Electrolyte compositions for calcium batteries, electrolytes for calcium batteries, and calcium batteries

Abstract

A composition for electrolytes for calcium batteries which contains a calcium salt comprising a calcium atom, boron atoms, and hydrogen atoms and having a cage structure.

Description

[Technical Field]

[0001] The present invention discloses an electrolyte composition for a calcium battery, an electrolyte containing this composition, and a calcium battery containing this electrolyte. [Background technology]

[0002] Lithium-ion batteries have high energy density and are used in portable electronic devices and grid-scale storage. The demand for large-scale energy storage systems is increasing with the proliferation of electric vehicles and smart grids. However, the performance of lithium-ion batteries is approaching its theoretical limits. Furthermore, lithium, the material used, is unevenly distributed, raising concerns about depletion of reserves and soaring prices. Therefore, the development of batteries using alternative materials to lithium is desired.

[0003] In recent years, calcium batteries have attracted attention as a next-generation secondary battery. Calcium batteries possess a high energy density comparable to lithium-ion batteries. Furthermore, their abundant resource availability allows for significant cost reductions.

[0004] Research into electrolytes for calcium batteries is progressing in order to commercialize them. The performance of a calcium battery is determined by three factors: Ca ion conductivity, the stability of the Ca ion dissolution reaction, and the potential window.

[0005] Non-patent document 1 discloses an electrolyte in which the calcium salt Ca(BF4)2 is dissolved in an ethylene carbonate / propylene carbonate (EC+PC) solvent. However, this battery operates at temperatures above 150°C, and the dissolution and extraction of Ca ions from the electrolyte is unstable, resulting in low Coulomb efficiency.

[0006] Non-patent document 2 discloses an electrolyte obtained by dissolving Ca(BF4)2 in tetrahydrofuran (THF), which has high Coulomb efficiency on an Au electrode, as a solvent. Although this electrolyte is compatible with Ca metal, its anodic stability is only 2.4V vs. Ca.2+ Because it is a Ca-based system, the potential window is narrow, and high voltage applications are impossible.

[0007] Non-patent documents 3 and 4 disclose an electrolyte obtained by dissolving Ca(4DME)[B(hfip)4]2 in 1,2-dimethoxyethane (DME) as a solvent. While this electrolyte provides good anodic stability (>4.0V), it contains fluorine, which causes calcium fluoride (CaF2) to form on the electrode during the charge-discharge process, preventing Ca ion conduction. [Prior art documents] [Non-patent literature]

[0008] [Non-Patent Document 1] A. Ponrouch et al., Nature Materials 2016, 15, 169-172. [Non-Patent Document 2] D. Wang et al., Nature Materials 2018, 17, 16-20. [Non-Patent Document 3] ZY Li et al., Energy and Environmental Science 2019, 12, 3496-3501 [Non-Patent Document 4] A. Shyamsunder et al., ACS Energy Lett. 2019, 4, 2271-2276 [Overview of the project] [Problems that the invention aims to solve]

[0009] This invention was conceived in view of the above problems, and does not contain halogens such as fluorine, has high Ca ion conductivity, stable Ca ion dissolution and extraction reaction, and has a wide potential window. Electrolyte compositions for calcium batteries, electrolytes for calcium batteries, and The objective is to provide a calcium battery.

[0010] To solve the above problems, we synthesized a novel electrolyte composition for calcium batteries, produced a novel electrolyte containing this composition, and fabricated a calcium battery containing this electrolyte. [Means for solving the problem]

[0011] The electrolyte composition for calcium batteries disclosed herein comprises at least calcium atoms, boron atoms, and hydrogen atoms, and contains a calcium salt having a cage structure.

[0012] The electrolyte of the calcium battery disclosed herein comprises an electrolyte medium and a calcium salt having a cage structure and consisting of at least calcium atoms, boron atoms, and hydrogen atoms.

