PREPARATION METHOD OF FLAME-RETARDANT LITHIUM-ION BATTERY ELECTROLYTE EASILY SOLUBLE IN ORGANIC SOLVENT

Abstract

A lithium salt easily soluble in an organic solvent and having a flame-retardant function and a lithium-ion battery flame-retardant electrolyte thereof are provided. The lithium salt is poly(lithium phosphate) phosphazene partially substituted by alkyl aromatic oxy groups, and has a structural general formula: [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x]. The novel flame-retardant electrolyte is compounded from the lithium salt and a phosphate intermediate thereof [(R—Ar—O).sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x] according to a mass ratio of 10:1-1:1. The electrolyte is easily soluble in an organic solvent. A liquid electrolyte is prepared according to an amount of 8%-45% to obtain the novel flame-retardant liquid electrolyte. The liquid electrolyte has good lithium ion conductivity and good flame-retardant properties, and is used in lithium-ion batteries, lithium-sulfur batteries, lithium carbon fluoride batteries or lithium-oxygen batteries.

Claims

1. A preparation method of a flame-retardant lithium-ion battery electrolyte easily soluble in an organic solvent, wherein a lithium salt with a structural general formula [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x] is a lithium salt easily soluble in the organic solvent and having a flame-retardant function, the lithium salt is poly(lithium phosphate) phosphazene partially substituted by alkyl aromatic oxy groups, and since a molecule of the lithium salt has a large number of aromatic groups, a solubility of the lithium salt in an organic solvent is improved; the solubility of the lithium salt in the organic solvent is regulated by controlling an amount of substitution of the alkyl aromatic oxy groups in the molecule; due to the presence of aromatic rings, a compatibility of the lithium salt with an electrode material is improved; since the molecule contains lots of lithium ions that are releasable by ionization, the lithium salt has a good lithium ion conductivity; since the molecule contains a polyphosphazene group and a phosphate group with good flame-retardant properties, the lithium salt has good flame-retardant properties; the lithium salt is compounded with a phosphate intermediate thereof having a formula of [(R—Ar—O).sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x]) to obtain the flame-retardant lithium-ion battery electrolyte; and wherein the preparation method a comprises the following steps: 1) heating a raw material hexachlorocyclotriphosphazene (HCCP) at 210-250° C. in a high-boiling-point solvent to carry out a ring-opening polymerization to obtain poly(dichlorophosphazene) (PDCP), dissolving the PDCP in a specific solvent, and carrying out a reaction with a certain amount of triphosphite at 100-120° C. to obtain partially phosphated poly(chloro(dialkoxyphosphate)phosphazene) [Cl.sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x]; reacting the [Cl.sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x] with alkyl aromatic phenolate sodium (R—Ar—ONa) to obtain [(R—Ar—O).sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x], and hydrolyzing the [(R—Ar—O).sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x] under alkaline conditions of lithium hydroxide to obtain [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x]; or carrying out a hydrolysis under conditions of sodium hydroxide to obtain [(R—Ar—O).sub.x(P═N).sub.n(Na.sub.2O.sub.3P).sub.2n-x], carrying out an ion exchange on the [(R—Ar—O).sub.x(P═N).sub.n(Na.sub.2O.sub.3P).sub.2n-x] with a cation exchange resin to obtain [(R—Ar—O).sub.x(P═N).sub.n(H.sub.2O.sub.3P).sub.2n-x], and carrying out a neutralization reaction with the lithium hydroxide to obtain [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x]; 2) compounding and mixing the [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x] with [(R—Ar—O).sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x] according to a certain ratio to obtain a mixture, and dissolving the mixture in the organic solvent to obtain an additive of the flame-retardant lithium-ion battery electrolyte; 3) adding the additive of the flame-retardant lithium-ion battery electrolyte obtained in step 2) to a commercially available liquid electrolyte with no flame retardant and lithium salt added originally to obtain the flame-retardant lithium-ion battery electrolyte; wherein the flame-retardant lithium-ion battery electrolyte has good flame-retardant properties, higher lithium-ion conductivity and better compatibility with electrodes; a battery assembled with the flame-retardant lithium-ion battery electrolyte has better battery performance, and higher flame-retardant properties and safety performance; and the flame-retardant lithium-ion battery electrolyte is used as an electrolyte for lithium-ion batteries, lithium-oxygen batteries and lithium-sulfur batteries.

