Non-aqueous electrolyte and lithium metal battery

Abstract

This invention provides a non-aqueous electrolyte and a lithium metal battery. The non-aqueous electrolyte comprises a lithium salt, a solvent, a co-solvent, a diluent, and an additive; the additive includes a nitrate ester compound, wherein the nitrate ester compound contains at least two nitrate ester groups in its structure. This invention provides a non-aqueous electrolyte with both high voltage and good flame retardant properties, which can form a double-layer solid electrolyte film (SEI film) on the surface of the lithium metal anode (where the inorganic component layer is located on the side closer to the lithium metal anode, and the organic component layer is located on the other side of the inorganic component layer). The above-mentioned double-layer solid electrolyte film not only improves the uniformity of lithium ion deposition and reduces the consumption rate of active lithium and electrolyte, but also improves the antioxidant and flame retardant properties of the electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte materials technology, specifically relating to a non-aqueous electrolyte and a lithium metal battery. Background Technology

[0002] Based on the different forms in which lithium exists within the battery, lithium batteries are classified into lithium-ion batteries and lithium metal batteries. Lithium batteries are widely used in various fields, such as portable electronic instruments, electric vehicles, and various energy storage systems. Lithium metal anodes are particularly valuable due to their high theoretical capacity (up to 3860 mAh g⁻¹). -1 Due to its advantages of low operating potential (-3.04V), lithium metal batteries are considered one of the most promising anode materials. However, some problems still exist in their application, as described below:

[0003] First, the high reactivity of lithium metal and the growth of lithium dendrites cause many serious safety problems. At the same time, lithium dendrites may form "dead lithium" or puncture the separator, resulting in low coulombic efficiency of the battery, short circuits and other hazards.

[0004] Secondly, on the one hand, most commercial lithium-ion batteries use carbonate-based electrolytes because carbonates can form a stable solid electrolyte interphase (SEI) film on the graphite anode, preventing further decomposition of the electrolyte. However, the poor compatibility between lithium metal anodes and carbonate-based electrolytes leads to the formation of lithium dendrites, resulting in low coulombic efficiency and limited cycle life. On the other hand, although ether-based electrolytes can improve compatibility with lithium metal anodes, thereby regulating lithium deposition, reducing the formation of high-lithium dendrites, and improving coulombic efficiency, their poor oxidation stability (typically below 4V) and high flammability pose serious safety risks. Furthermore, while researchers have employed various methods to improve the oxidation stability of ether-based electrolytes, broadening their electrochemical window remains a significant challenge.

[0005] Finally, the SEI film is one of the important factors affecting the performance of lithium metal batteries. The formation of an unevenly distributed SEI film will lead to the dispersion and transport of lithium ions, resulting in the continuous breakage and reconstruction of the SEI film, causing the loss of active lithium and rapid depletion of electrolyte, ultimately deteriorating the cycle performance of lithium metal batteries.

[0006] In recent years, non-flammable electrolytes such as phosphate-based electrolytes, solid electrolytes, and ionic liquids have been extensively studied. Among them, organic phosphates, especially low molecular weight phosphates, have advantages such as low viscosity, non-flammability, and wide potential window, and are expected to become safe electrolyte solvents. However, phosphates cannot establish a stable solid electrolyte interface (SEI film) on the negative electrode surface, resulting in poor electrochemical performance of the battery, thus limiting its commercial application.

[0007] Therefore, there is an urgent need in this field to develop an electrolyte system to improve the overall performance of lithium metal batteries. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a non-aqueous electrolyte and a lithium metal battery. The present invention provides a non-aqueous electrolyte that combines high voltage and good flame retardant properties. It can form a double-layer solid electrolyte film (SEI film) on the surface of the lithium metal anode, wherein the inorganic component layer is located on the side closest to the lithium metal anode, and an organic component layer is located on the other side of the inorganic component layer. This double-layer solid electrolyte film not only improves the uniformity of lithium-ion deposition and reduces the consumption rate of active lithium and electrolyte, but also improves the electrolyte's antioxidant and flame-retardant properties.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a non-aqueous electrolyte, the non-aqueous electrolyte comprising lithium salt, solvent, co-solvent, diluent and additive;

[0011] The additive includes nitrate ester compounds, which contain at least two nitrate ester groups in their structure.

