High-voltage stable electrolyte and lithium battery

Abstract

The invention discloses a high-voltage stable electrolyte and a lithium battery, and relates to the technical field of lithium batteries, the high-voltage stable electrolyte comprises an organic solvent, a lithium salt and an additive, the organic solvent comprises sulfate modified toluenesulfonyl and a carbonic ester compound; the additive comprises 3-bromofuran and a diluent; a preparation process of the sulfate modified toluenesulfonyl specifically comprises the following steps: preparing hydroxytoluene sulfone; the preparation method comprises the following steps: adding a sulfur trioxide trimethylamine complex and pyridine into a methanol solution of sodium hydroxide, stirring until the sulfur trioxide trimethylamine complex and pyridine are dissolved, then adding hydroxytoluene sulfone, uniformly dispersing, heating the mixture, refluxing a gaseous evaporant by using a reflux device, cooling to room temperature after the reaction is completed, filtering out a reaction product, adjusting the pH value to be neutral, washing with water, and drying to obtain the product. The sulfate modified toluenesulfonyl is obtained. The SEI film formed by mixing sulfate modified toluenesulfonyl as a main body with 3-bromofuran through reduction has better stability, and can maintain the battery performance in a long-time high-pressure environment.

Description

Technical Field

[0001] The present application relates to the technical field of lithium batteries, and in particular to a high-voltage stable electrolyte and a lithium battery. Background Art

[0002] With the rapid development of science and technology, lithium batteries are widely used in electric vehicles, electronic equipment and other fields as high-performance secondary batteries. However, when existing lithium batteries work in a high-voltage environment, the stability of their electrolytes is often affected, resulting in a decrease in battery performance and even safety hazards. Therefore, the development of a high-voltage stable electrolyte has become a research hotspot in the current field of lithium battery technology.

[0003] At present, the electrolytes on the market are mainly composed of organic solvents, lithium salts and additives. Although these electrolytes meet the use requirements of lithium batteries to a certain extent, their stability in high voltage environments still needs to be improved.

[0004] Invention patent publication number CN118522940A discloses a lithium metal battery and a high-voltage electrolyte thereof. The high-voltage electrolyte includes a non-aqueous organic solvent, a lithium salt and an electrolyte additive; the non-aqueous organic solvent includes any two or three of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate and dimethyl carbonate, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(oxalate)borate, lithium difluoro(oxalate)borate and lithium bis(fluorosulfonyl)imide, and the electrolyte additive is a halogenated phthalonitrile. The electrolyte can obtain a high mechanical stability and thermal stability CEI rich in LiF and -CN and a strong SEI layer rich in inorganic components such as LiF, Li2O and CN on the surface of the NCM811 cathode. The favorable CEI / SEI layer greatly reduces the decomposition of the electrolyte and the degradation of the electrode, and can effectively improve the high-voltage cycle stability of the lithium metal battery. However, after long-term high-voltage cycling, the SEI film containing inorganic components such as LiF, Li2O and CN and the stability of the SEI film will decrease to a certain extent, resulting in poor long-term stability of the battery prepared with this electrolyte under high voltage. Summary of the invention

[0005] In order to solve the problem of poor long-term stability of batteries prepared by electrolyte under high voltage, the purpose of this application is to provide a high-voltage stable electrolyte.

[0006] In the first aspect, the present application provides a high-voltage stable electrolyte using the following technical solution: A high-voltage stable electrolyte comprises: an organic solvent, a lithium salt and an additive, wherein the organic solvent comprises sulfate-modified toluenesulfonyl and a carbonate compound; the additive comprises 3-bromofuran and a diluent; The preparation process of the sulfate-modified tosyl is as follows: Preparation of hydroxytoluene sulfone; Add sulfur trioxide trimethylamine complex and pyridine to a methanol solution of sodium hydroxide, stir until dissolved, then add hydroxytoluene sulfone and disperse evenly, heat the mixture, and use a reflux device to reflux the gaseous evaporated material, react for 7-8 hours, and cool to room temperature after the reaction is completed. After filtering out the reaction product, adjust the pH to neutral, and wash with water and dry to obtain sulfate-modified toluenesulfonyl.

