HK1061865B - Solid electrolyte with high ion conductivity and electrochemical system using the solid electrolyte - Google Patents

Description

Solid electrolyte having high ionic conductivity and electrochemical system using the same

Technical Field

The present invention relates to a proton-conducting solid electrolyte having high ion conductivity or a hydroxide ion-conducting solid electrolyte having high ion conductivity which can be used for a fuel cell or the like, and an electrochemical system such as a fuel cell using the solid electrolyte having high ion conductivity.

Background

An electrolytic device such as a fuel cell, a dehumidifier or an electrolytic hydrogen generator can be generally considered as an electrochemical system using a proton-conducting solid electrolyte. For example, in a solid polymer fuel cell, current and electric energy are obtained according to an electrochemical oxidation reaction of hydrogen supplied to the negative electrode shown in the following formula (1), an electrochemical reduction reaction of oxygen supplied to the positive electrode shown in the formula (2), and a reaction based on proton movement in the electrolyte between the positive electrode and the negative electrode.

(1)

(2)

Fuel cells are known that use methane or the like as a fuel supplied to the anode in place of hydrogen. The reaction proceeds in a similar manner in which electrochemical oxidation of the fuel at the cathode occurs to release protons. Therefore, it can be implemented by using a proton-conductive solid electrolyte.

Electrolytic hydrogen generators may be considered as examples of electrolytic devices. The electrolytic hydrogen generator generates hydrogen according to a reversible reaction of the reactions represented by formulas (1) and (2) in the fuel cell. High-purity hydrogen can be obtained completely on site by using only water and electric energy in the electrolytic hydrogen generator, and a hydrogen tank is not necessary. In addition, since a solid electrolyte is used, it is entirely possible to easily perform electrolysis by introducing pure water containing no electrolyte solute. In the paper industry, a similar system is used to generate hydrogen peroxide for bleaching by using an electrolytic method of the following formula (3) (refer to non-patent publication 1).

(3)

The dehumidifier has a structure in which a proton conductive solid electrolyte membrane is sandwiched between a positive electrode and a negative electrode, in a manner similar to that of a fuel cell or a hydrogen generator. When a voltage is applied between the positive electrode and the negative electrode, water is decomposed into protons and oxygen at the positive electrode according to a reaction described by the following formula (4). The protons migrate through the solid electrolyte toward the negative electrode to perform the reaction described by formula (5). The result is that the protons combine with oxygen in the air to form water. Due to these reactions, water migrates from the positive electrode to the negative electrode to cause a dehumidification reaction atthe positive electrode.

(4)

(5)

It is also possible to decompose water and eliminate moisture by using a similar operating principle as the electrolytic hydrogen generator. There has been proposed an air conditioner (refer to non-patent publication 2) in combination with a wet gas evaporation cold blowing apparatus.

In any of the above systems, a perfluorosulfonic acid type ion exchange membrane represented by Nafion is used as the solid electrolyte. In addition, various sensors, electrochromic devices, and the like are basically based on a system similar to the above-described operation principle. The use of proton-conducting solid electrolytes is possible because these systems can operate when protons migrate in the electrolyte between the pair of positive and negative electrodes, which undergo reduction and oxidation reactions, respectively. Experimental studies on these systems using proton-conducting solid electrolytes have been carried out.

The hydrogen sensor utilizes electrode potential changes based on hydrogen concentration. It has been proposed to use a solid electrolyte such as one composed almost only of polyvinyl alcohol as an electrolyte in a hydrogen sensor (refer to non-patent publication 3). In addition, changes in electrode potential or ionic conductivity may also be applied to the humidity sensor.

When using tungsten trioxide (WO)₃) When an electric field is applied to the negative electrode of the electrochromic device, the electrochromic device generates one color based on the reaction shown in the following formula (6), and thus can be used as a display or a light-shielding glass. In this system, the use of the inorganic compound Sn (HPO) is proposed₄)·H₂O as a solid electrolyte (refer to non-patent publication 4).

(6)

In addition, primary batteries, secondary batteries, optical switches, and electrolyzed water generators can be used as electrochemical systems that operate primarily with proton-conducting solid electrolytes. For example, in a nickel-hydrogen secondary battery, a hydrogen-absorbing alloy is used as a negative electrode, nickel hydroxide is used as a positive electrode, and an alkaline electrolyte is used as an electrolyte. As shown in formulas (7) and (8), protons on the negative electrode undergo electrochemical reduction and oxidation, and hydrogen is stored in the hydrogen storage alloy through charge and discharge processes.

(7)

(8)

As shown in formulas (9) and (10), electrochemical oxidation and reduction of nickel hydroxide occur.

(9)

(10)

When protons or hydroxide ions migrate in the electrolyte, the charge and discharge reactions in the battery continue to progress. Although it is possible to mainly use a proton-conductive solid electrolyte, the prior art uses an alkaline electrolyte solution.

It is proposed to use yttrium as a negative electrode in an optical switch (refer to non-patent publication 5). When an electric field is applied, as shown in formula (11), yttrium is hydrogenated, thereby allowing light to pass therethrough. Thus, it is possible to realize switching between optical transmission and non-optical transmission by an electric field. Although it is possible to mainly use a proton-conducting solid electrolyte in the present system, the prior art uses an alkaline electrolyte solution.

(11)

The electrolyzed water is water produced by an electrolytic reaction. Despite the difference in utility between the reducing side and the oxidizing side, electrolyzed water has the effects of health, sterilization, washing, and promoting crop growth. It is possible to use the electrolyzed water for drinking water, food water, washing water, agricultural water, and the like. When water has an electrolyte, the electrolytic reaction can be promoted. When the electrolyte is soluble in water, it is generally necessary to remove the electrolyte from the water when the water is used. When a solid electrolyte is used as the electrolyte, it is not necessary to remove the solid electrolyte from water.

However, although a perfluorosulfonic acid type electrolyte, which is an electrochemical system using a proton-conductive solid electrolyte, is applied to a fuel cell, an electrolytic hydrogen generator, a dehumidifier, and the like, there is a problem that the production process of the perfluorosulfonic acid type electrolyte is complicated and the price is high. For economic reasons of mass production, it is desirable to produce electrolytes at low prices. However, the low price has a limitation. At present, inexpensive alternatives are desired.

