A process for the preparation of tris(trimethylsilyl)borate

Abstract

The application belongs to the technical field of lithium ion batteries, and discloses a preparation method of tris(trimethylsilyl)borate. The preparation method of tris(trimethylsilyl)borate comprises the following steps: (1) preparing a mixed boric acid solution: stirring and dissolving anhydrous boric acid, a solvent and a catalyst in a flask in a glove box to form a mixed boric acid solution; (2) preparing tris(trimethylsilyl)borate: slowly dropping a silane reagent into the mixed boric acid solution prepared in step (1) under the protection of inert gas to react, obtaining tris(trimethylsilyl)borate crude product, and vacuum filtering and rotary evaporating the tris(trimethylsilyl)borate crude product to obtain tris(trimethylsilyl)borate product. The method has the advantages of simple process, low cost, low requirement for equipment, high product yield, high purity and good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a preparation method of tris(trimethylsilyl)borate. BACKGROUND

[0002] Lithium ion batteries are widely concerned due to their high working voltage, large energy density, long cycle life, low self-discharge rate, and "green" environmental protection. With the rapid development of the new energy industry, the market share of lithium ion batteries is gradually increasing, and the importance of lithium battery materials is increasingly prominent.

[0003] The electrolyte of lithium ion batteries is mainly composed of three parts: (1) electrolyte lithium salt, (2) organic solvent, and (3) additive. There are problems such as compatibility with positive and negative electrodes and safety in the electrolyte. Research has found that the use of additives can significantly improve certain properties of the battery, including electrode capacity, charge and discharge rate performance, positive and negative electrode matching performance, cycle performance or safety performance, etc. To adapt to the development of the industry, in the development process of lithium ion battery electrolyte, researching high-voltage and high-energy-density additives has become the top priority in the lithium battery industry.

[0004] Tris(trimethylsilyl)borate (TMSB) is an organic silicon compound containing boron. After adding it to the electrolyte of a lithium ion battery, the oxygen atoms generated by the B-O-Si breakage react with the negative active sites to reduce their activity, thereby achieving the effect of inhibiting the decomposition of the electrolyte on the negative active sites, improving the high-temperature storage performance and use performance of the battery, improving the low-temperature capacity performance of the battery, and prolonging the service life of the battery, etc., thus showing good application prospects. The trimethylsilyl ester compound decomposes earlier than the organic solvent under low temperature and high rate discharge conditions, and forms a SEI layer on the negative electrode surface including elements B, P and Si, thereby preventing the decomposition of the organic solvent. In addition, the SEI layer formed on the negative electrode surface allows lithium ions to be embedded on the surface of the electrode. Therefore, the internal resistance is reduced, thereby improving the electrochemical performance of the battery.

[0005] However, there are few reports on the preparation method of tris(trimethylsilyl)borate at present, and there is a lack of a preparation method of tris(trimethylsilyl)borate with simple process, low cost, low requirement for equipment, and high product purity. The existing patent technology CN201310268325.3 discloses a preparation method of high-purity trisilyl borate. The method reacts silazane and boric acid under the catalysis of organic amine to obtain a crude product, and the crude product is filtered and rectified to obtain high-purity trisilyl borate. The patent method claims that the raw materials are easy to obtain and cheap, the synthesis reaction conditions are mild, the operation is simple, the equipment investment is small, the production capacity of trisilyl borate is high, the yield is high, the energy consumption is low, the post-treatment is simple, and it is suitable for large-scale production. However, in fact, the yield of this method is only 71-83%. SUMMARY

[0006] The present application aims to overcome the deficiencies of the prior art, and provides a preparation method of tris(trimethylsilyl)borate, which has simple process, low cost, low requirement for equipment, high product yield, high purity and good application prospect.

[0007] To achieve the object of the present application, the preparation method of tris(trimethylsilyl)borate comprises the following steps:

[0008] (1) Preparation of boronic acid mixed solution: stirring and dissolving anhydrous boronic acid, solvent and catalyst in a flask in a glove box to form a boronic acid mixed solution;

[0009] (2) Preparation of tris(trimethylsilyl)borate: slowly adding a silane reagent to the boronic acid mixed solution prepared in step (1) under inert gas protection to obtain a crude tris(trimethylsilyl)borate, and then vacuum filtering and rotary evaporating the crude tris(trimethylsilyl)borate to obtain a tris(trimethylsilyl)borate product.

[0010] As a preferred embodiment of the present application, the molar ratio of boronic acid to solvent in step (1) is 1.6:(1-4.4), and the molar ratio of catalyst to solvent is 0.02:(1-1.2).

[0011] As a preferred embodiment of the present application, the solvent in step (1) is n-hexane.