[0007] By adopting the above technical solution, when the battery is charged for the first time, the negative electrode material reacts with the electrolyte to form a SEI film on the surface of the negative electrode material. The SEI film can isolate the electrode from the electrolyte while allowing lithium ions to freely enter and exit, thereby maintaining the normal operation of the battery. Sulfate-modified toluenesulfonyl as part of the organic solvent and 3-bromofuran as part of the additive have better reducibility than carbonate compounds and diluents. After the negative electrode reacts with the electrode material, they are preferentially reduced and deposited on the negative electrode to form a SEI film, so that carbonate and diluent can remain in the electrolyte solvent, maintaining the ion conductivity of the solvent, and the SEI film formed by the reduction of sulfate-modified toluenesulfonyl as the main body and 3-bromofuran has better stability, will not be dissolved and corroded under long-term high-voltage environment, and maintains the embedding site of lithium ions. The sulfur trioxide trimethylamine complex can introduce sulfur trioxide in a liquid environment, and under the catalysis of pyridine, form a sulfate group with the hydroxyl group, thereby connecting the sulfonyl group and the sulfate group. Through the synergistic effect of the sulfate group and the sulfate group, the formed SEI film can maintain the stability of the lithium ion embedding site under high pressure, and under the joint action of 3-bromofuran, the structural stability of the SEI film can be maintained, which can resist the erosion of the electrolyte and maintain the capacity stability of the lithium battery for a long time.

[0008] Optionally, the volume ratio of the sulfate-modified toluenesulfonyl and the carbonate compound is 1:(1.5-3.5); the molecular weight ratio of 3-bromofuran and is 1:(1-2); the mass ratio of the organic solvent, lithium salt and additive is between 1:(1.2-2.8):(0.05-0.25).

[0009] By adopting the above technical solution and limiting the proportion of each component within a suitable range, the electrolyte can form a passivation film with excellent properties while ensuring the normal conduction of lithium ions in the electrolyte and the normal operation of the lithium-ion battery.

[0010] Optionally, the molar ratio of the hydroxytoluene sulfone to the trimethylamine sulfur trioxide complex is between 1:(1.1-1.3), and the mass ratio of the hydroxytoluene sulfone to the pyridine is between 1:(0.03-0.18).

[0011] By adopting the above technical solution, the molar number of hydroxytoluene sulfone is small, ensuring that the hydroxyl groups can be reacted with sulfur trioxide to form sulfate groups. By limiting the amount of pyridine, the reaction can proceed at a suitable rate, ensuring the stability of the product.

[0012] Optionally, the carbonate compound is selected from one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, ethylene propylene carbonate, fluoroethylene carbonate and vinylene carbonate; the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisoxalatoborate, lithium difluorooxalatoborate, trifluoromethylsulfonyl lithium, lithium bisfluorosulfonyl imide, lithium bisoxalatoborate, lithium bisfluorosulfonyl imide and lithium bis(trifluoromethylsulfonyl)imide; and the diluent is selected from one or more of fluorobenzene, fluoromethane, fluoroethane, fluoropropane, methyl chloride, ethyl chloride, chloropropane, methyl bromide, ethyl bromide and bromopropane.

[0013] By adopting the above technical solution, by using the above carbonate compounds, lithium salts and diluents, the electrolyte can stably perform the performance of transmitting lithium ions, and can maintain good fluidity and transmission properties under high and low temperature conditions, thereby ensuring the normal operation of the lithium-ion battery.

[0014] Optionally, the preparation method of the hydroxytoluene sulfone is as follows: Sodium p-toluenesulfinate is added to water to obtain a first solution, alkynes are added to the methanol mixture to obtain a second solution, the first solution and the second solution are mixed, and an iron salt catalyst is added, and the reaction is carried out at 35-90° C. for 12-18 hours to obtain an intermediate product; lithium aluminum hydride is added to the intermediate product, stirring is maintained, and the temperature is maintained at 25-35° C., and the reaction is carried out for 3-6 hours, and then hydroxytoluene sulfone is obtained after filtering, distillation, and washing with water.

[0015] By adopting the above technical scheme, sodium p-toluenesulfinate and alkyne are reacted to generate a sulfone compound, and the carbonyl group is reduced to a hydroxyl group through a selective hydrogenation reaction of lithium aluminum hydride, so that the sulfone group is respectively connected to toluene and a carbon chain with a hydroxyl group, and the sulfone group can react with a sulfur trioxide trimethylamine complex through the hydroxyl group, thereby connecting to a sulfate group.

