Electrolyte additive and method for its preparation

Abstract

The present application relates to a kind of electrolyte additives and its preparation method, belong to electrolyte technical field;The present application uses propenyl-1,3-sulfonic acid lactone as raw material, using the double bond of propenyl-1,3-sulfonic acid lactone and the amino group of 4-amino-2-(trifluoromethyl) thiophene occurs Michael addition reaction under the catalysis of 1,8-diazabicyclo (7-ene) Undecane, obtain the intermediate with tertiary amine structure, then through the quaternary ammonium salt reaction of tertiary amine structure of intermediate and bromo atom of ethyl bromoacetate, obtain additive, the additive of the present application and phosphate ester additive are compounded to obtain electrolyte additive, the present application is modified by propenyl-1,3-sulfonic acid lactone, introduce fluorinated alkyl, effectively reduce intermolecular force, weaken the dependence of electrolyte viscosity on temperature, improve the ionic conductivity of electrolyte under low temperature condition.

Description

Technical Field

[0001] This invention belongs to the field of electrolyte technology, specifically, it relates to an electrolyte additive and its preparation method. Background Technology

[0002] Lithium-ion batteries, as representatives of high-energy-density rechargeable batteries, have been widely used in consumer electronics, electric vehicles, and energy storage systems. Their performance optimization highly depends on the precise design of the electrolyte formulation, and additives, as key components for electrolyte function regulation, have a decisive impact on the battery's high and low temperature performance, cycle life, and safety. Sulfonate compounds (such as 1,3-propanesulfonate lactone (PS), propenyl-1,3-sulfonate lactone (PST), and their derivatives) have become an important class of additives for improving battery stability due to their unique molecular structures. These compounds can form a sulfonate-rich interfacial film at the positive and negative electrode interfaces, effectively suppressing redox side reactions of solvent molecules, significantly improving gas generation during high-temperature storage, and increasing capacity recovery. However, the poor ionic conductivity of the solid electrolyte interfacial film formed by sulfonate esters and the positive electrode electrolyte interfacial film may lead to a continuous increase in battery internal resistance. To address these technical shortcomings, this invention provides an electrolyte additive and its preparation method. Summary of the Invention

[0003] The purpose of this invention is to provide an electrolyte additive and its preparation method, so as to solve the problems mentioned in the background art.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing an electrolyte additive includes the following steps:

[0006] Step 1: Propylene-1,3-sulfonyl lactone, 4-amino-2-(trifluoromethyl)thiophene, 1,8-diazabicycloundec-7-ene, and N,N-dimethylformamide were mixed in a three-necked flask equipped with a condenser, thermometer, and magnetic stirrer. After turning on the magnetic stirrer, the mixture was reacted at 80-120℃ for 10-16 hours. After the reaction was completed, the solvent was removed by rotary evaporation and the intermediate was obtained by silica gel column chromatography.

[0007] The second step involves mixing the intermediate, ethyl bromoacetate, and N,N-dimethylformamide in a three-necked flask equipped with a condenser, thermometer, and magnetic stirrer. After turning on the magnetic stirrer, the mixture is reacted at a temperature of 50–110°C for 8–24 hours. After the reaction is completed, the solvent is removed by rotary evaporation of the reaction solution, and the first additive is obtained by silica gel column chromatography.

[0008] The third step is to combine the first additive and the second additive in any proportion to obtain an electrolyte additive.

[0009] Furthermore, the second additive is a phosphate ester additive, including at least one of tri(2,2,2-trifluoroethyl) phosphate and tri(1,1,1,2,2,2-hexafluoro-2-propyl) phosphate.

[0010] Furthermore, in the first step, the ratio of propenyl-1,3-sulfonyl lactone, 4-amino-2-(trifluoromethyl)thiophene, 1,8-diazabicycloundec-7-ene, and N,N-dimethylformamide is 0.03–0.04 mol: 0.01 mol: 0.004–0.006 mol: 40–60 mL.

[0011] Furthermore, the ratio of intermediate, ethyl bromoacetate, and N,N-dimethylformamide used in the second step is 0.005 mol: 0.006–0.01 mol: 40–60 mL.

[0012] Preferably, the mass ratio of the first additive to the second additive is 1 to 2:1.

[0013] An electrolyte additive is prepared by any of the above preparation steps.

