Preparation method and application of low-temperature-resistant and high-voltage-resistant ether-based electrolyte

Abstract

The invention discloses a preparation method and application of a low-temperature-resistant and high-voltage-resistant ether-based electrolyte, and belongs to the technical field of lithium metal battery electrolytes. The invention aims to solve the problems that the traditional commercial ester-based electrolyte is poor in adaptability to a lithium metal battery and poor in weather resistance. The low-temperature-resistant and high-voltage-resistant ether-based electrolyte comprises lithium bis (fluorosulfonyl) imide, lithium difluoro (oxalato) borate, ethylene glycol diethyl ether and 1, 1, 2, 2-tetrafluoroethyl 2, 2, 3, 3-tetrafluoropropyl ether. The low-temperature-resistant and high-voltage-resistant ether-based electrolyte is applied to a lithium metal battery. The problems that a traditional commercial ester-based electrolyte is poor in adaptability to a lithium metal battery and poor in weather resistance are solved, the circulation rate stability of the ether-based electrolyte in the high-voltage and wide-temperature environment is obviously improved, and the ether-based electrolyte is suitable for the fields of electric automobiles, high-power energy storage equipment and the like which have strict requirements on the fast charging performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium metal battery electrolyte technology, specifically relating to a method for preparing and applying a low-temperature resistant and high-voltage ether-based electrolyte. Background Technology

[0002] With the global energy structure transformation, electric vehicles, energy storage systems, mobile devices, and the low-altitude economy have experienced rapid development. These cutting-edge technology industries have placed unprecedentedly stringent demands on the energy density, power density, safety, and cycle life of electrochemical energy storage systems. However, the energy density of lithium-ion batteries, which currently dominate the market, is gradually approaching its theoretical limit, making it difficult to meet the needs of future technological iterations. Therefore, developing next-generation battery systems with higher energy density has become an essential path to support national energy strategies and lead industrial upgrading.

[0003] Against this backdrop, lithium metal batteries, due to their extremely high theoretical specific capacity and lowest electrochemical potential of anode materials, are widely regarded as the most promising breakthrough direction. However, the path from laboratory to industrialization is fraught with difficulties, with the core bottleneck being the lack of a "universal" electrolyte that can simultaneously "tame" highly active lithium metal anodes and "match" high-voltage cathodes. Traditional commercial carbonate electrolytes are unstable at the high voltages required for high-energy-density batteries and are incompatible with lithium metal anodes, leading to severe interfacial side reactions and lithium dendrite growth, causing safety risks and rapid capacity decay. On the other hand, ether electrolytes, which can coexist stably with lithium metal, have poor oxidation resistance and cannot withstand the harsh environment of high-voltage cathodes, greatly limiting the improvement of battery energy density. This sharp contradiction has long trapped lithium metal batteries, especially in applications pursuing extreme fast charging, in the dilemma of "high energy density, but no high power output and long lifespan guarantee." Existing electrolyte modification strategies often focus on local repairs of single interfaces, making it difficult to fundamentally coordinate the inherent contradiction between solvation structure and interfacial kinetics. Especially under high-rate charge and discharge conditions, the energy barrier for lithium ions to remove the solvation shell at the electrode interface becomes the rate-controlling step that restricts ion migration, directly determining the fast-charging performance limit of the battery. Summary of the Invention

[0004] The purpose of this invention is to solve the problems of poor compatibility and poor weather resistance of traditional commercial ester-based electrolytes with lithium metal batteries, and to provide a method for preparing and applying a low-temperature resistant and high-voltage ether-based electrolyte.

[0005] The emergence of this invention is timely. To address the aforementioned technical problems, this invention takes a unique approach, starting from the essence of regulating the solvation structure of the electrolyte. By constructing a high-entropy electrolyte system, it quantifies and establishes a direct correlation between solvation entropy and performance. This innovative high-entropy design actively guides anions into the solvation shell of lithium ions, significantly reducing the critical desolvation energy barrier and enabling ultrafast lithium ion migration, allowing the battery to operate stably even at extreme rates up to 20°C. Furthermore, through the preferential decomposition of anions, it constructs a robust and stable interface protection layer on the surfaces of both the positive and negative electrodes. This high-quality positive electrode passivation layer (CEI) effectively resists oxidation corrosion under high voltage, while the excellent negative electrode passivation layer (SEI) inhibits the growth of lithium dendrites, thus simultaneously solving the century-old problem of high-voltage compatibility and lithium metal stability.