[0016] Optionally, the molar ratio of the alkyne to the sodium p-toluenesulfinate is between (1.1-1.3):1, and the mass ratio of the iron salt catalyst to the alkyne is between (0.05-0.25):1.

[0017] By adopting the above technical solution, by adding excess alkyne in the reaction, the sodium p-toluenesulfinate can be completely reacted, and the remaining alkyne can be discharged from the system together with distillation and filtration in the subsequent treatment. The ratio of the iron salt catalyst to the alkyne is limited to a suitable range, so that the sodium p-toluenesulfinate and the alkyne can react stably and avoid the generation of by-products.

[0018] Optionally, the iron salt catalyst is selected from one of ferric chloride, ferric bromide and ferrous chloride, and the metal catalyst is selected from one of platinum, palladium and nickel.

[0019] By adopting the above technical scheme, the iron salt catalyst is used to catalyze the reaction of sodium p-toluenesulfinate and alkyne. Although the activity of the carbon-carbon triple bond is relatively high, the activity of the sulfinic acid group is relatively low. In an environment without a catalyst, the reaction rate of the two is relatively slow. By adding an iron salt catalyst including ferric chloride, ferric tribromide and ferrous chloride, the state of the sulfinic acid group is changed, the reaction activity is improved, and the synthesis reaction can be carried out quickly.

[0020] Optionally, the alkyne is selected from one or more of acetylene, propyne, butyne, n-pentyne and isopentyne.

[0021] By adopting the above technical solution, alkynes are used to connect carbon chains to sulfinic acid groups to form sulfonyl groups. By adopting different types of alkynes, the form of the carbon chain connected to the sulfonyl group can be changed, and the form of the carbon chain will affect the properties of hydroxytoluene sulfone. By using acetylene, propyne, butyne, n-pentyne and isopentyne as reaction raw materials, the carbon chain connected to the sulfonyl group will not be too long, so that the hydroxyl group can maintain a better distance from the sulfonyl group, and after the sulfate ester group is subsequently connected, the sulfonyl group can maintain a better distance from the sulfate ester group, play a synergistic role, and improve the properties of the electrolyte.

[0022] Optionally, the preparation method of the high-voltage stable electrolyte is as follows: Preparation of sulfate-modified tosyl; Mixing the sulfate-modified toluenesulfonyl and the carbonate compound at a temperature of 30-35° C. for 10-30 minutes to obtain an organic solvent; Add lithium salt, 3-bromofuran and a diluent into an organic solvent, mix for 20-40 minutes at a temperature of 25-45° C., and obtain an electrolyte.

[0023] By adopting the above technical solution, the sulfate-modified toluenesulfonyl can be mixed with carbonate compounds to form a uniform liquid as a solvent, which can effectively improve the dissolving capacity of the organic solvent. Lithium salt, 3-bromofuran as an additive, and a diluent are added to the organic solvent so that the components of the electrolyte can be mixed evenly to form a solution with a consistent phase, thereby improving the stability of the electrolyte.

[0024] In the second aspect, the present application provides a lithium battery adopting the following technical solution: A lithium battery using the above-mentioned high-voltage stable electrolyte.

[0025] By adopting the above technical solution, during the initial discharge, the chemically stable SEI film produced by the electrolyte and the negative electrode, and the CEI film that is difficult to fall off, are produced at the positive electrode. After multiple cycles of the battery, both the SEI film and the CEI film can maintain better properties to maintain the impedance stability of the electrode, thereby ensuring the long-term normal operation of the battery in a high-voltage environment.

