JPH02155173A - Electrochemical element - Google Patents

Abstract

PURPOSE:To enhance reliability in repeating and to make the formation of a uniform thin layer possible by dispersing uniform spherical particles in a solid electrolyte. CONSTITUTION:A solid electrolyte in which uniform spherical particles are dispersed is prepared in such a way that if the solid electrolyte solidified or gelled by heat or light is used, a solution in which spherical particles are dispersed is casted, then heat or light is irradiated to the solution. The reliability of an electrochemical element using this solid polymer electrolyte is enhanced by the existence of dispersed spherical substances. The formation of a thin film is made possible and a uniform thin electrolyte layer is easily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a solid polymer electrolyte useful for batteries, electrochromic devices, capacitors, and the like.

[Prior Art] There is a strong desire to solidify electrochemical devices such as batteries and electrochromic devices that utilize electrochemical reactions.

Conventionally, these devices have used electrolyte solutions, which have caused reliability problems due to leakage and volatilization of the solution. As a means to improve leakage resistance and storage stability,
Gelation (Japanese Unexamined Patent Publication No. 82-5506) and solidification (Japanese Unexamined Patent Publication No. 83-58704) of electrolyte solutions have been studied. In addition, a solid polymer electrolyte with high ionic conductivity has been reported [P.

1yver, 14, 589 (1973)] As one means for reliably solving the above problems, research on polymer solid electrolytes that do not contain solvents is also being actively conducted. However, since gel electrolytes lack strength, when applied to thin devices, short circuits between electrodes and destruction of the device are likely to occur. In addition, similar problems tend to occur with respect to solid polymer electrolytes, since materials that generally have high ionic conductivity tend to be soft and lack self-retention. Also, in order to lower the internal resistance of the device, it is necessary to make the electrolyte thinner.
This is a major challenge. As a means to solve these drawbacks, a method has been proposed in which a porous body, a filler, etc. are integrated into a solid electrolyte to solve problems such as short circuits between electrodes of an electrochemical element. (Unexamined Japanese Patent Publication No. 80-19587
8.60 Also, attempts have been made to deposit polyethylene oxide on the electrode substrate as a method of thinning the layer.

However, the former method does not provide a uniform electrolyte layer, causes color unevenness in electrochromic devices, and has insufficient repeat reliability.

In the latter case, although it is possible to make the layer uniform and thin, micro short circuits may occur due to a large area, and the manufacturing method is also difficult.

In the field of batteries as well, there has been an increasing demand for solid thin batteries, but conventional methods are not sufficient to uniformly thin the electrolyte layer.

[Problems to be Solved by the Invention] In view of these circumstances, an object of the present invention is to provide a highly reliable electrochemical device using a solid electrolyte.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventors have conducted extensive research, but in this process, the deterioration of characteristics during repeated use has been found in polymer solids in devices. We assumed that this was due to the fact that a uniform electric field was not applied due to the uneven thickness of the electrolyte layer, and as we continued our research, we found that it was effective to disperse uniform spherical particles into the polymer electrolyte. I discovered something. Furthermore, the present invention has made it possible to reduce the thickness of the membrane, making it easier to obtain a more uniform thin film electrolyte layer.

That is, the present invention is an electrochemical device having a solid electrolyte between at least two electrodes, characterized in that uniform spherical particles are dispersed in the solid electrolyte.

The material of the spherical particles used in the present invention must have no electronic conductivity. Furthermore, if it has ion conductivity, it will not impede the movement of ions and will not deteriorate the device characteristics. In addition, if the spherical particles have ionic conductivity, they will not reduce the carrier ion concentration of the electrolyte salt that can be dissociated into the electrolyte layer, making it possible to supply stable ions, resulting in stable device characteristics. become.

As described above, it is preferable that the material of the spherical particles has ion conductivity, but it is also possible to use a material that does not have ion conductivity.

Specifically speaking, the material of the uniform spherical particles is plastic.
Glass, etc. For example, plastics include phenol resin, divinylbenzene crosslinked product, polymethyl methacrylate, polystyrene, nylon resin, polyethylene, polyethylene oxide, polypropylene oxide, copolymers of these, or polymers having these in their side chains, and inorganic compounds. Soda glass, NASICON
Glass such as 1LISICON, aluminum oxide,
Examples include fine particles such as titanium dioxide.

Furthermore, it is preferable that these spherical particles are microporous to the extent that they maintain their spherical shape, since the inside of the pores can also contribute to ion conduction. When applying these particles to electrochromic devices, it is preferable that they be white or colorless and transparent.

