High-concentration high-entropy electrolyte and preparation method therefor, and battery

Abstract

A high-concentration high-entropy electrolyte and a preparation method therefor, and a battery. The high-concentration high-entropy electrolyte has a high molar concentration and a high degree of confusion, and comprises a solvent, a first solute salt, and an additive salt, the first solute salt being a solute salt having a high solubility in the solvent, and the additive salt including three or more solute salts. A molar concentration of the solute salt in the high-concentration high-entropy electrolyte ranges from 20 M to 60 M, a molar concentration of the first solute salt exceeds 20 M, and the molar concentration of the first solute salt accounts for 50% or higher of the molar concentration of the high-concentration high-entropy electrolyte. A sodium-carbon dioxide battery assembled with the high-concentration high-entropy electrolyte not only has a high power density, but also has an excellent discharge specific capacity and rate performance. In addition, the battery also shows good cycling stability, and the battery generates a liquid discharge product, a formic acid, so that the blockage of a solid discharge product to a catalytic layer is effectively avoided.

Description

A high-concentration high-entropy electrolyte, a preparation method thereof, and a battery Technical Field

[0001] The present invention relates to a high-concentration high-entropy electrolyte and the design and manufacture of a battery. Specifically, the present invention relates to a high-concentration high-entropy electrolyte and a preparation method thereof and a battery. Background Art

[0002] Global warming is increasing the frequency and intensity of extreme weather and climate events, leading to severe meteorological disasters. The use of fossil fuels, resulting in large-scale carbon dioxide emissions, is the primary cause of the greenhouse effect. Therefore, reducing carbon dioxide emissions and converting them into valuable chemicals is an inevitable trend in today's society.

[0003] Metal-CO2 batteries equipped with advanced CO2 electrodes provide a promising strategy for CO2 recycling and electrochemical energy conversion and storage. Among them, sodium-CO2 batteries have abundant sodium resources, high energy density (1125Wh kg -1 ) and other advantages have attracted widespread attention. Therefore, research related to the application of sodium-carbon dioxide batteries is of great significance to solving the energy crisis and mitigating the greenhouse effect.

[0004] However, the poor physicochemical properties of the electrolyte seriously hinder the practical application of sodium-CO2 batteries. First, the low ionic conductivity and high viscosity of current electrolytes cannot meet the battery's requirements for rapid sodium ion transport during charge and discharge. Second, the low electrochemical stability window of the electrolyte leads to low battery operating voltage and ultimately low battery energy density. Third, when using existing electrolytes, the battery's discharge products are all solid products, namely sodium carbonate, sodium oxalate, or sodium bicarbonate. When the battery operates for a long time, the solid discharge products will clog the catalyst layer, causing battery failure. Therefore, the research of new electrolytes is of great significance to improve the electrochemical performance of sodium-CO2 batteries and promote the application of sodium-CO2 batteries.

[0005] Summary of the Invention

[0006] The present invention provides a high-performance, high-concentration, high-entropy electrolyte and a preparation method thereof. The most suitable sodium salt composition and concentration are optimized according to different sodium salt components and sodium salt ratios, and an electrolyte with high ionic conductivity, low viscosity, high stability and high disorder is successfully prepared.

[0007] The present invention also provides a sodium-carbon dioxide battery based on the high-concentration high-entropy electrolyte, and improves the battery's electrochemical properties such as rate, capacity, power density, and cycle by using the electrolyte.

[0008] The present invention provides a high-concentration high-entropy electrolyte, which increases the concentration of the solute salt in the electrolyte and further increases the degree of disorder of the salt anions or cations in the electrolyte by introducing a multi-component solute salt (both inorganic and organic salts) into the electrolyte. The high-concentration high-entropy electrolyte includes a solvent, a first solute salt, and an added salt. The first solute salt is a solute salt with high solubility in the solvent, and the added salt is a solute salt composed of three or more. The molar concentration of the solute salt in the high-concentration high-entropy electrolyte ranges from 20M to 60M, the molar concentration of the first solute salt exceeds 20M, and the molar concentration of the first solute salt accounts for more than 50% of the molar concentration of the high-concentration high-entropy electrolyte.

[0009] Furthermore, the sum of the molar concentrations of the added salts is less than 50% of the molar concentration of the high-concentration high-entropy electrolyte, and the addition ratio of the added salts is calculated based on the solubility of the solute salt in the solvent.

