Preparation method and application of trimethylsilyl compound

Abstract

The application discloses a preparation method and application of a trimethylsilyl compound, and relates to the technical field of lithium ion battery additives. The preparation method is as follows: 4-bromobenzophenone, bis(triphenylphosphine)palladium chloride, triphenylphosphine and cuprous iodide are added into a container, then triethylamine and tetrahydrofuran are added to dissolve the mixture, trimethylethynylsilane is added to react, and product A is obtained after treatment; product A and zinc powder are added into the container, tetrahydrofuran is added first, and then the mixture is subjected to cooling treatment, titanium tetrachloride is added to react after cooling, and a trimethylsilyl compound is obtained after treatment. The trimethylsilyl compound prepared by the application has the ability to capture moisture or acid, and has a low density. When the trimethylsilyl compound is used as an additive in a lithium ion battery, the capacity retention rate of the battery can be improved, the stability of the electrode material can be improved, the electrode charge transfer impedance can be reduced, the discharge capacity ratio of the electrode can be improved, and the performance of the lithium ion battery can be improved.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery additives, specifically to a method for preparing a trimethylsilyl compound and its application. Background Technology

[0002] Lithium-ion batteries with layered transition metal oxide cathodes and graphite anodes are ubiquitous in portable electronics and electric vehicles due to their excellent cycle stability and high energy. In the electrochemical cycle of such batteries, lithium ions are de-intercalated from one electrode and intercalated into another, which is highly efficient and reversible.

[0003] Lithium-ion batteries have been commercialized since 1991. Layered oxides, such as LiMO2 (where M = Co, Ni, Mn), are the preferred cathode materials in commercial batteries. However, to further improve energy density, cathode materials need to operate at voltages exceeding 4.0V and maintain performance even during battery aging. (Li Ni) x Mn y Co z The O2(x+y+z=1) cathode has attracted much attention due to its adjustable properties, which are sufficient to balance the energy density, safety, and cycle stability of the battery. The cathode-electrolyte interface contributes the most to the cathode impedance, which is a major component of the overall cell impedance. As the battery ages, the cathode and overall cell impedance gradually increase, eventually reaching a level where charging and discharging become extremely slow; this phenomenon is known as "impedance rise." To improve the energy density of lithium-ion batteries, Li / Li ratios exceeding 4V are required. + Layered lithium oxide cathodes operate at high potentials. However, when continuously exposed to such high potentials, the battery materials gradually age, requiring the protection of electrolyte additives. To enhance battery surface protection and improve battery performance, this invention provides a method for preparing trimethylsilyl-based compounds and their applications. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing trimethylsilyl compounds and their applications. The prepared trimethylsilyl compounds have the ability to capture moisture or acid and have a low density. When used as additives in lithium-ion batteries, they can improve the battery's capacity retention rate, enhance the stability of electrode materials, reduce electrode charge transfer impedance, and increase the electrode's discharge capacity ratio, thereby improving the performance of lithium-ion batteries.

[0005] To achieve the above objectives, the present invention provides a method for preparing trimethylsilyl compounds, comprising the following steps:

[0006] S1. Add 4-bromobenzophenone, bis(triphenylphosphine)palladium chloride, triphenylphosphine and cuprous iodide to a dry container. After evacuating the container to a vacuum state, fill it with nitrogen gas. Then add triethylamine and tetrahydrofuran to the container and heat to 50°C to dissolve. Then add trimethylethynylsilane to the container and react at 50°C for 12 hours.

[0007] S2. Dry the solvent after the reaction in step S1, then extract and dry the reaction product to remove the extraction solvent and obtain the crude product. Then separate and purify the crude product to obtain product A.

[0008] S3. Add product A and zinc powder obtained in step S2 to a dry container. After the container is evacuated to a vacuum state, nitrogen gas is introduced. Then tetrahydrofuran is added to the container and the container is cooled in an ice bath. After cooling, titanium tetrachloride is added to the container. After removing the ice bath, the reaction is carried out for half an hour and then heated to 70°C. The reaction is stirred for 12 hours.

