High-voltage lithium metal battery electrolyte and preparation method thereof

Abstract

The invention discloses a high-voltage lithium metal battery electrolyte and a preparation method thereof. The high-voltage lithium metal battery electrolyte comprises a solvent, a lithium salt and an additive, wherein the solvent comprises a sulfone solvent and a carbonic ester solvent. By optimizing the coordination effect of the solvent system, the lithium salt and the functional additive, stable SEI and CEI films can be formed, so that the stability of the electrolyte under high voltage and the compatibility of the electrolyte to a lithium metal negative electrode are realized, meanwhile, the flame retardant property and the stability of the electrolyte are improved, and when the electrolyte is used for a lithium metal battery, the service life of the electrolyte is prolonged. The stability and the cycle performance of the lithium metal battery can be obviously improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium metal battery electrolyte preparation. Specifically, the present invention relates to a high-voltage lithium metal battery electrolyte and a preparation method thereof. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in various electronic devices due to their high energy density and long cycle life. However, with the growing demand for rechargeable portable devices and electric vehicles, people have shown greater expectations for the development of high energy density rechargeable batteries. However, based on graphite anode and layered Li[Ni x Co y M 1-x-y ]The commercial lithium-ion battery with O2 (M=Mn / Al) positive electrode has a maximum energy density of only 300Wh / kg due to its theoretical capacity limitation.

[0003] Compared to lithium-ion batteries (LIBs), lithium metal batteries (LMBs) with lithium metal (Li) as the negative electrode have begun to attract widespread attention due to their high theoretical capacity (3860mAh / g) and lowest reduction potential (-3.04V vs. standard hydrogen electrode). In addition, lithium is the lightest element in the periodic table with a density of only 0.534g / cm 3 , which can significantly reduce battery weight. Therefore, high-voltage lithium metal batteries are one of the most promising technologies for achieving ultra-high energy density. For example, a lithium metal battery using a lithium metal anode and a high-voltage / high-capacity nickel-cobalt-manganese oxide NCM811 cathode has the potential to reach 500Wh / kg. In addition to range, battery safety and cycle life are also crucial performance parameters.

[0004] Although high-voltage lithium metal batteries have advantages such as high energy density, they still face the following problems in practical applications: (1) Lithium dendrites and short-circuit risks: During the charge and discharge process, lithium dendrites are easily formed on the surface of the lithium metal negative electrode. The dendrites may penetrate the diaphragm and cause a short circuit, leading to thermal runaway or even explosion; (2) Electrolyte and interface stability issues: Under high-voltage conditions, liquid electrolytes are easily decomposed, resulting in uneven or ruptured SEI films, exacerbating side reactions and lithium dendrite growth; (3) Positive electrode material decomposition under high pressure: Under high pressure, positive electrode materials (such as high-nickel ternary materials) may precipitate lattice oxygen, exacerbating electrolyte oxidation and decomposition, and shortening battery life. In summary, the electrolyte affects and participates in the above-mentioned side reactions, determining whether the lithium metal battery can operate safely and stably. Therefore, it is crucial to invent an electrolyte that can simultaneously stabilize the negative electrode interface (SEI) and the positive electrode interface (CEI) under high voltage. Summary of the Invention

[0005] The present invention is based on the inventor's discovery and understanding of the following facts and problems: carbonate solvents commonly used in lithium metal batteries are prone to oxidative decomposition under high pressure and are difficult to form a stable solid electrolyte interface (SEI), resulting in low lithium metal deposition / stripping efficiency, poor coulombic efficiency, and lithium dendrite growth that may pierce the diaphragm, causing short circuit risks; ether solvents are friendly to lithium negative electrodes but have poor antioxidant capacity, and ether-based electrolytes are not suitable for high voltage (>4V vs. Li / Li + ) is easily oxidized and decomposed under high temperature, and the cathode material surface interface (CEI) cannot be stabilized, resulting in capacity decay and decreased cycle performance; these challenges can be partially solved by adding a large amount of lithium salt, but the viscosity of high-concentration electrolyte increases significantly, reducing lithium ion conductivity, thereby affecting battery rate performance. In addition, high-concentration electrolyte is expensive due to the addition of a large amount of lithium salt, and may aggravate side reactions, reducing the overall economy and practicality of the battery. Based on this, the present invention aims to develop a new type of lithium metal battery electrolyte to solve the problems existing in the actual use of current high-voltage lithium metal battery electrolytes.