[0026] In summary, the present application includes at least one of the following beneficial technical effects: 1. Sulfate-modified toluenesulfonyl as part of the organic solvent and 3-bromofuran as part of the additive have better reducibility than carbonate compounds and diluents. After the negative electrode reacts with the electrode material, they are preferentially reduced and deposited on the negative electrode to form an SEI film, so that carbonate and diluent can remain in the electrolyte solvent, maintaining the ion conductivity of the solvent. The SEI film formed by the reduction of sulfate-modified toluenesulfonyl as the main body and 3-bromofuran has better stability. In a long-term high-voltage environment, it will not be dissolved and corroded, maintaining the embedding site of lithium ions and maintaining the capacity of the lithium battery for a long time. 2. Sodium p-toluenesulfinate is reacted with alkynes to generate sulfone compounds, and the carbonyl group is reduced to a hydroxyl group by a selective hydrogenation reaction of lithium aluminum hydride, so that the sulfone group is connected to toluene and a carbon chain with a hydroxyl group, respectively, so that the sulfone group can react with a sulfur trioxide trimethylamine complex through the hydroxyl group, thereby connecting to a sulfate group; 3. Sulfate-modified toluenesulfonyl can form a uniform liquid as a solvent by mixing with carbonate compounds, which can effectively improve the solubility of organic solvents. Lithium salts, 3-bromofuran as an additive, and diluents are added to the organic solvent so that the components of the electrolyte can be mixed evenly to form a solution with a consistent phase state, thereby improving the stability of the electrolyte. DETAILED DESCRIPTION

[0027] The present application is further described in detail below in conjunction with embodiments and comparative examples.

[0028] In the following preparation examples, embodiments and comparative examples, the carbonate compound used is dimethyl carbonate, the diluent is a mixture of o-difluorobenzene, p-difluorobenzene and m-difluorobenzene, the lithium salt is a mixture of lithium hexafluorophosphate and lithium tetrafluoroborate, the alkyne is propyne, the iron salt catalyst is ferric chloride, and the metal catalyst is platinum.

[0029] Preparation Example 1 The preparation of hydroxytoluene sulfone comprises the following steps: S001. Dissolve 8.9 g of sodium p-toluenesulfinate in 100 ml of deionized water to obtain a first solution, dissolve 0.88 g of propyne in 20 ml of methanol to obtain a second solution, mix the first solution and the second solution and stir evenly, then add 0.05 g of ferric chloride, mix evenly, keep warm at 65°C for 12 h to complete the reaction, cool the reaction product to room temperature, adjust the pH to alkaline, filter out the precipitate, and obtain an intermediate product.

[0030] S002. Add lithium aluminum hydride to the intermediate product prepared in step S001, and keep stirring. React at a temperature of 30° C. for 4 hours. After washing with distilled water, hydroxytoluene sulfone is obtained.

[0031] Preparation Example 2 The preparation of hydroxytoluene sulfone comprises the following steps: S001. Dissolve 8.9 g of sodium p-toluenesulfinate in 100 ml of deionized water to obtain a first solution, dissolve 1.04 g of propyne in 20 ml of methanol to obtain a second solution, mix the first solution and the second solution and stir evenly, then add 0.26 g of ferric chloride, mix evenly, keep warm at 65°C for 12 h to complete the reaction, cool the reaction product to room temperature, adjust the pH to alkaline, filter out the precipitate, and obtain an intermediate product.

[0032] S002. Add lithium aluminum hydride to the intermediate product prepared in step S001, keep stirring, react at a temperature of 30° C. for 4 hours, and wash with distilled water to obtain hydroxytoluene sulfone.

[0033] Example 1 The preparation of high voltage stable electrolyte includes the following steps: S011, 0.4g of sodium hydroxide was dissolved in 100ml of methanol solution, and then 2.2g of sulfur trioxide trimethylamine complex and 0.21g of pyridine were added in sequence, stirred until dissolved, and then 6.9g of hydroxytoluene sulfone prepared in Preparation Example 1 was added and dispersed evenly, and the gaseous evaporated product was refluxed at 62°C using a reflux device, and the reaction was performed for 7.5h. After the reaction was completed, the product was cooled to room temperature, the reaction product was filtered out, the pH was adjusted to neutral, and after washing with water and drying, sulfate-modified toluenesulfonyl was obtained. S012, mixing 100 ml of the sulfate-modified toluenesulfonyl obtained in step S011 and 150 ml of dimethyl carbonate, and mixing at a temperature of 33° C. for 20 min to obtain an organic solvent; S013. Take 100 g of the organic solvent obtained in step S012, and add 20 g of lithium hexafluorophosphate, 20 g of lithium tetrafluoroborate, 2.8 g of 3-bromofuran and 2.2 g of difluorobenzene thereto, and mix at a temperature of 35° C. for 30 min to obtain an electrolyte.

