Synthesis method of lithium difluoro (oxalato) borate

Abstract

The invention discloses a synthesis method of lithium difluoro (oxalato) borate. The synthesis method comprises the following operation steps: S1, introducing negative ions SF < 6-> into a triethyl boron (CH2CH3) 3B solution, and carrying out a primary reaction; s2, oxalic acid is added for an intermediate reaction; s3, lithium hydroxide is added for a final reaction, and a final reaction product lithium difluoro (oxalato) borate LiC2O4BF2 is generated; the preparation process is efficient, simple and environment-friendly, and is suitable for serving as a synthesis process route for realizing industrial large-scale production of lithium difluoro (oxalato) borate, and the large-scale industrialization level of the electrolyte additive is further improved.

Description

Technical Field

[0001] The present invention belongs to the field of electrolyte preparation, and particularly relates to a synthesis method of lithium difluorooxalate borate. Background Art

[0002] The electrolyte in a lithium-ion battery, as the main place where the battery operates, is usually composed of three parts: a lithium salt, an electrolyte additive solvent, and a solvent. Currently, the more commonly used electrolyte additives include lithium difluoro(oxalato)borate, vinylene sulfate, lithium difluoro(oxalato)phosphate, lithium tetrafluoro(oxalato)phosphate, etc. These additives have been proven to be able to effectively improve the performance of the SEI film and significantly improve the charge-discharge cycle performance of lithium-ion batteries.

[0003] In particular, the currently disclosed methods for synthesizing lithium difluorooxalate borate usually use raw materials that are environmentally unfriendly, highly acidic, and highly toxic to humans, and are also disadvantageous in the subsequent purification process, which is not conducive to realizing green chemical production. For example, the invention patent application with the publication number CN109232628A uses boron trifluoride, oxalic acid, and lithium fluoride to react to synthesize lithium difluorooxalate borate. The raw materials used are highly toxic gases, and the acidity of the prepared product is high. Another example is the invention patent application with the publication number CN111943969A, which uses a reaction by mixing lithium tetrafluoroborate, lithium oxalate, an organic solvent, and an auxiliary agent. The auxiliary agent is niobium pentachloride, niobium pentafluoride, or antimony pentafluoride, which is highly harmful to the environment and the subsequent treatment process is difficult.

[0004] Therefore, the applicant hopes to seek technical solutions to improve the above technical problems. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a synthesis method of lithium difluorooxalate borate, which has an efficient and simple preparation process, is environmentally friendly, is suitable as a synthetic process route for realizing large-scale industrial production of lithium difluorooxalate borate, and further improves the large-scale industrialization level of electrolyte additives.

[0006] The technical solution adopted by the present invention is as follows: A synthesis method of lithium difluorooxalate borate, comprising the following operating steps: S1. Introduce the negative ion SF6 - into a solution of triethylboron (CH2CH3)3B for a preliminary reaction; S2. Add oxalic acid for an intermediate reaction; S3. Add lithium hydroxide for a final reaction to generate the final reaction product lithium difluorooxalate borate LiC2O4BF2.

[0007] Preferably, high-voltage power is applied to the SF6 gas, so that the SF6 gas absorbs free electrons to form the negative ion SF6 - .

[0008] Preferably, in the step S1, the addition amount of the negative ion SF6 - is 1.0 - 3.0 times, preferably 1.2 - 1.5 times, of the molar amount of triethylboron (CH2CH3)3B.

[0009] Preferably, in the step S1, the temperature of the preliminary reaction is set at 20 - 40°C, preferably 20 - 25°C; the time of the preliminary reaction is 1 - 3 hours, preferably 1 - 1.5 hours.

[0010] Preferably, in the step S1, the solvent of the triethylboron (CH2CH3)3B solution is any one or a mixture of several of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, preferably dimethyl carbonate.

[0011] Preferably, in the step S2, the addition amount of oxalic acid is 1.0 - 2.5 times, preferably 1.2 - 2.0 times, of the molar amount of triethylboron (CH2CH3)3B.

