High-voltage-resistant electrolyte for lithium metal battery and lithium metal battery
By using tetrabutylammonium hexafluorophosphate and lithium difluorooxalate borate to form an SEI film in lithium metal batteries, and combining it with fluoroethylene carbonate and difluoroethylene carbonate to improve the electrolyte, the problem of reaction between the electrolyte and the lithium metal anode in lithium-ion batteries was solved, and the high-voltage cycle stability and ion transport performance were improved.
Patent Information
- Application Number
- CN202511986012.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-26
- Publication Date
- 2026-04-03
AI Technical Summary
Traditional lithium-ion battery electrolytes react with the lithium metal anode in lithium metal batteries to produce hydrogen and hydrocarbon gases, leading to battery swelling, lithium consumption, and dendrite growth, which reduces safety and cycle performance.
Tetrabutylammonium hexafluorophosphate and lithium difluorooxalate borate were used as additives to form a dense inorganic-organic hybrid SEI film, which optimized the electrode interface. The electrostatic shielding effect of tetrabutylammonium hexafluorophosphate was used to suppress dendrite growth, while fluoroethylene carbonate and difluoroethylene carbonate were used to improve ion transport performance.
It improves the high-voltage cycle stability and ion transport performance of lithium metal batteries, enhances rate performance, and maintains a capacity retention rate of over 80% after 1000 cycles.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium metal battery technology, and more particularly to a high-voltage resistant electrolyte for lithium metal batteries and a lithium metal battery. Background Technology
[0002] Electrolyte, as an important component of lithium metal batteries, has a significant impact on the various performance characteristics of lithium metal batteries.
[0003] Traditional lithium-ion battery electrolytes mostly use carbonates as solvents, which introduces numerous problems when directly applied to lithium metal batteries. First, the reaction between the lithium metal anode and the carbonate solvent produces large amounts of hydrogen and hydrocarbon gases, causing battery swelling. Simultaneously, numerous side reactions induce significant lithium metal consumption and the formation and growth of lithium dendrites, greatly reducing the battery's safety and cycle performance.
[0004] Therefore, developing a novel, non-traditional carbonate electrolyte that is stable with lithium metal anodes is of great significance. Summary of the Invention
[0005] To address the aforementioned technical problems, this invention provides a high-voltage resistant electrolyte for lithium metal batteries and a lithium metal battery, which can improve ion transport performance and simultaneously enhance the battery's rate performance and high-voltage cycle stability.
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] In a first aspect, the present invention provides a high-voltage resistant electrolyte for lithium metal batteries, the high-voltage resistant electrolyte comprising an electrolyte salt, an organic solvent, and additives. The additives include tetrabutylamine hexafluorophosphate and lithium difluorooxalate borate.
[0008] The lithium difluorooxalate borate in the high-voltage electrolyte provided by this invention is mainly used to optimize the electrode interface. LiDFOB has a high reduction potential and preferentially decomposes on the lithium anode surface, forming an inorganic-organic hybrid SEI film rich in B, O, and F elements. This film is dense, uniform, has good mechanical strength, and high ionic conductivity, effectively isolating the electrolyte from side reactions with lithium and buffering volume changes. Tetrabutylamine hexafluoroborate (TBAPF6), as a large-cation quaternary ammonium salt additive, is mainly used to regulate lithium-ion deposition kinetics (suppress dendrite formation), and large-size Bu4N... + Cations exhibit an electrostatic shielding effect; during lithium deposition, they preferentially adsorb at the tips (dendritic buds) caused by surface inhomogeneities, but are not reduced. This adsorption shields the high electric field at the tips, forcing Li to... +Lithium ions deposit in flat regions with weaker electric fields, kinetically guiding their smooth, two-dimensional growth on the formed SEI film, rather than vertical dendrite growth. In short, the synergistic effect of LiDFOB and TBAPF6 lies in this: LiDFOB first constructs a high-quality SEI film, reducing the resistance to lithium ion crossing the interface and stabilizing the interface, while TBAPF6 utilizes electrostatic shielding to ensure uniform deposition of lithium ions on the SEI film. The combination of the two achieves comprehensive protection from thermodynamics (interface stabilization) to kinetics (uniform deposition), resulting in a dendrite suppression effect far superior to using either additive alone.