Incidentally, protons migrate at a high speed by the action of water in a solid that is located in a proton-conducting solid electrolyte operating at normal temperature. Therefore, there is a need for alternatives with sufficient water absorption. In particular, since most proton-conducting solid electrolytes are used in a humid environment, the proton-conducting solid electrolyte must also have water resistance. In the conventional perfluorosulfonic acid type electrolyte, water absorbed by highly hydrophilic sulfonic acid groups transfers ions, and a polyvinyl fluoride skeleton structure has the effects of maintaining water resistance, chemical stability and high temperature resistance.

Polyvinyl alcohol is an example of a hydrocarbon polymer having high hydrophilicity and being inexpensive. A material having proton conductivity obtained by mixing phosphoric acid into polyvinyl alcohol can be used as a hydrogen sensor or the like. Although protons migrate at a high speed because polyvinyl alcohol has high water absorption, polyvinyl alcohol is soluble in water, causing a problem of poor material stability in a wet environment.

An inorganic hydrated compound is another known material having high hydrophilicity and good durability and water resistance. For example, P produced by the sol-gel method₂O₅-ZrO₂-SiO₂The hydrated glass can absorb a large amount of water to have high proton conductivity, and it is insoluble in water. The water-containing glass has high stability particularly against inorganic compounds at high temperatures (refer to non-patent publication 6).

However, a common disadvantage of each inorganic hydrated compound is its brittleness. In particular, it is difficult to form each inorganic compound into a thin film, which is required for using a solid electrolyte. In addition, in the sol-gel process, expensive alkoxide metals are used as raw materials, and it is also difficult to reduce the cost of manufacturing equipment because an organic solvent such as alcohol is used in the sol-gel process. Although the above Sn (HPO) may be powdered₄)·H₂O is applied to an electrochromic device, however, it is difficult to make the above-mentioned Sn (HPO)₄)·H₂The membrane made of O has high strength and a gas diffusion limiting function required for a fuel cell or the like. Further, molybdenum phosphate and tungsten phosphate are reported as inorganic compounds having high conductivity (refer to non-patent publication 7). The molecular formula of the molybdenum phosphate can be represented as H₃MoPO₄₀·29H₂And O. The molecular formula of tungsten phosphate can be represented as H₃WPO₄₀·29H₂And O. In addition, ZrO₂·nH₂O、SnO₂·H₂O and Ce (HPO)₄4)₂Are reported to be inorganic compounds of high conductivity (refer to non-patent publication 8). Even with molybdenum phosphate, tungsten phosphate, and other materials, it is difficult to fabricate thin films.

A means proposed is to utilize a combination of a hydrophilic organic polymer and an inorganic compound as a method for overcoming the disadvantages of the hydrophilic organic polymer and the inorganic compound. For example, a proton conductive material obtained by chemically bonding a silicide to polyethylene oxide by nanotechnology is proposed (refer to patent publication 1). Although polyethylene oxide is a cheap and hydrophilic organic compound similar to polyvinyl chloride, it is soluble in water when used alone. However, when polyethylene oxide is combined with a silicide using a sol-gel process, it may be possible to make polyethylene oxide water-repellent. As a result, it is possible to obtain a material having good strength at high temperatures. However, it is difficult to obtain a compounded material by a method other than sol-gel. No other methods related thereto are disclosed. There is a problem in that it is difficult to reduce material costs and manufacturing costs. In addition,an ion conductive material which is made by combining an organic compound such as polyethylene oxide with an inorganic compound such as a silicide and a proton conductive additive such as tungsten phosphate or molybdenum phosphate has been proposed (refer to patent publication 2). However, patent publication 2 discloses only a combination based on a sol-gel process.

All of the above various conventional electrolytes are acidic. The materials used for the electrodes and other system construction materials are limited to acid-proof materials such as noble metals. As a result, it is difficult to reduce the cost of the entire system. When the solid electrolyte is acidic, it is difficult to use the acidic electrolyte for primary batteries, secondary batteries, and optical switches because the electrodes and active materials are degraded by the solid electrolyte. In addition, the alkaline liquid electrolyte leaks when used in a conventional primary battery and a conventional secondary battery.

On the other hand, a gel electrolyte in which an aqueous electrolyte such as an alkaline electrolyte solution is gelled by polyacrylic acid has been proposed (refer to non-patent publication 9). Although the gel electrolyte is not a solid electrolyte in nature, the gel electrolyte has a high ionic conductivity approximately equivalent to that of an aqueous electrolyte. In addition, the gel electrolyte is inexpensive, and leakage of the electrolyte solution can be prevented. However, the gel electrolyte does not have sufficient strength, and its ability to prevent gas or ion diffusion is low. Therefore, the gel electrolyte is used only in a limited range of applications.

(patent publication 1)

Unexamined patent publication Tokkai 2000-90946

(patent publication 1)

Unexamined patent publication Tokkai 2001-35509

(non-patent publication 1)

Electrochemistry (Electrochemistry), 69, No.3, 154-

(non-patent publication 2)

National literature collections of electronic engineering Institute (Collected papers of national Institute of Electrical Engineers), P3373(2000)

(non-patent publication 3)

Sensors and Actuators (Sensors and Actuators), 11, 377-

(non-patent publication 4)

Bull.Chem.Soc.Jpn.，60，747-752(1987)

(non-patent publication 5)

J.Electrochem.Soc.，Vol.143，No.10，3348-3353(1996)

(non-patent publication 6)

J.Electrochem.Soc.，Vol.144，No.6，2175-2178(1997)

(non-patent publication 7)

Chem.Lett.，17(1997)

(non-patent publication 8)

Electrochemistry (Electrochemistry), 69, No.1(2001)

(non-patent publication 9)

Electrochemistry (Electrochemistry), 659-663, No.9(2001)

Summary of The Invention

In order to solve the problems of the conventional ion-conducting solid electrolyte described above, it is an object of the present invention to provide an inexpensive high ion-conducting solid electrolyte utilizing organic and inorganic compounds having water-absorbing properties and water-repellent properties. It is another object of the present invention to provide an electrochemical system utilizing a high ion-conducting solid electrolyte.

In orderto achieve the above object, there is provided a high ion conductive solid electrolyte characterized in that it is composed of an aqueous complex comprising a zirconic acid compound, polyvinyl alcohol and a compound having a carboxyl group, or comprising a zirconic acid compound, polyvinyl alcohol and a metal salt compound having a carboxyl group. After an aqueous solution containing a zirconium salt or an oxyzirconium salt and polyvinyl alcohol and a compound having a carboxyl group or a metal salt compound having a carboxyl group is neutralized by alkali and water as a solvent is removed, a complex is prepared by removing unnecessary salts. In addition, the provided electrochemical system has a high ion-conducting solid electrolyte.

