An electrolyte and lithium metal battery

Abstract

Existing lithium metal batteries use ether-based electrolytes and SPAN cathodes, which makes it difficult to achieve reversible solid-solid conversion of the SPAN cathode, resulting in low battery life over a wide operating temperature range. This application provides an electrolyte and a lithium metal battery. The electrolyte includes an organic solvent and a diluent, wherein the organic solvent is trimethoxymethylsilane and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. In the electrolyte, the volume ratio of the organic solvent to the diluent is (9~1):(1~9). The electrolyte provided by this application can effectively suppress the dissolution of lithium polysulfides, ensuring that only solid-solid conversion occurs at the SPAN cathode, and can be used in a wide temperature range of -20℃, 30℃, and 60℃. It maintains the stability of the anion-rich solvation structure over a wide temperature range, thus extending the battery's wide-temperature cycle life.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more particularly to an electrolyte and a lithium metal battery. Background Technology

[0002] Lithium-sulfur batteries possess advantages such as high theoretical energy density, low cost, and environmental friendliness, making them a promising next-generation energy storage system. However, the electrochemical performance of lithium-sulfur batteries is severely affected by the significant volume changes of the sulfur cathode and lithium metal anode, the shuttle effect of lithium polysulfides (LiPSs), and the rapid and irreversible consumption of active materials and electrolytes, leading to problems such as capacity decay and short-circuit risks. Among these, sulfurized polyacrylonitrile (SPAN) has become a highly promising cathode material for lithium-sulfur batteries due to its high sulfur utilization, good cycle stability, and absence of the shuttle effect.

[0003] While SPAN cathodes achieve good cycle stability in carbonate-based electrolytes, interfacial side reactions at the lithium anode and lithium dendrite growth are key factors limiting the long-cycle performance of Li-SPAN batteries. Compared to carbonate-based electrolytes, ether-based electrolytes offer better chemical compatibility with lithium metal and enable highly reversible lithium deposition / stripping. However, when SPAN cathodes are charged and discharged in conventional ether-based electrolytes, the formation of soluble LiPSs and shuttle effects occur, hindering reversible solid-solid conversion of the SPAN cathode. Furthermore, the operating temperature range of Li-SPAN batteries is limited by the liquidus temperature range of ether-based electrolytes, resulting in low battery life over a wide operating temperature range. Summary of the Invention

[0004] To address the problems of existing lithium metal batteries using ether-based electrolytes and SPAN cathodes, which make it difficult to achieve reversible solid-solid conversion of the SPAN cathode and result in low battery life over a wide operating temperature range, this application provides an electrolyte and a lithium metal battery.

[0005] On one hand, the present invention provides an electrolyte comprising an organic solvent and a diluent, wherein the organic solvent is trimethoxymethylsilane and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and in the electrolyte, the volume ratio of the organic solvent to the diluent is (9~1):(1~9).

[0006] Preferably, in the electrolyte, the volume ratio of the organic solvent to the diluent is (7~3):(3~7).

[0007] Preferably, in the electrolyte, the volume ratio of the organic solvent to the diluent is (4~6):(6~4).

[0008] Preferably, the electrolyte further includes a lithium salt, wherein the molar concentration of the lithium salt is 0.5~1.5 mol / L.

[0009] Preferably, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide.

[0010] Preferably, in the electrolyte, the volume ratio of the organic solvent to the diluent is (4~6):(6~4); and the molar concentration of the lithium salt is 0.8~1.2 mol / L.

[0011] Preferably, the Raman solvation peak position of the electrolyte at -20~60℃ is 740.1~744.0 cm⁻¹. -1 .

[0012] On the other hand, this application provides a lithium metal battery, including the electrolyte described above.

[0013] Preferably, the lithium metal battery includes a positive electrode, the positive electrode includes a positive electrode active material, and the positive electrode active material is selected from sulfurized polyacrylonitrile.

[0014] Preferably, the lithium metal battery includes a lithium anode, which comprises lithium metal or a lithium alloy.