[0013] The calcium battery disclosed herein comprises a positive electrode, a negative electrode, an electrolyte medium, and an electrolyte for a calcium battery which includes a calcium salt having a cage structure and comprising at least calcium atoms, boron atoms, and hydrogen atoms. [Effects of the Invention]

[0014] According to the present invention, the material does not contain halogens such as fluorine, has high Ca ion conductivity, the Ca ion dissolution reaction is stable, and the potential window is wide. Electrolyte compositions for calcium batteries, electrolytes for calcium batteries, and We can provide calcium batteries. [Brief explanation of the drawing]

[0015] [Figure 1] This is a diagram showing the structure of [CB11H12]-. [Figure 2] This figure shows the material evaluation of Ca(CB11H12)2. Figure 2A shows the Raman spectrum, Figure 2B shows the nuclear magnetic resonance (NMR) spectrum of 11B, and Figure 2C shows the NMR spectrum of 1H. [Figure 3] This figure shows the electrolyte concentration of calcium salts and Ca ion conductivity for each solvent. [Figure 4] This diagram schematically shows a trielectrode calcium battery used for evaluation. [Figure 5] This figure shows a cyclic voltammogram of the Ca(CB11H12)2 / THF / DME electrolyte. [Figure 6] This is a schematic diagram of a calcium battery. [Figure 7] This figure shows the Coulomb efficiency determined from the cyclic voltammogram. [Figure 8] This figure shows the discharge and charge profiles of a calcium-sulfur battery using Ca(CB11H12)2 / THF / DME electrolyte. [Modes for carrying out the invention]

[0016] [A. One Embodiment] Embodiments of the present invention will be described below with reference to the drawings. The following description provides general or specific examples. Furthermore, the following embodiments are examples only, and the scope of the present invention is not limited to the embodiments described below.

[0017] [1. Electrolytes] As mentioned above, the performance of a calcium battery is determined by three factors: Ca ion conductivity, the stability of the Ca ion dissolution and extraction reaction, and the potential window. Specifically, Ca ion conductivity and the potential window are affected by the choice of electrolyte, and the stability of the Ca ion dissolution and extraction reaction is affected by the combination of the positive and negative electrodes. Here, we will explain the electrolyte, and the combination of the positive and negative electrodes will be discussed later.

[0018] To obtain an electrolyte with high Ca ion conductivity and a wide potential window, the inventors first synthesized the following novel electrolyte composition. Next, they prepared an electrolyte solution by dissolving this composition.

[0019] [1-1. Composition] The composition may be in the form of a calcium salt, and may be an inorganic calcium salt and / or an organic calcium salt. The salt is preferably anhydrous. The calcium salt is synthesized by combining a monovalent anion with a calcium atom which is a divalent cation.

[0020] The monovalent anion is, for example, Cl - , Br - , I - , BF4 - , PF6 - , AsF6 - , SbF6 - , SiF6 - , ClO4 - , AlCl4 - , FSO3 - , CF3SO3 - , C4F9SO3 - , [N(FSO2)2] - , [N(CF3SO2)2] - , [N(C2F5SO2)2] - , [N(FSO2)(CF3SO2)] - , CF3BF3 - , C2F5BF3 - , CB 11 H 12 - and their derivatives.

[0021] From the viewpoint of electrochemical stability, BF4 - , PF6 - , ClO4 - , AlCl4 - , [N(CF3SO2)2] - , [N(C2F5SO2)2] - , or CB 11 H 12 - may be selected. From the viewpoint of solubility, PF6 - , FSO3 - , [N(CF3SO2)2] - , [N(C2F5SO2)2] - , or CB 11 H 12 - may be selected.

[0022] In this embodiment, mainly attention was paid to anions belonging to closo-type complex hydrides or carboranes. The closo-type complex hydride is a kind of boron compound group, and its chemical formula is [B n H n] 2- It is represented as follows. Carboranes are also a type of boron compound, and are a general term for polyhedral boranes containing carbon atoms. All of them have a cage-like (clotho structure) crystal structure (see Figure 1). In a clotho structure, there are boron atoms at each vertex of a closed polyhedron and there are no 3-center 2-electron bonds. In the carborane system, carbon atoms are further bonded to the clotho structure.

