Electrolyte composition and battery

Abstract

To provide an electrolyte composition having low thermal conduction characteristics, which hardly cause thermal uniformity with the elapse of time, and a cell capable of obtaining high output and having excellent stability against repetition of heating and cooling.SOLUTION: An electrolyte composition contains at least one redox pair and hollow particles. The average particle size of the hollow particles is 200 μm or less. The electrolyte composition preferably contains 0.1 mass% or more and 30 mass% or less of the hollow particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electrolyte composition and a battery. [Background technology]

[0002] In recent years, advances in IoT sensor technology have accelerated the development of independent power sources, with particular attention being paid to thermoelectric conversion batteries that utilize waste heat and body heat. While inorganic heterogeneous metal junction batteries are the mainstream for thermoelectric conversion batteries, they have the drawback of having a low Seebeck coefficient, an indicator of thermoelectric conversion efficiency. Meanwhile, organic thermoelectric conversion batteries with a high Seebeck coefficient that utilizes the oxidation-reduction of ions have been attracting attention in recent years.

[0003] Non-Patent Document 1 reports an organic thermoelectric conversion system that uses an ionic liquid electrolyte to provide heat resistance, but has the problem of low battery voltage output.

[0004] Patent Document 1 reports that a coin-type battery using polyethylenedioxythiophene (PEDOT) / polystyrene sulfonate (PSS) and ferrocyanide ions / ferricyanide ions can obtain an output of 5 μW at a temperature difference of 25 K and 11 μW at a temperature difference of 40 K. However, it is predicted that the output will be even smaller when the temperature difference is small, such as between body temperature and ambient temperature.

[0005] One method for increasing the output of thermoelectric batteries is to increase the temperature difference between the battery's electrodes. However, when one electrode is in contact with a heat source, the temperature of the other electrode, which is not in contact with the heat source, also changes due to thermal conduction through the electrolyte composition inside the battery, presumably resulting in the temperature difference between the electrodes disappearing over time. Furthermore, when the electrolyte composition is liquid, convection occurs within the electrolyte composition, which may eliminate the temperature difference between the electrodes more quickly. For example, when a battery is attached to a human body, if one electrode is in contact with the body and the other electrode is exposed to ambient air at a temperature lower than body temperature, the temperature of the electrode on the ambient air side gradually increases due to the influence of body temperature, eventually becoming higher than the ambient temperature. More specifically, when a battery is attached to a human body with a body temperature of 37°C in an ambient temperature of 25°C, the temperature difference between the electrodes immediately after attachment is 12°C. However, as the battery gradually warms due to body temperature, the final temperature difference between the electrodes becomes less than 12°C. Therefore, in order to increase the output, it is important to suppress the heat conduction inside the battery and maintain the temperature difference.

[0006] One effective way to maintain the temperature difference is to increase the viscosity of the electrolyte composition inside the battery and reduce its fluidity. However, simply reducing the fluidity of the electrolyte composition can also reduce ion diffusivity, raising concerns about reduced output. Furthermore, for organic thermoelectric batteries with a high Seebeck coefficient that utilizes ion redox, there has not yet been sufficient research into how to effectively generate a temperature difference. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2018 / 079325 [Non-patent literature]

[0008] [Non-Patent Document 1] “Seebeck coefficients in ionic liquids prospects for thermo-electrochemical cells”, TJAbraham, et al., Chem. Commun., 47, (2011) pp.6260-6262. Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide an electrolyte composition with reduced thermal conduction, which makes it difficult for heat to be uniformly distributed over time, and to provide a battery that can obtain high output and has excellent stability when repeatedly heated and cooled. [Means for solving the problem]

[0010] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention relates to an electrolyte composition containing at least one redox couple and hollow particles, wherein the hollow particles have an average particle size of 200 μm or less.

[0011] The present invention also relates to the above-mentioned electrolyte composition, wherein the hollow particles are contained in an amount of 0.1% by mass or more and 30% by mass or less in the electrolyte composition.