[0009] Preferably, the mass percentage of the additive in the high-voltage electrolyte is 0.1~4.5wt%, for example, it can be 0.1wt%, 0.6wt%, 1.1wt%, 1.6wt%, 2.1wt%, 2.6wt%, 3.1wt%, 3.6wt%, 4.1wt%, or 4.5wt%, etc., but is not limited to the listed values, and other unlisted values within this range are also applicable.
[0010] Preferably, the mass ratio of tetrabutylammonium hexafluorophosphate to lithium difluorooxalate borate is 1:(1.8~2), for example, it can be 1:1.8, 1:1.82, 1:1.83, 1:1.85, 1:1.88, 1:1.89, 1:1.9, 1:1.95, 1:1.98 or 1:2, etc., but is not limited to the listed values, and other unlisted values within this range are also applicable.
[0011] The present invention preferably controls the mass ratio of tetrabutylammonium hexafluorophosphate and lithium difluorooxalate borate within the above-mentioned range, which can better improve the high-voltage cycle stability and rate performance of lithium metal batteries.
[0012] Preferably, the electrolyte salt comprises lithium bis(fluorosulfonyl)imide.
[0013] Preferably, the molar concentration of the electrolyte salt in the high-voltage resistant electrolyte is 1~3 mol / L, for example, it can be 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.7 mol / L, 1.9 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L or 3 mol / L, but is not limited to the listed values. Other unlisted values within this range are also applicable.
[0014] Preferably, the organic solvent includes fluorocarbonate.
[0015] Preferably, the fluorocarbonate includes fluoroethylene carbonate and difluoroethylene carbonate.
[0016] Since tetrabutylamine hexafluorophosphate and lithium difluorooxalate borate, when used as electrolyte additives, may generate insoluble substances that clog electrode pores or increase electrolyte viscosity, thus deteriorating ion transport performance, fluoroethylene carbonate and difluoroethylene carbonate are added as solvents. Through pre-charge and discharge, a stable SEI film rich in LiF is formed on the electrode surface, reducing the direct reaction between the electrolyte and the electrode, indirectly reducing the amount of by-products generated, thereby improving ion transport performance.
[0017] Specifically, the introduction of a strong electron-withdrawing group (-F) in fluoroethylene carbonate (FEC) weakens the stability of the carbonate ring, making it easier to open the ring at the reduction potential, but it still retains some organic characteristics. The introduction of two -F groups in difluoroethylene carbonate (DFEC) produces an even stronger electron-withdrawing effect, making the entire molecule extremely unstable, and the CF bond is easily broken (defluorinated), thus its reactivity is much higher than that of FEC. On the negative electrode surface, FEC is preferentially reduced over EC (polymerization-dominated), and the main reaction pathway is ring-opening polymerization, generating poly(fluoroethylene carbonate) and other polymer chains. Simultaneously, some CF bonds break to generate LiF, and the resulting SEI film is a composite material of an organic polymer network and inorganic LiF nanoparticles. This structure achieves a good balance between toughness and rigidity. DFEC has the highest reduction potential and is the first to be reduced in the electrolyte (defluorination-dominated). The main reaction is a rapid, multi-step defluorination reaction, and the resulting SEI film is rich in LiF, with a very high proportion of inorganic components, a dense and rigid structure, and low ionic conductivity. FEC can oxidize and decompose on the positive electrode side to form a CEI film, but DFEC has a more obvious advantage under high voltage. Its decomposition products can form a robust CEI film on the positive electrode surface, effectively inhibiting electrolyte oxidation, transition metal dissolution and oxygen release, significantly improving high-voltage cycling and high-temperature storage performance, and does not produce gas. The combination of the two can significantly improve the performance of lithium metal batteries.
