Preparation method and application of lithium trifluoroborate containing unsaturated bonds

Abstract

The invention relates to the technical field of lithium ion battery material additives, and discloses a preparation method and application of a lithium trifluoroborate salt containing unsaturated bonds, the preparation method comprises the following steps: placing a poor solvent and a boron trifluoride anisole complex in a reactor under a low temperature condition, and uniformly stirring; adding an organic lithium salt containing unsaturated bonds into the reactor, and reacting under a low-temperature condition; then reacting at normal temperature to obtain a reaction solution after the reaction is completed; carrying out solid-liquid separation on the reaction liquid to obtain a lithium trifluoroborate crude product containing unsaturated bonds and filtrate; and re-dissolving and recrystallizing the lithium trifluoroborate crude product containing the unsaturated bond to obtain a finished product. Anisole is used as a reaction solvent, so that the product yield is increased; the usage amount of the anisole is small, and the anisole can be recycled after being properly recycled, so that the production cost is reduced; the method has the characteristics of simplicity in operation, high product yield, high product quality and low cost, is basically free of three wastes, is environment-friendly and is suitable for industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of lithium ion battery material additives, and in particular to a preparation method and application of lithium trifluoroborate salt containing unsaturated bonds. Background Art

[0002] Lithium-ion batteries have the advantages of high operating voltage, high specific energy density, long cycle life and low environmental pollution, and have been widely used in various electronic consumer products and power battery fields. In high energy density battery systems, electrolytes are prone to a series of problems such as poor wettability, lithium precipitation, reduced cycle life and reduced rate performance. Electrolyte solutes are an indispensable component of electrolytes, and their performance directly affects the overall performance of the battery.

[0003] Lithium difluorooxalatoborate (LiODFB) and vinylene carbonate (VC) are electrolyte additives that improve the performance and safety of lithium-ion batteries through different mechanisms. LiODFB mainly improves the cycle performance and conductivity of the battery by forming an SEI film and acting as a conductive salt; while VC mainly protects the electrode material and improves the charge and discharge efficiency and cycle life of the battery by forming a stable SEI film. However, both LiODFB and VC have problems such as high production costs and complex preparation processes.

[0004] In the face of the above technical problems, researchers have actively developed various additives. For example, in the Chinese invention patent "A method for preparing trifluoroboric acid organic lithium salt containing unsaturated bonds at low temperature" with publication number CN116715691A, acetonitrile is used as a reaction solvent to synthesize trifluoroboric acid organic lithium salt containing unsaturated bonds. However, this process still has problems such as low product yield using good solvents, large amount of solvents that cannot be recycled, and high production costs. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a preparation method and application of lithium trifluoroborate salt containing unsaturated bonds.

[0006] To achieve the above object, the present invention is implemented according to the following technical solutions:

[0007] A method for preparing lithium trifluoroborate salt containing an unsaturated bond comprises the following steps:

[0008] S1, placing a poor solvent and a boron trifluoride anisole complex in a reactor under low temperature conditions, and stirring them uniformly;

[0009] S2, adding an organic lithium salt containing an unsaturated bond into the reactor in step S1, and reacting under low temperature conditions;

[0010] S3, then reacting at room temperature to obtain a reaction solution after the reaction is completed; performing solid-liquid separation on the reaction solution to obtain a crude product of lithium trifluoroborate salt containing an unsaturated bond and a filtrate;

[0011] S4, the crude product of lithium trifluoroborate salt containing unsaturated bonds is redissolved and recrystallized to obtain a finished product, namely the lithium trifluoroborate salt containing unsaturated bonds.

[0012] Preferably, the structural formula of the organic lithium salt containing an unsaturated bond is as shown in formula (1);

[0013]

[0014] The structural formula of the lithium trifluoroborate salt containing an unsaturated bond is shown in formula (2):

[0015]

[0016] In the above formula (1) and formula (2), R is One of them.