[0006] The significance of this invention lies not only in providing a specific electrolyte formulation, but also in offering a completely new electrolyte design paradigm. It successfully breaks through the traditional constraints of lithium metal batteries in terms of high voltage and high rate performance, laying a solid material foundation and scientific theoretical support for the practical application of next-generation high-power lithium metal batteries in key "low-altitude economy" fields such as ultra-fast charging of electric vehicles, large-scale energy storage frequency regulation, and long-endurance drones.

[0007] A low-temperature resistant and high-voltage resistant ether-based electrolyte, comprising lithium difluorosulfonylimide (LiFSI), lithium difluorooxalate borate (LiDFOB), ethylene glycol diethyl ether (DEE), and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE).

[0008] A method for preparing a low-temperature resistant and high-voltage resistant ether-based electrolyte is specifically carried out according to the following steps:

[0009] 1. Molecular sieves were added to lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether for physical dehydration, respectively, to obtain physically dehydrated lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether;

[0010] 2. At room temperature, in a glove box filled with argon gas, physically dehydrated lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether are mixed evenly and stirred to obtain a low-temperature resistant and high-voltage ether-based electrolyte.

[0011] Application of a low-temperature resistant and high-voltage ether-based electrolyte in lithium metal batteries.

[0012] Advantages of this invention:

[0013] I. The low-temperature and high-voltage ether-based electrolyte of this invention is a high-performance electrolyte prepared by mixing a dual salt and an ether-based solvent. It quantifies the solvation entropy during electrolyte solvation and establishes the relationship between entropy and solvation structure. This statistically high-entropy system promotes the entry of more anions into the solvation shell of lithium ions, reduces the solvent desolvation barrier, effectively improves the difficulty of lithium ion desolvation and the continuous decomposition of the electrolyte under high voltage. The positive electrode passivation layer (CEI) generated by the anion-rich solvation decomposition can slow down the corrosion of the cathode under high voltage and forms an excellent SEI, optimizing the desolvation kinetics at the interface and promoting the rapid migration of lithium ions; at 2.5 mg / cm³... 2 Under positive load, the maximum charge / discharge rate can reach 20C without significant capacity decay. After 1300 cycles under 10C high-rate charge / discharge conditions, the capacity remains stable.

[0014] Second, this invention solves the problems of poor compatibility and poor weather resistance of traditional commercial ester-based electrolytes with lithium metal batteries, and significantly improves the cycle rate stability of ether-based electrolytes under high pressure and wide temperature environments, making it suitable for fields with stringent requirements for fast charging performance, such as electric vehicles and high-power energy storage devices. Attached Figure Description

[0015] Figure 1 (a) is a snapshot of the molecular dynamics simulation of the FD-DT electrolyte; (b) is the radial distribution function and oxygen coordination number distribution of the FD-DT electrolyte; (c) is a snapshot of the molecular dynamics simulation of the 1M-DME electrolyte; (d) is the radial distribution function and oxygen coordination number distribution of the 1M-DME electrolyte; (e) is the lithium-ion solvation coordination ratio diagram of the FD-DT electrolyte; (f) is the solvation structure ratio diagram of the FD-DT electrolyte; (g) is the lithium-ion solvation coordination ratio diagram of the DME electrolyte; (h) is the solvation structure ratio diagram of the DME electrolyte; (i) is the mixing entropy diagram of different electrolytes; (j) is the solvent desolvation energy of the main solvation structure under different electrolytes; (k) is the HOMO-LUMO diagram of different solvation structures.

[0016] Figure 2 a and Figure 2 b shows the Raman spectra of different electrolytes in different wavenumber ranges. Figure 2 c shows the NMR spectra of different electrolytes;

[0017] Figure 3 SEM images of NCM811 electrodes after uncirculation, application example 1, and comparative application example 1 after circulation are shown. In the figure, (a) is the uncirculated NCM811 electrode, (b) is the NCM811 electrode after circulation in comparative application example 1, and (c) is the NCM811 electrode after circulation in application example 1.