[0034] Example 2 Compared with Example 1, the difference of Example 2 is: S011. Dissolve 0.4 g of sodium hydroxide in 100 ml of methanol solution, then add 2.6 g of sulfur trioxide trimethylamine complex and 0.70 g of pyridine in sequence, stir until dissolved, then add 6.9 g of hydroxytoluene sulfone prepared in Preparation Example 1, and disperse evenly, reflux the gaseous evaporated material at 62°C using a reflux device, react for 7.5 hours, cool to room temperature after the reaction is completed, filter out the reaction product, adjust the pH to neutral, and wash with water and dry to obtain sulfate-modified toluenesulfonyl.

[0035] S012, mixing 100 ml of the sulfate-modified toluenesulfonyl obtained in step S011 and 150 ml of dimethyl carbonate, and mixing at a temperature of 33° C. for 20 min to obtain an organic solvent; S013. Take 100 g of the organic solvent obtained in step S012, and add 20 g of lithium hexafluorophosphate, 20 g of lithium tetrafluoroborate, 2.8 g of 3-bromofuran and 2.2 g of difluorobenzene thereto, and mix at a temperature of 35° C. for 30 min to obtain an electrolyte.

[0036] Example 3 Compared with Example 1, the difference of Example 3 is: S011. Dissolve 0.4 g of sodium hydroxide in 100 ml of methanol solution, then add 3.1 g of sulfur trioxide trimethylamine complex and 1.24 g of pyridine in sequence, stir until dissolved, then add 6.9 g of hydroxytoluene sulfone prepared in Preparation Example 1, and disperse evenly, reflux the gaseous evaporate at 62°C using a reflux device, react for 7.5 hours, cool to room temperature after the reaction is completed, filter out the reaction product, adjust the pH to neutral, and wash with water and dry to obtain sulfate-modified toluenesulfonyl.

[0037] S012, mixing 100 ml of the sulfate-modified toluenesulfonyl obtained in step S011 and 150 ml of dimethyl carbonate, and mixing at a temperature of 33° C. for 20 min to obtain an organic solvent; S013. Take 100 g of the organic solvent obtained in step S012, and add 20 g of lithium hexafluorophosphate, 20 g of lithium tetrafluoroborate, 2.8 g of 3-bromofuran and 2.2 g of difluorobenzene thereto, and mix at a temperature of 35° C. for 30 min to obtain an electrolyte.

[0038] Example 4 Compared with Example 1, the difference of Example 4 is: S012, mixing 100 ml of the sulfate-modified toluenesulfonyl obtained in step S011 and 250 ml of dimethyl carbonate, and mixing at a temperature of 33° C. for 20 min to obtain an organic solvent; S013. Take 100 g of the organic solvent obtained in step S012, and add 25 g of lithium hexafluorophosphate, 25 g of lithium tetrafluoroborate, 4.3 g of 3-bromofuran and 10.7 g of difluorobenzene thereto, and mix at a temperature of 35° C. for 30 min to obtain an electrolyte.

[0039] Example 5 Compared with Example 1 and Example 5, the difference is: S012, mixing 100 ml of the sulfate-modified toluenesulfonyl obtained in step S011 and 350 ml of dimethyl carbonate, and mixing at a temperature of 33° C. for 20 min to obtain an organic solvent; S013. Take 100 g of the organic solvent obtained in step S012, and add 30 g of lithium hexafluorophosphate, 30 g of lithium tetrafluoroborate, 5.2 g of 3-bromofuran and 19.8 g of difluorobenzene thereto, and mix at a temperature of 35° C. for 30 min to obtain an electrolyte.

[0040] Example 6 Compared with Example 1, the difference of Example 6 is that the sulfate-modified toluenesulfonyl prepared in Preparation Example 2 is used instead of the sulfate-modified toluenesulfonyl prepared in Preparation Example 1.

[0041] Comparative Example 1 Compared with Example 1, the difference of Comparative Example 1 is that dimethyl sulfate is used instead of the sulfate-modified toluenesulfonyl prepared in Preparation Example 1.