[0015] The electrolyte provided in this application, when applied in a Li-SPAN battery system, effectively suppresses the dissolution of lithium polysulfides, ensuring that the SPAN cathode only undergoes a solid-solid conversion reaction and not a solid-liquid conversion reaction. Furthermore, it can be used within a wide temperature range of -20℃, 30℃, and 60℃, maintaining stability of the anion-rich solvation structure over this wide temperature range, thus extending the battery's wide-temperature cycle life. Simultaneously, it achieves high reversibility of lithium deposition / stripping on the negative electrode side, enabling uniform lithium deposition and reducing lithium dendrite formation.

[0016] Instruction manual illustrations Figure 1 Raman graphs of the electrolyte in Example 1 at -20°C, 30°C, and 60°C; Figure 2 Raman spectra of the electrolyte in Comparative Example 1 at -20℃, 30℃, and 60℃; Figure 3 Raman spectroscopy of the electrolyte in Comparative Example 2 at -20℃, 30℃, and 60℃; Figure 4 The lithium NMR spectra of the electrolytes in Example 1, Comparative Examples 1 and 2 at -20°C, 30°C and 60°C are shown. Figure 5 The diagram shows the ion transport activation energy analysis of the batteries in Example 1, Comparative Examples 1 and 2. Figure 6 The lithium metal deposition morphology of the negative electrode of the batteries in Example 1, Comparative Examples 1 and 2 after cycling at -20°C for 20 cycles; Figure 7 The lithium metal deposition morphology of the negative electrode of the batteries in Example 1, Comparative Examples 1 and 2 after cycling at 30°C for 20 cycles is shown. Figure 8 The lithium metal deposition morphology of the negative electrode after cycling at 60°C for 20 cycles in Examples 1, 1, and 2 is shown. Figure 9 The constant current charge-discharge curves of batteries in Example 1, Comparative Examples 1 and 2 at -20°C are shown. Figure 10 The constant current charge-discharge curves of batteries in Example 1, Comparative Examples 1 and 2 at 30°C are shown. Figure 11 The constant current charge-discharge curves of batteries in Example 1, Comparative Examples 1 and 2 at 60°C are shown. Figure 12 The cyclic voltammetry curves of batteries in Example 1, Comparative Examples 1 and 2 at -20°C, 30°C, and 60°C are shown. Figure 13 This is a comparison graph showing the change in specific capacity of batteries in Example 1, Comparative Examples 1 and 2 during cycle life testing at -20°C. Figure 14 This is a comparison graph showing the change in specific capacity of batteries in Example 1, Comparative Examples 1 and 2 during cycle life testing at 30°C. Figure 15 This is a comparison graph showing the change in specific capacity of batteries in Example 1, Comparative Example 1, and 2 during cycle life testing at 60°C. Figure 16 The electrostatic potential diagrams are for DME, MTOS, and TTE solvent molecules. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] To illustrate the technical solution of the present invention, specific embodiments are described below.

[0019] In one embodiment of the present invention, an electrolyte comprises an organic solvent and a diluent, wherein the organic solvent is trimethoxymethylsilane and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; in the electrolyte, the volume ratio of the organic solvent to the diluent is (9~1):(1~9).

[0020] The organic solvent is trimethoxymethylsilane. The Si-O conjugation in trimethoxymethylsilane reduces the electron-donating ability of oxygen, thus lowering the Li... + - Solvent interaction promotes the formation of anion-rich solvation structures and improves desolvation kinetics; at the same time, organic solvents have low solubility for lithium polysulfides and good stability to lithium metal, which can suppress polysulfide shuttle to some extent.

[0021] In the electrolyte, the volume ratio of organic solvent to diluent is (9~1):(1~9), and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. In synergy with the organic solvent, the electrolyte improves the reaction of Li... + The interaction force is the weakest, and the solvation structures are mainly CIP and AGG; within a wide temperature range of -20℃, 30℃, and 60℃, the anion-rich solvation structures remain stable. At different temperatures, the electrolyte's effect on Li... + The effect of this force is the weakest, and as the temperature increases, the effect on Li... + The interaction force tends to weaken, resulting in a low desolvation energy.

[0022] In specific embodiments, the volume ratio of organic solvent to diluent can be 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9, or within any range of the above.