2. The preparation method according to claim 1, wherein the high-boiling-point solvent used in the ring-opening polymerization of the HCCP is one or a mixture of several solvents selected from the group consisting of an aromatic solvent oil, diphenyl ether, sulfolane, glyceryl triacetate, pentaerythritoltetraacetate, polyethylene glycol diacetate, liquid paraffin and methylnaphthalene oil, wherein the high-boiling-point solvent is a solvent having a boiling point of higher than 220° C. and stable to the hexachlorocyclotriphosphazene and the poly(dichlorophosphazene).

3. The preparation method according to claim 1, wherein the poly(dichlorophosphazene) has a viscosity average molecular weight of 40,000-100,000 Da.

4. The preparation method according to claim 1, wherein the triphosphite is one or a mixture of several compounds selected from the group consisting of trimethylphosphite, triethylphosphite, tripropylphosphite and triisopropylphosphite, wherein an alcohol generated by the hydrolysis reaction has a low boiling point and is easily removed by evaporation; and a mass G of the PDCP is calculated according to G/232 to obtain a number of moles of an element chlorine in the PDCP, and a molar ratio of the number of moles of the element chlorine to phosphite is 4:1-1:4.

5. The preparation method according to claim 1, wherein the specific solvent used to dissolve the PDCP in the reaction between the PDCP and the triphosphite is toluene, xylene, tetrachloroethylene or dioxane; wherein the specific solvent has good solubility to the PDCP and the triphosphite, and is inert and unreactive to the PDCP and the triphosphite.

6. The preparation method according to claim 1, wherein R in the aromatic phenolate (R—Ar—ONa) is one selected from the group consisting of C.sub.1-C.sub.8 alkyl, disubstituted C.sub.1-C.sub.8 alkyl and CH.sub.2═CH—(CH.sub.2).sub.n— (n=1-6); and Ar is one or more selected from the group consisting of ph-, -ph-, naphthyl, disubstituted naphthyl, furyl, pyridyl, pyrazinyl, thienyl, imidazolyl and benzimidazolyl.

7. The preparation method according to claim 1, in step 2, wherein a mass ratio of the [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x] to the [(R—Ar—O).sub.x(P═N).sub.n—(R′.sub.2O.sub.3P).sub.2n-x] is 10:1-1:1; and the organic solvent used is one or a mixture of several solvents selected from the group consisting of methyl carbonate, ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethylsulfoxide, dimethylformamide, dimethylacetamide and N-methylpyrrolidone.

8. The preparation method according to claim 1, in step 3, wherein a mass percentage of the additive of the flame-retardant lithium-ion battery electrolyte compounded from the [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x] and the [(R—Ar—O).sub.x(P═N).sub.n—(R′.sub.2O.sub.3P).sub.2n-x] added to the commercially available electrolyte is 8%-45%.

Description

DETAILED DESCRIPTION

[Example 1]: Preparation of poly(dichlorophosphazene)

[0039] Under the protection of nitrogen, sulfamic acid (0.52 mmol, 0.05 g), hexachlorocyclotriphosphazene (HCCP) (14.4 mmol, 5 g) and a solvent diphenyl ether (15-30 mL) were respectively added into a three-necked flask equipped with a stirrer and a condenser pipe. After introducing nitrogen for 20-40 min, the mixture was stirred and heated to 210-250° C. to carry out ring-opening polymerization reaction. When the solution became viscous, heating was stopped, the mixture was cooled and poured into a beaker containing 40-60 mL of petroleum ether to remove the unreacted raw material HCCP, the mixture was washed with petroleum ether three times, suction filtration was carried out, and the obtained solid product was dried in a vacuum drying oven at 70-90° C. for 4-8 h to obtain poly(dichlorophosphazene) (PDCP). The obtained PDCP had a yield of 70% and a viscosity average molecular weight of 60000-80000.

