Sodium tetrafluoroborate and its preparation method and application

Abstract

The present invention relates to the field of sodium ion battery technology and provides sodium tetrafluoroborate, a preparation method, and applications thereof. The method comprises the following steps: introducing a gas into a sodium bifluoride solution, mixing, and concentrating the solution to obtain the sodium tetrafluoroborate. The method utilizes a one-step method to synthesize the sodium tetrafluoroborate, which is low-cost, simple, fast, and thorough, shortening the process time. No water is produced as a by-product, and the product yield reaches 92.2%. The resulting sodium tetrafluoroborate has a purity of 99.9%.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to sodium tetrafluoroborate, a preparation method thereof, and applications thereof. Background Art

[0002] Sodium tetrafluoroborate has high conductivity and low electrolyte viscosity and can be used as a primary salt or additive in sodium-ion battery electrolytes. Currently, sodium tetrafluoroborate production typically involves preparing fluoroboric acid from boric acid and hydrofluoric acid, then neutralizing it with sodium carbonate. The neutralized solution is then concentrated, crystallized, separated, washed, and dried to produce sodium tetrafluoroborate. This process uses highly hazardous hydrofluoric acid, and the water content of the neutralizer affects product quality. Summary of the Invention

[0003] The purpose of the present invention is to provide sodium tetrafluoroborate and a preparation method and application thereof.

[0004] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0005] The invention provides a preparation method of sodium tetrafluoroborate, comprising the following steps: introducing gas into a sodium bifluoride solution, mixing, and concentrating to obtain the sodium tetrafluoroborate.

[0006] Preferably, the solvent of the sodium bifluoride solution is one or more of dichloromethane, dichloroethane, methanol, ethanol, n-propanol, n-butanol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methyl acetate, ethyl acetate, propyl acetate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetone and acetonitrile.

[0007] Preferably, the mass ratio of sodium bifluoride to solvent in the sodium bifluoride solution is 120-140:180-220.

[0008] Preferably, the gas is boron trichloride.

[0009] Preferably, the mass ratio of sodium bifluoride to boron trichloride is 120-140:105-125.

[0010] Preferably, the starting temperature of the mixing is 15-30°C, and the target temperature of the mixing is 30-60°C.

[0011] Preferably, the mixed temperature is increased in a gradient manner, the temperature difference between adjacent temperatures is 5 to 10° C., and the insulation time of a single temperature is 0.1 to 0.5 h.

[0012] Preferably, the concentration temperature is ≤60°C.

[0013] The present invention also provides sodium tetrafluoroborate obtained by the preparation method.

[0014] The present invention also provides application of the sodium tetrafluoroborate in sodium ion batteries.

[0015] The present invention has the following beneficial effects:

[0016] The present invention provides a method for preparing sodium tetrafluoroborate, comprising the steps of introducing a gas into a sodium bifluoride solution, mixing the mixture, and concentrating the mixture to obtain the sodium tetrafluoroborate. The method employs a one-step method for synthesizing sodium tetrafluoroborate, which is low-cost, simple, fast, and thorough, shortens the process time, eliminates water by-products, and provides a high product yield. Furthermore, the resulting sodium tetrafluoroborate is of high purity.

[0017] The reaction principle of the present invention is: 2NaHF2+BCl3=NaBF4+NaCl+2HCl. DETAILED DESCRIPTION

[0018] The invention provides a preparation method of sodium tetrafluoroborate, comprising the following steps: introducing gas into a sodium bifluoride solution, mixing, and concentrating to obtain the sodium tetrafluoroborate.

[0019] In the present invention, the sodium bifluoride solution is obtained by mixing sodium bifluoride and a solvent.

[0020] In the present invention, the mixing temperature is preferably 15 to 30°C, more preferably 18 to 27°C, and even more preferably 20 to 25°C.

[0021] In the present invention, the solvent of the sodium bifluoride solution is preferably one or more of dichloromethane, dichloroethane, methanol, ethanol, n-propanol, n-butanol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methyl acetate, ethyl acetate, propyl acetate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetone and acetonitrile.

[0022] In the present invention, the mass ratio of sodium bifluoride to solvent in the sodium bifluoride solution is preferably 120-140:180-220, more preferably 125-135:190-210, and even more preferably 128-132:195-205.

[0023] In the present invention, the gas is preferably boron trichloride.

[0024] In the present invention, the time for introducing the gas is preferably 0.3 to 0.6 h, more preferably 0.4 to 0.5 h, and even more preferably 0.44 to 0.46 h.

[0025] In the present invention, the mass ratio of sodium bifluoride to boron trichloride is preferably 120-140:105-125, more preferably 125-135:110-120, and even more preferably 128-132:114-116.

[0026] In the present invention, the starting temperature of the mixing is preferably 15 to 30°C, more preferably 18 to 27°C, and even more preferably 20 to 25°C.

[0027] The target temperature of the mixing is preferably 30°C to 60°C, more preferably 35°C to 55°C, and even more preferably 40°C to 50°C.

[0028] In the present invention, there is a temperature difference between the starting temperature and the target temperature.

[0029] In the present invention, the mixing temperature increase method is preferably gradient temperature increase.

[0030] In the present invention, the temperature difference between adjacent temperatures is preferably 5-10°C, more preferably 6-9°C, more preferably 7-8°C, and the insulation time of a single temperature is preferably 0.1-0.5h, more preferably 0.2-0.4h, more preferably 0.25-0.35h.

[0031] In the present invention, the mixing process is carried out under ultrasonic conditions.