[0023] If the volume ratio of organic solvent to diluent is higher than (9~1):(1~9), the electrolyte contains too much organic solvent, which enhances its ability to dissolve lithium polysulfides, leading to a solid-liquid conversion reaction, the formation of soluble LiPSs, and shuttle effect problems, thus reducing the battery cycle life. If the volume ratio of organic solvent to diluent is lower than (9~1):(1~9), the electrolyte contains too much diluent, resulting in insufficient lithium salt dissolution and low conductivity.

[0024] The electrolyte provided in this application, when applied in a Li-SPAN battery system, effectively suppresses the dissolution of lithium polysulfides, ensuring that the SPAN cathode only undergoes a solid-solid conversion reaction and not a solid-liquid conversion reaction. Furthermore, it can be used within a wide temperature range of -20℃, 30℃, and 60℃, maintaining stability of the anion-rich solvation structure over this wide temperature range, thus extending the battery's wide-temperature cycle life. Simultaneously, it achieves high reversibility of lithium deposition / stripping on the negative electrode side, enabling uniform lithium deposition and reducing lithium dendrite formation.

[0025] The electrolyte provided in this application contains organic solvents and diluents that have weak solubility for lithium polysulfides, a wide liquid phase temperature range, and can regulate the solvation structure of the electrolyte to balance the ionic conductivity of the electrolyte and the reversible solid-solid conversion of the SPAN cathode, effectively improving the wide temperature performance of Li-SPAN batteries and increasing the cycle life of the batteries in a wide temperature range of -20℃, 30℃, and 60℃.

[0026] In some preferred embodiments, the volume ratio of the organic solvent to the diluent in the electrolyte is (7~3):(3~7).

[0027] When the volume ratio of organic solvent to dilution is within the above range, the electrolyte exhibits low solubility for lithium polysulfides, effectively suppressing their dissolution and ensuring that the SPAN cathode only undergoes a solid-solid conversion reaction, without a solid-liquid conversion reaction. It also possesses the characteristic of maintaining a stable anion-rich solvation structure, while Li... + - The interaction between the solvent and the desolvation energy is relatively weak, which effectively improves the wide temperature cycle life of the battery.

[0028] More preferably, in the electrolyte, the volume ratio of the organic solvent to the diluent is (4~6):(6~4).

[0029] Within the volume ratio of organic solvent to diluent within the above range, the synergistic effect of the organic solvent and diluent is stronger, Li + The weaker interaction with the solvent and the lower desolvation energy reduce the formation of lithium dendrites, resulting in a longer cycle life of the battery within a wide temperature range of -20℃, 30℃, and 60℃.

[0030] More preferably, in the electrolyte, the volume ratio of the organic solvent to the diluent is 5:5.

[0031] In some embodiments, the electrolyte further includes a lithium salt, wherein the molar concentration of the lithium salt is 0.5 to 1.5 mol / L.

[0032] Specifically, when the molar concentration of lithium salt in the electrolyte is within the above range, it can balance the ionic conductivity of the electrolyte, regulate the solvation structure, stabilize the negative electrode interface, and inhibit the growth of lithium dendrites.

[0033] In specific embodiments, the molar concentration of the lithium salt can be 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, etc., as long as the molar concentration of the lithium salt is in the range of 0.5 to 1.5 mol / L.

[0034] In some preferred embodiments, the molar concentration of the lithium salt is 0.8~1.2 mol / L.

[0035] When the molar concentration of lithium salt is in the range of 0.8 to 1.2 mol / L, the electrolyte has high ionic conductivity and moderate viscosity, which is beneficial to improving the wide temperature cycle life of the battery.

[0036] More preferably, the molar concentration of the lithium salt is 1.0 mol / L.

[0037] When the molar concentration of lithium salt is within the above-mentioned preferred range, the electrolyte has high conductivity, which is beneficial for improving the cycle life of the battery over a wide temperature range.

[0038] In some embodiments, the lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide.

[0039] The lithium salts are selected from the above types and provide lithium ions and anions in the electrolyte to synergistically improve battery cycle performance.

[0040] In some embodiments, the volume ratio of the organic solvent to the diluent in the electrolyte is (4~6):(6~4); the molar concentration of the lithium salt is 0.5~1.5 mol / L.