[0012] The present invention also relates to the above electrolyte composition, which further contains a compound having at least one functional group selected from a carboxy group, a hydroxyl group, a guanidino group, and salts thereof.

[0013] The present invention also relates to the above-mentioned electrolyte composition for use in a battery.

[0014] The present invention also relates to a battery comprising the above electrolyte composition.

[0015] The present invention also relates to the above battery which is a thermochemical battery. [Effects of the Invention]

[0016] The present invention makes it possible to provide an electrolyte composition with suppressed thermal conduction that makes it difficult for heat to be uniformly distributed over time, and a battery that can obtain high output and has excellent stability when repeatedly heated and cooled. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing the structure of a thermoelectric voltage evaluation device. [Figure 2] FIG. 2 is a cross-sectional view showing the structure of a thermoelectric voltage evaluation device. [Figure 3] 10 is an example of a diagram for calculating a thermoelectric voltage; [Figure 4] FIG. 1 is a schematic diagram showing the structure of a battery output density evaluation device. [Figure 5] FIG. 2 is a cross-sectional view showing the structure of a battery output density evaluation device. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below. In this specification, unless otherwise specified, "%" means "% by mass." Furthermore, in a numerical range, "xx or more, xx or less" is expressed as "xx to xx." Furthermore, unless otherwise specified, "parts" means "parts by mass," and "%" means "% by mass." Furthermore, "a functional group selected from the group consisting of a carboxy group, a hydroxyl group, a guanidino group, and salts thereof" may be abbreviated as "functional group (A)." Furthermore, "a compound having at least one functional group (A)" may be abbreviated as "compound (A)."

[0019] <Electrolyte composition> The electrolyte composition of the present invention is an electrolyte composition containing at least one redox couple and hollow particles, characterized in that the hollow particles have an average particle diameter of 200 μm or less. The presence of the redox couple exhibits thermoelectric conversion ability, and the inclusion of hollow particles with an average particle diameter of 200 μm or less can impart thermal insulation without reducing ionic conductivity, resulting in the development of a high Seebeck coefficient (hereinafter also referred to as thermoelectric voltage), and as a result, high output can be obtained when used as a battery electrolyte.

[0020] <Redox pair> The redox couple will now be described. In this specification, the term "redox couple" refers to a pair consisting of two types of ions capable of undergoing an oxidation-reduction reaction. While the redox couple is not particularly limited, from the viewpoints of chemical stability and battery performance, it preferably contains a metal element or a halogen element, and more preferably contains at least one pair selected from the group consisting of iron(II) ion / iron(III) ion, cobalt(II) ion / cobalt(III) ion, and iodide ion / triiodide ion. In particular, it is even more preferable to contain at least one pair selected from the group consisting of iodide ion and triiodide ion, ferrocyanide ion and ferricyanide ion, ferrocene and ferrocenium ion, and cobalt tris(bipyridine)(II) and cobalt tris(bipyridine)(III), and a pair consisting of ferrocyanide ion and ferricyanide ion is particularly preferable.

[0021] The redox couple is preferably contained in a total amount of 10 to 40%, more preferably 10 to 35%, and even more preferably 10 to 30% in the electrolyte composition. A content of 10% or more improves battery performance, while a content of 40% or less suppresses the occurrence of precipitation due to temperature changes, making it possible to stabilize the battery output when used in a battery electrolyte.

[0022] <Hollow particles> Hollow particles will now be described. In this specification, hollow particles refer to particles having a hollow portion. The hollow portion may be a structure having one hollow portion in an outer shell, such as a core-shell structure, or a structure having multiple hollow portions within a particle, such as a porous structure. There are no particular restrictions on the shape of the particle or the hollow portion. Furthermore, the hollow portions may be independent or continuous.

[0023] It is preferable that a gas is present inside the hollow portion. There are no particular limitations on the gas, and examples of the gas include air, nitrogen, oxygen, carbon dioxide, argon, and hydrogen. When the gas is present in the electrolyte composition, the thermal conductivity of the electrolyte composition is significantly reduced, making it easier to maintain a temperature difference.

