Method for preparing lithium difluoro (oxalato) borate by one-pot method

Abstract

The invention provides a one-pot method for preparing lithium difluoro (oxalato) borate, which comprises the following steps: (1) mixing lithium oxalate, oxalate, a boron trifluoride complex and an organic solvent to obtain a mixture; (2) carrying out a first heating reaction and a second heating reaction on the obtained mixture to obtain a reaction solution; and (3) carrying out post-treatment on the reaction liquid to obtain the lithium difluoro (oxalato) borate. Compared with the prior art, the method provided by the invention is a one-step reaction, avoids the use of reagents such as hydrofluoric acid, anhydrous hydrogen fluoride and gaseous boron trifluoride, has extremely high reaction selectivity and yield, not only can reduce reaction steps and is beneficial to industrial production, but also can improve the purity of the finally obtained lithium difluoro (oxalato) borate.

Description

Technical Field

[0001] The invention belongs to the technical field of electrolyte materials and relates to a method for preparing lithium difluorooxalatoborate, in particular to a method for preparing lithium difluorooxalatoborate by a one-pot process. Background Art

[0002] Lithium difluorooxalatoborate (LiODFB) is a lithium salt with the molecular formula C2BF2LiO4. It appears as a white powder or crystal. It is highly soluble in water and can be dissolved in carbonate solvents, ether compounds, and organic solvents such as γ-butyrolactone.

[0003] LiODFB combines the advantages of lithium tetrafluoroborate (LiBF4) and lithium bis(oxalatoborate) (LiBOB) in terms of structure and performance. It has the advantages of good thermal stability, insensitivity to moisture, easy film formation and low flatulence. It has high solubility in carbonate solvents and can significantly improve the cycle stability and electrochemical stability of the battery. Therefore, when LiODFB is used as a film-forming additive in lithium battery electrolyte, it can form a good solid electrolyte interface film (SEI film) to improve the cycle performance and rate performance of lithium batteries under wide temperature range conditions; when LiODFB is used as a conductive salt in electrolyte, it can replace lithium hexafluorophosphate to expand the battery operating temperature limit and improve the conductivity of the electrolyte.

[0004] CN109836444A discloses a method for preparing lithium difluorooxalate borate, comprising: (1) reacting a boron-containing substance and lithium oxalate in a polar aprotic solvent to obtain a mixture containing lithium difluorooxalate borate and lithium tetrafluoroborate; (2) reacting a boron-containing substance and potassium oxalate in a polar aprotic solvent to obtain a mixture containing potassium difluorooxalate borate; (3) adding the mixture obtained in step (1) dropwise to the mixture obtained in step (2), reacting to obtain a mixture containing lithium difluorooxalate borate and potassium tetrafluoroborate; (4) filtering the mixture obtained in step (3), concentrating the filtrate, adding an appropriate amount of solvent to the filtrate, stirring and crystallizing; (5) after the crystallization is completed, filtering, vacuum drying the filter cake, and obtaining lithium difluorooxalate borate. However, this method has the disadvantages of many reaction by-products, difficulty in refining and purifying the product, and low yield.

[0005] CN111808128A discloses a method for preparing lithium difluorooxalatoborate, comprising: (1) mixing a lithium source, a fluorine boron source, an oxalic acid compound and an organic solvent to obtain a mixed material; (2) subjecting the mixed material of step (1) to microwave treatment to obtain a microwave reaction product; (3) purifying the microwave reaction product of step (2) to obtain lithium difluorooxalatoborate. This method also has the disadvantages of having many reaction by-products, difficulty in refining and purifying the product and low yield.

