Preparation method of pentaerythritol bicyclic sulfate and application of pentaerythritol bicyclic sulfate in electrolyte and lithium ion battery

Abstract

The invention discloses a preparation method of pentaerythritol bicyclic sulfate and application of the pentaerythritol bicyclic sulfate in an electrolyte and a lithium ion battery, and relates to the technical field of lithium ion batteries. The method comprises the following steps: S1, carrying out a replacement reaction on alkali metal and pentaerythritol in an organic solvent at-10-10 DEG C for 5-20 hours to generate an intermediate product; and S2, carrying out nucleophilic substitution-cyclization reaction on the intermediate product and sulfuryl chloride in an organic solvent at 30-80 DEG C for 2-15 hours to generate pentaerythritol bicyclic sulfate. Compared with the prior art, the method has the advantages of simple synthesis process, high yield, no reaction involving conditions such as high temperature and high pressure, low energy consumption, less generated hazardous waste and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a preparation method of pentaerythritol bicyclic sulfate and its applications in electrolytes and lithium-ion batteries. Background Art

[0002] Disclosing the information of this background art section is only intended to enhance the overall understanding of the present invention and is not necessarily to be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art.

[0003] The electrolyte is an essential and important component in lithium-ion batteries, which has an important impact on various performances such as its capacity, cycle life, rate performance, and safety. Additives in the electrolyte can significantly improve the various performances of the battery. When pentaerythritol bicyclic sulfate (CAS No.: 201419-80-9) is used as an electrolyte additive, it can be more easily reduced and decomposed to form free radicals during the charging of the lithium battery. The free radicals can combine with lithium ions to form a suitable solid electrolyte interface film on the anode, improving the reversibility of lithium ion insertion / extraction, thereby increasing the discharge capacity and the cycle life of the battery. At the same time, pentaerythritol sulfate has a polycyclic-linked sulfate compound with a relatively large molecular weight and better thermal stability than traditional sulfate compounds.

[0004] There are various synthesis methods of pentaerythritol bicyclic sulfate in the prior art. For example, the Chinese patent with the application number "2019106073047" discloses a synthesis preparation method of pentaerythritol bicyclic sulfate, but there are problems such as low reaction yield and long reaction time; and it involves toxic reaction raw materials, with relatively high reaction temperature and production process pressure, having high requirements for safety and production; the Chinese patent with the application number "2022113217389" discloses a preparation method of pentaerythritol bicyclic sulfate using ether and sulfonyl fluoride gas as raw materials to obtain the product through a metathesis exchange method. This method uses relatively high-cost silyl ether and sulfonyl fluoride raw materials, and has relatively high danger and toxicity; the Chinese patent with the application number "2023110421913" discloses a preparation method of pentaerythritol bicyclic sulfate with the formation of an intermediate transition state. Due to steric hindrance effects, there are deficiencies such as many by-products and difficult purification. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a preparation method of pentaerythritol bicyclic sulfate and its applications in electrolytes and lithium-ion batteries, to solve the problems of low yield, difficult purification, and relatively high cost in the existing process, and to improve the high-temperature storage and cycle performance of lithium batteries.

[0006] To achieve the above purpose, the present invention is realized through the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing pentaerythritol bicyclic sulfate, comprising the following steps:

[0008] S1. In an organic solvent, an alkali metal and pentaerythritol undergo a displacement reaction, reacting at -10°C to 10°C for 5 to 20 hours to form an intermediate product;

[0009] S2. In an organic solvent, the intermediate product and thionyl chloride undergo a nucleophilic substitution-cyclization reaction, reacting at 30 to 80°C for 2 to 15 hours to form pentaerythritol bicyclic sulfate.

[0010] The reaction occurring in step S1 is as shown below:

[0011]

[0012] Among them, M is an alkali metal.

[0013] The reaction occurring in step S2 is as shown below:

[0014]

[0015] In the second aspect, an application of pentaerythritol bicyclic sulfate prepared by the above method in preparing an electrolyte is provided, and the electrolyte includes pentaerythritol bicyclic sulfate accounting for 0.05 to 5% of the total mass of the electrolyte.

