Preparation method of lithium difluoro (oxalato) borate

Abstract

The invention discloses a preparation method of lithium difluoro (oxalato) borate, which comprises the following step: reacting anhydrous lithium metaborate with oxalyl fluoride in an organic solvent to generate the lithium difluoro (oxalato) borate. The method is simple in process, high in product conversion rate, free of three wastes and environmentally friendly, and the prepared product is high in purity, few in impurities and suitable for the field of lithium ion batteries.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chemical synthesis, in particular to a preparation method of lithium difluoro(oxalato)borate. BACKGROUND

[0002] The lithium fluorinated oxalate salt can be used as an electrolyte additive for lithium ion batteries, which can effectively improve the structure of the passivation film, reduce the impedance of the passivation film, and improve the stability of the positive and negative electrodes of the lithium ion battery in high and low temperature cycles, and has an important role in improving the performance of the current high-voltage power battery and ternary high-nickel power battery system. Among them, lithium difluoro(oxalate)borate is a representative product, and its structural formula is as follows:

[0003]

[0004] The technical route of lithium difluoro(oxalate)borate disclosed in the prior art mainly includes the following types:

[0005] (1) Lithium tetrafluoroborate and oxalic acid are used as main raw materials, and a reaction aid is added in an organic solvent to prepare lithium difluoro(oxalate)borate. For example, patent EP1195834A2 uses lithium hexafluoroisopropyl alcohol as a reaction aid; patent EP1308449A uses silicon tetrachloride as a reaction aid; and patent CN103113396A uses HF as a reaction aid. Most of the aids used in this method have safety problems, and the equipment and operation are required to be high, and impurities such as chloride ions, organic fluorides, silicon-containing compounds, HF, etc. are introduced, which causes the product to have low purity or acidity, impurity ions, etc. Exceeding, affecting the application in lithium ion batteries; in addition, this method has great difficulty in treating three wastes, such as silicon tetrafluoride, hydrogen chloride, hydrogen fluoride, etc., which are easy to pollute the environment.

[0006] (2) Lithium difluoro(oxalate)borate is prepared by using boron trifluoride and lithium salt containing oxalic acid as raw materials. For example, patents CN101139352A and CN101648963A respectively report that lithium oxalate and boron trifluoride complex react in an organic solvent at a molar ratio of 1:1 and 2:1; and patent CN104230970A changes the reaction to be carried out in a ball mill; and the literature J. Cent. South Univ., 2018 (25): 550-560 discloses hydrogen lithium oxalate as a lithium salt. This method will produce a large amount of by-products, and the post-treatment process is difficult.

[0007] (Three) with boric acid, oxalic acid, lithium salt, fluoride and other raw materials to generate lithium difluorooxalate borate, this method uses ball milling, calcination and other solid phase method, a small part of the water as the medium. Such as patent CN103265569A uses boric acid solution, hydrofluoric acid, oxalic acid, lithium hydroxide and other raw materials by toluene water and other means of reaction; patent CN102260282B uses boric acid or boric anhydride, lithium fluoride is fully mixed by ball milling, under the protection of inert gas, 350-400℃ in muffle furnace for 20 hours, then heated to mix with water, then add oxalic acid. This method is very easy to hydrolyze lithium difluorooxalate borate, whether with water as the medium, the reaction will generate water, the purity of the product is not high, the key indicators such as acidity, moisture, etc. Can not be used in lithium battery application.

[0008] (Four) other methods. Such as patent CN103483368A uses lithium ion exchange method; patent CN107226821A uses lithium difluorooxalate borate fluoride method; patent CN113045594A uses fluorinated lithium difluorooxalate borate and fluorinated lithium oxalate phosphate coproduction method. These methods also cannot avoid the problems of the above three methods, such as complex reaction steps, many impurities in the product. SUMMARY

[0009] In order to solve the above technical problems, the present application provides a preparation method of lithium difluorooxalate borate, which is simple, high in product conversion rate and high in product purity, and safe and environmentally friendly.

[0010] The purpose of the present application is achieved by the following technical scheme:

[0011] A preparation method of lithium difluorooxalate borate, in which anhydrous metaborate lithium and oxalyl fluoride are reacted in an organic solvent to generate lithium difluorooxalate borate.

[0012] The reaction equation of the method of the present application is shown in formula I:

[0013]

[0014] The reaction of the present application can be carried out in a wide temperature range. Specifically, the reaction temperature of the method of the present application is 0-100℃; preferably, the reaction temperature is 10-60℃.

[0015] The raw material ratio of the present application is not particularly limited, but from the point of view of atomic economy, the molar ratio of the anhydrous metaborate lithium and oxalyl fluoride is 1:0.5-1:3, preferably 1:0.8-1:1.5, and further preferably 1:0.95-1:1.2.