[0040] By using the above method, the ring-opening polymerization product may also be obtained by replacing the diphenyl ether with other solvents (one or a mixture of several of aromatic solvent oil, sulfolane, glyceryl triacetate, pentaerythritoltetraacetate, polyethylene glycol diacetate, liquid paraffin and methylnaphthalene oil) and by controlling the temperature at 210-250° C. or a higher reaction temperature, only except that the solvent would be removed by washing the solvent using a low-boiling-point solvent with better solubility for the solvent.

[0041] The yield of the ring-opening polymerization reaction using different solvents was in the range of 40%-80%, and the viscosity average molecular weight was in the range of 40000-100000.

[Example 2]: Preparation of poly(chloro(dialkoxyphosphate)phosphazene) [Cl.SUB.x.(P═N).SUB.n.(R′.SUB.2.O.SUB.3.P).SUB.2n-x.]

[0042] The poly(dichlorophosphazene) (23.2 g) with an element chlorine content of 0.1 mol and 0.1 mol of triethylphosphite (16.6 g) were respectively weighed and respectively dissolved in 100 mL of xylene (dried). The two solutions were mixed in a three-necked flask equipped with a stirrer, a condenser pipe and a heating device under stirring, stirred and reacted at 100-120° C. for 5-7 h. After the solvent was removed by evaporation, the reaction mixture was washed with an appropriate amount of petroleum ether 3-4 times to remove impurities, suction filtration was carried out, and the solid was dried in a vacuum drying oven at 60-100° C. to obtain a solid powder product [Cl.sub.n(P═N).sub.n(Et.sub.2O.sub.3P).sub.n].

[0043] [Cl.sub.x(P═N).sub.n(Et.sub.2O.sub.3P).sub.2n-x] could be obtained by using different molar ratios of raw materials.

[0044] Using the same method above, other phosphate compounds [Cl.sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x] could be obtained by replacing ethyl phosphite with other phosphites (one or a mixture of several of trimethylphosphite, tripropylphosphite or triisopropylphosphite).

[Example 3]: Synthesis of Intermediate [(i-C.SUB.3.H.SUB.7.-ph-O).SUB.x.(P═N).SUB.n.(Et.SUB.2.O.SUB.3.P).SUB.2n-x.]

[0045] In a three-necked flask equipped with electric stirrer and a condenser pipe under the protection of nitrogen, 0.1 mol (21.75 g) of the [Cl.sub.n(P═N).sub.n(Et.sub.2O.sub.3P).sub.n] in the experiment of (2) above was dissolved in tetrahydrofuran, the solution was slowly added dropwise to 0.11 mol (17.38 g) of p-isopropyl-phenolate sodium in tetrahydrofuran, and the mixture was stirred at 80° C. to react for 24 h. After the completion of the reaction, the reaction mixture was cooled and neutralized with glacial acetic acid to neutrality, the mixture was stood and cooled in an ice water bath to separate a crystal, suction filtration was carried out, and the obtained crude product was recrystallized with tetrahydrofuran to obtain the pure product white crystal [(i-C.sub.3H.sub.7-ph-O).sub.n(P═N).sub.n(Et.sub.2O.sub.3P).sub.n].

[0046] Using the same method, different structures of [(i-C.sub.3H.sub.7-ph-O).sub.x(P═N).sub.n(Et.sub.2O.sub.3P).sub.2n-x] could be obtained by selecting different mass ratios.

[0047] Using the above method, other phenolates may be used instead of alkylphenylphenolate (the other phenolates were: R in the aromatic phenolate (R—Ar—ONa) was C.sub.1-C.sub.8 alkyl, disubstituted C.sub.1-C.sub.8 alkyl or CH.sub.2═CH—(CH.sub.2).sub.n— (n=1-6); and Ar was one or a mixture of several of ph-, -ph-, naphthyl, disubstituted naphthyl, furyl, pyridyl, pyrazinyl, thienyl, imidazolyl and benzimidazolyl.) to react with intermediates reactive to other phosphites to obtain intermediates [(R—Ar—O).sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x] substituted by other phenolates and substituted by other phosphites.