[0018] Preferably, the mass ratio of fluoroethylene carbonate to difluoroethylene carbonate in the fluorocarbonate is (1~5):(0.5~3). The number of parts of fluoroethylene carbonate can be, for example, 1, 1.5, 1.9, 2.4, 2.8, 3.3, 3.7, 4.2, 4.6 or 5, etc., but is not limited to the listed values, and other unlisted values within this range are also applicable; the number of parts of difluoroethylene carbonate can be, for example, 0.5, 0.8, 1.1, 1.4, 1.7, 1.9, 2.2, 2.5, 2.8 or 3, etc., but is not limited to the listed values, and other unlisted values within this range are also applicable.
[0019] The present invention does not impose any special restrictions on the preparation method of the high-voltage resistant electrolyte for lithium metal batteries in the above process. Any apparatus and method known to those skilled in the art can be used for preparation. The method can also be adjusted according to the actual process, such as uniform mixing.
[0020] In a second aspect, the present invention provides a lithium metal battery, the lithium metal battery comprising the high-voltage resistant electrolyte for lithium metal batteries described in the first aspect.
[0021] Preferably, the lithium metal battery comprises a lithium metal anode material.
[0022] This invention does not impose any special limitations on other materials used for the positive electrode in the aforementioned lithium metal battery. Any other materials known to those skilled in the art for use as the positive electrode can be employed, and adjustments can be made according to the actual process. For example, the conductive agent can be any one or a combination of at least two of acetylene black, carbon black, or graphite. Furthermore, the binder is polyvinylidene fluoride.
[0023] The present invention does not impose any special restrictions on the separator in the above-mentioned lithium metal battery. Any material known to those skilled in the art that can be used for the separator can be used, and adjustments can also be made according to the actual process. For example, it can be polypropylene, polyethylene, etc.
[0024] Compared with the prior art, the present invention has at least the following beneficial effects:
[0025] The high-voltage resistant electrolyte for lithium metal batteries provided by this invention can improve the high-voltage cycle stability of spinel-type nickel-manganese lithium metal cathode batteries, and also improve ion transport performance and rate performance. Batteries prepared using the high-voltage resistant electrolyte for lithium metal batteries provided by this invention retain more than 80% of their capacity after 1000 cycles under 3.5-5V and 1C conditions. Detailed Implementation
[0026] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.
[0027] The electrolyte is crucial because during the charging and discharging process, lithium ions rapidly escape from the positive electrode, enter the electrolyte, pass through the separator, and are embedded in the negative electrode. The migration of a large number of lithium ions requires the electrolyte to have high kinetic performance, so that the lithium ions have less mass transfer resistance during the mass transfer process. Therefore, the electrolyte needs to have better wettability, lower viscosity, and lower lithium ion transport resistance.
[0028] This invention improves the ion transport capacity of the electrolyte under high pressure conditions by adjusting the composition of the electrolyte, alleviates the dendrite problem in lithium metal batteries, and enhances the cycle stability of lithium metal batteries.
[0029] For ease of experimental comparison, the preparation method of the high-voltage resistant electrolyte for lithium metal batteries in the following examples and comparative examples includes: mixing electrolyte salt, organic solvent and additives to obtain the high-voltage resistant electrolyte for lithium metal batteries.
[0030] Example 1
[0031] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries, which includes an electrolyte salt, an organic solvent, and additives.
[0032] The additives include tetrabutylamine hexafluorophosphate and lithium difluorooxalate borate.
[0033] The additive in the high-voltage resistant electrolyte has a mass percentage content of 2.5 wt%.
[0034] The mass ratio of tetrabutylammonium hexafluorophosphate to lithium difluorooxalate borate is 1:2.
[0035] The electrolyte salt includes lithium bis(fluorosulfonyl)imide. The molar concentration of the electrolyte salt in the high-voltage resistant electrolyte is 2 mol / L.
[0036] The organic solvent includes fluorocarbonate. The fluorocarbonate includes fluoroethylene carbonate and difluoroethylene carbonate. The mass ratio of fluoroethylene carbonate to difluoroethylene carbonate in the fluorocarbonate is 3:1.
[0037] Example 2
[0038] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries, which includes an electrolyte salt, an organic solvent, and additives.
[0039] The additives include tetrabutylamine hexafluorophosphate and lithium difluorooxalate borate.