[0006] Therefore, there is an urgent need to solve the technical problems of the complicated preparation process of lithium difluorooxalatoborate and the large number of reaction by-products in the art. Summary of the invention

[0007] In view of the shortcomings of the prior art, the object of the present invention is to provide a one-pot method for preparing lithium difluorooxalatoborate, which can avoid the use of reagents such as hydrofluoric acid, anhydrous hydrogen fluoride and gaseous boron trifluoride, has extremely high reaction selectivity and yield, can not only reduce the reaction steps, which is conducive to industrial production, but also can improve the purity of the finally obtained lithium difluorooxalatoborate.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] The present invention provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0010] (1) mixing lithium oxalate, oxalate, a boron trifluoride complex and an organic solvent to obtain a mixture;

[0011] (2) subjecting the obtained mixture to a first temperature-raising reaction and a second temperature-raising reaction to obtain a reaction liquid;

[0012] (3) The reaction solution is post-treated to obtain the lithium difluorooxalatoborate.

[0013] The method provided by the present invention uses an organic solvent as a reaction medium, reacts lithium oxalate, oxalate and a boron trifluoride complex to obtain a reaction solution, and then performs conventional post-treatment to obtain high-purity lithium difluorooxalate borate. Compared with the prior art, the method provided by the present invention is a one-step reaction, avoids the use of reagents such as hydrofluoric acid, anhydrous hydrogen fluoride and gaseous boron trifluoride, has extremely high reaction selectivity and yield, can not only reduce the reaction steps, is conducive to industrial production, but also can improve the purity of the finally obtained lithium difluorooxalate borate.

[0014] Preferably, the molar ratio of lithium oxalate to boron trifluoride complex is 0.25:1 to 0.3:1, for example, 0.25:1, 0.26:1, 0.27:1, 0.28:1, 0.29:1 or 0.3:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 0.26:1 to 0.27:1.

[0015] Preferably, the molar ratio of the oxalate to the boron trifluoride complex is 0.25:1 to 0.3:1, for example, 0.25:1, 0.26:1, 0.27:1, 0.28:1, 0.29:1 or 0.3:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 0.25:1 to 0.26:1.

[0016] Preferably, the molar ratio of the organic solvent to the boron trifluoride complex is 3.1:1 to 3.2:1, for example, 3.1:1, 3.12:1, 3.15:1, 3.16:1, 3.18:1 or 3.2:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the temperature of the first temperature rising reaction is 50°C to 75°C, for example, it can be 50°C, 55°C, 60°C, 65°C, 70°C or 75°C, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 65°C to 70°C.

[0018] Preferably, the insulation time of the first temperature rising reaction is 2h to 6h, for example, 2h, 3h, 4h, 5h or 6h, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable, preferably 3h to 4h.

[0019] Preferably, the temperature of the second temperature-raising reaction is 80°C to 130°C, for example, it can be 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, 120°C or 130°C, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable, preferably 85°C to 90°C.

[0020] Preferably, the insulation time of the second temperature rising reaction is 4h to 9h, for example, it can be 4h, 5h, 6h, 7h, 8h or 9h, but is not limited to the listed values, and the remaining unlisted values ​​within the numerical range are also applicable, preferably 6h to 7h.

[0021] Preferably, the oxalate comprises any one of potassium oxalate, sodium oxalate or cesium oxalate or a combination of at least two thereof, typical but non-limiting combinations include a combination of potassium oxalate and sodium oxalate, a combination of sodium oxalate and cesium oxalate, a combination of potassium oxalate and cesium oxalate, or a combination of potassium oxalate, sodium oxalate and cesium oxalate, preferably sodium oxalate and / or potassium oxalate.

[0022] Preferably, the boron trifluoride complex comprises any one of boron trifluoride ethyl ether, boron trifluoride acetonitrile, boron trifluoride dimethyl carbonate, boron trifluoride methanol or boron trifluoride glycol dimethyl ether, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of boron trifluoride ethyl ether and boron trifluoride acetonitrile, a combination of boron trifluoride acetonitrile and boron trifluoride dimethyl carbonate, a combination of boron trifluoride methanol and boron trifluoride glycol dimethyl ether, a combination of boron trifluoride ethyl ether, boron trifluoride acetonitrile and boron trifluoride methanol, or a combination of boron trifluoride ethyl ether, boron trifluoride acetonitrile, boron trifluoride dimethyl carbonate, boron trifluoride methanol and boron trifluoride glycol dimethyl ether, preferably boron trifluoride dimethyl carbonate and / or boron trifluoride glycol dimethyl ether.