[0024] The average particle size of the hollow particles contained in the electrolyte composition is 200 μm or less, more preferably 180 μm or less, and even more preferably 130 μm or less. An average particle size of 200 μm or less allows the hollow particles to be uniformly dispersed in the electrolyte composition, imparting stability to the electrolyte composition when heated and cooled repeatedly. If the hollow particles are not uniformly dispersed, repeated heating and cooling of the electrolyte composition can cause the hollow particles to locally aggregate, reducing the thermal conductivity reduction effect and decreasing output. There is no particular lower limit for the average particle size of the hollow particles, but a size of 50 nm or more is preferred. A size of 50 nm or more allows the particles to maintain their mechanical strength and suppresses chipping and cracking of the hollow particles during the production of the electrolyte composition or when the battery is used in a high-temperature environment.

[0025] The bulk density of the hollow particles is 0.9 g / cm 3 Preferably, it is 0.8 g / cm or less. 3 It is more preferable that the concentration is 0.7 g / cm or less, and furthermore, 0.7 g / cm or less. 3 It is more preferable that the bulk density is 0.9 g / cm or less. 3 The bulk density of the electrolyte composition is not particularly limited, but is generally 0.08 g / cm. 3The bulk density can be measured by the method of JIS R1628.

[0026] The content of hollow particles in the electrolyte composition is preferably 0.1 to 30% by mass, more preferably 0.5 to 25% by mass, and even more preferably 1 to 20% by mass. A content of 0.1% by mass or more improves the heat insulating properties, making it easier to create temperature differences, increasing the battery voltage and improving output. Furthermore, a content of 30% by mass or less maintains ionic conductivity and improves battery output. Furthermore, even when the electrolyte composition is repeatedly heated and cooled, aggregation of hollow particles is suppressed, improving the stability of repeated output.

[0027] The material of the hollow particles is not particularly limited, and organic hollow particles or inorganic hollow particles can be used. Materials that can be used as organic hollow particles include polystyrene, poly(meth)acrylic acid ester, polyvinyl alcohol, polyimide, polyethylene, polypropylene, polyester, etc., but are not limited to these examples and may be used alone or in combination of two or more. Materials that can be used as inorganic hollow particles include, for example, silica, glass, ceramic, metal, etc., but are not limited to these examples and may be used alone or in combination of two or more. Organic hollow particles and inorganic hollow particles can be used alone or in combination, but from the viewpoints of thermal stability and mechanical strength, it is preferable to use inorganic hollow particles.

[0028] Examples of inorganic hollow particles include the Q-CEL (registered trademark) series (product names: 5020, 5020FPS, 7014, 7040S) manufactured by Potters Ballotini as sodium silicate glass hollow particles, the Sphericel (registered trademark) series (product names: 25P45, 60P18, 110P8, CP01, CP03) manufactured by Potters Ballotini as sodium silicate glass hollow particles, Glass Bubbles (product names: K1, K15, K20, K25, K37, S22, S28HS, S32HS, S38, S60HS, VS5500, iM16K, iM30K) manufactured by 3M as soda-lime silicate glass hollow particles, and Ceramic Multi (product names: 5020, 5020FPS, 7014, 7040S) manufactured by Potters Ballotini as ceramic hollow particles. Examples of such hollow particles include the Cellular series (product names: CMC-20, CMC-15) manufactured by Taiheiyo Cement Corporation, E-SPHERES (product names: SLG, SL300, SL150, SL125, SL75) manufactured by Taiheiyo Cement Corporation, and the Extendospheres (registered trademark) series (product names: SG, TG) manufactured by Potters Ballotini Co., Ltd., but are not limited to these examples. They may be used alone or in combination of two or more types.

[0029] The shape of the hollow particles is not particularly limited, and shapes such as spheres, elongated spheroids, cylinders, and polyhedrons such as rectangular parallelepipeds can be used.

