Metal-sulfur battery electrolyte and metal-sulfur battery

Abstract

The invention discloses a metal-sulfur battery electrolyte and a metal-sulfur battery. The metal-sulfur battery electrolyte comprises metal salt, an organic solvent and an additive, the additive is an organic compound containing phenyl and selenic acid groups or seleninic acid groups, and the concentration range of the additive in the metal-sulfur battery electrolyte is 0.5-3 wt%. The metal-sulfur battery comprises the electrolyte solution. The additive of the metal-sulfur battery electrolyte provided by the invention can inhibit the occurrence of a polysulfide shuttle effect and a metal negative electrode dendritic crystal phenomenon, and improve the cycle life and the capacity retention rate of a metal-sulfur battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal-sulfur battery electrolytes, and in particular relates to a metal-sulfur battery electrolyte and a metal-sulfur battery. Background Art

[0002] With the increasing popularity of portable electronics and the electrification of automobiles, the energy storage market has placed higher demands on high-energy-density energy storage devices. Lithium-ion batteries face the growing market demand for high-energy-density storage, leaving little room for improvement. Metal-sulfur batteries, with their high energy density and low cost, are widely considered a strong contender for next-generation battery technology. Sulfur is abundant and inexpensive, offering significant cost advantages. Furthermore, its environmentally friendly materials align with sustainable and green development requirements. Despite this, metal-sulfur batteries still face numerous development challenges. Sulfur has poor conductivity and a volume expansion effect, which can lead to structural instability in the positive electrode, impacting the battery's long-term cycle stability. The oxidation kinetics of the sulfur positive electrode itself are slow. During charge and discharge, sulfur is converted into highly conductive, soluble polysulfide intermediates, which migrate within the battery, resulting in irreversible loss of battery capacity and reduced efficiency, reducing cycle stability – the infamous "shuttle effect." Metal-sulfur batteries also face complex interface issues between the positive electrode, electrolyte, and negative electrode. On metal surfaces like lithium, sulfur can react with polysulfides, leading to irreversible chemical changes and the formation of "dead sulfur." Summary of the Invention

[0003] The object of the present invention is to provide a metal-sulfur battery electrolyte and a metal-sulfur battery based on the electrolyte, which are used to inhibit the occurrence of polysulfide shuttle effect and metal negative electrode dendrite phenomenon, and improve the cycle life and capacity retention rate of the metal-sulfur battery.

[0004] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0005] In a first aspect, the present invention provides a metal-sulfur battery electrolyte, comprising a metal salt, an organic solvent, and an additive, wherein the additive is an organic compound containing a phenyl group and a selenate group or a selenite group, and the concentration range of the additive in the metal-sulfur battery electrolyte is 0.005-0.03 g / mL.

[0006] Preferably, the additive is selected from phenylselenic acid, phenylselenic anhydride, 4-chlorophenylselenic acid, 4-bromophenylselenic acid, 4-fluorophenylselenic acid or phenylmethaneselenic acid.

[0007] In the present invention, the metal negative electrode in the metal-sulfur battery can be lithium, sodium, magnesium, etc. The metal salt is determined according to the metal negative electrode in the metal-sulfur battery, and the two need to be consistent. The solvent can also be determined accordingly. For example, it can be selected from at least one of 1,2-dimethoxyethane, 1,3-dioxolane, ethylene carbonate, and propylene carbonate. The metal salt concentration in the electrolyte can be set to 1 to 2 mol. When the metal-sulfur battery is a lithium-sulfur battery, the metal salt can be at least one of lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium nitrate (LiNO3), lithium perchlorate (LiClO4), etc. The solvent is a mixture of 1,2-dimethoxyethane and 1,3-dioxolane, and the volume ratio of the two is selected to be 1:0.5-2. When the metal-sulfur battery is a sodium-sulfur battery, the metal salt may be at least one of sodium perchlorate (NaClO4), sodium bis(trifluoromethylsulfonyl)imide (NaTFSI), sodium hexafluorophosphate (NaPF6), etc., and the solvent may be a mixture of ethylene carbonate and propylene carbonate, with the volume ratio of the two being 1:0.5-2. When the metal-sulfur battery is a magnesium-sulfur battery, the metal salt may be magnesium bis(trifluoromethylsulfonyl)imide, magnesium perfluoroalkyl borate (Mg(CB9H 10 )2), at least one of an organic magnesium salt such as hexamethyldiazaboryl magnesium (Mg(HMDS)2), etc., the solvent can be a mixture of 1,2-dimethoxyethane and 1,3-dioxolane, and the volume ratio of the two is selected to be 1:0.5-2.

