Preparation method and application of lithium difluoro (oxalato) borate
Through a specific reaction process, the combination of boron fluoride-containing complexes and oxalate compounds with oxalic acid and silane compounds has successfully improved the yield and purity of lithium difluoroxalate borate, solved the problem of difficult separation and purification of by-products in the prior art, and achieved an efficient and low-cost preparation method.
Patent Information
- Application Number
- CN202411391502.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-08
- Publication Date
- 2025-02-25
AI Technical Summary
The existing preparation methods for lithium difluoroxalate borate have problems such as difficult to separate by-product LiBF4, complex purification process, low reaction yield, low production efficiency and high energy consumption.
By mixing the boron fluoride-containing complex, oxalate-containing compound and solvent, a first-stage reaction solution is obtained; then oxalic acid and silane compounds are added, reacted and concentrated, and finally heated and cooled to precipitate to obtain lithium difluorooxalate borate, avoiding the separation operation of lithium tetrafluoroborate and improving yield and purity.
The high purity and high yield preparation of lithium difluoroxalate borate is achieved, the process flow is simplified, the production cost is reduced, and it is suitable for industrial production.
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of lithium difluorooxalatoborate synthesis, and particularly relates to a preparation method and application of lithium difluorooxalatoborate. Background Art
[0002] Electrolyte salt is an important component of lithium-ion battery electrolyte, and its research and development is crucial to the performance and development of lithium-ion secondary batteries. Lithium hexafluorophosphate (LiPF6) is the most widely used electrolyte salt in commercial lithium batteries. It has excellent properties such as high conductivity, high cycle efficiency, the ability to form a stable SEI film on the carbon negative electrode, and effective passivation of the positive electrode current collector. However, LiPF6 also has obvious disadvantages, such as poor thermal stability and easy hydrolysis to generate HF, which leads to battery performance degradation and cannot meet the special application requirements of lithium-ion batteries.
[0003] Lithium difluorooxalatoborate (LiODFB) is a new type of lithium-ion battery electrolyte with great application prospects. Due to its unique molecular structure, it combines the advantages of two lithium salts, lithium bis(oxalatoborate) (LiBOB) and lithium tetrafluoroborate (LiBF4). Compared with traditional electrolytes, lithium difluorooxalatoborate has good thermal stability and a decomposition temperature of 240°C; it has a wide operating temperature range, with both the high temperature performance of LiBOB and the low temperature performance of LiBF4; it has excellent high and low temperature performance, and has good electrochemical properties at -20°C and 60°C; it has excellent film-forming properties and can help form a stable SEI film in the electrolyte. It also has good cycle stability, good solubility and excellent rate discharge performance. Based on the above advantages, LiODFB is widely used in lithium-ion battery electrolytes.
[0004] At present, there are many preparation methods for lithium difluorooxalatoborate, but the existing preparation process still has shortcomings. For example, LiODFB will produce a by-product LiBF4 during the preparation process, and it is difficult to separate. Multiple recrystallizations are required to obtain a relatively pure LiODFB product. The purification process is complicated, the reaction yield is low, the production efficiency is low, and the energy consumption is high.
[0005] Therefore, it is of great significance to provide a method for preparing lithium difluorooxalatoborate which has a simple synthesis method, is easy to purify, has low cost, and has high purity and high yield. Summary of the invention
[0006] The present invention aims to solve one or more technical problems existing in the above-mentioned prior art, and at least provide a beneficial choice or create conditions. Specifically, the present invention provides a preparation method of lithium difluorooxalate borate, which has a simple synthesis method, is easy to purify, and has low cost, and the prepared lithium difluorooxalate borate has high purity and high yield.
[0007] The inventive concept of the present invention: The preparation method of the lithium difluorooxalate borate of the present invention is to mix a fluoride-containing boron complex, an oxalate-containing compound, and a solvent, react to obtain a primary reaction liquid; then mix oxalic acid, a silane compound, and the primary reaction liquid, react to obtain a secondary reaction liquid; then concentrate the secondary reaction liquid, add a solvent, heat, cool and precipitate, and obtain lithium difluorooxalate borate. After the primary reaction liquid containing lithium difluorooxalate borate and lithium tetrafluoroborate is obtained by a specific reaction, oxalic acid and a silane compound are added to convert the byproduct lithium tetrafluoroborate into lithium difluorooxalate borate, without the need to separate lithium difluorooxalate borate and lithium tetrafluoroborate, the yield and purity of lithium difluorooxalate borate can be improved, and the operation is simple and the production cost is low.