[0006] In a first aspect, an embodiment of the present invention provides a high-voltage lithium metal battery electrolyte, comprising a solvent, a lithium salt, and an additive; wherein the solvent comprises a sulfone solvent and a carbonate solvent.

[0007] In some embodiments, the high-voltage lithium metal battery electrolyte includes 70% to 90% solvent, 8% to 18% lithium salt and 2% to 12% additives, calculated by mass percentage.

[0008] In some embodiments, in the solvent, the volume ratio of the sulfone solvent to the carbonate solvent is (60% to 90%): (40% to 10%);

[0009] Optionally, the sulfone solvent includes at least one of sulfolane, dimethyl sulfone, and methyl ethyl sulfone;

[0010] Optionally, the carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0011] In some embodiments, the lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and lithium hexafluorophosphate.

[0012] In some embodiments, the additive comprises a mixture of a positive electrode protection additive, a positive electrode film-forming additive, and a negative electrode film-forming additive;

[0013] Optionally, in the high-voltage lithium metal battery electrolyte, the mass concentration of the positive electrode protection additive is 0.2wt% to 2wt%, the mass concentration of the positive electrode film-forming additive is 0.9wt% to 5wt%, and the mass concentration of the negative electrode film-forming additive is 0.9wt% to 5wt%.

[0014] In some embodiments, the positive electrode protective additive comprises at least one of adiponitrile, succinonitrile, ethanetristnitrile.

[0015] In some embodiments, the positive electrode film-forming additive comprises at least one of lithium difluoro(oxalato)borate, tris(2,2,2-trifluoroethyl) borate.

[0016] In some embodiments, the negative electrode film-forming additive comprises at least one of fluoroethylene carbonate, difluoroethylene carbonate, lithium difluorophosphate.

[0017] In the second aspect, the embodiments of the present application further provide a preparation method of the high-voltage lithium metal battery electrolyte according to the first aspect, comprising the following steps:

[0018] After mixing the sulfone solvent and the carbonate solvent, the lithium salt is added and stirred to dissolve, and finally the additive is added and stirred to mix, so that the high-voltage lithium metal battery electrolyte is obtained.

[0019] In the third aspect, the embodiments of the present application further provide a lithium metal battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and the high-voltage lithium metal battery electrolyte according to the first aspect.

[0020] The embodiments of the present application have the following advantages and beneficial effects:

[0021] The embodiments of the present application use sulfone with high oxidation stability as the main solvent, and add carbonate with low viscosity to form a cosolvent with the main solvent, so that the electrolyte can have high stability and low viscosity. In addition, the embodiments of the present application add positive electrode protective additives, positive electrode film-forming additives and negative electrode film-forming additives, which have a synergistic effect on the stability of the electrolyte. When they are applied to lithium metal batteries, the stability and cycle performance of the lithium metal batteries can be significantly improved. DETAILED DESCRIPTION

[0022] To make the objectives, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the described embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort belong to the protection scope of the present application.

[0023] Unless otherwise defined, the technical terms or scientific terms used in the present application shall have the usual meanings understood by those of ordinary skill in the art to which the present application belongs.

[0024] Where values ​​are described herein as ranges, it should be understood that such disclosure includes disclosure of all possible sub-ranges within that range, as well as specific values ​​falling within that range, regardless of whether a specific value or sub-range is explicitly stated.

[0025] As used herein, the words "comprise," "include," and "includes" and variations thereof mean that additional elements or integers may be included although permitted but not specifically described.

[0026] In a first aspect, an embodiment of the present invention provides a high-voltage lithium metal battery electrolyte, comprising a solvent, a lithium salt, and an additive; wherein the solvent comprises a sulfone solvent and a carbonate solvent.

[0027] In some embodiments, the high-voltage lithium metal battery electrolyte includes 70% to 90% solvent, 8% to 18% lithium salt and 2% to 12% additives, calculated by mass percentage.