[0042] Comparative Example 2 Compared with Example 1, the difference in Comparative Example 2 is that 3-bromofuran is not added, and an equal mass of difluorobenzene is used instead.

[0043] The performance tests were performed on the electrolytes prepared in the examples and comparative examples.

[0044] The test method for battery capacity and high-voltage cycle performance is as follows: inject the electrolyte into an unfilled high-voltage battery (the positive electrode is lithium iron phosphate and the negative electrode is graphite carbon). After packaging, shelving, formation, capacity division and other processes, a high-voltage battery is obtained. Referring to GB / T 18287-2000 General Specification for Lithium-ion Batteries for Cellular Phones, the high-voltage battery is charged at 1C rate constant current to 4.35V or 4.45V at 25°C, and then charged at 4.35V or 4.45V at constant voltage to a current of 20mA. After shelving for 10 minutes, it is discharged at 1C rate constant current to a cutoff of 2.75V, and then shelved for 10 minutes. Repeat this cycle until the required number of cycles is reached. Record the number of cycles and capacity to detect the high-voltage stability of the electrolyte.

[0045] The test results of the electrolytes prepared in the embodiments and preparation examples of Table 1 are as follows: The performance of the electrolyte prepared in the present application is explored in combination with Table 1, the embodiments and the comparative examples.

[0046] Comparing Examples 1, 2 and 3, the difference is that the raw material ratios and catalyst amounts for preparing sulfate-modified toluenesulfonyl are different. It can be seen that the electrolyte prepared under the conditions that the mass ratio of hydroxytoluenesulfone and sulfur trioxide trimethylamine complex is between 1:(0.31-0.45) and the mass ratio of hydroxytoluenesulfone and pyridine is between 1:(0.03-0.18) can still maintain a high cycle capacity after multiple cycles at high pressure, and the difference between the three is not large, indicating that the electrolytes prepared in Examples 1, 2 and 3 all have better high-voltage stability.

[0047] Comparing Examples 1, 4 and 5, the difference lies in the different compositions of the electrolytes. It can be seen that the volume ratio of sulfate-modified toluenesulfonyl and carbonate compounds is 1:(1.5-3.5), the molecular weight ratio of 3-bromofuran and diluent is 1:(1-2); the mass ratio of organic solvent, lithium salt and additive is between 1:(0.4-0.6):(0.05-0.25). The lithium battery prepared by the electrolyte has a small decrease in cycle capacity under high-voltage multiple cycles, and the difference between the three is not large, indicating that the electrolytes prepared in Examples 1, 4 and 5 have better high-voltage stability.

[0048] Comparing Examples 1 and 6, the difference is that the raw material ratios used in the preparation of sulfate-modified toluenesulfonyl are different. It can be seen that under the conditions that the molar ratio of alkyne to sodium p-toluenesulfinate is between (1.1-1.3):1, and the mass ratio of iron salt catalyst to alkyne is between (0.05-0.25):1, the prepared electrolyte can still maintain a high cycle capacity after multiple high-voltage cycles, and the difference between the three is not large, indicating that the electrolytes prepared in Examples 1 and 6 have better high-voltage stability.

[0049] Comparing Example 1 and Comparative Example 1, the difference is that the electrolyte solvent in Example 1 includes sulfate-modified toluenesulfonyl and dimethyl carbonate, while dimethyl sulfate is used instead of sulfate-modified toluenesulfonyl in Comparative Example 1. It can be seen that compared with Example 1, the lithium battery prepared by the electrolyte prepared in Comparative Example 1 has a greater decrease in cycle capacity after multiple cycles, indicating that sulfate-modified toluenesulfonyl can effectively improve the long-term high-voltage stability of the electrolyte.

[0050] Comparing Example 1 and Comparative Example 2, the difference is that the additive of the electrolyte in Example 1 includes 3-bromofuran, while an equal mass of difluorobenzene is used instead in Comparative Example 2. It can be seen that the lithium battery prepared by the electrolyte prepared in Comparative Example 2 has a greater decrease in cycle capacity after multiple cycles compared with Example 1, indicating that 3-bromofuran as an additive can effectively improve the long-term high-voltage stability of the electrolyte.