[0018] Figure 4 The images show TEM images of NCM811 electrodes after cycling in Application Example 1 and Comparative Application Example 1. In the figures, (a) is the NCM811 electrode after cycling in Comparative Application Example 1, and (b) is the NCM811 electrode after cycling in Application Example 1.

[0019] Figure 5 The figure shows the cycle coulombic efficiency of the NCM811 / / Li battery. FD-DT represents the NCM811 / / Li battery assembled in Application Example 1, and DME represents the NCM811 / / Li battery assembled in Comparative Application Example 1.

[0020] Figure 6 The figure shows the performance of NCM811 / / Li batteries at different rates. LiFD-DT is the NCM811 / / Li battery assembled in Application Example 1, and DME is the NCM811 / / Li battery assembled in Comparative Application Example 1.

[0021] Figure 7 The figure shows the cycle performance of NCM811 / / Li batteries at a conventional 1C rate. In the figure, LiFD-DT is the NCM811 / / Li battery assembled in Application Example 1, and DME is the NCM811 / / Li battery assembled in Comparative Application Example 1.

[0022] Figure 8 The figure shows the high-rate cycling performance of NCM811 / / Li batteries at 10C. In the figure, LiFD-DT is the NCM811 / / Li battery assembled in Application Example 1, and DME is the NCM811 / / Li battery assembled in Comparative Application Example 1.

[0023] Figure 9 The figure shows the performance of NCM811 / / Li batteries at different rates and their cycle performance at 1C. In the figure, 0.9-0.1-2-3 represents the NCM811 / / Li battery assembled in Application Example 1, 0.7-0.3-2-3 represents the NCM811 / / Li battery assembled in Application Example 2, and 0.5-0.5-2-3 represents the NCM811 / / Li battery assembled in Application Example 3. Detailed Implementation

[0024] Specific Implementation Method 1: This implementation method is a method for preparing a low-temperature resistant and high-voltage ether-based electrolyte, specifically completed according to the following steps:

[0025] 1. Molecular sieves were added to lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether for physical dehydration, respectively, to obtain physically dehydrated lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether;

[0026] 2. At room temperature, in a glove box filled with argon gas, physically dehydrated lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether are mixed evenly and stirred to obtain a low-temperature resistant and high-voltage ether-based electrolyte.

[0027] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage resistant ether-based electrolyte is (0.5~0.9):(0.1~0.5):2:3. The other steps are the same as in Specific Implementation Method One.

[0028] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage resistant ether-based electrolyte is 0.9:0.1:2:3. Other steps are the same as in Specific Implementation Method One or Two.

[0029] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage ether-based electrolyte is 0.7:0.3:2:3. The other steps are the same as in Specific Implementation Methods One to Three.

[0030] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that the molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage ether-based electrolyte is 0.5:0.5:2:3. The other steps are the same as in Specific Implementation Methods One to Four.

[0031] Specific Implementation Method Six: The difference between this implementation method and Specific Implementation Methods One to Five is that the stirring time in step two is 8 to 12 hours. The other steps are the same as in Specific Implementation Methods One to Five.

[0032] Specific Implementation Method Seven: This implementation method is an application of a low-temperature resistant and high-voltage ether-based electrolyte in a lithium metal battery.

[0033] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that the assembly method of the lithium metal battery is as follows:

[0034] I. Electrode Preparation:

[0035] ① Mix the active material, conductive agent and binder, and grind them in a mortar to obtain mixed electrode powder;

[0036] The active material mentioned in step 1① is NCM811; the conductive agent is Super P; and the binder is polyvinylidene fluoride.

[0037] ② Add N-methylpyrrolidone to the mixed electrode powder and stir to obtain an electrode slurry; coat the electrode slurry evenly on a copper foil with a coating thickness of 80μm~120μm; pre-dry the copper foil coated with electrode slurry in a vacuum oven at 80℃ for 1h~3h, and then dry it in a vacuum oven at 120℃ for 10h~12h to obtain an NCM811 electrode sheet;

[0038] II. Assembly of NCM811 / / Li batteries:

[0039] The negative electrode battery casing, spring sheet, gasket, lithium sheet, PP separator, NCM811 electrode, and positive electrode battery casing are stacked in that order. 30 μL of electrolyte is dropped onto each side of the separator. After sealing with a button cell sealing machine, the assembled NCM811 / / Li battery is obtained. Other steps are the same as in specific embodiments one to seven.