[0016] The oxalyl fluoride can be commercially available or prepared by reacting oxalyl chloride with a fluorinating agent, including potassium fluoride, hydrogen fluoride, hydrogen fluoride triethylamine salt, hydrogen fluoride pyridine salt, etc. Regardless of the way of obtaining the oxalyl fluoride, the excessive chlorine content will affect the quality of the final product, and preferably, the chlorine content of the oxalyl fluoride is < 5 ppm. In addition, due to the low boiling point of oxalyl fluoride, the present application uses low-temperature reflux condensation, closed pressurization, gas absorption and other means to reduce the volatilization loss of oxalyl fluoride in the process, which is not particularly limited.

[0017] In the prior art, oxalyl fluoride exists in both cis and trans planar configurations (Journal of Baoji University of Arts and Sciences, Vol 27, No. 1, PP. 49-53, Mar 2007), and the reactivity of which only has a small difference, and both can occur the reaction described in the present application.

[0018] The organic solvent can be selected as long as it is an aprotic solvent that does not have side reactions with the raw materials or products. Specifically, the organic solvent is selected from at least one of a chain carbonate, a cyclic carbonate, an aliphatic ester solvent, an ether solvent, a halogenated hydrocarbon solvent, or an organic solvent containing N, P, S and other heteroatoms. The chain carbonate is selected from at least one of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; the cyclic carbonate is selected from at least one of ethylene glycol carbonate, propylene glycol carbonate, and butanediol carbonate; the aliphatic ester solvent is selected from at least one of ethyl acetate, propyl acetate, and butyl acetate; the ether solvent is selected from at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, tetrahydrofuran, dioxane, and methyl tetrahydrofuran; the halogenated hydrocarbon solvent is selected from dichloromethane or dichloroethane; and the organic solvent containing N, P, S and other heteroatoms is selected from at least one of acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, methyl pyrrolidone, sulfolane, and hexamethylphosphoric triamide.

[0019] As a preferred, the organic solvent is a solvent with a larger solubility for the product, selected from at least one of dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, ethylene glycol dimethyl ether, or acetonitrile, and more preferably, the organic solvent is selected from at least one of acetonitrile or ethylene glycol dimethyl ether.

[0020] The amount of the organic solvent is not particularly limited. Preferably, the mass ratio of the organic solvent to anhydrous lithium metaborate is 3:1 to 10:1.

[0021] Because moisture in the reaction system reacts with oxaloyl fluoride to generate HF, the acidity of the product increases. The anhydrous lithium metaborate has a moisture content of <1000 ppm, preferably <10 ppm. The organic solvent has a moisture content of <1000 ppm, preferably <5 ppm. After the reaction, the product can be further purified by distillation, crystallization, filtration, etc., to obtain a solid product or a solution of a certain concentration. There are no particular limitations on the post-processing.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. The method described in this invention does not require the use of highly toxic and irritating raw materials such as boron trifluoride and chlorosilane, nor does it require the introduction of other additives. The resulting product has high purity, few impurities, and generates no waste, making it environmentally friendly.

[0024] 2. The method described in this invention is simple in process and easy to operate, with an atom utilization rate of up to 100% and a high reaction yield. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0026] Example 1

[0027] In a dry environment with an ambient dew point <-40℃, 50.0 g of anhydrous lithium metaborate (1 mol) and 500 mL of anhydrous acetonitrile were added to a flask equipped with a thermometer, reflux condenser, and stirrer. 103.4 g of oxaloyl fluoride (1.1 mol) was slowly added over 2 hours, with the temperature controlled at around 25℃. After the addition was complete, the mixture was stirred for about 8 hours until most of the solid dissolved. The reaction solution was first filtered to remove a small amount of undissolved lithium metaborate raw material (which can be reused in the next reaction), and then distilled and concentrated to precipitate the solid, yielding 136.5 g of solid, with a yield of 94.9%.

[0028] Nuclear magnetic resonance (NMR) analysis of boron and fluorine spectra confirmed that the solid was lithium difluorooxalate borate. Ion chromatography analysis showed that the purity of lithium difluorooxalate borate was 99.8%, and the chloride ion concentration was <1 ppm. Titration revealed an acidity of 27 ppm.

[0029] Example 2

[0030] The operation in this embodiment is the same as in embodiment 1, except that the amount of oxalyl fluoride is 112.8g (1.2mol), and all other operations remain unchanged.

[0031] The final yield was 140.8 g of lithium difluorooxalate borate solid, with a yield of 97.8%. Testing showed that the purity of lithium difluorooxalate borate was 99.7%, chloride ion concentration was <1 ppm, and acidity was 25 ppm.

[0032] Example 3

[0033] The operation in this embodiment is the same as in embodiment 1, except that the solvent is changed to 500mL ethylene glycol dimethyl ether, and all other operations remain the same.