[0023] Preferably, the organic solvent comprises any one of acetonitrile, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether or methanol, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of acetonitrile and dimethyl carbonate, a combination of dimethyl carbonate and diethyl carbonate, a combination of ethyl methyl carbonate and ethylene glycol dimethyl ether, a combination of ethylene glycol dimethyl ether and methanol, a combination of acetonitrile, dimethyl carbonate and diethyl carbonate, a combination of diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether and methanol, or a combination of acetonitrile, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether and methanol, preferably dimethyl carbonate and / or ethylene glycol dimethyl ether.

[0024] As a preferred technical solution of the method provided by the present invention, the method comprises the following steps:

[0025] (1) firstly uniformly mixing a boron trifluoride complex and an organic solvent, and then adding lithium oxalate and oxalate and uniformly mixing them to obtain a mixture;

[0026] The molar ratio of lithium oxalate to boron trifluoride complex is 0.25:1 to 0.3:1;

[0027] The molar ratio of the oxalate to the boron trifluoride complex is 0.25:1 to 0.3:1;

[0028] The molar ratio of the organic solvent to the boron trifluoride complex is 3.1:1 to 3.2:1;

[0029] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0030] The temperature of the first temperature-raising reaction is 65° C. to 70° C., and the insulation time is 3 h to 4 h;

[0031] The temperature of the second temperature-raising reaction is 85° C. to 90° C., and the insulation time is 6 h to 7 h;

[0032] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is subjected to reduced pressure rotary evaporation and vacuum filtration to obtain a white solid; the white solid is vacuum dried to obtain the lithium difluorooxalate borate.

[0033] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The method provided by the present invention uses an organic solvent as a reaction medium, reacts lithium oxalate, oxalate and a boron trifluoride complex to obtain a reaction solution, and then performs conventional post-treatment to obtain high-purity lithium difluorooxalate borate. Compared with the prior art, the method provided by the present invention is a one-step reaction, avoids the use of reagents such as hydrofluoric acid, anhydrous hydrogen fluoride and gaseous boron trifluoride, has extremely high reaction selectivity and yield, can not only reduce the reaction steps, is conducive to industrial production, but also can improve the purity of the finally obtained lithium difluorooxalate borate. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0037] Example 1

[0038] This embodiment provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0039] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 575.04 g (6.383 mol) of an organic solvent (dimethyl carbonate) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 67 g (0.5 mol) of oxalate (sodium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0040] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.192:1.

[0041] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0042] The temperature of the first temperature-raising reaction was 65°C and the holding time was 3h; the temperature of the second temperature-raising reaction was 90°C and the holding time was 6h;

[0043] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is concentrated under reduced pressure at a vacuum degree of 30 mbar and a temperature of 60° C. until the solution remains at 20%, and a white solid is obtained by filtration; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0044] Example 2

[0045] This embodiment provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0046] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 677.47 g (6.381 mol) of an organic solvent (ethylene glycol dimethyl ether) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 67 g (0.5 mol) of oxalate (sodium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0047] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.19:1.

[0048] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0049] The temperature of the first temperature-raising reaction was 65°C and the holding time was 3h; the temperature of the second temperature-raising reaction was 85°C and the holding time was 9h;

[0050] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is concentrated under reduced pressure at a vacuum degree of 30 mbar and a temperature of 60° C. until the solution remains at 20%, and a white solid is obtained by filtration; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0051] Example 3

[0052] This embodiment provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0053] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 677.47 g (6.381 mol) of an organic solvent (ethylene glycol dimethyl ether) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 92.115 g (0.5 mol) of oxalate (potassium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0054] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.19:1.

