Stable double-interface electrolyte and preparation method thereof

Abstract

The invention relates to the technical field of lithium metal batteries, in particular to a stable double-interface electrolyte and a preparation method thereof. The stable double-interface electrolyte is prepared by uniformly mixing a lithium salt, an organic solvent and a fluorine-containing silicon-based additive and then standing, the mass percent of the fluorine-containing silicon-based additive in the electrolyte is 1-5%; the fluorine-containing silicon-based additive is a compound with a structure shown as a formula (I); wherein X represents a trimethylsilyl group, and R represents an alkyl group with 1-4 carbon atoms; the Li < + > transference number of the stable double-interface electrolyte at 25 DEG C is greater than 0.65. According to the invention, the contradiction that a conventional additive is difficult to give consideration to improvement of ion transmission and interface stabilization of the lithium metal battery is solved, the problem of electrode polarization caused by low Li < + > transference number of a traditional electrolyte is solved, a firm SEI and CEI composite interface layer is constructed, and the cycling stability and safety of the battery are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery technology, specifically to a stable dual-interface electrolyte and its preparation method. This stable dual-interface electrolyte can simultaneously stabilize the high-voltage positive electrode interface and the lithium metal negative electrode interface of a lithium metal battery system. Background Technology

[0002] Lithium metal anodes are considered the ultimate anode material for realizing next-generation high-energy-density batteries due to their extremely high theoretical capacity and lowest electrochemical potential. When matched with high-capacity, high-operating-voltage, high-nickel ternary cathodes, this system is expected to break through the current energy density bottleneck of lithium-ion batteries. However, the commercial application of lithium metal batteries is constrained by the severe instability problem at both electrode interfaces. On the anode side, the high reactivity of lithium metal with the electrolyte leads to the continuous growth of an uneven and unstable solid electrolyte interphase (SEI) film, accompanied by electrolyte consumption and lithium dendrite growth, posing safety risks. On the cathode side, high-nickel materials are prone to structural degradation and CEI interface side reactions under high voltage, and the oxidative decomposition and trace acid erosion of conventional electrolytes further exacerbate the degradation of the cycle performance of lithium metal batteries.

[0003] In-depth analysis reveals that the exacerbation of these interfacial side reactions is closely related to severe electrode polarization within the battery. One significant source of this polarization is the excessively low lithium-ion transference number (LTUN) in conventional electrolytes. In conventional electrolytes, the LTUN is typically below 0.4, meaning that over 60% of the current is contributed by anion migration. During battery operation, anions rapidly accumulate near the electrodes, forming a space charge layer, leading to severe concentration polarization. This polarization not only limits the battery's rate performance but also forces it to operate at higher overpotentials: on the lithium metal anode side, the high overpotential directly accelerates lithium dendrite growth; on the cathode side, it exacerbates the oxidative decomposition of the electrolyte at high potentials. Therefore, increasing the LTUN is crucial for mitigating polarization, achieving efficient and stable ion transport, and simultaneously improving the stability of the positive and negative electrode interfaces.

[0004] Currently, researchers have developed various electrolyte engineering strategies to address these challenges, but all have significant limitations. High-concentration electrolytes can construct stable SEIs by forming anion-dominated solvation structures, effectively suppressing dendrites. While their ionic conductivity and viscosity have been widely discussed, the substantial improvement in lithium-ion transference number is limited, and their inherent high viscosity, high cost, and poor wettability restrict practical application. Locally high-concentration electrolytes and weakly solvated electrolytes, while improving physicochemical properties to some extent or achieving solvation-like structures at conventional concentrations, face problems such as decreased ionic conductivity and high desolvation energy barriers, respectively. In particular, the lithium-ion transference number remains low, failing to fundamentally solve the problem of synergistic rapid ion transport and interface stability in lithium metal batteries. Solid-state electrolytes, considered the ultimate solution, can fundamentally prevent dendrite penetration, but technical bottlenecks such as low room-temperature ionic conductivity and high solid-solid interface contact impedance have not yet been fully overcome.