[0017] Preferably, in step S1, the amount of the poor solvent is 8 to 10 times the mass of the organic lithium salt containing an unsaturated bond; the poor solvent is a poor solvent for lithium trifluoroborate salt containing an unsaturated bond.

[0018] Preferably, the poor solvent is one of anisole, dichloromethane and methyl tert-butyl ether.

[0019] More preferably, the poor solvent is anisole.

[0020] In the preparation method of the present invention, it is possible to react as long as a poor solvent of trifluoroborate lithium salt containing unsaturated bonds is selected; but anisole is the best poor solvent. When the poor solvent selects dichloromethane, although dichloromethane is easier to remove in the later stage during the production process, after all, there is anisole produced by the boron trifluoride anisole complex in addition to dichloromethane after the reaction, and there are two kinds of solvents, and post-processing becomes more cumbersome, and it is necessary to consider removing two kinds of residual solvents. When anisole is selected, the type of solvent in the reaction solution can be made single, and it is convenient to uniformly recycle anisole in the later stage, without further separation of two different solvents.

[0021] Preferably, in step S1, the content of boron trifluoride in the boron trifluoride anisole complex is 28.5 wt %.

[0022] The content of boron trifluoride in the boron trifluoride anisole complex of the present invention does not affect the reaction; however, the solid-liquid reaction preparation process is smoother than the solid-solid reaction, so the liquid boron trifluoride anisole complex is preferably selected.

[0023] Preferably, in step S2, the amount (molar amount) of the organic lithium salt containing an unsaturated bond added is 0.90 to 0.98 times the molar amount of the boron trifluoride anisole complex.

[0024] Specifically, the molar amount of the boron trifluoride anisole complex is based on the molar amount of boron trifluoride contained therein.

[0025] The anisole used in the present invention is a poor solvent for the prepared product, lithium trifluoroborate salt containing an unsaturated bond.

[0026] Preferably, steps S1, S2, S3 and S4 are all performed under inert gas protection or nitrogen protection.

[0027] Preferably, the reaction temperature in steps S1 and S2 is -20 to -10°C.

[0028] The reason why the reaction temperature of steps S1 and S2 of the present invention is controlled at a low temperature is that the reaction starts after the addition of lithium salt, and the reaction is an exothermic reaction. During the reaction, the temperature will rise to about 38-40°C. In this temperature range, many by-products will be generated, which will affect the yield. Therefore, the present invention first reacts at a low temperature, lowers the temperature, and reacts at room temperature after the reaction is exothermic.

[0029] More preferably, the reaction temperatures in steps S1 and S2 are both -20 to -15°C.

[0030] Preferably, in step S2, the time for adding the organic lithium salt containing an unsaturated bond is 10 to 20 minutes; after the addition is completed, the stirring reaction is continued at a low temperature for 20 to 30 minutes.

[0031] Preferably, in step S3, the reaction temperature at room temperature is 10-20° C., and the reaction time is 4-6 hours.

[0032] More preferably, in step S3, the reaction temperature for the reaction at room temperature is 15-20°C.

[0033] Preferably, the filtrate obtained in step S3 can be recycled.

[0034] Specifically, the filtrate can be collected and recycled as anisole.

[0035] Preferably, in step S4, the solvent used in the process of re-dissolution and recrystallization is at least one of dimethyl carbonate, diethyl carbonate, acetonitrile, ethyl acetate, and ethylene glycol dimethyl ether; the amount of the solvent used is 5 to 10 times the quality of the crude lithium trifluoroborate salt containing unsaturated bonds.

[0036] The lithium trifluoroborate salt containing unsaturated bonds prepared by the present invention can be used as an additive in lithium ion batteries. It is mainly used in the electrolyte of lithium ion batteries and can be used as a new type of lithium ion battery additive to improve the cycle stability and life of lithium ion batteries.