[0008] The electrolyte of the present invention can be prepared by conventional methods, such as placing the components under a protective gas atmosphere (such as argon), uniformly mixing, stirring, and allowing to stand at concentrations of less than 0.01 ppm for both H₂O and O₂. Molecular sieves may be added during storage to remove water.

[0009] In a second aspect, the present invention provides a metal-sulfur battery comprising the electrolyte described in the first aspect.

[0010] The metal-sulfur battery described in the present invention generally includes a sulfur positive electrode, a metal negative electrode, a separator, and an electrolyte commonly used in the literature. The metal negative electrode can be a lithium negative electrode, a sodium negative electrode, a magnesium negative electrode, etc. The sulfur positive electrode is obtained by coating a positive electrode slurry containing a positive electrode material, a conductive agent, and a binder onto a current collector and drying it. The positive electrode material can be an S / C material, an organic sulfide, or a metal sulfide. The S / C material can be an S / C material derived from a sulfur-containing metal-organic framework (MOF), or can be obtained by mixing a sulfur source and a carbon source and then calcining them. The sulfur source can be sublimated sulfur, a sulfide precursor, a sulfurized polymer, etc. The carbon source can be conductive carbon black (Katjenblack, Super P), carbon nanotubes (CNTs), porous carbon derived from a metal-organic framework (MOF-C), biomass carbon, etc. As a specific embodiment, the S / C material is obtained by ball-milling sulfur powder and Ketjen black in a mass ratio of 70-80%:30-20%, and then calcining at 150-160°C for 8-12 hours under an inert atmosphere. The conductive agent can be at least one of Super P, Katjenblack, CNTs, graphene, etc., and the binder can be at least one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), sodium alginate (SA), etc. The sulfur loading on the sulfur positive electrode is 0.5-5 mg cm -2 The diaphragm material is a conventional diaphragm material, such as polypropylene.

[0011] Compared with the prior art, the present invention has the following advantages:

[0012] The present invention adds an organic compound containing phenylselenic acid or phenylselenoic acid groups as an electrolyte additive, which acts as a redox medium in the electrolyte system to mediate the polysulfide conversion kinetics; by introducing selenium with high electron transport performance, the battery impedance and charge and discharge overpotential are reduced, the charge transfer rate between the positive electrode and the electrolyte is increased, and the battery performance is improved; the polysulfide adsorption capacity is enhanced, the "shuttle effect" is effectively suppressed, and the battery capacity retention rate is improved; and the SEI film components on the metal negative electrode surface are participated in the formation to form a uniform and dense oxide layer, which can effectively protect the lithium negative electrode surface from corrosion and suppress the growth of lithium dendrites, thereby improving the cycle stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figures 1a-1c is a long cycle diagram of some embodiments and comparative examples, wherein Figures 1a-1c The charge and discharge efficiency curves correspond to the batteries of Example 1, Example 8, and Example 13, respectively;

[0014] Figure 2 Cyclic voltammograms for different electrolyte systems;

[0015] Figure 3 Calculate the LUMO energy levels of organic solvents and phenylselenous acid for DFT;

[0016] Figure 4 These are SEM images of the metal negative electrode after 50 cycles, including (a) Example 1; (b) Example 8; (c) Example 13; (d) Example 2;

[0017] Figure 5 XPS test of the lithium negative electrode of Comparative Example 1 and Example 1 after 50 cycles; (a) full spectra of Comparative Example 1 and Example 1; (b) S2p, (c) Se 3d, and (d) C 1s spectra of Example 1; (e) S2p spectrum of Comparative Example 1;

[0018] Figure 6 FTIR graphs of the lithium polysulfide solution in Example 18 without and with phenylselenous acid added. DETAILED DESCRIPTION

[0019] In order to facilitate understanding of the present invention, the technical solution of the present invention is fully and completely described below in conjunction with the embodiments. Obviously, the protection scope of the present invention is not limited to the embodiments.

[0020] Currently, metal-sulfur batteries suffer from slow redox kinetics, the notorious polysulfide "shuttle effect," and the growth of metal dendrites such as lithium, which seriously affect the battery's long cycle life and cycling stability. Specifically, polysulfides, intermediate products of charge and discharge, are soluble and spontaneously migrate from the positive electrode to the negative electrode in the electrolyte. Their high reactivity leads to irreversible chemical reactions with the metal negative electrode, resulting in irreversible loss of active materials and metals such as lithium, forming "dead sulfur" and "dead lithium," which reduces battery capacity retention and makes it difficult to maintain cycling stability.

