CN117650279A

CN117650279A - Nonaqueous electrolyte and lithium metal battery

Info

Publication number: CN117650279A
Application number: CN202311682787.XA
Authority: CN
Inventors: 朱甜; 胡波剑; 马勇; 李云明; 苗力孝; 苏甜; 师悦; 王宁
Original assignee: Svolt Energy Technology Co Ltd
Current assignee: Svolt Energy Technology Co Ltd
Priority date: 2023-12-08
Filing date: 2023-12-08
Publication date: 2024-03-05

Abstract

The invention provides a nonaqueous electrolyte and a lithium metal battery. The nonaqueous electrolyte comprises lithium salt, a solvent, a cosolvent, a diluent and an additive; the additive comprises a nitrate compound, wherein the structure of the nitrate compound contains at least two nitrate groups. The invention provides a non-aqueous electrolyte solution with high voltage and good flame retardant property, which can form a double-layer solid electrolyte membrane (SEI membrane for short) on the surface of a lithium metal negative electrode, wherein an inorganic component layer is arranged on one side close to the lithium metal negative electrode, and an organic component layer is arranged on the other side of the inorganic component layer), and the double-layer solid electrolyte membrane not only improves the deposition uniformity of lithium ions, reduces the consumption rate of active lithium and electrolyte, but also improves the oxidation resistance and flame retardant property of the electrolyte solution.

Description

Nonaqueous electrolyte and lithium metal battery

Technical Field

The invention belongs to the technical field of electrolyte materials, and particularly relates to a non-aqueous electrolyte and a lithium metal battery.

Background

According to the existence forms of lithium in lithium batteries, 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 have a high theoretical capacity (up to 3860mAh g ^-1 ) And low operating potential (-3.04V), but is considered one of the most promising anode materials, lithium metal batteries still have some problems in application as follows:

first, the high reactivity of lithium metal and lithium dendrite growth pose serious safety problems, and at the same time, lithium dendrites may form "dead lithium" or pierce the separator, causing various hazards such as low coulomb efficiency, short circuit, etc. of the battery.

Secondly, on the one hand, carbonate-based electrolytes are mostly used in commercial lithium ion batteries because carbonates can form a stable solid electrolyte interface layer (SEI film) on a graphite anode to prevent further decomposition of the electrolyte. However, the poor compatibility between lithium metal anodes and carbonate-based electrolytes results in the formation of lithium dendrites and results in batteries with lower coulombic efficiency and limited cycle life. On the other hand, although the ether-based electrolyte can improve compatibility with the metallic lithium anode, thereby adjusting deposition of metallic lithium, reducing formation of high lithium dendrite, and improving coulombic efficiency of the battery, the oxidation voltage is generally lower than 4V due to poor oxidation stability of the ether-based electrolyte, and most of the ether-based electrolytes have high flammability, possibly causing serious safety problems. In addition, researchers have employed a number of means to improve the oxidative stability of ether-based electrolytes, but widening the electrochemical window of ether-based electrolytes is a significant challenge.

Finally, the SEI film is one of important factors affecting the performance of the lithium metal battery, and the formation of the SEI film with uneven distribution can lead to the dispersion and transportation of lithium ions, thereby leading to continuous fracture and reconstruction of the SEI film, causing loss of active lithium and rapid exhaustion of electrolyte, and finally deteriorating the cycle performance of the lithium metal battery.

In recent years, phosphate-based electrolytes, solid electrolytes, ionic liquids and other non-flammable electrolytes have been widely studied, and among them, organic phosphates, particularly low molecular weight phosphates, have the advantages of low viscosity, nonflammability, wide potential window and the like, and are expected to be safe electrolyte solvents, but phosphates cannot establish a stable solid electrolyte interface (SEI film) on the surface of a negative electrode, resulting in poor electrochemical performance of a battery, and thus limiting commercial applications thereof.

Accordingly, there is a need in the art to develop an electrolyte system to improve the overall performance of lithium metal batteries.

Disclosure of Invention

In view of the shortcomings of the prior art, the invention aims to provide a nonaqueous electrolyte and a lithium metal battery. The invention provides a non-aqueous electrolyte solution with high voltage and good flame retardant property, which can form a double-layer solid electrolyte membrane (SEI membrane for short) on the surface of a lithium metal negative electrode, wherein an inorganic component layer is arranged on one side close to the lithium metal negative electrode, and an organic component layer is arranged on the other side of the inorganic component layer), and the double-layer solid electrolyte membrane not only improves the deposition uniformity of lithium ions, reduces the consumption rate of active lithium and electrolyte, but also improves the oxidation resistance and flame retardant property of the electrolyte solution.