[0012] As a preferred embodiment of the present application, the slow dropping in step (2) refers to a dropping time of 0.1 h or more, preferably a dropping time of 0.1-5 h, and more preferably 0.5-1.5 h.

[0013] As a preferred embodiment of the present application, the molar ratio of silane reagent to n-hexane in step (2) is (2-1):1.1.

[0014] As a preferred embodiment of the present application, the temperature of the reaction in step (2) is 60-80℃, and the reaction time is 12-48 h.

[0015] As a preferred embodiment of the present application, the silane reagent in step (2) is hexamethyldisilazane.

[0016] As a preferred embodiment of the present application, the catalyst in step (2) is one of tetraphenylphosphonium bromide, tetraphenylphosphonium bromide, triethylbenzylammonium chloride, and tetrabutylammonium bromide, for example, tetrabutylammonium bromide.

[0017] As a preferred embodiment of the present application, the rotary evaporation temperature in step (2) is 70-80℃, for example 75℃. The vacuum degree can be selected according to the actual situation of the production device during the rotary evaporation in step (2) of the present application, and the vacuum degree is preferably -0.05-0.2MPa, for example -0.1MPa.

[0018] Tris(trimethylsilyl)borate (TMSB) is a boron-containing organosilicon compound. After being added into a lithium ion battery electrolyte, the oxygen atom generated by B-O-Si rupture reacts with the negative active sites, thereby reducing the activity of the negative active sites, and achieving the effects of inhibiting the decomposition of the electrolyte on the negative active sites, improving the high-temperature storage performance and use performance of the battery, improving the low-temperature capacity performance of the battery, prolonging the service life of the battery, and the like.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] (1) The method of the present application has simple process, mild reaction conditions, few steps, and simple operation, and significantly optimizes the production process;

[0021] (2) The method of the present application has low cost and low requirement for equipment, and the raw materials are cheap and easy to obtain, and the obtained product has high purity, thereby effectively reducing the production cost;

[0022] (3) The product of the present application is particularly suitable for improving the performance of the electrolyte. The product is applied as an additive in the lithium ion battery electrolyte, is easy to form a film on the electrode surface, and the film has good effects of improving the high-temperature storage performance and use performance of the battery, improving the low-temperature capacity performance of the battery, prolonging the service life of the battery, and the like, and has wide application prospect and good industrial production potential in the field of lithium ion battery additive synthesis. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below. Additional aspects and advantages of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood by the practice of the present application. It should be understood that the following description is only used to explain the present application, and is not used to limit the present application.

[0024] The term "comprising", "including", "having" or "containing" or any other variant thereof used in this document means to cover non-exclusive inclusion. For example, a composition, step, method, article or apparatus that comprises a list of elements does not necessarily limit those elements to only those elements, but can include other elements not explicitly listed or inherent to such composition, step, method, article or apparatus.

[0025] The conjunctive term "comprising," used in the context of describing the chemical components of the compositions of the present application, does not preclude the presence of other components than those recited; nor, in the context of reciting a process, does it preclude additional, unrecited steps of the process. The conjunctive term "consisting of" excludes any element, step or ingredient not specified. If used in the claims, the phrase "consisting of" will have its ordinary meaning, determined by reference to the specification as a whole.

[0026] When equivalent, concentration, or other values or parameters are expressed in ranges, preferred ranges, or a series of upper preferred values and lower preferred values, it is to be understood that all ranges formed by any pair of an upper preferred value or limit and a lower preferred value or limit, whether or not such a range is separately disclosed, is expressly disclosed as a separate aspect of the application. For example, where a range of "1 to 5" is disclosed, it is to be understood that the description is equally applicable to the ranges of "1 to 4," "1 to 3," "1 to 2," "1 to 2 and 4 to 5," "1 to 3 and 5," etc. Where a range of values is recited, unless otherwise stated, the range is intended to include both the upper and lower limit values, and all intervening values of the range, whether stated or not.

[0027] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. "Optional" or "any of" means that the subsequently described event or circumstance can or can not occur, and that the description includes instances where the event occurs and instances where it does not.

[0028] Approximating language such as, for example, "approximately," "substantially," and "about" are terms of approximation. Any references to approximate or approximate values should be interpreted as meaning values that are acceptable within manufacturing tolerances, or as otherwise expected by one of ordinary skill in the art. In the present application and claims, ranges are used as endpoints to qualify and limit the range. Such ranges are inclusive of the endpoints that are used as termini. It is specifically intended that the endpoints be included within the ranges used. Unless otherwise specified, approximate language should be interpreted -10- (RL) - 12 / 17 / 2008

[0029] The indefinite articles "a" and "an," as used herein in the specification, unless clearly indicated to the contrary, should be interpreted to mean "at least one." The indefinite articles "a" and "an," as used in this application are to be construed to mean "one or more" unless specified to the contrary or clear from the context to be directed only to the singular.