The particle size is preferably 0.1 to 50 μm, more preferably 0.5 to 10 μm. Therefore, the film thickness of the solid electrolyte is also suitably within the range of 0.1 to 50 .mu.-.

Here, uniformity preferably means that the oblateness is 0 to 5% and the sphere diameter distribution is 5% or less.

Examples of methods for producing spherical particles include methods such as emulsion polymerization and suspension polymerization in the case of plastics. In addition, for glass etc., a method of pulverizing agglomerates and granulating them can be mentioned. Furthermore, there are also methods that utilize crystal growth, and the method is not limited to these.

The spherical particles are uniformly dispersed in a single layer in the solid electrolyte membrane, and up to 2000 particles are dispersed in 1 ma+' depending on the particle size. For example, about 50 to 200 particles of 2 to 3 μm are appropriate. As for the density,
O,1Vo1% to 50111o1%, preferably 1Vo
It is best to adjust it between 1% and 20 Vo1%.

The solid electrolyte used in the present invention for dispersing the above-mentioned spherical particles is a material with good ionic conductivity and low electronic conductivity, and is composed of at least a polymer serving as a matrix and an electrolyte salt serving as a carrier. There is.

Furthermore, an organic compound having a high boiling point and high dielectric constant or a low viscosity compound may be added.

Also included are gel-like or solid electrolytes produced by adding, for example, acrylic monomers, epoxy monomers, etc., which are cured by electron beams, light, heat, etc., together with radical generators, to electrolytic solutions.

Examples of the polymer matrix include polyacrylonitrile, polyvinylidene fluoride, polyethylene oxide, polyethyleneimine, or -+Cl1z C
1(0+ (R-H5C0z), -+ CH2C11
Examples include those containing 2Nil+ in the main chain or side chain.

In the present invention, particularly good characteristics were obtained when a crosslinked polyethylene oxide was used.

Electrolyte salts that serve as carriers for polymer solid electrolytes include:
SCN″″ CI-Br-1-BF4- PF5-
AsFi-Cl04SbF6-, CF2S
O3-B(CH3)4B (C2H5) 4-
B (C3H7) 4B (C4H9)-BCC
6Hs) 4- and other anions, and Li2 Na”K”
Alkali metal cations such as (C4HI)4N'' (
Examples include electrolyte salts consisting of cations such as organic cations such as C2H5)4N+.

Compounds added to the solid electrolyte include polyethylene glycol, monomethoxypolyethylene glycol, dimethoxypolyethylene glycol, polypropylene glycol, dimethoxyethane, ethoxymethoxyethane,
Ether compounds such as jetoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, tetrahydrofuran and its derivatives, propylene carbonate, ethylene carbonate, γ-butyrolactone, 1,3-dioxolane, 4-methyldioxolane, sulfolane, 3-methylsulfolane , dimethylformamide, dimethylacetamide and the like. Also,
Two or more types of solvents may be mixed. By adding these compounds, the ionic conductivity was significantly increased.

For example, the following method is used to produce the solid electrolyte in which uniform spherical particles of the present invention are dispersed.

If the solid electrolyte is solidified or gelled by heat or light, it is sufficient to cast the solution in which spherical particles are dispersed and then irradiate it with heat or light. Furthermore, if the solid electrolyte is made of a solid polymer electrolyte such as PEO, spherical particles may be dispersed in a solution containing the solid polymer electrolyte and then cast. To crosslink the electrolyte, a functional group having crosslinking properties may be introduced into the polymer, or a crosslinking agent may be added. In this case crosslinking must be carried out after casting.

Electrodes constituting the electrochemical device of the present invention, particularly functional electrodes, include chromic materials such as tungstic acid, inorganic materials such as battery electrode materials such as manganese dioxide, titanium disulfide, and lithium, and conductive polymers. Examples include organic materials such as materials.

The solid electrolyte in which uniform spherical particles of the present invention are dispersed can also be used as a separator in electrochemical devices. In this case, since the separator itself has ion conductivity, the internal impedance of the element can be reduced. In addition, especially when applied to lithium batteries, lithium dendrites are more difficult to grow than conventional ones, so it can contribute to improving the cycle life.

Next, an electrochemical device was created by using the solid electrolyte in which the uniform spherical particles of the present invention were dispersed and further combining it with an electrode using a conductive polymer as an active material.

The above-mentioned conductive polymer can be synthesized by chemical polymerization, electrolytic polymerization, or plasma polymerization, but especially when manufactured by electrolytic polymerization, the polymer material is usually formed uniformly in the form of a film on the electrolytic electrode. If a current collector is used as an electrolytic electrode, the electrode can be obtained at the same time as the electrode active material is produced, which is convenient for later steps.