[0040] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in the following ways: the mass ratio of the active material, conductive agent, and binder in step one ① is 0.4:0.05:0.05; the grinding time in step one ① is 40 min to 60 min; the mass ratio of the active material in step one ① to N-methylpyrrolidone in step two ② is 0.4:2; the stirring speed in step one ② is 500 rpm to 1000 rpm, and the stirring time is 4 h to 6 h. Other steps are the same as in Specific Implementation Methods One to Eight.

[0041] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in the following ways: the diameter of the lithium sheet in step two is 14mm; the diameter of the NCM811 electrode in step two is 12mm; the diameter of the PP separator in step two is 19mm; the material of the spring sheet in step two is stainless steel; and the material of the gasket in step two is stainless steel. Other steps are the same as in Specific Implementation Methods One to Nine.

[0042] The beneficial effects of the present invention are verified using the following embodiments:

[0043] Example 1: A method for preparing a low-temperature resistant and high-voltage ether-based electrolyte, specifically comprising the following steps:

[0044] 1. Molecular sieves were added to lithium difluorosulfonylimide (LiFSI), lithium difluorooxalate borate (LiDFOB), ethylene glycol diethyl ether (DEE), and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) for physical dehydration to obtain physically dehydrated lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether.

[0045] 2. At room temperature, in a glove box filled with argon, physically dehydrated lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether were mixed evenly and stirred for 12 hours to obtain a low-temperature resistant and high-voltage ether-based electrolyte (FD-DT).

[0046] In step two, the molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage ether-based electrolyte is 0.9:0.1:2:3.

[0047] Example 2: The difference between this example and Example 1 is that the molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage ether-based electrolyte described in step two is 0.7:0.3:2:3. All other steps and parameters are the same as in Example 1.

[0048] Example 3: The difference between this example and Example 1 is that the molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage ether-based electrolyte described in step two is 0.5:0.5:2:3. All other steps and parameters are the same as in Example 1.

[0049] Comparative Example 1: The preparation method of DME electrolyte is carried out according to the following steps:

[0050] 1. Molecular sieves were added to ethylene glycol dimethyl ether solvent (DME) and lithium bisfluorosulfonyl imide (LiFSI) respectively for physical dehydration to obtain physically dehydrated ethylene glycol dimethyl ether solvent (DME) and lithium bisfluorosulfonyl imide (LiFSI).

[0051] 2. Mix the physically dehydrated ethylene glycol dimethyl ether solvent (DME) and lithium bis(fluorosulfonyl)imide (LiFSI) evenly and stir for 12 hours to obtain DME electrolyte;

[0052] In step two, the molar ratio of lithium bis(fluorosulfonyl)imide (LiFSI) to dimethyl ethylene glycol (DME) solvent in the DME electrolyte is 1:8.

[0053] Application Example 1: The assembly method of NCM811 / / Li battery is specifically completed according to the following steps:

[0054] I. Electrode Preparation:

[0055] ① Mix 0.4g of active material, 0.05g of conductive agent and 0.05g of binder, and grind them in a mortar for 60 minutes to obtain mixed electrode powder;

[0056] The active material mentioned in step 1① is NCM811; the conductive agent is Super P; and the binder is polyvinylidene fluoride.

[0057] ② Add 2g of N-methylpyrrolidone to the mixed electrode powder and stir at 500rpm for 5h to obtain electrode slurry; coat the electrode slurry evenly on copper foil with a coating thickness of 100μm; pre-bake the copper foil coated with electrode slurry in a vacuum oven at 80℃ for 2h, and then dry it in a vacuum oven at 120℃ for 12h to obtain NCM811 electrode sheet;

[0058] II. Assembly of NCM811 / / Li batteries:

[0059] The negative electrode battery casing, spring sheet, gasket, lithium sheet, PP separator, NCM811 electrode, and positive electrode battery casing are stacked in that order. 30 μL of the low-temperature resistant and high-voltage ether-based electrolyte prepared in Example 1 is dropped onto both sides of the separator. After sealing with a button battery sealing machine, the NCM811 / / Li battery assembly is completed (denoted as 0.9-0.1-2-3).