[0034] The final yield was 136.9 g of lithium difluorooxalate borate solid, with a yield of 95.1%. Testing showed that the purity of lithium difluorooxalate borate was 99.8%, chloride ion concentration was <1 ppm, and acidity was 30 ppm.

[0035] Example 4

[0036] The operation in this embodiment is the same as in embodiment 1, except that the reaction temperature is changed to 10°C, while other operations remain unchanged.

[0037] The final yield was 139.0 g of lithium difluorooxalate borate solid, with a yield of 96.5%. Testing showed that the purity of lithium difluorooxalate borate was 99.8%, chloride ion concentration was <1 ppm, and acidity was 21 ppm.

[0038] Example 5

[0039] The operation in this embodiment is the same as in embodiment 1, except that the amount of oxalyl fluoride is 94g (1mol), and all other operations remain unchanged.

[0040] The final yield was 134.6 g of lithium difluorooxalate borate solid, with a yield of 93.7%. Testing showed that the purity of lithium difluorooxalate borate was 99.5%, chloride ion concentration was <1 ppm, and acidity was 20 ppm.

[0041] Example 6

[0042] The operation in this embodiment is the same as in embodiment 1, except that 2.0g of the 50.0g lithium metaborate used is the unreacted raw material obtained by filtration in embodiment 1. All other operations remain unchanged.

[0043] The final yield was 136.6 g of lithium difluorooxalate borate solid, with a yield of 94.9%. Testing showed that the purity of lithium difluorooxalate borate was 99.8%, chloride ion concentration was <1 ppm, and acidity was 29 ppm.

[0044] Example 7

[0045] The operation in this embodiment is the same as in embodiment 1, except that the amount of oxalyl fluoride is 89.3g (0.95mol), and all other operations remain unchanged.

[0046] The final yield was 129.7 g of lithium difluorooxalate borate solid, with a yield of 90.1%. Testing showed that the purity of lithium difluorooxalate borate was 99.6%, chloride ion concentration was <1 ppm, and acidity was 22 ppm.

[0047] Example 8

[0048] The operation in this embodiment is the same as in embodiment 1, except that the reaction temperature is changed to 60°C, while other operations remain unchanged.

[0049] The final yield was 134.6 g of lithium difluorooxalate borate solid, with a yield of 93.5%. Testing showed that the purity of lithium difluorooxalate borate was 99.5%, chloride ion concentration was <1 ppm, and acidity was 35 ppm.

Claims

1. A process for the preparation of lithium bisfluorosulfonylborate, characterized in that, The anhydrous metaborate lithium and oxalyl fluoride are reacted in an organic solvent to generate lithium difluoro(oxalato)borate.

2. The method of preparing lithium bisfluorooxalato borate according to claim 1, characterized in that, The molar ratio of the anhydrous metaborate lithium and oxalyl fluoride is 1:0.5-1:

3.

3. The method of preparing lithium bisfluorooxalato borate according to claim 1, characterized in that, The molar ratio of the anhydrous metaborate lithium and oxalyl fluoride is 1:0.8-1:1.

5.

4. The method of preparing lithium bisfluorooxalato borate according to claim 1, characterized by, The molar ratio of the anhydrous metaborate lithium and oxalyl fluoride is 1:0.95-1:1.

2.

5. The method of preparing lithium bisfluorooxalato borate according to claim 1, wherein, The organic solvent is at least one selected from a chain carbonate, a cyclic carbonate, an aliphatic ester solvent, an ether solvent, a halogenated hydrocarbon solvent or an organic solvent containing heteroatoms such as N, P and S.

6. The method of preparing lithium bisfluorooxalato borate according to claim 5, characterized in that, The chain carbonate is at least one selected from dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate; the cyclic carbonate is at least one selected from ethylene glycol carbonate, propylene glycol carbonate and butylene glycol carbonate; the aliphatic ester solvent is at least one selected from ethyl acetate, propyl acetate and butyl acetate; the ether solvent is at least one selected from dimethyl ether of ethylene glycol, diethyl ether of ethylene glycol, methyl ethyl ether of ethylene glycol, tetrahydrofuran, dioxane and methyl tetrahydrofuran; the halogenated hydrocarbon solvent is selected from dichloromethane or dichloroethane; and the organic solvent containing heteroatoms such as N, P and S is at least one selected from acetonitrile, N,N-dimethylformamide, N,N-dimethylacetamide, methyl pyrrolidone, sulfolane and hexamethylphosphoric triamide.

7. The method of preparing lithium bisfluorooxalato borate according to claim 6, characterized in that, The organic solvent is at least one selected from dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl ether of ethylene glycol or acetonitrile.

8. The method of preparing lithium bisfluorooxalato borate according to claim 1, wherein, The reaction temperature is 0-100℃.

9. The method of preparing lithium bisfluorooxalato borate according to claim 1, wherein, The reaction temperature is 10-60℃.

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