[0005] Existing technologies primarily focus on modifying and stabilizing the single electrode interface of lithium metal batteries. For example, patents such as CN118572193A, CN116864809A, and CN116435594A protect the positive electrode with fluorinated solvents and optimize the SEI (Sediment Interchange) of the negative electrode using additives. However, these solutions fall short in simultaneously achieving effective protection of both the high-voltage positive electrode interface and the highly active lithium metal negative electrode interface, especially in terms of validation under extreme conditions. The difficulty in balancing ionic conductivity, interface stability, and overall practical feasibility reveals a significant bottleneck in the current electrolyte system design.

[0006] The extremely high chemical reactivity of lithium metal anodes makes their SEI interface polarization problem far more severe than that of graphite anodes in lithium-ion batteries. For example, the silicon-containing additive electrolyte scheme disclosed in CN109659611A can achieve some effect in lithium-ion batteries (graphite anodes), but its mechanism of action and efficiency are entirely based on the graphite system design. If it is directly applied to lithium metal batteries, it will not only fail to solve the unique, dynamic, and severe SEI interface failure problem of lithium metal, but will also exacerbate electrode polarization due to poor SEI interface compatibility. This will result in a battery capacity retention rate far lower than its existing level in lithium-ion batteries (e.g., lower than 94% of CN109659611A), leading to a performance degradation of lithium-ion batteries.

[0007] Therefore, breaking away from existing approaches that limit themselves to single-interface modifications or macroscopic formulation adjustments, and designing a multifunctional additive that combines weak coordination properties with excellent film-forming ability from the perspective of molecular electronic structure is a key problem urgently needing to be solved in this field. Ideally, the molecule should be able to actively participate in Li... +The solvation of lithium ions reduces the binding of solvent molecules through weak coordination, creating an anion-rich coordination environment that fundamentally increases the lithium ion transference number. Simultaneously, its decomposition products can synergistically construct a robust protective layer at the positive and negative electrode interfaces. However, how to precisely integrate strong electron-donating and electron-withdrawing groups within the same molecule to achieve a balance between weak coordination and high interfacial activity through stereoelectronic effects has not been publicly reported, and no readily available molecules are available for selection. Summary of the Invention

[0008] This invention provides a stable dual-interface electrolyte and its preparation method. The stable dual-interface electrolyte possesses a primary solvation sheath structure, improving the electrolyte performance of lithium metal batteries. + It improves transmission efficiency and solves the technical problem of dual-interface stability between the high-voltage positive electrode CEI and the highly active lithium metal negative electrode SEI in lithium metal batteries.

[0009] The first objective of this invention is to provide a stable dual-interface electrolyte for lithium metal batteries.

[0010] The stable dual-interface electrolyte is prepared by mixing lithium salt, organic solvent and fluorine-containing silicon-based additive and then allowing it to stand until the solvation reaction is complete. The fluorinated silicon-based additive constitutes 1-5% by mass in the stable dual-interface electrolyte; the fluorinated silicon-based additive is a compound with the structure shown in formula (I) below: (I); Wherein, X represents trimethylsilyl and R represents an alkyl group having 1 to 4 carbon atoms; The stable dual-interface electrolyte at 25°C, Li + Migration number > 0.65.

[0011] Preferably, in the stable dual-interface electrolyte of the present invention, the fluorinated silicon-based additive is DTAE; DTAE is ethyl 2,2-difluoro-2-(trimethylsilyl)ethyl acetate.

[0012] Preferably, in the stable dual-interface electrolyte of the present invention, the amount of DTAE added is 2 wt% of the mass of the stable dual-interface electrolyte.

[0013] Preferably, in the stable dual-interface electrolyte of the present invention, the organic solvent is a carbonate electrolyte.