[0041] Specifically, in the electrolyte, it is preferable to keep the volume ratio of organic solvent and diluent fixed, and adjust the molar concentration of lithium salt within the above range. As the lithium salt concentration increases, there will be more solvation structures rich in anions in the electrolyte, which is beneficial to extending the battery's wide temperature cycle life.

[0042] In some preferred embodiments, the volume ratio of the organic solvent to the diluent is (4~6):(6~4); and the molar concentration of the lithium salt is 0.8~1.2 mol / L.

[0043] In electrolytes, when there are more anionic solvated structures, the electrolyte viscosity will be higher, which is not conducive to low-temperature cycling of the battery. The preferred lithium salt molar concentration is in the range of 0.8~1.2 mol / L, which provides moderate electrolyte viscosity and high conductivity, thus improving the battery's wide-temperature cycle life.

[0044] In some embodiments, the Raman solvation peak position of the electrolyte at -20 to 60°C is 740.1 to 744.0 cm⁻¹. -1 .

[0045] The electrolyte provided in this application, compared to other types of electrolytes, exhibits Raman spectra with solvation peaks located between 740.1 and 744.0 cm⁻¹ when subjected to Raman spectroscopy at -20°C, 30°C, and 60°C. -1Within the specified range, the peak position remains unchanged, while the peak positions of other electrolytes change with temperature. This indicates that the electrolyte provided in this application has a relatively stable anion-rich solvation structure, and the interaction between lithium ions and solvent is weak, which is conducive to desolvation. This can effectively improve the lithium deposition problem at the negative electrode interface, reduce the formation of lithium dendrites at the negative electrode interface, and improve the cycle life of the battery.

[0046] Secondly, this application provides a lithium metal battery, including the electrolyte described above.

[0047] The lithium metal battery provided in this application, using the above-mentioned electrolyte, can effectively suppress the dissolution of lithium polysulfides, so that the SPAN positive electrode only undergoes a "solid-solid" conversion reaction and does not undergo a "solid-liquid" conversion reaction. Furthermore, it can reduce the formation of lithium dendrites on the negative electrode side within a wide temperature range of -20℃, 30℃, and 60℃, thereby improving the wide temperature cycle life of the battery.

[0048] In some embodiments, the lithium metal battery includes a positive electrode, the positive electrode including a positive electrode active material selected from sulfurized polyacrylonitrile.

[0049] The electrolyte provided in this application is suitable for lithium metal battery systems using sulfurized polyacrylonitrile as the positive electrode active material. The resulting battery has a high cycle life over a wide temperature range of -20℃, 30℃, and 60℃. When other types of positive electrode active materials are used, the cycle life of the battery is poor over a wide temperature range.

[0050] The positive electrode includes a positive electrode active material layer, which also includes a conductive agent and a binder. This application does not impose specific restrictions on the types of conductive agents and binders. For example, the conductive agent may be one or more of graphite, acetylene black, carbon black, Ketjen black, carbon nanotubes, or graphite; the binder may be one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl butyral (PVB), ethylene-vinyl acetate copolymer (EVA), and polyvinyl alcohol (PVA).

[0051] The positive current collector can be made of metal foil or metal plate, such as aluminum foil.

[0052] In some embodiments, the lithium metal battery includes a lithium anode, which comprises lithium metal or a lithium alloy.

[0053] The lithium anode selected from the above types, together with the positive electrode active material selected from the above, is a sulfurized polyacrylonitrile. The resulting lithium metal battery has a high cycle life in a wide temperature range of -20℃, 30℃, and 60℃.

[0054] The lithium anode may also include a negative electrode current collector and a lithium metal sheet or lithium alloy sheet disposed on the surface of the negative electrode current collector. The negative electrode current collector may be a metal foil or a metal plate, such as copper foil.

[0055] Lithium metal batteries also include a separator, which is positioned between the positive and negative electrodes. Existing separators can be used.

[0056] The present application will be further illustrated by the following examples.

[0057] Example 1 Preparation of S1 electrolyte: The organic solvent is trimethoxymethylsilane (MTOS), and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), with a volume ratio of MTOS:TTE of 5:5; the lithium salt is lithium bisfluorosulfonylimide (LiFSI). The organic solvent, diluent, and lithium salt are mixed thoroughly to obtain the electrolyte, in which the molar concentration of the lithium salt is 1.0 mol / L.

