A lithium battery electrolyte solvent and its preparation method and application

Abstract

The present invention provides a lithium battery electrolyte solvent and a preparation method and application thereof, belonging to the technical field of lithium batteries, and the preparation method steps: S1, adding a raw material solvent and ethylene glycol diformate to a reactor, stirring, adding a catalyst, a halogenating agent, turning on ultraviolet light at the same time, blowing nitrogen into the reactor, absorbing the waste gas through an alkaline solution, adding an alkaline pH regulator to the reactor, blowing with nitrogen at the same time, discharging the tail gas, until the pH value reaches neutral, and obtaining a 1,6-dihalogenated ethylene glycol diformate solution; S2, filtering the 1,6-dihalogenated ethylene glycol diformate solution and transferring it to the reactor two, refluxing, adding a sodium methoxide solution, cooling to room temperature, adding an acidic pH regulator, until the pH value reaches neutral, and obtaining a 2,5-dioxy adipate dimethyl ester solution; S3, rectification and purification, that is. The present invention ensures that the obtained lithium battery electrolyte has excellent stability at a high voltage of 5V.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a lithium battery electrolyte solvent and a preparation method and application thereof. Background Art

[0002] With the rapid development of electric vehicles, electronics and other industries, the requirements for the energy density of lithium-ion batteries are getting higher and higher. The lithium-ion battery industry has also improved the energy density of batteries through various technological breakthroughs. Among them, increasing the maximum voltage of the battery is the most effective way to increase the energy density, because increasing the voltage also increases the battery capacity.

[0003] Due to the decomposition of carbonate solvents under high voltage, the maximum voltage of 4.5V has become the biggest technical difficulty of lithium-ion batteries. If tested under a high voltage environment of 5V, carbonate solvents are prone to oxidative decomposition, resulting in damage to the electrolyte structure and increased side reactions; at the same time, high voltage will accelerate the degradation of electrode materials, further reducing the cycle stability and capacity retention rate of the battery. Summary of the invention

[0004] In order to solve the problems existing in the background technology, the present invention provides a lithium battery electrolyte solvent and a preparation method and application thereof, so as to ensure that the prepared lithium battery electrolyte has excellent stability under a high voltage of 5V.

[0005] In order to achieve the above-mentioned object, in a first aspect, the present invention provides a method for preparing a lithium battery electrolyte solvent, comprising the following steps:

[0006] S1, halogenation reaction: add the raw material solvent and ethylene glycol diformate to the reactor 1, stir, add the catalyst, control the temperature at 5-10°C, add the halogenating agent, and turn on the ultraviolet light at a light intensity of 800-1200μW / cm 2 After stirring and reacting for 2-3 hours, nitrogen is blown into the reactor 1, and the waste gas is absorbed by the alkaline solution. Then, an alkaline pH regulator is added to the reactor 1, and nitrogen is blown at the same time to discharge the tail gas until the pH value reaches neutral, thereby obtaining a 1,6-dihalodiformic acid ethylene glycol ester solution;

[0007] S2, nucleophilic substitution reaction; filter the 1,6-dihalodiformic acid ethylene glycol ester solution obtained in S1 and transfer it to the second reaction kettle, heat it to 61-77°C, add sodium methoxide solution under reflux, reflux for 1.5-2h, cool it to room temperature, add an acidic pH regulator until the pH value reaches neutral, and obtain 2,5-dioxoadipate dimethyl ester solution;

[0008] S3, distillation and purification; filtering, roughly distilling, washing, and distilling the 2,5-dioxadipic acid dimethyl ester solution obtained in S2 to obtain the lithium battery electrolyte solvent.

[0009] Furthermore, in S1, the raw material solvent includes carbon tetrachloride or chloroform.

[0010] Furthermore, in S1, the catalyst includes any one of aluminum trichloride, boron trifluoride, palladium, sulfuric acid, and phosphoric acid.

[0011] Furthermore, in S1, the halogenating agent includes liquid chlorine or liquid bromine.

[0012] Furthermore, in S1, the molar ratio of the raw material solvent, ethylene glycol diformate and the halogenating agent is (2-3):1:(2.05-2.10).

[0013] Furthermore, in S1, the alkaline pH regulator includes sodium bicarbonate or sodium carbonate; and in S2, the acidic pH regulator is 5-10% dilute hydrochloric acid.

[0014] Furthermore, in S2, the sodium methoxide solution is prepared by mixing sodium methoxide and a raw material solvent, and the molar ratio of the sodium methoxide to ethylene glycol diformate is (2.05-2.1):1.

