Binary solvent electrolyte and application thereof

Abstract

The invention provides a binary solvent electrolyte and application thereof. The binary solvent system adopts the combination of the strong solvating solvent and the weak solvating solvent, and the strong solvating characteristic not only has excellent lithium salt dissociation capacity, but also can promote efficient migration and transmission of lithium ions, so that the conversion kinetics of lithium polysulfide (LiPSs) is improved; the weak solvation characteristic can effectively inhibit the dissolution and shuttling of LiPSs, and improves the interface compatibility with a lithium metal negative electrode. According to the binary solvent electrolyte, through the synergistic combination of the binary solvents, the shuttle effect of lithium polysulfide can be effectively inhibited, the conversion reaction kinetics of lithium polysulfide can be remarkably improved, meanwhile, the side reaction of the electrolyte to a lithium metal negative electrode is greatly reduced, and the lithium-sulfur battery prepared by adopting the electrolyte system has the advantages that the stability is high, and the service life is long. The characteristics of high specific capacity, long cycle stability and the like are shown. The invention provides an electrolyte solution with important application value for developing a high-performance and long-life lithium-sulfur battery.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to a binary solvent electrolyte and its application. Background Technology

[0002] Lithium-sulfur batteries boast high theoretical energy density (2600 Wh kg). -1 Lithium trifluoromethanesulfonylimide (LiTFSI) is considered one of the most promising next-generation energy storage systems. Currently used electrolytes primarily consist of lithium bis(trifluoromethanesulfonylimide) dissolved in a mixed solvent of 1,3-dioxolane (DOL) and dimethyl ethylene glycol (DME). More importantly, lithium polysulfides (LiPSs) exhibit a certain degree of solubility in this electrolyte system, resulting in a significant shuttle effect. On one hand, LiPSs dissolved in the electrolyte lead to rapid loss of active material, shortening battery life; on the other hand, LiPSs shuttled to the negative electrode further corrode lithium metal, causing lithium dendrite growth and even puncturing the separator, leading to short circuits in the battery device. Furthermore, to achieve high specific capacity, an excessive amount of electrolyte (greater than 10 µL mg) is often required. -1 This significantly reduces the energy density of battery devices. Clearly, low electrolyte conditions (less than 5 µL mg) are detrimental. -1 High energy density can only be achieved through this approach; however, slow redox reaction kinetics and low utilization of active materials are the bottlenecks of this strategy.

[0003] In recent years, balancing the dissociation and efficient conversion of LiPSs has become a major focus in this field. Typically, using solvents with high solubility for LiPSs can significantly improve sulfur utilization and accelerate the conversion kinetics. However, these solvents have a severe corrosive effect on lithium metal, leading to instability at the lithium metal anode interface, significantly shortened battery life, and short circuits. Therefore, balancing the compatibility of these solvents with lithium metal and designing and developing novel electrolyte systems that combine rapid sulfur-based conversion kinetics with excellent lithium metal compatibility has become a major challenge in promoting the practical application of high-energy-density lithium-sulfur batteries.

[0004] In conclusion, a new technical solution is urgently needed to address the problems existing in the current technology. Summary of the Invention

[0005] Based on this, the present invention provides a binary solvent electrolyte and its applications. The binary solvent system of the present invention employs a combination of two different solvents: a strong solvating solvent and a weak solvating solvent. The strong solvating characteristic not only provides excellent lithium salt dissociation capability but also promotes efficient lithium-ion migration and transport, thereby enhancing the conversion kinetics of LiPSs. The weak solvating characteristic effectively suppresses the dissolution and shuttle of LiPSs while improving interfacial compatibility with the lithium metal anode. This strategy overcomes the problem of lack of regulation of LiPSs in traditional ether-based electrolytes, achieving the dual goals of efficient LiPSs conversion and suppression of its shuttle, providing a new direction for the design of high-performance lithium-sulfur battery electrolytes. The binary solvent electrolyte provided by the present invention, through the synergistic combination of binary solvents, not only effectively suppresses the shuttle effect of lithium polysulfides and significantly improves their conversion reaction kinetics but also greatly reduces the side reactions of the electrolyte on the lithium metal anode. Lithium-sulfur batteries prepared using this electrolyte system exhibit high specific capacity and long cycle stability. The present invention provides an electrolyte solution with significant application value for the development of high-performance, long-life lithium-sulfur batteries.