[0012] First, this invention achieves the formation of a double-layer solid electrolyte membrane (SEI membrane) on the surface of the lithium metal anode by adding nitrate ester compounds. The SEI membrane is located on the side closer to the lithium metal anode and is rich in LiN. x O yThe invention employs a double-layer SEI film (an inorganic component layer on one side and an organic component layer on the other), which significantly improves the uniformity of lithium-ion deposition and reduces the consumption rate of active lithium and electrolyte. Secondly, the use of a diluent with good oxidation stability facilitates the formation of a thinner SEI film with a higher inorganic content. Simultaneously, the relatively weak interaction between the diluent and the solvation shell (a layer of solvent molecules on the surface of the positive and negative electrode materials in the battery) enhances the coordination effect with lithium ions, thereby improving the oxidation resistance of the electrolyte. Furthermore, the invention utilizes a co-solvent, diluent, and solvent in combination to prepare a non-aqueous electrolyte with a wide electrochemical window and high ionic conductivity, specifically increasing the electrochemical window of the electrolyte to above 4.0V.

[0013] In this invention, by controlling the number of nitrate ester groups in nitrate ester compounds, increasing the number of nitrate ester groups helps to improve the desolvation capability, because nitrate ions can enter the inner layer of lithium and anion bonding. During charging, anions are more easily desolvated and more easily form films on the lithium surface.

[0014] Preferably, the nitrate ester compound includes any one or a combination of at least two of isosorbide dinitrate, glycerol 1,3-dinitrate, propylene glycol dinitrate, diethylene glycol dinitrate, ethylene glycol dinitrate, [13C6]-isosorbitol dinitrate, or 3-(2-methoxyphenoxy)propane-1,2-dinitrate.

[0015] Preferably, the nitrate ester compound includes any one of 3-(2-methoxyphenoxy)propane-1,2-dinitrate, [13C6]-isosorbitol dinitrate, ethylene glycol dinitrate, or diethylene glycol dinitrate.

[0016] Preferably, the nitrate ester compounds include a combination of 3-(2-methoxyphenoxy)propane-1,2-dinitrate and glycerol-1,3-dinitrate, or a combination of 3-(2-methoxyphenoxy)propane-1,2-dinitrate and [13C6]-isosorbitol dinitrate.

[0017] Preferably, based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of the additive is 0.1-10 wt.%, more preferably 0.5-7.5 wt%, for example, it can be 0.1 wt.%, 0.2 wt.%, 0.5 wt.%, 0.8 wt.%, 1 wt.%, 1.5 wt.%, 2 wt.%, 2.5 wt.%, 3 wt.%, 3.5 wt.%, 4 wt.%, 4.5 wt.%, 5 wt.%, 5.5 wt.%, 6 wt.%, 6.5 wt.%, 7 wt.%, 7.5 wt.%, 8 wt.%, 8.5 wt.%, 9 wt.%, 9.5 wt.%, 10 wt.%, etc.

[0018] In this invention, the amount of additive entering the lithium-anion bonding layer is further controlled by adjusting the mass percentage content of the additive, thereby regulating the solvation capability. If the content is too low, the solvation capability will not be improved, resulting in excessive solvation of lithium and anions. During battery charging, lithium and anions reach the negative electrode surface, affecting battery polarization and reducing the battery's capacity. In severe cases, lithium may directly deposit on the surface, leading to lithium dendrite formation. If the lithium desolvation process is incomplete, a solvent molecule will enter the negative electrode, damaging its structure and causing rapid lithium degradation, thus affecting battery life. Conversely, insufficient solvation capability leads to inadequate solvation. Lower solvation capability is not always better; insufficient solvation causes ion aggregation, poor ion movement, and reduced salt solubility, resulting in increased polarization and ultimately rapid performance degradation of the battery.

[0019] Preferably, the diluent comprises perfluoroalkane compounds.

[0020] In this invention, perfluoroalkane compounds are used as diluents, which have the following advantages: ① for Li + The coordination effect of the anion-induced solvation structure is relatively small, which is beneficial to suppress the decoupling of ether / lithium salt anions and improve the antioxidant capacity of the electrolyte; ② Perfluoroalkane compounds have better oxidation stability than conventional hydrofluoric acid diluents; ③ The higher F / C ratio is beneficial to the formation of a thinner SEI film with a higher inorganic content; ④ Its interaction with the solvation shell is relatively weak, thereby enhancing lithium ion coordination and improving the antioxidant performance of the electrolyte.