[Example 4]: Preparation of Novel Flame-Retardant Lithium Salt [(R—Ar—O).SUB.x.(P═N).SUB.n.(Li.SUB.2.O.SUB.3.P).SUB.2n-x.]

[0048] [Method I] Hydrolysis in Lithium Hydroxide Solution

[0049] According to the method, an excess of lithium hydroxide was needed. A certain amount of [(R—Ar—O).sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x] was weighed and dispersed in a 2 mol/L lithium hydroxide solution. The mixture was heated, stirred and refluxed for 24 h. After ethanol generated by the hydrolysis reaction was removed by evaporation, the mixture was concentrated, cooled and stood overnight to obtain a crude product. The crude product was recrystallized twice with an ethanol-water mixed solution to obtain a colorless crystal [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x]. The mother liquor uses a cation exchange resin to collect and recover lithium ions.

[0050] [Method II] Hydrolysis in Sodium Hydroxide Solution.

[0051] Method II was the same as Method I, except that: the lithium hydroxide solution was replaced by a sodium hydroxide solution to obtain the colorless crystal [(R—Ar—O).sub.x(P═N).sub.n(Na.sub.2O.sub.3P).sub.2n-x], and a solution prepared was exchanged with a cation exchange resin for 24 h to obtain [(R—Ar—O).sub.x(P═N).sub.n(H.sub.2O.sub.3P).sub.2n-x], and the acid structure was reacted with an equimolar amount of lithium hydroxide (or a slightly excess amount, the pH of the solution was 9-11) to obtain the colorless crystal [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x] product.

Example 4

[0052] Using the above method, other phenolates may be used instead of alkylphenylphenolate (the other phenolates were: R in the aromatic phenolate (R—Ar—ONa) was C.sub.1-C.sub.8 alkyl, disubstituted C.sub.1-C.sub.8 alkyl or CH.sub.2═CH—(CH.sub.2).sub.n— (n=1-6); and Ar was one or a mixture of several of ph-, -ph-, naphthyl, disubstituted naphthyl, furyl, pyridyl, pyrazinyl, thienyl, imidazolyl and benzimidazolyl.) to obtain products substituted by other phenolates.

[0053] Preparation process conditions, yields, solubilities, flame-retardant properties, conductivities and other data of various lithium salts are shown in Table 1.

[Example 5]: Research of Compounding Process of Electrolyte

[0054] The [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n-x] was mixed and compounded with the [(R—Ar—O).sub.x(P═N).sub.n(R′.sub.2O.sub.3P).sub.2n-x] according to a mass ratio of 10:1-1:1; and the mixture was dissolved in a suitable organic solvent. The solvent used was as follows: one or a mixture of several of methyl carbonate, ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dim ethyl sulfoxide, dimethylformamide, dimethylacetamide and N-methylpyrrolidone was used as the solvent of the electrolyte. The solution in which the novel flame-retardant electrolyte was dissolved was used as the additive of the novel flame-retardant lithium-ion battery electrolyte.

[Example 6]: Preparation of Liquid Electrolyte

[0055] According to the novel flame-retardant electrolyte additive obtained in Example (5), a series of lithium-ion battery additives were added, for example: an anti-overcharge additive, such as one or a mixture of several of diacetylferrocene, transition metal complex of bipyridine, terpyridine or o-phenanthroline, anisole, cyclohexylbenzene and N-phenylmaleimide, with a mass percentage of 6%-25%; and an additive that promotes formation of an SEI, such as one or mixture of several of fluoroethylene carbonate, fluoropropylene carbonate, nonafluorobutyl ethyl ether, butane sultone, 1,3-propane sultone, vinyltrimethoxysilane, 2-phenylimidazole and 4-fluorophenylisocyanate, with a mass percentage of 4%-20%.

