Preparation method of lithium bis (catechol radical) borate

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a preparation method of lithium bis (catechol radical) borate. The preparation method of the bis (catechol radical) lithium borate comprises the following steps: S1, under a protective atmosphere, dissolving catechol and lithium tetrafluoroborate in a non-aqueous solvent, dropwise adding a siloxane auxiliary agent, and carrying out a heating reaction to obtain a mixed solution; and S2, the mixed solution is subjected to solvent removal and purification, and the lithium bis (catechol radical) borate is obtained. The preparation method of the lithium bis (catechol) borate is simple in step, mild in reaction condition, high in yield and high in product purity, and compared with an existing preparation method of the lithium bis (catechol) borate, no water phase participates, and the content of crystal water in the product can be reduced, so that the lithium bis (catechol) borate can be applied to a lithium ion battery; according to the electrolyte taking the lithium bis (catechol) borate as the additive, the wettability of a negative electrode interface to the electrolyte can be improved, and the battery performance is improved.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion batteries, and in particular to a method for preparing lithium bis(catecholyl)borate. Background Art

[0002] Introducing electrolyte additives is one of the cost-effective methods to improve battery stability and energy density. Through electrochemical redox, a stable solid electrolyte phase (SEI) is formed on the electrode, which can improve the electrochemical performance of the electrode. Among them, additives with boron as the central atom have been a hot topic in recent years. For example, lithium bis(oxalatoborate) (LiBOB) and lithium difluorooxalatoborate (LiDFOB) can form a stable SEI layer on the negative electrode to improve battery performance. However, the SEI layer formed by LiBOB has a large resistance, which hinders charge transfer at high rates; and the products produced by the LiDFOB reaction are mainly boron-containing oligomers, which may dissolve in subsequent cycles, thereby affecting the cycle stability of the battery. Therefore, it is urgent to develop new additives to improve the stability and energy density of the battery.

[0003] Lithium di(catecholate)borate (LiBBB), molecular formula C 12 H8BLiO4, the structural formula is shown in Formula I:

[0004]

[0005] Lithium di(catechol)borate was once considered as an electrolyte lithium salt for lithium-ion batteries because of its low cost and good thermal stability. However, lithium di(catechol)borate has poor oxidation stability and low ionic conductivity, and is difficult to be widely used as an electrolyte lithium salt in lithium-ion batteries. Currently, lithium di(catechol)borate is mainly prepared by the aqueous phase method, through the direct reaction of lithium hydroxide, boric acid and catechol in an aqueous medium. This method has a high yield, but the resulting product contains crystal water, which further limits its application in lithium-ion batteries. Summary of the invention

[0006] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, one of the purposes of the present invention is to provide a method for preparing lithium di(catecholyl) borate; the second purpose of the present invention is to provide an electrolyte; the third purpose of the present invention is to provide a lithium ion battery.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention provides a method for preparing lithium bis(catecholyl)borate, comprising the following steps:

[0009] S1. Under an inert atmosphere, dissolving catechol and lithium tetrafluoroborate in a non-aqueous solvent, adding a siloxane additive dropwise, and heating to react to obtain a mixed solution;

[0010] S2. The mixed solution is purified after the solvent is removed to obtain the lithium di(catecholate)borate.

[0011] In some embodiments of the present invention, the protective atmosphere includes nitrogen and an inert atmosphere.

[0012] In some embodiments of the present invention, the molar ratio of catechol, lithium tetrafluoroborate and siloxane additive is (1-3.5):1:(2-5).

[0013] In some specific embodiments of the present invention, the molar ratio of catechol, lithium tetrafluoroborate and siloxane additive is (1-2.5):1:(2-4.3).

[0014] In some embodiments of the present invention, the solid-to-liquid ratio of catechol to the non-aqueous solvent is 1 g:(4-10) mL.

[0015] In some specific embodiments of the present invention, the solid-to-liquid ratio of the catechol to the non-aqueous solvent is 1 g:(4.5-7.5) mL.

[0016] In some embodiments of the present invention, the non-aqueous solvent is selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, diethyl ether, tetrahydrofuran, dichloromethane, and n-hexane.