[0030] The average particle size of hollow particles can be determined using a scanning electron microscope. The average particle size of hollow particles referred to in this specification is determined by measuring the particle sizes of 100 randomly selected hollow particles using a scanning electron microscope, and taking the median diameter (d50, number-based) as the average particle size. However, if the hollow particles have a shape other than spherical, the length in the minor axis direction is used as the particle size of the particle.

[0031] <Additives> The electrolyte composition of the present invention preferably further contains a compound (sometimes collectively referred to as "compound (A)") having at least one functional group selected from the group consisting of a carboxyl group, a hydroxyl group, a guanidino group, and salts thereof (sometimes collectively referred to as "functional group (A)"). The inclusion of compound (A) generates ionic interactions and hydrogen bonds with the redox pair, resulting in a change in state before and after the oxidation-reduction reaction, thereby improving the thermoelectric voltage. The guanidino group refers to a group represented by -NH-C(=NH)-NH2. The functional group selected from these salts may be ionized.

[0032] Examples of compounds having a carboxy group include acrylic acid, alginic acid, carboxymethyl cellulose, gellan gum, and polymers thereof. Examples of compounds having a salt of a carboxy group (which is synonymous with the salt of a compound having a carboxy group) include lithium salts, sodium salts, potassium salts, calcium salts, magnesium salts, and the like of the compounds having a carboxy group. Examples of compounds having a hydroxyl group include agar, agarose, agaropectin, cyclodextrin, etc. Examples of compounds having a salt of a hydroxyl group (which is synonymous with a salt of a compound having a hydroxyl group) include metal alkoxides such as aluminum isopropylate and titanium tetraisopropoxide, and 4-nitrophenol sodium. Examples of compounds having a guanidino group or a salt thereof include guanidine, aminoguanidine, arginine, guanidine carbonate, nitroguanidine, N-acetylguanidine, etc. Examples of compounds having a salt of a guanidino group (which is synonymous with a salt of a compound having a guanidino group) include guanidinium chloride, guanidinium iodide, guanidinium bromide, guanidinium thiocyanate, guanidine phosphate, aminoguanidine hydrochloride, arginine hydrochloride, arginine acetate, etc. The compound (A) is not limited to the above examples, and may be used alone or in combination of two or more kinds.

[0033] The electrolyte composition of the present invention preferably contains 0.5 to 30 mass %, more preferably 1.0 to 25 mass % of compound (A). When the compound (A) is contained in an amount of 0.5 mass %, a high voltage and improved output can be achieved, and when the compound (A) is contained in an amount of 30 mass % or less, ionic conductivity is maintained and the battery output is improved.

[0034] <Solvent> The electrolyte composition may further contain a solvent. The solvent is not particularly limited and can be appropriately selected from known solvents. Examples include water and the following organic solvents. Examples of organic solvents include aromatic solvents such as toluene and xylene; alcohol solvents such as n-butyl alcohol, propylene glycol monomethyl ether, diacetone alcohol, and ethyl cellosolve; ester solvents such as ethyl acetate, butyl acetate, and cellosolve acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; carbonate solvents such as ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and fluoroethylene carbonate; and dimethylformamide. However, the examples are not limited to these examples, and one or more of these solvents can be used in combination. From the viewpoint of the solubility of the redox couple, it is preferable that the solvent contains a protic solvent, and it is more preferable that the solvent contains water.

[0035] The electrolyte composition may be in any form of a liquid, sol, gel, or solid state, but is preferably in a sol, gel, or solid state from the viewpoints of battery safety and hollow particle dispersibility.

[0036] The electrolyte composition may further contain a leveling agent, a thickener, a surface conditioner, an antifoaming agent, a rheology control agent, etc., within the range that does not impair the effects of the present invention.