[0030] Moreover, the description herein of any aspect or embodiment of the application using terms such as "one embodiment", "an embodiment", "at least one embodiment", "some embodiments" or "some examples" or the like is intended to convey that the described implementation, feature or characteristic is included in at least one implementation or example of the application. Therefore, these terms in no way preclude that there can be additional implementation, feature or characteristic, and / or that other implementation, feature or characteristic can be used. Furthermore, the inclusion of a feature or characteristic in at least one example or implementation of the application does not exclude that the feature or characteristic can be used in other examples or implementations of the application.

[0031] Example 1

[0032] In the glove box, 0.25 mol of boric acid was added to a three-necked flask, then 150 mL of solvent n-hexane was added, 7.4 g of tetrabutylammonium bromide was added, and after being heated to 70°C, 2 mol of hexamethyldisilazane was added dropwise for reaction, the dropwise time was 0, and the reaction was incubated for 24 h to obtain crude tri (trimethylsilyl) borate. The crude tri (trimethylsilyl) borate was subjected to post-treatment filtration operation under a vacuum of -0.1 MPa to obtain a colorless transparent liquid. Finally, the crude product obtained by post-treatment was rotary evaporated under a vacuum of -0.1 MPa and a temperature of 75°C, and the colorless transparent liquid evaporated by rotary evaporation was subjected to GC test analysis to determine that it was solvent n-hexane; at the same time, the remaining substances in the flask were solvent n-hexane and product tri (trimethylsilyl) borate, and the product purity was 99.9% and the yield was 87%.

[0033] Example 2

[0034] In the glove box, 0.25 mol of boric acid was added to a three-necked flask, then 150 mL of solvent n-hexane was added, 7.4 g of tetrabutylammonium bromide was added, and after being heated to 70°C, 2 mol of hexamethyldisilazane was added dropwise for reaction, the dropwise time was 0.5 h, and the reaction was incubated for 24 h to obtain crude tri (trimethylsilyl) borate. The crude tri (trimethylsilyl) borate was subjected to post-treatment filtration operation under a vacuum of -0.1 MPa to obtain a colorless transparent liquid. Finally, the crude product obtained by post-treatment was rotary evaporated under a vacuum of -0.1 MPa and a temperature of 75°C, and the colorless transparent liquid evaporated by rotary evaporation was subjected to GC test analysis to determine that it was solvent n-hexane; at the same time, the remaining substances in the flask were solvent n-hexane and product tri (trimethylsilyl) borate, and the product purity was 99.9% and the yield was 89%.

[0035] Example 3

[0036] In the glove box, 0.25 mol of boric acid was added to a three-necked flask, then 150 mL of solvent n-hexane was added, 7.4 g of tetrabutylammonium bromide was added, after being heated to 70°C, 2 mol of hexamethyldisilazane was added dropwise for reaction, the dropwise time was 1 h, and the reaction was kept for 24 h to obtain a crude product of tris(trimethylsilyl) borate. The crude product of tris(trimethylsilyl) borate was subjected to post-treatment filtration operation under a vacuum degree of -0.1 MPa to obtain a colorless transparent liquid. Finally, the crude product obtained by post-treatment was subjected to rotary evaporation under a condition of -0.1 MPa and a temperature of 75°C, and the colorless transparent liquid obtained by rotary evaporation was subjected to GC test analysis to determine that it was solvent n-hexane; at the same time, the remaining substances in the flask were solvent n-hexane and product tris(trimethylsilyl) borate, the purity of the product was 99.9%, and the yield was 95%.

[0037] Example 4

[0038] In the glove box, 0.25 mol of boric acid was added to a three-necked flask, then 150 mL of solvent n-hexane was added, 7.4 g of tetrabutylammonium bromide was added, after being heated to 70°C, 2 mol of hexamethyldisilazane was added dropwise for reaction, the dropwise time was 1 h, and the reaction was kept for 24 h to obtain a crude product of tris(trimethylsilyl) borate. The crude product of tris(trimethylsilyl) borate was subjected to post-treatment filtration operation under a vacuum degree of -0.1 MPa to obtain a colorless transparent liquid. Finally, the crude product obtained by post-treatment was subjected to rotary evaporation under a condition of -0.1 MPa and a temperature of 75°C, and the colorless transparent liquid obtained by rotary evaporation was subjected to GC test analysis to determine that it was solvent n-hexane; at the same time, the remaining substances in the flask were solvent n-hexane and product tris(trimethylsilyl) borate, the purity of the product was 99.9%, and the yield was 95%.