[0017] In some embodiments of the present invention, the dropping speed of the silicone additive is 0.1-0.2 mL / min.

[0018] In some embodiments of the present invention, the siloxane auxiliary agent is selected from at least one of trimethylchlorosilane, dimethyldichlorosilane, and hexamethyldisilazane.

[0019] In the present invention, a siloxane auxiliary agent is added to replace the fluorine atoms of lithium tetrafluoroborate, and at the same time, the chloride ions in the auxiliary agent are combined with the hydrogen of catechol to promote catechol to better connect with the boron atoms; the dripping method can accurately control the reaction rate and reduce the generation of by-products.

[0020] In some embodiments of the present invention, the temperature of the heating reaction is 25-80°C.

[0021] In some specific embodiments of the present invention, the temperature of the heating reaction is 50-80°C.

[0022] In some embodiments of the present invention, the heating reaction time is 3-9 hours.

[0023] In some specific embodiments of the present invention, the heating reaction time is 4-8 hours.

[0024] In some embodiments of the present invention, the solvent removal method comprises evaporation.

[0025] In some embodiments of the present invention, the purification method includes recrystallization.

[0026] In some embodiments of the present invention, the recrystallization solvent is selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, diethyl ether, tetrahydrofuran, dichloromethane, and n-hexane.

[0027] In some embodiments of the present invention, the purification specifically includes the following steps: dissolving the solid obtained after removing the solvent from the mixed solution, cooling and crystallizing, filtering, and drying to obtain the lithium di(catecholyl)borate.

[0028] In some embodiments of the present invention, the time of the cooling crystallization is 2-4 hours.

[0029] In some embodiments of the present invention, the drying temperature is 80-100°C.

[0030] In some embodiments of the present invention, the drying time is 10-12 hours.

[0031] In the present invention, a non-aqueous phase method is adopted to prepare lithium di(catecholyl)borate, which can significantly reduce the content of crystal water in lithium di(catecholyl)borate and create conditions for the application of lithium di(catecholyl)borate in lithium ion batteries.

[0032] A second aspect of the present invention provides an electrolyte, comprising an electrolyte additive and a basic electrolyte;

[0033] The electrolyte additive is lithium di(catecholate)borate obtained by the preparation method described in the first aspect of the present invention;

[0034] The basic electrolyte includes cyclic carbonate, linear carbonate and lithium salt.

[0035] In some embodiments of the present invention, the content of the electrolyte additive is 0.25%-1% of the mass of the basic electrolyte.

[0036] In some specific embodiments of the present invention, the content of the electrolyte additive is 0.25%-0.75% of the mass of the basic electrolyte.

[0037] In some embodiments of the present invention, in the basic electrolyte, the mass ratio of the cyclic carbonate to the linear carbonate is 1:(0.3-3).

[0038] In some specific embodiments of the present invention, in the basic electrolyte, the mass ratio of the cyclic carbonate to the linear carbonate is 1:(1-1.5).

[0039] In some embodiments of the present invention, the cyclic carbonate comprises ethylene carbonate (EC).

[0040] In some embodiments of the present invention, the linear carbonate is selected from at least one of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC).

[0041] In some embodiments of the present invention, in the basic electrolyte, the content of the lithium salt is 0.8-1.5 mol / L.

[0042] In some specific embodiments of the present invention, in the basic electrolyte, the content of the lithium salt is 0.8-1.2 mol / L.

[0043] In some embodiments of the present invention, the lithium salt is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium trifluoromethanesulfonate, lithium perchlorate, lithium hexafluoroarsenate, lithium trifluoromethylsulfonyl imide, and lithium perfluoroalkylsulfonyl imide.

[0044] In the present invention, it is found that lithium di(catecholyl)borate can be used as an electrolyte additive to effectively improve the stability and rate performance of the battery.

[0045] The third aspect of the present invention provides a lithium-ion battery, comprising the electrolyte described in the second aspect of the present invention.

[0046] In some embodiments of the present invention, the lithium-ion battery further includes a positive electrode sheet, a negative electrode sheet and a separator.