[0016] In the third aspect, an application of pentaerythritol bicyclic sulfate prepared by the above method in preparing a lithium-ion battery is provided, and the electrolyte in the lithium-ion battery includes pentaerythritol bicyclic sulfate accounting for 0.05 to 5% of the total mass of the electrolyte.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. The present invention provides a novel synthesis process for pentaerythritol bicyclic sulfate, which has the advantages of simple synthesis process, high yield, no need for high temperature and high pressure conditions in the reaction, low energy consumption, and less hazardous waste generated compared with the prior art.

[0019] 2. The pentaerythritol bicyclic sulfate compound synthesized by the present invention has a structure in which two rings are connected in a spiro form, with strong thermal stability. When applied to the electrolyte, it can avoid the discoloration problem of the electrolyte caused by high temperature. At the same time, during charging, the pentaerythritol bicyclic sulfate compound accepts electrons from the negative electrode surface and reduces and decomposes itself to form free radicals and / or ions containing sulfate groups, forming a stable SEI layer and improving the high-temperature cycle stability. Description of the Drawings

[0020] The specification drawings forming a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention.

[0021] The distances or dimensions between parts are exaggerated in the figure for showing the positions of the parts, and the schematic diagram is only for illustration purposes.

[0022] Figure 1 It is the test result of the pentaerythritol bicyclic sulfate prepared in Example 1.

[0023] Figure 2 It is the test result diagram of the capacity retention rate in the specific implementation manner. Specific implementation manner

[0024] It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0025] It should be noted that the terms used herein are only for describing the specific implementation manner and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] The chemical substances used in the following specific implementation manner include:

[0027] Pentaerythritol, with the chemical formula C5H 12 O4, CAS No. 115-77-5.

[0028] Thionyl chloride, with the chemical formula SO2Cl2, CAS No. 7791-25-5.

[0029] Ethyl acetate, with the chemical formula C4H8O2, CAS No. 141-78-6.

[0030] Tetrahydrofuran, with the chemical formula C4H8O, CAS No. 109-99-9.

[0031] Dimethylformamide, with the chemical formula C3H7NO, CAS No. 68-12-2.

[0032] Acetonitrile, with the chemical formula C2H3N, CAS No. 75-05-8.

[0033] Formamide, with the chemical formula CH3NO, CAS No. 75-12-7.

[0034] The present invention will be further described below in conjunction with the drawings and embodiments.

[0035] A preparation method of pentaerythritol bicyclic sulfate, comprising the following steps:

[0036] S1. In an organic solvent, a displacement reaction occurs between an alkali metal and pentaerythritol, and an intermediate product is formed by reacting at -10°C to 10°C for 5 to 20 hours;

[0037] S2. In an organic solvent, a nucleophilic substitution-cyclization reaction occurs between the intermediate product and thionyl chloride, and pentaerythritol bicyclic sulfate is formed by reacting at 30°C to 80°C for 2 to 15 hours.

[0038] The reaction occurring in step S1 is as follows:

[0039]

[0040] Among them, M is an alkali metal.

[0041] The reaction occurring in step S2 is as follows:

[0042]

[0043] Optionally, in S1, the alkali metal includes one or more of sodium metal and lithium metal; the intermediate product includes one or more of sodium pentaerythritol and lithium pentaerythritol.

[0044] Optionally, in S1, the organic solvent includes one or more of tetrahydrofuran, dimethylformamide, acetonitrile, formamide, ethyl acetate, butyl acetate, and dimethyl carbonate; preferably tetrahydrofuran (THF) or dimethylformamide (DMF); the selected solvent needs to have a certain solubility for pentaerythritol and sodium pentaerythritol, reduce the post-treatment process, and the selected solvent cannot be water, alcohols, and solvents containing active hydrogen, and the water content of the organic solvent ≤ 10 ppm.

[0045] Optionally, in S1, during the reaction process, an inert gas is introduced into the reaction vessel at a set flow rate; optionally, the flow rate of the inert gas is 1 to 2 mL / min.

[0046] Optionally, in S1, the reaction temperature is -5°C to 4°C.

[0047] Optionally, in S1, the molar ratio of pentaerythritol to the alkali metal is 1:(4 to 5).

[0048] Optionally, in S1, pentaerythritol is added in the form of a dropping solution, and the alkali metal is added in the form of a powder, and the particle size of the powder is between 80 and 120 μm, so as to increase the later reaction rate.