Contains water, and comprises a zirconic acid compound, polyvinyl alcohol and a compound having a carboxyl group, or a complex comprising the zirconic acid compound, polyvinyl alcohol and a metal salt compound having a carboxyl group includes at least one compound selected from the group consisting of aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium and barium. In the neutralization method, the aqueous solution of the zirconium-containing salt or the oxygen-containing zirconium salt includes at least one selected from the group consisting of an aluminum salt, a titanium salt, a calcium salt, a strontium salt, a barium salt and boric acid. Alternatively, the base used to neutralize the aqueous solution comprises at least one alkali metal salt selected from the group consisting of silicates, borates, phosphates, tungstates, molybdates and stannates. The prepared complex comprises at least one compound selected from the group consisting of aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium, and barium. In addition, the ratio of the specific weight (specific weight) to the weight of polyvinyl alcohol is between 0.1 and 0.2. When it is assumed that the form of each carboxyl group in polyacrylic acid or polyacrylic acid metal salt is-COOH, the specific weight is equal to the obtained weight. The ratio of the weight of the zirconic acid compound converted to the weight of zirconium dioxide to the weight of polyvinyl alcohol is not less than 0.05. The ratio of the weight of silicic acid compound converted into silica to the weight of polyvinyl alcohol is between 0.016 and 0.097. The ratio of the weight of the phosphoric acid compound converted into phosphorus pentoxide to the weight of polyvinyl alcohol is not less than 0.023. The complex is subjected to an impregnation treatment with an alkaline solution.

It may be applied to, for example, fuel cells, steam pumps, dehumidifiers, air conditioners, electrochromic devices, electrolyzers, electrolytic hydrogen generators, electrolytic hydrogen peroxide generators, electrolytic water generators, humidity sensors, hydrogen sensors, primary batteries, secondary batteries, optical switching systems, or novel battery systems using covalent metals.

According to the high ion-conductive solid electrolyte and the electrochemical system using the same, it is possible to prepare the ion-conductive solid electrolyte by a simple process in which a zirconium salt or an oxygen-containing zirconium salt and other additive salts are neutralized in a solution containing polyvinyl alcohol and a compound having a carboxyl group or a metal salt compound having a carboxyl group. On the basis of the above-mentioned neutralization and the heat treatment after neutralization, the zirconic acid compound and the compound obtained from the other addition salt undergo a polycondensation reaction. Micro-scale entanglement occurs between these compounds, polyvinyl alcohol and a compound having a carboxyl group or a metal salt compound having a carboxyl group. As a result, a complex can be formed. Since polyvinyl alcohol, a compound having a carboxyl group or a metal salt compound having a carboxyl group, a zirconic acid compound and other added compounds are hydrophilic, the complex has an ability to contain a large amount of water. The contained water acts as a medium for the diffusion of protons or hydroxide ions at high speed.

In the complex of the present invention, an organic component such as polyvinyl alcohol and a compound having a carboxyl group or a metal salt compound having a carboxyl group is closely linked with an inorganic component such as a zirconic acid compound and other additive compounds by hydrogen bonding or dehydration polycondensation. Therefore, although the complex is hydrophilic, it is insoluble in hot water and can maintain stable physical properties under high temperature and humidity environments. Even if the complexing material does not contain a compound having a carboxyl group or a metal salt compound having a carboxyl group, the complexing material may have a considerably high ionic conductivity. When the prepared solid electrolyte is used in applications requiring high ionic conductivity in an alkaline form, such as primary or secondary batteries, the prepared solid electrolyte has insufficient capacity. On the other hand, the solid electrolyte containing the compound having a carboxyl group or the metal salt compound having a carboxyl group has sufficiently high ionic conductivity due to the increase in the concentration of hydroxide ions in a free basic form. The complex has high strength and flexibility, and the complex is easily made into a thin film. Although high ionic conductivity is provided only by the zirconic acid compound, high ionic conductivity can be maintained or improved when the prepared complex includes at least one compound selected from the group consisting of aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium, and barium. Such as silicon and phosphorus components, make the uniformity of the complex good. Thus, the complex can be formed into a thinfilm having good conditions.

Brief Description of Drawings

The graph of fig. 1 is used to explain the relationship between the humidity and the ionic conductivity of each sample. The ion conductivity and humidity relationship diagram of a polyvinyl alcohol/polyacrylic acid/zirconic acid complex electrolyte membrane is shown, and the electrolyte membrane is subjected to alkali impregnation treatment in a solution containing sodium hydroxide, sodium silicate and sodium carbonate.

Preferred embodiments of the invention

A high ion conductivity solid electrolyte and an electrochemical system using the same will be described according to an embodiment of the present invention. In the present invention, the solid electrolyte is composed of a micro-scale complex made of an aqueous solution of polyvinyl alcohol, a compound having a carboxyl group or a metal salt compound having a carboxyl group, a zirconic acid compound, aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium, and barium compounds. The complexes are inexpensive and have high ionic conductivity in the basic form. The present invention provides a proton-or hydroxide ion-conductive solid electrolyte having high water resistance and provides an electrochemical system using the solid electrolyte.

In the present invention, the original aqueous solution contains a zirconium salt or an oxygen-containing zirconium salt and other additives such as an aluminum salt, a titanium salt, a calcium salt, a strontium salt, a barium salt, boric acid, and a compound containing polyvinyl alcohol and having a carboxyl group or a metal salt compound having a carboxyl group.The original aqueous solution is neutralized with a base comprising alkali metal salts of silicic acid, boric acid, phosphoric acid, tungstic acid, molybdic acid and stannic acid. After removing water as a solvent, a complex compound as a solid electrolyte composed of a zirconic acid compound, aluminum, silicon, boron, phosphorus, titanium, tungsten, aluminum, tin, calcium, strontium, barium compound, polyvinyl alcohol, and a compound having a carboxyl group or a metal salt compound having a carboxyl group and water are obtained by removing unnecessary salts.

Embodiments of the present invention will be described below. The invention is not limited to the described embodiments.