[0047] In some embodiments of the present invention, the positive electrode sheet comprises a lithium iron phosphate positive electrode sheet.

[0048] In some embodiments of the present invention, the negative electrode sheet comprises a graphite negative electrode sheet.

[0049] In some embodiments of the present invention, the separator comprises a polyethylene film.

[0050] In the present invention, the lithium di(catecholyl)borate prepared by the preparation method described in the first aspect of the present invention is added as an electrolyte additive to a basic electrolyte containing cyclic carbonate, linear carbonate and lithium salt, thereby obtaining a lithium ion battery electrolyte that can effectively improve the rate performance of the battery.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1) The preparation method of lithium di(catechol)borate provided by the present invention has simple steps, mild reaction conditions, high yield and high product purity. Compared with the existing preparation method of lithium di(catechol)borate, no water phase is involved, the content of crystal water in the product can be reduced, and lithium di(catechol)borate can be better applied to lithium ion batteries;

[0053] 2) The electrolyte provided by the present invention is a functional electrolyte with lithium di(catecholyl) borate as an additive, which can improve the wettability of the negative electrode interface to the electrolyte and improve the battery performance;

[0054] 3) The lithium ion battery provided by the present invention uses an electrolyte containing a lithium di(catecholyl) borate additive, and the rate performance of the battery is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 The NMR boron spectrum of the lithium bis(catecholyl)borate prepared in Example 1 is 11 B NMR;

[0056] Figure 2 The carbon NMR spectrum of the lithium di(catecholyl)borate prepared in Example 1 is 13 C NMR;

[0057] Figure 3 The Fourier transform infrared spectra of the lithium bis(catecholyl)borate prepared in Example 3 and Comparative Example 1;

[0058] Figure 4 Thermogravimetric analysis diagrams of lithium bis(catecholyl)borate prepared in Example 3 and Comparative Example 1;

[0059] Figure 5 The first charge and discharge curves of the lithium cobalt oxide / lithium half-cell corresponding to the electrolyte in Application Example 3 and Comparative Example 2;

[0060] Figure 6 The results of rate performance tests of the electrolytes in Application Example 3 and Comparative Example 1 corresponding to graphite / lithium half-cells. DETAILED DESCRIPTION

[0061] The present invention is further described in detail below by specific examples. Unless otherwise specified, the raw materials, reagents or devices used in the examples and comparative examples can be obtained from conventional commercial sources or can be obtained by prior art methods. Unless otherwise specified, the experiments or test methods are conventional methods in the art.

[0062] Example 1

[0063] In this example, lithium bis(catecholyl)borate is prepared by the following steps:

[0064] S11. Under a nitrogen atmosphere, 8.34 g of catechol (75 mmol) and 4.78 g of lithium tetrafluoroborate (51 mmol) were dissolved in 40 mL of dimethyl carbonate solution, and stirred to fully dissolve. 9.8 mL of trimethylsilyl chloride was slowly added dropwise to the reactor. After the addition was completed, the mixture was reacted at 60° C. for 6 h to obtain a mixed solution containing di(catechol)-complexed lithium borate.

[0065] S12. The mixed solution obtained by the reaction is evaporated at high temperature using a rotary evaporator to remove the solvent to obtain a solid product; the solid product is dissolved in dimethyl carbonate at high temperature to be dissolved into a clear liquid, and then the temperature is reduced for recrystallization, and filtered after 3 hours; the filter cake is vacuum dried at 90° C. for 12 hours to obtain 5.1 g of lithium di(catecholyl)borate with a purity of 99.5%, and the yield is 87.6%.

[0066] Example 2

[0067] In this example, lithium bis(catecholyl)borate is prepared by the following steps:

[0068] S11. Under a nitrogen atmosphere, 5.56 g of catechol (50 mmol) and 2.49 g of lithium tetrafluoroborate (26 mmol) were dissolved in 40 mL of dimethyl carbonate solution, and stirred to fully dissolve. 5.1 mL of dimethyldichlorosilane was slowly added dropwise to the reactor. After the addition was completed, the mixture was reacted at 60° C. for 6 h to obtain a mixed solution containing di(catechol)-containing lithium borate;

[0069] S12. The mixed solution obtained by the reaction is evaporated at high temperature using a rotary evaporator to remove the solvent to obtain a solid product; the solid product is dissolved in dimethyl carbonate at high temperature to be dissolved into a clear liquid, and then the temperature is reduced for recrystallization, and filtered after 3 hours; the filter cake is vacuum dried at 90° C. for 12 hours to obtain 5.9 g of lithium di(catecholyl)borate with a purity of 90.4%, and the yield is 97.4%.