In order to achieve the aim of the invention, the invention adopts the following technical scheme:

in a first aspect, the present invention provides a nonaqueous electrolyte comprising a lithium salt, a solvent, a cosolvent, a diluent, and an additive;

the additive comprises a nitrate compound, wherein the structure of the nitrate compound contains at least two nitrate groups.

Firstly, the invention can form a double-layer solid electrolyte membrane (SEI membrane for short) on the surface of a lithium metal anode by adding nitrate compoundThe side of the medium close to the lithium metal cathode is rich in LiN _x O _y The inorganic component layer is arranged on the other side of the inorganic component layer), the double-layer SEI film remarkably improves the uniformity of lithium ion deposition and reduces the consumption rate of active lithium and electrolyte. Secondly, the invention adopts the diluent with good oxidation stability, which is favorable for forming the SEI film with thinner thickness and higher inorganic matter content; meanwhile, the effect between the diluent and the solvation shell (which refers to a shell layer with a layer of solvent molecules on the surface of the anode material and the cathode material in the battery) is relatively weak, and the coordination effect with lithium ions can be enhanced, so that the oxidation resistance of the electrolyte is improved. In addition, the cosolvent, the diluent and the solvent are matched for use, so that the nonaqueous electrolyte with wider electrochemical window and high ionic conductivity is prepared, and the electrochemical window of the electrolyte can be improved to more than 4.0V.

In the invention, the quantity of nitrate groups in the nitrate compound is regulated and controlled, so that the quantity of nitrate groups is improved to help improve desolvation capacity, nitrate ions can enter the lithium and anion combined inner layer, anions are more easily desolvated in the charging process, and film formation is more easily carried out on the surface of lithium.

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

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

Preferably, the nitrate-based compound includes a combination of 3- (2-methoxyphenoxy) propane-1, 2-dinitrate and glycerin 1, 3-dinitrate, a combination of 3- (2-methoxyphenoxy) propane-1, 2-dinitrate and [13C6] -isosorbide dinitrate.

Preferably, the additive is 0.1 to 10wt.%, preferably 0.5 to 7.5wt.%, e.g., 0.1wt.%, 0.2wt.%, 0.8wt.%, 1.5wt.%, 2wt.%, 3wt.%, 4wt.%, 5wt.%, 5.5wt.%, 6.5wt.%, 7wt.%, 8.5wt.%, 9.5wt.%, 10wt.%, etc., based on the total mass of the nonaqueous electrolytic solution being 100 wt.%.

According to the invention, the quantity of the additive entering the lithium and anion binding layer is further regulated by regulating the mass percentage content of the additive, so that the solvation capacity can be regulated, the solvation capacity can not be improved due to the fact that the content is too low, the solvation capacity of the lithium and the anion is too strong, lithium and the anion can reach the surface of the negative electrode in the battery charging process, the battery polarization can be influenced, the playing capacity of the battery is reduced, lithium can be directly deposited on the surface in severe cases, lithium dendrite formation is caused, and if the lithium desolvation process is not thorough, a solvent molecule enters the negative electrode, the structure of the negative electrode is damaged, the lithium is rapidly attenuated, and the service life of the battery is further influenced. Conversely, the solvation capability is insufficient, the lower the solvation capability is, the better the solvation capability is, the ions are aggregated due to insufficient solvation, the ion movement is poor, the solubility of salt is reduced, the polarization is increased, and finally the performance of the battery is rapidly attenuated.

Preferably, the diluent comprises a perfluoroalkane.

In the invention, the perfluoroalkane compound is used as a diluent, and has the following advantages: (1) for Li ⁺ The coordination effect of the anion-induced solvation structure is smaller, which is favorable for inhibiting the decomplexing of ether/lithium salt anions and improving the antioxidant capacity of the electrolyte; (2) compared with the conventional hydrofluoric acid diluent, the perfluoroalkane compound has better oxidation stability; (3) the F/C ratio is higher, which is favorable for forming a thinner SEI film with higher inorganic matter content; (4) the effect of the lithium ion complex with the solvated shell is relatively weak, so that the coordination of the lithium ion is enhanced, and the oxidation resistance of the electrolyte is improved.