[0010] Furthermore, the solvent is an organic solvent or an inorganic solvent; the organic solvent is at least one of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, alcohols, ethers, esters, ketones, glycol derivatives, acetonitrile, pyridine, phenol, etc.; the inorganic solvent is at least one of acidic solvents, alkaline solvents, amphoteric solvents, and inert solvents.

[0011] Furthermore, the solute salt includes an organic salt or an inorganic salt. The solute salt includes lithium trifluoride (LiOTf), sodium trifluoride (NaOTf), magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium nitrate (LiNO3), sodium nitrate (NaNO3), sodium bis(trifluoromethanesulfonyl)imide (NaFSI), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), sodium perchlorate (NaClO4), lithium perchlorate (LiClO4), sodium chloride (NaCl), lithium chloride (LiCl), zinc chloride (ZnCl2), sodium iodide (NaI) and the like; the solvent is water (distilled water or deionized water).

[0012] The present invention also provides a method for preparing a high-concentration high-entropy electrolyte, comprising the following steps:

[0013] S1. Select a solute salt with high solubility as the first solute salt, weigh a certain amount of the first solute salt and dissolve it in a solvent to obtain an electrolyte with a certain molar concentration, and heat it to 60°C to obtain a basic high-concentration electrolyte.

[0014] S2. Select three or more solute salts as additive salts, calculate and weigh the required additive salts according to the preset molar concentration, and add them to the basic high-concentration electrolyte obtained in step S1. Also heat to 60° C. to ensure that all the solute salts are completely dissolved, thereby obtaining a mixed high-concentration electrolyte.

[0015] S3. Place the mixed high-concentration electrolyte obtained in S2 into an ultrasonic instrument and sonicate for 5-30 minutes to ensure that the components in the solution are completely mixed, and cool the solution to room temperature to obtain a high-concentration high-entropy electrolyte.

[0016] Furthermore, the molar concentration of the solute salt in the high-concentration high-entropy electrolyte is in the range of 20M-60M, the molar concentration of the first solute salt exceeds 20M, and the molar concentration of the first solute salt accounts for more than 50% of the total molar concentration of the high-concentration high-entropy electrolyte; the sum of the molar concentrations of the added salts is less than 50% of the total molar concentration of the high-concentration high-entropy electrolyte.

[0017] On the other hand, the present invention also provides a sodium-carbon dioxide battery comprising the high-concentration high-entropy electrolyte, wherein the high-concentration high-entropy electrolyte replaces the traditional positive electrode electrolyte (saturated sodium chloride solution, "salt-in-water" electrolyte, seawater electrolyte, etc.) to obtain a sodium-carbon dioxide battery based on the high-concentration high-entropy electrolyte.

[0018] Compared with the prior art, the present invention provides a sodium-carbon dioxide battery based on a high-concentration high-entropy electrolyte. The high-concentration high-entropy electrolyte includes a high-concentration base electrolyte and an added salt. The electrolyte has higher ionic conductivity, lower viscosity, higher stability, and higher disorder than traditional electrolytes. In addition, the electrolyte also has a higher carbon dioxide solubility capacity and weaker solvation effect. The use of this high-concentration high-entropy electrolyte can not only effectively improve the power density and discharge specific capacity of the sodium-carbon dioxide battery, but also improve the problem of poor rate performance of batteries based on traditional electrolytes. At the same time, the use of this electrolyte can also convert the solid discharge products of the sodium-carbon dioxide battery based on the traditional electrolyte into liquid discharge products, which is beneficial to improving the battery's cycle stability and increasing the utilization rate of the metal sodium negative electrode. In addition, the electrolyte can also effectively reduce the corrosion of the electrolyte on the electrode, thereby improving the performance of the battery, which is of great significance to the commercialization of sodium-carbon dioxide batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG1 is a schematic flow chart of a method for preparing a high-concentration high-entropy electrolyte provided in an embodiment of the present invention.

[0020] FIG2 is a schematic structural diagram of a sodium-carbon dioxide battery provided in an embodiment of the present invention.

[0021] FIG3 is a sodium nuclear magnetic resonance spectrum of a high-concentration high-entropy electrolyte and a traditional electrolyte provided by an embodiment of the present invention.