[0021] Preferably, the perfluoroalkane compounds include C5-18-perfluoroalkanes, perfluoroalkanes mixtures FC-40, perfluorooctane, perfluorononane, perfluorohexane, perfluorodecane, perfluorobutane, perfluoron-pentane, perfluorohexadecane, perfluorocyclopentane, perfluorotetradecane, perfluorododecane, perfluoron-heptane, perfluoropentadecane, perfluorocyclohexane, perfluorotridecane, perfluorotetracosane, perfluorobutylethane, perfluoroeicosane, perfluorohexylethane, perfluoro(methylcyclohexane), perfluorohexyloctane, and perfluorobutane. The perfluorocyclohexane, perfluoromethylcyclopentane, perfluorodimethylcyclobutane, perfluoro-2,7-dimethyloctane, perfluoro-1,2-dimethylcyclohexane, perfluoro-2,2,3,3-tetramethylbutane, perfluoro-2-methyl-2,3-epoxypentane, or perfluoro-1,3,5-trimethylcyclohexane, preferably any one or a combination of at least two of perfluoro(methylcyclohexane), perfluorodimethylcyclobutane, or perfluoro-1,3,5-trimethylcyclohexane.

[0022] Preferably, the co-solvent includes cyclophosphonitrile solvents.

[0023] In this invention, cyclophosphonitrile solvents are used as co-solvents for ether-based electrolytes. The F, N and P elements contained in their structure have flame-retardant effects and can form an SEI film rich in LiF and Li3N on the lithium metal surface. Furthermore, by controlling their volume ratio to within 20%, the overall conductivity of the non-aqueous electrolyte will not be affected.

[0024] Preferably, the cyclophosphonitrile solvents include hexafluorocyclotriphosphonitrile, ethoxy(pentafluoro)cyclotriphosphonitrile, phenoxycyclophosphonitrile, pentafluoro(phenoxy)cyclotriphosphonitrile, hexa(1,1,5-hydroperfluoropentoxy)cyclotriphosphonitrile, 3,3-difluorocyclobutaneformonitrile, 2-(3,3-difluorocyclobutyl)acetonitrile, hexa(1H,1H-perfluoropropoxy)phosphonitrile, hexa(1H,1H-nonafluoropentoxy)phosphonitrile, hexa(1H,1H-perfluorohexyloxy)phosphonitrile, and hexa(1H,1H,7H-perfluoropropoxy)phosphonitrile. The phosphoric acid is any one or a combination of at least two of the following: fluoroheptoxyphosphazene, hexa(1H,1H,3H-perfluoropropoxyphosphazene)phosphazene, or hexa(4-'carboxyphenoxy')cyclotriphosphazene, preferably pentafluoro(phenoxy)cyclotriphosphazene, hexa(1,1,5-hydroperfluoropentoxy)cyclotriphosphazene, 2-(3,3-difluorocyclobutyl)acetonitrile, hexa(1H,1H,7H-perfluoroheptoxy)phosphazene, or hexa(1H,1H,3H-perfluoropropoxy)phosphazene.

[0025] Preferably, the lithium salt comprises lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide.

[0026] Preferably, the concentration of the lithium salt is 1 to 3.5 mol / L, for example, it can be 1 mol / L, 1.2 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.5 mol / L, 2.8 mol / L, 3 mol / L, 3.2 mol / L, 3.5 mol / L, etc.

[0027] In this invention, by adjusting the concentration of lithium salt, the lithium salt is fully dissolved in the solvent and co-solvent, and the prepared electrolyte is clear, transparent, and completely dissociated.

[0028] Preferably, the solvent includes ether solvents.

[0029] Preferably, the ether solvent includes any one or a combination of at least two of the following: vinyl glycol ether, tetraethylene diethanol ether, tripropylene glycol ether, dibutyl triethylene glycol ether, vinyl diethylene glycol ether, tetraethylene glycol dibutyl ether, tetraethylene glycol dihexyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dipentyl ether; diethylene glycol dibutyl ether, diethylene glycol dihexyl ether, diethylene glycol diethyl ether, diethylene glycol dipentyl ether, triethylene glycol dibutyl ether, triethylene glycol dihexyl ether, triethylene glycol diethyl ether, or triethylene glycol dipentyl ether, preferably tetraethylene glycol diethyl ether and / or triethylene glycol dihexyl ether.