[0006] One object of the present invention is to provide a binary solvent electrolyte, wherein the components of the binary solvent electrolyte include the following: a main lithium salt and a binary solvent; The binary solvent is composed of a strong solvating solvent and a weak solvating solvent; The power supply constant of the strongly solvated solvent is greater than that of the weakly solvated solvent; The difference between the power supply constant of the strongly solvated solvent and the weakly solvated solvent is 1-28 kcal / mol. -1 .

[0007] Furthermore, the dielectric constant and some of the power supply constants described in this invention are derived from "Handbook of Chemical and Chemical Engineering Properties: Organic Volume (Revised Edition)", "Static Dielectric Constants of Pure Liquids and Binary Liquid Mixtures", "Chem. Soc. Rev. 2025, 54, 4822", "J. Energy Chem. 2024, 98, 374", and "Electrochim. Acta 1976, 21, 661", etc.

[0008] Furthermore, the power supply constant of the solvent described in this invention is determined using the test method reported in the literature "Nat. Chem. 2014, 6, 1091", that is, using 10 mM sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) dissolved in a solvent. 23 The Na NMR spectrum was converted.

[0009] Furthermore, the difference between the power supply constant of the strongly solvated solvent and the weakly solvated solvent is 1.4 kcal mol. -1 3.6 kcal mol -1 5.6 kcal mol -1 21.7 kcal mol -1 .

[0010] It is worth noting that the terms "strong solvating solvent" and "weak solvating solvent" used in this invention are relative concepts. When two solvents are used together, the solvent with the stronger power supply constant is the strong solvating solvent; conversely, the solvent with the weaker power supply constant is the weaker solvating solvent. However, the difference between the two must be at least ≥1 kcal / mol. -1 .

[0011] Furthermore, the strong solvating solvent is selected from one of dimethyl sulfoxide (DMSO), 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide (CSA), 2-methyltetrahydrofuran (MeTHF), N,N-dimethyl-4,4,4-trifluorobutamide (TFBA) or 1,3-dioxolane (DOL).

[0012] Further, the weak solvating solvent is selected from one of 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide (CSA), ethylene glycol dimethyl ether (DME), 2-methyltetrahydrofuran (MeTHF), N,N-dimethyl-4,4,4-trifluorobutamide (TFBA), 1,3-dioxolane (DOL), or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE).

[0013] The binary solvent is selected from one of the following: strong solvating solvent 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide and weak solvating solvent ethylene glycol dimethyl ether (CSA and DME); strong solvating solvent 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide and weak solvating solvent 2-methyltetrahydrofuran (CSA and MeTHF); strong solvating solvent 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide and weak solvating solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (CSA and TTE); strong solvating solvent N,N-dimethyl-4,4,4-trifluorobutamide and weak solvating solvent 1,3-dioxolane (TFBA and DOL).

[0014] Furthermore, the molar ratio of the strong solvating solvent to the weak solvating solvent is in the range of 1:(0.67-9).

[0015] Furthermore, the binary solvent electrolyte also includes a lithium salt additive; the concentration of the lithium salt additive in the binary solvent electrolyte ranges from 0.01 to 0.5 mol / L. -1 .

[0016] Furthermore, the lithium salt additive is selected from one or more of lithium nitrate (LiNO3), lithium bromide (LiBr), lithium bis(oxalate)borate (LiBOB), or lithium iodide (LiI).

