A lithium-ion battery electrolyte and a lithium-ion battery using the electrolyte

Abstract

This invention relates to a lithium-ion battery electrolyte and a lithium-ion battery using the electrolyte. To address the problems of poor cycle performance and low safety performance of existing lithium batteries at high voltages, this invention provides a lithium-ion battery electrolyte comprising a lithium salt, additives, and a non-aqueous organic solvent. The lithium salt is lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide, and the additives include tripyridyl phosphate compounds. Based on the combination of tripyridyl phosphate compounds and lithium salts, the cycle performance, overcharge capability, and high-temperature storage performance of the high-voltage battery are significantly improved simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a lithium-ion battery electrolyte and a lithium-ion battery using the electrolyte. Background Technology

[0002] In recent years, to meet the requirements of long-range portable electric devices, lithium-ion rechargeable batteries have been developing towards higher energy densities. Increasing battery energy density primarily focuses on increasing battery capacity and reducing battery weight. With key materials such as copper and aluminum foil already reaching thicknesses of around 10 μm, further reductions have become increasingly difficult. Therefore, increasing battery capacity has become a crucial research direction, primarily through raising the battery's operating voltage. However, as the operating voltage increases, a series of problems that were not severe in low-voltage systems become more prominent in high-voltage systems. For example, at high voltages, the electrolyte oxidizes, transition metal oxide ions precipitate in the electrode materials, and metal dendrites form on the negative electrode. Therefore, the requirements for materials and electrolytes are becoming increasingly stringent.

[0003] The selection of solvents or additives has become one of the important means to solve the above problems. A suitable solvent can improve the oxidative stability of the entire electrolyte system, thereby reducing or minimizing side reactions in the electrolyte, thus improving the overall stability of the electrolyte. Furthermore, reducing oxidation reactions also reduces electrolyte decomposition, ensuring the electrolyte's sufficiency during cycling and thus extending battery life. Selecting one or more sacrificial additives can pre-decompose the electrolyte on the surface of the positive electrode before it decomposes, forming a film that prevents side reactions between the electrolyte and the positive electrode, thus hindering further electrolyte decomposition and extending battery life.

[0004] With the increase in the operating voltage of lithium batteries, higher requirements are placed on the cycle performance, high-temperature performance and safety performance of electrolytes under high voltage. It is necessary to develop more electrolyte additives to work with other components in the electrolyte to overcome or alleviate the problems encountered in high-voltage battery systems under existing technology conditions. Summary of the Invention

[0005] The purpose of this invention is to provide an electrolyte that can simultaneously meet the requirements of long cycle life and high safety of lithium-ion batteries under high voltage.

[0006] The purpose of this invention is to provide a lithium-ion battery with long cycle life and high safety performance.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A lithium-ion battery electrolyte comprises a lithium salt, additives, and a non-aqueous organic solvent, wherein the additives include one or more of the tripyridyl phosphite compounds shown in Formula 1.

[0009]

[0010] Among them, R1~R 12 Independently selected from hydrogen atom, halogen atom, cyano group, amino group, nitro group, silyl group, unsubstituted or substituted C1 to C1 atoms. 10 Alkyl, unsubstituted or substituted C2-C 10 Alkenyl, unsubstituted or substituted C6-C 14 aryl, unsubstituted or substituted C1-C 14 Alkoxy, unsubstituted or substituted C6-C 14 The aryloxy group, wherein the substituent of any substitution is F, Cl, Br or cyano.

[0011] Preferably, R1~R 12 The substituent is independently selected from hydrogen atom, halogen atom, cyano, amino, nitro, silyl, unsubstituted or substituted C1-C4 alkyl, unsubstituted or substituted C2-C4 alkenyl, unsubstituted or substituted C6-C8 aryl, unsubstituted or substituted C1-C4 alkoxy, unsubstituted or substituted C6-C8 aryloxy, wherein the substituted substituent is F, Cl or cyano.

[0012] Preferably, R1~R 12 It is independently selected from hydrogen atoms, halogen atoms, cyano, nitro, F-substituted C1-C4 alkyl or unsubstituted C2-C4 alkenyl groups.