(embodiment mode 1)

In preparing the electrolyte membrane, a predetermined amount of zirconium oxychloride octahydrate (ZrCl) was added₂O·8H₂O) was dissolved in 2% by weight, 80cc of a polyvinyl alcohol having an average molecular weight of 120,000-190,000 and a saponification degree of 87-89% and a polyacrylic acid solution having an average molecular weight of 140,000 to obtain an original aqueous solution. Sodium hydroxide of 1M concentration was added dropwise to the original aqueous solution and stirredTo a pH of not less than 10. Thereafter, the solution was poured into two petri dishes having a diameter of 90mm and dried at 50 ℃ to remove water as a solvent. After the drying, the membrane remaining on the petri dish was peeled off from the petri dish, and a heat treatment process of drying in air at 100 ℃ was performed in an oven for 3 hours. In addition, after the heat treatment, the film is cleaned or washed in hot water at 70 to 80 ℃.

The electrolyte membrane obtained by the above process was subjected to an immersion treatment, and the electrolyte membrane was immersed in a sodium hydroxide solution having a concentration of about 0.5M at roomtemperature for 3 hours to promote the formation of an alkali form of the electrolyte membrane. Alternatively, the electrolyte membrane may be subjected to an impregnation treatment in a sodium silicate solution of 0.5M concentration in a similar manner as described above. Alternatively, the electrolyte membrane may be subjected to an impregnation treatment in a sodium carbonate solution of 0.5M concentration in a similar manner as described above. In each case, the samples were dried after the dipping treatment, and the surfaces of the samples were wiped after drying.

The samples obtained in the above manner are represented by the samples No.1 to No.10 in Table 1. The amount of polyacrylic acid is represented in table 1 as the ratio of the specific weight of each sample to the weight of polyvinyl alcohol. When assuming polypropyleneWhen each carboxyl group in the acid is in the form of-COOH, the specified weight is equal to the weight obtained. In addition, Table 1 shows the conversion to zirconium dioxide (ZrO) in each of samples Nos. 1 to 10₂) The amount of zirconic acid compound by weight and is expressed as the ratio of the weight converted to zirconium dioxide to the weight of polyvinyl alcohol in table 1. Samples No.1 to No.5 were not subjected to the dipping treatment.

TABLE 1

Ion conductivity of polyvinyl alcohol/polyacrylic acid/zirconic acid complex electrolyte membrane

No.	Polyacrylic acid and process for preparing polyvinyl alcohol Weight ratio of	Zirconic acid compounds With polyvinyl alcohol In a weight ratio of	Additive compound With polyvinyl alcohol In a weight ratio of	Alkaline impregnation treatment	Ionic conductivity (S/cm)
						1	0	0.13	Is free of	Is free of	5.6×10-7
2	0.05	0.13	Is free of	Is free of	2.1×10-6
						3	0.1	0.13	Is free of	Is free of	1.0×10-5
4	0.2	0.13	Is free of	Is free of	8.4×10-5
						5	0.3	0.13	Is free of	Is free of	9.7×10-5
6	0	0.13	Is free of	NaOH	1.4×10-5
						7	0.05	0.13	Is free of	NaOH	8.8×10-5
8	0.1	0.13	Is free of	NaOH	5.6×10-4
						9	0.2	0.13	Is free of	NaOH	7.7×10-4
10	0.3	0.13	Is free of	NaOH	6.8×10-4
						11	0.1	0.05	Is free of	NaOH	4.2×10-4
12	0.1	0.13	(Al)0.028	NaOH	4.6×10-4
						13	0.1	0.13	(Si)0.016	NaOH	6.0×10-4
14	0.1	0.13	(Si)0.032	NaOH	6.2×10-4
						15	0.1	0.13	(Si)0.065	NaOH	6.8×10-4
16	0.1	0.13	(Si)0.097	NaOH	4.9×10-4
						17	0.1	0.13	(Si)0.15	NaOH	1.7×10-4
18	0.1	0.13	(B)0.006	NaOH	3.7×10-4
						19	0.1	0.13	(P)0.023	NaOH	7.0×10-4
20	0.1	0.13	(Ti)0.044	NaOH	5.7×10-4
						21	0.1	0.13	(W)0.18	NaOH	4.6×10-4
22	0.1	0.13	(Mo)0.078	NaOH	5.0×10-4
						23	0.1	0.13	(Sn)0.082	NaOH	5.9×10-4
24	0.1	0.13	(Ca)0.061	Na0H	3.8×10-4
						25	0.1	0.13	(Sr)0.11	NaOH	5.6×10-4
26	0.1	0.13	(Ba)0.082	NaOH	5.7×10-4
						27	0.1	0.13	(Si)0.032	NaOH	5.8×10-4
28	0.1	0.13	(Si)0.032	NaOH	4.9×10-4

(Al): aluminide (Si): silicide (B): boride compound

(P): phosphide (Ti): titanium compound (W): tungsten compound

(Mo): molybdenum (Sn): tin compound (Ca): calcified substance

(Sr): strontium compound (Ba): barium compound (Na): polyacrylic acid sodium salt

Each sample obtained by compounding a zirconic acid compound whose ratio of the weight converted into zirconium oxide to the weight of polyvinyl alcohol is not less than 0.05 was not dissolved and the shape of the film was maintained even when washed in hot water at not less than 70 ℃ for 1 hour. Each sample had a high water resistance. The comparative film sample prepared by using only polyvinyl alcohol containing no zirconic acid compound in a similar manner as described above was quickly dissolved in hot water. That is, the sample containing only polyvinyl alcohol had low water resistance. In addition, although a sample of the film obtained using only polyvinyl alcohol and polyacrylic acid does not dissolve in hot water quickly, it is impossible to sufficiently maintain the shape of the film. As is readily understood from the above results, the water resistance of polyvinyl alcohol and polyacrylic acid was significantly improved by compounding the zirconic acid compound.

The ion conductivity of each sample film prepared was measured based on the following method. Each sample was cut into a circle having a diameter of 30 mm. The round sample was sandwiched between two platinum round disks each 28mm in diameter. Copper circular disks are located on the outside surface of each circular disk. And they are sandwiched by insulating clips. An alternating voltage of 10mV was applied to the lead wire connected to the copper circular disk by using an LCR meter with frequency fluctuations between 5MHz and 50 MHz. The current and phase angle responses were measured. The ionic conductivity was calculated based on the commonly used Cole-Cole curve semi-circle diameter. Incidentally, during the measurement, each sample was fixed in a container of constant temperature and humidity, the temperature was controlled to 50 ℃ and the relative humidity to 90%. The measurement results are described in table 1.