[0017] Further, the main lithium salt is selected from one or more of lithium bis(trifluoromethane)sulfonylimide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonylimide) (LiFSI), or lithium perchlorate (LiClO4); the concentration of the main lithium salt in the binary solvent electrolyte is 0.1-4 mol L. -1 .

[0018] Furthermore, the preparation method of the binary solvent electrolyte includes the following steps: S1. In a glove box filled with inert gas, the strong solvating solvent and the weak solvating solvent are pretreated by molecular sieve adsorption or low-temperature vacuum distillation to make their moisture content less than 10 ppm; then, in a glove box or closed batching system filled with high-purity argon or helium, the two pretreated solvents are mixed to obtain a basic mixed solvent. S2. The main lithium salt, which has been dried in a vacuum oven at 100-120°C for more than 24 hours, is added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte. or S1. In a glove box filled with inert gas, the strong solvating solvent and the weak solvating solvent are pretreated by molecular sieve adsorption or low-temperature vacuum distillation to make their moisture content less than 10 ppm; then, in a glove box or closed batching system filled with high-purity argon or helium, the two pretreated solvents are mixed to obtain a basic mixed solvent. S2. The main lithium salt and lithium salt additive, which have been dried in a vacuum oven at 100-120℃ for more than 24 hours, are added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte.

[0019] Another object of the present invention is to provide the application of the binary solvent electrolyte in lithium-sulfur batteries.

[0020] The present invention has the following beneficial effects: This invention provides a binary solvent electrolyte and its applications. The binary solvent system of this invention employs a combination of two different solvents: a strong solvating solvent and a weak solvating solvent. The strong solvating property not only provides excellent lithium salt dissociation capability but also promotes efficient lithium-ion migration and transport, thereby enhancing the conversion kinetics of LiPSs. The weak solvating property effectively suppresses the dissolution and shuttle of LiPSs while improving interfacial compatibility with the lithium metal anode. This strategy overcomes the lack of regulation of LiPSs in traditional ether-based electrolytes, achieving the dual goals of efficient LiPSs conversion and suppression of its shuttle, providing a new direction for the design of high-performance lithium-sulfur battery electrolytes. The binary solvent electrolyte provided by this invention, through the synergistic combination of binary solvents, not only effectively suppresses the shuttle effect of lithium polysulfides and significantly improves their conversion reaction kinetics but also greatly reduces the side reactions of the electrolyte on the lithium metal anode. Lithium-sulfur batteries prepared using this electrolyte system exhibit high specific capacity and long cycle stability. This invention provides an electrolyte solution with significant application value for the development of high-performance, long-life lithium-sulfur batteries. Attached Figure Description

[0021] Figure 1 The electrochemical performance of the Li||S battery in Application Example 1 is shown.

[0022] Figure 2 The electrochemical performance of the Li||S battery in Application Example 2 is shown.

[0023] Figure 3 The electrochemical performance of the Li||S battery in Application Example 3 is shown.

[0024] Figure 4 The electrochemical performance of the Li||S battery in Application Example 4 is shown.

[0025] Figure 5 The electrochemical performance of Li||S batteries in comparative application examples is shown. Detailed Implementation

[0026] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0027] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0028] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0029] This invention focuses on three aspects: electrolyte formulation screening, electrode preparation process optimization, and battery electrochemical performance evaluation. Specific implementation methods will detail the composition and ratio of each binary electrolyte and the coating and drying conditions of the positive electrode slurry (such as active material loading, drying temperature, and time). By comparing and analyzing key performance indicators such as coulombic efficiency, first-cycle discharge capacity, and capacity retention under different electrolyte systems, the effectiveness and superiority of the electrolyte design strategy proposed in this invention are verified.

[0030] All operations involving the preparation, assembly, and testing of air-sensitive components are performed in a glove box or closed system protected by inert gas.

[0031] Table 1 lists the Gutmann donor number (DN) and dielectric constant (ε) of some of the available solvents. r ).