[0028] In some embodiments, in the solvent, the volume ratio of the sulfone solvent to the carbonate solvent is (60% to 90%): (40% to 10%); the inventors have found through research that if the amount of sulfone solvent added is too high, it will lead to high viscosity of the solution, which will significantly increase the migration resistance of lithium ions between electrodes, hinder the diffusion of lithium ions, and thus reduce the rate performance of lithium metal batteries; it will also make it difficult for the electrolyte to fully penetrate the electrode micropores and diaphragms, forming local "dead zones", and the unevenness of the interfacial reaction will lead to the peeling of active materials and structural collapse, shortening the cycle life of the battery; but if the amount of sulfone solvent added is too little, the co-solvent formed by the sulfone solvent and the carbonate solvent will have insufficient high-pressure resistance, and side reactions such as solvent decomposition will occur during the high-pressure cycle, which will greatly reduce the cycle performance of the lithium metal battery. Therefore, it is advantageous to control the amount of sulfone solvent added in the embodiment of the present invention within the above range;

[0029] Optionally, the sulfone solvent includes at least one of sulfolane, dimethyl sulfone, and methyl ethyl sulfone;

[0030] Optionally, the carbonate solvent includes at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0031] The present invention uses a sulfone solvent with high oxidative stability as the primary solvent. Sulfone solvents have high voltage tolerance, with their oxidative decomposition voltage generally exceeding 5.5V, thereby improving the electrolyte's high-voltage resistance. Their high boiling point and non-flammability significantly reduce the risk of thermal runaway in lithium metal batteries. However, due to the high viscosity of sulfone solvents, the present invention also incorporates a carbonate solvent as a secondary solvent to reduce electrolyte viscosity and prevent lithium ion transport.

[0032] In some embodiments, the lithium salt includes at least one of lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethylsulfonyl)imide (LiTFSI), and lithium hexafluorophosphate (LiPF6).

[0033] In some embodiments, the additive comprises a mixture of a positive electrode protection additive, a positive electrode film-forming additive, and a negative electrode film-forming additive;

[0034] Optionally, in the high-voltage lithium metal battery electrolyte, the mass concentration of the positive electrode protection additive is 0.2wt% to 2wt%, the mass concentration of the positive electrode film-forming additive is 0.9wt% to 5wt%, and the mass concentration of the negative electrode film-forming additive is 0.9wt% to 5wt%.

[0035] In some embodiments, the positive electrode protective additive includes at least one of adiponitrile, succinonitrile, and ethanetrinitrile. In embodiments of the present invention, the above-mentioned nitrile compounds are selected as positive electrode protective additives, which can form complexes with the positive electrode metal to prevent metal ion dissolution, thereby stabilizing the positive electrode.

[0036] In some embodiments, the cathode film-forming additive includes at least one of lithium difluorooxalatoborate (LiDFOB) and tris(2,2,2-trifluoroethyl) borate (TTFEB). These substances are selected as cathode film-forming additives in embodiments of the present invention. These additives can form an inorganic CEI film (such as LiF and LiBO2) rich in boron and fluorine at the cathode to withstand high voltages.

[0037] In some embodiments, the negative electrode film-forming additive includes at least one of fluoroethylene carbonate (FEC), bisfluoroethylene carbonate (DFEC), and lithium difluorophosphate (LiPO2F2). These materials are selected as negative electrode film-forming additives in embodiments of the present invention. These additives can form an inorganic LiF-rich SEI film at the negative electrode, preventing the electrolyte from decomposing on the surface of the lithium metal negative electrode and improving battery stability.

[0038] In a second aspect, an embodiment of the present invention further provides a method for preparing a high-voltage lithium metal battery electrolyte as described in the first aspect, comprising the following steps:

[0039] After mixing a sulfone solvent and a carbonate solvent, lithium salt is added and stirred to dissolve, and finally additives are added and stirred to obtain the high-voltage lithium metal battery electrolyte.