[0021] To address the above problems, electrolyte additives are used to adsorb polysulfides, catalyze the kinetics of sulfur redox reactions, and inhibit the formation of metal dendrites to improve the energy density of metal-sulfur batteries.

[0022] The present invention provides an electrolyte for a metal-sulfur battery, comprising a metal salt, a solvent and an additive. The additive is an organic compound containing a phenyl group and a selenic acid group or a selenious acid group, including but not limited to phenylselenic acid, phenylselenic anhydride, 4-chlorophenylselenic acid (chlorine can be replaced by other halogen atoms), and phenylmethaneselenic acid.

[0023] According to the embodiments of the present application, additives such as phenylselenic acid and phenylselenoic acid have a strong adsorption effect on polysulfides, which can effectively inhibit the shuttle effect of polysulfides. At the same time, the additives participate in the composition of the SEI film on the surface of the metal negative electrode, maintain the uniform and stable morphology and structure of the metal negative electrode after cycling, protect the surface of the metal negative electrode from corrosion, and improve the battery cycle stability; at the same time, promote the conversion kinetics of polysulfides and increase the redox rate.

[0024] In some embodiments, the metal negative electrode is selected from lithium, sodium, and magnesium.

[0025] In some embodiments, the mass volume concentration of the additive in the electrolyte is 0.005-0.03 g / mL.

[0026] In some embodiments, the organic solvent includes but is not limited to a mixture of 1,2-dimethoxyethane and 1,3-dioxolane in a volume ratio of 1:1; and a mixture of ethylene carbonate and propylene carbonate in a volume ratio of 1:1.

[0027] In some embodiments, the metal salt is selected from lithium bis(trifluoromethyl)sulfonyl imide, sodium perchlorate, and magnesium bis(trifluoromethyl)sulfonyl imide, and the specific concentration of the metal salt in the electrolyte is 1 mol / L.

[0028] An embodiment of the present application provides a method for preparing an electrolyte for improving the cycle life and capacity retention rate of a lithium-sulfur battery, namely, under an argon atmosphere and under environmental conditions where the concentrations of H2O and O2 are both less than 0.01 ppm, an organic solvent and a metal salt are uniformly mixed and stirred thoroughly for complete dissolution to obtain a blank electrolyte, an additive is then added to obtain an electrolyte, and finally a molecular sieve is added and allowed to stand for 12 hours to remove residual water molecules in the solution.

[0029] According to the embodiments of the present application, the obtained electrolyte has high cycle stability and suppresses the shuttle effect of polysulfides.

[0030] The present application provides a metal-sulfur battery comprising a positive electrode, a negative electrode, a separator and the above-mentioned electrolyte.

[0031] According to an embodiment of the present application, the positive electrode is composed of an active material, a conductive agent, a binder, and a current collector. Specifically, the active material is an S / C material, and the mass ratio of S and C in the S / C material is 7:3; the conductive agent is Super P; the binder is polyvinylidene fluoride; the mass ratio of the active material, the conductive agent, and the binder is 7:2:1; and the current collector is carbon-coated aluminum foil.

[0032] In some embodiments, the negative electrode is metallic lithium, metallic sodium, or metallic magnesium.

[0033] In some embodiments, the septum is polypropylene.

[0034] The following examples further describe the disclosure of this application. These examples are for illustrative purposes only. All reagents used in the examples are commercially available or synthesized according to conventional methods, and the instruments used in the examples are commercially available. To better illustrate the different implementation methods of the examples, the examples are divided into three types of batteries for illustration: lithium-sulfur batteries, sodium-sulfur batteries, and magnesium-sulfur batteries.

[0035] Comparative Example 1

[0036] Under an argon atmosphere, the concentrations of H2O and O2 were both less than 0.01 ppm. In a glove box, 2.87 g of lithium bis(trifluoromethyl)sulfonyl imide was weighed and added to a 10 mL volumetric flask. 10 mL of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio of 1:1) were measured and added to the volumetric flask. The mixture was stirred until the lithium salt was completely dissolved. 2 g of 3A molecular sieves was added, and the mixture was allowed to stand in the glove box for 12 h to obtain an electrolyte.