[0013] More preferably, R1~R 12 It is independently selected from hydrogen atom, halogen atom, cyano, nitro, trifluoromethyl or vinyl.

[0014] Preferably, R1~R 12 Not all of them are hydrogen atoms.

[0015] According to some embodiments, the additive includes one or more compounds represented by the following structural formulas:

[0016]

[0017]

[0018] Preferably, the mass of the additive is 0.1% to 20% of the total mass of the lithium-ion battery electrolyte.

[0019] More preferably, the mass of the additive is 0.1% to 15% of the total mass of the lithium-ion battery electrolyte.

[0020] More preferably, the mass of the additive is 3-15% of the total mass of the lithium-ion battery electrolyte.

[0021] More preferably, the mass of the additive is 3 to 10% of the total mass of the lithium-ion battery electrolyte.

[0022] Preferably, the lithium salt is lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide.

[0023] LiPF6 suffers from poor thermal stability and is prone to hydrolysis, which can cause rapid capacity decay and safety hazards. The new lithium salt lithium bisfluorosulfonyl imide (LiFSI) has the characteristics of good thermal stability, high conductivity and excellent thermodynamic stability, which can make up for the shortcomings of LiPF6 and improve the performance of batteries to a certain extent.

[0024] Preferably, the concentration of the lithium salt is 0.5 to 2.5 mol / L.

[0025] More preferably, the concentration of the lithium salt is 0.8–2.0 mol / L.

[0026] More preferably, the concentration of the lithium salt is 0.8–1.5 mol / L.

[0027] Preferably, the non-aqueous organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, ethylene carbonate, propylene carbonate, vinylene carbonate, ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, and γ-butyrolactone.

[0028] More preferably, the non-aqueous organic solvent is a mixture of dimethyl carbonate (DMC), ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC).

[0029] More preferably, the mass ratio of dimethyl carbonate (DMC), ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) is 1–3:2–4:1:3–5.

[0030] Preferably, the additive further includes one or more of the following: fluoroethylene carbonate (FEC), ethylene sulfate (DTD), propylene sulfate, vinylene carbonate (VC), 1,3-propane sulpholactone (PST), succinic anhydride, glutaric anhydride (GA), adiponitrile (ADN), succinic anhydride (SN), tris(trimethylsilane) phosphate (TMSP), tris(2,2,2-trifluoroethyl) phosphite, tris(trimethylsilane) borate (TMSB), or triphenyl phosphite (TPP).

[0031] The lithium-ion battery provided by the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is the lithium-ion battery electrolyte.

[0032] Preferably, the positive electrode active material of the positive electrode sheet is Li2CoO3 and / or Li2MnO3.

[0033] Preferably, the negative electrode sheet includes a negative electrode active material capable of accepting or releasing lithium ions, and the negative electrode active material includes one or more of lithium metal, lithium alloy, crystalline carbon, amorphous carbon, carbon fiber, hard carbon, or soft carbon.

[0034] More preferably, the crystalline carbon includes one or more of natural graphite, graphitized coke, graphitized MCMB, and graphitized mesophase pitch carbon fiber.

[0035] More preferably, the lithium alloy comprises an alloy of lithium and one or more of aluminum, zinc, silicon, tin, gallium, or antimony.

[0036] Preferably, the charging cutoff potential of the lithium-ion battery is not lower than 4.35V.

[0037] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0038] This invention, by adding a tripyridyl phosphite compound of Formula 1 to the electrolyte, effectively reduces the battery impedance in conjunction with other components in the electrolyte, significantly improving the battery's cycle performance. The tripyridyl phosphite compound can also form a thin and dense SEI film on the surfaces of the positive and negative electrodes, hindering the redox decomposition reaction of the electrode materials with the electrolyte. Furthermore, the tripyridyl phosphite compound can bind to transition metal ions dissolved in the electrolyte and free HF, preventing transition metal ions from electrodepositing on the negative electrode surface and avoiding damage to the SEI film by HF, thus improving the cycle and high-temperature performance of high-voltage lithium-ion batteries. In addition, the tripyridyl phosphite compound also has good flame-retardant properties, increasing battery safety. Further, by adjusting the lithium salt in the electrolyte, the battery's overcharge protection capability is improved, greatly enhancing the safety performance of the lithium battery. Detailed Implementation

[0039] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0040] In order to further improve the cycle performance and safety performance of high-voltage lithium-ion batteries, the inventors conducted a lot of research and experimental verification from the perspective of electrolyte, and finally proposed an electrolyte suitable for high-voltage lithium secondary batteries.