Electrolytic polymerization methods are described, for example, in J. EIectrochem, S.
oc,.

It is shown as 130.1508 (19g3). Anodic oxidation polymerization or cathodic reduction polymerization occurs by adding a monomer to an electrolyte solution or solid electrolyte and applying electrolysis by dipping or bringing two electrodes into contact. It is also possible to obtain a composite of a solid electrolyte and a conductive polymer by performing electrolytic polymerization in a solid electrolyte instead of an electrolyte and a solvent. In addition, chemical polymerization methods include, for example, Conductjng Pol
ygers, 105 (1987).

When the electrochemical device is a battery, the battery stores energy by doping a conductive polymer with anions or cations, and releases energy through an external circuit by dedoping. Furthermore, in the battery of the present invention, this doping-dedoping is performed reversibly, so it can be used as a secondary battery.

Since the solid electrolyte of the present invention allows production of a uniform thin film,
In particular, when applied to thin batteries, it is possible to apply a uniform electric field between both electrodes, and it is also possible to prevent minute short circuits due to thinning the film, making it effective for making battery electrodes larger in area and thinner.

Furthermore, the electrochromic device produced according to the present invention utilizes the property of conductive polymers that exhibit color changes upon doping and dedoping.

By using the solid electrolyte of the present invention, there is no micro short circuit and an electric field is uniformly applied, which is effective for increasing the area.

Examples of the conductive polymer used in the present invention include virolthiophene, furan, benzene, azulene, aniline, diphenylbenzidine, diphenylamine, triphenylamine, and conductive or semiconductive polymers obtained by polymerizing derivatives thereof. These polymers form a complex with an electrolyte anion at the same time as they are polymerized, and the anion moves in and out as a result of redox reactions.Polymers that form complexes with cations include polythiophene, polyphenylene, polyphenylene vinylene, polyphenylene xylylene, etc. These compounds form complexes through ion doping, resulting in high electrical conductivity and can store energy.

Examples of ions that form complexes with conductive polymers include:
ClO4-PF5- ASF6SbFh-BF4-,
Paratoluenesulfonate anion, nitrobenzenesulfonate anion, complex anions such as Fe (CN)b-, hydrogen, alkali metals such as Na"K"Li+, (CH3)4N"(C2H5)4N"(C
3H7) Ammonium cations such as 4N+ or A
Examples include Lewis acids such as lCl3 FeC1a CaC13.

In the present invention, the dopant for the conductive polymer constituting the device is preferably the same type of ion as the ion in the solid polymer electrolyte. Therefore, conductive polymers can be synthesized using dopants of the same type as the ions in the solid electrolyte and used as they are in devices, or they can be polymerized and dedoped using ions of a different type, and then It is preferable to use the device by doping again with a dopant of the same type as the ion. The dedoping treatment includes chemical dedoping and electrochemical dedoping, and either method may be used.

Another electrode constituting the device is polyacetylene, polythiophene, which can be doped with cations,
In addition to polyparaphenylene, conductive polymers such as polyphenylene vinylene and polyphenylene xylylene, L t, N
Metals such as aSKSAg, Zn, Al5Cu, or L
Examples include alloys of i and AI% Mg% S tSPb, Gas In, and the like.

These conductive polymers and metals themselves have a current collecting function, but metals such as Nj, AI, Pt1Au, alloys such as stainless steel, metals such as SnO2, InzOz, carbon bodies, polypyrrole, etc. A current collecting material with high electrical conductivity is adhered by pressure bonding, vapor deposition, electroless plating, etc.
It is preferable to improve current collection efficiency.

[Example] The present invention will be explained in more detail with reference to Examples below.

Example 1 A 4-layer laminated 12V battery was fabricated using the following procedure.

1,000 people deposited gold and then 1,000 people deposited lithium on aluminum substrates in Japan. A solution having the following composition was sprayed onto this to form a film. This solution consists of dispersing 2 g of ceramic spheres (average particle size 2 μl) in 10 g of methyl ethyl ketone, and then dispersing PE into 10 g of methyl ethyl ketone.
010 g, L i BF 40.85 g, dibutyltin dilaurate 0.01 g, TDl 0,1 15 g were dissolved. After forming an electrolyte layer from the solution, it was heated at 70° C. for 20 minutes to crosslink PEO. Next, 1000 polypyrroles were grown on the electrolyte layer by plasma polymerization. Furthermore, gold, lithium, electrolyte, and polypyrrole were laminated in this order to create a 12V class battery consisting of a total of 4 cells (Figure 1).