[Example 7]: Performance Test of Liquid Electrolyte

[0056] The liquid electrolyte was tested for various physical and chemical performance indicators, such as flame-retardant properties, lithium-ion conductivity and other properties. The formula and compounding process of the liquid electrolyte were improved through the performance test to seek for a preparation process of a liquid electrolyte with more excellent performances.

[0057] Various liquid electrolyte formulae and compounding processes as well as test results such as viscosity, flame-retardant properties, conductivity and the like are shown in Table 2.

[Example 8]: Assembly and Performance Test of Lithium-Ion Battery

[0058] The battery assembled with the novel flame-retardant liquid electrolyte was tested for battery performance, initial power generation performance, charge and discharge performance at different rates, cycle stability, battery overheating resistance, puncture resistance, anti-overcharge performance and the like.

[Example 9]: Assembly and Performance Test of Lithium-Sulfur Battery

[Example 10]: Assembly and Performance Test of Lithium-Oxygen Battery

[0059] The lithium-sulfur battery and the lithium-oxygen battery assembled with the novel flame-retardant liquid electrolyte were respectively tested for battery performance. Various aspects of performance of the novel flame-retardant liquid electrolyte were investigated.

[0060] The performance of various batteries assembled with different liquid electrolytes are shown in Table 2.

TABLE-US-00001 TABLE 1 Composition, yield, solubility, conductivity and flame-retardant properties of lithium salt [(R—Ar—O).sub.x(P═N).sub.n(Li.sub.2O.sub.3P).sub.2n−x] Relationship Limiting between Conductivity Oxygen Fire Rating R Ar n and x Yield Solubility (S/cm) Index (LOI) (UL-94) Me R—Ph— n = x 73% 31% 0.025 41 Non-combustible Et [00004] n > x 78% 34% 0.034 42 Non-combustible n-Pr [00005] n < x 82% 39% 0.030 44 Non-combustible i-Pr [00006] n > x 75% 33% 0.036 42 Non-combustible n-Bu [00007] n = x 72% 38% 0.038 42 Non-combustible i-Bu [00008] n < x 71% 42% 0.030 45 Non-combustible s-Bu [00009] n > x 83% 33% 0.042 42 Non-combustible CH.sub.2═CH(CH.sub.2).sub.3— [00010] n = x 81% 40% 0.041 43 Non-combustible CH.sub.2═CH(CH.sub.2).sub.4— [00011] n > x 84% 35% 0.045 42 Non-combustible n-Pr [00012] n < x 85% 45% 0.029 46 Non-combustible CH.sub.3(CH.sub.2).sub.6CH.sub.2— [00013] n > x 74% 35% 0.046 45 Non-combustible CH.sub.3(CH.sub.2).sub.5CH.sub.2— [00014] n = x 80% 41% 0.038 43 Non-combustible n-Bu [00015] n > x 83% 36% 0.048 42 Non-combustible CH.sub.3(CH.sub.2).sub.6CH.sub.2— [00016] n = x 85% 45% 0.051 41 Non-combustible CH.sub.2═CH(CH.sub.2).sub.4— [00017] n = x 82% 43% 0.043 42 Non-combustible