[0037] The preparation method of the sulfur positive electrode is as follows: sulfur powder and Ketjen black are uniformly mixed in a mass ratio of 7:3, ball milled at 500 rpm for 2 hours, and calcined at 155°C in an argon atmosphere for 10 hours to obtain an S / C material; the S / C material, conductive agent Super P, and binder polyvinylidene fluoride are stirred and mixed in an N-methylpyrrolidone (NMP) solvent in a mass ratio of 7:2:1 to obtain a positive electrode slurry, which is coated on a current collector (carbon-coated aluminum foil) and dried at 60°C for 12 hours in a vacuum environment to obtain a positive electrode sheet. The sulfur loading on the sulfur positive electrode is 2 mg cm -2 .

[0038] A button cell was prepared in a glove box. The above-mentioned sulfur positive electrode was used as the positive electrode, the positive electrode sheet had a diameter of 12 mm, a polypropylene separator was used as the diaphragm, and the negative electrode was metallic lithium with a diameter of 16 mm.

[0039] Examples 1-7

[0040] This embodiment provides a method for preparing an electrolyte for improving the cycle life and capacity retention rate of a lithium-sulfur battery.

[0041] Under argon atmosphere, H2O and O2 concentrations were less than 0.01ppm. 2.87g of lithium bis(trifluoromethyl)sulfonyl imide was weighed in a glove box and added to a 10mL volumetric flask. 10mL of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio of 1:1) are added to a volumetric flask and stirred until the lithium salt is completely dissolved. Then, additives are added respectively to prepare electrolytes with different additive concentrations, wherein the additives in each embodiment are phenylselenous acid (Example 1, 0.05 g), phenylselenic acid (Example 2, 0.05 g), phenylselenic anhydride (Example 3, 0.05 g), 4-chlorophenylselenic acid (Example 4, 0.05 g), phenylmethaneselenic acid (Example 5, 0.05 g), phenylselenic acid (Example 6, 0.1 g), and phenylselenic acid (Example 7, 0.3 g). The mixture is evenly mixed by magnetic stirring, 3A molecular sieves are added, and the mixture is allowed to stand for 12 h to obtain an electrolyte. The supernatant in the volumetric flask can be taken for subsequent use.

[0042] The above electrolyte was used to prepare button batteries in a glove box, and the preparation method was the same as that of Comparative Example 1.

[0043] Comparative Example 2: Sodium-sulfur battery

[0044] Under an argon atmosphere, the concentrations of H2O and O2 were both less than 0.01 ppm. In a glove box, 1.22 g of sodium perchlorate was weighed and added to a volumetric flask. 10 mL of ethylene carbonate and propylene carbonate (volume ratio of 1:1) were measured and added to a 10 mL volumetric flask. The mixture was stirred until the sodium salt was completely dissolved. 2 g of 3A molecular sieve was added, and the mixture was allowed to stand in the glove box for 12 h to obtain an electrolyte.

[0045] The above electrolyte was used to prepare button batteries in a glove box, and the preparation method was the same as that of Comparative Example 1.

[0046] Examples 8-12: Sodium-sulfur batteries

[0047] This embodiment provides a method for preparing an electrolyte for improving the cycle life and capacity retention rate of a sodium-sulfur battery.

[0048] Under an argon atmosphere, the concentrations of H2O and O2 were both less than 0.01ppm. 1.22g of sodium perchlorate was weighed in a glove box and added to a volumetric flask. 10mL of ethylene carbonate and propylene carbonate (volume ratio of 1:1) were measured and added to a 10mL volumetric flask. The mixture was stirred until the sodium salt was completely dissolved, and then 0.05g of additives were added to prepare electrolytes with different concentrations of additives. The additives were phenylselenous acid (Example 8), phenylselenic acid (Example 9), phenylselenic anhydride (Example 10), 4-chlorophenylselenic acid (Example 11), and phenylmethaneselenic acid (Example 12). The mixture was evenly mixed by magnetic stirring, and molecular sieves were added and allowed to stand for 12h to obtain an electrolyte containing additives.

[0049] The above electrolyte was used to prepare button batteries in a glove box, and the preparation method was the same as that of Comparative Example 1.

[0050] Comparative Example 3: Magnesium-sulfur battery

[0051] Under an argon atmosphere, the concentrations of H2O and O2 were both less than 0.01 ppm. In a glove box, 5.84 g of magnesium bis(trifluoromethyl)sulfonyl imide was weighed and added to a volumetric flask. 10 mL of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio of 1:1) were measured and added to a 10 mL volumetric flask. The mixture was stirred until the magnesium salt was completely dissolved. 2 g of 3A molecular sieves was added, and the mixture was allowed to stand in the glove box for 12 h to obtain an electrolyte.