The thickness X of this battery was determined. In addition, constant voltage charging was performed at 15 V, and the leakage current after reaching the theoretical charge amount was constant. In addition, a charge/discharge test was conducted between 10 V and 15 V at 0 and 1 mA to determine the discharge capacity per positive electrode active material.

Example 2 Aniline was polymerized in a 1.5N aqueous sulfuric acid solution containing 0.5M of aniline at a constant current of 1 mA/C using an ITO glass electrode as a reaction electrode.

The amount of current applied was 3C/cs2. After thoroughly washing the obtained electrode with running water, -0.4V vs S in 0.2N sulfuric acid.
, C, and E to perform sufficient dedoping. After thoroughly washing with running water, add 3.5 M LiBF4.
Doping was carried out by applying a potential of 3.8 V to lithium in a propylene carbonate solution in which lithium was dissolved. After drying this, a solid polymer electrolyte with spherical particles dispersed therein was cast from the solution onto the electrode.

The casting solution was an ion-conductive spherical polyethylene glycol diacrylate polymer (average particle size 5 μff) synthesized by emulsion polymerization in 10 g of methyl ethyl ketone.
Disperse 2g of 1) and add 10g of polyethylene oxide triol (PEO) thereto.

It was prepared by dissolving 0.85 g of L i B F 4 , 0.01 g of dibutyltin dilaurate, and 0.85 g of rylene-284-diisocyanate (TDI).

The solution was formed into a film on the composite electrode using an applicator, and a 10 μI metal lithium foil and a glass electrode were pressed onto this to create the battery shown in Figure 2.
Heat at 70°C for 20 minutes while applying a kg of pressure.
EO was crosslinked. The thickness X of this battery was measured. This battery was charged at a constant voltage of 3.7μ, and the leakage current value was measured after reaching the theoretical charge amount. Also, 0.01mA/Cm
A charge/discharge test was conducted at a constant current of 2.5 to 3.7 V to determine the discharge capacity per positive electrode active material.

Example 3 In Example 2, the following casting solution was used to cast onto the electrode.

Casting solution is propylene carbonate tog
2 g of Microvar SP-205 was dispersed in the solution, 9 g of Coconi LiB F 40 was added, and H"CI was heated. Polyvinylidene fluoride was added thereto to prepare the film. After film formation, a 10 μm lithium metal foil was added. Crimp and heat to 80℃ again while applying 1kg of pressure in the direction perpendicular to the electrode surface.
Heated it to create a battery.

Evaluation was performed in the same manner as in Example 2.

Example 4 In Example 2, the amount of current applied during polyaniline polymerization was set to 30i.
C/cm2, and the casting solution was cast onto the electrode using the following:

Casting solution is propylene carbonate 7g51
, 2-dimethoxyethane, 2 g of ceramic spheres (average particle size 2 μm) were dispersed in a mixed solvent of 3 g of 2-dimethoxyethane, and Li
It was prepared by adding 40.9 g of B F and further adding 0.1 g of divinylbenzene as a gelling agent. The solution was cast onto an electrode, heated at 50"C for 1 minute, a glass electrode on which 1 g of lithium was deposited was laminated, and the solution was gelled by further heating at 50"C for 20 minutes to create a battery. .Evaluation was performed in the same manner as in Example 1.

Example 5 In Example 2, the amount of polyaniline polymerized was 30 mC/e■
2, and an electrolyte layer was similarly cast on the obtained polyaniline electrode using the following solution.

The casting solution was prepared by dispersing 2 g of ceramic spheres (average particle size 2 μm) in 10 g of methyl ethyl ketone.
It was prepared by dissolving PE010g5LiBF*0.89g, dibutyltin dilaurate 0.01g% TD10.85g, and propylene carbonate 1.0g. The solution was formed into a film on the composite electrode using an applicator, and
The PEO was crosslinked by heating at ℃ for 20 minutes. Next, 1μ− of lithium was applied to the solid electrolyte surface facing the polyaniline electrode.
A polyaniline-Li battery was fabricated by vapor deposition.

Evaluation was performed in the same manner as in Example 1.

Example 6 A battery was fabricated using the polyaniline electrode shown in Example 2 and a crosslinked film formed in a volume of 1.5 μl from the casting solution shown in Example 2 as a separator, and a metal lithium foil of 1Og as a negative electrode. . As the electrolytic solution, 4.4M Li BF4 was dissolved in a mixed solution of propylene carbonate/dimethoxyethane-7/3. Evaluation was performed in the same manner as in Example 1.

Example 7 Titanium disulfide was used as the positive electrode active material, and the rest was the same as Example 5.
A battery was prepared and evaluated in the same manner as above. The positive electrode was cast from a solvent in which a mixed powder consisting of 10 parts by weight of Ti5z and 1 part by weight of carbon black was dispersed in toluene at a concentration of 10% by weight.