[0022] FIG4 is a power density curve diagram of a sodium-carbon dioxide battery based on a high-concentration high-entropy electrolyte and a traditional electrolyte provided by an embodiment of the present invention.

[0023] FIG5 is a rate curve diagram of a sodium-carbon dioxide battery based on a high-concentration high-entropy electrolyte and a traditional electrolyte provided by an embodiment of the present invention.

[0024] FIG6 is a graph showing the discharge specific capacity of a sodium-carbon dioxide battery based on a high-concentration high-entropy electrolyte and a traditional electrolyte according to an embodiment of the present invention.

[0025] FIG7 is a photograph of the metallic sodium negative electrode of a battery after discharge based on a traditional electrolyte and a high-concentration high-entropy electrolyte provided by an embodiment of the present invention.

[0026] FIG8 is a cycle curve diagram of a sodium-carbon dioxide battery based on a high-concentration high-entropy electrolyte and a traditional electrolyte provided by an embodiment of the present invention.

[0027] FIG9 is a Raman characterization of discharge products of a sodium-carbon dioxide battery based on a traditional electrolyte provided by an embodiment of the present invention.

[0028] FIG10 is a hydrogen nuclear magnetic resonance spectrum of a sodium-carbon dioxide battery product based on a high-concentration high-entropy electrolyte provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0030] Please refer to Figure 1, which is a schematic flow chart of a method for preparing a high-concentration high-entropy electrolyte provided by an embodiment of the present invention. The method for preparing a high-concentration high-entropy electrolyte provided by an embodiment of the present invention comprises the following specific steps:

[0031] S1. Select a solute salt with high solubility as a first solute salt, weigh a certain amount of the first solute salt and dissolve it in a solvent to obtain an electrolyte with a certain molar concentration, and heat it to 60° C. to obtain a basic high-concentration electrolyte.

[0032] S2. Select three or more solute salts as added salts, calculate and weigh the required added salts according to the preset molar concentration, add them to the basic high-concentration electrolyte obtained in step S1, and also heat to 60° C. to ensure that all solute salts are completely dissolved to obtain a mixed high-concentration electrolyte.

[0033] S3. Place the mixed high-concentration electrolyte obtained in S2 into an ultrasonic instrument and sonicate for 5-30 minutes to ensure that the components in the solution are completely mixed, and cool the solution to room temperature to obtain a high-concentration high-entropy electrolyte.

[0034] It can be understood that high solubility refers to the mass (solid and liquid) or volume of the solute that is dissolved after finally reaching saturation. In this embodiment, it refers to the mass of the solute that is dissolved after the solute salt is finally saturated in the solvent.

[0035] Among them, in the high-concentration high-entropy electrolyte prepared according to the preparation method of the high-concentration high-entropy electrolyte, the molar concentration of the solute salt is in the range of 20M-60M, the molar concentration of the first solute salt exceeds 20M, and the molar concentration of the first solute salt accounts for more than 50% of the total molar concentration of the high-concentration high-entropy electrolyte; the sum of the molar concentrations of the added salts is less than 50% of the total molar concentration of the high-concentration high-entropy electrolyte.

[0036] Specifically, the molar concentration of the solute salt can be 20M, 25M, 30M, 35M, 40M, 45M, 50M, 55M, 60M, as long as it is within the range of 20M-60M. The molar concentration of the first solute salt exceeds 20M, that is, the molar concentration of the first solute salt can be 20M, 25M, 30M, 35M, 40M, 45M, 50M, 55M, 60M, etc.; when the molar concentration of the high-concentration high-entropy electrolyte is 50M, the molar concentration of the first solute salt is at least 25M, and when the molar concentration of the high-concentration high-entropy electrolyte is 60M, the molar concentration of the first solute salt is at least 30M, that is, the molar concentration of the first solute salt is at least 10M. The molar concentration accounts for more than 50% of the total molar concentration of the high-concentration, high-entropy electrolyte; it can be understood that when the molar concentration of the first solute salt accounts for more than 50% of the total molar concentration of the high-concentration, high-entropy electrolyte, the sum of the molar concentrations of the added salts is less than 50% of the total molar concentration of the high-concentration, high-entropy electrolyte, that is, when the molar concentration of the high-concentration, high-entropy electrolyte is 50M, the molar concentration of the first solute salt is at least 25M, and the sum of the molar concentrations of the added salts is less than 25M.