[0040] In a third aspect, an embodiment of the present invention further proposes a lithium metal battery, comprising a positive electrode sheet, a negative electrode sheet, a separator, and the high-voltage lithium metal battery electrolyte described in the first aspect.

[0041] In some embodiments, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.

[0042] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0043] The positive electrode film layer includes a positive electrode active material, which can be selected from materials capable of absorbing and releasing lithium.

[0044] The specific type of positive electrode active material is not subject to specific restrictions and can be selected according to needs. As an example, the positive electrode active material may include but is not limited to lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium cobalt phosphate (LiCoPO4), iron pyrophosphate (Li2FeP2O7), lithium cobalt oxide (LiCoO2), spinel lithium manganese oxide (LiMn2O4), spinel nickel lithium manganese oxide (LiNi 0.5 Mn 1.5 O4), layered lithium manganese oxide (LiMnO2), lithium nickel oxide (LiNiO2), lithium niobate (LiNbO2), lithium ferrite (LiFeO2), ternary materials (such as lithium nickel cobalt manganese oxide NCM), etc. These materials can be used alone or in combination of two or more.

[0045] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0046] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0047] In some embodiments, the positive electrode film layer may further include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0048] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0049] It should be noted that the negative electrode sheet in the above-mentioned lithium metal battery is not subject to special restrictions, and those skilled in the art can select it according to actual needs, for example, using a negative electrode sheet made by rolling lithium foil on a copper substrate.

[0050] It should also be noted that the embodiments of the present invention have no particular restrictions on the type of diaphragm, and any known porous structure diaphragm with good chemical stability and mechanical stability can be selected.

[0051] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0052] The following are non-limiting examples and comparative examples of the present invention. It should be noted that the comparative examples are not prior art and are provided solely for comparison with the examples and are not intended to limit the present invention. Unless otherwise noted, the various raw materials used in the examples and comparative examples are conventional commercially available products or can be prepared by known methods.

[0053] Example 1

[0054] This embodiment provides a high-voltage lithium metal battery electrolyte, comprising: 85% solvent, 11% lithium salt, and 4% additives, calculated in percentage by mass;

[0055] In this embodiment, the solvent is a mixture of sulfolane and ethyl methyl carbonate (EMC), and the volume ratio of the two is 80%:20%;

[0056] In this embodiment, the lithium salt is lithium hexafluorophosphate (LiPF6);

[0057] In this embodiment, the additive is a mixture of adiponitrile, lithium difluorooxalatoborate (LiDFOB), and fluoroethylene carbonate (FEC), and the mass concentrations of the three are 0.5 wt %, 1.5 wt %, and 2 wt %, respectively.

[0058] This embodiment also provides a method for preparing the high-voltage lithium metal battery electrolyte, comprising the following steps:

[0059] Mix sulfolane and EMC evenly according to the volume ratio, then add LiPF6 and stir evenly until it is completely dissolved, and finally add adiponitrile, LiDFOB and FEC, stir and mix evenly to obtain a high-voltage lithium metal battery electrolyte.

[0060] Example 2

[0061] This embodiment is substantially the same as embodiment 1, with the only difference being that in this embodiment, the volume ratio of sulfolane to EMC is 60%:40%.

[0062] Example 3

[0063] This embodiment is substantially the same as embodiment 1, except that in this embodiment, the solvent is a mixture of sulfolane and dimethyl carbonate (DMC), and the volume ratio of the two is 90%:10%.

[0064] Example 4

[0065] This embodiment is substantially the same as the first embodiment, except that the high-voltage lithium metal electrolyte of this embodiment includes 85% solvent, 11.2% lithium salt, and 3.8% additive, wherein the mass concentrations of adiponitrile, LiDFOB, and FEC in the additive are 2 wt %, 0.9 wt %, and 0.9 wt %, respectively.

[0066] Example 5

[0067] This embodiment is substantially the same as the first embodiment, except that the electrolyte of this embodiment comprises 84% ​​solvent, 8% lithium salt, and 8% additive, wherein the additive is a mixture of adiponitrile, tris(2,2,2-trifluoroethyl) borate (TTFEB), and fluoroethylene carbonate (FEC), and the mass concentrations of the three are 0.2 wt %, 2.8 wt %, and 5 wt %, respectively.