[0049] Optionally, in S2, the intermediate product is dispersed in an organic solvent, and thionyl chloride solution is added thereto at 0-10°C, and then at 50-65°C; the reaction time is 5-10 h; among them, the possible side reaction is incomplete substitution to form a substitution product:

[0050]

[0051] To inhibit the occurrence of side reactions, the thionyl chloride solution needs to be added dropwise to the reaction solution generated in S1.

[0052] Optionally, in S2, the thionyl chloride solution is obtained by mixing thionyl chloride and an organic solvent in a mass ratio of 1:(1-3); the organic solvent includes one or more of tetrahydrofuran, dimethylformamide, acetonitrile, formamide, ethyl acetate, butyl acetate, and dimethyl carbonate. The organic solvent needs to be water-free and does not react with thionyl chloride, and is of the same type as the organic solvent selected in S1.

[0053] Optionally, in S2, the molar ratio of the intermediate product to thionyl chloride is 1:(2-2.1).

[0054] Optionally, in S2, the addition method of the thionyl chloride solution is dropwise addition, and the dropping rate is 1.2-1.8 mL / min.

[0055] Application of pentaerythritol bicyclic sulfate prepared by the above method in preparing an electrolyte, wherein the electrolyte includes 0.05-5% of pentaerythritol bicyclic sulfate by total mass of the electrolyte.

[0056] Optionally, the electrolyte further includes a lithium salt, an organic solvent, and ethylene carbonate; the total concentration of the lithium salt in the electrolyte is 0.6-1.4 mol / L; it includes one or more of lithium hexafluorophosphate (LiPF6) and lithium bis(fluorosulfonyl)imide (LiFSI);

[0057] The ethylene carbonate accounts for 0.5-8 wt% of the total mass of the electrolyte;

[0058] The organic solvent is a chain carbonate or a cyclic carbonate, preferably a mixture of any one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC).

[0059] Application of pentaerythritol bicyclic sulfate prepared by the above method in preparing a lithium ion battery, wherein the electrolyte in the lithium ion battery includes 0.05-5% of pentaerythritol bicyclic sulfate by total mass of the electrolyte.

[0060] Example 1

[0061] Preparation method of pentaerythritol bicyclic sulfate, including the steps:

[0062] S1. Add 459.6 g of anhydrous tetrahydrofuran into a four-necked flask, and add 91.92 g (4 mol) of metallic sodium. Introduce nitrogen at a rate of 2 mL / min, start stirring, and control the temperature at 0 ± 0.5 °C. Mix 136.15 g (1 mol) of pentaerythritol with 272.3 g of anhydrous tetrahydrofuran to form a dispersion, and add the dispersion dropwise into the four-necked flask at a temperature of 0 ± 0.5 °C. Continuously stir and react to make the metallic sodium react with pentaerythritol to generate sodium pentaerythritol and hydrogen. The hydrogen is mixed with the introduced nitrogen and discharged as tail gas to prevent hydrogen accumulation, and the sodium pentaerythritol is retained in the anhydrous tetrahydrofuran. React until no hydrogen is detected in the tail gas. The reaction time in this example is 8 h. Filter the liquid in the flask to obtain an anhydrous tetrahydrofuran solution of sodium pentaerythritol.

[0063] S2. Place the tetrahydrofuran solution of sodium pentaerythritol in a four-necked flask, start stirring and control the temperature at 0 ± 0.5 °C. Mix 269.94 g (2 mol) of thionyl chloride with 269.94 g of tetrahydrofuran to form a solution and add it to a constant pressure dropping funnel, and then add it dropwise into the four-necked flask at a rate of 1.2 mL / min. After the dropping is completed, raise the temperature to 50 °C and react for 8 h to obtain a tetrahydrofuran solution of pentaerythritol bicyclic sulfate. Filter, wash and rectify the tetrahydrofuran solution of pentaerythritol bicyclic sulfate, including: perform suction filtration on the reaction solution of pentaerythritol bicyclic sulfate to obtain a filter cake and a filtrate; wash the filter cake with water and dry it to obtain white solid pentaerythritol bicyclic sulfate.

[0064] The test results of the obtained pentaerythritol bicyclic sulfate are as Figure 1 shown. The purity measured by the gas phase purity detection method is 99.5%, and the further measured yield is 88.6%.