[0051] The embodiments of this specific implementation are all preferred embodiments of this application, and are not intended to limit the protection scope of this application. Therefore, any equivalent changes made based on the structure, shape, and principle of this application should be included in the protection scope of this application.

Claims

1. A high-voltage stable electrolyte, characterized in that: include: An organic solvent, a lithium salt and an additive, wherein the organic solvent comprises sulfate-modified toluenesulfonyl and a carbonate compound; and the additive comprises 3-bromofuran and a diluent; The preparation process of the sulfate-modified tosyl is as follows: Preparation of hydroxytoluene sulfone; Add sulfur trioxide trimethylamine complex and pyridine to a methanol solution of sodium hydroxide, stir until dissolved, then add hydroxytoluene sulfone and disperse evenly, heat the mixture, and use a reflux device to reflux the gaseous evaporated material, react for 7-8 hours, and cool to room temperature after the reaction is completed. After filtering out the reaction product, adjust the pH to neutral, and wash with water and dry to obtain sulfate-modified toluenesulfonyl.

2. The high-voltage stable electrolyte according to claim 1, characterized in that: The volume ratio of the sulfate-modified toluenesulfonyl and the carbonate compound is 1:(1.5-3.5); the molecular weight ratio of the 3-bromofuran and the diluent is 1:(1-2); and the mass ratio of the organic solvent, the lithium salt and the additive is between 1:(0.4-0.6):(0.05-0.25).

3. The high-voltage stable electrolyte according to claim 1, characterized in that: The mass ratio of the hydroxytoluene sulfone to the trimethylamine sulfur trioxide complex is between 1:(0.31-0.45), and the mass ratio of the hydroxytoluene sulfone to the pyridine is between 1:(0.03-0.18).

4. The high-voltage stable electrolyte according to claim 1, characterized in that: The carbonate compound is selected from one or more of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene carbonate, propylene carbonate, ethylene propylene carbonate, fluoroethylene carbonate and vinylene carbonate; the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisoxalatoborate, lithium difluorooxalatoborate, trifluoromethylsulfonyl lithium, lithium bisfluorosulfonyl imide, lithium bisoxalatoborate, lithium bisfluorosulfonyl imide and lithium bis(trifluoromethylsulfonyl)imide; the diluent is selected from one or more of fluorobenzene, fluoromethane, fluoroethane, fluoropropane, methyl chloride, ethyl chloride, chloropropane, methyl bromide, ethyl bromide and bromopropane.

5. The high-voltage stable electrolyte according to claim 1, characterized in that: The preparation method of the hydroxytoluene sulfone is as follows: Sodium p-toluenesulfinate is added to water to obtain a first solution, alkyne is added to the methanol mixture to obtain a second solution, the first solution and the second solution are mixed, and an iron salt catalyst is added, and the mixture is reacted at 35-90° C. for 12-18 hours to obtain an intermediate product; Add lithium aluminum hydride to the intermediate product, keep stirring, and maintain the temperature at 25-35° C. for 3-6 hours, and then distill and wash with water to obtain hydroxytoluene sulfone.

6. The high-voltage stable electrolyte according to claim 1, characterized in that: The molar ratio of the alkyne to the sodium p-toluenesulfinate is between (1.1-1.3):1, and the mass ratio of the iron salt catalyst to the alkyne is between (0.05-0.25):

1.

7. The high-voltage stable electrolyte according to claim 1, characterized in that: The iron salt catalyst is selected from one of ferric chloride, ferric bromide and ferrous chloride, and the metal catalyst is selected from one of platinum, palladium and nickel.

8. The high-voltage stable electrolyte according to claim 1, characterized in that: The alkyne is selected from one or more of acetylene, propyne, butyne, n-pentyne and isopentyne.

9. The high-voltage stable electrolyte according to claim 1, characterized in that: The preparation method of the high-voltage stable electrolyte is as follows: Mixing the sulfate-modified toluenesulfonyl and the carbonate compound at a temperature of 30-35° C. for 10-30 minutes to obtain an organic solvent; Add lithium salt, 3-bromofuran and a diluent into an organic solvent, mix for 20-40 minutes at a temperature of 25-45° C., and obtain an electrolyte.

10. A lithium battery, characterized in that: A high-voltage stable electrolyte as described in any one of claims 1 to 9 is used.

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