Preparation method of liquid lithium tetrafluoroborate

Abstract

The invention discloses a preparation method of liquid lithium tetrafluoroborate, which comprises the following steps: fluorating anhydrous lithium chloride by anhydrous hydrogen fluoride in an organic solvent to obtain lithium fluoride, then introducing boron trifluoride gas or adding a boron trifluoride complex, and reacting to obtain a lithium tetrafluoroborate liquid; the preparation process is simple and efficient, the adopted raw materials are very easy to obtain, meanwhile, the fluorination reaction and the lithium tetrafluoroborate synthesis reaction are sequentially carried out in an organic solvent environment, the whole reaction process is safe, stable and reliable, and the preparation method is very suitable for large-scale batch popularization and application; and the lithium tetrafluoroborate liquid with a low acid value can be directly obtained and can be directly applied as an electrolyte additive.

Description

Technical Field

[0001] The invention belongs to the field of lithium ion battery electrolyte, and specifically relates to a method for preparing liquid lithium tetrafluoroborate. Background Art

[0002] Lithium tetrafluoroborate LiBF4 is widely used as an electrolyte additive in the electrolyte of lithium-ion batteries. It can provide ion conductivity, promote ion transport within the battery, and improve battery performance and cycle life.

[0003] The invention patent application with publication number CN106335907A discloses a synthesis technology of lithium tetrafluoroborate, in which sodium tetrafluoroborate (or potassium or ammonia) and lithium fluoride are reacted in an organic solvent under the catalysis of a catalyst, the produced sodium fluoride (or potassium or ammonia) is filtered out with a filter press, and the filtrate is evaporated and dried to obtain the product lithium tetrafluoroborate.

[0004] The invention patent application with publication number CN116730352A discloses a synthesis method and electrolyte of lithium tetrafluoroborate, which is synthesized by a solvent method. Specifically, any available halogenated lithium and boron trichloride are first reacted to obtain an intermediate product, which is then uniformly fluorinated to obtain lithium tetrafluoroborate.

[0005] The current synthesis methods either use expensive raw materials or require harsh reaction conditions and high costs.

[0006] The applicant hopes to seek a more efficient preparation route to obtain liquid lithium tetrafluoroborate. Summary of the invention

[0007] In view of this, the purpose of the present invention is to provide a method for preparing liquid lithium tetrafluoroborate, the preparation process is simple and efficient, and the raw materials used are very easy to obtain. At the same time, the present invention performs sequential fluorination reaction and lithium tetrafluoroborate synthesis reaction in an organic solvent environment, and the overall reaction process is safe, stable and reliable, which is very suitable for large-scale batch promotion and application; and the present invention can directly obtain lithium tetrafluoroborate liquid with a low acid value, which can be directly used as an electrolyte additive.

[0008] The technical solution adopted by the present invention is as follows: A method for preparing liquid lithium tetrafluoroborate comprises the following steps: anhydrous lithium chloride is fluorinated with anhydrous hydrogen fluoride in an organic solvent to obtain lithium fluoride, and then boron trifluoride gas is introduced or a boron trifluoride complex is added to react and obtain liquid lithium tetrafluoroborate.

[0009] Preferably, the reaction equation for obtaining lithium fluoride by fluorination of anhydrous lithium chloride with anhydrous hydrogen fluoride in an organic solvent is as follows: HF+LiCl=LiF+HCl(g).

[0010] Preferably, the reaction equation for obtaining lithium tetrafluoroborate liquid is as follows: LiF+BF3=LiBF4.

[0011] Preferably, the method comprises the following steps: S10), adding powdered anhydrous lithium chloride to the organic solvent in the reactor, and dissolving by stirring to obtain a lithium chloride solution; S20), adding anhydrous hydrogen fluoride dropwise to the lithium chloride solution, and under stirring, the lithium chloride is fluorinated by the hydrogen fluoride to obtain lithium fluoride; S30), vacuumizing the reactor to remove hydrogen chloride gas; S40), introducing boron trifluoride gas or adding a boron trifluoride complex into the reactor under stirring to react and obtain lithium tetrafluoroborate liquid.

[0012] Preferably, during the reaction to obtain lithium fluoride, the temperature in the reactor is controlled within a range of 15-45° C., and the reaction time is not less than 1.5 hours.

[0013] Preferably, the molar ratio of the anhydrous lithium chloride to the organic solvent is in the range of 1:1-3, more preferably 1:1.05-2; the molar ratio of the anhydrous lithium chloride to the anhydrous hydrogen fluoride is in the range of 1:1-1.08, more preferably 1:1.01-1.06; the molar ratio of the lithium fluoride to boron trifluoride is in the range of 1:1-1.1.