[0055] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0056] The temperature of the first temperature-raising reaction is 65°C and the holding time is 3h; the temperature of the second temperature-raising reaction is 90°C and the holding time is 7h;

[0057] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is concentrated under reduced pressure at a vacuum degree of 30 mbar and a temperature of 60° C. until the solution remains at 20%, and a white solid is obtained by filtration; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0058] Example 4

[0059] This embodiment provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0060] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 677.47 g (6.381 mol) of an organic solvent (ethylene glycol dimethyl ether) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 92.115 g (0.5 mol) of oxalate (potassium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0061] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.19:1.

[0062] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0063] The temperature of the first temperature-raising reaction was 65°C and the holding time was 3h; the temperature of the second temperature-raising reaction was 85°C and the holding time was 9h;

[0064] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is concentrated under reduced pressure at a vacuum degree of 30 mbar and a temperature of 60° C. until the solution remains at 20%, and a white solid is obtained by filtration; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0065] Example 5

[0066] This embodiment provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0067] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 575.04 g (6.383 mol) of an organic solvent (dimethyl carbonate) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 67 g (0.5 mol) of oxalate (sodium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0068] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.192:1.

[0069] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0070] The temperature of the first temperature-raising reaction was 70°C and the holding time was 4 hours; the temperature of the second temperature-raising reaction was 85°C and the holding time was 7 hours;

[0071] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is concentrated under reduced pressure at a vacuum degree of 30 mbar and a temperature of 60° C. until the solution remains at 20%, and a white solid is obtained by filtration; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0072] Example 6

[0073] This embodiment provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0074] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 575.04 g (6.383 mol) of an organic solvent (dimethyl carbonate) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 67 g (0.5 mol) of oxalate (sodium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0075] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.192:1.

[0076] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0077] The temperature of the first temperature-raising reaction is 60°C and the holding time is 5h; the temperature of the second temperature-raising reaction is 95°C and the holding time is 8h;

[0078] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is subjected to reduced pressure rotary evaporation and vacuum filtration to obtain a white solid; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0079] Example 7

[0080] This example provides a one-pot method for preparing lithium difluorooxalatoborate, which is the same as Example 1 except that the mass of lithium oxalate is 61.146 g (0.6 mol).

[0081] In the method provided in this embodiment, the molar ratio of lithium oxalate to boron trifluoride complex is 0.3:1.

[0082] Example 8

[0083] This example provides a one-pot method for preparing lithium difluorooxalatoborate, which is the same as Example 1 except that the mass of lithium oxalate is 50.95 g (0.5 mol).

[0084] In the method provided in this embodiment, the molar ratio of lithium oxalate to boron trifluoride complex is 0.25:1.

[0085] Example 9

[0086] This example provides a one-pot method for preparing lithium difluorooxalatoborate, which is the same as Example 1 except that the mass of sodium oxalate is 80.4 g (0.6 mol).

[0087] In the method provided in this embodiment, the molar ratio of sodium oxalate to boron trifluoride complex is 0.3:1.

[0088] Example 10

[0089] This example provides a one-pot method for preparing lithium difluorooxalatoborate, which is the same as Example 1 except that the mass of sodium oxalate is 70.68 g (0.52 mol).

[0090] In the method provided in this embodiment, the molar ratio of sodium oxalate to boron trifluoride complex is 0.26:1.

[0091] Embodiment 11

[0092] This embodiment provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0093] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 575.04 g (6.383 mol) of an organic solvent (dimethyl carbonate) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 67 g (0.5 mol) of oxalate (sodium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0094] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.192:1.

[0095] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0096] The temperature of the first temperature-raising reaction is 50°C and the insulation time is 6 hours; the temperature of the second temperature-raising reaction is 80°C and the insulation time is 9 hours;

[0097] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is subjected to reduced pressure rotary evaporation and vacuum filtration to obtain a white solid; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0098] Example 12

[0099] This embodiment provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0100] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 575.04 g (6.383 mol) of an organic solvent (dimethyl carbonate) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 67 g (0.5 mol) of oxalate (sodium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0101] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.192:1.

