlorine concentration was 0.01% or less. On the other hand, the result of elemental analysis is a theoretical value (%) C calculated from the theoretical structural formula [Chemical Formula 14].
Analyzed values were 48.67, H: 8.12, N: 1.88, P: 3.86 in comparison to 48.94, H: 7.97, N: 1.73, P: 3.82, and the values were in good agreement. As a result of GFC analysis of this polymer shown in FIG. 2, the weight average molecular weight was 161 × 104 and Mw / Mn was 11.
I got one. From the above results, it was confirmed that the desired product was obtained.

[0044]

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Examples 3 to 13 Table 1 shows the reaction conditions and analysis results of the polymer synthesized in the same manner as in Example 1.

[0046]

[Table 1]

Example 14 Table 2 shows the results obtained by dissolving a lithium salt in the polymers obtained in Examples 1 to 13 and measuring the AC conductivity at 30 ° C. by the complex impedance method.

[0048]

[Table 2]

EXAMPLE 15 10 parts of lithium perchlorate was dissolved in 100 parts of the oligoethyleneoxypolyphosphazene having a cyclic carbonate group and an allyl group obtained in Example 13 by ultrasonic treatment at 40 ° C. or less, and the electrolyte was dissolved. I got This electrolyte is transparent ITO
The mixture was sandwiched between the electrodes, and irradiated with light from a 400 W high-pressure mercury lamp to cause a cross-linking reaction of polyphosphazene to form an electrolyte membrane having a cross-linked structure. The value of AC conductivity by the complex impedance method was 2.8 × 10 ⁻⁴ S / cm (30 ° C.).

Example 16 Oligoethyleneoxy polyphosphazene having a cyclic carbonate group and an allyl group synthesized in Example 13
Parts were sonicated at 40 ° C. or lower with 60 parts of propylene carbonate and 10 parts of lithium perchlorate to obtain an electrolyte. This electrolyte is sandwiched between transparent ITO electrodes,
Irradiation with light from a 400 W high-pressure mercury lamp was performed to perform a cross-linking reaction of polyphosphazene, thereby forming an electrolyte membrane having a cross-linked structure. The value of AC conductivity by the complex impedance method is
It showed 3.0 × 10 ⁻³ S / cm (30 ° C.), and showed an ionic conductivity one order of magnitude higher than that of an electrolyte containing no propylene carbonate.

Example 17 To 50 parts of the oligoethyleneoxypolyphosphazene having a cyclic carbonate group obtained in Example 2 were added 40 parts of an oligoethyleneoxypolyphosphazene having a methyl group represented by the following formula (VII) and LiBF ₄ 10 parts were subjected to ultrasonic treatment at 40 ° C. or lower to dissolve, thereby obtaining an electrolyte. The value of AC conductivity of this electrolyte according to the complex impedance method is 2.9 × 10 ^-4 S / cm.
(30 ° C.).

[0052]

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Example 18 As a specific example of the battery according to the present invention, a sheet type thin film battery as shown in FIG. 3 was produced. The external dimensions are adapted to a business card size of 5.5 cm x 9 cm, and the thickness is about 0.1 mm.

First, the amorphous V ₂ O ₅ obtained by the rapid quenching method was
% Aqueous solution, and 6.66 g is uniformly applied to a central portion of 36 cm ² of a 5.5 cm × 9 cm, 20 μm thick stainless steel plate [Nippon Steel Corporation]. This was dried at 80 to 100 ° C. for about 1 hour to form a film, and then vacuum dried at 220 ° C. for 5 hours to obtain a positive electrode member. On this member, a dimethoxyethane solution of a polymer solid electrolyte based on polyphosphazene having a cyclic carbonate group described in Examples 2 and 14 is applied, and dimethoxyethane is removed to form an electrolyte film.

On the other hand, in an argon atmosphere, a polyolefin-based sealing material was adhered to a peripheral portion of 5.5 cm × 9 cm, and a thickness of 20 cm.
A 30 μm-thick lithium foil is pressure-bonded to a central portion 36 cm ² of a μm stainless steel plate to separately produce a negative electrode member. This bipolar member was thermocompression-bonded under vacuum to produce a sheet battery. The open circuit electromotive voltage of this battery is 3.90 V, and 1.0 mA at 30 ° C.
As a result of the constant current discharge shown in FIG. 4, the discharge capacity density until the voltage was reduced to 2 V was 170 Ah / kg with respect to the positive electrode active material. FIG. 5 shows the state of the battery up to 10 cycles when the charge / discharge repetition test was performed. In the curve portions, a and a 'represent a rest period after charging, b represents a discharging state, c represents a rest period after discharging, and d represents a charging state. The charge and discharge efficiency of the present battery was 99% or more, and it was confirmed that the present battery system including the electrolyte was a secondary battery having excellent charge and discharge characteristics.

[0056]

As described above, the oligoethyleneoxy polyphosphazene having a novel cyclic carbonate group of the present invention has a dramatic improvement in ionic conductivity by dissolving a salt, as compared with the prior art, It is a polymer solid electrolyte that can pass a practically usable current.

Accordingly, the oligoethyleneoxypolyphosphazene having a cyclic carbonate group of the present invention and a mixture thereof can be used as a polymer solid electrolyte in an electrochemical system such as an all-solid primary and secondary battery, a solid display element, a sensor, and a capacitor. It can be applied to a wide range of fields such as electric, electronic, chemical, and medical applications as an electrolyte for devices.

[Brief description of the drawings]

FIG. 1 is a diagram showing the results of a GFC analysis of Example 1.

FIG. 2 is a diagram showing the results of a GFC analysis of Example 2.

FIG. 3 is a schematic sectional view of a specific example of the battery of the present invention.

FIG. 4 is a diagram showing the results of constant current discharge at 0.5 mA at 30 ° C. of the battery of Example 18.

FIG. 5 is a view showing a result of conducting a charge / discharge test of the battery of Example 18.

[Explanation of symbols]

1 ...... V ₂ O ₅ film 2 ...... metal lithium 3 ...... organic solid electrolyte membrane 4 ...... stainless steel foil 5 ...... sealant

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 79/00-79/04 CA (STN)

Claims (3)

(57) [Claims] 1. An oligoethyleneoxy polyphosphazene having a cyclic carbonate group on a side chain substituent represented by the general formula (I). Embedded image [Wherein, X and Y are the same or different and each represents a group (A) or a group (B). Embedded image _{-O (CH 2 CH 2 O)} kR (B) R is a methyl group, an ethyl group, a propyl group, or an allyl group, these may be different from one in the same. h, and
k indicates the average number of repetitions of the ethyleneoxy unit, and 0 ≦ h ≦ 15 and 0 ≦ k ≦ 15, respectively. m is 3 to 200
Indicates an integer of 000. However, in at least one of the m repeating units, one of X and Y is a group (A), and the other is a group (B). ] 2. A polyphosphonitrile chloride represented by the general formula (II) is reacted with a compound represented by the general formula (III) or (IV) to once obtain a substitution reaction product, 2. The process for producing a polyphosphazene according to claim 1, wherein the acetonide group on the group is hydrolyzed to form a diol derivative, followed by a ring closure reaction to introduce a carbonate group. Embedded image (In the formula, m is an integer of 3 to 200,000.) MO (CH ₂ CH ₂ O) kR (III) (where k represents the average number of repeating ethyleneoxy units, and 0 ≦ k ≦ 15. M is an alkali metal.) (In the formula, h represents the average number of repeating ethyleneoxy units, and 0 ≦ h ≦ 15. M represents an alkali metal.) 3. A battery using the polyphosphazene according to claim 1.