[0014] The beneficial effects of this invention are:

[0015] 1) This invention uses propylene-1,3-sulfonyl lactone as raw material. The double bond of propylene-1,3-sulfonyl lactone reacts with the amino group of 4-amino-2-(trifluoromethyl)thiophene under the catalysis of 1,8-diazabicycloundec-7-ene to obtain an intermediate with a tertiary amine structure. Then, the tertiary amine structure of the intermediate reacts with the bromine atom of ethyl bromoacetate to obtain an additive. The additive of this invention is compounded with phosphate ester additives to obtain an electrolyte additive. This invention modifies propylene-1,3-sulfonyl lactone by introducing fluoroalkyl groups, which effectively reduces intermolecular forces, weakens the temperature dependence of electrolyte viscosity, and improves the ionic conductivity of the electrolyte under low temperature conditions.

[0016] 2) This invention modifies propylene-1,3-sulfonyl lactone, thereby changing the energy level orbitals of propylene-1,3-sulfonyl lactone, effectively optimizing the interfacial stability of sulfonyl lactone additives and effectively inhibiting the cyclic decay of electrolyte. Detailed Implementation

[0017] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the examples. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments in this application specification, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection claimed in this application.

[0018] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0019] The raw materials used in this invention are not particularly restricted in terms of their source; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0020] Example 1

[0021] A method for preparing an electrolyte additive includes the following steps:

[0022] Step 1: 0.03 mol of propenyl-1,3-sulfonyl lactone, 0.01 mol of 4-amino-2-(trifluoromethyl)thiophene, 0.006 mol of 1,8-diazabicycloundec-7-ene, and 40 mL of N,N-dimethylformamide were mixed in a three-necked flask equipped with a condenser, thermometer, and magnetic stirrer. After turning on the magnetic stirrer, the mixture was reacted at 80 °C for 16 h. After the reaction was completed, the solvent was removed by rotary evaporation and the intermediate was obtained by silica gel column chromatography.

[0023] Step 2: Mix 0.005 mol of intermediate, 0.006 mol of ethyl bromoacetate, and 40 mL of N,N-dimethylformamide in a three-necked flask equipped with a condenser, thermometer, and magnetic stirrer. After turning on the magnetic stirrer, react at 110°C for 8 hours. After the reaction is completed, remove the solvent by rotary evaporation and then elute by silica gel column chromatography to obtain the first additive.

[0024] The third step involves compounding the first additive and the second additive, tris(1,1,1,2,2,2-hexafluoro-2-propyl) phosphate, at a mass ratio of 1:1 to obtain an electrolyte additive.

[0025] An electrolyte additive is prepared by the above preparation steps.

[0026] Example 2

[0027] A method for preparing an electrolyte additive includes the following steps:

[0028] Step 1: 0.035 mol of propenyl-1,3-sulfonyl lactone, 0.01 mol of 4-amino-2-(trifluoromethyl)thiophene, 0.005 mol of 1,8-diazabicycloundec-7-ene, and 50 mL of N,N-dimethylformamide were mixed in a three-necked flask equipped with a condenser, thermometer, and magnetic stirrer. After turning on the magnetic stirrer, the mixture was reacted at 100 °C for 13 h. After the reaction was completed, the solvent was removed by rotary evaporation and the intermediate was obtained by silica gel column chromatography.

[0029] Step 2: Mix 0.005 mol of intermediate, 0.008 mol of ethyl bromoacetate, and 50 mL of N,N-dimethylformamide in a three-necked flask equipped with a condenser, thermometer, and magnetic stirrer. After turning on the magnetic stirrer, react at 80°C for 16 h. After the reaction is completed, remove the solvent by rotary evaporation and then elute by silica gel column chromatography to obtain the first additive.

[0030] The third step involves compounding the first additive and the second additive, tris(1,1,1,2,2,2-hexafluoro-2-propyl) phosphate, at a mass ratio of 1.5:1 to obtain an electrolyte additive.

[0031] An electrolyte additive is prepared by the above preparation steps.

[0032] Example 3

[0033] A method for preparing an electrolyte additive includes the following steps:

[0034] Step 1: 0.04 mol of propenyl-1,3-sulfonyl lactone, 0.01 mol of 4-amino-2-(trifluoromethyl)thiophene, 0.004 mol of 1,8-diazabicycloundec-7-ene, and 60 mL of N,N-dimethylformamide were mixed in a three-necked flask equipped with a condenser, thermometer, and magnetic stirrer. After turning on the magnetic stirrer, the mixture was reacted at 120 °C for 10 h. After the reaction was completed, the solvent was removed by rotary evaporation and the intermediate was obtained by silica gel column chromatography.