[0041] According to the present invention, the lithium-ion battery electrolyte comprises a lithium salt, additives, and a non-aqueous organic solvent, wherein the additives comprise one or more of the tripyridyl phosphite compounds shown in Formula 1.

[0042]

[0043] Among them, R1~R 12 Independently selected from hydrogen atom, halogen atom, cyano group, amino group, nitro group, silyl group, unsubstituted or substituted C1 to C1 atoms. 10 Alkyl, unsubstituted or substituted C2-C 10 Alkenyl, unsubstituted or substituted C6-C 14 aryl, unsubstituted or substituted C1-C 14 Alkoxy, unsubstituted or substituted C6-C 14 The aryloxy group, wherein the substituent of any substitution is F, Cl, Br or cyano.

[0044] The nitrogen atom in the pyridine ring structure of tripyridyl phosphite compounds possesses strong complexing ability, capable of binding transition metal ions dissolved in the electrolyte and free HF. This prevents transition metal ions from electrodepositing on the negative electrode surface and avoids HF damage to the SEI film, while also exhibiting advantages in improving battery safety. It shows promise for applications in high-voltage battery systems. The phosphite structure also reduces battery internal resistance and possesses certain flame retardancy, thereby enhancing battery safety performance.

[0045] According to some embodiments, R1~R 12 Preferably, it is independently selected from hydrogen atoms, halogen atoms, cyano groups, nitro groups, trifluoromethyl groups, or vinyl groups.

[0046] According to some embodiments, the non-aqueous organic solvent is a mixture of dimethyl carbonate (DMC), ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) in a mass ratio of 1–3:2–4:1:3–5.

[0047] According to some embodiments, the lithium salt is lithium hexafluorophosphate and / or lithium bisfluorosulfonylimide.

[0048] The preferred approach is to use lithium hexafluorophosphate (LiPF6) in combination with lithium bisfluorosulfonylimide (LiFSI). Because LiPF6 suffers from poor thermal stability and is prone to hydrolysis, it can easily lead to rapid capacity decay and safety hazards. The novel lithium salt LiFSI possesses advantages such as good thermal stability, high conductivity, and excellent thermodynamic stability, which can effectively compensate for the shortcomings of LiPF6 and improve battery performance to a certain extent. However, the cost of LiFSI is significantly higher than that of LiPF6; therefore, it is best to use the two in combination.

[0049] The electrolyte of this invention can be used in lithium secondary batteries with a charging cutoff potential greater than or equal to 4.35V, significantly improving the room temperature cycle performance, high temperature cycle performance, overcharge capability, and high temperature storage performance of lithium secondary batteries, and significantly enhancing safety performance.

[0050] The technical solutions and effects of the present invention will be further illustrated below with reference to embodiments and comparative examples.

[0051] The tripyridyl phosphite compounds involved in the following examples and comparative examples are as follows:

[0052]

[0053] Preparation route of tripyridyl phosphite (compound (1)): Polyethylene glycol is added to 4-hydroxypyridine, phosphorus trichloride is added dropwise during stirring, the reaction temperature is controlled at 75-85℃ under a pressure of about 800Pa, the reaction time is 4-6h, and after the reaction is completed, unreacted phosphorus trichloride is removed by atmospheric distillation to obtain tripyridyl phosphite.

[0054] Preparation route of compound (2): 2-vinylpyridine was mixed with ethyl acetate and stirred evenly at room temperature. Sulfoxide was added dropwise using a dropping funnel. After the addition was complete, the mixture was heated to reflux in an oil bath and stirred for 4 hours. The color of the mixture gradually changed from yellow to brown. After standing and separating into layers, the lower black solid was taken out, dried, and washed with anhydrous ethanol. Then it was dried again to obtain 4-hydroxy-2-vinylpyridine. Polyethylene glycol was added to 4-hydroxy-2-vinylpyridine. Phosphorus trichloride was added dropwise during stirring. The reaction temperature was controlled at 75-85℃ under a pressure of about 800 Pa for 4-6 hours. After the reaction was completed, unreacted phosphorus trichloride was removed by atmospheric distillation to obtain compound (2).