[0070] Example 3

[0071] In this example, lithium bis(catecholyl)borate is prepared by the following steps:

[0072] S11. Under a nitrogen atmosphere, 5.56 g of catechol (50 mmol) and 2.49 g of lithium tetrafluoroborate (26 mmol) were dissolved in 40 mL of dimethyl carbonate solution, and stirred to fully dissolve. 13.03 mL of trimethylsilyl chloride was slowly added dropwise to the reactor. After the addition was completed, the mixture was reacted at 60° C. for 6 h to obtain a mixed solution containing di(catechol)-containing lithium borate.

[0073] S12. The mixed solution obtained by the reaction is evaporated at high temperature using a rotary evaporator to remove the solvent to obtain a solid product; the solid product is dissolved in dimethyl carbonate at high temperature to be dissolved into a clear liquid, and then the temperature is reduced for recrystallization, and filtered after 3 hours; the filter cake is vacuum dried at 90° C. for 12 hours to obtain 5.8 g of lithium di(catecholyl)borate with a purity of 98.5%, and the yield is 95.7%.

[0074] Comparative Example 1

[0075] This comparative example is prepared by the following steps:

[0076] 1) nitrogen was introduced into a dry three-necked flask equipped with a condensing device to ensure an oxygen-free environment; 1.9 g of lithium hydroxide monohydrate, 2.8 g of boric acid and 10 g of catechol were added into the reactor, and 60 mL of deionized water saturated with nitrogen was added, stirred to fully dissolve, and the reactor was slowly heated to 105° C. for 12 h to obtain a brown mixed solution;

[0077] 2) using a rotary evaporator to evaporate the mixed solution obtained by the reaction at high temperature to remove the solvent, thereby obtaining a solid product; after dissolving the solid product in acetonitrile at high temperature, the temperature is lowered and recrystallized to obtain lithium di(catecholate)borate.

[0078] Application Example 1

[0079] This application example prepares an electrolyte solution, using the lithium di(catecholyl) borate prepared in Example 1 as an electrolyte additive, and the steps are as follows:

[0080] 1) Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1 to obtain a mixed solvent; lithium hexafluorophosphate is dissolved in the mixed solvent to control the final concentration to be 1.0 mol / L, and stirred evenly to obtain a basic electrolyte;

[0081] 2) The lithium di(catechol)borate prepared in Example 1 was added to the basic electrolyte in an amount of 0.25% of the mass of the basic electrolyte to obtain a functional electrolyte containing the lithium di(catechol)borate additive.

[0082] Application Example 2

[0083] This application example prepares an electrolyte, using the lithium di(catecholated) borate prepared in Example 2 as an electrolyte additive, and the steps are as follows:

[0084] 1) Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1 to obtain a mixed solvent; lithium hexafluorophosphate is dissolved in the mixed solvent to control the final concentration to be 1.0 mol / L, and stirred evenly to obtain a basic electrolyte;

[0085] 2) The lithium di(catechol)borate prepared in Example 2 was added to the basic electrolyte in an amount of 0.5% of the mass of the basic electrolyte to obtain a functional electrolyte containing the lithium di(catechol)borate additive.

[0086] Application Example 3

[0087] This application example prepares an electrolyte, using the lithium di(catecholated) borate prepared in Example 3 as an electrolyte additive, and the steps are as follows:

[0088] 1) Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1 to obtain a mixed solvent; lithium hexafluorophosphate is dissolved in the mixed solvent to control the final concentration to be 1.0 mol / L, and stirred evenly to obtain a basic electrolyte;

[0089] 2) The lithium di(catechol)borate prepared in Example 3 was added to the basic electrolyte in an amount of 1% by mass of the basic electrolyte to obtain a functional electrolyte containing the lithium di(catechol)borate additive.