[0035] The second step involves mixing 0.005 mol of intermediate, 0.01 mol of ethyl bromoacetate, and 60 mL of N,N-dimethylformamide in a three-necked flask equipped with a condenser, thermometer, and magnetic stirrer. After turning on the magnetic stirrer, the mixture is reacted at 50°C for 24 h. After the reaction is completed, the solvent is removed by rotary evaporation and then eluted by silica gel column chromatography to obtain the first additive.

[0036] The third step involves compounding the first additive and the second additive, tri(2,2,2-trifluoroethyl) phosphate, at a mass ratio of 2:1 to obtain an electrolyte additive.

[0037] An electrolyte additive is prepared by the above preparation steps.

[0038] Comparative Example 1

[0039] The difference between this comparative example and Example 1 is that the first additive is not prepared, but rather the electrolyte additive is obtained by directly compounding propylene-1,3-sulfonyl lactone with the second additive.

[0040] A method for preparing an electrolyte additive includes the following steps:

[0041] An electrolyte additive was prepared by compounding propylene-1,3-sulfonyl lactone and the second additive, tris(1,1,1,2,2,2-hexafluoro-2-propyl) phosphate, in a mass ratio of 1:1.

[0042] An electrolyte additive is prepared by the above preparation steps.

[0043] Experimental Example 1

[0044] The electrolyte additives from Examples 1-3 and Comparative Example 1 were incorporated into a solvent (the solvent was a mixture of diethyl carbonate and ethylene carbonate in a mass ratio of 1:1) at a mass fraction of 3% to obtain an electrolyte. A battery was assembled using lithium manganese oxide as the positive electrode active material and graphite as the negative electrode. The high-temperature cycle capacity retention rate (45°C, 500 cycles) and low-temperature cycle capacity retention rate (-10°C, 50 cycles) of the assembled battery were tested. The test results are shown in Table 1.

[0045] Table 1

[0046]

[0047] The descriptions of the above embodiments are merely illustrative of the methods and core ideas of the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing an electrolyte additive, characterized in that, Includes the following steps: An intermediate was obtained by Michael addition reaction of propenyl-1,3-sulfonyl lactone and 4-amino-2-(trifluoromethyl)thiophene. The intermediate was then reacted with ethyl bromoacetate as a quaternary ammonium salt to obtain the first additive. The first additive was then combined with the second additive to obtain the electrolyte additive. The conditions for the Michael addition reaction of propenyl-1,3-sulfonyl lactone with 4-amino-2-(trifluoromethyl)thiophene are as follows: the reaction is carried out at a controlled temperature of 80-120℃ after mixing propenyl-1,3-sulfonyl lactone, 4-amino-2-(trifluoromethyl)thiophene, 1,8-diazabicycloundec-7-ene, and N,N-dimethylformamide. The conditions for the quaternary ammonium salt reaction between the intermediate and ethyl bromoacetate are as follows: the intermediate, ethyl bromoacetate, and N,N-dimethylformamide are mixed and the reaction is carried out at a controlled temperature of 50-110℃. The second additive is a phosphate ester additive.

2. The method for preparing an electrolyte additive according to claim 1, characterized in that, The Michael addition reaction takes 10–16 hours to occur.

3. The method for preparing an electrolyte additive according to claim 1, characterized in that, The time for the quaternary ammonium salt reaction to occur is 8–24 hours.

4. The method for preparing an electrolyte additive according to claim 1, characterized in that, The mass ratio of the first additive to the second additive is 1 to 2:

1.

5. The method for preparing an electrolyte additive according to claim 1, characterized in that, The ratio of propenyl-1,3-sulfonyl lactone to 4-amino-2-(trifluoromethyl)thiophene is 0.03–0.04 mol: 0.01 mol.

6. The method for preparing an electrolyte additive according to claim 1, characterized in that, The ratio of intermediate to ethyl bromoacetate is 0.005 mol: 0.006–0.01 mol.

7. An electrolyte additive, characterized in that, The electrolyte additive is prepared by the preparation method described in any one of claims 1 to 6.

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