[0014] Preferably, in the stable dual-interface electrolyte of the present invention, the carbonate electrolyte is prepared by mixing ethylene carbonate and diethyl carbonate in a volume ratio of (0.5-2):1. More preferably, the volume ratio of ethylene carbonate to diethyl carbonate is 1:1.

[0015] Preferably, in the stable dual-interface electrolyte of the present invention, the lithium salt is LiPF6; its concentration in the lithium metal battery electrolyte is 1M.

[0016] Preferably, in the stable dual-interface electrolyte of the present invention, the standing temperature is 25-30°C, and the standing solvation reaction time is 2-3 hours.

[0017] Preferably, the stable dual-interface electrolyte of the present invention, at 25°C, Li + The migration rate is 0.72.

[0018] A second objective of this invention is to provide a method for preparing the aforementioned stable dual-interface electrolyte, comprising the following steps: S1: Mix the fluorinated silicon-based additive, lithium salt, and organic solvent evenly to obtain a mixed solution; S2: Let the mixed solution stand until the solvation reaction is complete to obtain a stable dual-interface electrolyte.

[0019] Preferably, in the preparation method of the present invention, the standing temperature is 25-30°C; at this temperature, the time for the solvation reaction to end is usually not less than 2 hours; preferably 3 hours.

[0020] A third objective of this invention is to provide a lithium metal battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the aforementioned stable dual-interface electrolyte or a dual-interface electrolyte prepared by the aforementioned preparation method.

[0021] Preferably, in the lithium metal battery of the present invention, the positive electrode comprises a high-nickel layered oxide positive electrode active material; preferably, the positive electrode is NCM811; and the negative electrode is lithium metal.

[0022] This study proposes a novel dual-interface electrolyte additive with synergistic intramolecular electronic effects. This additive molecule simultaneously introduces both strong electron-donating and strong electron-withdrawing functional groups, utilizing their synergistic effect in spatial and electronic structure to significantly influence lithium-ion coordination ability. Thanks to this unique electronic effect, the additive molecule can participate in Li-ion coordination via its coordinating functional groups through weak interactions. + Reconstruction of the primary solvated sheath effectively replaces some solvent molecules and significantly reduces Li + The energy barrier to be overcome in the desolvation process. During the operation of lithium metal batteries, this additive exhibits distinct interfacial selectivity: on the negative electrode side, it preferentially undergoes reduction decomposition, where its fluorine and silicon-containing components synergistically construct a thin and dense solid electrolyte interface layer rich in inorganic and silicon-oxygen components, effectively inhibiting lithium dendrite growth and mitigating electrolyte side reactions; on the positive electrode side, it preferentially undergoes oxidation reaction, where its silicon-containing functional groups have the ability to remove corrosive impurities in the electrolyte, while the fluorine-containing components participate in the formation of a stable positive electrode electrolyte interface layer, significantly mitigating the structural degradation of high-nickel positive electrode materials and the dissolution of transition metals.

[0023] The beneficial effects of this invention are: 1. The fluorinated silicon-based additive in the electrolyte of this invention has a specific structure. Its strong electron-donating silicon group and strong electron-withdrawing fluorine group at the same carbon site generate a unique stereoelectronic interaction. After being blended with lithium salt and organic solution and subjected to a static solvation reaction, it actively participates in and reconstructs Li. + The primary solvation sheath structure can reduce Li + Migration resistance significantly improves ion transport efficiency, Li + The migration count can be as high as 0.72.