[0037] In step S1 and step S2, the mass of the first solute salt and the added salt to be added is calculated based on the preset concentration of the high-concentration high-entropy electrolyte and the concentration of the first solute salt, and then the required mass of the first solute salt and the added salt are weighed to prepare solutions of corresponding molar concentrations in steps S1 and S2.

[0038] In this embodiment, the solute salt includes an organic salt or an inorganic salt. The solute salt includes lithium trifluoride (LiOTf), sodium trifluoride (NaOTf), magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium nitrate (LiNO3), sodium nitrate (NaNO3), sodium bis(trifluoromethanesulfonyl)imide (NaFSI), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), sodium perchlorate (NaClO4), lithium perchlorate (LiClO4), sodium chloride (NaCl), lithium chloride (LiCl), zinc chloride (ZnCl2), sodium iodide (NaI), etc. Specifically, the first solute salt is one of sodium fluorosulfonyl imide (NaFSI), lithium bisfluorosulfonyl imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and zinc chloride (ZnCl2); the added salt is at least three of lithium nitrate (LiNO3), sodium nitrate (NaNO3), sodium perchlorate (NaClO4), lithium perchlorate (LiClO4), sodium chloride (NaCl), lithium chloride (LiCl), and sodium iodide (NaI). It is understood that the added salt can be selected from three of the aforementioned solute salts, or four, five, six, or even more.

[0039] In the embodiments of the present invention, the solvent may be an organic solvent selected from at least one of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, alcohols, ethers, esters, ketones, glycol derivatives, acetonitrile, pyridine, and phenol; or an inorganic solvent selected from at least one of acidic solvents, alkaline solvents, amphoteric solvents, and inert solvents. In this embodiment, the solvent is water and / or deionized water.

[0040] In some embodiments, the high-concentration high-entropy electrolyte is a salt with high solubility in water as the first solute salt, such as NaFSI, LiFSI, LiTFSI, ZnCl2, etc., and then three or more salts are selected as additive salts and dissolved in deionized water according to a certain molar concentration to obtain a high-concentration high-entropy electrolyte, wherein the additive salt is a solute salt such as LiNO3, NaNO3, NaClO4, LiClO4, NaCl, LiCl, NaI, etc. The high-concentration high-entropy electrolyte obtained by using multiple salts has lower viscosity, higher ionic conductivity, wider electrochemical stability window and stability than traditional electrolytes. In addition, the electrolyte also has a higher carbon dioxide solubility capacity than traditional electrolytes. Most importantly, the high-concentration high-entropy electrolyte has a lower solvation effect than traditional electrolytes.

[0041] The high-concentration high-entropy electrolyte prepared by the preparation method of the high-concentration high-entropy electrolyte described in the embodiment of the present invention has high ionic conductivity, low viscosity, high stability, and high disorder; at the same time, it also has a high carbon dioxide solubility and a weak solvation effect.

[0042] On the other hand, an embodiment of the present invention further provides a sodium-carbon dioxide battery comprising the aforementioned high-concentration high-entropy electrolyte. As shown in Figure 2, Figure 2 is a schematic structural diagram of a sodium-carbon dioxide battery provided by an embodiment of the present invention. The sodium-carbon dioxide battery comprises a negative electrode A, a solid electrolyte membrane B, and a positive electrode C, wherein the negative electrode A comprises a metallic sodium negative electrode A1 and a negative electrode electrolyte A2, and the positive electrode C comprises a positive electrode electrolyte C1 and a catalyst layer C2. In an embodiment of the present invention, the metallic sodium negative electrode A1, the negative electrode electrolyte A2, the solid electrolyte membrane B, and the catalyst layer C2 are the same as those of a sodium-carbon dioxide battery with a conventional electrolyte, and the positive electrode electrolyte C1 is different from a sodium-carbon dioxide battery with a conventional electrolyte, and the positive electrode electrolyte C1 is a high-concentration high-entropy electrolyte prepared by the preparation method of the high-concentration high-entropy electrolyte described in an embodiment of the present invention.