[0032] Table 1. Solvent's dielectric constant (DN) and dielectric constant (ε) r ) The power supply constant of the aforementioned solvents was determined using the test method described in the previously reported literature "Nat. Chem. 2014, 6, 1091", which involved dissolving 10 mM NaTFSI in a solvent. 23 The Na NMR spectrum was converted.

[0033] The binary solvent system of this invention employs a combination of two different solvents: a strong solvating solvent and a weak solvating solvent. The strong solvating property provides excellent lithium salt dissociation capability and promotes efficient lithium-ion migration and transport, thereby improving LiPSs conversion kinetics. The weak solvating property suppresses LiPSs dissolution and shuttle, and improves interfacial compatibility with the lithium metal anode. The binary solvent electrolyte obtained by using the above solvent combination, when applied to lithium-sulfur batteries, exhibits excellent charge-discharge performance.

[0034] Guided by the above design principles, this invention provides a series of binary solvent electrolytes. The following binary solvent electrolyte formulations were prepared and evaluated: CSA / DME, CSA / MeTHF, CSA / TTE, and TFBA / DOL.

[0035] This invention starts with electrolyte design, designing different binary solvent electrolytes to achieve rapid conversion of LiPSs while improving the stability of lithium metal anodes, providing an effective electrolyte solution for promoting the practical application of lithium-sulfur batteries.

[0036] The present invention uses the following raw materials: Kojic Black: Battery grade, purchased from Lion Corporation, Japan; Carbon nanotubes: purchased from Carbon Energy Technology Co., Ltd. Adhesive LA133: Purchased from Shenzhen Kejing Co., Ltd.; Carbon-coated aluminum foil: purchased from Shenzhen Kejing Co., Ltd.; Celgard2500: Purchased from Shenzhen Kejing Co., Ltd.

[0037] Example 1 A binary solvent electrolyte, wherein the binary solvent electrolyte is composed of the following components: a main lithium salt LiTFSI, a lithium salt additive LiNO3, a strong solvating solvent CSA, and a weak solvating solvent DME; The molar ratio of LiTFSI, LiNO3, CSA, and DME is 1:0.2:4:6. The preparation method of the binary solvent electrolyte includes the following steps: S1. In a glove box filled with nitrogen, the strong solvating solvent and the weak solvating solvent are respectively subjected to molecular sieve adsorption pretreatment to reduce their moisture content to below 10 ppm. Subsequently, in a glove box filled with high-purity argon, the two pretreated solvents are mixed to obtain a basic mixed solvent. S2. LiTFSI and LiNO3, which have been dried in a vacuum oven at 110°C for 24 h, are added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte.

[0038] Example 2 A binary solvent electrolyte, wherein the binary solvent electrolyte is composed of the following components: a main lithium salt LiTFSI, a lithium salt additive LiNO3, a strong solvating solvent CSA, and a weak solvating solvent MeTHF; The molar ratio of LiTFSI, LiNO3, CSA, and MeTHF is 1:0.2:4:6. The preparation method of the binary solvent electrolyte includes the following steps: S1. In a glove box filled with nitrogen, the strong solvating solvent and the weak solvating solvent are respectively subjected to molecular sieve adsorption pretreatment to reduce their moisture content to below 10 ppm. Subsequently, in a glove box filled with high-purity argon, the two pretreated solvents are mixed to obtain a basic mixed solvent. S2. LiTFSI and LiNO3, which have been dried in a vacuum oven at 110°C for 24 h, are added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte.

[0039] Example 3 A binary solvent electrolyte, wherein the binary solvent electrolyte is composed of the following components: a main lithium salt LiTFSI, a strong solvating solvent CSA, and a weak solvating solvent TTE; The molar ratio of LiTFSI, CSA, and TTE is 1:4:6. The preparation method of the binary solvent electrolyte includes the following steps: S1. In a glove box filled with nitrogen, the strong solvating solvent and the weak solvating solvent are respectively subjected to molecular sieve adsorption pretreatment to reduce their moisture content to below 10 ppm. Subsequently, in a glove box filled with high-purity argon, the two pretreated solvents are mixed to obtain a basic mixed solvent. S2. LiTFSI, which has been dried in a vacuum oven at 110°C for 24 h, is added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte.