[0008] Therefore, the first aspect of the present invention provides a method for preparing lithium difluorooxalatoborate.
[0009] Specifically, the preparation method of lithium difluorooxalatoborate comprises the following steps:
[0010] (1) mixing a fluoride-containing boron complex, an oxalate-containing compound, and a solvent, and reacting them to obtain a primary reaction solution;
[0011] (2) mixing oxalic acid, a silane compound, and the primary reaction solution obtained in step (1), and reacting the mixture to obtain a secondary reaction solution;
[0012] (3) Concentrating the secondary reaction solution obtained in step (2), adding a solvent, heating, cooling and precipitation to obtain lithium difluorooxalatoborate.
[0013] Specifically, the primary reaction liquid is a primary reaction liquid containing lithium difluorooxalatoborate and lithium tetrafluoroborate.
[0014] Specifically, after step (2), the byproduct lithium tetrafluoroborate is converted into lithium difluorooxalatoborate to obtain a secondary reaction liquid of lithium difluorooxalatoborate.
[0015] Preferably, in step (1), the boron fluoride complex comprises at least one of boron trifluoride acetonitrile, boron trifluoride tetrahydrofuran, boron trifluoride ether and boron trifluoride methanol.
[0016] Preferably, in step (1), the oxalate-containing compound includes at least one of lithium oxalate and lithium hydrogen oxalate.
[0017] Preferably, in step (1), the solvent comprises at least one of diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ethyl methyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, ethyl butyl carbonate, ethylene carbonate, propylene carbonate, methyl acetate, ethyl acetate, butyl acetate, acetonitrile, propionitrile, butyronitrile and tetrahydrofuran.
[0018] Specifically, in step (1), the solvent is a polar aprotic solvent.
[0019] Preferably, in step (1), the molar ratio of the boron fluoride complex to the oxalate compound is (1.8-11):1; further preferably, in step (1), the molar ratio of the boron fluoride complex to the oxalate compound is (2-10):1.
[0020] Preferably, in step (1), the reaction temperature is 18-130°C, and the reaction time is 0.5-26h; further preferably, in step (1), the reaction temperature is 20-120°C, and the reaction time is 0.5-24h.
[0021] Preferably, in step (2), the silane compound includes at least one of hexamethyldisilazane, hexamethyldisiloxane, methyldichlorosilane and silicon tetrachloride.
[0022] Preferably, the molar ratio of the oxalic acid to the oxalate-containing compound is (0.9-5.5):1; further preferably, the molar ratio of the oxalic acid to the oxalate-containing compound is (1-5):1.
[0023] Preferably, the molar ratio of the silane compound to the oxalate-containing compound is (0.9-11):1; further preferably, the molar ratio of the silane compound to the oxalate-containing compound is (1-10):1.
[0024] Preferably, in step (2), the reaction temperature is 18-130°C, and the reaction time is 0.5-26h; further preferably, in step (2), the reaction temperature is 20-120°C, and the reaction time is 0.5-24h.
[0025] Preferably, in step (3), the solvent comprises at least one of diethyl carbonate, ethyl methyl carbonate, ethyl acetate and acetonitrile.
[0026] Specifically, in step (3), the solvent is a benign solvent.
[0027] Preferably, in step (3), the heating temperature is 90-220°C; further preferably, in step (3), the heating temperature is 100-200°C.
[0028] Specifically, a crude product is obtained after concentration, and the crude product is completely dissolved by heating.
[0029] Preferably, in step (3), after cooling and precipitation, the process of filtering, washing and vacuum drying is also included; the pressure of the vacuum drying is -0.1MPa to -0.07MPa, the temperature of the vacuum drying is 55-220°C, and the time of the vacuum drying is 2-52h; further preferably, the pressure of the vacuum drying is -0.1MPa to -0.08MPa, the temperature of the vacuum drying is 60-200°C, and the time of the vacuum drying is 4-48h.
[0030] Preferably, washing is performed with an inert solvent.
[0031] Preferably, the inert solvent includes at least one of dichloromethane, 1,2-dichloroethane, diethyl ether, n-hexane and cyclohexane.
[0032] The second aspect of the present invention provides an application of the preparation method of lithium difluorooxalatoborate described in the first aspect of the present invention in the field of preparing battery materials.