[0043] Specifically, the sodium metal negative electrode A1 is a sodium metal sheet with a purity exceeding 99.7%, a thickness of 1 mm and a diameter of 10 mm; the negative electrode electrolyte A2 is an ester electrolyte of 1 mol / L NaClO4 / [(EC+DMC)(1:1)+1 vol% FEC], where 1:1 is a volume ratio; the solid electrolyte membrane B is Na3Zr2Si2PO 12The catalyst layer C2 is formed by pressing catalyst-loaded carbon paper and nickel foam, and the catalyst-loaded carbon paper has a diameter of 10 mm and a thickness of 0.5 mm. The catalyst-loaded carbon paper is prepared by coating a slurry formed by dispersing the catalyst in a mixed solution on a hydrophilic carbon paper, wherein the catalyst is a 5% Ru / C catalyst, and the mixed solution is a mixed solution formed by mixing alcohol: water: binder in a volume ratio of 8:1.5:0.5, and the binder is a 5% PVDF aqueous solution; the nickel foam has a thickness of 1 mm and a diameter of 10 mm.

[0044] In some embodiments, when a high-concentration high-entropy electrolyte is used in place of a conventional electrolyte in the cathode electrolyte C1 of a sodium-carbon dioxide battery, the lower viscosity of the high-concentration high-entropy electrolyte can significantly increase the battery's power density. Its higher ionic conductivity and lower solvation are beneficial for improving the battery's rate performance. Its wider electrochemical stability window and stability are beneficial for improving the battery's cycle performance. Its higher carbon dioxide solubility is beneficial for improving the battery's discharge specific capacity. Furthermore, the high-concentration high-entropy electrolyte's unique solvation structure allows for the highly selective generation of formic acid as a liquid product. The generation of this liquid product is less likely to clog the catalytically active sites of the catalyst layer, allowing the battery to discharge for extended periods, thereby improving the utilization of the negative electrode.

[0045] Example 1:

[0046] As shown in Figure 3, the nuclear magnetic resonance sodium spectra of a high-concentration high-entropy electrolyte and a traditional electrolyte prepared according to the above-mentioned preparation method in this embodiment; wherein, the high-concentration high-entropy electrolyte is prepared by dissolving 4 solute salts with a molar concentration of 20M NaFSI, 5M NaClO4, 5M NaCl and 5M NaNO3 in deionized water; wherein the traditional electrolyte is obtained by dissolving 35M NaFSI in deionized water. The results of nuclear magnetic resonance treatment of the above-mentioned two electrolytes show that in the nuclear magnetic resonance sodium spectrum, the chemical shift of the characteristic peak of sodium ions of the high-concentration high-entropy electrolyte gradually shifts to a lower field relative to the traditional electrolyte, indicating that the solvation effect around the sodium ions is reduced, which is conducive to the release of sodium ions during the operation of the battery and is more conducive to the rapid transfer of sodium ions. In this embodiment, two sodium-carbon dioxide batteries are provided for comparison experiments. The two sodium-carbon dioxide batteries include, from the negative electrode part A to the positive electrode part C, a metallic sodium negative electrode A1, a negative electrode electrolyte A2, a solid electrolyte membrane B, a positive electrode electrolyte C1, and a catalyst layer C2. Among them, the metal negative electrode A1 is a metal sodium sheet with a thickness of 1 mm and a diameter of 10 mm, and the negative electrode electrolyte A2 is 1 mol / LNaClO4 / [(EC+DMC)(1:1)+1 vol%FEC]; the solid electrolyte membrane B is a NASICON type fast ion conductor with a thickness of 1 mm and a diameter of 16 mm; the positive electrode electrolyte of one sodium-carbon dioxide battery is the high-concentration high-entropy electrolyte described above in this embodiment, that is, the high-concentration high-entropy electrolyte is prepared by dissolving 20M NaFSI, 5M NaClO4, 5M NaCl, and 5M NaNO34 solute salts in deionized water; the positive electrode electrolyte of another sodium-carbon dioxide battery is the traditional electrolyte described above in this embodiment, that is, the traditional electrolyte is 35M The catalyst layer is formed by dissolving NaFSI in deionized water; the catalyst layer is formed by pressing carbon paper loaded with the catalyst and nickel foam; the carbon paper loaded with the catalyst is porous hydrophilic carbon paper with a diameter of 10 mm and a thickness of 0.5 mm; the catalyst is 5% Ru / C; the nickel foam has a thickness of 1 mm and a diameter of 10 mm.