[0040] The additive in the high-voltage resistant electrolyte has a mass percentage content of 0.5 wt%.
[0041] The mass ratio of tetrabutylamine hexafluorophosphate to lithium difluorooxalate borate is 1:1.8.
[0042] The electrolyte salt includes lithium bis(fluorosulfonyl)imide. The molar concentration of the electrolyte salt in the high-voltage resistant electrolyte is 3 mol / L.
[0043] The organic solvent includes fluorocarbonate. The fluorocarbonate includes fluoroethylene carbonate and difluoroethylene carbonate. The mass ratio of fluoroethylene carbonate to difluoroethylene carbonate in the fluorocarbonate is 1:0.5.
[0044] Example 3
[0045] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries, which includes an electrolyte salt, an organic solvent, and additives.
[0046] The additives include tetrabutylamine hexafluorophosphate and lithium difluorooxalate borate.
[0047] The additive in the high-voltage electrolyte has a mass percentage of 4.5 wt%.
[0048] The mass ratio of tetrabutylammonium hexafluorophosphate to lithium difluorooxalate borate is 1:1.9.
[0049] The electrolyte salt includes lithium bis(fluorosulfonyl)imide. The molar concentration of the electrolyte salt in the high-voltage resistant electrolyte is 1 mol / L.
[0050] The organic solvent includes fluorocarbonate. The fluorocarbonate includes fluoroethylene carbonate and difluoroethylene carbonate. The mass ratio of fluoroethylene carbonate to difluoroethylene carbonate in the fluorocarbonate is 5:3.
[0051] Example 4
[0052] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries. Except for replacing lithium difluorosulfonylimide with lithium hexafluorophosphate, the high-voltage resistant electrolyte for lithium metal batteries is the same as that in Example 1, and will not be described again here.
[0053] Example 5
[0054] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries. Except for the mass ratio of tetrabutylammonium hexafluorophosphate and lithium difluorooxalate borate being 1:2.5, the high-voltage resistant electrolyte for lithium metal batteries is the same as that in Example 1, and will not be repeated here.
[0055] Example 6
[0056] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries. Except for the mass ratio of tetrabutylammonium hexafluorophosphate and lithium difluorooxalate borate being 1:1.5, the high-voltage resistant electrolyte for lithium metal batteries is the same as that in Example 1, and will not be repeated here.
[0057] Example 7
[0058] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries. Except for the fact that the mass percentage of additives in the high-voltage resistant electrolyte is 5 wt%, the rest of the high-voltage resistant electrolyte is the same as that in Example 1, and will not be repeated here.
[0059] Example 8
[0060] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries. Except for the fact that the mass percentage of additives in the high-voltage resistant electrolyte is 0.05 wt%, the rest of the high-voltage resistant electrolyte is the same as that in Example 1, and will not be repeated here.
[0061] Example 9
[0062] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries. Except for the fact that all the fluorocarbonate is fluoroethylene carbonate, the high-voltage resistant electrolyte for lithium metal batteries is the same as that in Example 1, and will not be described again here.
[0063] Example 10
[0064] This embodiment provides a high-voltage resistant electrolyte for lithium metal batteries. Except for the fact that all the fluorocarbonate in the high-voltage resistant electrolyte for lithium metal batteries is difluoroethylene carbonate, the rest is the same as in Example 1, and will not be repeated here.
[0065] Comparative Example 1
[0066] This comparative example provides an electrolyte. The high-voltage resistant electrolyte for lithium metal batteries is the same as in Example 1, except that all tetrabutylammonium hexafluorophosphate is replaced with lithium difluorooxalate borate. Therefore, it will not be described again here.
[0067] Comparative Example 2
[0068] This comparative example provides an electrolyte. The high-voltage resistant electrolyte for lithium metal batteries is the same as in Example 1, except that lithium difluorooxalate borate is completely replaced with tetrabutylammonium hexafluorophosphate. Therefore, it will not be described again here.