[0023] An example of anion belonging to the carborane group is CB 11 H 12 CB9H 10 Examples include CB7H8, preferably CB 11 H 12 CB may be selected. Carborane anions share the common characteristics of having excellent reduction stability, not undergoing reductive decomposition on the surface of calcium metal electrodes, and having low coordination with calcium cations due to weak interaction with them. 11 H 12 It is expected that good calcium solubility stability can be obtained by selecting other carborane-based anions instead. Figure 1 shows CB 11 H 12 ([CB 11 H 12 ] - The structure of ) is shown. As the legend indicates, the parts shown with fine right-sloping hatching are hydrogen atoms (H), the parts filled in black are carbon atoms (C), and the parts shown with coarse left-sloping hatching are boron atoms (B). [CB 11 H 12 ] - In this structure, boron atoms (B) and carbon atoms (C) are bonded together to form a space inside, and this structure is described as a cage shape. Hydrogen atoms (H) bond to the periphery of this cage-shaped structure, [CB 11 H 12 ] - A formation is created.

[0024] The composition of this embodiment contains a calcium salt having a cage structure, comprising at least calcium atoms, boron atoms, and hydrogen atoms. This calcium salt has the general formula Ca(CB) n-1 H n It contains components represented by )² (where n is an integer greater than or equal to 4). Specifically, calcium salts include Ca(CB). 11 H 12 )2, and Ca(CB 11 H 12 )2 and Ca(CB9H 10 It may contain an ingredient selected from either of the two mixtures (mixed salts). If the calcium salt is a mixed salt, the general formula is Ca(CB 11 H 12 ) 2-x (CB9H 10 ) X (where x is an integer greater than or equal to 1) is used to represent this. Below, the calcium salt is Ca(CB) 11 H 12 Let's explain using example 2. Ca(CB 11 H 12 Other calcium salts besides 2 can also be synthesized by the same method as described below.

[0025] Ca(CB 11 H 12 The synthesis method for )2 will be explained. Step 1 involves using the starting material A(CB 11 H 12 The aqueous solution of )x is passed through a cation exchange resin, and (H3O)(CB 11 H 12 ) Prepare as an aqueous solution. Examples of A include Li, Na, Cs, Me3NH, Mg, etc., but in this example A=Cs and x=1 or 2. In step 2, the obtained (H3O)(CB) 11 H 12 )Calcium compounds such as Ca(CO3) and Ca(OH)2 are added to an aqueous solution and neutralized in the aqueous solution, thereby producing Ca(CB 11 H 12 ) Dihydrate is obtained. In step 3, the obtained Ca(CB) 11 H 12)For the dihydrate, heat treatment is carried out under vacuum at 160 - 240 °C to dehydrate it, thereby obtaining anhydrous Ca(CB 11 H 12 )2.

[0026] [1 - 2. Evaluation of the composition] For the Ca(CB 11 H 12 )2 dihydrate and anhydrous Ca(CB 11 H 12 )2 obtained by the steps of the above synthesis method, material evaluation was carried out. Sample 1 is Ca(CB 11 H 12 )2 (dihydrate) before heat treatment, and Sample 2 is Ca(CB 11 H 12 )2 (anhydrous) after heat treatment.

[0027] Note that the measurements for evaluating the composition and electrolyte in this embodiment were carried out under the temperature condition of 25 °C (room temperature) and the humidity condition of 1 ppm or less. The electrolyte was handled in a glove box filled with an inert gas of argon in order to prevent contamination such as moisture from mixing in.

[0028] <Raman spectroscopy measurement> In-situ Raman spectroscopy measurement was carried out on Samples 1 and 2. For this measurement, a Raman spectrometer (DXR Raman Microscope manufactured by Thermo SCIENTIFIC) was used.

[0029] Figure 2A shows the spectroscopic analysis results. In Figure 2A, the horizontal axis represents the Raman shift, and the vertical axis represents the normalized scattering intensity. Among the two spectra, the upper one shows the Raman spectrum of Sample 1, and the lower one shows the Raman spectrum of Sample 2. The symbols attached to each spectrum are: * indicates the peak of [CB 11 H 12 - , and the diamond-shaped figure indicates the peak of H2O. In any of the spectra, [CB 11 H 12 - ​​The peak of was detected. As the peak of H2O was not detected in the lower spectrum, it was confirmed that Sample 2 was anhydrous.