[0037] <Battery> The battery of the present invention comprises the electrolyte composition of the present invention. More specifically, the battery is constructed by sandwiching the electrolyte composition of the present invention between at least a pair of electrodes. The electrolyte composition and battery of the present invention can be suitably used in a thermochemical battery, a type of thermoelectric conversion battery. A thermochemical battery is a thermoelectric conversion battery that utilizes the temperature dependence of the redox equilibrium potential, and contains at least one pair of redox couples in the electrolyte composition. Known electrodes can be appropriately selected and used, including metal electrodes such as platinum, gold, copper, and silver; carbon electrodes such as carbon nanotubes, graphene, and graphite; and conductive polymer electrodes such as polythiophene, polyacetylene, polyaniline, and polypyrrole. However, the electrodes are not particularly limited, and one or more types can be used in combination. These electrodes may be formed alone or on a substrate such as a plastic film. Furthermore, an ion-permeable membrane or other electrolyte composition may be laminated between the electrode and the electrolyte composition of the present invention. [Example]

[0038] The present invention will be described in more detail below with reference to examples, but the technical scope of the present invention is not limited by these examples. In the examples, "parts" means "parts by mass" and "%" means "% by mass".

[0039] <Production of hollow particles> [Manufacturing Example 1] Using the example sample A8 described in Japanese Patent No. 5466801 as a reference, the average particle size was 200 μm and the bulk density was 0.25 g / cm 3 Silica-based hollow particles were prepared and designated as hollow particles (A1).

[0040] [Manufacturing Example 2] With reference to Example 3 of Japanese Patent No. 6953114, an average particle size of 55 nm and a bulk density of 1.2 g / cm 3 Silica-based hollow particles were prepared and designated as hollow particles (A2).

[0041] [Manufacturing Example 3] With reference to Example 2 of Japanese Patent No. 6595898, an average particle size of 2 μm and a bulk density of 2.0 g / cm 3 Silica-based hollow particles were prepared and designated as hollow particles (A3).

[0042] [Manufacturing Example 4] With reference to Example 5 of WO 2021 / 085189, the average particle size was 310 nm and the density was 0.65 g / cm 3 Styrene / divinylbenzene hollow particles were prepared and designated as hollow particles (A4).

[0043] [Manufacturing Example 5] With reference to Example 6 of WO 2021 / 085189, an average particle size of 520 nm and a density of 0.65 g / cm 3 Styrene / divinylbenzene hollow particles were prepared and designated as hollow particles (A5).

[0044] [Comparative manufacturing example 1] With reference to Comparative Example 1 described in Japanese Patent No. 5466801, an average particle size of 270 μm and a bulk density of 0.25 g / cm 3 Silica-based hollow particles were prepared as comparative hollow particles (B1).

[0045] <Measurement of average particle size> The average particle size was measured using an electron microscope. Using a scanning electron microscope (JSM-7800, manufactured by JEOL Ltd.), the particles were photographed at an accelerating voltage of 5 kV, and the particle diameter in the minor axis direction of 100 randomly selected particles was measured. The median diameter (d50, number basis) of the obtained particle diameters was calculated and used as the average particle size.

[0046] [Example 1] A solution was obtained by mixing and stirring 15 parts of a redox pair, which was an equimolar mixture of potassium ferricyanide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and potassium ferrocyanide trihydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), with 84.9 parts of distilled water. 0.1 parts of hollow particles (A1) were added to the obtained solution to obtain an electrolyte composition. The obtained electrolyte composition was evaluated as follows.