Example 8 Dissolve aniline in 1M hydrochloric acid to a concentration of 0.8M,
A solution of ammonium sulfate dissolved in IM hydrochloric acid to a concentration of 0.25 M was added dropwise thereto, and the mixture was reacted at 10° C. for 2 hours to polymerize polyaniline. This was reduced by stirring overnight in a 20% hydrazine methanol solution. 30 g of the obtained polyaniline and 3 g of carbon black were dispersed in the following electrolyte solution and cast onto a glass electrode substrate. The electrolyte solution is 1:PE in 10g of methyl ethyl ketone.
010g, L i BF40.89g, dibutyltin dilaurate 0.01g, T D 10.85
g, prepared by dissolving propylene carbonate Ig. The polyaniline/solid electrolyte was cast in 30 μl using an applicator and heated at 70° C. for 20 minutes. On top of this, add Micropearl SP-2 to the previous electrolyte solution.
After casting 2 g of 05 dispersed therein and further heating at 70° C. for 20 minutes, a 30 μ-lithium foil and a glass electrode were laminated to produce the battery shown in FIG. 2. Evaluation was performed in the same manner.

Example 9 10cm x 3G on a polyester film with a thickness of 75μI
cm of ITO was deposited. 3-Methylthiophene was added to this TO'rIs electrode in a propylene carbonate solution containing 50M tetrabutylammonium perchlorate by constant current electrolysis using 1OLmAIC112.
A fllClC112 charge was introduced to polymerize. Next, an electrolyte layer was laminated on the electrode by spraying. The electrolyte solution is Micropearl SP in 10g of methyl ethyl ketone.
2g of -214 was dispersed, and PEOlOg, KC
1041.24g, dibutyltin dilaurate 0.0
It was prepared by dissolving 1g of TDIO and 85g of TDIO.

After film formation, PEO was crosslinked by heating at 70° C. for 20 minutes, and gold was vapor-deposited at 1000 A on the surface of the solid electrolyte facing poly-3-methylthiophene to produce an electrochromic device. The device was subjected to doping and dedoping operations at ±5 Ov, and color changes were observed.

Example 10 As the electrolyte solution in Example 9, 2 g of Micropearl 5P-214 was dispersed in 10 g of propylene carbonate, 1.32 g of KClO4 was added thereto, heated to 80°C, and polyvinylidene fluoride was added thereto. It was cast onto a poly 3-methylthiophene film using A glass electrode on which 1,000 gold particles had been vapor-deposited was placed on top of this, and further heated at 70° C. for 20 minutes to improve the adhesion between the electrode and the solid electrolyte, thereby producing the EC device shown in FIG. 3. Evaluation was performed in the same manner.

Comparative Example 1 A battery completely similar to Example 1 except that the electrolyte did not contain spherical particles was prepared and evaluated.

Comparative Example 2 Preparation of EC Device A solid polymer electrolyte containing no spherical particles was cast from a solution onto the electrode shown in Example 9.

The casting solution is PEOIOg.

It was prepared by dissolving 1.24 g of K CI O4, 0.01 g of dibutyltin dilaurate, and 0.85 g of T D I in methyl ethyl ketone tog. The solution was stacked on a composite electrode and heated at 70° C. for 20 minutes while applying a pressure of 1 kg in a direction perpendicular to the electrode surface to crosslink PEO. The obtained electrochromic device (3 cm x 3 cm) was similarly evaluated.

The evaluation results of each of the above examples and comparative examples are shown in Table 1.2.3.

Table-1 Note PEO; Polyethylene oxide DME; Dimethoxyethane PPy: Polyvirol Pc:
Propylene carbonate PAn: polyaniline
γ-BL-γ-Butyrolactone P3MeT: Poly 3-methylthiophene PVDF: Polyvinylidene fluoride Table-2 ■) Discharge capacity per 1 g of positive electrode active material 2) Discharge capacity after mounting coin-type battery CR201B Table-5
(Evaluation of EC device) [Effect of the invention] As explained above, the solid polymer electrolyte of the present invention improves the reliability of an electrochemical device using the solid polymer electrolyte due to the presence of particulate matter dispersed therein. can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the configuration of the secondary battery in Example 1, FIG. 2 is a diagram for explaining the configuration of the secondary battery in Example 8, and FIG. 3 is a diagram for explaining the configuration of the EC element in Example 10. Figure to do.

Claims (1)

[Claims] (1) An electrochemical device having a solid electrolyte between at least two electrodes, characterized in that uniform spherical particles are dispersed in the solid electrolyte.