[0030] Preferably, the volume ratio of the solvent, co-solvent, and diluent is (0.5–4):(0.1–2):(5–9), more preferably (1–3):(0.5–1.5):(5.5–8.5), for example, 0.5:0.1:5, 0.8:0.2:5.5, 1:0.5:5.8, 1.5:0.8:6, 2:1:6.5, 2.5:1.5:7, 3:1.8:7.5, 3.5:2:8, 4:2:9, etc.

[0031] In this invention, by adjusting the volume ratio of solvent, co-solvent, and diluent, the conductivity of the electrolyte is made not less than 4.5 mS × cm. -1 If the volume ratio is too low, the lithium salt will not be able to dissolve completely and may precipitate out; conversely, it will affect the viscosity, conductivity and other parameters of the electrolyte.

[0032] In a second aspect, the present invention provides a lithium metal battery, the lithium metal battery comprising a positive electrode, a negative electrode and an electrolyte, the electrolyte comprising the non-aqueous electrolyte according to the first aspect.

[0033] Preferably, the negative electrode material includes lithium metal.

[0034] In this invention, the cathode material includes, for example, ternary cathode material, perfluoroeicosane lithium-rich manganese-based cathode material, or sulfur cathode material.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention provides a non-aqueous electrolyte. First, by adding nitrate ester compounds, a double-layer solid electrolyte membrane (SEI membrane) can be formed on the surface of the lithium metal anode, wherein the side closer to the lithium metal anode is rich in LiN. x O y The invention employs a double-layer SEI film (an inorganic component layer on one side and an organic component layer on the other), which significantly improves the uniformity of lithium-ion deposition and reduces the consumption rate of active lithium and electrolyte. Secondly, the use of a diluent with good oxidation stability facilitates the formation of a thinner SEI film with a higher inorganic content. Simultaneously, the relatively weak interaction between the diluent and the solvation shell (a layer of solvent molecules on the surface of the positive and negative electrode materials in the battery) enhances the coordination effect with lithium ions, thereby improving the oxidation resistance of the electrolyte. Furthermore, the invention utilizes a co-solvent, diluent, and solvent in combination to prepare a non-aqueous electrolyte with a wide electrochemical window and high ionic conductivity, specifically increasing the electrochemical window of the electrolyte to above 4.0V.

[0037] In this invention, by controlling the number of nitrate ester groups in nitrate ester compounds, increasing the number of nitrate ester groups helps to improve the desolvation capability, because nitrate ions can enter the inner layer of lithium and anion bonding. During charging, anions are more easily desolvated and more easily form films on the lithium surface. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0039] Example 1

[0040] This embodiment provides a non-aqueous electrolyte, which includes lithium bis(fluorosulfonyl)imide, triethylene glycol dihexyl ether solvent, phenoxycyclophosphonitrile co-solvent, perfluoroeicosane diluent, and ethylene glycol dinitrate additive.

[0041] Of which, based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of ethylene glycol dinitrate additive is 5 wt.%, the concentration of lithium bis(fluorosulfonyl)imide is 1 mol / L, and the volume ratio of triethylene glycol dihexyl ether, phenoxycyclophosphonitrile and perfluoroeicosane is 1:2:7.

[0042] This embodiment also provides a method for preparing the above-mentioned non-aqueous electrolyte, which includes the following steps:

[0043] When the oxygen content is <5ppm and the water content is <2ppm, the above components are mixed according to the formula amount and stirred evenly to obtain the non-aqueous electrolyte.

[0044] Example 2

[0045] This embodiment provides a non-aqueous electrolyte, which includes lithium bis(fluorosulfonyl)imide, triethylene glycol dihexyl ether solvent, phenoxycyclophosphonitrile co-solvent, perfluoroeicosane diluent, and ethylene glycol dinitrate additive.

[0046] Of which, based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of ethylene glycol dinitrate additive is 5 wt.%, the concentration of lithium bis(fluorosulfonyl)imide is 1.3 mol / L, and the volume ratio of triethylene glycol dihexyl ether, phenoxycyclophosphonitrile and perfluoroeicosane is 1:2:7.

[0047] This embodiment also provides a method for preparing the above-mentioned non-aqueous electrolyte, which includes the following steps:

[0048] When the oxygen content is <5ppm and the water content is <2ppm, the above components are mixed according to the formula amount and stirred evenly to obtain the non-aqueous electrolyte.