[0058] S2: Preparation of the positive electrode: The positive electrode active material is vulcanized polyacrylonitrile (SPAN), the conductive agent is carbon nanotubes (CNT), and the binder is polyacrylic acid (PAA).

[0059] SPAN, CNT, and PAA are mixed with water and ethanol in a mass ratio of 93:2:5 to obtain a positive electrode slurry. The positive electrode slurry is coated on the surface of aluminum foil and then rolled and die-cut to obtain a positive electrode sheet.

[0060] The negative electrode is a lithium metal negative electrode.

[0061] A lithium metal battery is obtained by combining an electrolyte, a positive electrode, and a negative electrode.

[0062] Examples 2-9 and Comparative Examples 3-4 Examples 2-9 and Comparative Examples 3-4 are largely the same as those in Example 1, except that the volume ratio of MTOS to TTE is different, as detailed in Table 1. The rest is the same as in Example 1.

[0063] Examples 10-21 Examples 10-21 are largely the same as Example 1, except that the lithium salt concentrations in Examples 10-21 are different, as detailed in Table 2. The rest are the same as in Example 1.

[0064] Example 22 Most of the steps in Example 22 are the same as those in Example 1, except that the type of positive electrode active material used is different; in Example 22, the positive electrode active material is NCM811. The rest is the same as in Example 1.

[0065] Comparative Example 1 This comparative example is largely the same as Example 1, except that in the electrolyte preparation step, the solvent is dimethyl glycol ether (DME) and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE). The rest is the same as in Example 1. See Table 1 for details.

[0066] Comparative Example 2 This comparative example is largely the same as Example 1, except that in the electrolyte preparation step, the solvents are ethylene glycol dimethyl ether (DME) and 1,3-dioxolane (DOL) in a volume ratio of 5:5, and no diluent is used. The rest is the same as in Example 1. See Table 1 for details.

[0067] Performance testing The lithium metal batteries prepared in the above embodiments and comparative examples were subjected to the following performance tests.

[0068] 1) Cycle life at -20℃, 30℃, and 60℃ At -20℃, with a charging cutoff voltage of 3.0V and a discharging cutoff voltage of 1.0V, a 0.2C / 0.2C charge-discharge cycle test was performed on the lithium metal battery. The capacity retention rate was 80%, and the number of cycles was recorded.

[0069] Similarly, the above cycle test was performed at 30℃ and 60℃, the difference being that the charging and discharging currents were different, with the charging and discharging currents being 0.5C / 0.5C, and the number of cycles was recorded respectively.

[0070] The test results are shown in Tables 1 and 2.

[0071] 2) The electrolytes obtained in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to Raman spectroscopy tests at -20°C, 30°C, and 60°C. The test results are shown in [Figure number missing]. Figure 1-3 .

[0072] 3) Temperature-dependent NMR spectroscopy was performed on the electrolytes in Example 1, Comparative Example 1, and Comparative Example 2 at -20°C, 30°C, and 60°C. The obtained temperature-dependent lithium NMR spectra are shown below. Figure 4 .

[0073] 4) Variable-temperature electrochemical impedance spectroscopy (VIS) The batteries from Example 1, Comparative Example 1, and Comparative Example 2 were subjected to EIS tests at different temperatures, and ion transport activation energy analysis charts were obtained. Specific test results are shown below. Figure 5 .

[0074] 5) The batteries prepared in Examples 1, 1, and 2 were subjected to the above performance test step 1) for 20 cycles at -20°C, 30°C, and 60°C. The lithium metal deposition morphology on the lithium metal anode surface was then measured using SEM. Specific test results are shown in [link to specific test results]. Figure 6-8 .

[0075] 6) The batteries prepared in Example 1, Comparative Example 1, and Comparative Example 2 were subjected to lithium-copper Aurbach tests at -20℃, 30℃, and 60℃ to test the stability of the three electrolytes on lithium metal at different temperatures, and constant current charge-discharge curves were obtained. Specific test results are shown in [link to specific test results]. Figure 8-11 .

[0076] 7) Cyclic voltammetry tests were conducted on the batteries prepared in Example 1, Comparative Example 1, and Comparative Example 2 at -20℃, 30℃, and 60℃. Specific test results are shown in [link to test results]. Figure 12 .