[0052] The above electrolyte was used to prepare button batteries in a glove box, and the preparation method was the same as that of Comparative Example 1.

[0053] Examples 13-17: Magnesium-sulfur battery

[0054] This embodiment provides a method for preparing an electrolyte for improving the cycle life and capacity retention rate of a magnesium-sulfur battery.

[0055] Under an argon atmosphere, the concentrations of H2O and O2 were both less than 0.01ppm. 5.84g of magnesium bis(trifluoromethyl)sulfonyl imide was weighed in a glove box and added to a volumetric flask. 10mL of 1,2-dimethoxyethane and 1,3-dioxolane (volume ratio of 1:1) were measured and added to a 10mL volumetric flask. The mixture was stirred until the magnesium salt was completely dissolved, and then 0.05g of additives were added to prepare electrolytes with additives of different concentrations. The additives were phenylselenous acid (Example 13), phenylselenic acid (Example 14), phenylselenic anhydride (Example 15), 4-chlorophenylselenic acid (Example 16), and phenylmethaneselenic acid (Example 17). The mixture was evenly mixed by magnetic stirring, and 2g of 3A molecular sieves were added and allowed to stand for 12h to obtain an electrolyte containing additives.

[0056] The above electrolyte was used to prepare button batteries in a glove box, and the preparation method was the same as that of Comparative Example 1.

[0057] Example 18

[0058] Under argon atmosphere, in a glove box where the concentrations of H2O and O2 in the environment were less than 0.01 ppm, 0.023 g of lithium sulfide and 0.64 g of sublimed sulfur were weighed in a molar ratio of 1:5, and dissolved in a 10 mL volumetric flask with 10 mL of DME solvent. The mixture was heated at 60 °C for 12 h to obtain a 0.05 M lithium polysulfide solution.

[0059] The prepared lithium polysulfide solution was divided into two 5 ml volumetric flasks, and 0.05 g of phenylselenous acid was added to one of the volumetric flasks. The solution was allowed to stand for 3 hours until the solution was clear, and the supernatant was taken for FT-IR analysis. The lithium polysulfide solution without phenylselenous acid was tested directly after the solution was divided. The results are as follows: Figure 6 As shown in the figure, after adding phenylselenous acid to the 0.05 mol / L Li2S6 solution, the characteristic peak intensity of the SS bond corresponding to the long-chain polysulfide decreased significantly, proving that the addition of the additive significantly inhibited the shuttle effect of the polysulfide.

[0060] The batteries obtained from the above examples and comparative examples were subjected to electrochemical tests. The electrochemical test methods are as follows: constant current charge and discharge tests were performed using a LAND test system (CT2001A), with the voltage window selected between 1.7 and 2.8 V and the test current being 0.2 C. Electrochemical impedance spectroscopy (EIS) analysis was performed using an Ivium electrochemical workstation with a frequency range of 0.01 Hz to 100 kHz and an amplitude of 5 mV. Cyclic voltammetry (CV) tests were performed using an Ivium electrochemical workstation with a voltage range of 1.7 to 2.8 V and a scan rate of 0.1 mV·s. -1 The above electrochemical tests were all performed at room temperature (25°C).

[0061] Computational chemistry testing methods are as follows: Density Funcional Theory (DFT) was used for computational analysis, using Materials Studio as the testing software. Molecular structure optimization was performed using the DMOL3 module, with GGA and BLYP as functionals. Energy calculations were performed on the optimized molecules in DMOL3, using GGA and BLYP as functionals, and using Fukui functions and Orbitals as calculation functions.

[0062] The test results are shown in Table 1 and the accompanying drawings. Figure 1a-Figure 1c The long cycle diagrams of some examples after adding additives are shown. For example, in Example 1a, after adding phenylselenous acid, the first cycle charge and discharge capacity of the lithium-sulfur battery is 1120 mAh g -1 , the capacity retention rate after 100 cycles is 83.43%, which has an excellent cycle capacity retention rate. Figure 3 The frontier orbital theory of DFT calculation of phenylselenous acid and organic solvent in Example 1 shows that phenylselenous acid has a lower LUMO value and undergoes reduction reaction on the negative electrode side before the organic solvent to form a passivation layer, and selenium participates in the formation of the SEI film. Figure 5 Shows the XPS spectrum of the metal anode before and after cycling. Figure 5c is the Se 3d spectrum after 50 cycles of adding phenylselenous acid electrolyte. As shown in the figure, Se-O bonds exist on the surface of the lithium negative electrode, proving that phenylselenous acid participates in the film formation on the negative electrode surface and Figure 5 The S2p spectrum of the lithium negative electrode without adding phenylselenous acid shown in b and Figure 5 Compared with the S2p spectrum of the negative electrode with added lithium phenylselenite shown in e, the addition of the additive effectively reduces the deposition of short-chain polysulfides such as Li2S at the negative electrode, proving that it has an inhibitory effect on the shuttle effect of polysulfides. Figure 4 It can be seen that after adding additives, the structure of the metal negative electrode remains good, smooth and complete after cycling.