[0068] Comparative Example 1

[0069] This comparative example is basically the same as Example 1, except that the mass concentrations of adiponitrile, LiDFOB and FEC in the additives of this comparative example are 3 wt %, 0.5 wt % and 0.5 wt %, respectively.

[0070] Comparative Example 2

[0071] This comparative example is substantially the same as Example 1, except that the volume ratio of sulfolane to EMC in the solvent of this comparative example is 95%:5%.

[0072] Comparative Example 3

[0073] This comparative example is substantially the same as Example 1, except that the volume ratio of sulfolane to EMC in the solvent of this comparative example is 50%:50%.

[0074] Comparative Example 4

[0075] This comparative example is basically the same as Example 1, except that the additive in this comparative example does not contain the positive electrode protection additive adiponitrile, that is, the additive in this comparative example is a mixture of LiDFOB and FEC, and the mass concentrations of the two are 2 wt% and 2 wt%, respectively.

[0076] Comparative Example 5

[0077] This comparative example is basically the same as Example 1, except that the additives in this comparative example do not contain the positive electrode film-forming additive LiDFOB, that is, the additives in this comparative example are a mixture of adiponitrile and FEC, and the mass concentrations of the two are 2 wt% and 2 wt% respectively.

[0078] Comparative Example 6

[0079] This comparative example is basically the same as Example 1, except that the additive in this comparative example does not contain the negative electrode film-forming additive FEC, that is, the additive in this comparative example is a mixture of adiponitrile and LiDFOB, and the mass concentrations of the two are 2 wt % and 2 wt %, respectively.

[0080] The electrolytes prepared in the above examples and comparative examples are respectively used in lithium metal batteries. The preparation method of the lithium metal battery comprises the following steps:

[0081] (1) The positive electrode active material (NCM811), conductive agent (SP), and binder (PVDF) were mixed uniformly in a mass ratio of 97:1:2, and then a solvent (NMP) was added and stirred to form a uniform slurry. The slurry was then evenly coated on a 13 μm carbon-coated aluminum foil using a transfer coater, and then rolled and cut to form positive electrode sheets;

[0082] (2) The negative electrode sheet is a lithium foil rolled on a copper substrate, with a copper foil thickness of 10 μm and a lithium foil thickness of 30 μm, which is cut into negative electrode sheets;

[0083] (3) The positive electrode sheet, negative electrode sheet, and separator (9 μm PE base film + 3 μm ceramic layer) are stacked to form a core package, and then the electrolytes of the above embodiments and comparative examples are injected respectively to assemble into a battery cell, which is then baked, injected with liquid, allowed to stand at high temperature, formed, and divided into different volumes to obtain a lithium metal soft pack battery.

[0084] Lithium metal batteries containing the electrolytes of the above examples and comparative examples were cycled at 25°C at 1C / 1C. The specific test steps were as follows: the initial test temperature was 25±2°C, and each group of cells was charged at 1C to 4.4V, then charged at a constant voltage to 0.05C, held for 10 minutes, and then discharged at 1C to 2.8V, held for 10 minutes. This cycle was repeated until the capacity dropped to 80% of the initial capacity. The cycle data are shown in Table 1.

[0085] Table 1

[0086]

[0087]

[0088] It can be seen from Table 1 that, compared with the electrolytes prepared in the comparative examples, the electrolytes prepared in the examples of the present invention all exhibited better cycle performance.

[0089] Specifically, by comparing Examples 1, 4, and 5 with Comparative Example 1, it can be seen that in Comparative Example 1, due to the low addition ratio of the film-forming additive, the SEI film cannot be continuously generated after rupture during the cycle, which will lead to reduced cycle performance of the lithium metal battery. In contrast, the embodiments of the present invention control the addition amounts of the positive electrode protection additive, the positive electrode film-forming additive, and the negative electrode film-forming additive to be between 0.2wt% and 2wt%, 0.9wt% and 5wt%, and 0.9wt% and 5wt%, respectively, to ensure normal cycling. The battery performance is optimal when the ratio of the three is 0.5%:1.5%:2%.