[0012] Preferably, in the step S2, the temperature of the intermediate reaction is set at 20 - 40°C, preferably 20 - 25°C; the reaction time of the intermediate reaction is 1 - 3 hours, preferably 1.5 - 2 hours.

[0013] Preferably, in the step S3, the addition amount of lithium hydroxide is 1.0 - 2.5 times, preferably 1.2 - 2.2 times, of the molar amount of triethylboron (CH2CH3)3B.

[0014] Preferably, in the step S3, the temperature of the final reaction is set at 20 - 40°C, preferably 20 - 25°C; the reaction time of the final reaction is 1 - 3 hours, preferably 1.5 - 2 hours.

[0015] Preferably, after the step S3, there is further included a step S4: The solvent of the final reaction product lithium difluoro(oxalato)borate LiC2O4BF2 is filtered off to obtain solid lithium difluoro(oxalato)borate LiC2O4BF2 with a purity of ≧99%.

[0016] Preferably, the gas generated by the reaction contains butane, ethane, and sulfur tetrafluoride. After being transported through a gas vent pipeline to a water absorption tower for sulfur tetrafluoride absorption treatment, it is then connected to a flare system for combustion treatment of butane and ethane.

[0017] This application proposes a method suitable for environmentally friendly synthesis of lithium difluoro(oxalato)borate. The reaction equation is as follows: ; The synthesis method proposed in this application is efficient, simple, environmentally friendly and easy to purify, and is suitable as a synthetic process route for realizing the large-scale industrial production of lithium difluoro(oxalato)borate, further improving the large-scale industrialization level of electrolyte additives. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a step block diagram of the synthesis method of lithium difluoro(oxalato)borate under the specific embodiment of the present invention. SPECIFIC EMBODIMENTS

[0019] Please refer to Figure 1 As shown, this embodiment provides a synthesis method of lithium difluoro(oxalato)borate, including the following operating steps: S1. Introduce the negative ion SF6 - into the solution of triethylboron (CH2CH3)3B for preliminary reaction; preferably, apply high-voltage electricity to the SF6 gas so that the SF6 gas forms the negative ion SF6 in this step after absorbing free electrons - ; preferably, in this step S1, the addition amount of the negative ion SF6 - is 1.0 - 3.0 times the molar amount of triethylboron (CH2CH3)3B, more preferably 1.2 - 1.5 times; the temperature of the preliminary reaction is set at 20 - 40 °C, preferably 20 - 25 °C; the time of the preliminary reaction is 1 - 3 hours, more preferably 1 - 1.5 hours; the solvent of the triethylboron (CH2CH3)3B solution is any one or a mixture of several of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, more preferably dimethyl carbonate; S2. Add oxalic acid for intermediate reaction; preferably, in this step S2, the addition amount of oxalic acid is 1.0 - 2.5 times the molar amount of triethylboron (CH2CH3)3B, more preferably 1.2 - 2.0 times; the temperature of the intermediate reaction is set at 20 - 40 °C, more preferably 20 - 25 °C; the reaction time of the intermediate reaction is 1 - 3 hours, more preferably 1.5 - 2 hours; S3. Add lithium hydroxide for final reaction to generate the final reaction product lithium difluoro(oxalato)borate LiC2O4BF2; preferably, in this step S3, the addition amount of lithium hydroxide is 1.0 - 2.5 times the molar amount of triethylboron (CH2CH3)3B, more preferably 1.2 - 2.2 times; the temperature of the final reaction is set at 20 - 40 °C, more preferably 20 - 25 °C; the reaction time of the final reaction is 1 - 3 hours, more preferably 1.5 - 2 hours.

[0020] Preferably, in this embodiment, after step S3, there is also step S4: The final reaction product lithium difluoro(oxalato)borate LiC2O4BF2 is filtered to remove the solvent, obtaining solid lithium difluoro(oxalato)borate LiC2O4BF2 with a purity of ≧99%.

[0021] Preferably, in this embodiment, the gas generated by the reaction contains butane, ethane and sulfur tetrafluoride. After being transported through the gas vent pipeline to the water absorption tower for sulfur tetrafluoride absorption treatment, it is then connected to the flare system for combustion treatment of butane and ethane.