[0077] 8) During the cyclic testing of the batteries in Examples 1, 1, and 2 at -20°C, 30°C, and 60°C, the specific changes in specific capacity are shown in the figure. Figure 13-15 .

[0078] Table 1 As shown in Table 1, compared with Comparative Examples 1 and 2, the organic solvent in Comparative Example 1 was dimethyl ethylene glycol ether (DME), resulting in a lower battery cycle life at -20°C, 30°C, and 60°C. Comparative Example 2 used no diluent, and the organic solvent was dimethyl ethylene glycol ether (DME). Compared with 1,3-dioxolane (DOL), the battery cycle life is also low under conditions of -20℃, 30℃, and 60℃. In comparison with Examples 1-9 and Comparative Examples 3-4, the volume ratio of organic solvent to diluent is not in the range of (9~1):(1~9), and the battery cycle life is low over a wide temperature range. This indicates that in the electrolyte, the organic solvent is trimethoxymethylsilane and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. When the volume ratio of organic solvent to diluent in the electrolyte is in the range of (9~1):(1~9), it can be applied in the Li-SPAN battery system to effectively suppress the dissolution of lithium polysulfides, so that the SPAN cathode only undergoes a "solid-solid" conversion reaction and does not undergo a "solid-liquid" conversion reaction. It can also be applied in a wide temperature range of -20℃, 30℃, and 60℃, thus extending the wide temperature cycle life of the battery. Comparing Example 1 and Example 22, the positive electrode material used in Example 22 is of a different type, such as the ternary material NCM811. The battery has a low cycle life in a wide temperature range of -20℃, 30℃, and 60℃. This indicates that the electrolyte provided in this application is suitable for lithium metal batteries with positive electrode active materials selected from sulfurized polyacrylonitrile. The corresponding organic solvent has low solubility for lithium polysulfides, and the resulting battery has a high cycle life in a wide temperature range.

[0079] Comparative examples 1-9 show that when the volume ratio of organic solvent to diluent is in the range of (7~3):(3~7), the battery cycle life is slightly higher under conditions of -20℃, 30℃, and 60℃. More preferably, when the volume ratio of organic solvent to diluent is in the range of (4~6):(6~4), the battery cycle life is relatively high. More preferably, when the volume ratio of organic solvent to diluent is 5:5, the battery cycle life is the highest.

[0080] Table 2 Table 2 shows that, comparing Examples 1, 10-19, and 20-21, batteries with lithium salt molar concentrations in the electrolyte outside the range of 0.5~1.5 mol / L have lower cycle lives at -20℃, 30℃, and 60℃. Conversely, batteries with lithium salt molar concentrations in the electrolyte within the range of 0.5~1.5 mol / L have higher cycle lives at -20℃, 30℃, and 60℃. A comparison of Examples 1 and 10-19 indicates that batteries with lithium salt molar concentrations in the electrolyte within the range of 0.8~1.2 mol / L have higher cycle lives at -20℃, 30℃, and 60℃.

[0081] pass Figure 1-3 The comparison shows that the electrolyte obtained in Example 1, under conditions of -20℃, 30℃, and 60℃, has a solvation structure mainly composed of CIP and AGG, and the solvation structure remains unchanged. In contrast, the electrolytes in Comparative Examples 1 and 2 change with temperature, indicating that the electrolyte provided in this application has the characteristic of maintaining a stable solvation structure rich in anions.

[0082] pass Figure 4 It can be seen that, under conditions of -20℃, 30℃, and 60℃, the electrolyte of Example 1 has a positive effect on Li + The effect of temperature on Li is the weakest; as temperature increases, the effect of temperature on Li... + The weakening of the force indicates that the electrolyte of this application can reduce the desolvation energy.

[0083] Figure 5 These are ion transport activation energy analysis graphs for Example 1 and Comparative Examples 1 and 2 at different temperatures. Figure 8 It can be seen that the lithium-ion transport activation energy in Example 1 is low and the energy barrier overcome is low, indicating that the electrolyte provided in this application can improve the lithium-ion transport dynamics and improve the cycle life of the battery under conditions of -20℃, 30℃ and 60℃.