[0047] <Evaluation of thermoelectric voltage> As shown in FIGS. 1 and 2, a ribbon thermocouple 2, a gold electrode 3, and a pipe 4 (bottom diameter 2.5 cm, height 1 cm) were placed on a Peltier element 1 (hereinafter referred to as the bottom Peltier element) in this order, and the resulting electrolyte composition 5 was filled into the pipe. Next, a ribbon thermocouple 7 and a gold electrode 8 were placed on another Peltier element 6 (hereinafter referred to as the top Peltier element) in this order from below to create a laminate. This laminate was placed on a pipe 4 filled with the electrolyte composition 5 so that the gold electrode was in contact with the electrolyte composition 5, thereby creating a thermoelectric voltage evaluation device. Next, the bottom Peltier element was set to 30°C and the top Peltier element was set to 15°C. After holding for 2 minutes, the upper and lower gold electrodes were connected to a voltmeter and the voltage was measured. Next, while the temperature of the bottom Peltier element was maintained at 30°C, the top Peltier element was heated by 5°C and the same measurement was performed. This measurement was continued until the top Peltier element reached 45°C. The obtained voltage values ​​were plotted against the temperature difference between the bottom-surface Peltier element and the top-surface Peltier element, as shown in Figure 3, and the thermoelectric voltage was estimated from the slope of the obtained linear approximation line. Evaluation was based on the relative value when the thermoelectric voltage of Comparative Example 1 was set to 1, and was evaluated according to the following criteria. The results are shown in Table 1. ◎: Relative value of 1.5 or more (great improvement over Comparative Example 1) ○: Relative value 1.2 or more and less than 1.5 (better than Comparative Example 1) △: Relative value 1.0 or more and less than 1.2 (same as Comparative Example 1) ×: Relative value less than 1.0 (deteriorated from Comparative Example 1) The Peltier elements 1 and 6 used in the measurements were a Peltier temperature controller set (product number: VTH1.8K-70S) manufactured by VICS Corporation, which was connected to separate heat sinks 9 and 10 and a temperature controller, and ribbon thermocouples 2 and 7 were ribbon temperature sensors (product number: RB-K-100-1-SMP) manufactured by AS ONE Corporation. The same applies to the evaluation of the battery output density shown below.

[0048] <Battery power density evaluation> In a temperature-controlled room set at 25°C, an electrolyte composition was placed on the lower Peltier element 11 in the same manner as in the thermoelectric voltage measurement shown in Figs. 4 and 5. Next, a laminate was fabricated by placing a ribbon thermocouple 16 and a gold electrode 17, in that order, on an insulated heat sink 19. This laminate was then placed on a pipe 14 (bottom diameter 2.5 cm, height 3 mm) filled with an electrolyte composition 15 so that the gold electrode was in contact with the electrolyte composition, thereby fabricating a battery power density measurement and evaluation device. Next, the bottom Peltier element was set to 40°C, and the heat sink side was allowed to cool naturally. After holding for 2 minutes, the voltage was swept and the current value was measured. The maximum power was estimated from the obtained voltage-current plot and divided by the bottom area of ​​the pipe to obtain the battery power density. Evaluation was based on the relative value, assuming the battery power density of Comparative Example 1 to be 1, and evaluated according to the following criteria. The results are shown in Table 1. ◎: Relative value of 2.0 or more (great improvement over Comparative Example 1) ○: Relative value 1.5 or more and less than 2.0 (better than Comparative Example 1) △: Relative value 1.2 or more and less than 1.5 (slightly improved from Comparative Example 1) ×: Relative value less than 1.2 (same as Comparative Example 1)

[0049] <Evaluation of repeat stability> After measuring the battery power density, the lower Peltier element of the battery power density measurement / evaluation device was cooled to 25°C and held there for 10 minutes. The lower Peltier element of the battery power density measurement / evaluation device was then warmed to 40°C and held there for 10 minutes, and the battery power density was measured again. The lower Peltier element of the battery power density measurement / evaluation device was then cooled to 25°C and held there for 10 minutes, and then heated to 40°C and held there for 10 minutes. This cycle constituted one measurement, and was repeated until a total of 50 cycles were reached. The battery power density measured at the last cycle (50th cycle) was divided by the battery power density measured at the first cycle (1st cycle) and then subtracted from 100% to calculate the rate of decrease in battery power density. The repetitive stability was evaluated according to the following criteria. The results are shown in Table 1. ◎: Decrease rate less than 1% ○: Decrease rate is 1% or more but less than 2% △: Decrease rate is 2% or more but less than 5% ×: Decrease rate of 5% or more In practice, the reduction rate is less than 5%.