[0037] In the Chinese invention patent with publication number CN116715691A, the amount of solvent used is 12-14 times that of the raw material lithium salt, while the amount of solvent used in the present invention is 8-10 times that of the raw material lithium salt, and the amount of solvent used is small; and the solvent of the present invention can be recycled, and the production cost is lower.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The invention uses anisole as a reaction solvent, thereby improving the product yield; the amount of anisole used is small, and the anisole can be recycled after being recovered, thereby reducing the production cost; the invention has the characteristics of simple operation, high product yield, high quality and low cost, basically no three wastes are generated, the invention is environmentally friendly and suitable for industrial production. DETAILED DESCRIPTION

[0040] A method for preparing lithium trifluoroborate salt containing an unsaturated bond comprises the following steps:

[0041] (1) Weigh a poor solvent of lithium trifluoroborate salt containing an unsaturated bond and a boron trifluoride anisole complex into a reactor and stir them uniformly at -20 to -10°C.

[0042] (2) adding an organic lithium salt containing an unsaturated bond under magnetic stirring, and continuing to stir and react at -20 to -10°C for 20 to 30 minutes after the addition is completed.

[0043] (3) The reactor was then moved to a temperature of 15 to 20° C. and reacted for 4 to 6 hours. A large amount of white solid precipitated and was filtered using a positive pressure filter. The filter cake was purged with nitrogen for 2 to 4 hours and then collected to obtain a crude product of lithium trifluoroborate salt containing an unsaturated bond.

[0044] (4) The crude product of lithium trifluoroborate salt containing unsaturated bonds is redissolved and recrystallized to obtain the finished product of lithium trifluoroborate salt containing unsaturated bonds.

[0045] The present invention is further described below with reference to specific embodiments. The illustrative embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0046] Example 1

[0047] The preparation method of the lithium trifluoroborate salt containing an unsaturated bond in this embodiment comprises the following steps (all the following steps are carried out under nitrogen protection):

[0048] (1) Weigh 210 g of anisole and 82.3 g of boron trifluoride anisole (wherein the content of boron trifluoride is 28.5 wt %), add them into a round-bottom flask, and stir evenly at -20°C.

[0049] (2) Add 26 g of lithium acrylate to the solution under stirring conditions for 10 min. After the addition is completed, continue to stir and react at -20°C for 30 min.

[0050] (3) The round-bottom flask was removed from the freezing bath and moved to room temperature (20°C) to continue the reaction for 5 h.

[0051] (4) Filter the reaction solution with a positive pressure filter to obtain a filtrate and a solid; after the solid is purged with nitrogen for 2 hours, 46.7 g of a crude product of lithium trifluoroborate containing an unsaturated bond is obtained.

[0052] (5) The crude lithium trifluoroborate salt containing an unsaturated bond was redissolved with 374 g of dimethyl carbonate and filtered, and the filtrate was concentrated and crystallized to obtain 45.9 g of the finished product.

[0053] The finished lithium salt obtained in this embodiment is lithium trifluoroborate acrylate, and its yield is 95% and its purity is 98%.

[0054] Example 2

[0055] The preparation method of the lithium trifluoroborate salt containing an unsaturated bond in this embodiment comprises the following steps:

[0056] (1) Weigh 270 g of anisole and 80.5 g of boron trifluoride anisole (wherein the content of boron trifluoride is 28.5 wt %), add them into a round-bottom flask, and stir evenly at -20°C.

[0057] (2) 30 g of lithium methacrylate was added to the solution under stirring for 15 min. After the addition was completed, the mixture was stirred and reacted at -20°C for 30 min.

[0058] (3) The round-bottom flask was removed from the freezing bath and moved to room temperature (20°C) to continue the reaction for 6 h.

[0059] (4) Filter the reaction solution with a positive pressure filter to obtain a filtrate and a solid; the filtrate is collected and recycled, and the solid is purged with nitrogen for 2 hours to obtain 50.6 g of crude lithium trifluoroborate salt containing an unsaturated bond.