[0024] 2. The stable dual-interface electrolyte of this invention forms a dense protective layer CEI on the surface of the positive electrode residue through the preferential oxidation and decomposition of fluorosilicone-based additives, which significantly enhances the high-voltage stability of the system, and its oxidation window can reach 4.8 V; 3. The present invention stabilizes the dual-interface electrolyte, which preferentially participates in the formation of SEI and CEI, thereby improving the dual-interface stability of lithium metal batteries and simultaneously improving the cycle performance of lithium metal batteries under high voltage and high temperature. Attached Figure Description

[0025] Figure 1 The Raman spectra of the stable dual-interface electrolyte and the reference electrolyte in Example 1 of this invention are shown. Figure 2 To stabilize the dual-interface electrolyte and the reference electrolyte in Embodiment 1 of the present invention 7 LiNMR spectrum; Figure 3 Linear sweep voltammetric curves of a stable dual-interface electrolyte and a reference electrolyte in Example 1 of this invention; Figure 4 The figures are chronoampere and AC impedance diagrams of a symmetrical battery in Embodiment 1 of the present invention; wherein, a is the chronoampere curve and AC impedance spectrum before and after polarization of a stable dual-interface electrolyte (inset), and b is the chronoampere curve and AC impedance spectrum before and after polarization of a reference electrolyte (inset). Figure 5 The image shows the SEI (Series Electron Microscope) morphology of lithium metal surface in Example 1 of the present invention; wherein, a is the SEI scanning electron microscope image of lithium metal surface of stable dual-interface electrolyte, and b is the SEI scanning electron microscope image of lithium metal surface of reference electrolyte. Figure 6 The images shown are scanning electron microscope (SEM) images of the NCM811 surface CEI of Embodiment 1 of the present invention; wherein, a is a scanning electron microscope image of the NCM811 cathode surface CEI of the stable dual-interface electrolyte, and b is a scanning electron microscope image of the NCM811 cathode surface CEI of the reference electrolyte. Figure 7 This is a comparison chart of the cycling performance of the Li||NCM811 battery in Example 1 of the present invention at 4.3V and 25℃. Figure 8 This is a comparison chart of the cycling performance of the Li||NCM811 battery in Example 1 of the present invention at 4.6V and 25℃. Figure 9 This is a comparison chart of the cycling performance of the Li||NCM811 battery in Example 1 of the present invention at 4.5V and 60℃. Detailed Implementation

[0026] A stable dual-interface electrolyte for lithium metal batteries is prepared by mixing lithium salt, organic solvent and fluorine-containing silicon-based additive and then allowing it to stand until the solvation reaction is completed. The fluorinated silicon-based additive constitutes 1-5% by mass in the stable dual-interface electrolyte; the fluorinated additive is a compound with the structure shown in formula (I) below: (I); Where X represents trimethylsilyl, R represents an alkyl group with 1 to 4 carbon atoms, and n represents a natural number 1 to 4; The stable dual-interface electrolyte at 25°C, Li + Migration number > 0.65.

[0027] In some instances, the fluorinated silicon-based additive is DTAE; DTAE represents compound 2,2-difluoro-2-(trimethylsilyl)ethyl acetate.

[0028] In some instances, the amount of DTAE added is 2 wt% of the mass of the stable dual-interface electrolyte.

[0029] In some instances, the organic solvent is a carbonate electrolyte.

[0030] In some instances, the carbonate electrolyte is a mixture of ethylene carbonate and diethyl carbonate in a volume ratio of (0.5–2):1.

[0031] In some instances, the lithium salt is LiPF6; its concentration in the lithium metal battery electrolyte is 1M.

[0032] In some instances, the settling temperature is 25–30°C, and the settling time for the solvation reaction to end is 2–3 hours.

[0033] In some instances, Li at 25°C + The migration rate is 0.72.

[0034] The preparation method of the above-mentioned stable two-interface electrolyte includes the following steps: S1: Mix the fluorinated silicon-based additive, lithium salt and organic solution evenly to obtain a mixture; S2: Let the mixture stand until the solvation reaction is complete to obtain; In some instances, the settling temperature is 25–30°C, and the settling time until the solvation reaction is complete is preferably 3 hours.

[0035] The stable dual-interface electrolyte of the present invention is used as an electrolyte in lithium metal batteries.