[0015] In a second aspect, the present invention provides a lithium battery electrolyte solvent prepared by the above-mentioned preparation method.

[0016] In a third aspect, the present invention provides an application of a lithium battery electrolyte solvent prepared by the above-mentioned preparation method, which is used to prepare a new electrolyte. The preparation method of the new electrolyte is as follows: the lithium battery electrolyte solvent is mixed with ethyl methyl fluorocarbonate and ethylene fluorocarbonate in a mass ratio of 1:1:1 to obtain a mixed solution; 1L of the mixed solution is taken, cooled to 5°C, 1 mol of lithium hexafluorophosphate is added, stirred evenly, and finally additives 1,3-propane sultone and vinylene carbonate are added to obtain the new electrolyte.

[0017] Furthermore, the added volumes of 1,3-propane sultone and vinylene carbonate are both 1-1.8% of the volume of the mixed solution.

[0018] This application has the following beneficial effects:

[0019] 1. The lithium ion electrolyte solvent prepared by the present invention has excellent stability under a high voltage of 5V. After participating in the preparation of a lithium battery, the capacity retention rate is still as high as 86.2% or more after 450 cycles at 5V.

[0020] 2. When the lithium ion electrolyte solvent prepared by the present invention is used to prepare a new electrolyte, the participation of fluoroethyl methyl carbonate and fluoroethylene carbonate can improve the stability of the prepared new electrolyte under a high voltage of 5V.

[0021] 3. The lithium ion electrolyte solvent prepared by the present invention is used to prepare a new electrolyte, which can significantly improve the stability of the prepared new electrolyte under a high voltage of 5V; and it can also improve the stability of the decrease in capacity retention rate of the prepared lithium battery with increasing cycle times, and avoid a significant increase in the decrease with increasing cycle times. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 , 5V charge and discharge curve of lithium ion battery made with novel electrolyte in Example 1 of the present invention;

[0023] Figure 2 , a graph showing the capacity retention rate corresponding to the 5V cycle times of a lithium-ion battery prepared with the novel electrolyte in Example 1 of the present invention;

[0024] Figure 3 , a comparative trend chart of the capacity retention rates corresponding to 5V cycle times (150, 300, and 450 times) of lithium-ion batteries prepared with the novel electrolytes of Examples 1-4 of the present invention and Comparative Examples 1-3. DETAILED DESCRIPTION

[0025] The present application is further described in detail below with reference to the embodiments.

[0026] Unless otherwise specified, the raw materials used in the examples and comparative examples of the present application are all commercially available.

[0027] Example 1: A lithium battery electrolyte solvent, the preparation method is as follows:

[0028] S1, halogenation reaction;

[0029] Add 300 kg of carbon tetrachloride and 118 kg of ethylene glycol diformate as raw material solvent to the reactor 1, stir, then add 5 kg of aluminum trichloride as catalyst, control the temperature (cool down) to 5 ° C, slowly add 75 kg of halogenating agent liquid chlorine, and turn on ultraviolet light at the same time, and control the light intensity at 900 μW / cm 2 After stirring and reacting for 2.5 hours, nitrogen gas with a purity of more than 99.9% was blown into the reactor from the bottom of the reactor. The tail gas was discharged and absorbed by the NaOH aqueous solution. Then, alkaline pH regulator NaHCO3 was slowly added to the reactor, and nitrogen gas was blown into the bottom of the reactor until the pH value reached a neutral value of about 7. Then, the addition of NaHCO3 was stopped to obtain a 1,6-dihalodiformic acid ethylene glycol ester solution.

[0030] S2, nucleophilic substitution reaction;

[0031] The 1,6-dihalogenated ethylene glycol dicarboxylate solution obtained in S1 was filtered and transferred to the second reactor (reflux reactor), heated to 69°C, and reflux was started. Under the reflux state, a mixed solution prepared by mixing sodium methoxide and carbon tetrachloride in equal mass proportions was slowly added. The mass of sodium methoxide was 115 kg. The time used for adding the mixed solution was controlled to be 2 hours. After the addition was completed, the reflux was continued for 1.7 hours, and then the temperature was lowered to room temperature. An acidic pH regulator (mass fraction) of 7% dilute hydrochloric acid was added until the pH value reached a neutral value of about 7 to obtain a 2,5-dioxoadipate dimethyl ester solution.