[0049] Example 3

[0050] This embodiment provides a non-aqueous electrolyte, which includes lithium bis(trifluoromethanesulfonylimide), tetraethylene glycol dihexyl ether solvent, pentafluoro(phenoxy)cyclotriphosphazene co-solvent, perfluoron-heptane diluent, and isosorbide nitrate additive.

[0051] Of which, based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of isosorbide nitrate additive is 2.5 wt.%, the concentration of lithium bis(trifluoromethanesulfonylimide) is 2 mol / L, and the volume ratio of tetraethylene glycol dihexyl ether, pentafluoro(phenoxy)cyclotriphosphazene and perfluoron-heptane is 3:1:6.

[0052] This embodiment also provides a method for preparing the above-mentioned non-aqueous electrolyte, which includes the following steps:

[0053] When the oxygen content is <5ppm and the water content is <2ppm, the above components are mixed according to the formula amount and stirred evenly to obtain the non-aqueous electrolyte.

[0054] Example 4

[0055] The difference between this embodiment and Example 1 is that the ethylene glycol dinitrate additive is replaced with an equal amount of isosorbide nitrate additive; otherwise, they are the same as in Example 1.

[0056] Example 5

[0057] The difference between this embodiment and Example 1 is that phenoxycyclophosphonitrile is replaced with an equal amount of hexanoic acid cosolvent; otherwise, they are the same as in Example 1.

[0058] Example 6

[0059] The difference between this embodiment and Embodiment 1 is that the perfluoroeicosane diluent is replaced with an equal amount of hydrofluoric acid diluent; otherwise, they are the same as in Embodiment 1.

[0060] Example 7

[0061] The difference between this embodiment and Example 1 is that the volume ratio of triethylene glycol dihexyl ether, phenoxycyclophosphonitrile, and perfluoroeicosane is 0.1:0.05:1, while all other aspects are the same as in Example 1.

[0062] Example 8

[0063] The difference between this embodiment and Example 1 is that the volume ratio of triethylene glycol dihexyl ether, phenoxycyclophosphonitrile, and perfluoroeicosane is 8:5:15, while all other aspects are the same as in Example 1.

[0064] Example 9

[0065] The difference between this embodiment and Example 1 is that the ethylene glycol dinitrate additive is replaced with an equal amount of isosorbide 2-nitrate additive; otherwise, they are the same as in Example 1.

[0066] Example 10

[0067] The difference between this embodiment and Example 1 is that lithium bis(fluorosulfonyl)imide is replaced with lithium hexafluorophosphate of the same concentration; otherwise, they are the same as in Example 1.

[0068] Comparative Example 1

[0069] The difference between this comparative example and Example 1 is that the phenoxycyclophosphonitrile co-solvent is replaced with an equal amount of triethylene glycol dihexyl ether solvent; all other aspects are the same as in Example 1.

[0070] Comparative Example 2

[0071] The difference between this comparative example and Example 1 is that the perfluoroeicosane diluent is replaced with an equal amount of triethylene glycol diethyl ether solvent; otherwise, they are the same as in Example 1.

[0072] Comparative Example 3

[0073] The difference between this comparative example and Example 1 is that the ethylene glycol dinitrate additive is replaced with an equal amount of lithium nitrate additive; otherwise, they are the same as in Example 1.

[0074] Application Examples 1 to 10 and Comparative Application Examples 1 to 3

[0075] Lithium-ion batteries were prepared using the non-aqueous electrolytes provided in Examples 1 to 10 and Comparative Examples 1 to 3, and the preparation methods are as follows:

[0076] The positive electrode sheet is prepared by mixing lithium nickel cobalt manganese oxide ternary material LiNi9Co1Mn1O2, conductive agent SuperP, binder PVDF and carbon nanotubes at a mass ratio of 96.0:2.5:1.0:0.5 to form a lithium-ion battery positive electrode slurry of a certain viscosity. The slurry is coated on aluminum foil for current collector, dried at 85°C and then cold-pressed. After trimming, cutting and slitting, the slurry is dried at 85°C under vacuum for 8 hours to produce a lithium metal battery positive electrode sheet that meets the requirements.

[0077] The negative electrode uses 6μm thick copper foil purchased from the market and a copper-lithium composite strip with lithium on both sides (lithium thickness is 20μm); it is then cut, diced and slit to produce a lithium metal battery negative electrode sheet that meets the requirements.