[0036] In some instances, Li||Li symmetric cells assembled with a stable dual-interface electrolyte were used, and after cycling, a protective SEI layer was formed between the Li anode and the electrolyte, and the Li anode surface exhibited a dense and flat morphology.

[0037] In some instances, the positive electrode of a lithium metal secondary battery is NCM811, which is a high-nickel layered oxide positive electrode active material.

[0038] In some instances, Li||NCM811 batteries assembled using stable lithium metal battery dual-interface electrolytes form a uniform and stable protective CEI on the NCM811 cathode surface after cycling.

[0039] The specific embodiments of the present invention will be further described below with reference to specific examples, but the present invention is not limited to the scope of the embodiments described herein.

[0040] The raw materials used in the following examples are: ethyl 2,2-difluoro-2-(trimethylsilyl)ethyl acetate (DTAE), ethylene carbonate (EC), diethyl carbonate (DEC), and lithium hexafluorophosphate (LiPF6).

[0041] Example 1

[0042] This embodiment provides a method for preparing a stable dual-interface electrolyte, including the following steps: 1. Add LiPF6 to an EC / DEC solution with a volume ratio of 1:1 to obtain a carbonate electrolyte with a LiPF6 concentration of 1M; 2. Add 2 wt% of DTAE to 1 mL of carbonate electrolyte to obtain a mixed solution; 3. Let the mixed solution stand at 25°C for 2 hours to obtain a stable dual-interface electrolyte.

[0043] Example 2

[0044] This embodiment prepares a stable dual-interface electrolyte according to the steps of Example 1, with the only difference being that 3 wt% of DTAE is added to the carbonate electrolyte.

[0045] Example 3

[0046] This embodiment prepares a stable dual-interface electrolyte according to the steps of Example 1, with the only difference being that 4 wt% of DTAE is added to the carbonate electrolyte.

[0047] Example 4

[0048] This embodiment prepares a stable dual-interface electrolyte according to the steps of Example 1, with the only difference being that 5 wt% of DTAE is added to the carbonate electrolyte.

[0049] Example 5

[0050] This embodiment prepares a stable dual-interface electrolyte according to the steps of Example 1, with the only difference being that 1 wt% of DTAE is added to the carbonate electrolyte.

[0051] The stable two-interface electrolyte prepared in Example 1 was characterized below using the carbonate electrolyte of Example 1 as a reference electrolyte: I. Raman Spectroscopy Test Raman spectroscopy was performed on the stable dual-interface electrolyte of Example 1 and the reference electrolyte. The resulting Raman spectra are shown below. Figure 1 As shown.

[0052] From the appendix Figure 1 As can be seen, compared with the reference electrolyte, the stable two-interface electrolyte is located at 700-750 cm⁻¹. -1 The signal representing contact ion pairs (CIPs) and aggregates (AGGs) within the range was enhanced, while the signal representing solvent-separated ion pairs (SSIPs) was significantly weakened, indicating that the addition of DTAE promoted PF6. - Anions enter Li + The primary solvation sheath leads to a transformation of the solvation structure towards anion-rich coordination.

[0053] II. Nuclear Magnetic Resonance Spectroscopy (NMR) Testing

[0054] Nuclear magnetic resonance spectroscopy was performed on the stable dual-interface electrolyte of Example 1 and the reference electrolyte, and the results were obtained. 7 LiNMR spectrum as shown Figure 2 As shown.

[0055] From the appendix Figure 2 It is evident that, compared to the reference electrolyte, the stable dual-interface electrolyte... 7 The LiNMR signal clearly shifts towards the lower field, indicating that DTAE and Li + Weak coordination occurs, altering Li + The coordination environment.

[0056] III. Linear Scan Voltmeter Curve Test

[0057] Linear sweep voltammetry was performed on the stable dual-interface electrolyte of Example 1 and the reference electrolyte. The results of the linear sweep voltammetry are as follows: Figure 3 As shown.