[0030] <NMR Measurement> Nuclear Magnetic Resonance (NMR) measurements were performed on Samples 1 and 2. For this measurement, a nuclear magnetic resonance apparatus (manufactured by Bruker, AVANCE III 400 type) was used.

[0031] Figures 2B and 2C show the results of nuclear magnetic resonance analysis. In Figures 2B and 2C, the horizontal axis indicates the chemical shift, and the vertical axis indicates the normalized signal intensity. Figure 2B shows 11 the detection result of , and Figure 2C shows 1 the detection result of . In each detection result, among the two spectra, the upper one is the NMR spectrum of Sample 1, and the lower one is the NMR spectrum of Sample 2. As shown in Figure 2B, the peak of 11 was detected in both spectra. On the other hand, as shown in Figure 2C, the peak of 1 was not detected in the spectrum of Sample 2. From this, it was also confirmed that Sample 2 was anhydrous in the NMR measurement.

[0032] <ICP-OES Measurement> Inductivity coupled plasma optical emission spectrometer (ICP-OES) measurement was performed on Sample 1. For this measurement, an ICP emission spectroscopic analyzer (manufactured by Thermo SCIENTIFIC, iCAP6500) was used.

[0033] Table 1 shows the composition ratio of Ca(CB 11 H 12 )2. When the contents of calcium, boron, and cesium are shown as ratios, the theoretical value is 1:22:0, but the measurement result is 1:21.96:1.5×10 -5 , and a value close to the theoretical value was obtained. [Table 1]

[0034] From the above multiple measurement results, Ca(CB) 11 H 12 It was confirmed that )2 was successfully synthesized.

[0035] [1-3. Electrolyte medium] Any liquid capable of dissolving calcium salts can be used as the electrolyte medium, but non-aqueous solvents are preferred. Examples of non-aqueous solvents include ether-based, carbonate-based, and glyme-based solvents. Ether-based solvents are particularly preferred because ether oxygen, which has negative polarity to Ca ions, does not easily coordinate with them, allowing for high-concentration dissolution of calcium salts. Examples of low-coordination ether-based solvents include 1,2-dimethoxyethane (hereinafter abbreviated as DME), tetrahydrofuran (hereinafter abbreviated as THF), triglyme, diglyme, tetraglyme, and propylene carbonate.

[0036] Typically, DME or THF is used as the solvent for calcium electrolytes. Therefore, the present composition Ca(CB) 11 H 12 When )2 was added to DME and THF respectively, it hardly dissolved in either. Therefore, a mixed solution of DME and THF (hereinafter referred to as DME / THF mixed solution) was prepared, and Ca(CB 11 H 12 When )2 was added to the mixed solution, it dissolved well. The amount dissolved was approximately 0.5 mol / L or more. In this embodiment, the volume ratio of DME to THF in the DME / THF mixed solution is 1:1, but the volume ratio may be different. Ca(CB 11 H 12 The electrolyte state when )2 is dissolved in DME / THF is liquid.

[0037] Furthermore, Ca(CB) 11 H 12 )2 and Ca(CB9H 10When the mixture of )2 (mixed salt) was added to the DME / THF mixed solution, it dissolved well. The amount dissolved was Ca(CB 11 H 12 )2 and Ca(CB9H 10 Each of the two concentrations was approximately 0.25 mol / L or higher. The electrolyte state when the mixture is dissolved in DME / THF is liquid.

[0038] Figure 3 and Table 2 show the solubility of calcium compounds and the conductivity of Ca ions in each solvent. Here, the calcium compound is Ca(CB). 11 H 12 )2 and Ca(CB9H 10 )2 was used. In Figure 3, the horizontal axis shows concentration (electrolyte concentration), and the vertical axis shows conductivity (Ca ion conductivity). For the elemental solvents DME, THF, diglime, and triglime, Ca(CB) was used. 11 H 12 A saturated amount of )2 was dissolved. Furthermore, two equal volumes of the mixed solvent DME / THF were prepared, and in one of them, Ca(CB) was added. 11 H 12 Dissolve 2 in 0.25 [mol / L] solution (hereinafter referred to as "DME / THF1"), and in the other, add Ca(CB 11 H 12 )2 and Ca(CB9H 10 )2 were each dissolved in a solution of 0.25 [mol / L] (hereinafter, this mixed solvent will be referred to as "DME / THF2").