[0022] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0023] Based on the above-described embodiments, the present application further proposes the following specific embodiments: First of all, it should be noted that the sources of the reagent raw materials used in the following specific embodiments of the present invention are as follows: Triethylboron, oxalic acid, and lithium hydroxide are all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; For the remaining reagent raw materials, unless otherwise specified, they are all ordinary commercially available products.

[0024] The structural characterization of the reaction product is determined by nuclear magnetic resonance, and the spectrometer is Bruker AVANCE II 500MHz. Example 1:

[0025] In a triethylboron reaction kettle, triethylboron (97.99 g, 1 mol) is dissolved in dimethyl carbonate (783.92 g, 8.7 mol) according to a mass ratio of 1:8 to obtain a triethylboron (CH2CH3)3B solution; 48 liters (2 mol) of SF6 gas is subjected to high-voltage power-on to absorb free electrons to form negative ions SF6 - , which is introduced into the triethylboron reaction kettle and reacted at a temperature of 25°C for 1 hour; oxalic acid (135.05 g, 1.5 mol) is added to the reaction kettle and reacted at 25°C for 1.5 hours; finally, lithium hydroxide (38.32 g, 1.6 mol) is added to generate the final reaction product lithium difluoro(oxalato)borate LiC2O4BF2 (in the form of a lithium difluoro(oxalato)borate solution); the gas generated by the reaction contains butane, ethane and sulfur tetrafluoride. The gas vent pipeline first passes through the water absorption tower to absorb sulfur tetrafluoride, and the butane and ethane gases are connected to the flare system for combustion; After the reaction was completed, filtration was carried out under the conditions of vacuum -0.095 MPaG and 90 °C to remove all solvents in the lithium difluoro(oxalato)borate solution, obtaining a solid (133.7 g, 0.93 mol). It was confirmed by NMR analysis that this solid was lithium difluoro(oxalato)borate with a purity of 99.8%. Its structural formula is as follows:

[0026] The structural characterization results of the above reaction products are as follows: 19 F NMR (500 MHz, CHCl3-d): δ -146.78 – -147.36 (m). 11 B NMR (500 MHz, CHCl3-d): δ 2.02(s). Example 2:

[0027] In a triethylboron reaction kettle, triethylboron (98 g, 1 mol) was dissolved in dimethyl carbonate (783.93 g, 8.7 mol) in a mass ratio of 1:8 to obtain a triethylboron (CH2CH3)3B solution; 48 liters (2 mol) of SF6 gas was subjected to high-voltage power-on to absorb free electrons to form negative ions SF6 - , which was introduced into the triethylboron reaction kettle and reacted at a temperature of 25 °C for 1 hour; oxalic acid (180.06 g, 2 mol) was added to the reaction kettle and reacted at 25 °C for 1.5 hours; finally, lithium hydroxide (50.30 g, 2.1 mol) was added to generate the final reaction product lithium difluoro(oxalato)borate LiC2O4BF2 (in the form of a lithium difluoro(oxalato)borate solution); the gases generated in the reaction contained butane, ethane and sulfur tetrafluoride. The gas discharge pipeline first passed through a water absorption tower to absorb sulfur tetrafluoride, and the butane and ethane gases were connected to the flare system for combustion; After the reaction was completed, filtration was carried out under the conditions of vacuum -0.095 MPaG and 90 °C to remove all solvents in the lithium difluoro(oxalato)borate solution, obtaining a solid (129.38 g, 0.9 mol). It was confirmed by NMR analysis that this solid was lithium difluoro(oxalato)borate with a purity of 99.92%. Its structural formula is as follows:

[0028] The structural characterization results of the above reaction products are as follows: 19 F NMR (500 MHz, CHCl3-d): δ -146.78 – -147.36 (m). 11 B NMR (500 MHz, CHCl3-d): δ 2.02(s) Example 3:

[0029] In a triethylboron reaction kettle, triethylboron (97.98 g, 1 mol) was dissolved in ethyl methyl carbonate (905.67 g, 8.7 mol) according to a mass ratio of 1:8 to obtain a solution of triethylboron (CH2CH3)3B; 48 liters (2 mol) of SF6 gas was subjected to high-voltage power-on to absorb free electrons to form negative ions SF6 - , which was introduced into the triethylboron reaction kettle and reacted at a temperature of 25 °C for 1 hour; oxalic acid (135.08 g, 1.5 mol) was added to the reaction kettle and reacted at 25 °C for 1.5 hours; finally, lithium hydroxide (38.33 g, 1.6 mol) was added to generate the final reaction product lithium difluorooxalate borate LiC2O4BF2 (in the form of a lithium difluorooxalate borate solution); the gases generated by the reaction contained butane, ethane and sulfur tetrafluoride. The gas vent pipe first passed through a water absorption tower to absorb sulfur tetrafluoride, and the butane and ethane gases were connected to the flare system for combustion; After the reaction, filtration was carried out under the conditions of vacuum -0.095 MPaG and 90 °C to remove all solvents in the lithium difluorooxalate borate solution, and a solid (132.15 g, 0.92 mol) was obtained. Nuclear magnetic resonance analysis confirmed that the solid was lithium difluorooxalate borate with a purity of 99.73%. Its structural formula is as follows:

[0030] The structural characterization results of the above reaction products are as follows: 19 F NMR (500 MHz, CHCl3-d): δ -146.78 – -147.36 (m). 11 B NMR (500 MHz, CHCl3-d): δ 2.02(s).

[0031] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0032] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative manner of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for synthesizing lithium difluorooxalatoborate, characterized in that: The steps are as follows: S1, negative ion SF6 - Pass triethylborane (CH2CH3)3B solution into the reactor for preliminary reaction; S2, adding oxalic acid to carry out an intermediate reaction; S3. Add lithium hydroxide to carry out a final reaction to generate a final reaction product, lithium difluorooxalatoborate LiC2O4BF2.

2. The method for synthesizing lithium difluorooxalatoborate according to claim 1, characterized in that: The SF6 gas is energized with high voltage, so that the SF6 gas absorbs free electrons to form negative ions SF6. - .

3. The method for synthesizing lithium difluorooxalatoborate according to claim 1, characterized in that: In step S1, the negative ion SF6 - The amount added is 1.0-3.0 times the molar amount of triethylboron (CH2CH3)3B, preferably 1.2-1.5 times.

4. The method for synthesizing lithium difluorooxalatoborate according to claim 1, characterized in that: In the step S1, the temperature of the preliminary reaction is set to 20-40°C, preferably 20-25°C; the time of the preliminary reaction is 1-3 hours, preferably 1-1.5 hours.

5. The method for synthesizing lithium difluorooxalatoborate according to claim 1, characterized in that: In the step S1, the solvent of the triethylborane (CH2CH3)3B solution is any one of dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, or a mixture of several of them, preferably dimethyl carbonate.

6. The method for synthesizing lithium difluorooxalatoborate according to claim 1, characterized in that: In the step S2, the amount of oxalic acid added is 1.0-2.5 times, preferably 1.2-2.0 times, the molar amount of triethylboron (CH2CH3)3B.

7. The method for synthesizing lithium difluorooxalatoborate according to claim 1, characterized in that: In the step S2, the temperature of the intermediate reaction is set to 20-40°C, preferably 20-25°C; the reaction time of the intermediate reaction is 1-3 hours, preferably 1.5-2 hours.

8. The synthesis method according to claim 1, characterized in that: In step S3, the amount of lithium hydroxide added is 1.0-2.5 times, preferably 1.2-2.2 times, the molar amount of triethylboron (CH2CH3)3B.

9. The synthesis method according to claim 1, characterized in that: In the step S3, the temperature of the final reaction is set to 20-40°C, preferably 20-25°C; the reaction time of the final reaction is 1-3 hours, preferably 1.5-2 hours.

10. The synthesis method according to claim 1, characterized in that: After step S3, the method further includes step S4: The final reaction product, lithium difluorooxalate borate LiC2O4BF2, is filtered to remove the solvent to obtain solid lithium difluorooxalate borate LiC2O4BF2 with a purity of ≧99%.

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