[0047] The two sodium-carbon dioxide batteries assembled in this embodiment were subjected to performance tests at a constant temperature of 30°C and pure CO2. The power density curve is shown in FIG4 , and the rate curve is shown in FIG5 . When the positive electrode electrolyte is the high-concentration high-entropy electrolyte, the maximum power density of the sodium-carbon dioxide battery is 5.85 mW / cm 2 When the cathode electrolyte is a conventional electrolyte, the maximum power density of the sodium-carbon dioxide battery is 2.26 mW / cm 2As shown in Figure 5, when the cathode electrolyte is a high-concentration high-entropy electrolyte, the rate performance of the sodium-carbon dioxide battery is significantly better than when the cathode electrolyte is a traditional electrolyte; in addition, when the current density increases to 2 mA / cm 2 When the electrolyte is high, the sodium-carbon dioxide battery using the traditional electrolyte can no longer operate normally, while the sodium-carbon dioxide battery using the high-concentration high-entropy electrolyte still has excellent charge and discharge performance. It can be seen that the performance of the sodium-carbon dioxide battery using the high-concentration high-entropy electrolyte as the positive electrode electrolyte in this embodiment is better than that of the sodium-carbon dioxide battery using the traditional electrolyte as the positive electrode electrolyte.

[0048] Example 2:

[0049] In this embodiment, two sodium-carbon dioxide batteries are provided for comparison experiments. The two sodium-carbon dioxide batteries include, from the negative electrode part A to the positive electrode part C, a metallic sodium negative electrode A1, a negative electrode electrolyte A2, a solid electrolyte membrane B, a positive electrode electrolyte C1, and a catalyst layer C2. Among them, the metal negative electrode A1 is a metal sodium sheet with a thickness of 1 mm and a diameter of 10 mm; the negative electrode electrolyte A2 is 1 mol / LNaClO4 / [(EC+DMC)(1:1)+1 vol%FEC]; the solid electrolyte membrane B is a NASICON type fast ion conductor with a thickness of 1 mm and a diameter of 16 mm; the positive electrode electrolyte of one sodium-carbon dioxide battery is a high-concentration high-entropy electrolyte, which is prepared by dissolving 5 solute salts of 27M NaFSI, 2M NaClO4, 2M NaCl, 2M NaNO3, and 2M NaI in deionized water according to the above preparation method; the positive electrode electrolyte of another sodium-carbon dioxide battery is a traditional electrolyte, which is 18M NaClO4 is dissolved in deionized water and prepared according to the above preparation method; the catalytic layer is formed by pressing carbon paper loaded with a catalyst and nickel foam, the carbon paper loaded with the catalyst is porous hydrophilic carbon paper with a diameter of 10 mm and a thickness of 0.5 mm, the catalyst is 5% Ru / C, and the nickel foam has a thickness of 1 mm and a diameter of 10 mm.

[0050] The two sodium-carbon dioxide batteries assembled in this embodiment were subjected to performance tests at a constant temperature of 30°C and pure CO2. The discharge capacity curves are shown in FIG6 . When the positive electrode electrolyte is a high-concentration high-entropy electrolyte, the discharge capacity of the sodium-carbon dioxide battery is 44.85 mAh / cm 2 When the cathode electrolyte is a conventional electrolyte, the discharge capacity of the sodium-carbon dioxide battery is 10.67 mAh / cm 2. In addition, as shown in Figure 7, when the positive electrode electrolyte is a traditional electrolyte, the residual amount of metallic sodium in the negative electrode of the sodium-CO2 battery is significantly lower than the residual amount when the positive electrode electrolyte is a high-concentration high-entropy electrolyte, which significantly improves the utilization rate of the metallic sodium in the negative electrode. It can be seen that the performance of the sodium-CO2 battery using the high-concentration high-entropy electrolyte as the positive electrode electrolyte in this embodiment is better than that of the sodium-CO2 battery using the traditional electrolyte as the positive electrode electrolyte.