[0090] By comparing Examples 1-3 with Comparative Examples 2-3, it can be seen that the addition ratio of sulfolane in Comparative Example 2 is too high and the addition ratio of sulfolane in Comparative Example 3 is too low, which will lead to a significant deterioration in the cycle performance of the lithium metal battery; in contrast, in Examples 1-3 of the present invention, the addition amount of sulfolane is controlled between 60% and 90%, which can ensure the normal progress of the cycle, and the capacity retention rate is the highest when the addition amount is 80%, indicating that when the ratio of sulfolane to ethyl methyl carbonate is 80:20, the high pressure resistance and viscosity of the solution will show an optimal balance, and the performance of the lithium metal battery is the best at this time.

[0091] By comparing Example 1 with Comparative Examples 4-6, it can be seen that the positive electrode protection additive, positive electrode film-forming additive, and negative electrode film-forming additive in the embodiments of the present invention have a synergistic effect, complement each other, and are indispensable. Comparative Example 4 lacks a positive electrode protection additive, which causes the metal elements in the positive electrode material to dissolve under high pressure, destroying the material structure while also catalyzing the decomposition of the electrolyte, thereby reducing the cycle performance of the lithium metal battery; while Comparative Examples 5 and 6 lack a positive electrode film-forming additive and a negative electrode film-forming additive, respectively, resulting in the inability to form a dense CEL film and SEI film on the positive and negative electrode surfaces. As the reaction proceeds, the electrolyte will undergo a series of side reactions on the positive and negative electrode surfaces, resulting in rapid degradation of the cycle performance.

[0092] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0093] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A high-voltage lithium metal battery electrolyte, characterized in that: The method comprises a solvent, a lithium salt and an additive; wherein the solvent comprises a sulfone solvent and a carbonate solvent.

2. The high-voltage lithium metal battery electrolyte according to claim 1, characterized in that The high-voltage lithium metal battery electrolyte includes 70% to 90% solvent, 8% to 18% lithium salt and 2% to 12% additives, calculated in mass percentage.

3. The high-voltage lithium metal battery electrolyte according to claim 1, characterized in that In the solvent, the volume ratio of the sulfone solvent to the carbonate solvent is (60% to 90%): (40% to 10%); Optionally, the sulfone solvent includes at least one of sulfolane, dimethyl sulfone, and methyl ethyl sulfone; Optionally, the carbonate solvent includes at least one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

4. The high-voltage lithium metal battery electrolyte according to claim 1 or 2, characterized in that: The lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, and lithium hexafluorophosphate.

5. The high-voltage lithium metal battery electrolyte according to claim 1 or 2, characterized in that: The additives include a mixture of a positive electrode protection additive, a positive electrode film-forming additive, and a negative electrode film-forming additive; Optionally, in the high-voltage lithium metal battery electrolyte, the mass concentration of the positive electrode protection additive is 0.2wt% to 2wt%, the mass concentration of the positive electrode film-forming additive is 0.9wt% to 5wt%, and the mass concentration of the negative electrode film-forming additive is 0.9wt% to 5wt%.

6. The high-voltage lithium metal battery electrolyte according to claim 5, characterized in that The positive electrode protection additive includes at least one of adiponitrile, succinonitrile, and ethanetrinitrile.

7. The high-voltage lithium metal battery electrolyte according to claim 5, characterized in that The positive electrode film-forming additive includes at least one of lithium difluorooxalatoborate and tris(2,2,2-trifluoroethyl) borate.

8. The high-voltage lithium metal battery electrolyte according to claim 5, characterized in that The negative electrode film-forming additive includes at least one of fluoroethylene carbonate, bisfluoroethylene carbonate, and lithium difluorophosphate.

9. A method for preparing a high-voltage lithium metal battery electrolyte according to any one of claims 1 to 8, characterized in that: The steps include: The high-voltage lithium metal battery electrolyte is obtained by mixing a sulfone solvent and a carbonate solvent, adding a lithium salt and stirring to dissolve, and finally adding an additive and stirring to mix.

10. A lithium metal battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet, a separator and the high-voltage lithium metal battery electrolyte according to any one of claims 1 to 8.

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