Samples No.1 to No.5 were not subjected to the alkali solution immersion treatment. Sample No.1, which does not contain polyacrylic acid, has 10^-7Low conductivity of the order of S/cm. On the other hand, when polyacrylic acid is contained, the ionic conductivity is improved. Each sample had 10 when containing polyacrylic acid having a weight-to-weight polyvinyl alcohol ratio of converted polyacrylic acid to polyvinyl alcohol of 0.05^-6High ionic conductivity of the order of S/cm. Each sample had a weight ratio of 10 when polyacrylic acid was contained at a ratio of the converted weight of polyacrylic acid to the weight of polyvinyl alcohol of 0.1 or more^-5High ionic conductivity of the order of S/cm. Samples No.6 to No.10 are sample Nos. 1 to 5, respectively, which were subjected to the dipping treatment with the alkali solution. The ionic conductivity of any of the samples treated by the alkali solution impregnation was improved. Each sample had a weight ratio of 10 when polyacrylic acid was contained at a ratio of the converted weight of polyacrylic acid to the weight of polyvinyl alcohol of 0.1 or more^-4High ionic conductivity of the order of S/cm.

Although it is possible to maintain high ionic conductivity even when the concentration of polyacrylic acid is increased to a weight-to-polyvinyl alcohol weight ratio of converted polyacrylic acid of 0.3, the strength of the film is significantly reduced during hot water washing of production, making it difficult to handle the film. Furthermore, non-uniformity within the film is also improved. At this time, it is preferable that the concentration of polyacrylic acid is such that the ratio of the converted weight of polyacrylic acid to the weight of polyvinyl alcohol is between 0.1 and 0.2. In addition, even when the concentration of zirconic acid was decreased to a value at which the ratio of the weight of the zirconic acid compound converted to the weight of polyvinyl alcohol (sample No.11) was 0.05, it was possible to maintain high ionic conductivity. Incidentally, once the sample is subjected to the acid impregnation treatment instead of the base impregnation treatment, it is difficult to obtain high ionic conductivity as compared with the base impregnation treatment. The ionic conductivity of the acid-impregnated sample was almost the same as that of the sample which was neither acid-impregnated nor base-impregnated.

Samples No.12 to No.26 were obtained by the above procedure in addition to adding aluminum chloride, titanium chloride, strontium chloride, barium chloride or boric acid to the raw solution, and sodium silicate, trisodium phosphate, sodium tungstate, sodium molybdate or sodium stannate to the alkali may be optionally added by neutralization. Incidentally, symbols (Al), (Si), (B), (P), (Ti), (W), (Mo), (Sn), (Ca), (Sr) and (Ba) in Table 1 represent compounds of aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium and barium, respectively. The above additives are respectively converted into Al₂O₃、SiO₂、B₂O₃、P₂O₅、TiO₂、WO₃、MoO₃、SnO₂CaO, SrO and BaO, and the weight ratio of each additive to polyvinyl alcohol is listed. In the case where any one of the additives was added, the ionic conductivity had 10 when subjected to the alkali impregnation treatment^-4Of the order of S/cm. The ionic conductivity can be maintained to a level of or improved as compared to the ionic conductivity of the polyvinyl alcohol, polyacrylic acid, and zirconic acid compounds alone. When a silicate compound is added and the ratio of its weight to the polyvinyl alcohol is 0.016 orMore, it is possible to significantly improve the ionic conductivity and to obtain thin films (sample nos. 13 to 17) having good uniformity. Since the ionic conductivity is reduced when the content of the silicate compound is more than 0.097, it is desirable that the content of the silicate compound is in the range between 0.016 and 0.097. When a phosphorus-containing compound is added and the ratio of the weight thereof to the polyvinyl alcohol is not less than 0.023, it is possible to obtain a film having high ionic conductivity and good uniformity, similarly to the case of the silicate compound.

(embodiment mode 2)

An example of an electrolyte membrane prepared in a manner different from that of embodiment 1 will be described below. A predetermined amount of sodium silicate was dissolved in 2 wt% of the polyvinyl alcohol solution according to embodiment 1. The neutralization was carried out by adding to the solution obtained 1.2M hydrochloric acid containing a predetermined amount of zirconium oxychloride octahydrate (ZrCl)₂O·8H₂O) and polyacrylic acid. Next, the process of the present invention is described,the neutralized solution was poured into two petri dishes having a diameter of 90mm and dried at 50 ℃ to remove water as a solvent. After the drying, the membrane remaining on the petri dish was peeled off from the petri dish, and a heat treatment process of drying in air at 100 ℃ was performed in an oven for 3 hours. In addition, after the heat treatment, the film is cleaned in hot water at 70-80 ℃. The sample produced by the above procedure is represented by No.27 in Table 1. Sample No.27 had 10^-4High ionic conductivity of the order of S/cm.

(embodiment mode 3)

Examples of electrolyte membranes prepared in a manner different from embodiments 1 and 2 will be described below. A predetermined amount of sodium silicate was dissolved in 2 wt% of the polyvinyl alcohol solution according to embodiment 1. The neutralization was carried out by adding to the solution obtained 1.2M hydrochloric acid containing a predetermined amount of zirconium oxychloride octahydrate (ZrCl)₂O·8H₂O). Next, the neutralized solution was poured into two petri dishes having a diameter of 90mm and dried at 50 ℃ to remove water as a solvent. After the drying, the membrane remaining on the petri dish was peeled off from the petri dish, and heat was applied in an oven at 100 ℃ for 3 hours in airAnd (5) processing. In addition, after the heat treatment, the film is cleaned in hot water at 70-80 ℃. The sample produced by the above procedure is represented by No.28 in Table 1. Sample No.28 has 10^-4High ionic conductivity of the order of S/cm.

(embodiment mode 4)

For sample No.14 in table 1, the alkali solution used for the alkali impregnation treatment was changed to sodium silicate of 0.5M concentration and sodium carbonate of 0.5M concentration to prepare a new sample. The ionic conductivities of sample No.14 and the new samples were measured at 50 ℃ and 60% to 90% relative humidity. Fig. 1 shows the relationship between the ionic conductivity and humidity of a complex electrolyte membrane, which is a polyvinyl alcohol/polyacrylic acid/zirconium acid membrane subjected to an alkali impregnation treatment in a sodium hydroxide, sodium silicate or sodium carbonate solution. As is readily understood from fig. 1, the decrease in ionic conductivity of the sample impregnated with the sodium silicate solution or the sodium carbonate solution is moderate at low relative humidity as compared with the sample impregnated with the sodium hydroxide solution.