[0051] Example 3:

[0052] In this embodiment, two sodium-carbon dioxide batteries are provided for comparative experiments. The two sodium-carbon dioxide batteries include a metal sodium negative electrode A1, a negative electrode electrolyte A2, a solid electrolyte membrane B, a positive electrode electrolyte C1, and a catalyst layer C2 in order from the negative electrode part A to the positive electrode part C. The metal negative electrode A1 is a metal sodium sheet with a thickness of 1 mm and a diameter of 10 mm; the negative electrode electrolyte A2 is 1 mol / L NaClO4 / [(EC+DMC)(1:1)+1 vol% FEC]; the solid electrolyte membrane B is a NASICON type fast ion conductor with a thickness of 1 mm and a diameter of 16 mm; the positive electrode electrolyte of one of the sodium-carbon dioxide batteries is a high-concentration high-entropy electrolyte, which is composed of 23M NaFSI, 3M NaClO4, 3M NaCl, 3M NaNO3, 3M NaI Five solute salts are dissolved in deionized water and prepared according to the above preparation method; the positive electrode electrolyte of another sodium-carbon dioxide battery is a traditional electrolyte, which is a saturated sodium chloride solution; the catalytic layer is formed by pressing carbon paper loaded with a catalyst and nickel foam, the carbon paper loaded with the catalyst is porous hydrophilic carbon paper with a diameter of 10 mm and a thickness of 0.5 mm, the catalyst is 5% Ru / C, and the nickel foam has a thickness of 1 mm and a diameter of 10 mm.

[0053] The two sodium-carbon dioxide batteries assembled in this embodiment were subjected to performance tests at a constant temperature of 30°C and pure CO2. The cycle curves are shown in Figure 8. When the positive electrode electrolyte is a high-concentration high-entropy electrolyte, the cycle number of the sodium-carbon dioxide battery is as high as 374 times; and when the positive electrode electrolyte is a traditional electrolyte, the cycle number of the sodium-carbon dioxide battery is as high as 108 times. It can be seen that the performance of the sodium-carbon dioxide battery using the high-concentration high-entropy electrolyte as the positive electrode electrolyte in this embodiment is better than that of the sodium-carbon dioxide battery using the traditional electrolyte as the positive electrode electrolyte.

[0054] Example 4:

[0055] In this embodiment, two sodium-carbon dioxide batteries are provided for comparative experiments. The two sodium-carbon dioxide batteries include, from the negative electrode part A to the positive electrode part C, a metal sodium negative electrode A1, a negative electrode electrolyte A2, a solid electrolyte membrane B, a positive electrode electrolyte C1, and a catalyst layer C2. The metal negative electrode A1 is a metal sodium sheet with a thickness of 1 mm and a diameter of 10 mm; the negative electrode electrolyte A2 is 1 mol / L NaClO4 / [(EC+DMC)(1:1)+1 vol% FEC]; the solid electrolyte membrane B is a NASICON type fast ion conductor with a thickness of 1 mm and a diameter of 16 mm; the positive electrode electrolyte of one of the sodium-carbon dioxide batteries is a high-concentration high-entropy electrolyte, which is composed of 20M NaFSI, 4M NaClO4, 4M NaCl, 4M NaNO3, 3M NaI Five solute salts are dissolved in deionized water and prepared according to the above preparation method; the positive electrode electrolyte of another sodium-carbon dioxide battery is a traditional electrolyte, which is a saturated sodium perchlorate solution; the catalytic layer is formed by pressing carbon paper loaded with a catalyst and nickel foam, the carbon paper loaded with the catalyst is porous hydrophilic carbon paper with a diameter of 10 mm and a thickness of 0.5 mm, the catalyst is 5% Ru / C, and the nickel foam has a thickness of 1 mm and a diameter of 10 mm.

[0056] The two sodium-carbon dioxide batteries assembled in this embodiment were fully discharged at a constant temperature of 30°C and pure CO2. As shown in Figure 9, the catalyst layer after the battery discharge was detected using Raman spectroscopy and it was found that when the positive electrode electrolyte was a traditional electrolyte, the discharge product of the battery was Na2CO3. As shown in Figure 10, the electrolyte after the battery discharge was detected using nuclear magnetic resonance hydrogen spectroscopy and it was found that when the positive electrode electrolyte was a high-concentration high-entropy electrolyte, the discharge product of the battery was liquid formic acid. It can be seen that the discharge product of the sodium-carbon dioxide battery using the high-concentration high-entropy electrolyte as the positive electrode electrolyte in this embodiment is formic acid. As a liquid, it will not clog the catalyst layer and cause battery failure, thereby ensuring the performance of the sodium-carbon dioxide battery using a high-concentration high-entropy electrolyte.

[0057] Although the present invention has been described above with reference to the exemplary embodiments, it will be apparent to those skilled in the art that various modifications and variations may be made to the exemplary embodiments of the present invention without departing from the spirit and scope defined in the claims.