[0032] S3, distillation and purification;

[0033] The 2,5-dioxadipic acid dimethyl ester solution obtained in S2 is filtered, roughly distilled, washed, and rectified to obtain 2,5-dioxadipic acid dimethyl ester with a water content of 9.3 ppm and a purity of 99.99%, which is the electrolyte solvent for lithium batteries.

[0034] Specifically, first, the 2,5-dioxodimethyl adipate solution obtained by S2 is filtered through a filter to remove solid impurities and suspended matter therein. Then, the filtered solution is sent to a crude distillation tower for preliminary separation, and the tower top temperature is controlled between 60-70°C and the tower bottom temperature is between 80-90°C. In this process, low-boiling components (such as unreacted raw materials, by-products, etc.) will be evaporated, while the high-boiling target product will remain at the bottom of the tower. Then, the bottom product of the tower after crude distillation is washed with water to remove inorganic salts and other water-soluble impurities therein. During the washing process, it is necessary to stir fully to ensure that the impurities are fully dissolved in the water, stand for stratification, and separate the upper organic phase from the lower aqueous phase. Then, the washed organic phase is sent to a rectification tower for further separation and purification. The tower top temperature is controlled between 90-100°C and the tower bottom temperature is controlled between 110-120°C. In this process, the target product 2,5-dioxodimethyl adipate will be evaporated and condensed into a liquid in the tower top condenser. The product at the top of the tower is collected, which is dimethyl 2,5-dioxoadipate with high purity. The water content and purity of the product after distillation are tested, and the water content is 9.3 ppm and the purity is 99.99%.

[0035] A novel electrolyte solution is prepared as follows: a lithium battery electrolyte solvent is mixed with fluoroethyl methyl carbonate and fluoroethylene carbonate in a mass ratio of 1:1:1 to obtain a mixed solution. 1L of the mixed solution is taken, cooled to 5°C, 1 mol of lithium hexafluorophosphate (151.91 g) is added, stirred evenly, and finally 12 mL of additive 1,3-propane sultone and 12 mL of vinylene carbonate are added, mixed evenly, and the novel electrolyte solution is obtained.

[0036] Example 2: A lithium battery electrolyte solvent, the preparation method is as follows:

[0037] S1, halogenation reaction;

[0038] Add 300 kg of carbon tetrachloride and 118 kg of ethylene glycol diformate as raw material solvent to the reactor 1, stir, then add 5 kg of aluminum chloride as catalyst, control the temperature (cool down) to 5 °C, slowly add 75 kg of halogenating agent liquid chlorine, and turn on ultraviolet light at the same time, and control the light intensity at 800 μW / cm 2 After stirring and reacting for 2 hours, nitrogen with a purity of more than 99.9% was blown into the reactor from the bottom of the reactor. The tail gas was discharged and absorbed by the NaOH aqueous solution. Then, the alkaline pH regulator NaHCO3 was slowly added to the reactor, and nitrogen was blown into the reactor from the bottom of the reactor until the pH value reached a neutral value of about 7. Then, the addition of NaHCO3 was stopped to obtain a 1,6-dihalodiformic acid ethylene glycol ester solution.

[0039] S2, nucleophilic substitution reaction;

[0040] The 1,6-dihalogenated ethylene glycol dicarboxylate solution obtained in S1 was filtered and transferred to the second reactor (reflux reactor), heated to 61°C, and reflux was started. Under the reflux state, a mixed solution prepared by mixing sodium methoxide and carbon tetrachloride in equal mass proportions was slowly added. The mass of sodium methoxide was 115 kg, and the time used for adding the mixed solution was controlled to be 2 hours. After the addition was completed, the reflux was continued for 1.5 hours, and then the temperature was lowered to room temperature, and an acidic pH regulator (mass fraction) of 5% dilute hydrochloric acid was added until the pH value reached a neutral value of about 7 to obtain a 2,5-dioxoadipate dimethyl ester solution.

[0041] S3, distillation and purification;

[0042] The 2,5-dioxadipic acid dimethyl ester solution obtained in S2 is filtered, roughly distilled, washed, and rectified to obtain 2,5-dioxadipic acid dimethyl ester with a water content of 9.8 ppm and a purity of 99.93%, which is the electrolyte solvent for lithium batteries.

[0043] A novel electrolyte solution is prepared as follows: a lithium battery electrolyte solvent is mixed with fluoroethyl methyl carbonate and fluoroethylene carbonate in a mass ratio of 1:1:1 to obtain a mixed solution. 1L of the mixed solution is taken, cooled to 5°C, 1 mol of lithium hexafluorophosphate (151.91 g) is added, stirred evenly, and finally 10 mL of additive 1,3-propane sultone and 10 mL of vinylene carbonate are added, mixed evenly, and the novel electrolyte solution is obtained.