[0078] Preparation of lithium metal pouch battery: The positive electrode, negative electrode and separator prepared according to the above process are stacked to form a lithium metal battery with three positive and four negative electrodes and a capacity of 1700mAh. The electrolyte is then injected to complete the battery manufacturing.

[0079] Test conditions

[0080] The lithium-ion batteries provided in Application Examples 1 to 10 and Comparative Application Examples 1 to 3 were tested using the following methods:

[0081] Room temperature formation test: At 25℃, charge the battery to 3.7V with a constant current of 0.01C, charge it to 4.35V with a constant current of 0.05C, charge it to 4.35V with a constant voltage of 4.35V until the cutoff current is 0.05C, and then discharge the battery to 3.0V with a constant current of 0.05C.

[0082] Room temperature cycling test: At 25℃, the battery was charged at a constant current of 0.33C to 4.4V, then charged at a constant voltage of 4.35V to the cutoff current of 0.05C. The battery was then discharged at a constant current of 0.33C to 3.0V. The discharge capacity was recorded as C1. This charge-discharge cycle was repeated 300 times to obtain the discharge capacity C in the Nth cycle. N Capacity retention rate = (C N / C1)×100%.

[0083] The test results are shown in Table 1:

[0084] Table 1

[0085]

[0086] Note: For pouch lithium metal batteries, if the capacity retention rate is below 85% and the coulombic efficiency is below 98% during cycle testing, the battery testing will be stopped.

[0087] As can be seen from Table 1, the electrolyte provided by the present invention has good antioxidant properties, a wide electrochemical window range, and good electrochemical performance. As shown in Application Examples 1-3, the batteries provided in Application Examples 1-3 have high initial coulombic efficiency, good cycle stability, a wide electrochemical window, and high conductivity.

[0088] Compared to Application Example 1, Application Example 4 uses isosorbide dinitrate additive, which is less effective than ethylene glycol dinitrate additive; Application Examples 5-6 show that replacing them with conventional cosolvents and diluents cannot achieve all the technical effects that the present invention can achieve.

[0089] Compared to Application Example 1, Application Examples 7 and 8 demonstrate that the electrochemical window and conductivity can be balanced by adjusting the volume ratio of triethylene glycol dihexyl ether, phenoxycyclophosphonitrile, and perfluoroeicosane. Application Example 8 shows that a higher content of cosolvent results in a higher antioxidant capacity, leading to a higher LSV value, but a lower conductivity, while Application Example 7 shows the opposite.

[0090] Compared with Application Example 1, Application Example 9 shows that a better technical effect can be achieved by adjusting the amount of nitrate.

[0091] Comparative application examples 1-3 show that neither adding diluents and cosolvents nor replacing them with conventional lithium nitrate additives can improve the overall performance of the battery.

[0092] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A nonaqueous electrolyte, characterized by comprising: The non-aqueous electrolyte includes lithium salt, solvent, co-solvent, diluent, and additives; The additive includes nitrate ester compounds, wherein the structure of the nitrate ester compounds contains at least two nitrate ester groups; The diluent includes perfluoroalkane compounds; The co-solvent includes cyclophosphonitrile solvents; The solvent includes ether solvents; Based on the total mass of the non-aqueous electrolyte (100%), the additive has a mass percentage content of 0.1~10 wt.%. The volume ratio of the solvent, co-solvent, and diluent is (0.5~4):(0.1~2):(5~9).

2. The nonaqueous electrolyte according to claim 1, characterized by The nitrate compounds include any one or a combination of at least two of isosorbide dinitrate, glycerol 1,3-dinitrate, propylene glycol dinitrate, diethylene glycol dinitrate, ethylene glycol dinitrate, [13C6]-isosorbitol dinitrate, or 3-(2-methoxyphenoxy)propane-1,2-dinitrate.

3. The non-aqueous electrolyte according to claim 2, characterized in that, The nitrate ester compounds include any one of 3-(2-methoxyphenoxy)propane-1,2-dinitrate, [13C6]-isosorbitol dinitrate, ethylene glycol dinitrate, or diethylene glycol dinitrate.

4. The nonaqueous electrolyte according to claim 2, wherein The nitrate compounds include combinations of 3-(2-methoxyphenoxy)propane-1,2-dinitrate and glycerol-1,3-dinitrate, and combinations of 3-(2-methoxyphenoxy)propane-1,2-dinitrate and [13C6]-isosorbitol dinitrate.