[0060] The lithium sheet mentioned in step two has a diameter of 14mm; the NCM811 electrode mentioned in step two has a diameter of 12mm; the PP separator mentioned in step two has a diameter of 19mm; the spring sheet mentioned in step two is made of stainless steel; the gasket mentioned in step two is made of stainless steel.

[0061] Application Example 2: The difference between this application example and Application Example 1 is that in step two, the low-temperature resistant and high-voltage ether-based electrolyte prepared in Example 1 is replaced with the low-temperature resistant and high-voltage ether-based electrolyte prepared in Example 2; the NCM811 / / Li battery assembled in step two is designated as 0.7-0.3-2-3. All other steps and parameters are the same as in Application Example 1.

[0062] Application Example 3: The difference between this application example and Application Example 1 is that in step two, the low-temperature resistant and high-voltage ether-based electrolyte prepared in Example 1 is replaced with the low-temperature resistant and high-voltage ether-based electrolyte prepared in Example 3; the NCM811 / / Li battery assembled in step two is designated as 0.5-0.5-2-3. All other steps and parameters are the same as in Application Example 1.

[0063] Comparative Application Example 1: The difference between this application example and Application Example 1 is that in step two, the low-temperature resistant and high-voltage ether-based electrolyte prepared in Example 1 is replaced with the DME electrolyte prepared in Comparative Example 1. All other steps and parameters are the same as in Application Example 1.

[0064] Figure 1 (a) is a snapshot of the molecular dynamics simulation of the FD-DT electrolyte; (b) is the radial distribution function and oxygen coordination number distribution of the FD-DT electrolyte; (c) is a snapshot of the molecular dynamics simulation of the 1M-DME electrolyte; (d) is the radial distribution function and oxygen coordination number distribution of the 1M-DME electrolyte; (e) is the lithium-ion solvation coordination ratio diagram of the FD-DT electrolyte; (f) is the solvation structure ratio diagram of the FD-DT electrolyte; (g) is the lithium-ion solvation coordination ratio diagram of the DME electrolyte; (h) is the solvation structure ratio diagram of the DME electrolyte; (i) is the mixing entropy diagram of different electrolytes; (j) is the solvent desolvation energy of the main solvation structure under different electrolytes; (k) is the HOMO-LUMO diagram of different solvation structures.

[0065] from Figure 1 In d, the coordination number of DME molecules with lithium ions is much higher than that of FSI- anions with lithium ions. Figure 1 In the FD-DT modified electrolyte (b), the coordination number of FSI- anions is significantly increased, while the coordination number of DEE molecules with lithium ions is reduced to half that of DME molecules. This indicates that the 1M-DME electrolyte has a solvent-dominated solvation structure, while the FD-DT electrolyte has an anion-dominated solvation structure. Figure 1 e and f represent the proportion of lithium-ion solvation coordination and the proportion of solvation structure in the FD-DT electrolyte, respectively. Figure 1 g and h represent the lithium-ion solvation coordination ratio and solvation structure ratio of the 1M-DME electrolyte, respectively. It can be seen that the solvation structure of the FD-DT electrolyte is more uniform and diverse, providing conditions for the formation of a good interface. To explain the reason for this phenomenon, from the perspective of thermodynamic theoretical calculations combined with molecular dynamics simulation results, a new descriptor for the solvation structure of the system—the solvation mixing entropy—was constructed. Figure 1i). The increase in mixing entropy indicates a more diversified electrolyte solvation structure, with more anions participating in the lithium-ion solvation shell, accompanied by a decrease in the solvation desolvation energy barrier (Fig. j). The addition of LiDFOB increases the HOMO level, which helps to form a stable passivation layer on the cathode surface (Fig. k).

[0066] Figure 2 a and Figure 2 b shows the Raman spectra of different electrolytes in different wavenumber ranges. Figure 2 c shows the NMR spectra of different electrolytes;

[0067] Figure 2 1 M-DME is a 1 M LiFSI electrolyte with DME as solvent; 1 M-DEE is a 1 M LiFSI electrolyte with DEE as solvent; F-DT is an electrolyte with TTE and DEE as solvents and LiFSI as lithium salt, wherein the molar ratio of LiFSI:DEE:TTE is 1:2:3; FD-DT is the low-temperature resistant and high-voltage ether-based electrolyte prepared in Example 1; DEE-TTE is a mixed solvent with a DEE:TTE molar ratio of 2:3.