[0009] S4. Add dilute hydrochloric acid to the container after the reaction in step S3, then blow the solvent dry, extract and dry the obtained product, remove the extraction solvent to obtain the crude product, and then separate and purify the crude product to separate the final product trimethylsilyl compound.

[0010] The synthetic route is as follows:

[0011]

[0012] Preferably, in step S1, the molar ratio of 4-bromobenzophenone to trimethylethynylsilane is 10:13.

[0013] Preferably, in step S1, the molar ratio of bis(triphenylphosphine)palladium chloride, triphenylphosphine, and cuprous iodide is 1:3:2.

[0014] Preferably, in step S3, the molar ratio of product A, zinc powder, and titanium tetrachloride is 1:1:1.

[0015] Preferably, in both steps S2 and S4, the solvent is dried using compressed air.

[0016] Preferably, the extraction and drying operations in steps S2 and S4 are both: extracting the reaction product with dichloromethane and water, combining the organic layers, and drying with anhydrous magnesium sulfate.

[0017] Preferably, in both steps S2 and S4, a rotary evaporator is used to remove the extraction solvent to obtain the crude product, and the crude product is purified by column chromatography, wherein the eluent used is a mixed solvent of n-hexane / dichloromethane.

[0018] Application of trimethylsilyl compounds prepared by the method in lithium-ion batteries.

[0019] Therefore, this invention provides a method for preparing trimethylsilyl compounds and their applications, with the following specific beneficial effects:

[0020] (1) Trimethylsilyl compounds have the ability to capture moisture or acid and have a low density;

[0021] (2) Applying trimethylsilyl compounds as additives to lithium-ion batteries can enhance the surface protection of the battery and improve battery performance. They react with lithium hexafluorophosphate in the electrolyte to produce the secondary product difluorophosphoroxytrimethylsilane, which serves as the cathode protection in the electrolyte, preventing the occurrence of harmful reactions, thereby improving the capacity retention rate and reducing the rise in impedance of high-voltage lithium-ion batteries.

[0022] (3) Improve the battery capacity retention rate, improve the stability of electrode materials, and at the same time improve the discharge capacity ratio of the electrode.

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0024] Figure 1 The trimethylsilyl compounds prepared in this invention are used in deuterated chloroform. 1 1H NMR spectrum, with solvent peaks marked by asterisks *;

[0025] Figure 2 The trimethylsilyl compounds prepared in this invention are used in deuterated chloroform. 13 CNMR carbon spectrum, with solvent peaks marked with an asterisk *;

[0026] Figure 3 This is under the condition of a current density of 0.5C for LiNi 0.8 Co 0.1 Mn 0.1 Cyclic performance curves of the O2 electrode in electrolyte I and electrolyte II, respectively;

[0027] Figure 4 It is LiNi 0.8 Co 0.1 Mn 0.1 Electrochemical impedance curves of the O2 electrode after standing in electrolyte I and electrolyte II for 12 h;

[0028] Figure 5 This is under the condition of a current density of 0.1C for LiNi 0.8 Co 0.1 Mn 0.1The charge-discharge curves of the O2 electrode in electrolyte I and electrolyte II during the first week. Detailed Implementation

[0029] The following detailed description of embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] Example

[0031] This invention provides a method for preparing trimethylsilyl compounds, comprising the following steps:

[0032] S1. In a dry three-necked flask, add 20 mmol of 4-bromobenzophenone as a reactant, 0.4 mmol of bis(triphenylphosphine)palladium chloride, 1.2 mmol of triphenylphosphine, and 0.8 mmol of cuprous iodide as catalysts. Use a vacuum pump to evacuate the three-necked flask to a vacuum state and then fill it with nitrogen. Repeat this operation three times. Then, use a syringe to add 160 mL of triethylamine and 30 mL of tetrahydrofuran to the three-necked flask. Heat to 50 °C. After the catalyst dissolves in the solvent, add 26 mmol of trimethylethynylsilane as a reactant to the three-necked flask to carry out the reaction. Maintain the reaction temperature at 50 °C. After 12 hours, the reaction is complete.