[0058] From the appendix Figure 3 It can be seen that the oxidation window using the stable dual-interface electrolyte is 4.8V, while the reference electrolyte begins to undergo significant oxidative decomposition at 4.1V. This indicates that the addition of DTAE to the reference electrolyte significantly improves the electrolyte's antioxidant capacity at high voltages.

[0059] IV. Ion transport number

[0060] Li||Li symmetric cells were prepared using the stable dual-interface electrolyte from Example 1 and a reference electrolyte, respectively. The chronoampere and AC impedance of the symmetric cells were measured at 25°C and a polarization voltage of 10 mV. The results are as follows: Figure 4 As shown; where a is the chronoamperometry curve and AC impedance spectrum before and after polarization of the stable two-interface electrolyte (inset), and b is the chronoamperometry curve and AC impedance spectrum before and after polarization of the reference electrolyte (inset).

[0061] From the appendix Figure 4 As can be seen, the ion transference number using the stable dual-interface electrolyte is 0.72, while the ion transference number of the reference electrolyte is only 0.48; this is due to the difference between DTAE and Li. + The low binding energy of Li weakens its binding properties. + The overall binding strength with the solvent makes Li + They are more easily desolvated and migrated under the influence of an electric field.

[0062] V. SEI morphology of lithium metal surface

[0063] Li||Li symmetric cells were prepared using the stable dual-interface electrolyte from Example 1 and the reference electrolyte, respectively, at 25°C and 1 mA cm⁻¹. -2 The scanning electron microscope image of the lithium metal surface after 50 cycles is shown in the attached image. Figure 5 As shown; where a is a scanning electron microscope (SEM) image of the SEI on the lithium metal surface of a stable dual-interface electrolyte, and b is a scanning electron microscope (SEM) image of the SEI on the lithium metal surface of a reference electrolyte.

[0064] From the appendix Figure 5 It is evident that the lithium metal interface deposited using a stable dual-interface electrolyte is dense and flat, exhibiting a regular blocky morphology, while the lithium metal surface deposited using a reference electrolyte is thick and loosely porous; this indicates that the addition of DTAE suppresses unfavorable side reactions on the lithium metal surface.

[0065] VI. CEI morphology of NCM811 cathode surface

[0066] Li||NCM811 batteries were prepared using the stable dual-interface electrolyte from Example 1 and the reference electrolyte, respectively. After 100 cycles at 4.3 V (2.8-4.3 V), 1C, and 25°C, the CEI scanning electron microscope images of the NCM811 cathode surface are attached. Figure 6 As shown; where a is a scanning electron microscope image of the CEI on the cathode surface of the stable dual-interface electrolyte NCM811, and b is a scanning electron microscope image of the CEI on the cathode surface of the reference electrolyte NCM811.

[0067] From the appendix Figure 6 It is evident that the NCM811 particles using the stable dual-interface electrolyte remained intact without cracks, while the NCM811 particles using the reference electrolyte were severely fractured. This indicates that the addition of DTAE formed a stable CEI, protecting the structural integrity of the NCM811 cathode particles.

[0068] VII. Atmospheric Pressure and Room Temperature Cyclic Performance Test

[0069] Li||NCM811 batteries were prepared using the stable dual-interface electrolyte from Example 1 and the reference electrolyte, respectively. Cyclic performance was tested under the following conditions: cutoff voltage 4.3 V (2.8-4.3 V), 1C, and 25℃. The resulting comparison of cycle performance is shown in the attached figure. Figure 7 As shown.

[0070] From the appendix Figure 7 It is evident that the Li||NCM811 battery using a stable dual-interface electrolyte can cycle stably for more than 400 cycles, with a capacity retention of 82.65% after 490 cycles; conversely, the Li||NCM811 battery using a reference electrolyte exhibits rapid degradation in cycling performance, with a capacity retention of only 80.17% after 163 cycles.