[0102] (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0103] The temperature of the first temperature-raising reaction is 75°C and the holding time is 2h; the temperature of the second temperature-raising reaction is 130°C and the holding time is 4h;

[0104] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is subjected to reduced pressure rotary evaporation and vacuum filtration to obtain a white solid; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0105] Comparative Example 1

[0106] This comparative example provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0107] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 575.04 g (6.383 mol) of an organic solvent (dimethyl carbonate) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 67 g (0.5 mol) of oxalate (sodium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0108] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.192:1.

[0109] (2) the obtained mixture is subjected to a temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0110] The temperature of the temperature-raising reaction is 65°C and the holding time is 9h;

[0111] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is subjected to reduced pressure rotary evaporation and vacuum filtration to obtain a white solid; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0112] Comparative Example 2

[0113] This comparative example provides a one-pot method for preparing lithium difluorooxalatoborate, the method comprising the following steps:

[0114] (1) In a 1000 mL reaction container, 315.76 g (2 mol) of a boron trifluoride complex (boron trifluoride dimethyl carbonate) and 575.04 g (6.383 mol) of an organic solvent (dimethyl carbonate) were first uniformly mixed, and then 52.98 g (0.52 mol) of lithium oxalate and 67 g (0.5 mol) of oxalate (sodium oxalate) were added at once and uniformly mixed to obtain a mixture;

[0115] The molar ratio of lithium oxalate to boron trifluoride complex is 0.26:1, the molar ratio of oxalate to boron trifluoride complex is 0.25:1, and the molar ratio of organic solvent to boron trifluoride complex is 3.192:1.

[0116] (2) the obtained mixture is subjected to a temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution;

[0117] The temperature of the temperature-raising reaction is 90°C and the holding time is 9h;

[0118] (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is subjected to reduced pressure rotary evaporation and vacuum filtration to obtain a white solid; the white solid is vacuum dried at 120° C. to obtain the lithium difluorooxalate borate.

[0119] The molar yields of the above examples and comparative examples and the purity of the obtained lithium difluorooxalatoborate by ion chromatography analysis are shown in Table 1.

[0120] Table 1

[0121]

[0122]

[0123] As can be seen from Table 1, the method provided by the present invention can realize the preparation of lithium difluorooxalatoborate with a high yield, and can obtain lithium difluorooxalatoborate with a purity of more than 99.95%.

[0124] Among them, if the molar ratio of lithium oxalate to boron trifluoride complex is too large, the purity of lithium difluorooxalate borate will not be further improved, but the yield will be reduced; if the molar ratio of lithium oxalate to boron trifluoride complex is too small, although the purity of lithium difluorooxalate borate will be slightly improved, the yield will be significantly reduced. Therefore, as a preferred embodiment of the present invention, it is necessary to control the molar ratio of lithium oxalate to boron trifluoride complex within a numerical range of 0.26:1 to 0.27:1.

[0125] Among them, if the molar ratio of oxalate to boron trifluoride complex is too large, the yield and purity of the final obtained lithium difluorooxalatoborate are significantly reduced. From the comparison of Example 1 and Example 9 and Example 10 of the present invention, it can be seen that by controlling the molar ratio of oxalate to boron trifluoride complex in the range of 0.25:1 to 0.26:1, a relatively high yield and purity can be obtained.

[0126] Among them, the reaction temperature and insulation time also affect the yield and purity of the method provided by the present invention. From the comparison of Example 1, Example 11, Example 12 and Comparative Example 1 and Comparative Example 2 of the present application, it can be seen that when the temperature and time during the reaction change, the method provided by the present invention cannot achieve the optimal yield and purity.