[0050] [Examples 2 to 16] An electrolyte composition was prepared in the same manner as in Example 1, except that the materials and blending amounts were changed as shown in Table 1, and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1. The solvent was used when mixing the redox pair to prepare the electrolyte solution, and the compound having a functional group selected from a carboxyl group, a hydroxyl group, a guanidino group, or a salt thereof was added to a solution consisting of the redox pair and the solvent, after which the hollow particles were added. The abbreviations for the redox pair and compounds in Table 1 are as follows. The abbreviations for the hollow particles in Table 1 are as shown in Table 2.

[0051] <Redox pair> Fe 2+ / Fe 3+ : Potassium ferrocyanide / potassium ferricyanide = 1 mol / 1 mol mixture I - / I3 - : Potassium iodide / Iodine = 2mol / 1mol mixture C o 2 + / C o 3 + : ((Tris(2,2'-bipyridine)cobalt(II) bis(hexafluorophosphate) / tris(2,2'-bipyridine)cobalt(III) tris(hexafluorophosphate) = 1 mol / 1 mol mixture

[0052] <Compound (A)> (Compounds having a carboxy group or its salt) AA: Polyacrylic acid (manufactured by Toagosei Co., Ltd., trade name "Jurimer (registered trademark) AC-10L") AANa: Partially neutralized sodium polyacrylate (manufactured by Toagosei Co., Ltd., trade name "Aronvis (registered trademark) AH-105X") (Compounds having a hydroxyl group or its salt) AGR: Agarose (Fujifilm Wako Pure Chemical Industries, Ltd., product name "Agarose 1600") CD: Cyclodextrin (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "α-cyclodextrin") AIPD: Aluminum isopropylate (manufactured by Kawaken Fine Chemicals Co., Ltd., product name "AIPD") (Compounds having a guanidino group or a salt thereof) NAG: N-acetylguanidine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "N-acetylguanidine") GDC: Guanidine hydrochloride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "Guanidine Hydrochloride")

[0053] [Comparative Examples 1 to 3] As in Example 1, an electrolyte composition was prepared in the blending amounts shown in Table 1, and measurements were carried out in the same manner as in Example 1. The results are shown in Table 1. Note that the composition of Comparative Example 3 does not contain a redox couple as an electrolyte, and refers to a composition in which only distilled water and hollow particles are mixed, and the repetitive stability was not evaluated.

[0054] As described above, it was revealed that the battery containing the electrolyte composition of the present invention had a good battery power density and excellent cycle stability. On the other hand, the battery containing the electrolyte composition of Comparative Example 1 did not contain hollow particles and had a low battery power density. The battery containing the electrolyte composition of Comparative Example 2 had an average particle diameter of hollow particles greater than 200 μm, which resulted in poor uniformity in the electrolyte composition and low cycle stability. The battery containing the electrolyte composition of Comparative Example 3 did not exhibit thermoelectric conversion performance because it did not contain a redox couple.

[0055] [Table 1]

[0056] [Table 2] [Explanation of symbols]

[0057] 1, 6, 11 Peltier element 2, 7, 12, 16 Ribbon thermocouples 3, 8, 13, 17 Gold electrodes 4, 14 pipes 5, 15 Electrolyte composition 9, 10, 18, 19 Heatsink

Claims

1. A thermochemical battery comprising an electrolyte composition, characterized in that the electrolyte composition contains at least one pair of redox couples and hollow particles, and the average particle diameter of the hollow particles is 200 μm or less.

2. 2. The thermochemical battery according to claim 1, wherein the hollow particles are contained in the electrolyte composition in an amount of 0.1% by mass to 30% by mass.

3. A thermochemical battery as described in claim 1 or 2, wherein the electrolyte composition further contains a compound having at least one functional group selected from a carboxy group, a hydroxyl group, a guanidino group, and salts thereof.

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