[0060] (5) The crude lithium trifluoroborate salt containing an unsaturated bond was redissolved with 405 g of dimethyl carbonate and filtered, and the filtrate was concentrated and crystallized to obtain 49.8 g of the finished product.

[0061] The finished lithium salt obtained in this embodiment is lithium methacrylate trifluoroborate, and its yield is 96% and its purity is 98%.

[0062] Example 3

[0063] The preparation method of the lithium trifluoroborate salt containing an unsaturated bond in this embodiment comprises the following steps:

[0064] (1) Weigh 205 g of the filtrate obtained by filtering the reaction solution in step (4) of Example 2 and 55.9 g of boron trifluoride anisole (wherein the content of boron trifluoride is 28.5 wt %), add them into a round-bottom flask, and stir evenly at -20°C.

[0065] (2) 24 g of lithium tiglate was added to the solution under stirring for 10 min. After the addition was completed, the solution was stirred at -20°C for 30 min.

[0066] (3) Take the round-bottom flask out of the freezing bath and move it to room temperature (20°C) for reaction for 5 h.

[0067] (4) Filter the reaction solution with a positive pressure filter to obtain a filtrate and a solid; after the solid is purged with nitrogen for 2 hours, 38.5 g of a crude solid lithium trifluoroborate salt containing an unsaturated bond is obtained.

[0068] (5) The crude product of lithium trifluoroborate salt containing unsaturated bonds was redissolved in 267 g of ethyl acetate and filtered. The filtrate was concentrated and crystallized to obtain 37.2 g of the finished product.

[0069] The finished lithium salt obtained in this embodiment is lithium trifluoroborate tigaic acid, and its yield is 95% and its purity is 97%.

[0070] Example 4

[0071] The preparation method of the lithium trifluoroborate salt containing an unsaturated bond in this embodiment comprises the following steps:

[0072] (1) Weigh 294 g of dichloromethane and 83.8 g of boron trifluoride anisole (wherein the content of boron trifluoride is 28.5 wt %), add them into a round-bottom flask, and stir them evenly at -20°C.

[0073] (2) 36 g of lithium dimethacrylate was added to the solution under stirring for 20 min. After the addition was completed, the solution was stirred at -20°C for 30 min.

[0074] (3) Take the round-bottom flask out of the freezing bath and move it to room temperature (20°C) for reaction for 6 h.

[0075] (4) Filter the reaction solution with a positive pressure filter to obtain a filtrate and a solid; after the solid is purged with nitrogen for 2 hours, 57.3 g of a crude product of lithium trifluoroborate containing an unsaturated bond is obtained.

[0076] (5) The crude product of lithium trifluoroborate salt containing an unsaturated bond was redissolved in 200 g of acetonitrile and 143 g of ethyl acetate and filtered. The filtrate was concentrated and crystallized to obtain 56.4 g of the finished product.

[0077] The finished lithium salt obtained in this embodiment is lithium trifluoroborate dimethacrylate, and its yield is 96% and its purity is 97%.

[0078] Example 5

[0079] This example uses the lithium trifluoroborate acrylate obtained in Example 1 and adds it to an electrolyte with LiPF6 as a solute lithium salt and DMC and DEC as solvents. The lithium trifluoroborate acrylate is used as an additive to improve the cycle stability and service life of the lithium battery.

[0080] Comparative Example 1

[0081] A method for preparing lithium trifluoroborate salt containing an unsaturated bond comprises the following steps:

[0082] (1) Weigh 210 g of acetonitrile and 96.8 g of boron trifluoride acetonitrile (wherein the content of boron trifluoride is 19 wt%) into a round-bottom flask and stir evenly at -20°C.

[0083] (2) Add 21 g of lithium acrylate to the solution under stirring conditions for 10 min. After the addition is completed, stir and react at -20°C for 30 min.

[0084] (3) The round-bottom flask was removed from the freezing bath and moved to room temperature (20°C) to continue the reaction for 5 h.