[0068] The above results demonstrate that the methylation and localized high-concentration strategies employed in this invention effectively promote the participation of anions in Li. + In the solvation structure, with Figure 1 The theoretical and technical results are consistent.

[0069] Figure 3 SEM images of NCM811 electrodes after uncirculation, application example 1, and comparative application example 1 after circulation are shown. In the figure, (a) is the uncirculated NCM811 electrode, (b) is the NCM811 electrode after circulation in comparative application example 1, and (c) is the NCM811 electrode after circulation in application example 1.

[0070] Figure 4 The images show TEM images of NCM811 electrodes after cycling in Application Example 1 and Comparative Application Example 1. In the figures, (a) is the NCM811 electrode after cycling in Comparative Application Example 1, and (b) is the NCM811 electrode after cycling in Application Example 1.

[0071] from Figure 3 As can be seen in (a), the NCM811 polycrystalline particles were initially intact; from Figure 3 As can be seen in (b), the NCM811 particles after cycling with the DME-based electrolyte exhibited obvious cracking and uneven lithium deposition; from Figure 3As can be seen in (c), the initial structure in (a) without cycling is not significantly different; the surface deposition is uniform and crack-free, thus protecting the positive electrode surface. By comparing the CEI films of the two electrolytes on the surface of NCM811 particles, it can be seen that the DME-based ( Figure 4 (a) The CEI film has uneven thickness and exceeds 10 nm, while the modified ( Figure 4 (b) The CEI film is thin and uniform. This also verifies the benefits of the mixed entropy-increasing electrolyte system for the NCM811 cathode surface from the perspective of electrode characterization, laying the foundation for stable and rapid battery charge-discharge cycles.

[0072] Figure 5 The figure shows the cycle coulombic efficiency of the NCM811 / / Li battery. FD-DT represents the NCM811 / / Li battery assembled in Application Example 1, and DME represents the NCM811 / / Li battery assembled in Comparative Application Example 1.

[0073] from Figure 5 It can be seen that the modified electrolyte (the high-voltage, wide-temperature-range, high-energy-density battery electrolyte prepared in Example 1) has a significantly improved coulombic efficiency compared to the DME-based electrolyte, indicating that it has excellent compatibility with lithium metal anodes and excellent cycle stability.

[0074] Figure 6 The figure shows the performance of NCM811 / / Li batteries at different rates. LiFD-DT is the NCM811 / / Li battery assembled in Application Example 1, and DME is the NCM811 / / Li battery assembled in Comparative Application Example 1.

[0075] Figure 7 The figure shows the cycle performance of NCM811 / / Li batteries at a conventional 1C rate. In the figure, LiFD-DT is the NCM811 / / Li battery assembled in Application Example 1, and DME is the NCM811 / / Li battery assembled in Comparative Application Example 1.

[0076] Comparison of rate and cycle performance tests shows that the modified electrolyte (the high-voltage, wide-temperature-range, high-energy-density battery electrolyte prepared in Example 1) released extremely high discharge capacity at different rates, and the capacity could still be maintained at 86% after 400 cycles of long-term stable operation.

[0077] Figure 8 The figure shows the high-rate cycling performance of NCM811 / / Li batteries at 10C. In the figure, LiFD-DT is the NCM811 / / Li battery assembled in Application Example 1, and DME is the NCM811 / / Li battery assembled in Comparative Application Example 1.

[0078] from Figure 8It can be seen that under a high current of 10C, the rate performance of DME is poor, the capacity is not fully utilized and the capacity decays quickly; the modified electrolyte (the high-voltage, wide-temperature-range, high-energy-density battery electrolyte prepared in Example 1) still has a stable discharge capacity after 1200 cycles, which shows excellent high-rate stability.

[0079] Figure 9 The figure shows the performance of NCM811 / / Li batteries at different rates and their cycle performance at 1C. In the figure, 0.9-0.1-2-3 represents the NCM811 / / Li battery assembled in Application Example 1, 0.7-0.3-2-3 represents the NCM811 / / Li battery assembled in Application Example 2, and 0.5-0.5-2-3 represents the NCM811 / / Li battery assembled in Application Example 3.