[0065] In the detection, the chromatographic column is: the stationary phase is (5%)-diphenyl (95%) dimethyl polysilazane; the chromatographic column: 0 m * 0.32 mm * 0.5 μm; the vaporization chamber temperature is 260 °C; the FID detector temperature is 280 °C; the column oven temperature: the initial temperature is 100 °C, and it is heated to 150 °C at a rate of 2 °C / min and held for 2 min; it is heated to 260 °C at a heating rate of 10 °C / min and held for 5 min; the injection volume is 0.5 and the split ratio is 50:1

[0066] Example 2

[0067] A preparation method of pentaerythritol bicyclic sulfate, which is different from Example 1 in that:

[0068] The reaction temperature in S1 is 4 °C, and the other methods and raw material requirements are the same as those in Example 1.

[0069] Example 3

[0070] A preparation method of pentaerythritol bicyclic sulfate, the difference from Example 1 is that:

[0071] In S1, 275.76 of anhydrous tetrahydrofuran is first added into the four-necked flask, and the reaction temperature is -5°C. Other methods and raw material requirements are the same as those in Example 1.

[0072] Example 4

[0073] A preparation method of pentaerythritol bicyclic sulfate, the difference from Example 1 is that:

[0074] The organic solvent used in S1 is dimethylformamide, and the reaction temperature is -5°C.

[0075] The organic solvent used in S2 is dimethylformamide.

[0076] Example 5

[0077] A preparation method of pentaerythritol bicyclic sulfate, the difference from Example 1 is that:

[0078] In S1, 136.15 g (1 mol) of pentaerythritol and 544.6 g of anhydrous tetrahydrofuran are mixed into a dispersion liquid, and the reaction temperature is -5°C.

[0079] Example 6

[0080] A preparation method of pentaerythritol bicyclic sulfate, the difference from Example 1 is that:

[0081] The dropping rate of the dispersion liquid in S1 is 1.5 mL / min, and the reaction temperature is -5°C.

[0082] Example 7

[0083] A preparation method of pentaerythritol bicyclic sulfate, the difference from Example 1 is that:

[0084] The reaction temperature in S1 is -5°C.

[0085] In S2, 269.94 g (2 mol) of thionyl chloride and 539.88 g of tetrahydrofuran are mixed into a solution.

[0086] Example 8

[0087] A preparation method of pentaerythritol bicyclic sulfate, the difference from Example 1 is that:

[0088] The reaction temperature in S1 is -5°C.

[0089] The dropping rate of the solution in S2 is 1.5 mL / min.

[0090] Example 9

[0091] A preparation method of pentaerythritol bicyclic sulfate, different from Example 1 in that: the reaction temperature in S1 is -5°C.

[0092] The dropping temperature in S2 is -5°C.

[0093] Example 10

[0094] A preparation method of pentaerythritol bicyclic sulfate, different from Example 1 in that: the reaction temperature in S1 is -5°C.

[0095] The dropping temperature in S2 is 10°C.

[0096] Example 11

[0097] A preparation method of pentaerythritol bicyclic sulfate, different from Example 1 in that: the reaction temperature in S1 is -5°C.

[0098] The dropping temperature in S2 is -5°C, and the reaction temperature is 65°C.

[0099] Example 12

[0100] A preparation method of pentaerythritol bicyclic sulfate, different from Example 1 in that: the reaction temperature in S1 is -5°C.

[0101] The dropping temperature in S2 is -5°C, and the reaction time is 5 h.

[0102] The specific parameters, yields and product purities of each example are shown in Table 1.

[0103]

[0104]

[0105] Example 13

[0106] A lithium-ion battery, the electrolyte of which includes pentaerythritol bicyclic sulfate.

[0107] The preparation method of the lithium-ion battery in this example includes:

[0108] Preparation of the positive electrode plate: Mix the positive electrode material lithium iron phosphate, conductive carbon black Super P and binder polyvinylidene fluoride (PVDF) evenly according to the mass ratio of 96.8:2:1.2, then disperse them in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode paste, and then coat the paste evenly on both sides of the aluminum foil, and obtain the positive electrode plate after drying and rolling.

[0109] Preparation of the negative electrode sheet: Graphite, conductive carbon black Super P, binder styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed evenly according to the mass ratio of 95.5:2:1.8:0.7. Then they were dispersed in deionized water to obtain a negative electrode slurry, and the slurry was evenly coated on both sides of the aluminum foil, followed by drying and rolling to obtain the negative electrode sheet.