[0039] Table 2 shows the electrolyte concentrations of saturated solutions for the individual solvents DME, THF, diglime, and triglime. For the mixed solvent DME / THF1, the electrolyte concentration is Ca(CB). 11 H 12 The electrolyte concentration is 20.5 [mol / L], and for the mixed solvent DME / THF2, Ca(CB) 11 H 12 )2 is mixed with 0.25 [mol / L] Ca(CB9H 10 This shows an electrolyte concentration of 0.5 [mol / L], which is the sum of 0.25 [mol / L] of )2. [Table 2]

[0040] Figure 3 plots the data points for each solvent, with diglime shown as G2, triglime as G3, and the mixed solvents DME / THF1 and DME / THF2. From Figure 3 and Table 2, it was confirmed that the elemental solvents DME and THF had low solubility and ionic conductivity, while the mixed solvents DME / THF1 and DME / THF2 had high solubility and ionic conductivity. Furthermore, while the elemental solvents diglime and triglime yielded similarly favorable electrolyte concentrations and ionic conductivity, the mixed solvents DME / THF1 and DME / THF2 yielded more favorable results. In addition, it was confirmed that the mixed solvent DME / THF2 yielded higher conductivity than the mixed solvent DME / THF1.

[0041] [1-4. Method for producing electrolyte solution] The electrolyte production method according to this embodiment is calcium salt Ca(CB) 11 H 12 It is prepared by dissolving )2 in a non-aqueous solvent DME / THF mixed solution. For example, a DME / THF mixed solution of a desired electrolyte concentration is added to the calcium salt powder and stirred. This operation was carried out under temperature conditions of 25°C (room temperature) and humidity conditions of 1 ppm or less. Stirring was continued for about one night until the solution became completely clear.

[0042] [1-5. Evaluation of the electrolyte] To evaluate the characteristics of the electrolyte, cyclic voltammetry was performed on the three-electrode prototype calcium battery shown in Figure 4 to determine the elution and extraction of Ca ions from the electrolyte. =Configuration of a three-electrode prototype calcium battery= Electrolyte: Ca(CB 11 H 12 )2 dissolved in a DME / THF mixed solution Working electrode: Metal electrode (e.g., Au) Counter electrode: Ca electrode Reference electrode: Ca electrode

[0043] <Cyclic Voltammogram> Figure 5 shows the results of cyclic voltamogram (CV) measurements. In Figure 5, the horizontal axis represents potential and the vertical axis represents current. Regarding the current, no current was obtained in the initial cycle, but the current increased with each subsequent cycle. The CV curve that increases in the positive direction, with an increase of 0V as the boundary, represents the oxidation current and indicates the Ca ion dissolution reaction. The CV curve that increases in the negative direction represents the reduction current and indicates the Ca ion deposition reaction. The fact that the absolute value of the reduction peak current is larger than the oxidation peak current indicates that the deposition reaction proceeded more rapidly than the dissolution reaction of Ca ions. Furthermore, the large reduction peak current and the fact that the reduction peak current has not shifted to the negative electrode side indicate that the diffusion rate and the electrode reaction rate are equivalent. In addition, regarding the potential, since no current flows at 4V, it can be seen that the potential window is wide down to slightly less than 4V. From these results, it was confirmed that the dissolution and deposition reaction of Ca ions is stable in the range of slightly less than 20mA with this electrolyte, and that the potential window is wide.

[0044] [2. Calcium battery] [2-1. Overall Structure] The electrolyte according to this embodiment can be used in a calcium battery. A calcium battery includes a positive electrode, a negative electrode, and the electrolyte of the calcium battery. The electrolyte can be any of the ones described in [1. Electrolyte] above. The calcium salt is Ca(CB). 11 H 12 It may contain the component )2, and furthermore, Ca(CB9H 10 It may also contain component 2.