[0033] S2. After the reaction is complete, the solvent is dried with compressed air. The resulting reaction product is extracted with dichloromethane and water. The combined organic layers are dried with anhydrous magnesium sulfate. The extraction solvent is then removed using a rotary evaporator to obtain the crude product. Finally, the crude product is purified by column chromatography using a mixed solvent of n-hexane and dichloromethane as the eluent. Product A is separated with a yield of 92%.

[0034] S3. Add 20 mmol of product A and 20 mmol of zinc powder to a dry three-necked flask. Use a vacuum pump to evacuate the three-necked flask to a vacuum state and then fill it with nitrogen. Repeat this operation three times. Then, use a syringe to add 160 mL of tetrahydrofuran solvent to the three-necked flask. Cool the three-necked flask with an ice bath. After cooling, slowly add 20 mmol of titanium tetrachloride to the three-necked flask. After removing the ice bath and reacting for 0.5 hours, heat the system to 70°C and stir for 12 hours to complete the reaction.

[0035] S4. After the reaction is complete, 100 mL of dilute hydrochloric acid is added to the three-necked flask, and the solvent is dried by compressed air. The reaction product is extracted with dichloromethane and water. After the organic layers are combined, they are dried with anhydrous magnesium sulfate. Then, the extraction solvent is removed by rotary evaporation to obtain the crude product. Finally, the crude product is purified by column chromatography, using a mixed solvent of n-hexane / dichloromethane as the eluent. The final product, trimethylsilyl compounds, is separated with a yield of 90%.

[0036] like Figure 1 and Figure 2 As shown, Figure 1 The different hydrogen atoms in the structure were characterized. The hydrogen atoms in different positions appeared in different positions. There were a total of 18 hydrogen atoms on the benzene ring, and the corresponding peak appeared at about 7 ppm. There were 8 hydrogen atoms adjacent to the carbon-carbon double bond and 4 hydrogen atoms adjacent to the triple bond. The total number of hydrogen atoms on trimethylsilane was 18, and the corresponding peak appeared at about 0.8 ppm. Figure 2 The structure was characterized by different carbon atoms, with carbon atoms at different positions appearing in different locations. Carbon atoms at triple bonds were the characteristic peaks, with the peak of the triple bond carbon closest to the benzene ring appearing at around 105 ppm, and the peak of the triple bond carbon closest to the silicon atom appearing at around 95 ppm. Figure 1 and Figure 2 This demonstrates that the structure of the compound is accurate.

[0037] The trimethylsilyl compounds prepared in the above examples were used as additives to perform performance tests on lithium-ion battery electrodes. The specific test method is as follows:

[0038] 1. Preparation of electrolyte and electrode materials

[0039] Electrolyte I was prepared by dissolving 1M lithium hexafluorophosphate in a mixed solvent of ethylene carbonate / dimethyl carbonate (volume ratio 1:1); electrolyte II was prepared by dissolving 0.5 wt% of the trimethylsilyl compound prepared in this invention in electrolyte I.

[0040] With LiNi 0.8 Co 0.1 Mn 0.1 O2 is used as the positive electrode material, and graphite-based carbon is used as the negative electrode material. The electrodes are vacuum dried at 80°C for 12 hours. Button batteries are made using electrolytes I and II. The batteries are assembled in a nitrogen glove box with a water and oxygen concentration of less than 0.01 ppm. The separator is a PE polyethylene membrane.

[0041] 2. Conduct electrochemical performance tests.

[0042] Depend on Figure 3The electrode cycling performance curves show that after 100 cycles, the electrode capacity in electrolyte II decreased from 195 mAh / g to 183 mAh / g, while in electrolyte I, the electrode capacity decreased from 191 mAh / g to 173 mAh / g. The electrode capacity in electrolyte II decreased more slowly, and the decrease was also less than that in electrolyte I. The corresponding capacity retention rates were 93.8% and 90.6%, respectively. This indicates that the experimental battery with trimethylsilyl compounds added as additives has better cycle stability than the battery without additives. The trimethylsilyl compounds improve the cycling performance of LiNi... 0.8 Co 0.1 Mn 0.1 Cyclic stability of O2 electrode materials.