Preferably, the perfluoroalkanes include any one or a combination of at least two of C5-18-perfluoro-alkane, perfluoro-mixture FC-40, perfluoro-octane, perfluoro-nonane, perfluoro-hexane, perfluoro-decane, perfluoro-butane, perfluoro-n-pentane, perfluoro-hexadecane, perfluoro-cyclopentane, perfluoro-tetradecane, perfluoro-dodecane, perfluoro-n-heptane, perfluoro-pentadecane, perfluoro-cyclohexane, perfluoro-tridecane, perfluoro-tetracosane, perfluoro-butylethane, perfluoro-eicosane, perfluoro-hexylethane, perfluoro (methylcyclohexane), perfluoro-hexyloctane, perfluoro-butylcyclohexane, perfluoro-methylcyclopentane, perfluoro-dimethylcyclobutane, perfluoro-2, 7-dimethyloctane, perfluoro-1, 2-dimethylcyclohexane, perfluoro-2, 3-tetramethylbutane, perfluoro-2-methyl-2, 3-epoxypentane or perfluoro-1, 3, 5-trimethylcyclohexane, preferably perfluoro (methylcyclohexane), perfluoro (dimethylcyclohexane) or a combination of at least two of perfluoro-1, 3, 5-trimethylcyclohexane.

Preferably, the co-solvent comprises a cyclophosphazene solvent.

In the invention, the cyclophosphazene solvent is used as the cosolvent of the ether base electrolyte, and F, N and P elements contained in the structure of the cyclophosphazene solvent have flame retardant effect, and can form a catalyst rich in LiF and Li on the surface of lithium metal ₃ An SEI film of N; and the volume ratio is controlled within 20 percent, so that the conductivity of the whole nonaqueous electrolyte is not affected.

Preferably, the cyclic phosphazene solvent comprises any one or a combination of at least two of hexafluorocyclotriphosphazene, ethoxy (pentafluoro) cyclotriphosphazene, phenoxy cyclotriphosphazene, pentafluoro (phenoxy) cyclotriphosphazene, hexa (1, 5-hydroperfluoropentyloxy) cyclotriphosphazene, 3-difluorocyclobutanecarbonitrile, 2- (3, 3-difluorocyclobutyl) acetonitrile, hexa (1H, 1H-perfluoropropyloxy) phosphazene, hexa (1H, 1H-nonafluoropropyloxy) phosphazene, hexa (1H, 1H-perfluorohexyloxy) phosphazene, hexa (1H, 7H-perfluoroheptyloxy) phosphazene, hexa (1H, 3H-perfluoropropyloxy) phosphazene or hexa (4-carboxyphenoxy') cyclotriphosphazene, preferably any one or a combination of at least two of pentafluoro (phenoxy) cyclotriphosphazene, hexa (1, 5-hydroperfluoropentyloxy) cyclotriphosphazene, 2- (3, 3-difluorocyclobutyl) acetonitrile, hexa (1H, 7H-perfluoroheptyloxy) phosphazene or hexa (1H, 3H-perfluoropropoxy) phosphazene.

Preferably, the lithium salt comprises lithium bis-fluorosulfonyl imide or lithium bis-trifluoromethanesulfonyl imide.

The concentration of the lithium salt is preferably 1 to 3.5mol/L, and may be, for example, 1mol/L, 1.2mol/L, 1.5mol/L, 1.8mol/L, 2mol/L, 2.2mol/L, 2.5mol/L, 2.8mol/L, 3mol/L, 3.2mol/L, 3.5mol/L, or the like.

In the invention, the concentration of the lithium salt is regulated so that the lithium salt is fully dissolved in the solvent and the cosolvent, and the prepared electrolyte is clear and transparent and completely dissociated.

Preferably, the solvent comprises an ether solvent.

Preferably, the ether solvent comprises vinyl glycol ether, tetraethylene glycol ether, tripropylene glycol ether, tributyl glycol ether, vinyl glycol ether, tetraethylene glycol dibutyl ether, tetraethylene glycol dihexyl ether, tetraethylene glycol diethyl ether, tetraethylene glycol dipentyl ether; any one or a combination of at least two of 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.

Preferably, the volume ratio of the solvent, the cosolvent and the diluent is (0.5-4): 0.1-2): 5-9, preferably (1-3): 0.5-1.5): 5.5-8.5, for example, may be 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.