[0044] Example 3: A lithium battery electrolyte solvent, the preparation method is as follows:

[0045] S1, halogenation reaction;

[0046] Add 300 kg of carbon tetrachloride and 118 kg of ethylene glycol diformate as raw material solvent to the reactor 1, stir, then add 5 kg of aluminum chloride as catalyst, control the temperature (cool down) to 5 °C, slowly add 75 kg of halogenating agent liquid chlorine, and turn on ultraviolet light at the same time, and control the light intensity at 1200 μW / cm 2 After stirring and reacting for 3 hours, nitrogen with a purity of more than 99.9% was blown into the reactor from the bottom of the reactor. The tail gas was discharged and absorbed by the NaOH aqueous solution. Then, alkaline pH regulator NaHCO3 was slowly added to the reactor, and nitrogen was blown into the reactor from the bottom of the reactor until the pH value reached a neutral value of about 7. Then, the addition of NaHCO3 was stopped to obtain a 1,6-dihalodiformic acid ethylene glycol ester solution.

[0047] S2, nucleophilic substitution reaction;

[0048] The 1,6-dihalogenated ethylene glycol dicarboxylate solution obtained in S1 was filtered and transferred to the second reactor (reflux reactor), heated to 77°C, and reflux was started. Under the reflux state, a mixed solution prepared by mixing sodium methoxide and carbon tetrachloride in equal mass proportions was slowly added. The mass of sodium methoxide was 115 kg. The time used for adding the mixed solution was controlled to be 2 hours. After the addition was completed, the reflux was continued for 2 hours, and then the temperature was lowered to room temperature. An acidic pH regulator (mass fraction) of 10% dilute hydrochloric acid was added until the pH value reached a neutral value of about 7 to obtain a 2,5-dioxoadipate dimethyl ester solution.

[0049] S3, distillation and purification;

[0050] The 2,5-dioxadipic acid dimethyl ester solution obtained in S2 is filtered, roughly distilled, washed, and rectified to obtain 2,5-dioxadipic acid dimethyl ester with a water content of 9.8 ppm and a purity of 99.91%, which is the electrolyte solvent for lithium batteries.

[0051] A novel electrolyte is prepared as follows: a lithium battery electrolyte solvent is mixed with fluoroethyl methyl carbonate and fluoroethylene carbonate in a mass ratio of 1:1:1 to obtain a mixed solution. 1L of the mixed solution is taken, cooled to 5°C, 1 mol of lithium hexafluorophosphate (151.91g) is added, stirred evenly, and finally 18mL of additives 1,3-propane sultone and 18mL of vinylene carbonate are added, mixed evenly, and the novel electrolyte is obtained.

[0052] Example 4: A lithium battery electrolyte solvent, the preparation method is as follows:

[0053] S1, halogenation reaction;

[0054] Add 300 kg of carbon tetrachloride and 118 kg of ethylene glycol diformate as raw material solvent to the reactor 1, stir, then add 5 kg of aluminum chloride as catalyst, control the temperature (cool down) to 5 °C, slowly add 75 kg of halogenating agent liquid chlorine, and turn on ultraviolet light at the same time, and control the light intensity at 1000 μW / cm 2 After stirring and reacting for 2.5 hours, nitrogen gas with a purity of more than 99.9% was blown into the reactor from the bottom of the reactor. The tail gas was discharged and absorbed by the NaOH aqueous solution. Then, alkaline pH regulator NaHCO3 was slowly added to the reactor, and nitrogen gas was blown into the bottom of the reactor until the pH value reached a neutral value of about 7. Then, the addition of NaHCO3 was stopped to obtain a 1,6-dihalodiformic acid ethylene glycol ester solution.

[0055] S2, nucleophilic substitution reaction;

[0056] The 1,6-dihalogenated ethylene glycol dicarboxylate solution obtained in S1 was filtered and transferred to the second reactor (reflux reactor), heated to 72°C, and reflux was started. Under the reflux state, a mixed solution prepared by mixing sodium methoxide and carbon tetrachloride in equal mass proportions was slowly added. The mass of sodium methoxide was 115 kg, and the time used for adding the mixed solution was controlled to be 2 hours. After the addition was completed, the reflux was continued for 1.8 hours, and then the temperature was lowered to room temperature, and an acidic pH regulator (mass fraction) of 8% dilute hydrochloric acid was added until the pH value reached a neutral value of about 7 to obtain a 2,5-dioxoadipate dimethyl ester solution.