[0127] In summary, the method provided by the present invention uses an organic solvent as a reaction medium, reacts lithium oxalate, oxalate and a boron trifluoride complex to obtain a reaction solution, and then performs conventional post-treatment to obtain high-purity lithium difluorooxalate borate. Compared with the prior art, the method provided by the present invention is a one-step reaction, which avoids the use of reagents such as hydrofluoric acid, anhydrous hydrogen fluoride and gaseous boron trifluoride, has extremely high reaction selectivity and yield, can not only reduce the reaction steps, is conducive to industrial production, but also can improve the purity of the final obtained lithium difluorooxalate borate.

[0128] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A one-pot method for preparing lithium difluorooxalatoborate, characterized in that: The method comprises the following steps: (1) mixing lithium oxalate, oxalate, a boron trifluoride complex and an organic solvent to obtain a mixture; (2) subjecting the obtained mixture to a first temperature-raising reaction and a second temperature-raising reaction to obtain a reaction liquid; (3) The reaction solution is post-treated to obtain the lithium difluorooxalatoborate.

2. The method according to claim 1, characterized in that The molar ratio of the lithium oxalate to the boron trifluoride complex is 0.25:1 to 0.3:1, preferably 0.26:1 to 0.27:

1.

3. The method according to claim 1 or 2, characterized in that: The molar ratio of the oxalate to the boron trifluoride complex is 0.25:1 to 0.3:1, preferably 0.25:1 to 0.26:

1.

4. The method according to any one of claims 1 to 3, characterized in that: The molar ratio of the organic solvent to the boron trifluoride complex is 3.1:1 to 3.2:

1.

5. The method according to any one of claims 1 to 4, characterized in that: The temperature of the first temperature-raising reaction is 50°C to 75°C, preferably 65°C to 70°C; Preferably, the insulation time of the first temperature rising reaction is 2h to 6h, preferably 3h to 4h.

6. The method according to any one of claims 1 to 5, characterized in that: The temperature of the second temperature-raising reaction is 80°C to 130°C, preferably 85°C to 90°C; Preferably, the insulation time of the second temperature rising reaction is 4h to 9h, preferably 6h to 7h.

7. The method according to any one of claims 1 to 6, characterized in that: The oxalate includes any one of potassium oxalate, sodium oxalate or cesium oxalate or a combination of at least two thereof, preferably sodium oxalate.

8. The method according to any one of claims 1 to 7, characterized in that: The boron trifluoride complex comprises any one of boron trifluoride ethyl ether, boron trifluoride acetonitrile, boron trifluoride dimethyl carbonate, boron trifluoride methanol or boron trifluoride glycol dimethyl ether, or a combination of at least two thereof, preferably boron trifluoride dimethyl carbonate and / or boron trifluoride glycol dimethyl ether.

9. The method according to any one of claims 1 to 8, characterized in that: The organic solvent includes any one of acetonitrile, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene glycol dimethyl ether or methanol, or a combination of at least two thereof, preferably dimethyl carbonate and / or ethylene glycol dimethyl ether.

10. The method according to claim 1, characterized in that The method comprises the following steps: (1) firstly uniformly mixing a boron trifluoride complex and an organic solvent, and then adding lithium oxalate and oxalate and uniformly mixing them to obtain a mixture; The molar ratio of lithium oxalate to boron trifluoride complex is 0.25:1 to 0.3:1; The molar ratio of the oxalate to the boron trifluoride complex is 0.25:1 to 0.3:1; The molar ratio of the organic solvent to the boron trifluoride complex is 3.1:1 to 3.2:1; (2) the obtained mixture is subjected to a first temperature-raising reaction and a second temperature-raising reaction, and then cooled to room temperature to obtain a reaction solution; The temperature of the first temperature-raising reaction is 65° C. to 70° C., and the insulation time is 3 h to 4 h; The temperature of the second temperature-raising reaction is 85° C. to 90° C., and the insulation time is 6 h to 7 h; (3) The reaction solution is vacuum filtered to obtain a lithium difluorooxalate borate filtrate; the lithium difluorooxalate borate filtrate is concentrated under reduced pressure and filtered to obtain a white solid; the white solid is vacuum dried to obtain the lithium difluorooxalate borate.

Images