[0055] Preparation route of compound (3): Polyethylene glycol was added to 4-hydroxy-2-cyanopyridine (CAS 475057-86-4), phosphorus trichloride was added dropwise during stirring, the reaction temperature was controlled at 75-85℃ under a pressure of about 800Pa, the reaction time was 4-6h, and after the reaction was completed, unreacted phosphorus trichloride was removed by atmospheric distillation to obtain compound (3).

[0056] Preparation route of compound (4): Polyethylene glycol was added to 4-hydroxy-2-trifluoromethyl-3,5,6-trifluoropyridine (application number: PCT / JP2018 / 039843), and phosphorus trichloride was added dropwise while stirring. The reaction temperature was controlled at 75-85℃ under a pressure of about 800Pa, and the reaction time was 4-6h. After the reaction was completed, unreacted phosphorus trichloride was removed by atmospheric distillation to obtain compound (4).

[0057] Preparation route of compound (5): Polyethylene glycol was added to 4-hydroxy-3-nitro-2,6-dichloropyridine (application number: AU1958041193), phosphorus trichloride was added dropwise while stirring, the reaction temperature was controlled at 75-85℃ under a pressure of about 800 Pa, the reaction time was 4-6 h, and after the reaction was completed, unreacted phosphorus trichloride was removed by atmospheric distillation to obtain compound (5).

[0058] The preparation route of compound (6) (application number 202010878715.2): Sodium 3,5,6-trichloropyridin-2-ol was dissolved in water, and the temperature was raised to 70-75℃ while stirring. Hydrochloric acid was added dropwise to adjust the pH value to 2-4. After filtration, 2-hydroxy-3,5,6-trichloropyridinium was obtained. Toluene, a dehydrating agent, was added to 2-hydroxy-3,5,6-trichloropyridinium. The temperature was raised to 100℃-110℃ while stirring to carry out the dehydration reaction. After the dehydration reaction was completed, the temperature was lowered to 35℃-40℃, polyethylene glycol was added, and phosphorus trichloride was added dropwise while stirring. The reaction temperature was controlled at 75℃-85℃ under a pressure of about 800 Pa. After the reaction was completed, the unreacted phosphorus trichloride was distilled off under normal pressure, and the dehydrating agent toluene was distilled off under reduced pressure to obtain tri-(3,5,6-trichloropyridinium) phosphite, i.e., compound (6).

[0059] Unless otherwise specified, all raw materials used in the following examples and comparative examples are commercially available products.

[0060] Examples 1-24 and Comparative Examples 1-4

[0061] (1) Preparation of electrolyte

[0062] In an argon-atmospheric glove box (with water and oxygen content both less than 0.1 ppm), dimethyl carbonate (DMC), ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) were mixed in a mass ratio of 2:3:1:4, and then the electrolytes for the examples and comparative examples were prepared according to Table 1.

[0063] Table 1

[0064]

[0065]

[0066] (2) Preparation of positive electrode sheet

[0067] 3% by mass of polyvinylidene fluoride (PVDF) was dissolved in a 1-methyl-2-pyrrolidone solution. 94% by mass of Li2MnO3 and 3% by mass of conductive carbon black were added to the above solution and mixed evenly. The mixed slurry was coated on both sides of aluminum foil, dried, and rolled to obtain the positive electrode sheet.

[0068] (3) Preparation of negative electrode sheet

[0069] 4% by mass of SBR binder and 1% by mass of CMC thickener are dissolved in an aqueous solution. 95% by mass of graphite is added to the above solution and mixed evenly. The mixed slurry is then coated on both sides of a copper foil, dried, and rolled to obtain the negative electrode sheet.

[0070] (4) Manufacturing of lithium-ion batteries

[0071] The positive electrode, negative electrode, and separator prepared above are wound into a soft-pack battery cell, packaged with polymer, filled with the electrolyte prepared above, and then processed through formation and other processes to produce a lithium-ion battery with a capacity of 1500mAh.