[0014] Preferably, during the reaction to obtain lithium tetrafluoroborate liquid, the temperature in the reactor is controlled within a range of 10-60° C., and the reaction time is not less than 1.5 hours.

[0015] Preferably, the reactor is a polytetrafluoroethylene (PTFE) lined reactor with a stirring device and a jacket.

[0016] Preferably, in the step S20), during the reaction to obtain lithium fluoride, the generated hydrogen chloride gas is transported to an absorption tower for absorption, and the absorption tower comprises a water absorption tower and an alkali absorption tower connected in sequence, wherein the top gas output end of the reactor is connected to the water absorption tower.

[0017] Preferably, in the step S30), the vacuum pump is started to evacuate the reactor, and the operating pressure in the reactor is maintained under negative pressure for 3-12 hours; in the step S40), the speed of introducing boron trifluoride gas is controlled at 0.28-0.4 mol / hour.

[0018] The invention adopts anhydrous lithium chloride to be fluorinated by anhydrous hydrogen fluoride in an organic solvent to obtain lithium fluoride, and then introduces boron trifluoride gas or adds a boron trifluoride complex to react to obtain lithium tetrafluoroborate liquid. The preparation process is simple and efficient, and the raw materials used are very easy to obtain. At the same time, the application performs sequential fluorination reaction and lithium tetrafluoroborate synthesis reaction in an organic solvent environment. The overall reaction process is safe, stable and reliable, and is very suitable for large-scale batch promotion and application. In addition, the application can directly obtain lithium tetrafluoroborate liquid with a low acid value, which can be directly used as an electrolyte additive. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the connection structure of a device for preparing liquid lithium tetrafluoroborate according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0020] See also Figure 1 As shown, this embodiment provides a method for preparing liquid lithium tetrafluoroborate, wherein anhydrous lithium chloride is fluorinated with anhydrous hydrogen fluoride in an organic solvent to obtain lithium fluoride, and the corresponding reaction equation is: HF+LiCl=LiF+HCl(g); then boron trifluoride gas is introduced or a boron trifluoride complex is added to react to obtain lithium tetrafluoroborate liquid, and the corresponding reaction equation is: LiF+BF3=LiBF4.

[0021] Preferably, see Figure 1 As shown, in this embodiment, the reactor adopts a polytetrafluoroethylene (PTFE) lined reactor 100 with a stirring device 110 and a jacket 120, and is connected to an exhaust vacuum pump (not shown), and is respectively provided with an anhydrous hydrogen chloride gas delivery pipeline a1, a boron trifluoride gas delivery pipeline a2, a nitrogen delivery pipeline a3, a solid raw material delivery pipeline a4 (for realizing the feeding and delivery of lithium chloride and / or boron trifluoride complex), and an organic solvent delivery pipeline ( Figure 1 The upper end of the jacket 120 is connected to a cold (hot) medium outlet pipeline a6, and the lower end thereof is connected to a cold (hot) medium inlet pipeline a7; Preferably, in this embodiment, the preparation method of liquid lithium tetrafluoroborate specifically includes the following steps: S10), adding powdered anhydrous lithium chloride to the organic solvent in the reactor (i.e., the reactor 100), and dissolving by stirring to obtain a lithium chloride solution; preferably, in this step S10), the molar ratio of anhydrous lithium chloride to the organic solvent is in the range of 1:1-3, more preferably 1:1.05-2; the organic solvent may be any known carbonate organic solvent, preferably a linear carbonate organic solvent; S20), add anhydrous hydrogen fluoride dropwise to the lithium chloride solution, and under stirring, the lithium chloride is fluorinated by hydrogen fluoride to obtain lithium fluoride; wherein, preferably, in this step S20), the temperature range in the reactor is controlled at 15-45°C, and the reaction time is not less than 1.5 hours, preferably 2-8 hours, and more preferably 2-6 hours; the molar ratio of anhydrous lithium chloride to anhydrous hydrogen fluoride is in the range of 1:1-1.08, and more preferably 1:1.01-1.06; further preferably, in this step S20), , the generated hydrogen chloride gas is transported to the absorption tower for absorption, and the absorption tower includes a water absorption tower 200 and an alkali absorption tower 300 connected in sequence, wherein the hydrogen chloride gas output pipeline a5 at the top of the reactor 100 is connected to the water absorption tower 200, and the hydrogen chloride gas generated after the fluorination reaction in the reactor 100 is removed in time, and more preferably, a water absorption tower circulation pump 210 is provided at the bottom and the top of the water absorption tower 200, and an alkali absorption tower circulation pump 310 is provided at the bottom and the top of the alkali absorption tower 300; S30), the reactor is evacuated to remove the hydrogen chloride gas; preferably, in this step S30), the vacuum pump is started to evacuate the reactor, and the operating pressure in the reactor is maintained under negative pressure conditions for 3-12 hours, preferably at -0.1 MPaG to -0.06 MPaG for 3-12 hours, and more preferably at -0.099 MPaG to -0.089 MPaG for 6-12 hours; S40), introducing boron trifluoride gas or adding a boron trifluoride complex into the reactor under stirring to react and obtain lithium tetrafluoroborate liquid; preferably, in this step S30), the molar ratio of lithium fluoride to boron trifluoride is in the range of 1:1-1.1; the speed of introducing boron trifluoride gas is controlled at 0.28-0.4 mol boron trifluoride / hour; the temperature in the reactor is controlled at 10-60°C, and the reaction time is not less than 1.5 hours, preferably 2-8 hours, and more preferably 3-6 hours.