TABLE-US-00002 TABLE 2 Formula, conductivity, flame-retardant properties of liquid electrolyte and battery performance Lithium-oxygen Flame-retardant Lithium-ion Battery .sup.# Battery Properties First Lithium-sulfur Battery .sup.& First Limiting Discharge First Discharge Oxygen Fire Capacity Coulombic D.sub.Li Discharge Coulombic Capacity Conductivity Index Rating (0.1 C., Efficiency Value LSV Capacity Efficiency Capacity (0.1 C., Formula * (S/cm) (LOI) (UL-94) mAh/g) (%) (cm.sup.2/s) (V) (0.1 C., mAh/g) (%) Retention mAh/g) 1 0.032 40 Non- 198 96% 3.37 × 10.sup.−9 5.1 1045 98 80% 3210 combustible 2 0.028 42 Non- 206 97% 4.28 × 10.sup.−9 5.2 1124 99 89% 2106 combustible 3 0.036 42 Non- 210 97% 5.34 × 10.sup.−9 5.2 1213 99 90% 3697 combustible 4 0.031 40 Non- 213 98% 4.02 × 10.sup.−9 5.2 1138 99 90% 3287 combustible 5 0.026 41 Non- 185 97% 2.01 × 10.sup.−9 5.0 1012 98 89% 2396 combustible 6 0.041 42 Non- 225 98% 6.78 × 10.sup.−9 5.2 1326 99.5 91% 5102 combustible NOTE * Formula of liquid electrolyte: 1: The lithium salt was [(n-Bu-ph-O).sub.n(P═N).sub.n(Li.sub.2O.sub.3P) .sub.n], the ester intermediate was (n-Bu-ph-O).sub.n(P=N).sub.n((C.sub.2H.sub.5).sub.2O.sub.3P) .sub.n], and the mass ratio of the two was 5:1. The organic solvent was a mixture of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethylsulfoxide, dimethylacetamide and N-methylpyrrolidone, with a mass percentage of 30%. The other additives and mass percentages thereof were respectively: 3% diacetylferrocene, 3% anisole, 2% butane sultone, 2% 1,3-propane sultone and 5% 2-phenylimidazole. [00018]The mass ratio of the two was 6:1. The organic solvent was a mixture of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethylsulfoxide, dimethylacetamide and N-methylpyrrolidone, with a mass percentage of 35%. The other additives and mass percentages thereof were respectively: 4% di acetyl ferrocene, 3% transition metal complex of o-phenanthroline, 2% butane sultone, 3% nonafluorobutyl ethyl ether and 4% vinyltrimethoxysilane. [00019]The mass ratio of the two was 7:1. The organic solvent was a mixture of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethylsulfoxide, dimethylacetamide and N-methylpyrrolidone, with a mass percentage of 36%. The other additives and mass percentages thereof were respectively: 2% di acetyl ferrocene, 4% N-phenylmaleimide, 3% butane sultone, 3% 1,3-propane sultone and 4% 4-fluorophenylisocyanate. [00020]The mass ratio of the two was 4:1. The organic solvent was a mixture of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethylsulfoxide, dimethylacetamide and N-methylpyrrolidone, with a mass percentage of 37%. The other additives and mass percentages thereof were respectively: 4% di acetyl ferrocene, 3% anisole, 4% butane sultone, 3% vinyltrimethoxysilane and 4% 2-phenylimidazole. [00021]The mass ratio of the two was 10:1. The organic solvent was a mixture of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethylsulfoxide, dimethylacetamide and N-methylpyrrolidone, with a mass percentage of 30%. The other additives and mass percentages thereof were respectively: 4% diacetylferrocene, 5% nonafluorobutyl ethyl ether, 3% butane sultone, 3% vinyltrimethoxysilane and 4% 2-phenylimidazole. [00022]The mass ratio of the two was 5:1. The organic solvent was a mixture of ethyl carbonate, propyl carbonate, ethylene carbonate, fluoroethylene carbonate, dimethylsulfoxide, dimethylacetamide and N-methylpyrrolidone, with a mass percentage of 34%. The other additives and mass percentages thereof were respectively: 4% di acetyl ferrocene, 2% anisole, 3% butane sultone, 4% 1,3-propane sultone and 2% 2-phenylimidazole. .sup.# Lithium-ion battery A commercial ternary lithium-ion battery was used, and the liquid electrolyte was the liquid electrolyte of the invention. The battery performance was tested according to GB/T18287. .sup.& Lithium-sulfur batteryLithium-sulfur battery capacity retention test: 10 cycles at 1 C..

[0061] Safety Performance of Batteries

[0062] The safety performance of all the batteries were better than that using the commercial liquid electrolyte under various test conditions. For example, the batteries of the invention did not become swollen in water; the temperature resistance could be increased to 80-100° C.; and the puncture resistance, compression resistance and bending resistance were greatly improved.