[0057] S3, distillation and purification;

[0058] The 2,5-dioxadipic acid dimethyl ester solution obtained in S2 is filtered, roughly distilled, washed, and rectified to obtain 2,5-dioxadipic acid dimethyl ester with a water content of 9.5 ppm and a purity of 99.96%, which is the electrolyte solvent for lithium batteries.

[0059] A novel electrolyte is prepared as follows: a lithium battery electrolyte solvent is mixed with fluoroethyl methyl carbonate and fluoroethylene carbonate in a mass ratio of 1:1:1 to obtain a mixed solution. 1L of the mixed solution is taken, cooled to 5°C, 1 mol of lithium hexafluorophosphate (151.91g) is added, stirred evenly, and finally 12mL of additive 1,3-propane sultone and 16mL of vinylene carbonate are added, mixed evenly, and the novel electrolyte is obtained.

[0060] Comparative Example 1: The difference between this comparative example and Example 1 is that in the preparation of the new electrolyte, the lithium battery electrolyte solvent is deleted.

[0061] Specifically, a novel electrolyte solution is prepared as follows: fluoroethyl methyl carbonate and fluoroethylene carbonate are mixed in a mass ratio of 1:1 to obtain a mixed solution. 1L of the mixed solution is taken, cooled to 5°C, 1 mol of lithium hexafluorophosphate (151.91 g) is added, stirred evenly, and finally 12 mL of additive 1,3-propane sultone and 12 mL of vinylene carbonate are added, mixed evenly, and the novel electrolyte solution is obtained.

[0062] Comparative Example 2: The difference between this comparative example and Example 1 is that in the preparation of the new electrolyte, fluoroethyl methyl carbonate is replaced by fluoroethylene carbonate.

[0063] Specifically, a novel electrolyte is prepared as follows: a lithium battery electrolyte solvent and fluoroethylene carbonate are mixed in a mass ratio of 1:2 to obtain a mixed solution. 1L of the mixed solution is taken, cooled to 5°C, 1 mol of lithium hexafluorophosphate (151.91g) is added, stirred evenly, and finally 12mL of additives 1,3-propane sultone and 12mL of vinylene carbonate are added, mixed evenly, and the novel electrolyte is obtained.

[0064] Comparative Example 3: The difference between this comparative example and Example 1 is that in the preparation of the new electrolyte, fluoroethylene carbonate is replaced by fluoroethyl methyl carbonate.

[0065] Specifically, a novel electrolyte is prepared as follows: a lithium battery electrolyte solvent and ethyl methyl fluorocarbonate are mixed in a mass ratio of 1:2 to obtain a mixed solution. 1L of the mixed solution is taken, cooled to 5°C, 1 mol of lithium hexafluorophosphate (151.91g) is added, stirred evenly, and finally 12mL of additives 1,3-propane sultone and 12mL of vinylene carbonate are added, mixed evenly, and the novel electrolyte is obtained.

[0066] Experimental example: Preparation of positive electrode: In a homogenization device, N-methylpyrrolidone is used as a solvent, lithium cobalt oxide, acetylene black, and polyvinylidene fluoride are uniformly mixed in a mass ratio of 96:2:2 to form a positive electrode slurry, and the positive electrode slurry is coated on a 12μm aluminum foil. After drying and cold pressing, a positive electrode sheet is obtained.

[0067] Preparation of negative electrode: In a homogenization device, deionized water is used as a solvent, and artificial graphite, acetylene black, styrene-butadiene rubber, and sodium carboxymethyl cellulose are uniformly mixed in a mass ratio of 94.5:2:2:1 to form a negative electrode slurry, and the negative electrode slurry is coated on an 8 μm copper foil. After drying and cold pressing, a negative electrode sheet is obtained.

[0068] Preparation of lithium-ion batteries: stack the positive electrode sheet, PE separator, and negative electrode sheet in order, so that the PE separator is between the positive electrode sheet and the negative electrode sheet to play an isolating role, and then wind them to obtain a bare battery cell; place the bare battery cell in an aluminum-plastic film shell, inject the electrolyte into the dried battery, and complete the preparation of the lithium-ion battery after vacuum packaging, standing, formation, shaping and other processes.

[0069] The electrolytes are novel electrolytes prepared from Examples 1-4 and Comparative Examples 1-3, respectively.