In the invention, the volume ratio of the solvent, the cosolvent and the diluent is regulated so that the conductivity of the electrolyte is not lower than 4.5ms multiplied by cm ^-1 When the volume ratio is too low, lithium salt cannot be completely dissolved and may be precipitated, otherwise, parameters such as viscosity and conductivity of the electrolyte are affected.

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

Preferably, the material of the negative electrode includes lithium metal.

In the present invention, the material of the positive electrode illustratively includes a ternary positive electrode material, a perfluoroeicosane lithium-rich manganese-based positive electrode material, or a sulfur positive electrode material.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a non-aqueous electrolyte, firstly, by adding nitrate compound, it can form double-layer solid electrolyte membrane (SEI membrane for short) on the surface of lithium metal negative electrode, wherein, near the side of lithium metal negative electrode, is rich in LiN _x O _y The inorganic component layer is arranged on the other side of the inorganic component layer), the double-layer SEI film remarkably improves the uniformity of lithium ion deposition and reduces the consumption rate of active lithium and electrolyte. Secondly, the invention adopts the diluent with good oxidation stability, which is favorable for forming the SEI film with thinner thickness and higher inorganic matter content; meanwhile, the effect between the diluent and the solvation shell (which refers to a shell layer with a layer of solvent molecules on the surface of the anode material and the cathode material in the battery) is relatively weak, and the coordination effect with lithium ions can be enhanced, so that the oxidation resistance of the electrolyte is improved. In addition, the cosolvent, the diluent and the solvent are matched for use, so that the nonaqueous electrolyte with wider electrochemical window and high ionic conductivity is prepared, and the electrochemical window of the electrolyte can be improved to more than 4.0V.

Detailed Description

The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.

Example 1

The present example provides a nonaqueous electrolyte comprising lithium bis (fluorosulfonyl) imide, triethylene glycol dihexyl ether solvent, phenoxy cyclophosphazene co-solvent, perfluoroeicosane diluent and ethylene glycol dinitrate additive.

Wherein, based on 100% of the total mass of the nonaqueous electrolyte, the mass percent of the ethylene glycol dinitrate additive is 5wt%, the concentration of lithium bis (fluorosulfonyl) imide is 1mol/L, and the volume ratio of triethylene glycol dihexyl ether, phenoxy cyclophosphazene and perfluoroeicosane is equal to 1:2:7.

The embodiment also provides a preparation method of the nonaqueous electrolyte, which comprises the following steps:

under the condition that the oxygen content is less than 5ppm and the water content is less than 2ppm, the components are mixed according to the formula amount, and the nonaqueous electrolyte is obtained after uniform stirring.

Example 2

Wherein, based on 100% of the total mass of the nonaqueous electrolyte, the mass percent of the ethylene glycol dinitrate additive is 5wt%, the concentration of lithium bis (fluorosulfonyl) imide is 1.3mol/L, and the volume ratio of triethylene glycol dihexyl ether, phenoxy cyclophosphazene and perfluoroeicosane is equal to 1:2:7.

Example 3

The present example provides a nonaqueous electrolyte comprising lithium bistrifluoromethane sulfonimide, tetraethylene glycol dihexyl ether solvent, pentafluoro (phenoxy) cyclotriphosphazene cosolvent, perfluoro-n-heptane diluent, and isosorbide nitrate additive.

Wherein, based on 100 percent of the total mass of the nonaqueous electrolyte, the mass percent of the isosorbide dinitrate additive is 2.5 wt%, the concentration of lithium bistrifluoromethane sulfonyl imide is 2mol/L, and the volume ratio of tetraethylene glycol dihexyl ether, pentafluoro (phenoxy) cyclotriphosphazene and perfluoro-n-heptane is equal to 3:1:6.

Example 4

This example differs from example 1 in that the ethylene glycol dinitrate additive was replaced with an equal amount of isosorbide nitrate additive, all other things being equal to example 1.

Example 5

This example differs from example 1 in that phenoxycyclophosphazene is replaced with an equal amount of capronitrile co-solvent, all other things being equal to example 1.

Example 6

This example differs from example 1 in that the perfluoroeicosane diluent was replaced with an equal amount of hydrofluoric acid diluent, all other things being equal to example 1.

Example 7

This example differs from example 1 in that the volume ratio of triethylene glycol dihexyl ether, phenoxycyclophosphazene to perfluoroeicosane is equal to 0.1:0.05:1, the others being the same as in example 1.