[0045] Figure 6 is a schematic diagram showing an example configuration of a calcium battery 1. The calcium battery 1 is a rechargeable secondary battery. The calcium battery 1 comprises a positive electrode 2, a negative electrode 3, and a separator 4. The separator 4 is positioned between the positive electrode 2 and the negative electrode 3. The structure of the calcium battery 1 may be, for example, button type, coin type, cylindrical type, prismatic type, or laminate type.

[0046] The amount of energy stored in a calcium battery is determined by the amount of Ca ions stored in the electrode materials of the positive and negative electrodes, and the difference in reaction potential (voltage) between the positive and negative electrodes. [2-2. Positive electrode] Positive electrode 2 may contain a positive electrode active material capable of reversibly desorbing and inserting Ca ions. Examples of positive electrode active materials include sulfur and titanium sulfide, vanadium oxide, manganese oxide, iron phosphate, sodium vanadium phosphate, calcium molybdate, and Prussian blue. Of these, sulfur is particularly preferred. Sulfur has a large theoretical capacity and can store 5 to 10 times more Ca ions in its structure compared to the oxide-type positive electrode active materials mentioned above. Furthermore, sulfur has a relatively low chemical reaction potential, which is a disadvantage as it makes it difficult to obtain high energy density, but on the other hand, it has the advantage of reducing the load on the electrolyte. For this reason, a sulfur positive electrode can obtain high energy density without decomposing the electrolyte.

[0047] [2-3. Negative electrode] The negative electrode 3 may contain a negative electrode active material capable of reversibly desorbing and inserting Ca ions. A preferred example of the negative electrode active material is metallic calcium. The greatest energy density can be obtained by using Ca ions from metallic calcium. Another example is calcium alloy. This alloy is calcium tin alloy (CaSn x ), silicon calcium alloy (CaSi x ), calcium zinc alloy (CaZn x ), calcium lithium alloy (CaLi x ), calcium sodium alloy (CaNa x ) etc. are acceptable.

[0048] The combination of positive electrode 2 and negative electrode 3 is preferably such that positive electrode 2 is sulfur (S) and negative electrode 3 is calcium (Ca) metal. The reason for this is, for example, the "theoretically" large capacity (1.34 Ah / g) of calcium metal and its Ca 2+This is because it is the optimal potential relative to Ca. Also, the reaction potential between sulfur and calcium is 2.5V vs. Ca. 2+ / Ca is the oxidative degradation potential of the electrolyte (4V vs. Ca 2+ Since there is ample margin for (above / Ca), a long lifespan for calcium battery 1 can be expected.

[0049] In the above embodiment, the positive electrode 2 and negative electrode 3 are preferably made by mixing the granularly crushed active material with a conductive material such as acetylene black, carbon black, or graphite, and a binder such as polyvinylidene fluoride or polytetrafluoroethylene. These polymer materials are limited insofar as they bind the active material and the conductive material and achieve the effects of the present invention. isn't it.

[0050] [2-4. Separator] The separator 4 is for insulating the positive electrode 2 from the negative electrode 3. The separator 4 is impregnated with a liquid electrolyte. Examples of separator materials include porous films or nonwoven fabrics. The separator may consist of, for example, glass fiber, glass ceramics, polyethylene, polypropylene, cellulose, and polyvinylidene fluoride, or mixtures thereof. The separator may contain an electrolyte. The calcium battery 1 of this embodiment may be obtained by contacting, for example, impregnating the separator 4 with a liquid electrolyte.

[0051] [2-5. Electrochemical Evaluation] The electrolyte based on this embodiment was evaluated electrically and chemically. <Coulomb efficiency> Figure 7 plots the Coulomb efficiency determined from the cyclic voltammogram measurement results in Figure 5 for a triode calcium battery (see Figure 4). In Figure 7, the horizontal axis represents the cycle and the vertical axis represents the Coulomb efficiency. The Coulomb efficiency remains constant at 90% from the 5th cycle onward, and a very high Coulomb efficiency is maintained throughout the entire cycle. This result indicates that the capacity gained during charging can be used for discharge without loss, confirming that calcium batteries using this electrolyte have excellent charge-discharge cycle performance and can be expected to have a long lifespan.