[0032] In the present invention, the frequency of the ultrasound is preferably 22 to 26 KHz, more preferably 23 to 25 KHz, and even more preferably 23.5 to 24.5 KHz.

[0033] In the present invention, nitrogen is introduced after the mixing is completed to purge excess boron trichloride and generated hydrogen chloride gas.

[0034] In the present invention, the time for introducing nitrogen is preferably 0.2 to 0.8 h, more preferably 0.3 to 0.7 h, and even more preferably 0.4 to 0.6 h.

[0035] In the present invention, the sodium tetrafluoroborate is obtained by introducing nitrogen, filtering, concentrating, filtering again, washing and drying.

[0036] In the present invention, the filtrate obtained by filtration is concentrated.

[0037] In the present invention, the concentration temperature is preferably ≤60°C, more preferably ≤50°C, and even more preferably ≤45°C.

[0038] In the present invention, the filter cake obtained by re-filtration is washed by soaking-rinsing, and the washing solvent is preferably dichloromethane.

[0039] In the present invention, the drying process is completed under a nitrogen atmosphere, and the drying temperature is preferably 70-140°C, more preferably 80-130°C, and even more preferably 100-110°C.

[0040] The present invention also provides sodium tetrafluoroborate obtained by the preparation method.

[0041] The present invention also provides application of the sodium tetrafluoroborate in sodium ion batteries.

[0042] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0043] Example 1

[0044] At 20 ° C, 130.2 g of sodium bifluoride was added to 200 g of dimethyl carbonate and stirred thoroughly to obtain a sodium bifluoride solution. 117.3 g of boron trichloride gas was introduced under ultrasonic conditions at a frequency of 23 kHz for 0.3 h. The mixed solution was heated at a gradient temperature of 20-25-30 ° C. and each temperature was kept warm for 0.3 h for a total of 0.9 h. The reaction was completed. Nitrogen was purged for 0.5 h and then filtered. The filtrate was concentrated under reduced pressure at 50 ° C and filtered again. The filter cake was soaked and rinsed three times with 500 g of dichloromethane and dried at 100 ° C under nitrogen protection to obtain 99.8 g of sodium tetrafluoroborate with a purity of 99.7% and a yield of 90.9%.

[0045] Example 2

[0046] At 30°C, 127.1 g of sodium bifluoride was added to 200 g of dimethyl carbonate and stirred thoroughly to obtain a sodium bifluoride solution. 117.3 g of boron trichloride gas was introduced under ultrasonic conditions at a frequency of 24 kHz for 0.6 h. The reaction was then carried out by increasing the temperature gradually from 30 to 35°C. The temperature was kept at each temperature for 0.3 h for a total of 0.6 h until the reaction was completed. The residual boron trichloride and hydrogen chloride gas were purged with nitrogen for 0.5 h and then filtered. The filtrate was concentrated under reduced pressure at 45°C and filtered again. The filter cake was soaked and rinsed four times with 600 g of dichloromethane and dried at 95°C under nitrogen to obtain 100.7 g of sodium tetrafluoroborate with a purity of 99.82% and a yield of 91.5%.

[0047] Example 3

[0048] At 25 ° C, 129.6 g of sodium bifluoride was added to 210 g of ethyl acetate and stirred thoroughly to obtain a sodium bifluoride solution. 117.3 g of boron trichloride gas was introduced under ultrasonic conditions at a frequency of 26 kHz for 0.5 h. The reaction was then carried out at a gradient temperature of 25-30-35-40 ° C. The temperature was kept at each temperature for 0.1 h for a total of 0.4 h. The reaction was completed. Nitrogen was purged for 0.4 h and then filtered. The filtrate was concentrated under reduced pressure at 55 ° C and filtered again. The filter cake was soaked and rinsed 5 times with 700 g of dichloromethane and dried at 85 ° C under nitrogen protection to obtain 101.3 g of sodium tetrafluoroborate with a purity of 99.9% and a yield of 92.2%.

[0049] As can be seen from the above examples, the present invention provides a method for preparing sodium tetrafluoroborate, comprising the steps of: introducing a gas into a sodium bifluoride solution, mixing, and concentrating to obtain the sodium tetrafluoroborate. The present invention utilizes a one-step method for synthesizing sodium tetrafluoroborate, which is low-cost, simple, fast, and thorough, shortens the process time, does not produce water by-products, and achieves a product yield as high as 92.2%. The resulting sodium tetrafluoroborate has a purity of 99.9%.

[0050] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing sodium tetrafluoroborate, characterized in that: The following steps are involved: Passing gas into the sodium bifluoride solution, mixing, and concentrating to obtain the sodium tetrafluoroborate; The gas is boron trichloride; The starting temperature of the mixing is 15 to 30°C, and the target temperature of the mixing is 30 to 60°C; The solvent of the sodium bifluoride solution is one or more of dichloromethane, dichloroethane, methanol, ethanol, n-propanol, n-butanol, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, methyl acetate, ethyl acetate, propyl acetate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetone and acetonitrile; The mass ratio of the sodium bifluoride to the boron trichloride is 120-140:105-125.

2. The preparation method according to claim 1, wherein The mass ratio of sodium bifluoride to solvent in the sodium bifluoride solution is 120-140:180-220.

3. The preparation method according to claim 1, wherein The mixed temperature is increased in a gradient manner, the temperature difference between adjacent temperatures is 5 to 10° C., and the insulation time of a single temperature is 0.1 to 0.5 h.

4. The preparation method according to claim 1, wherein The concentration temperature is ≤60°C.