Example 8

This example differs from example 1 in that the volume ratio of triethylene glycol dihexyl ether, phenoxycyclophosphazene to perfluoroeicosane is equal to 8:5:15, all other things being equal to example 1.

Example 9

This example differs from example 1 in that the ethylene glycol dinitrate additive was replaced with an equal amount of isosorbide 2-nitrate additive, all other things being equal to example 1.

Example 10

This example differs from example 1 in that lithium bis (fluorosulfonyl) imide was replaced with lithium hexafluorophosphate at an equal concentration, and the other is the same as in example 1.

Comparative example 1

This comparative example differs from example 1 in that the phenoxycyclophosphazene co-solvent is replaced with an equal amount of triethylene glycol dihexyl ether solvent, all other things being equal to example 1.

Comparative example 2

This comparative example differs from example 1 in that the perfluoroeicosane diluent was replaced with an equivalent amount of triethylene glycol dihexyl ether solvent, all other things being equal to example 1.

Comparative example 3

This comparative example differs from example 1 in that the ethylene glycol dinitrate additive was replaced with an equivalent amount of lithium nitrate additive, all other things being equal to example 1.

Application examples 1 to 10 and comparative application examples 1 to 3

The nonaqueous electrolytic solutions provided in examples 1 to 10 and comparative examples 1 to 3 were prepared to obtain lithium ion batteries, and the preparation methods were as follows:

manufacturing a positive plate: ternary material LiNi of nickel cobalt lithium manganate ₉ Co ₁ Mn ₁ O ₂ Uniformly mixing a conductive agent SuperP, an adhesive PVDF and a carbon nano tube according to a mass ratio of 96.0:2.5:1.0:0.5 to prepare lithium ion battery anode slurry with certain viscosity, coating the lithium ion battery anode slurry on aluminum foil for a current collector, drying the aluminum foil at 85 ℃, and then cold pressing the aluminum foil; then trimming, cutting pieces and drying for 8 hours at 85 ℃ under vacuum condition after cutting to prepare the lithium metal battery positive plate meeting the requirements;

the cathode adopts copper foil with the thickness of 6 mu m purchased in the market, and a copper-lithium composite belt with double surfaces coated with lithium (the thickness of the lithium is 20 mu m); trimming, cutting and slitting to prepare a lithium metal battery negative plate meeting the requirements;

preparation of lithium metal soft package battery: and manufacturing the positive plate, the negative plate and the diaphragm prepared according to the process into a three-positive-four-negative lithium metal battery with the capacity of 1700mAh through a lamination process, and injecting the electrolyte to finish the battery manufacturing.

Test conditions

The lithium ion batteries provided in application examples 1 to 10 and comparative application examples 1 to 3 were tested as follows:

and (3) normal temperature formation test: charging to 3.7V at 25 ℃ with 0.01C constant current, charging to 4.35V with 0.05C constant current, charging to 0.05C constant voltage with 4.35V constant voltage, and discharging the battery to 3.0V with 0.05C constant current;

and (3) normal temperature cyclic test: charging to 4.4V at 25 ℃ with a constant current of 0.33 ℃, charging to a cut-off current of 0.05C with a constant voltage of 4.35V, and discharging the battery to 3.0V with a constant current of 0.33 ℃; the discharge capacity was recorded as C ₁ Repeating the charge and discharge process for 300 weeks to obtain the discharge capacity C at the nth week _N Capacity retention= (C _N /C ₁ )×100％。

The test results are shown in table 1:

TABLE 1

Note that: the cycle test capacity retention rate of the soft-package lithium metal battery is lower than 85%, the coulombic efficiency is lower than 98%, and the battery stops testing.

As can be seen from Table 1, the electrolyte provided by the invention has good oxidation resistance, wide electrochemical window range and electrochemical performance. As shown in application examples 1 to 3, the batteries provided in application examples 1 to 3 have high first coulombic efficiency, good cycling stability, a wide electrochemical window, and high conductivity.

In comparison with application example 1, application example 4 employed isosorbide dinitrate additive which was less effective than ethylene glycol dinitrate additive; application examples 5-6 demonstrate that the replacement of conventional co-solvents and diluent types does not achieve all of the technical benefits that can be achieved by the present invention.