[0063] Table 1 Comparison of electrochemical performance of three types of battery systems Examples 1-15 and Comparative Examples 1-3

[0064]

[0065]

[0066] As shown in Table 1, in the three metal-sulfur battery systems, after adding additives containing phenylselenic acid and phenylselenous acid groups, the specific capacity and cycle retention rate of the battery remained at a high level, proving that it improves the cycle life and capacity retention rate of the battery in the metal-sulfur battery system. It is suitable for the metal-sulfur battery system. Through the introduction of additives, the electrolyte material is optimized, and it has great development potential, which may provide new solutions and ideas for large-scale use in the future.

Claims

1. A metal-sulfur battery electrolyte, characterized in that: The metal-sulfur battery electrolyte comprises a metal salt, an organic solvent and an additive, wherein the additive is an organic compound containing a phenyl group and a selenic acid group or a selenious acid group, and the concentration range of the additive in the metal-sulfur battery electrolyte is 0.005-0.03 g / mL.

2. The metal-sulfur battery electrolyte according to claim 1, wherein: The additive is selected from phenylselenic acid, phenylselenic anhydride, 4-chlorophenylselenic acid, 4-bromophenylselenic acid, 4-fluorophenylselenic acid or phenylmethaneselenic acid.

3. The metal-sulfur battery electrolyte according to claim 1, wherein: The metal negative electrode in the metal-sulfur battery is lithium, sodium or magnesium.

4. The metal-sulfur battery electrolyte according to claim 3, wherein: When the metal-sulfur battery is a lithium-sulfur battery, the metal salt is at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium nitrate, and lithium perchlorate, and the solvent is a mixture of 1,2-dimethoxyethane and 1,3-dioxolane, and the volume ratio of the two is 1:0.5-2; when the metal-sulfur battery is a sodium-sulfur battery, the metal salt is at least one of sodium perchlorate, sodium bis(trifluoromethylsulfonyl)imide, and sodium hexafluorophosphate, and the solvent is a mixture of ethylene carbonate and propylene carbonate, and the volume ratio of the two is 1:0.5-2; when the metal-sulfur battery is a magnesium-sulfur battery, the metal salt is at least one of magnesium bis(trifluoromethylsulfonyl)imide, magnesium perfluoroalkyl borate, and hexamethyldiazaboryl magnesium, and the solvent is a mixture of 1,2-dimethoxyethane and 1,3-dioxolane, and the volume ratio of the two is 1:0.5-2.

5. The metal-sulfur battery electrolyte according to any one of claims 1 to 4, characterized in that: The concentration of the metal salt in the electrolyte can be set to 1-2 mol.

6. A metal-sulfur battery comprising the electrolyte according to any one of claims 1 to 4.

7. The metal-sulfur battery according to claim 6, wherein: The metal-sulfur battery includes a sulfur positive electrode, a metal negative electrode, a separator and an electrolyte; the sulfur positive electrode is obtained by coating a positive electrode slurry containing a positive electrode material, a conductive agent and a binder onto a current collector and drying it, and the positive electrode material is an S / C material, an organic sulfide or a metal sulfide.

8. The metal-sulfur battery according to claim 7, wherein: The S / C material is obtained by mixing sulfur powder and Ketjen black in a mass ratio of 70-80%:30-20% by ball milling, and then calcining at 150-160° C. for 8-12 hours in an inert atmosphere.

9. The metal-sulfur battery according to claim 7 or 8, characterized in that: The sulfur loading on the sulfur positive electrode is 0.5-5 mg cm -2 .

10. The metal-sulfur battery according to claim 7, wherein: The conductive agent is at least one of Super P, Katjenblack, CNTs, and graphene; the binder is at least one of polyvinylidene fluoride, carboxymethyl cellulose, polyacrylic acid, and sodium alginate; and the diaphragm material is polypropylene.

Images