[0090] Application Comparative Example 1

[0091] This application comparative example prepares a common electrolyte, and the steps are as follows:

[0092] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1 to obtain a mixed solvent; lithium hexafluorophosphate is dissolved in the mixed solvent to control the final concentration to be 1.0 mol / L, and stirred evenly to obtain a common electrolyte.

[0093] Application Comparative Example 2

[0094] This application comparative example prepares an electrolyte, using the lithium di(catecholyl) borate prepared in comparative example 1 as an electrolyte additive, and the steps are as follows:

[0095] 1) Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 1:1 to obtain a mixed solvent; lithium hexafluorophosphate is dissolved in the mixed solvent to control the final concentration to be 1.0 mol / L, and stirred evenly to obtain a basic electrolyte;

[0096] 2) The lithium di(catechol)borate prepared in Comparative Example 1 was added to the basic electrolyte in an amount of 1% by mass of the basic electrolyte to obtain a functional electrolyte containing the lithium di(catechol)borate additive.

[0097] Characterization and performance testing

[0098] 1. The lithium bis(catecholyl) borate prepared in Example 1 was subjected to13 C NMR and 11 B NMR spectrum determination:

[0099] Figure 1 The NMR boron spectrum of the lithium bis(catecholyl)borate prepared in Example 1 is 11 B NMR, Figure 2 The carbon NMR spectrum of the lithium di(catecholyl)borate prepared in Example 1 is 13 C NMR, by Figure 1 and Figure 2 It can be seen that the lithium bis(catecholyl)borate prepared in Example 1 has the target structure.

[0100] 2. The lithium di(catecholyl) borate prepared in Example 3 and Comparative Example 1 was tested by Fourier transform infrared spectroscopy:

[0101] Figure 3 is the Fourier transform infrared spectrum of the lithium di(catecholyl) borate prepared in Example 3 and Comparative Example 1, Figure 3 It can be seen that the product in Example 1 has a similar structure to the lithium di(catecholate)borate prepared by the prior art in Comparative Example 1, indicating that the method in Example 1 successfully synthesized lithium di(catecholate)borate.

[0102] 3. Thermogravimetric analysis of the lithium bis(catecholyl)borate prepared in Example 3 and Comparative Example 1 was performed:

[0103] Figure 4 Thermogravimetric analysis of lithium bis(catecholyl)borate prepared in Example 3 and Comparative Example 1 is shown in FIG. Figure 4 It can be seen that in Comparative Example 1, the aqueous phase method is used to prepare lithium di(catecholyl)borate, which contains more crystal water, and the product has a large loss rate in the range of 100-400°C. However, the preparation method in Example 1 does not involve an aqueous phase, and the thermogravimetric loss of the product at 100-400°C is small, indicating that its crystal water content is relatively small.

[0104] 4. The lithium cobalt oxide / lithium half-cell was assembled with the electrolyte of Application Example 3 and Application Comparative Example 2, and the graphite half-cell was assembled with the electrolyte of Application Example 3 and Application Comparative Example 1. The battery shell was a 2025 model battery shell, the graphite electrode diameter was 12 mm, the lithium sheet diameter was kept consistent with the steel gasket (15.6 mm), the electrolyte dosage was 70 μL, and the diaphragm was a Celgard 2500 polypropylene film with a diameter of 16 mm:

[0105] 1) Use the Blue Electric Tester to perform a single constant current charge and discharge test on the lithium cobalt oxide / lithium half-cell, the test voltage range is 3-4.5V, and the rate used is 0.1C;

[0106] 2) The graphite / lithium half-cell was charged and discharged at different rates using a blue electric tester. The test voltage range was 0.005-2.5 V. After 10 cycles at 0.1C, 0.2C, 0.5C, 1C and 2C, the test was repeated 10 times at 1C.