[0084] Figure 6-8 The lithium metal deposition morphology of Example 1, Comparative Example 1, and Comparative Example 2 was tested after 20 cycles at -20℃, 30℃, and 60℃. Figure 6-8 It can be seen that the lithium metal deposition thickness in Example 1 is thinner when compared with d, e, and f. Meanwhile, the lithium layer in the electron microscope images a, b, and c does not have obvious dendrites or pores. This indicates that in the lithium metal battery of Example 1, lithium metal can be uniformly deposited on the surface of the lithium anode during battery cycling. This shows that the electrolyte provided in this application can enable uniform lithium metal deposition, suppress lithium dendrite formation, and improve battery cycle life.

[0085] pass Figure 9-11 The comparison shows that the coulombic efficiency of Example 1 is 99.5% at room temperature (30℃), 98.6% at low temperature (-20℃), and 99.4% at high temperature (60℃). At all three different temperatures, Example 1 has the highest coulombic efficiency. The higher the coulombic efficiency, the stronger the stability to lithium metal. This indicates that the electrolyte of Example 1 has the best stability to lithium metal.

[0086] pass Figure 12 The comparison shows that Comparative Examples 1 and 2 exhibited excess redox peaks at 30℃ and 60℃, corresponding to the solid-liquid conversion peaks in lithium-sulfur batteries, which can lead to a shuttle effect and are detrimental to cycle life. Example 1 showed no excess peaks.

[0087] pass Figure 13-15 The comparison shows that the battery obtained in Example 1 has better cycle performance under conditions of -20℃, 30℃, and 60℃.

[0088] Figure 16 This is an electrostatic potential diagram of DME, MTOS, and TTE solvent molecules. The electron cloud density around the O atom in the DME molecule is significantly higher than that in the MTOS molecule, resulting in a greater binding energy with lithium ions and exhibiting a stronger interaction. From left to right, the solvation binding strength between the solvent molecules and lithium ions decreases.

[0089] It should be noted that in Figures 1-15 above, the label 1M LiFSI specifically means that the lithium salt in the electrolyte is LiFSI and the molar concentration of LiFSI is 1 mol / L; the label DME / DOL corresponds to Example 2, the label DME / TTE corresponds to Example 1, and the label MTOS / TTE corresponds to Example 1.

[0090] Figure 6-8 In the middle, from left to right, all satisfy the following: a and d correspond to comparative example 2, b and e correspond to comparative example 1, and c and f correspond to example 1.

[0091] This description is intended to illustrate the technical solutions of the present invention, and not to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. An electrolyte, characterized in that, The electrolyte comprises an organic solvent and a diluent, wherein the organic solvent is trimethoxymethylsilane and the diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether; and the volume ratio of the organic solvent to the diluent in the electrolyte is (9~1):(1~9).

2. The electrolyte according to claim 1, characterized in that, In the electrolyte, the volume ratio of the organic solvent to the diluent is (7~3):(3~7).

3. The electrolyte according to claim 2, characterized in that, In the electrolyte, the volume ratio of the organic solvent to the diluent is (4~6):(6~4).

4. The electrolyte according to claim 1, characterized in that, The electrolyte also includes a lithium salt, wherein the molar concentration of the lithium salt is 0.5~1.5 mol / L.

5. The electrolyte according to claim 4, characterized in that, The lithium salt includes one or more of lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, and lithium bis(trifluoromethanesulfonyl)imide.

6. The electrolyte according to claim 4, characterized in that, In the electrolyte, the volume ratio of the organic solvent to the diluent is (4~6):(6~4); the molar concentration of the lithium salt is 0.5~1.5 mol / L.

7. The electrolyte according to any one of claims 1-6, characterized in that, The Raman solvation peak of the electrolyte at -20 to 60°C is located at 740.1 to 744.0 cm⁻¹. -1 .

8. A lithium metal battery, characterized in that, Includes the electrolyte as described in any one of claims 1 to 7.

9. The lithium metal battery according to claim 8, characterized in that, The lithium metal battery includes a positive electrode, which includes a positive electrode active material selected from sulfurized polyacrylonitrile.

10. The lithium metal battery according to claim 8, characterized in that, The lithium metal battery includes a lithium anode, which comprises lithium metal or a lithium alloy.

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