[0043] Depend on Figure 4 The electrochemical impedance spectroscopy (EIS) curves show that the Nyquist plots of both the additive-free electrolyte I and the additive-added electrolyte II consist of a semicircle and a diagonal line. However, the charge transfer impedance of the electrode in the additive-added electrolyte II is significantly lower than that of the electrode in the additive-free electrolyte I. This indicates that the trimethylsilyl compound, acting as an additive, reduces the electrode charge transfer impedance.

[0044] Depend on Figure 5 The charge-discharge curves for the first week show that, in electrolyte II and electrolyte I, LiNi 0.8 Co 0.1 Mn 0.1 The charge-discharge plateau of the O2 electrode is similar, representing the lithium-ion insertion / extraction process of the electrode material. The first-cycle discharge specific capacity of the electrode in electrolyte II is 214 mAh / g, while that in electrolyte I is 210 mAh / g. The higher first-cycle discharge specific capacity of electrolyte II compared to electrolyte I indicates that adding trimethylsilyl compounds as additives can improve the first-cycle discharge specific capacity of the electrode.

[0045] Therefore, the present invention provides a method for preparing trimethylsilyl compounds. The obtained trimethylsilyl compounds have the ability to capture moisture or acid and have a low density. When used as an additive in lithium-ion batteries, they can improve the battery's capacity retention rate, improve the stability of electrode materials, reduce electrode charge transfer impedance, and increase the electrode's discharge capacity ratio, thereby improving the performance of lithium-ion batteries.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. The application of a trimethylsilyl-based compound in lithium-ion batteries, characterized in that, The preparation method of this compound includes the following steps: S1. Add 4-bromobenzophenone, bis(triphenylphosphine)palladium chloride, triphenylphosphine and cuprous iodide to a dry container. After evacuating the container to a vacuum state, fill it with nitrogen gas. Then add triethylamine and tetrahydrofuran to the container and heat to 50°C to dissolve. Then add trimethylethynylsilane to the container and react at 50°C for 12 hours. S2. Dry the solvent after the reaction in step S1, then extract and dry the reaction product to remove the extraction solvent and obtain the crude product. Then separate and purify the crude product to obtain product A. S3. Add product A and zinc powder obtained in step S2 to a dry container. After the container is evacuated to a vacuum state, nitrogen gas is introduced. Then tetrahydrofuran is added to the container and the container is cooled in an ice bath. After cooling, titanium tetrachloride is added to the container. After removing the ice bath, the reaction is carried out for half an hour and then heated to 70°C. The reaction is stirred for 12 hours. S4. Add dilute hydrochloric acid to the container after the reaction in step S3, then blow the solvent dry, extract and dry the obtained product, remove the extraction solvent to obtain the crude product, and then separate and purify the crude product to separate the final product trimethylsilyl compound. The synthetic route is as follows: 。 2. The application of a trimethylsilyl-based compound according to claim 1 in a lithium-ion battery, characterized in that: In step S1, the molar ratio of 4-bromobenzophenone to trimethylethynylsilane is 10:

13.

3. The application of a trimethylsilyl-based compound according to claim 1 in a lithium-ion battery, characterized in that: In step S1, the molar ratio of bis(triphenylphosphine)palladium chloride, triphenylphosphine, and cuprous iodide is 1:3:

2.

4. The application of a trimethylsilyl-based compound according to claim 1 in a lithium-ion battery, characterized in that: In step S3, the molar ratio of product A, zinc powder, and titanium tetrachloride is 1:1:

1.

5. The application of a trimethylsilyl-based compound according to claim 1 in a lithium-ion battery, characterized in that: In both steps S2 and S4, compressed air is used to dry the solvent.

6. The application of a trimethylsilyl-based compound according to claim 1 in a lithium-ion battery, characterized in that, The extraction and drying operations in steps S2 and S4 are as follows: the reaction product is extracted with dichloromethane and water, and the organic layers are combined and then dried with anhydrous magnesium sulfate.

7. The application of a trimethylsilyl-based compound according to claim 1 in a lithium-ion battery, characterized in that: In both steps S2 and S4, a rotary evaporator is used to remove the extraction solvent to obtain the crude product. The crude product is then purified by column chromatography, where the eluent is a mixed solvent of n-hexane and dichloromethane.

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