[0085] (4) The reaction solution was filtered through a positive pressure filter and purged with nitrogen for 2 h to obtain 35.5 g of a crude product.

[0086] (5) The crude product was redissolved in 374 g of dimethyl carbonate and filtered, and the filtrate was concentrated and crystallized to obtain 33.2 g of the finished product.

[0087] The finished product obtained in this comparative example is lithium acrylate trifluoroborate, with a yield of 85% and a purity of 98%.

[0088] The technical solution of the present invention is not limited to the above-mentioned specific embodiments. All technical variations made according to the technical solution of the present invention fall within the protection scope of the present invention.

Claims

1. A method for preparing a lithium trifluoroborate salt containing an unsaturated bond, characterized in that: The following steps are involved: S1, placing a poor solvent and a boron trifluoride anisole complex in a reactor under low temperature conditions, and stirring them uniformly; S2, adding an organic lithium salt containing an unsaturated bond into the reactor in step S1, and reacting under low temperature conditions; S3, then reacting at room temperature to obtain a reaction solution after the reaction is completed; performing solid-liquid separation on the reaction solution to obtain a crude product of lithium trifluoroborate salt containing an unsaturated bond and a filtrate; S4, the crude product of lithium trifluoroborate salt containing unsaturated bonds is redissolved and recrystallized to obtain a finished product, namely the lithium trifluoroborate salt containing unsaturated bonds.

2. The method for preparing a lithium trifluoroborate salt containing an unsaturated bond according to claim 1, characterized in that: The structural formula of the organic lithium salt containing an unsaturated bond is shown in formula (1); The structural formula of the lithium trifluoroborate salt containing an unsaturated bond is shown in formula (2): In the above formula (1) and formula (2), R is One of them.

3. The method for preparing a lithium trifluoroborate salt containing an unsaturated bond according to claim 1, characterized in that: In the step S1, the amount of the poor solvent is 8 to 10 times the mass of the organic lithium salt containing unsaturated bonds; the poor solvent is a poor solvent for lithium trifluoroborate salt containing unsaturated bonds.

4. The method for preparing a lithium trifluoroborate salt containing an unsaturated bond according to claim 3, characterized in that: The poor solvent is one of anisole, dichloromethane and methyl tert-butyl ether.

5. The method for preparing a lithium trifluoroborate salt containing an unsaturated bond according to claim 1, characterized in that: In the step S2, the amount of the organic lithium salt containing an unsaturated bond added is 0.90 to 0.98 times the molar amount of the boron trifluoride anisole complex, the feeding time of the organic lithium salt containing an unsaturated bond is 10 to 20 minutes, and after the feeding is completed, the stirring reaction is continued at a low temperature for 20 to 30 minutes.

6. The method for preparing a lithium trifluoroborate salt containing an unsaturated bond according to claim 1, characterized in that: The steps S1, S2, S3 and S4 are all carried out under the condition of inert gas protection or nitrogen protection.

7. The method for preparing a lithium trifluoroborate salt containing an unsaturated bond according to claim 1, characterized in that: The reaction temperatures in steps S1 and S2 are both -20 to -10°C.

8. The method for preparing a lithium trifluoroborate salt containing an unsaturated bond according to claim 1, characterized in that: In the step S3, the reaction temperature is 10-20° C. and the reaction time is 4-6 hours at room temperature; the filtrate obtained in the step S3 can be recycled.

9. The method for preparing a lithium trifluoroborate salt containing an unsaturated bond according to claim 1, characterized in that: In step S4, the solvent used in the process of re-dissolving and recrystallizing is at least one of dimethyl carbonate, diethyl carbonate, acetonitrile, ethyl acetate, and ethylene glycol dimethyl ether; the amount of the solvent used is 5 to 10 times the quality of the crude lithium trifluoroborate salt containing unsaturated bonds.

10. Use of lithium trifluoroborate salt containing unsaturated bonds prepared by the preparation method according to any one of claims 1 to 9 in lithium ion batteries.

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