[0033] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:
[0034] (1) The present invention obtains a primary reaction liquid containing lithium difluorooxalatoborate and lithium tetrafluoroborate through a specific reaction, and then adds oxalic acid and a silane compound to convert the byproduct lithium tetrafluoroborate into lithium difluorooxalatoborate. There is no need to separate lithium difluorooxalatoborate and lithium tetrafluoroborate, so the yield and purity of lithium difluorooxalatoborate can be improved, and the operation is simple and the production cost is low.
[0035] (2) The synthesis and purification process of the present invention is simple, the synthesis process can be operated in the air, the reaction time is short, the production cost is low, the prepared lithium difluorooxalatoborate product has a high yield and high purity, is suitable for industrial production, and has broad application prospects. DETAILED DESCRIPTION
[0036] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.
[0037] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.
[0038] Example 1
[0039] A method for preparing difluorinated lithium oxalate borate comprises the following steps:
[0040] (1) Add 0.5 mol, 50.95 g of lithium oxalate and 300 mL of diethyl carbonate to a dry reaction bottle, stir and mix evenly, then dropwise add 1.0 mol, 108.86 g of boron trifluoride acetonitrile solution to the reaction bottle. After the dropwise addition is complete, continue stirring and reacting at 20° C. for 24 h to obtain a primary reaction solution;
[0041] (2) The primary reaction solution obtained in step (1) was adjusted to room temperature, 0.5 mol, 45 g oxalic acid was added, and 5 mol, 806.95 g hexamethyldisilazane was slowly added dropwise. After the addition was completed, the reaction was continued at 20° C. with stirring for 0.5 h to obtain a secondary reaction solution;
[0042] (3) The secondary reaction liquid obtained in step (2) was concentrated, and then 300 mL of diethyl carbonate was added, heated to 100° C. to dissolve, cooled to precipitate, filtered, and the solid was washed with dichloromethane. Finally, it was placed in a vacuum drying oven at 60° C. and -0.1 MPa and dried for 24 h to obtain 133.72 g of a white powdery solid, namely, lithium difluorooxalatoborate. The theoretical yield was 143.78 g, and the yield was actual yield / theoretical yield×100%. After calculation, the yield was 93%.
[0043] Example 2
[0044] A method for preparing lithium difluorooxalatoborate comprises the following steps:
[0045] (1) Add 0.5 mol, 50.95 g of lithium oxalate and 300 mL of ethyl methyl carbonate to a dry reaction bottle, stir and mix evenly, and under stirring, dropwise add 10 mol, 1399.1 g of boron trifluoride tetrahydrofuran solution to the reaction bottle. After the dropwise addition is complete, heat to 120° C. and continue stirring and reacting for 0.5 h to obtain a primary reaction solution;
[0046] (2) The primary reaction liquid obtained in step (1) was cooled to room temperature, and then 2.5 mol, 225 g, of oxalic acid was added, and 0.5 mol, 84.95 g of silicon tetrachloride was slowly added dropwise. After the addition was completed, the reaction was continued at 120° C. with stirring for 15 h to obtain a secondary reaction liquid;
[0047] (3) The secondary reaction liquid obtained in step (2) was concentrated, 300 mL of acetonitrile was added, and the mixture was heated to 100° C. to dissolve. The mixture was cooled and precipitated, filtered, and the solid was washed with cyclohexane. Finally, the solid was dried in a vacuum drying oven at 200° C. and −0.1 MPa for 24 h to obtain 130.86 g of a white powdery solid, namely, lithium difluorooxalatoborate. The theoretical yield was 143.78 g, and the yield was actual yield / theoretical yield × 100%. After calculation, the yield was 91%.