[0069] Comparative Example 3
[0070] This comparative example provides an electrolyte. The high-voltage resistant electrolyte for lithium metal batteries is the same as that in Example 1, except that tetrabutylammonium hexafluorophosphate is replaced with dibutylammonium hexafluorophosphate. It will not be described again here.
[0071] Comparative Example 4
[0072] This comparative example provides an electrolyte. The high-voltage resistant electrolyte for lithium metal batteries is the same as that in Example 1, except that lithium difluorooxalate borate is replaced with lithium borate. It will not be described again here.
[0073] Battery manufacturing:
[0074] 1. Preparation of positive electrode sheet
[0075] Spinel-type lithium nickel manganese oxide positive electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5 and then added to the solvent N-methylpyrrolidone (NMP). After mixing evenly, a positive electrode slurry with a solid content of 45% was obtained. The positive electrode slurry was coated on the surface of the positive electrode current collector aluminum foil and then vacuum dried to obtain the positive electrode sheet.
[0076] 2. The diaphragm was prepared using Celgard 2400 diaphragm from Celgard Diaphragm Company, USA.
[0077] 3. Preparation of electrolyte: The electrolytes of the above examples and comparative examples were used.
[0078] 4. Assembly of lithium metal batteries: The positive electrode, separator, and lithium sheet are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The bare cell is placed in the outer packaging shell, dried, and then injected with the electrolyte. After vacuum sealing, settling, formation, and shaping, a lithium metal soft-pack battery is obtained.
[0079] Test method:
[0080] (1) Initial Coulomb efficiency
[0081] At 25℃, the lithium metal battery was charged to 5V at a constant current and constant voltage rate of 0.33C, allowed to stand for 5 minutes, and then discharged to 3.5V at a constant current rate of 0.33C, allowed to stand for 5 minutes. The initial coulombic efficiency of the lithium metal battery was calculated. Initial coulombic efficiency (%) = (Total capacity of lithium metal battery during initial discharge at 0.33C) / (Total capacity of lithium metal battery during initial charge at 0.33C) × 100%.
[0082] (2) First discharge specific capacity under 1C and 5C conditions
[0083] At 25°C, the lithium metal battery was charged to 5V at constant current and constant voltage at 1C and 5C rates, respectively, and allowed to stand for 5 minutes. Then, the lithium metal battery was discharged to 3.5V at constant current at 1C and 5C rates, respectively, and allowed to stand for 5 minutes. The discharge specific capacity of the lithium metal battery under 1C and 5C conditions was calculated.
[0084] (3) Capacity retention rate after 1000 cycles at room temperature (1°C / 1°C)
[0085] At 25°C, the lithium metal battery was charged at a constant current and constant voltage rate of 1C to 5V, with the constant voltage cutoff rate at 0.05C. After resting for 5 minutes, the lithium metal battery was discharged at a constant current rate of 1C to 3.5V and then rested for 5 minutes. This constitutes one charge-discharge cycle. The lithium metal battery was charged and discharged for 1000 cycles using the above method. The capacity retention rate of the lithium metal battery after 1000 charge-discharge cycles at 1C / 1C was calculated.
[0086] The capacity retention rate (%) of a lithium metal battery after N cycles = (discharge specific capacity of the Nth cycle / initial discharge specific capacity) × 100%, where N is the number of cycles of the lithium metal battery.
[0087] The test results of the above embodiments and comparative examples are shown in Table 1.
[0088] Table 1
[0089]
[0090] The following points can be observed from Table 1:
[0091] (1) As can be seen from the comprehensive examples 1 to 3, the high-voltage resistant electrolyte for lithium metal batteries provided by the present invention can improve the rate performance and high-voltage cycle stability of the battery. The initial coulombic efficiency is above 93%, the 1C discharge specific capacity is 137.1 mAh / g, and the 5C discharge specific capacity is 130 mAh / g, showing excellent rate performance. The capacity retention rate after 1000 cycles at room temperature 1C / 1C is above 84.5%, showing broad application prospects.
[0092] (2) In Example 4, the electrolyte salt lithium difluorosulfonylimide was replaced with lithium hexafluorophosphate, and the cycle capacity retention rate deteriorated significantly.