[0080] from Figure 9 It can be seen that the salt ratio affects the performance of the electrolyte, and the battery assembled with an electrolyte ratio of 0.9-0.1-2-3 has the best performance.

Claims

1. A method for preparing a low-temperature resistant and high-voltage ether-based electrolyte, characterized in that... The preparation method is specifically carried out according to the following steps:

1. Molecular sieves were added to lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether for physical dehydration, respectively, to obtain physically dehydrated lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether; 2. At room temperature, in a glove box filled with argon gas, physically dehydrated lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether are mixed evenly and stirred to obtain a low-temperature resistant and high-voltage ether-based electrolyte.

2. The method for preparing a low-temperature resistant and high-voltage ether-based electrolyte according to claim 1, characterized in that... The molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage resistant ether-based electrolyte is (0.5~0.9):(0.1~0.5):2:

3.

3. The method for preparing a low-temperature resistant and high-voltage ether-based electrolyte according to claim 2, characterized in that... The molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage resistant ether-based electrolyte is 0.9:0.1:2:

3.

4. The method for preparing a low-temperature resistant and high-voltage resistant ether-based electrolyte according to claim 2, characterized in that... The molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage resistant ether-based electrolyte is 0.7:0.3:2:

3.

5. The method for preparing a low-temperature resistant and high-voltage ether-based electrolyte according to claim 2, characterized in that... The molar ratio of lithium difluorosulfonylimide, lithium difluorooxalate borate, ethylene glycol diethyl ether, and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the low-temperature resistant and high-voltage resistant ether-based electrolyte is 0.5:0.5:2:

3.

6. The method for preparing a low-temperature resistant and high-voltage ether-based electrolyte according to claim 1, characterized in that... The stirring time mentioned in step two is 8h~12h.

7. The application of the low-temperature resistant and high-voltage ether-based electrolyte as described in claim 1, characterized in that... Application of a low-temperature resistant and high-voltage ether-based electrolyte in lithium metal batteries.

8. The application of the low-temperature resistant and high-voltage ether-based electrolyte according to claim 7, characterized in that... The assembly method of the lithium metal battery is as follows: I. Electrode Preparation: ① Mix the active material, conductive agent and binder, and grind them in a mortar to obtain mixed electrode powder; The active material mentioned in step 1① is NCM811; the conductive agent is Super P; and the binder is polyvinylidene fluoride. ② Add N-methylpyrrolidone to the mixed electrode powder and stir to obtain an electrode slurry; coat the electrode slurry evenly on a copper foil with a coating thickness of 80μm~120μm; pre-dry the copper foil coated with electrode slurry in a vacuum oven at 80℃ for 1h~3h, and then dry it in a vacuum oven at 120℃ for 10h~12h to obtain an NCM811 electrode sheet; II. Assembly of NCM811 / / Li batteries: The negative electrode battery casing, spring sheet, gasket, lithium sheet, PP separator, NCM811 electrode, and positive electrode battery casing are stacked in that order. 30μL of electrolyte is dropped onto both sides of the separator. After sealing with a button cell sealing machine, the NCM811 / / Li battery assembly is obtained.

9. The application of the low-temperature resistant and high-voltage ether-based electrolyte according to claim 8, characterized in that... The mass ratio of the active material, conductive agent, and binder mentioned in step 1① is 0.4:0.05:0.05; the grinding time mentioned in step 1① is 40 min to 60 min; the mass ratio of the active material mentioned in step 1① to the N-methylpyrrolidone mentioned in step 2② is 0.4:2; the stirring speed mentioned in step 1② is 500 rpm to 1000 rpm, and the stirring time is 4 h to 6 h.

10. The application of the low-temperature resistant and high-voltage ether-based electrolyte according to claim 8, characterized in that... The lithium sheet mentioned in step two has a diameter of 14mm; the NCM811 electrode mentioned in step two has a diameter of 12mm; the PP separator mentioned in step two has a diameter of 19mm; the spring sheet mentioned in step two is made of stainless steel; the gasket mentioned in step two is made of stainless steel.

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