[0070] Normal temperature 25℃ cycle test: The prepared lithium-ion batteries were placed at normal temperature 25℃, charged to 5V at 1C constant current and constant voltage, and then discharged to 3V at 1C constant current, and the charge and discharge cycle test was performed, and the test data of 150, 300, and 450 cycles were recorded.

[0071] Table 1 shows the charge and discharge cycle test results of batteries using the novel electrolytes prepared in Examples 1-4 and Comparative Examples 1-3.

[0072] Table 1

[0073]

[0074] Result analysis: Analyze examples 1-4 and combine the data in Table 1 and Figure 1-3 It can be seen that the lithium ion electrolyte solvent prepared by the present invention has excellent stability under a high voltage of 5V. After being prepared into a lithium battery, the capacity retention rate is still as high as over 86.2% after 450 cycles at 5V.

[0075] Analyze Example 1 and Comparative Examples 2-3 and combine the data in Table 1 and Figure 3 It can be seen that when the lithium ion electrolyte solvent prepared by the present invention is used to prepare a new electrolyte, the participation of fluoroethyl methyl carbonate and fluoroethylene carbonate can improve the stability of the prepared new electrolyte under a high voltage of 5V.

[0076] Compared with Example 1, the capacity retention rates of Comparative Example 2 (without fluoroethyl methyl carbonate) and Comparative Example 3 (without fluoroethylene carbonate) decreased at the same 5V cycle number. However, as the cycle number increases, the decrease in Comparative Example 2 and Comparative Example 3 is basically consistent with the decrease in Example 1.

[0077] Analyze Example 1 and Comparative Example 1 and combine the data in Table 1 and Figure 3 It can be seen that the lithium ion electrolyte solvent prepared by the present invention is applied to prepare a new electrolyte, which can significantly improve the stability of the prepared new electrolyte under a high voltage of 5V.

[0078] Compared with Example 1, the capacity retention rate of Comparative Example 1 (not containing the lithium ion electrolyte solvent prepared by the present invention) is greatly reduced at the same 5V cycle number. Moreover, as the cycle number increases, the reduction range of Comparative Example 1 is increasingly greater than that of Example 1. This indicates that the lithium ion electrolyte solvent prepared by the present invention can also improve the stability of the reduction range of the capacity retention rate of the prepared lithium battery brought about by the increase in the cycle number.

[0079] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations. In addition, the various different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a lithium battery electrolyte solvent, characterized in that: The steps include: S1, halogenation reaction: add the raw material solvent and ethylene glycol diformate to the reactor 1, stir, add the catalyst, control the temperature at 5-10°C, add the halogenating agent, and turn on the ultraviolet light at a light intensity of 800-1200μW / cm 2 After stirring and reacting for 2-3 hours, nitrogen is blown into the reactor 1, and the waste gas is absorbed by the alkaline solution. Then, an alkaline pH regulator is added to the reactor 1, and nitrogen is blown at the same time to discharge the tail gas until the pH value reaches neutral, thereby obtaining a 1,6-dihalodiformic acid ethylene glycol ester solution; The raw material solvent is carbon tetrachloride; the catalyst is aluminum chloride; the halogenating agent is liquid chlorine; S2, nucleophilic substitution reaction; filter the 1,6-dihalodiformic acid ethylene glycol ester solution obtained in S1 and transfer it to the second reaction kettle, heat it to 61-77°C, add sodium methoxide solution under reflux, reflux for 1.5-2h, cool it to room temperature, add an acidic pH regulator until the pH value reaches neutral, and obtain 2,5-dioxoadipate dimethyl ester solution; S3, distillation and purification; filtering, roughly distilling, washing, and distilling the 2,5-dioxadipic acid dimethyl ester solution obtained in S2 to obtain the lithium battery electrolyte solvent.

2. The method for preparing a lithium battery electrolyte solvent according to claim 1, characterized in that: In S1, the molar ratio of the raw material solvent, ethylene glycol diformate and the halogenating agent is (2-3):1:(2.05-2.10).

3. The method for preparing a lithium battery electrolyte solvent according to claim 1, characterized in that: In S1, the alkaline pH regulator includes sodium bicarbonate or sodium carbonate; in S2, the acidic pH regulator is 5-10% dilute hydrochloric acid.

4. The method for preparing a lithium battery electrolyte solvent according to claim 1, characterized in that: In S2, the sodium methoxide solution is prepared by mixing sodium methoxide and a raw material solvent, and the molar ratio of the sodium methoxide to ethylene glycol diformate is (2.05-2.1):1.

Images