Claims

1. A high-concentration high-entropy electrolyte, characterized in that: The high-concentration high-entropy electrolyte includes a solvent, a first solute salt, and an added salt, wherein the first solute salt is a solute salt having high solubility in the solvent, and the added salt is three or more solute salts; the molar concentration range of the solute salt in the high-concentration high-entropy electrolyte is 20M-60M, the molar concentration of the first solute salt exceeds 20M, and the molar concentration of the first solute salt accounts for more than 50% of the molar concentration of the high-concentration high-entropy electrolyte.

2. The high-concentration high-entropy electrolyte according to claim 1, characterized in that: The sum of the molar concentrations of the added salts is less than 50% of the molar concentration of the high-concentration high-entropy electrolyte, and the addition ratio of the added salts is calculated based on the solubility of the solute salt in the solvent.

3. The high-concentration high-entropy electrolyte according to claim 1, characterized in that: The solvent is an organic solvent or an inorganic solvent.

4. The high-concentration high-entropy electrolyte according to claim 3, characterized in that: The organic solvent is at least one of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, alcohols, ethers, esters, ketones, diol derivatives, acetonitrile, pyridine, and phenol.

5. The high-concentration high-entropy electrolyte according to claim 3, characterized in that: The inorganic solvent is at least one of an acidic solvent, a basic solvent, an amphoteric solvent, and an inert solvent.

6. The high-concentration high-entropy electrolyte according to claim 1, characterized in that: The solute salt includes an organic salt or an inorganic salt.

7. The high-concentration high-entropy electrolyte according to claim 1, characterized in that: The first solute salt is one of sodium fluorosulfonyl imide (NaFSI), lithium bis(trifluoromethanesulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and zinc chloride (ZnCl2); the added salt is at least three of lithium nitrate (LiNO3), sodium nitrate (NaNO3), sodium perchlorate (NaClO4), lithium perchlorate (LiClO4), sodium chloride (NaCl), lithium chloride (LiCl), and sodium iodide (NaI).

8. A method for preparing a high-concentration high-entropy electrolyte, characterized in that: The following steps are involved: S1, selecting a solute salt with high solubility as a first solute salt, and calculating and weighing the required mass of the first solute salt according to a preset molar concentration, dissolving it in a solvent, and heating to obtain a basic high-concentration electrolyte; S2, selecting three or more solute salts as added salts, and calculating and weighing the required added salts according to the preset molar concentration, dissolving them in the basic high-concentration electrolyte in step S1, and heating them so that the added salts are completely dissolved to obtain a mixed high-concentration electrolyte; S3, subjecting the mixed high-concentration electrolyte in step S2 to ultrasonic treatment in an ultrasonic instrument to ensure that the components in the mixed high-concentration electrolyte are completely mixed, and cooling to room temperature to obtain a high-concentration high-entropy electrolyte.

9. The method for preparing a high-concentration high-entropy electrolyte according to claim 8, characterized in that: The molar concentration of the solute salt in the high-concentration high-entropy electrolyte is in the range of 20M-60M, the molar concentration of the first solute salt exceeds 20M, and the molar concentration of the first solute salt accounts for more than 50% of the total molar concentration of the high-concentration high-entropy electrolyte; the sum of the molar concentrations of the added salts is less than 50% of the total molar concentration of the high-concentration high-entropy electrolyte.

10. A sodium-carbon dioxide battery, characterized in that: The sodium-carbon dioxide battery comprises a metallic sodium negative electrode, a negative electrode electrolyte, a solid electrolyte membrane, a positive electrode electrolyte, and a catalyst layer arranged in sequence; the metallic sodium negative electrode is a metallic sodium sheet, the negative electrode electrolyte is an ester electrolyte of 1 mol / L NaClO4 / [(EC+DMC)(1:1)+1 vol% FEC], wherein 1:1 is a volume ratio; the solid electrolyte membrane is Na3Zr2Si2PO 12 NASICON structure fast ion conductor; the positive electrode electrolyte is a high-concentration high-entropy electrolyte prepared according to the high-concentration high-entropy electrolyte according to any one of claims 1 to 7 or the preparation method of the high-concentration high-entropy electrolyte according to any one of claims 8 to 9; the catalytic layer is formed by pressing carbon paper and nickel foam loaded with a catalyst, and the catalyst is a 5% Ru / C catalyst.

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