[0040] Example 4 A binary solvent electrolyte, wherein the binary solvent electrolyte is composed of the following components: a main lithium salt LiTFSI, a strong solvating solvent TFBA, and a weak solvating solvent DOL; The molar ratio of LiTFSI, TFBA, and DOL is 1:4:6. The preparation method of the binary solvent electrolyte includes the following steps: S1. In a glove box filled with nitrogen, the strong solvating solvent and the weak solvating solvent are respectively subjected to molecular sieve adsorption pretreatment to reduce their moisture content to below 10 ppm. Subsequently, in a glove box filled with high-purity argon, the two pretreated solvents are mixed to obtain a basic mixed solvent. S2. LiTFSI, which has been dried in a vacuum oven at 110°C for 24 h, is added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte.

[0041] Comparative Example A lithium-sulfur battery electrolyte is composed of the following components: LiTFSI, LiNO3, DME and DOL; The molar ratio of LiTFSI, LiNO3, DME, and DOL is 1:0.2:4:6. The preparation method of the lithium-sulfur battery electrolyte in this comparative example includes the following steps: S1. In a glove box filled with nitrogen, DME and DOL were pretreated by molecular sieve adsorption to reduce their moisture content to below 10 ppm. Subsequently, in a glove box filled with high-purity argon, the two pretreated solvents were mixed to obtain a basic mixed solvent. S2. LiTFSI and LiNO3, which have been dried in a vacuum oven at 110°C for 24 h, are added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte.

[0042] Application Examples 1-4 A lithium-sulfur battery was prepared using the binary solvent electrolytes of Examples 1-4, respectively. Its preparation process includes the following steps: Sulfur powder and Ketjen black were ground and mixed at a mass ratio of 7:3 to obtain a sulfur-carbon composite material (S@KB). Subsequently, S@KB, carbon nanotubes, and binder LA133 were mixed at a mass ratio of 77.5:12.5:10 and stirred until homogeneous to obtain a positive electrode slurry. This slurry was uniformly coated onto a carbon-coated aluminum foil to serve as the sulfur-carbon composite positive electrode. Finally, using lithium metal as the negative electrode, Celgard 2500 as the separator, and the sulfur-carbon composite material as the positive electrode, a lithium-sulfur battery was assembled using the binary solvent electrolyte of the example.

[0043] Comparative application examples The difference between this comparative application example and the application example is that the lithium-sulfur battery electrolyte used in this example is used to assemble the lithium-sulfur battery, while the other steps and quantities are the same as in the application example.

[0044] Test case Electrochemical performance tests were conducted on lithium-sulfur batteries used in Application Examples 1-4 and the comparative application examples.

[0045] Test method: The assembled battery was subjected to charge-discharge cycle test on a battery charge-discharge tester with a working voltage of 1.7-2.8 V and a charge-discharge rate of 0.2 C. The discharge capacity of the first cycle and the discharge capacity of the 40th cycle were tested.

[0046] The test results are shown in Table 2 and Figure 1-5 As shown.

[0047] Table 2. Discharge capacity test results of Application Examples 1-4 and Comparative Application Examples (first and 40th cycles). Figure 1 The electrochemical performance of the Li||S battery in Application Example 1 is shown.

[0048] Figure 2 The electrochemical performance of the Li||S battery in Application Example 2 is shown.

[0049] Figure 3 The electrochemical performance of the Li||S battery in Application Example 3 is shown.

[0050] Figure 4 The electrochemical performance of the Li||S battery in Application Example 4 is shown.

[0051] Figure 5 The electrochemical performance of Li||S batteries in comparative application examples is shown.