Application examples 7 and 8 show that the electrochemical window and the conductivity are balanced by controlling the volume ratio of triethylene glycol dihexyl ether, phenoxycyclophosphazene and perfluoroeicosane compared with application example 1. Application example 8 shows that the co-solvent content is relatively high, the oxidation resistance of the co-solvent is relatively high, so the LSV value is high, but the conductivity is low, whereas application example 7 is the opposite.

Application example 9 shows that the technical effect is better by controlling the amount of nitrate esters compared with application example 1.

Comparative application examples 1-3 show that the combination of the battery cannot be improved without the addition of diluents, co-solvents, and replacement with conventional additives of lithium nitrate.

The applicant states that the process of the invention is illustrated by the above examples, but the invention is not limited to, i.e. does not mean that the invention must be carried out in dependence on the above process steps. It should be apparent to those skilled in the art that any modification of the present invention, equivalent substitution of selected raw materials, addition of auxiliary components, selection of specific modes, etc. fall within the scope of the present invention and the scope of disclosure.

Claims

1. A nonaqueous electrolyte characterized in that the nonaqueous electrolyte comprises a lithium salt, a solvent, a cosolvent, a diluent and an additive;

2. The nonaqueous electrolytic solution according to claim 1, wherein the nitrate-based compound comprises any one or a combination of at least two of isosorbide nitrate, glycerin 1, 3-dinitrate, propylene glycol dinitrate, diethylene glycol dinitrate, ethylene glycol dinitrate, [13C6] -isosorbide dinitrate, and 3- (2-methoxyphenoxy) propane-1, 2-dinitrate;

preferably, the nitrate compound comprises any one of 3- (2-methoxyphenoxy) propane-1, 2-dinitrate, [13C6] -isosorbide dinitrate, ethylene glycol dinitrate or diethylene glycol dinitrate;

3. The nonaqueous electrolytic solution according to claim 1 or 2, wherein the content of the additive is 0.1 to 10wt.%, preferably 0.5 to 7.5wt.%, based on 100% of the total mass of the nonaqueous electrolytic solution.

4. The nonaqueous electrolytic solution according to any one of claims 1 to 3, wherein the diluent comprises a perfluoroalkane compound;

preferably, the perfluoroalkanes include any one or a combination of at least two of C5-18-perfluoro-alkane, perfluoro-mixture FC-40, perfluoro-octane, perfluoro-nonane, perfluoro-hexane, perfluoro-decane, perfluoro-butane, perfluoro-n-pentane, perfluoro-hexadecane, perfluoro-cyclopentane, perfluoro-tetradecane, perfluoro-dodecane, perfluoro-n-heptane, perfluoro-pentadecane, perfluoro-cyclohexane, perfluoro-tridecane, perfluoro-tetracosane, perfluoro-butylethane, perfluoro-eicosane, perfluoro-hexylethane, perfluoro (methylcyclohexane), perfluoro-hexyloctane, perfluoro-butylcyclohexane, perfluoro-methylcyclopentane, perfluoro-dimethylcyclobutane, perfluoro-2, 7-dimethyloctane, perfluoro-1, 2-dimethylcyclohexane, perfluoro-2, 3-tetramethylbutane, perfluoro-2-methyl-2, 3-epoxypentane or perfluoro-1, 3, 5-trimethylcyclohexane, preferably perfluoro (methylcyclohexane), perfluoro (dimethylcyclohexane) or a combination of at least one of perfluoro-1, 3, 5-trimethylcyclohexane.

5. The nonaqueous electrolyte according to any one of claims 1 to 4, wherein the cosolvent comprises a cyclophosphazene-based solvent;

6. The nonaqueous electrolytic solution according to any one of claims 1 to 5, wherein the lithium salt comprises lithium bis-fluorosulfonyl imide or lithium bis-trifluoromethanesulfonyl imide;

preferably, the concentration of the lithium salt is 1 to 3.5mol/L.

7. The nonaqueous electrolytic solution according to any one of claims 1 to 6, wherein the solvent comprises an ether-based solvent;

8. The nonaqueous electrolyte according to any one of claims 1 to 7, wherein the volume ratio of the solvent, the cosolvent and the diluent is (0.5 to 4): (0.1 to 2): (5 to 9), preferably (1 to 3): (0.5 to 1.5): (5.5 to 8.5).

9. A lithium metal battery characterized in that the lithium metal battery comprises a positive electrode, a negative electrode and an electrolyte comprising the nonaqueous electrolyte according to any one of claims 1 to 8.

10. The lithium metal battery of claim 9, wherein the material of the negative electrode comprises lithium metal.