[0048] Example 3
[0049] A method for preparing lithium difluorooxalatoborate comprises the following steps:
[0050] (1) Add 0.5 mol, 50.95 g of lithium oxalate and 300 mL of tetrahydrofuran to a dry reaction bottle, stir and mix evenly, and under stirring, dropwise add 2.5 mol, 249.63 g of boron trifluoride methanol solution to the reaction bottle. After the dropwise addition is complete, heat to 60° C. and continue stirring and reacting for 12 h to obtain a primary reaction solution;
[0051] (2) The primary reaction liquid obtained in step (1) was cooled to room temperature, 1.25 mol, 112.5 g oxalic acid was added, and 2.5 mol, 290.1 g methyl dichlorosilane was slowly added dropwise. After the addition was completed, the reaction was continued at 60° C. with stirring for 12 h to obtain a secondary reaction liquid;
[0052] (3) The secondary reaction liquid obtained in step (2) was concentrated, 300 mL of ethyl acetate was added, and the mixture was heated to 100° C. to dissolve. The mixture was cooled and precipitated, filtered, and the solid was washed with ether. Finally, the solid was dried in a vacuum drying oven at 200° C. and −0.1 MPa for 24 h to obtain 132.01 g of a white powdery solid, namely, lithium difluorooxalatoborate. The theoretical yield was 143.78 g, and the yield was actual yield / theoretical yield×100%. After calculation, the yield was 92%.
[0053] Comparative Example 1
[0054] The difference between Comparative Example 1 and Example 1 is that step (1) of Comparative Example 1 uses different raw materials and processes to prepare the primary reaction liquid, and the remaining steps are the same as Example 1.
[0055] Specifically, the preparation method of lithium difluorooxalatoborate in Comparative Example 1 comprises the following steps:
[0056] (1) In a No. 1 reactor, 26.0 g of lithium fluoride (1.0 mol) and 400 g of anhydrous hydrogen fluoride (20.0 mol) were reacted for 4 h at a temperature of -35°C to obtain a hydrogen fluoride solution of lithium fluoride; the hydrogen fluoride solution of lithium fluoride was pumped into a No. 2 reactor and stirred evenly, then 45.0 g of anhydrous oxalic acid (0.5 mol) was added to the No. 2 reactor, and 117.0 g of boron trichloride gas (1.0 mol) was slowly and evenly introduced from the bottom of the No. 2 reactor for 2 h; during the addition process, the reaction temperature was controlled at 18°C; during the reaction process, the tail gas generated was discharged from the top of the reactor and absorbed by a two-stage film falling device to remove hydrogen fluoride, thereby obtaining 561.6 g of hydrochloric acid with a concentration of 20%; after the boron trichloride gas was introduced, stirring was continued for 30 min to complete the reaction, and then the reaction solution was filtered to remove insoluble matter (impurities in oxalic acid, etc.), thereby obtaining 478.8 g of filtrate, thereby obtaining a primary reaction solution;
[0057] (2) The primary reaction solution obtained in step (1) was adjusted to room temperature, 0.5 mol, 45 g oxalic acid was added, and 5 mol, 806.95 g hexamethyldisilazane was slowly added dropwise. After the addition was completed, the reaction was continued to stir at 20° C. for 0.5 h to obtain a secondary reaction solution;
[0058] (3) The secondary reaction liquid obtained in step (2) was concentrated, and then 300 mL of diethyl carbonate was added, heated to 100° C. to dissolve, cooled to precipitate, filtered, and the solid was washed with dichloromethane. Finally, it was placed in a vacuum drying oven at 60° C. and -0.1 MPa and dried for 24 h to obtain 105.74 g of a white powdery solid, namely, lithium difluorooxalatoborate. The theoretical yield was 143.78 g, and the yield was actual yield / theoretical yield×100%. After calculation, the yield was 74%.
[0059] Comparative Example 2
[0060] The only difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the molar ratio of the boron fluoride complex to the oxalate compound is 1:1, and the rest is the same as Example 1.
[0061] Comparative Example 2 obtained 115.56 g of white powdery solid, namely, lithium difluorooxalatoborate, with a theoretical yield of 143.78 g. The yield was actual yield / theoretical yield×100%. After calculation, the yield was 80%.
[0062] Comparative Example 3
[0063] The only difference between Comparative Example 3 and Example 1 is that the reaction temperature of steps (1) and (2) of Comparative Example 3 is 150° C., that is, the reaction is stirred at 150° C., and the rest is the same as Example 1.
[0064] Comparative Example 3 obtained 130.18 g of white powdery solid, namely, lithium difluorooxalatoborate, with a theoretical yield of 143.78 g. The yield was actual yield / theoretical yield. After calculation, the yield reached 90.5%.
[0065] Performance Testing
[0066] The purity of the lithium difluorooxalatoborate prepared in Examples 1-3 and Comparative Examples 1-3 was tested using a 600 MHz Fourier transform nuclear magnetic resonance spectrometer (FT-NMR). The test results are shown in Table 1.