[0110] Preparation of the electrolyte: In a glove box filled with argon (with moisture < 10 ppm and oxygen content < 10 ppm), ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed evenly at a mass ratio of 3:7. Subsequently, lithium hexafluorophosphate (LiPF6) with a mass fraction of 11.5% and lithium bis(fluorosulfonyl)imide (LiFSI) with a mass fraction of 2.5% were slowly added to the mixed solvent, and stirred until completely dissolved. Then 1 wt% vinylene carbonate (VC) and 0.8 wt% of the pentaerythritol bicyclic sulfate prepared in Example 1 were added to obtain the electrolyte of this example.

[0111] Battery preparation: The positive electrode sheet, separator, and negative electrode sheet were stacked in sequence, ensuring that the separator separated the positive electrode sheet and the negative electrode sheet, and the negative electrode sheet completely wrapped the positive electrode sheet. Then the stacked battery core was placed in an aluminum-plastic film packaging bag, and the prepared electrolyte was injected into the battery core. After formation, through processes such as sealing, aging, secondary sealing, and grading, a lithium iron phosphate battery with a capacity of 1000 mAh was manufactured.

[0112] The detection contents of the above electrolyte and lithium-ion battery include:

[0113] High-temperature acidity and chromaticity test of the electrolyte: The prepared electrolyte was filled into an aluminum-plastic bottle and placed in an oven at 60 °C for 48 h, and then the changes in the chromaticity and acidity of the electrolyte were measured.

[0114] High-temperature cycle test of the battery: Under high-temperature (55 °C) conditions, a lithium-ion battery was charged and discharged at 1C / 1C once (the battery discharge capacity was C0), with an upper limit voltage of 3.65 V, and then charged and discharged at 1C / 1C at room temperature for 800 cycles (the battery discharge capacity was C1);

[0115] Capacity retention rate = (C1 / C0) * 100%.

[0116] High-temperature storage test of the battery: Measure the constant current and constant voltage full charge capacity C1 at room temperature at 0.33C, then let it stand at 60 °C for 7 days. Take it out and wait for the battery to cool to room temperature (25 °C), and then the 1C discharge capacity at room temperature is recorded as C2. Continue to cycle three times and calculate the average discharge capacity and record it as C3. Then the capacity retention rate is: C2 / C1, and the capacity recovery rate is: C3 / C1.

[0117] Example 14

[0118] A lithium-ion battery, whose electrolyte includes pentaerythritol bicyclic sulfate. The difference from Example 13 is that: during the preparation of the electrolyte, 0.8 wt% of the pentaerythritol bicyclic sulfate prepared in Example 1 is replaced with 1.0 wt% of the pentaerythritol bicyclic sulfate prepared in Example 4.

[0119] Example 15

[0120] A lithium-ion battery, whose electrolyte includes pentaerythritol bicyclic sulfate. The difference from Example 13 is that: during the preparation of the electrolyte, 0.8 wt% of the pentaerythritol bicyclic sulfate prepared in Example 1 is replaced with 1.5 wt% of the pentaerythritol bicyclic sulfate prepared in Example 8.

[0121] Example 16

[0122] A lithium-ion battery, whose electrolyte includes pentaerythritol bicyclic sulfate. The difference from Example 13 is that: during the preparation of the electrolyte, 0.8 wt% of the pentaerythritol bicyclic sulfate prepared in Example 1 is replaced with 2.0 wt% of the pentaerythritol bicyclic sulfate prepared in Example 12.

[0123] Comparative Example 1

[0124] A lithium-ion battery, whose electrolyte does not include pentaerythritol bicyclic sulfate. The difference from Example 13 is that: during the preparation of the electrolyte, 0.8 wt% of the pentaerythritol bicyclic sulfate prepared in Example 1 is replaced with 1.5 wt% of vinylene sulfate.

[0125] The test results of Example 13, 14, 15, 16 and Comparative Example 1 are shown in Table 2, and the test result graph of the capacity retention rate is as Figure 2 shown.

[0126]

[0127]

[0128] The results show that after high-temperature storage, the physical property data analysis of the electrolyte: pentaerythritol bicyclic sulfate synthesized by different processes in the present invention is added in Example 13, 14, 15 and 16 respectively, and vinylene sulfate is added in Comparative Example 1 as a comparative example. It can be seen that the acidity and chromaticity of the electrolyte in Example 13, 14, 15 and 16 do not change much after high-temperature storage. This is because compared with vinylene sulfate, the pentaerythritol bicyclic sulfate compound has a structure in which two rings are connected in a spiro form and has strong thermal stability, which also explains the reason why the acidity and chromaticity in the examples change less than those in the control group.