5. The nonaqueous electrolyte according to claim 1, wherein Based on the total mass of the non-aqueous electrolyte as 100%, the mass percentage of the additive is 0.5~7.5wt%.

6. The nonaqueous electrolyte according to claim 1, wherein The perfluoroalkane compounds include any one or a combination of at least two of the following: perfluoroalkane mixtures FC-40, perfluorooctane, perfluorononane, perfluorohexane, perfluorodecane, perfluorobutane, perfluoron-pentane, perfluorohexadecane, perfluorocyclopentane, perfluorotetradecane, perfluorododecane, perfluoron-heptane, perfluoropentadecane, perfluorocyclohexane, perfluorotridecane, perfluorotetracosane, perfluoroeicosane, perfluoro(methylcyclohexane), perfluorobutylcyclohexane, perfluoromethylcyclopentane, perfluorodimethylcyclobutane, perfluoro-2,7-dimethyloctane, perfluoro-1,2-dimethylcyclohexane, perfluoro-2,2,3,3-tetramethylbutane, or perfluoro-1,3,5-trimethylcyclohexane.

7. The nonaqueous electrolyte according to claim 6, wherein The perfluoroalkane compounds include any one or a combination of at least two of perfluoro(methylcyclohexane), perfluorodimethylcyclobutane, or perfluoro1,3,5-trimethylcyclohexane.

8. The nonaqueous electrolyte according to claim 1, wherein The cyclophosphonitrile solvents include any one or a combination of at least two of the following: hexafluorocyclotriphosphonitrile, ethoxy(pentafluoro)cyclotriphosphonitrile, phenoxycyclotriphosphonitrile, pentafluoro(phenoxy)cyclotriphosphonitrile, hexa(1,1,5-hydroperfluoropentoxy)cyclotriphosphonitrile, hexa(1H,1H-perfluoropropoxy)phosphonitrile, hexa(1H,1H-nonafluoropentoxy)phosphonitrile, hexa(1H,1H-perfluorohexyloxy)phosphonitrile, hexa(1H,1H,7H-perfluoroheptoxy)phosphonitrile, hexa(1H,1H,3H-perfluoropropoxy)phosphonitrile, or hexa(4-'carboxyphenoxy')cyclotriphosphonitrile.

9. The nonaqueous electrolyte according to claim 8, wherein The cyclophosphonitrile solvents include any one or a combination of at least two of pentafluoro(phenoxy)cyclotriphosphonitrile, hexa(1,1,5-hydroperfluoropentoxy)cyclotriphosphonitrile, 2-(3,3-difluorocyclobutyl)acetonitrile, hexa(1H,1H,7H-perfluoroheptoxy)phosphonitrile or hexa(1H,1H,3H-perfluoropropoxy)phosphonitrile.

10. The nonaqueous electrolyte according to claim 1, wherein The lithium salt includes lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethanesulfonyl)imide.

11. The non-aqueous electrolyte according to claim 1, characterized in that, The concentration of the lithium salt is 1~3.5 mol / L.

12. The non-aqueous electrolyte according to claim 1, characterized in that, The ether solvents include any one or a combination of at least two of the following: vinyl glycol ether, tetraethylene diethanol ether, tripropylene glycol ether, dibutyl triethylene glycol ether, vinyl diethylene glycol ether, tetraethylene glycol dibutyl ether, tetraethylene glycol dihexyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dipentyl ether, diethylene glycol dibutyl ether, diethylene glycol dihexyl ether, diethylene glycol dipentyl ether, triethylene glycol dibutyl ether, triethylene glycol dihexyl ether, triethylene glycol diethyl ether, or triethylene glycol dipentyl ether.

13. The nonaqueous electrolyte according to claim 12, wherein The ether solvents include tetraethylene glycol diethyl ether and / or triethylene glycol diethyl ether.

14. The nonaqueous electrolyte according to claim 1, wherein The volume ratio of the solvent, co-solvent, and diluent is (1~3):(0.5~1.5):(5.5~8.5).

15. A lithium metal battery, characterized in that, The lithium metal battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the electrolyte includes a non-aqueous electrolyte according to any one of claims 1-14.

16. The lithium metal battery of claim 15, wherein, The negative electrode material includes lithium metal.

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