It is difficult to maintain the film shape of most of the samples shown in table 1 because the strength thereof is significantly reduced during cleaning or washing with hot water once the heat treatment is not performed at 100 ℃. Therefore, in the production process of the electrolyte material according to the present invention, it is preferable that the heat treatment temperature is not lower than 100 ℃.

It is not necessary to use a substance completely identical to the above polyvinyl alcohol. Materials that function substantially in accordance with polyvinyl alcohol may be used. For example, a material in which a part of the hydrocarbon group is substituted with anothergroup can function as polyvinyl alcohol. In addition, materials made by copolymerization of other polymers can also function as polyvinyl alcohol. Furthermore, polyvinyl acetate, which is a raw material of polyvinyl alcohol, can also be used as a starting material because similar effects are obtained by producing polyvinyl alcohol during the reaction of the present invention.

Although various compounds having a carboxyl group or metal salts having a carboxyl group are used in the present invention, it is preferable to use a polymer because the polymer is easily mixed into a complex. Further, polyacrylic acid, metal salts of polyacrylic acid, and the like are suitably used because high density of carboxyl groups is preferable. For example, materials in which some of the carboxyl groups are replaced with other groups can function as polyacrylic acids. In addition, materials made by copolymerization of other polymers can also function as polyvinyl alcohol.

Within the scope of the functions of the polyvinyl alcohol and the compound having a carboxyl group or the metal salt compound having a carboxyl group apparently exhibited according to the present invention, a mixture of any other polymer may be utilized. For example, the other polymer may be a polyolefin polymer such as polyethylene or polypropylene, a polyether polymer such as polyethylene oxide or polypropylene oxide, a fluorinated polymer such as polytetrafluoroethylene or polyfluorovinylene, a polysaccharide such as methylcellulose, a polyvinyl acetate polymer, a polystyrene polymer, a polycarbonate polymer, and an epoxy polymer. In addition, mixtures of other organic or inorganic additives may also be utilized.

Various zirconium salts and zirconyl salts may be used provided that they are soluble in water. And a certain proportion of oxygen and negative ions can be selected at will. In addition, a certain proportion of water can be selected at will.

In the solution of the present invention, water is basically used as a solvent. Other solvents may also be present in amounts less than water. At least one material selected from the group consisting of aluminum salt, titanium salt, calcium salt, strontium salt, barium salt and boric acid is dissolved in the raw solution and zirconium salt or oxygen-containing zirconium salt, although compounds of aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium and barium may be added to the material. Optionally, a metal salt selected from silicic acid, boric acid, phosphoric acid, tungstic acid, molybdic acid and strontium acid is added to the base used for neutralizing the aqueous solution. Various aluminum, titanium, calcium, strontium, and barium salts may be used, provided they are soluble in water. And a certain proportion of oxygen and negative ions can be selected at will. In addition, a certain proportion of water can be selected at will.

As the alkali metal salts of silicic acid, boric acid, phosphoric acid, tungstic acid, molybdic acid and strontium acid, any material irrespective of the kind of alkali metal ion, the alkali metal ion component and the contained water ratio can be used. For example, water glass may be used when silicate is used. These salts may be added as a mixture of at least two salts. In addition, a heteropolyacid salt may be used as a raw material. For example, the heteropolyacid may be selected from tungstophosphoric acid, molybdophosphoric acid, silicotungstic acid, silicomolybdic acid, tungtoboronic acid and molybdoboronic acid, which are previously obtained by combination of tungstic acid or molybdic acid with phosphoric acid, silicic acid or boric acid. Although metaphosphates, secondary phosphates and orthophosphates may be used as phosphates, metaphosphates are not desirable because when silicates or borates are present in the solution, the metaphosphates neutralize the silicates or borates as they go into the original solution.

Any type of base can be used to neutralize the zirconium salt or zirconyl-containing salt. Sodium hydroxide, potassium hydroxide or lithium hydroxide may be used. Further, as described in embodiment 2, when the alkali used for neutralization contains an alkali metal salt of silicic acid, boric acid, phosphoric acid, tungstic acid, molybdic acid or strontium acid in an amount, the acid may be added in advance to the original solution containing a zirconium salt or an oxygen-containing zirconium salt to allow the neutralization reaction to proceed completely. There are two methods of neutralization operation, i.e., adding alkali to the original solution containing zirconium salt or zirconyl salt, or adding the original solution to alkali. Under the conditions of dissolving the polyvinyl alcohol and the compound having a carboxyl group or the metal salt of the compound having a carboxyl group and the zirconium salt or the zirconyl salt, any method is allowed as long as the neutralization reaction can be performed. In the step before the neutralization operation, polyvinyl alcohol and a compound having a carboxyl group or a metal salt of a compound having a carboxyl group may be present in the original solution or the base.

Water as a solvent is removed from the neutralized aqueous solution by heat drying to process the complex into a desired shape such as a film. The complex to be processed is subjected to a heat treatment at a temperature of not less than 100 ℃ to promote the polycondensation reaction of the zirconic acid compound and the co-production (joint production) of the compound of aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium and barium, polyvinyl alcohol and the compound having a carboxyl group or the metal salt of the compound having a carboxyl group. Therefore, the strength, water resistance and high temperature stabilityof the complex can be improved. When the heat treatment is not performed, there is a problem that the strength is lowered in high-temperature water. The heat treatment may be performed in an inert atmosphere or a vacuum atmosphere.

The complex is washed with a solvent such as water before or in a subsequent step of the heat treatment to remove unnecessary salts from the complex. In any electrochemical system using a solid electrolyte, a redox reaction occurs at the electrode. Since free negative ions unsuitable for the solid electrolyte are introduced by the acid at the time of neutralization, which adversely affects the redox reaction, it is necessary to remove unnecessary salt-free ions by washing.

It is preferable that the ratio of the weight of zirconium dioxide to the weight of polyvinyl alcohol of the zirconic acid compound in the complex is defined to be not less than 0.05. Once the weight ratio is less than 0.05, it is difficult to obtain significant water resistance and high ionic conductivity.