[0107] Figure 5 The first charge and discharge curves of the lithium cobalt oxide / lithium half-cell corresponding to the electrolyte in Application Example 3 and Comparative Example 2 are as follows: Figure 5 It can be seen that in Application Example 2, lithium di(catechol)borate prepared by the aqueous phase method is used as an electrolyte additive. Since lithium di(catechol)borate contains crystalline water, it decomposes under high voltage, resulting in a relatively large polarization of the electrolyte under the first charge. In contrast, in Application Example 3, lithium di(catechol)borate prepared by the method provided by the present invention is used as an electrolyte additive. Since the crystalline water content in the product is greatly reduced, the polarization of the electrolyte under the first charge is relatively small, and it can be better used in batteries.

[0108] Figure 6 The rate performance test results of the electrolyte corresponding to the graphite / lithium half-cell in Application Example 3 and Comparative Example 1 are as follows: Figure 6 It can be seen that the electrolyte in Application Example 3, using the di(catechol)borate lithium prepared by the method provided by the present invention as an electrolyte additive, effectively improves the capacity attenuation problem of the graphite half-cell after the conversion rate, and improves the cycle stability of the graphite electrode. In the initial cycle, the graphite half-cell assembled with the electrolyte in Application Example 3 has a high charging capacity, indicating that the di(catechol)borate lithium prepared by the present invention improves the wettability between the electrolyte and the graphite electrode and improves the utilization rate of the graphite electrode. In the cycle at high rate, the graphite half-cell assembled with the electrolyte in Application Example 3 maintains a stable capacity, indicating that the di(catechol)borate lithium prepared by the method provided by the present invention as an electrolyte additive can effectively improve the rate performance of the battery.

[0109] The preparation method of lithium di(catechol)borate provided by the invention can reduce the content of crystal water in lithium di(catechol)borate compared with the traditional aqueous phase method; the prepared lithium di(catechol)borate can be added into a common electrolyte as an electrolyte additive; when the functional electrolyte containing the lithium di(catechol)borate additive is applied to the assembly of lithium ion batteries, the polarization ratio of the first charge can be effectively reduced, and the rate performance of the graphite half-cell can be effectively improved.

Claims

1. A method for preparing lithium bis(catecholyl)borate, characterized in that: The following steps are involved: S1. Under a protective atmosphere, dissolve catechol and lithium tetrafluoroborate in a non-aqueous solvent, dropwise add a siloxane additive, and heat to react to obtain a mixed solution; S2. The mixed solution is purified after the solvent is removed to obtain the lithium di(catecholate)borate.

2. The preparation method according to claim 1, characterized in that: The molar ratio of catechol, lithium tetrafluoroborate and siloxane additive is (1-3.5):1:(2-5).

3. The preparation method according to claim 1, characterized in that: The solid-to-liquid ratio of the catechol to the non-aqueous solvent is 1g: (4-10)mL.

4. The preparation method according to claim 1, characterized in that: The non-aqueous solvent is selected from at least one of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, acetonitrile, ether, tetrahydrofuran, dichloromethane and n-hexane.

5. The preparation method according to claim 1, characterized in that: The dropping speed of the silicone additive is 0.1-0.2 mL / min; Preferably, the siloxane auxiliary agent is selected from at least one of trimethylchlorosilane, dimethyldichlorosilane and hexamethyldisilazane.

6. The preparation method according to claim 1, characterized in that: The temperature of the heating reaction is 25-80° C.; and / or the time of the heating reaction is 3-9 hours.

7. An electrolyte, characterized in that: Including electrolyte additives and basic electrolyte; The electrolyte additive is lithium di(catecholyl)borate obtained by the preparation method according to any one of claims 1 to 6; the basic electrolyte comprises cyclic carbonate, linear carbonate and lithium salt.

8. The electrolyte according to claim 7, characterized in that The content of the electrolyte additive is 0.25%-1% of the mass of the basic electrolyte.

9. The electrolyte according to claim 7, characterized in that In the basic electrolyte, the mass ratio of the cyclic carbonate to the linear carbonate is 1:(0.3-3); and / or the content of the lithium salt is 0.8-1.5 mol / L.

10. A lithium ion battery, characterized in that: The electrolyte comprising any one of claims 7 to 9.

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