[0039] Example 5

[0040] In the glove box, 0.375 mol of boric acid was added to a three-necked flask, then 150 mL of solvent n-hexane was added, 6 g of tetrabutylammonium bromide was added, after being heated to 75°C, 2 mol of hexamethyldisilazane was added dropwise for reaction, the dropwise time was 1.5 h, and the reaction was kept for 24 h to obtain a crude product of tris(trimethylsilyl) borate. The crude product of tris(trimethylsilyl) borate was subjected to post-treatment filtration operation under a vacuum degree of -0.1 MPa to obtain a colorless transparent liquid. Finally, the crude product obtained by post-treatment was subjected to rotary evaporation under a condition of -0.1 MPa and a temperature of 75°C, and the colorless transparent liquid obtained by rotary evaporation was subjected to GC test analysis to determine that it was solvent n-hexane; at the same time, the remaining substances in the flask were solvent n-hexane and product tris(trimethylsilyl) borate, the purity of the product was 99.6%, and the yield was 88%.

[0041] According to the above synthesis method, different synthesis experiments were carried out under different conditions, and the specific experimental conditions are shown in Table 1:

[0042] Table 1 Main experimental parameters of examples and comparative examples

[0043]

[0044]

[0045] By analyzing the reaction conditions and product parameters of the above examples, the following conclusions are mainly obtained:

[0046] ① When the target product is synthesized by the method described in the present application, a target product with relatively high purity can be obtained, and the purity is relatively stable;

[0047] ② It can be found from the comparative examples that the purity and yield of the product obtained by using hexamethyldisilazane as a raw material to provide silicon atoms are higher than those of the products obtained by using trimethylsilic acetate, hexamethyldisilthiane and trimethylchlorosilane as silicon atom providers. This may be because when hexamethyldisilazane is used as a raw material, the by-product is NH3, which can be directly absorbed by water and easily removed without residue.

[0048] ③ It can be found from the comparison of the comparative examples and the examples that in the preparation process of tris(trimethylsilyl)borate, different catalysts have different effects on the yield and purity of the product. Among them, tetrabutylammonium bromide as a catalyst is better than triphenylphosphonium bromide and triethylbenzylammonium chloride. However, it should be noted that the use of excessive catalyst will increase the viscosity of the reaction liquid and affect the reaction rate.

[0049] Those skilled in the art will readily understand that the above only describes the embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A process for the preparation of tri (trimethylsilyl) borate, characterized by, The preparation method of the tri (trimethylsilyl) borate comprises the following steps: (1) preparing a mixed boric acid solution: stirring and dissolving anhydrous boric acid, a solvent and a catalyst in a flask in a glove box to form a mixed boric acid solution; (2) preparing tri (trimethylsilyl) borate: slowly adding a silane reagent to the mixed boric acid solution prepared in step (1) under inert gas protection to obtain a crude tri (trimethylsilyl) borate, and then performing vacuum filtration and rotary evaporation on the crude tri (trimethylsilyl) borate to obtain a tri (trimethylsilyl) borate product; The slow dropping in step (2) refers to a dropping time of 1 h, the reaction temperature in step (2) is 70 DEG C, and the reaction time is 24 h; the silane reagent in step (2) is hexamethyldisilazane, and the catalyst in step (1) is tetrabutylammonium bromide.

2. The method for preparing tris(trimethylsilane)boronic acid ester according to claim 1, characterized in that, The molar ratio of boric acid to solvent in step (1) is 1.6: (1-4.4), and the molar ratio of catalyst to solvent is 0.02: (1-1.2).

3. The method for preparing tris(trimethylsilane)boronic acid ester according to claim 1, characterized in that, The solvent in step (1) is n-hexane.

4. The method for preparing tris(trimethylsilane)boronic acid ester according to claim 3, characterized in that, The molar ratio of silane reagent to n-hexane in step (2) is (2-1): 1.

1.

5. The method for preparing tris(trimethylsilane)boronic acid ester according to claim 1, characterized in that, The rotary evaporation temperature in step (2) is 70-80 DEG C.

6. The method for preparing tris(trimethylsilane)boronic acid ester according to claim 1, characterized in that, The rotary evaporation temperature in step (2) is 75 DEG C.

7. The method for preparing tris(trimethylsilane)boronic acid ester according to claim 1, characterized in that, The vacuum degree during rotary evaporation in step (2) is -0.05-0.2 MPa.

8. The method of claim 1, wherein the trimethylsilyl borate is prepared by the process comprising: reacting trimethylsilyl chloride with sodium borohydride in the presence of a solvent to form trimethylsilyl borate; and removing the solvent from the trimethylsilyl borate. The vacuum degree during rotary evaporation in step (2) is -0.1 MPa.

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