[0052] The test results show that this invention, starting with the design of the electrolyte system, effectively addresses the key challenges of lithium-sulfur batteries in practical applications: on the one hand, it improves the conversion reaction kinetics of the sulfur cathode, and on the other hand, it enhances the interfacial compatibility with the lithium anode, thereby simultaneously achieving a significant improvement in battery energy density and cycle stability.

[0053] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0054] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A binary solvent electrolyte, characterized in that, The binary solvent electrolyte comprises the following components: main lithium salt and binary solvent; The binary solvent is composed of a strong solvating solvent and a weak solvating solvent; The power supply constant of the strongly solvated solvent is greater than that of the weakly solvated solvent; The difference between the donor constant of the strongly solvating solvent and the donor constant of the weakly solvating solvent is 1-28 kcal mol -1 .

2. The binary solvent electrolyte according to claim 1, wherein The difference between the power supply constant of the strongly solvated solvent and the weakly solvated solvent is 1.4 kcal / mol. -1 3.6 kcal mol -1 5.6 kcal mol -1 Or 21.7 kcal mol -1 .

3. The binary solvent electrolyte of claim 1, wherein The strong solvating solvent is selected from one of dimethyl sulfoxide, 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide, 2-methyltetrahydrofuran, N,N-dimethyl-4,4,4-trifluorobutamide, or 1,3-dioxolane.

4. The binary solvent electrolyte of claim 1, wherein The weak solvating solvent is selected from one of 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, N,N-dimethyl-4,4,4-trifluorobutamide, 1,3-dioxolane, or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

5. The binary solvent electrolyte of claim 1, wherein The binary solvent is selected from one of the following: strong solvating solvent 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide and weak solvating solvent ethylene glycol dimethyl ether; strong solvating solvent 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide and weak solvating solvent 2-methyltetrahydrofuran; strong solvating solvent 2,5-dimethyl-1,2,5-thiadiazolidine-1-oxide and weak solvating solvent 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; strong solvating solvent N,N-dimethyl-4,4,4-trifluorobutamide and weak solvating solvent 1,3-dioxolane.

6. The binary solvent electrolyte of claim 1, wherein The molar ratio of the strong solvating solvent to the weak solvating solvent is in the range of 1:(0.67-9).

7. The binary solvent electrolyte of claim 1, wherein The components of the binary solvent electrolyte further include a lithium salt additive; the concentration of the lithium salt additive in the binary solvent electrolyte ranges from 0.01 to 0.5 mol / L -1 .

8. The binary solvent electrolyte of claim 1, wherein, The main lithium salt is selected from one or more of lithium bis(trifluoromethane)sulfonylimide, lithium hexafluorophosphate, lithium bis(fluorosulfonylimide), or lithium perchlorate; the concentration of the main lithium salt in the binary solvent electrolyte is 0.1-4 mol / L. -1 .

9. A method for preparing the binary solvent electrolyte according to any one of claims 1-8, characterized in that, Includes the following steps: S1. In a glove box filled with inert gas, the strong solvating solvent and the weak solvating solvent are pretreated by molecular sieve adsorption or low-temperature vacuum distillation to make their moisture content less than 10 ppm; then, in a glove box or closed batching system filled with high-purity argon or helium, the two pretreated solvents are mixed to obtain a basic mixed solvent. S2. The main lithium salt, which has been dried in a vacuum oven at 100-120°C for more than 24 hours, is added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte. or S1. In a glove box filled with inert gas, the strong solvating solvent and the weak solvating solvent are pretreated by molecular sieve adsorption or low-temperature vacuum distillation to make their moisture content less than 10 ppm; then, in a glove box or closed batching system filled with high-purity argon or helium, the two pretreated solvents are mixed to obtain a basic mixed solvent. S2. The main lithium salt and lithium salt additive, which have been dried in a vacuum oven at 100-120℃ for more than 24 hours, are added to the basic mixed solvent to dissolve the lithium salt and form a stable electrolyte, thus obtaining a binary solvent electrolyte.

10. The application of the binary solvent electrolyte according to any one of claims 1-8 in lithium-sulfur batteries.

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