[0072] (5) Battery performance test

[0073] Flammability test of electrolyte: Refer to the literature J. Electrochem. Soc., 2002, 149(5), A622 - A626. Glass wool balls with a diameter of 0.3 - 0.5 cm are made, and their weight is m1. Then the glass wool balls are fully immersed in the electrolyte to be tested, taken out and weighed as m2. The difference in the mass of the glass wool balls before and after immersion is the mass of the electrolyte absorbed by the balls. The glass wool ball is placed on a thin iron wire whose front section is folded into an "o" shape and ignited with an ignition device, and the time from ignition to flame extinction is recorded, which is called the self - extinguishing time (T1). Conventionally, the self - extinguishing time is calculated based on the self - extinguishing time per unit mass of the electrolyte, denoted as T, and thus the flame - retardant properties of different electrolyte flame - retardants can be compared; in this invention, all self - extinguishing times refer to the self - extinguishing time T per unit mass of the electrolyte. Each sample is measured three times and the average value is taken. T = T1 / (m2 - m1), and the test results of the self - extinguishing time are shown in Table 2.

[0074] Table 2 Self - extinguishing time of electrolyte

[0075]

[0076]

[0077] From the test results in Table 2, it can be seen that the self - extinguishing time of the examples is significantly shorter than that of the comparative examples, and at the same time, as the concentration of the additive increases, its self - extinguishing time gradually decreases, indicating that the additive provided by this invention, namely tripyridyl phosphite, plays a key role in improving the safety of the battery. Further, after adding LiFSI to the electrolyte system, the self - extinguishing time of the electrolyte also decreases.

[0078] Over - charge performance test: Take 50 lithium - ion batteries obtained from the above Examples 1 - 24 and Comparative Examples 1 - 4 respectively, charge them at a constant current of 1C and a constant voltage to 4.6V, with a cut - off current of 0.05C, and then over - charge the batteries at 1C for 1h to detect the state of the batteries. The results are shown in Table 3, where a qualified test battery does not show phenomena such as bulging (bulging rate < 10%), leakage, smoking, catching fire, or cracking.

[0079] Table 3 Test results of battery over - charge performance

[0080]

[0081]

[0082] As can be seen from the test results in Table 3, compared with Comparative Example 4, the addition of the additives provided by the present invention significantly improved the safety performance of the battery during 1C overcharging for 1 hour after full charge in Examples 1-24. When the additives provided by the present invention contain groups such as nitro and halogen atoms, the compounds exhibit more outstanding performance during battery overcharging. When LiFSI is added to the electrolyte system, the battery's overcharge protection capability is improved. Therefore, the combination of pyridyl phosphate compound and the two lithium salts greatly improves the safety performance of the battery.

[0083] Normal temperature cycle test conditions: The battery was subjected to 200 charge-discharge cycle tests in the voltage range of 3.0 to 4.6V at a charge-discharge rate of 1 / 1C, and the discharge capacity of the first cycle and the 200th cycle were recorded respectively.

[0084] Capacity retention rate at week 200 (%) = Discharge capacity at week 200 / Discharge capacity at week 1 * 100%.

[0085] High-temperature cycle test conditions: At 45℃, the battery was subjected to 100 charge-discharge cycles at a charge-discharge rate of 1 / 1C, and the discharge capacity of the first and 100th cycles was recorded.

[0086] Capacity retention rate at week 100 (%) = Discharge capacity at week 100 / Discharge capacity at week 1 * 100%.

[0087] High-temperature storage test conditions: First, the formed battery is charged and discharged once at 1C at room temperature, and the discharge capacity is recorded as Q1. Then, the battery is fully charged at 1C with a cutoff current of 0.05C. Before storage at 60℃ for 7 days, the battery thickness is measured and recorded as t1. After the high-temperature storage is completed and the battery has completely cooled down, the battery thickness is measured again and recorded as t2. Then, the battery is discharged at 1C and the discharge capacity is recorded as Q2.

[0088] Thickness change rate = (t2-t1) / t1*100%; Storage capacity retention rate = Q2 / Q1*100%.

[0089] The test results are shown in Table 4.