[0022] In order to enable those skilled in the art to better understand the implementation process of the present invention, based on the above implementation scheme, the present application further proposes the following specific examples: Embodiment 1:

[0023] In a polytetrafluoroethylene (PTFE) lined reactor with a stirring device and a jacket, 200 g (about 2.22 mol) of electronic grade dimethyl carbonate was added, the reactor was stirred, 42.4 g (about 1.0 mol) of anhydrous lithium chloride was added first, and then 20.1 g (about 1.0 mol) of anhydrous hydrogen fluoride was added dropwise, the reaction temperature was maintained at 25°C, and the addition was completed and stirred for 2 hours. The hydrogen chloride gas generated during the reaction was transported to a water absorption tower for absorption; after the reaction was completed, the vacuum pump was started to evacuate the reactor, and the operating pressure in the reactor was maintained at -0.098 MPaG for 10 hours, and the evacuation was completed; 67.9 g of high-purity boron trifluoride gas was introduced within three hours, and the stirring reaction was continued for 3 hours after completion; liquid lithium tetrafluoroborate was obtained; After content detection, the lithium tetrafluoroborate content in the liquid lithium tetrafluoroborate is 31.2%, and the acidity is (calculated as hydrogen fluoride) 35ppm. Embodiment 2:

[0024] In a polytetrafluoroethylene (PTFE) lined reactor with a stirring device and a jacket, 107.0 g (about 1.19 mol) of electronic grade dimethyl carbonate was added, the reactor was stirred, 42.4 g (about 1.0 mol) of anhydrous lithium chloride was added first, and then 21.1 g (about 1.05 mol) of anhydrous hydrogen fluoride was added dropwise, the reaction temperature was maintained at 23°C, and the addition was stirred for 3 hours. The hydrogen chloride gas generated during the reaction was transported to a water absorption tower for absorption; after the reaction was completed, the vacuum pump was started to evacuate the materials in the reactor, and the operating pressure in the reactor was maintained at -0.0985 MPaG for 8 hours, and the evacuation was completed; 161.5 g of solid boron trifluoride dimethyl carbonate complex (including about 42% boron trifluoride content, 67.8 g boron trifluoride, and 93.6 g dimethyl carbonate) was added, and the stirring reaction was continued for 4 hours after completion; liquid lithium tetrafluoroborate was obtained; After content detection, the lithium tetrafluoroborate content in the liquid lithium tetrafluoroborate is 31.4%, and the acidity is (calculated as hydrogen fluoride) 45ppm. Embodiment 3:

[0025] In a polytetrafluoroethylene (PTFE) lined reactor with a stirring device and a jacket, 208 g (about 2.0 mol) of electronic grade ethyl methyl carbonate was added, the reactor was stirred, 42.4 g (about 1.0 mol) of anhydrous lithium chloride was added first, and then 21.1 g (about 1.05 mol) of anhydrous hydrogen fluoride was added dropwise, the reaction temperature was maintained at 28°C, and the addition was completed and stirred for 3 hours. The hydrogen chloride gas generated during the reaction was transported to a water absorption tower for absorption; after the reaction was completed, the vacuum pump was started to evacuate the materials in the reactor, and the operating pressure in the reactor was maintained at -0.099 MPaG for 10 hours, and the evacuation was completed; 67.8 g of boron trifluoride gas was introduced, and the reaction was continued to be stirred for 6 hours after completion; liquid lithium tetrafluoroborate was obtained; After content detection, the lithium tetrafluoroborate content in the liquid lithium tetrafluoroborate is 30.8%, and the acidity is (calculated as hydrogen fluoride) 32ppm. Embodiment 4:

[0026] In a polytetrafluoroethylene (PTFE) lined reactor with a stirring device and a jacket, 110 g (about 1.0 mol) of electronic grade ethyl methyl carbonate was added, the reactor was stirred, 42.4 g (about 1.0 mol) of anhydrous lithium chloride was added first, and then 20.6 g (about 1.03 mol) of anhydrous hydrogen fluoride was added dropwise, the reaction temperature was maintained at 36°C, and the addition was stirred for 5 hours. The hydrogen chloride gas generated during the reaction was transported to a water absorption tower for absorption; after the reaction was completed, the vacuum pump was started to evacuate the materials in the reactor, and the operating pressure of the reactor was maintained at -0.0995 MPaG for 10 hours, and the evacuation was completed; 178.5 g of boron trifluoride ethyl carbonate complex (including about 38.0% boron trifluoride content, 67.8 g boron trifluoride, and 110.6 g ethyl methyl carbonate) was slowly added, and the stirring reaction was continued for 5 hours after completion; liquid lithium tetrafluoroborate was obtained.

[0027] After content detection, the lithium tetrafluoroborate content in the liquid lithium tetrafluoroborate is 30.9%, and the acidity is (calculated as hydrogen fluoride) 28ppm.

[0028] It will be apparent to those skilled in the art that the invention is not limited to the details of the exemplary embodiments described above and that the invention can be implemented in other specific forms without departing from the spirit or essential features of the invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations falling within the meaning and scope of the equivalent elements of the claims be included in the invention. Any reference numeral in a claim should not be considered as limiting the claim to which it relates.

[0029] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing liquid lithium tetrafluoroborate, characterized in that: Anhydrous lithium chloride is fluorinated with anhydrous hydrogen fluoride in an organic solvent to obtain lithium fluoride, and then boron trifluoride gas or a boron trifluoride complex is introduced to react to obtain lithium tetrafluoroborate liquid.

2. The method for preparing liquid lithium tetrafluoroborate according to claim 1, characterized in that: The reaction equation for obtaining lithium fluoride by fluorination of anhydrous lithium chloride with anhydrous hydrogen fluoride in an organic solvent is as follows: HF+LiCl=LiF+HCl(g).

3. The method for preparing liquid lithium tetrafluoroborate according to claim 1, characterized in that: The reaction equation for obtaining lithium tetrafluoroborate liquid by the reaction is as follows: LiF+BF3=LiBF4.

4. The method for preparing liquid lithium tetrafluoroborate according to claim 1, characterized in that: The steps are as follows: S10), adding powdered anhydrous lithium chloride to the organic solvent in the reactor, and dissolving by stirring to obtain a lithium chloride solution; S20), adding anhydrous hydrogen fluoride dropwise to the lithium chloride solution, and under stirring, the lithium chloride is fluorinated by the hydrogen fluoride to obtain lithium fluoride; S30), vacuumizing the reactor to remove hydrogen chloride gas; S40), introducing boron trifluoride gas or adding a boron trifluoride complex into the reactor under stirring to react and obtain lithium tetrafluoroborate liquid.

5. The method for preparing liquid lithium tetrafluoroborate according to claim 1, 2, 3 or 4, characterized in that: In the process of obtaining lithium fluoride by reaction, the temperature in the reactor is controlled in the range of 15-45° C., and the reaction time is not less than 1.5 hours.

6. The method for preparing liquid lithium tetrafluoroborate according to claim 1, 2, 3 or 4, characterized in that: The molar ratio of the anhydrous lithium chloride to the organic solvent is in the range of 1:1-3, more preferably 1:1.05-2; the molar ratio of the anhydrous lithium chloride to the anhydrous hydrogen fluoride is in the range of 1:1-1.08, more preferably 1:1.01-1.06; the molar ratio of the lithium fluoride to boron trifluoride is in the range of 1:1-1.

1.

7. The method for preparing liquid lithium tetrafluoroborate according to claim 1, 2, 3 or 4, characterized in that: In the process of obtaining lithium tetrafluoroborate liquid by reaction, the temperature in the reactor is controlled in the range of 10-60° C., and the reaction time is not less than 1.5 hours.

8. The method for preparing liquid lithium tetrafluoroborate according to claim 4, characterized in that: The reactor is a polytetrafluoroethylene (PTFE) lined reactor with a stirring device and a jacket.

9. The method for preparing liquid lithium tetrafluoroborate according to claim 4, characterized in that: In the step S20), during the reaction to obtain lithium fluoride, the generated hydrogen chloride gas is transported to an absorption tower for absorption, and the absorption tower includes a water absorption tower and an alkali absorption tower connected in sequence, wherein the top gas output end of the reactor is connected to the water absorption tower.

10. The method for preparing liquid lithium tetrafluoroborate according to claim 4, characterized in that: In the step S30), the vacuum pump is started to evacuate the reactor, and the operating pressure in the reactor is maintained under negative pressure for 3-12 hours; in the step S40), the speed of introducing boron trifluoride gas is controlled at 0.28-0.4 mol / hour.

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