[0093] (3) The mass ratio of lithium difluorooxalate borate to tetrabutylammonium hexafluorophosphate in Examples 5 and 6 was too large and too small, respectively, resulting in poor battery rate and cycle life.
[0094] (4) In Example 7, the addition of excessive amounts of tetrabutylammonium hexafluorophosphate and lithium difluorooxalate borate resulted in low battery capacity and poor rate capability. In Example 8, the addition of insufficient amounts of tetrabutylammonium hexafluorophosphate and lithium difluorooxalate borate resulted in poor battery cycle performance.
[0095] (5) In Example 9, all the fluorocarbonate was fluoroethylene carbonate, which resulted in slightly poorer battery cycle life. In Example 10, all the fluorocarbonate was difluoroethylene carbonate, which resulted in lower battery capacity and a simultaneous decrease in rate.
[0096] (6) In Comparative Example 1 and Comparative Example 2, the addition of only one of tetrabutylammonium hexafluorophosphate or lithium difluorooxalate borate resulted in a decrease in both rate performance and capacity retention.
[0097] (7) In Comparative Example 3, tetrabutylammonium hexafluorophosphate (TBA-PF6) was replaced with dibutylammonium hexafluorophosphate (DBA-PF6). The dibutylammonium ion is smaller in volume than the tetrabutylammonium ion and has a stronger association with the electrolyte salt anion, resulting in a decrease in the lithium ion migration number and a worse battery rate. The space shielding effect is weaker, resulting in a decrease in the uniformity of lithium deposition and a worse battery cycle.
[0098] (8) In Comparative Example 4, lithium difluorooxalate borate was replaced with lithium borate, which had very poor performance. Lithium borate has very low solubility in organic electrolytes. Adding it to the electrolyte may form precipitates or suspended particles, causing uneven local current density, inducing lithium dendrites, increasing the risk of thermal runaway, and failing to suppress the side reactions of the positive / negative electrodes at the molecular / ionic level.
[0099] The present invention has been illustrated with the above embodiments to illustrate its detailed features, but the present invention is not limited to the above detailed features, that is, it does not mean that the present invention must rely on the above detailed features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the selected technical features, additions of auxiliary technical features, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.
Claims
1. A high-voltage resistant electrolyte for lithium metal batteries, characterized in that, The high-voltage resistant electrolyte for lithium metal batteries includes electrolyte salts, organic solvents, and additives. The additives include tetrabutylamine hexafluorophosphate and lithium difluorooxalate borate.
2. The high-voltage resistant electrolyte for lithium metal batteries according to claim 1, characterized in that, The additive in the high-voltage resistant electrolyte has a mass percentage content of 0.1~4.5wt%.
3. The high-voltage resistant electrolyte for lithium metal batteries according to claim 1 or 2, characterized in that, The mass ratio of tetrabutylammonium hexafluorophosphate to lithium difluorooxalate borate is 1:(1.8~2).
4. The high-voltage resistant electrolyte for lithium metal batteries according to any one of claims 1 to 3, characterized in that, The electrolyte salt includes lithium difluorosulfonylimide.
5. The high-voltage resistant electrolyte for lithium metal batteries according to any one of claims 1 to 4, characterized in that, The molar concentration of electrolyte salts in the high-voltage resistant electrolyte is 1~3 mol / L.
6. The high-voltage resistant electrolyte for lithium metal batteries according to any one of claims 1 to 5, characterized in that, The organic solvent includes fluorocarbonate.
7. The high-voltage resistant electrolyte for lithium metal batteries according to claim 6, characterized in that, The fluorocarbonates include fluoroethylene carbonate and difluoroethylene carbonate.
8. The high-voltage resistant electrolyte for lithium metal batteries according to claim 7, characterized in that, The mass ratio of fluoroethylene carbonate to difluoroethylene carbonate in the fluorocarbonate is (1~5):(0.5~3).
9. A lithium metal battery, characterized in that, The lithium metal battery includes the high-voltage resistant electrolyte for lithium metal batteries as described in any one of claims 1 to 8.
10. The lithium metal battery according to claim 9, characterized in that, The lithium metal battery includes a lithium metal anode material.