[0090] Table 4. Battery storage performance test results at room temperature, high temperature, and high temperature.

[0091]

[0092] As can be seen from Table 4, the batteries of Examples 1-24 are better than those of Comparative Examples 1-4 in terms of both room temperature and high temperature cycling performance. They also better suppress the increase in battery thickness in terms of high temperature storage and improve the battery capacity retention rate. This shows that the batteries containing the present invention have significantly improved high temperature storage performance and cycling performance.

[0093] Therefore, the additives provided by this invention greatly improve the safety performance, cycle performance, and high-temperature storage performance of high-voltage lithium batteries, resulting in excellent overall battery performance.

[0094] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A lithium-ion battery electrolyte, comprising a lithium salt, additives, and a non-aqueous organic solvent, characterized in that, The additives include one or more of the tripyridyl phosphite compounds shown in Formula 1. ， Among them, R1~R 12 Independently selected from hydrogen atom, halogen atom, cyano group, amino group, nitro group, silyl group, unsubstituted or substituted C1 to C1 atoms. 10 Alkyl, unsubstituted or substituted C2-C 10 Alkenyl, unsubstituted or substituted C6-C 14 aryl, unsubstituted or substituted C1-C 14 Alkoxy, unsubstituted or substituted C6-C 14 The aryloxy group, wherein the substituent of any substitution is F, Cl, Br or cyano. Alternatively, the additive is .

2. The lithium-ion battery electrolyte according to claim 1, characterized in that, R1~R 12 The substituent is independently selected from hydrogen atom, halogen atom, cyano, amino, nitro, silyl, unsubstituted or substituted C1-C4 alkyl, unsubstituted or substituted C2-C4 alkenyl, unsubstituted or substituted C6-C8 aryl, unsubstituted or substituted C1-C4 alkoxy, unsubstituted or substituted C6-C8 aryloxy, wherein the substituted substituent is F, Cl or cyano.

3. The lithium-ion battery electrolyte according to claim 2, characterized in that, R1~R 12 It is independently selected from hydrogen atoms, halogen atoms, cyano, nitro, F-substituted C1-C4 alkyl or unsubstituted C2-C4 alkenyl.

4. The lithium-ion battery electrolyte according to claim 3, characterized in that, R1~R 12 It is independently selected from hydrogen atom, halogen atom, cyano, nitro, trifluoromethyl or vinyl.

5. The lithium-ion battery electrolyte according to claim 1, characterized in that, The additives include one or more compounds shown in the following structural formulas: 、 、 、 、 。 6. The lithium-ion battery electrolyte according to claim 1, characterized in that, The additive is added at a mass of 0.1-20% of the total mass of the lithium-ion battery electrolyte.

7. The lithium-ion battery electrolyte according to claim 1, characterized in that, The lithium salt is lithium hexafluorophosphate and / or lithium bis(fluorosulfonyl)imide, and / or the concentration of the lithium salt is 0.5~2.5 mol / L.

8. The lithium-ion battery electrolyte according to claim 1, characterized in that, The non-aqueous organic solvent is selected from one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, methyl formate, ethylene carbonate, propylene carbonate, vinylene carbonate, ethyl acetate, ethyl propionate, methyl acetate, propyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, and γ-butyrolactone. And / or, the additives further include one or more of the following: fluoroethylene carbonate, ethylene sulfate, propylene sulfate, vinylene carbonate, 1,3-propane sulpholactone, succinic anhydride, glutaric anhydride, adiponitrile, succinic anhydride, tris(trimethylsilane) phosphate, tris(2,2,2-trifluoroethyl) phosphite, tris(trimethylsilane) borate, or triphenyl phosphite.

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

10. The lithium-ion battery according to claim 9, characterized in that, The positive electrode active material of the positive electrode sheet is Li2CoO3 and / or Li2MnO3; And / or, the negative electrode sheet includes a negative electrode active material capable of accepting or releasing lithium ions, the negative electrode active material including one or more of lithium metal, lithium alloy, crystalline carbon, amorphous carbon, carbon fiber, hard carbon or soft carbon; And / or, the charging cut-off potential of the lithium-ion battery is not lower than 4.35V.

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