[0052] Furthermore, measurements were performed on the following two-electrode prototype calcium battery 1 (see Figure 6). =Two-electrode prototype calcium battery 1= Electrolyte: Ca(CB 11 H 12 )2 dissolved in a DME / THF mixed solution Negative electrode material: Ca metal Cathode material: Sulfur (S)

[0053] <Charge / Discharge Profile> Figure 8 shows the charging profile. Specifically, it shows the results of measuring the cycling performance of the electrolyte during charge and discharge in a potential window of 1.0 to 3.2V. In Figure 8, the horizontal axis represents capacity and the vertical axis represents voltage. Of the two lines, the line labeled "Charging" is the current-potential curve during charging, and the line labeled "Discharging" is the current-potential curve during discharge. Reversibility can be inferred from these results, confirming that charge and discharge are occurring in the calcium battery using this electrolyte.

[0054] [B. Others] [Industrial applicability]

[0055] According to the present invention, the material does not contain halogens such as fluorine, has high Ca ion conductivity, the Ca ion dissolution reaction is stable, and the potential window is wide. Electrolyte compositions for calcium batteries, electrolytes for calcium batteries, and A calcium battery can be provided. The electrolyte composition and electrolyte of this disclosure can be used in a calcium battery. [Explanation of Symbols]

[0056] 1. Calcium battery 2 Positive electrode 3 Negative electrode 4 Separators

Claims

1. The present invention contains a calcium salt comprising at least calcium atoms, carbon atoms, boron atoms, and hydrogen atoms, and having a cage structure composed of the aforementioned carbon atoms, boron atoms, and hydrogen atoms. A composition for the electrolyte of a calcium battery.

2. The calcium salt has the general formula Ca(CB) ｎ－１ H ｎ ) ２ Includes components represented by (where n is an integer greater than or equal to 4), The electrolyte composition for a calcium battery according to claim 1.

3. The calcium salt is Ca(CB １１ H １２ ), ２ and includes any component selected from the mixture of Ca(CB １１ H １２ ), ２ and Ca(CB ９ H １０ ), ２ ​ The electrolyte composition for a calcium battery according to claim 2.

4. The calcium salt is Ca(CB １１ H １２ ) ２ Contains the following ingredients: The electrolyte composition for a calcium battery according to claim 3.

5. The calcium salt further comprises Ca(CB ９ H １０ ) ２ Contains the following ingredients: The electrolyte composition for a calcium battery according to claim 4.

6. The electrolyte is a liquid electrolyte, The electrolyte composition for a calcium battery according to any one of claims 1 to 5.

7. Electrolyte medium and A calcium salt having a cage structure, consisting of at least calcium atoms, boron atoms, and hydrogen atoms, The electrolyte for calcium batteries, which includes this component.

8. The general formula for the calcium salt is Ca(CB) ｎ－１ H ｎ ) ２ Includes components represented by (where n is an integer greater than or equal to 4), The electrolyte for the calcium battery according to claim 7.

9. The calcium salt is Ca(CB １１ H １２ ) ２ , and Ca(CB １１ H １２ ) ２ and Ca(CB ９ H １０ ) ２ Containing any of the components selected from the mixture, The electrolyte for the calcium battery according to claim 8.

10. The calcium salt is Ca(CB １１ H １２ ) ２ Contains the following ingredients: The electrolyte for the calcium battery according to claim 9.

11. The calcium salt further comprises Ca(CB ９ H １０ ) ２ Contains the following ingredients: The electrolyte for the calcium battery according to claim 10.

12. The electrolyte medium is a mixed solution of 1,2-dimethoxyethane and tetrahydrofuran. The electrolyte for a calcium battery according to any one of claims 7 to 11.

13. The volume ratio of 1,2-dimethoxyethane to tetrahydrofuran in the aforementioned mixed solution is 1:

1. The electrolyte for the calcium battery according to claim 12.

14. Positive electrode and, The negative electrode and, The electrolyte of the calcium battery according to any one of claims 7 to 13, A calcium battery containing calcium.

15. The electrolyte is impregnated in a separator for insulating the positive electrode and the negative electrode. The calcium battery according to claim 14.

16. The positive electrode is sulfur, The aforementioned negative electrode is made of calcium metal. The calcium battery according to claim 14 or 15.

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