[0071] 8. High-pressure room temperature cycling performance test

[0072] Li||NCM811 batteries were prepared using the stable dual-interface electrolyte from Example 1 and the reference electrolyte, respectively. Cyclic performance was tested under the following conditions: cutoff voltage 4.6 V (2.8-4.6 V), 1C, and 25°C. The resulting comparison of cycle performance is shown in the attached figure. Figure 8 As shown.

[0073] From the appendix Figure 8 It can be seen that the Li||NCM811 battery using a stable dual-interface electrolyte can retain 82.91% of its capacity after 330 cycles; in contrast, the Li||NCM811 battery using a reference electrolyte exhibits rapid degradation in cycling performance, with a capacity retention of only 80.84% ​​after 66 cycles.

[0074] IX. High-pressure and high-temperature cycling performance test

[0075] Li||NCM811 batteries were prepared using the stable dual-interface electrolyte from Example 1 and the reference electrolyte, respectively. Cyclic performance was tested under the following conditions: cutoff voltage 4.5 V (2.8-4.5 V), 1C, and 60℃. The resulting comparison of cycle performance is shown in the attached figure. Figure 9 As shown.

[0076] From the appendix Figure 9 It is evident that the Li||NCM811 battery using a stable dual-interface electrolyte can maintain a capacity retention of 82.32% after 250 cycles; conversely, the Li||NCM811 battery using a reference electrolyte exhibits rapid degradation in cycling performance, with a capacity retention of only 77.83% after 90 cycles.

[0077] The characterization results above demonstrate that ethyl 2,2-difluoro-2-(trimethylsilyl)ethyl acetate possesses a primary solvation sheath structure in the electrolyte through "weak coordination," which can significantly enhance the ion transport capability of lithium metal batteries and the stability of the SEI and CEI dual interfaces.

Claims

1. A stable dual-interface electrolyte for lithium metal batteries, characterized in that, The stable dual-interface electrolyte is prepared by mixing lithium salt, organic solvent and fluorine-containing silicon-based additive and then allowing it to stand until the solvation reaction is complete. The fluorinated silicon-based additive is present in the stable dual-interface electrolyte at a mass percentage of 1–5%; the fluorinated additive is a compound with the structure shown in formula (I) below: (I)； Where X represents trimethylsilyl, R represents an alkyl group with 1 to 4 carbon atoms, and n represents a natural number 1 to 4; The stable dual-interface electrolyte at 25°C, Li + Migration number > 0.

65.

2. The stable dual-interface electrolyte according to claim 1, characterized in that: The fluorinated silicon-based additive is ethyl 2,2-difluoro-2-(trimethylsilyl)ethyl acetate (DTAE).

3. The stable dual-interface electrolyte according to claim 2, characterized in that: The amount of DTAE added is 2 wt% of the mass of the stable dual-interface electrolyte.

4. The stable dual-interface electrolyte according to claim 1, characterized in that: The organic solvent is a carbonate electrolyte.

5. The stable dual-interface electrolyte according to claim 4, characterized in that: The carbonate electrolyte is composed of ethylene carbonate and diethyl carbonate mixed in a volume ratio of (0.5-2):

1.

6. The stable dual-interface electrolyte according to claim 1, characterized in that: The lithium salt is LiPF6; its concentration in the lithium metal battery electrolyte is 1M.

7. The stable dual-interface electrolyte according to claim 1, characterized in that, The settling temperature is 25–30°C, and the settling time until the solvation reaction is complete is 2–3 hours.

8. The stable dual-interface electrolyte according to claim 1, characterized in that, Li at 25℃ + The migration rate is 0.

72.

9. A lithium metal battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, characterized in that: The electrolyte is the stable dual-interface electrolyte according to any one of claims 1-8.

10. The lithium metal battery according to claim 9, characterized in that, The positive electrode comprises a high-nickel layered oxide positive electrode active material.

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