[0129] High-temperature cycling performance analysis: The high-temperature cycling performance of Examples 13 and 15 is significantly superior to that of Comparative Example 1. This is because the sulfate group of the bicyclic sulfate compound can accept electrons from the negative electrode surface during charging and decompose itself reductively to form free radicals and / or ions containing sulfate groups, thereby affecting the characteristics of the SEI layer formed thereon, and further preventing or minimizing the formation of products obtained by further decomposing the solvent.

[0130] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing pentaerythritol bicyclic sulfate, characterized in that, It includes the following steps: S1. A displacement reaction occurs between an alkali metal and pentaerythritol in an organic solvent, and an intermediate product is formed by reacting at -10°C to 10°C for 5 to 20 hours; S2. A nucleophilic substitution-cyclization reaction occurs between the intermediate product and thionyl chloride in an organic solvent, and pentaerythritol bicyclic sulfate is formed by reacting at 30°C to 80°C for 2 to 15 hours.

2. The preparation method of the pentaerythritol bicyclic sulfate according to claim 1, characterized in that, In S1, the alkali metal includes one or more of sodium metal and lithium metal; the intermediate product includes one or more of sodium pentaerythritol and lithium pentaerythritol.

3. The preparation method of the pentaerythritol bicyclic sulfate according to claim 1, characterized in that, In S1, the organic solvent includes one or more of tetrahydrofuran, dimethylformamide, acetonitrile, formamide, ethyl acetate, butyl acetate, and dimethyl carbonate; preferably tetrahydrofuran or dimethylformamide.

4. The preparation method of the pentaerythritol bicyclic sulfate according to claim 1, characterized in that, In S1, during the reaction process, an inert gas is introduced into the reaction vessel at a set flow rate; or, the flow rate of the inert gas is 1 to 2 mL / min.

5. The preparation method of pentaerythritol bicyclic sulfate according to claim 1, characterized in that In S1, the reaction temperature is -5°C to 4°C.

6. The preparation method of pentaerythritol bicyclic sulfate according to claim 1, characterized in that, In S1, the molar ratio of pentaerythritol to the alkali metal is 1:(4 to 5); Or, in S1, pentaerythritol is added in the form of a dropping solution, and the alkali metal is added in the form of a powder with a particle size between 80 and 120 μm.

7. The preparation method of the pentaerythritol bicyclic sulfate according to claim 1, wherein, In S2, the intermediate product is dispersed in an organic solvent, thionyl chloride solution is added thereto at 0°C to 10°C, and then at 50°C to 65°C; the reaction time is 5 to 10 hours; Or, in S2, the thionyl chloride solution is obtained by mixing thionyl chloride and an organic solvent in a mass ratio of 1:(1 to 3); the organic solvent includes one or more of tetrahydrofuran, dimethylformamide, acetonitrile, formamide, ethyl acetate, butyl acetate, and dimethyl carbonate; Or, in S2, the molar ratio of the intermediate product to thionyl chloride is 1:(2 to 2.1); Or, in S2, the addition method of the thionyl chloride solution is dropping, and the dropping rate is 1.2 to 1.8 mL / min.

8. Use of the method for preparing pentaerythritol bicyclic sulfate according to any one of claims 1-7 in preparing an electrolyte, characterized in that, The electrolyte includes pentaerythritol bicyclic sulfate accounting for 0.05 to 5% of the total mass of the electrolyte.

9. Use of the method for preparing pentaerythritol bicyclic sulfate according to claim 8 in the preparation of an electrolyte, characterized in that, The electrolyte includes a lithium salt, an organic solvent, and ethylene carbonate; the total concentration of the lithium salt in the electrolyte is 0.6 to 1.4 mol / L; it includes one or more of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide; The ethylene carbonate accounts for 0.5 to 8 wt% of the total mass of the electrolyte; The organic solvent is a chain carbonate or a cyclic carbonate, preferably a mixture of any one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

10. Use of the method for preparing pentaerythritol bicyclic sulfate according to any one of claims 1-7 in the preparation of lithium ion batteries, characterized in that, The electrolyte in the lithium-ion battery includes pentaerythritol bicyclic sulfate accounting for 0.05 to 5% of the total mass of the electrolyte.

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