When a proton-conducting solid electrolyte or a hydroxide ion-conducting solid electrolyte in an alkaline form is obtained, the resulting complex is subjected to an alkaline solution immersion treatment to completely alkalize the resulting complex. As a result, the ion conductivity can be improved. Any base can be used for the impregnation treatment to basify the resulting complex. For example, sodium hydroxide, potassium hydroxide or lithium hydroxide solutions may be used. Alkali metal salt solutions of silicic acid, boric acid or carbonic acid may also be used. In particular, if an alkali salt of silicic acid or carbonic acid is used, an advantage that the decrease in ionic conductivity is moderated at low relative humidity can be obtained. By using an alkali salt of silicic acid or carbonic acid, even when the electrolyte material is used in air or under a carbon dioxide atmosphere, since neutralization by carbon dioxide hardly occurs, there is an advantage in that deterioration of the solid electrolyte performance is gentle. The alkali impregnation treatment is effective if the inorganic compound contained in the electrolyte is only the zirconic acid compound, or if the inorganic compound contained in the electrolyte has compounds of aluminum, silicon, boron, titanium, molybdenum, tin, calcium, strontium, and barium. It is not necessary to perform the alkali impregnation treatment with an aqueous solution.

The high ion-conductive solid electrolyte obtained according to the present invention exhibits high hydroxide ion conductivity in a high proton or alkaline form, and by alkalinizing the solid electrolyte, a relatively inexpensive material such as nickel can be used as a structural material of electrodes and other systems. Thus, the cost of the entire system can be reduced.

In addition, when the solid electrolyte is alkalized, the solid electrolyte may be applied to a primary battery or a secondary battery. When the electrolyte material of the present invention is used instead of a conventional electrolyte solution, leakage of the solution can be prevented. When the solid electrolyte in an alkaline form is used, a secondary battery which has been difficult to realize in the prior art can be obtained. For example, the secondary battery may be a high energy density battery using a polyvalent metal having a divalent or higher as a negative electrode. A nickel-zinc battery is an example thereof, and this battery is similar to the positive electrode of a nickel-metal hydride battery in that zinc oxide is used as the negative electrode and nickel hydroxide is used as the positive electrode. During the charging of a nickel zinc battery, zinc oxide is reduced to metallic zinc at the negative electrode. During the discharge, zinc is electrochemically oxidized into zinc oxide as shown in the following formulas (12) and (13).

(12)

(13)

Although the nickel zinc battery has a high energy storage density due to zinc having a divalent property, zinc oxide is easily dissolved in an alkaline electrolyte solution. Zinc ions are released from the electrodes. When the released zinc ions are reduced during charging, needle-shaped metallic zinc is formed, which penetrates the separator and causes a short circuit. Also, oxidation of zinc by water in a charged state causes self-discharge to easily occur because the oxidation-reduction potential of zinc is smaller than that of hydrogen. In addition, hydrogen is generated from the zinc electrode during charging, which reduces charging efficiency. Therefore, it is difficult to realize a battery using a liquid electrolyte. When the highly ion-conductive solid electrolyte of the present invention is used, the release of metal ions is limited. Even if the metal ions are slightly released from the electrodes, the released metal ions slowly diffuse from the electrodes. Therefore, the possibility of forming needle-shaped metal is low. Even if needle-shaped metal is formed, the solid electrolyte can prevent its penetration from the negative electrode to the positive electrode. Further, since the reactivity of water contained in the solid electrolyte is poor, self-discharge hardly occurs for a metal having an oxidation-reduction potential smaller than that of hydrogen. The charging efficiency is improved because water electrolysis competing with the reduction reaction of the metal hardly occurs. In other words, the charge efficiency is improved because the reduction reaction of protons hardly occurs. Similar effects to those described above can be produced for a galvanic cell or a nickel-metal hydride cell in terms of the release of metal ions, the diffusion of metal ions and the restriction of needle-shaped metal formation. In addition, an air zinc battery using an air electrode as a positive electrode has the similar advantages as above. Since the permeation of oxygen into the zinc electrode is restricted, a battery which is easily charged can be obtained.

Many metals are divalent or higher. For example, copper, cobalt, iron, magnesium, chromium, vanadium, tin, molybdenum, nickel, tungsten, silicon, boron, and aluminum all have a divalent or higher. Therefore, when the solid electrolyte of the present invention is used, a secondary battery can be obtained using one of the metals described above.

Although the prior art uses a porous separator that absorbs an alkaline electrolyte solution in an alkaline secondary battery, such as a nickel-hydrogen battery, since the electrolyte of the present invention has dual functions of both the electrolyte solution and the separator, it may be unnecessary to use the electrolyte solution or the amount of the electrolyte solution may be reduced. Therefore, the energy density of the battery can be improved. In addition, a thin film type electrode having a large surface area can also be used because the electrolyte of the present invention prevents the occurrence of short circuits in the porous separator even if the electrolyte of the present invention is processed into a thin film.

Since the solid electrolyte of the present invention is made of inexpensive raw materials and employs a simple aqueous solution preparation process, it is inexpensive compared to known perfluorosulfonic acid electrolytes. Further, it is easy to process the solid electrolyte of the present invention into a thin film because the solid electrolyte of the present invention has flexibility as compared with an inorganic solid material. Although the prior art has attempted to combine polyethylene oxide and a silicide,it is difficult to prepare a complex having hot water resistance even with the method of the present invention. It is necessary to employ a high-cost method such as a sol-gel method. However, when polyvinyl alcohol is selected as described in the present invention, an aqueous solution method which is simple to produce and inexpensive can be employed. Also, the solid electrolyte of the present invention has high ionic conductivity in an alkaline form. Therefore, it is not necessary to use expensive noble metals on the electrodes and other components, and a high ion-conductive solid electrolyte can be used on the primary battery and the secondary battery.

Since the solid electrolyte of the present invention has proton conductivity, the solid electrolyte can be applied to a fuel cell, a steam pump, a dehumidifier, an air conditioner, an electrochromic device, an electrolyzer, an electrolytic hydrogen generator, an electrolytic hydrogen peroxide generator, an electrolytic water generator, a humidity sensor, and a hydrogen sensor in a manner similar to a conventional perfluorosulfonic acid ion exchange membrane. Since the above electrolyte also has high ionic conductivity in an alkaline form, the solid electrolyte can be applied to electrochemical systems such as primary batteries, secondary batteries, or optical switching systems. In addition, the solid electrolyte can also be used in a new battery system using a polyvalent metal.

As described above, the present invention is characterized in that a zirconium salt or an oxygen-containing zirconium salt and other additive salts in an aqueous solution containing polyvinyl alcohol, a compound having a carboxyl group or a metal salt compound having a carboxyl group are neutralized with a base, and after removing water as a solvent, unnecessary salts are removed to prepare a complex. The water solution method can be used for easily preparing organic and inorganic complex compounds with water absorption and water resistance, and the high-ion-conductivity solid electrolyte and the electrochemical system using the high-ion-conductivity solid electrolyte can be prepared at low cost.