[0067] Table 1: Purity (mass fraction) of lithium difluorooxalate borate prepared in Examples 1-3 and Comparative Examples 1-3
[0068] Test items Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 purity 99.9％ 99.9％ 99.9％ 88.3％ 89.6％ 82.3％
[0069] It can be seen from Table 1 that the lithium difluorooxalatoborate prepared by the preparation method of the present invention has high purity, and the purity can reach 99.9%.
[0070] Comparative Example 1 uses different raw materials and processes to prepare the primary reaction liquid, so that the purity of lithium difluorooxalatoborate in Comparative Example 1 is significantly lower than that in Example 1, indicating that the use of specific raw materials and processes to prepare the primary reaction liquid can improve the purity of the product.
[0071] Comparative Example 2 changed the molar ratio of the boron fluoride complex and the oxalate compound, and Comparative Example 3 changed the reaction temperature during the preparation of the primary reaction liquid and the secondary reaction liquid, so that the purity of Comparative Examples 2 and 3 was significantly lower than that of Example 1, indicating that the specific dosage ratio between the raw materials and the specific reaction temperature play an extremely important role in the purity of the product.
[0072] In summary, the present invention obtains a primary reaction liquid containing lithium difluorooxalatoborate and lithium tetrafluoroborate through specific raw materials and processes, and then adds oxalic acid and a silane compound to convert the byproduct lithium tetrafluoroborate into lithium difluorooxalatoborate. There is no need to separate lithium difluorooxalatoborate and lithium tetrafluoroborate, and the yield and purity of lithium difluorooxalatoborate can be improved.
[0073] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.
Claims
1. A method for preparing lithium difluorooxalatoborate, characterized in that: The following steps are involved: (1) mixing a fluoride-containing boron complex, an oxalate-containing compound, and a solvent, and reacting them to obtain a primary reaction solution; (2) mixing oxalic acid, a silane compound, and the primary reaction solution obtained in step (1), and reacting the mixture to obtain a secondary reaction solution; (3) Concentrating the secondary reaction solution obtained in step (2), adding a solvent, heating, cooling and precipitation to obtain lithium difluorooxalatoborate.
2. The preparation method according to claim 1, characterized in that: In step (1), the fluoride-containing boron complex includes at least one of boron trifluoride acetonitrile, boron trifluoride tetrahydrofuran, boron trifluoride ether, and boron trifluoride methanol; and / or, the oxalate-containing compound includes at least one of lithium oxalate and lithium hydrogen oxalate; and / or, the solvent includes at least one of diethyl carbonate, dipropyl carbonate, dibutyl carbonate, ethyl methyl carbonate, ethyl propyl carbonate, methyl butyl carbonate, ethyl butyl carbonate, ethylene carbonate, propylene carbonate, methyl acetate, ethyl acetate, butyl acetate, acetonitrile, propionitrile, butyronitrile, and tetrahydrofuran.
3. The preparation method according to claim 1, characterized in that: In step (1), the molar ratio of the boron fluoride complex to the oxalate compound is (1.8-11):
1.
4. The preparation method according to claim 1, characterized in that: In step (1), the reaction temperature is 18-130° C., and the reaction time is 0.5-26 h.
5. The preparation method according to claim 1, characterized in that: In step (2), the silane compound includes at least one of hexamethyldisilazane, hexamethyldisiloxane, methyldichlorosilane, and silicon tetrachloride.
6. The preparation method according to claim 1, characterized in that: The molar ratio of the oxalic acid to the oxalate-containing compound is (0.9-5.5):1; and / or the molar ratio of the silane compound to the oxalate-containing compound is (0.9-11):
1.
7. The preparation method according to claim 1, characterized in that: In step (2), the reaction temperature is 18-130° C., and the reaction time is 0.5-26 h.
8. The preparation method according to claim 1, characterized in that: In step (3), the solvent includes at least one of diethyl carbonate, ethyl methyl carbonate, ethyl acetate, and acetonitrile.
9. The preparation method according to claim 1, characterized in that: In step (3), the heating temperature is 90-220°C; And / or, the cooling and precipitation further includes filtering, washing and vacuum drying processes; the vacuum drying pressure is -0.1MPa to -0.07MPa, the vacuum drying temperature is 55-220°C, and the vacuum drying time is 2-52h.
10. Application of the preparation method according to any one of claims 1 to 9 in the field of preparing battery materials.