When neutralization is performed in a solution containing only zirconium salt or zirconic acid-containing salt, the present invention causes micro-scale entanglement between polyvinyl alcohol and zirconic acid compound due to polyvinyl alcohol in the solution, although only the ligation polycondensation reaction of zirconic acid occurs. Since the linking polycondensation reaction is promoted by heating, a complex having strength and flexibility can be obtained. In addition, although the polyvinyl alcohol alone is soluble in hot water, the complex is insoluble in hot water by being tightly bound to the zirconic acid compound. Therefore, the physical properties can be maintained under high temperature and high humidity environments. Also, although the complex has water resistance, since polyvinyl alcohol and the zirconic acid compound have water affinity, the complex can absorb a large amount of water and have high ionic conductivity. Therefore, water contained in a complex composed of polyvinyl alcohol and a zirconic acid compound becomes a medium for high-speed diffusion of protons or hydroxide ions. In addition, the ionic conductivity of the basic form can be greatly improved by adding a compound having a carboxyl group or a metal salt compound having a carboxyl group.

In addition, when the original aqueous solution containing a zirconium salt or an oxyzirconium salt has an aluminum salt, a titanium salt, a calcium salt, a strontium salt, a barium salt, and boric acid, or when the original aqueous solution has an alkali metal salt of silicic acid, boric acid, phosphoric acid, tungstic acid, molybdic acid, or stannic acid, compounds of aluminum, silicon, boron, titanium, molybdenum, tin, calcium, strontium, and barium can be combined. The performance can be improved by combining the third or fourth components described above. Further, since the amount of the zirconium salt or the zirconyl salt is reduced by combining the above third or fourth components, the cost can be reduced.

The solid electrolyte may be applied to electrochemical systems such as fuel cells, steam pumps, dehumidifiers, air conditioners, electrochromic devices, electrolyzers, electrolytic hydrogen generators, electrolytic hydrogen peroxide generators, electrolytic water generators, humidity sensors, hydrogen sensors, primary batteries, secondary batteries, optical switching systems, or new battery systems using polyvalent metals. Can contribute to the low price of the above electrochemical system. In addition, when the electrolytic material is a material in an alkaline form, a low-priced material can be used as a material for an external member such as an electrode within an electrochemical system.

Claims (15)

1. A high ion-conductive solid electrolyte characterized by consisting of an aqueous complex comprising a zirconic acid compound, a polyvinyl alcohol and a compound having a carboxyl group, or comprising a zirconic acid compound, a polyvinyl alcohol and a metal salt compound having a carboxyl group.

2. The high ion-conductive solid electrolyte as claimed in claim 1, wherein the compound having a carboxyl group or the metal salt compound having a carboxyl group is composed of polyacrylic acid or a metal salt of polyacrylic acid.

3. A high ion-conductive solid electrolyte characterized by consisting of an aqueous complex compound containing a zirconic acid compound, a polyvinyl alcohol and a compound having a carboxyl group, or containing a zirconic acid compound, a polyvinyl alcohol and a metal salt compound having a carboxyl group, the complex compound being prepared by neutralizing an aqueous solution of a zirconium-containing salt or an oxygen-containing zirconium salt and a polyvinyl alcohol and a compound having a carboxyl group or a metal salt compound having a carboxyl group with an alkali, and removing water as a solvent, and then removing unnecessary salts.

4. The solid electrolyte of claim 3, wherein the compound having a carboxyl group or the metal salt compound having a carboxyl group is composed of polyacrylic acid or a metal salt of polyacrylic acid.

5. The high ion-conductive solid electrolyte as claimed in any one of claims 3 and 4, wherein a heat treatment at a temperature of not less than 100 ℃ is performed before or after removing the unnecessary salt.

6. The high ion-conductive solid electrolyte as claimed in any one of claims 2, 4 and 5, wherein the ratio of the specific weight, which is equal to the obtained weight when assuming that the form of each carboxyl group in the polyacrylic acid or polyacrylic acid metal salt is-COOH, to the weight of the polyvinyl alcohol is between 0.1 and 0.2.

7. The solid electrolyte as claimed in any of claims 1 to 5, wherein the ratio of the weight of the zirconic acid compound converted into the weight of zirconium dioxide to the weight of polyvinyl alcohol is not less than 0.05.

8. The high ion-conductive solid electrolyte as claimed in any one of claims 1, 2, 3, 4, 6 and 7, wherein the high ion-conductive solid electrolyte comprises at least one compound selected from the group consisting of aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium and barium.

9. The solid electrolyte of any one of claims 3, 4, 5, 6 and 7, wherein the aqueous solution containing a zirconium salt or an oxyzirconium salt includes at least one selected from the group consisting of an aluminum salt, a titanium salt, a calcium salt, a strontium salt, a barium salt and boric acid, or a base for neutralizing the aqueous solution, the base includes at least one alkali metal salt selected from the group consisting of a silicate, a borate, a phosphate, a tungstate, a molybdate and a stannate, and the prepared complex includes at least one compound selected from the group consisting of aluminum, silicon, boron, phosphorus, titanium, tungsten, molybdenum, tin, calcium, strontium and barium.

10. The solid electrolyte as claimed in any of claims 8 and 9, wherein the ratio of the weight of silicic acid compound converted into the weight of silica to the weight of polyvinyl alcohol is between 0.016 and 0.097.

11. The solid electrolyte as claimed in any of claims 8 and 9, wherein the ratio of the weight of the phosphoric acid compound converted into phosphorus pentoxide to the weight of polyvinyl alcohol is not less than 0.023.

12. The high ion-conductive solid electrolyte as claimed in any one of claims 1 to 11, wherein the complex is subjected to an impregnation treatment with an alkaline solution.

13. The solid electrolyte with high ionic conductivity as claimed in claim 12, wherein the alkali solution used for the impregnation treatment is a silicate or carbonate solution.

14. An electrochemical system characterized by using the high ion-conductive solid electrolyte according to any one of claims 1 to 13.

15. The electrochemical system using a high ion conductive solid electrolyte according to claim 14, wherein the electrochemical system is any one of a fuel cell, a steam pump, a dehumidifier, an air conditioner, an electrochromic device, an electrolyzer, an electrolytic hydrogen generator, an electrolytic hydrogen peroxide generator, an electrolytic water generator, a humidity sensor, a hydrogen sensor, a primary battery, a secondary battery, an optical switching system, or a new battery system using a polyvalent metal.