Preparation method of electrolyte salt lithium difluoro (oxalato) borate for lithium ion battery
Lithium difluorooxalate borate was prepared by reacting oxalic acid, lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride complex. This method solves the problems of low conversion rate and serious pollution in the existing technology, and achieves high purity and high yield, reducing production costs and environmental impact.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YANTAI YUCHEN NEW MATERIAL TECH R&D CO LTD
- Filing Date
- 2026-01-16
- Publication Date
- 2026-05-05
AI Technical Summary
In the existing technology, the preparation method of lithium difluorooxalate borate has problems such as low conversion rate, low product purity and yield, and the generation of corrosive gases during the reaction process, resulting in high production costs and serious environmental pollution.
Lithium difluorooxalate borate is prepared by reacting oxalic acid, lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride complex in an organic solvent via a one-pot method. By controlling the reaction temperature and vacuum concentration conditions, and combining crystallization with unsuitable solvents with vacuum drying, the process is simplified and impurity generation is avoided.
The preparation of lithium difluorooxalate borate with high conversion rate and high purity has been achieved, simplifying the production steps, reducing production costs and environmental pollution, conforming to the concept of green chemistry, and having significant industrial application value.
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Abstract
Description
Technical Field
[0001] This application relates to the technical field of chemical synthesis, specifically to a method for preparing lithium difluorooxalate borate, an electrolyte salt for lithium-ion batteries. Background Technology
[0002] Electrolytes, as a key component of lithium-ion batteries, have always been a research focus in this field. Currently, commercially available LiPF6 batteries suffer from insufficient thermal stability and are prone to decomposition, producing highly corrosive HF that adversely affects electrode performance.
[0003] Lithium difluorooxalate borate (LiDFOB), as an electrolyte additive, not only exhibits good high and low temperature performance but also forms a stable SEI film structure on the surface of electrode materials, significantly improving the cycle performance of lithium-ion batteries. Currently, the preparation methods of LiDFOB both domestically and internationally are divided into the boron trifluoride (BF3) complex method and the lithium tetrafluoroborate (LiBF4) method.
[0004] The BF3 complex method involves reacting BF3 complex and lithium oxalate as raw materials with diethyl ether or carbonate as solvent to obtain a crude mixture of LiBF4 and LiDFOB. The target product is then obtained after multiple recrystallizations. However, because LiBF4 and LiDFOB have similar solubilities in common solvents, product separation is difficult, resulting in low yields.
[0005] The LiBF4 method uses oxalic acid and BF3 complex as raw materials. A catalyst (silicon tetrachloride, aluminum trichloride, silicon tetrabromide, or boron tribromide) is added to solvents such as carbonates or acetonitrile and the reaction is carried out in a dry environment to obtain a solution containing LiDFOB. After concentration, low-temperature crystallization and vacuum drying, a product with a purity of 99.9% can be obtained. However, this method introduces a large amount of chloride or bromide ions into the product, and a large amount of acidic gas is generated during the reaction, making tail gas treatment cumbersome.
[0006] Therefore, how to provide a method for preparing lithium difluorooxalate borate with high conversion rate, high product purity and yield, and no corrosive gases generated during the reaction process is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0007] To address the aforementioned technical problems, this application provides a method for preparing lithium difluorooxalate borate, an electrolyte salt for lithium-ion batteries.
[0008] This application provides a method for preparing lithium difluorooxalate borate, comprising the following steps: (1) Mix oxalic acid, lithium fluoride, boric acid, lithium hydroxide, boron trifluoride complex and organic solvent, heat and react, filter to obtain a reaction solution containing LiDFOB; wherein the reaction temperature is 50~120℃ and the reaction time is 4~48h; (2) The reaction solution containing LiDFOB is concentrated under vacuum until a white solid precipitates out. The solution is then cooled, a poor solvent is added to induce crystallization, and the solution is filtered to obtain a wet product. The target product is obtained by vacuum drying.
[0009] The reaction formula for the preparation method of lithium difluorooxalate borate provided in this application is shown in formula (1).
[0010]
[0011] Equation (1) This application uses oxalic acid, lithium fluoride, boric acid, lithium hydroxide, boron trifluoride complex, and organic solvent as raw materials to prepare lithium difluorooxalate borate in a one-pot process. This method significantly simplifies the traditional process and achieves high product conversion rate by optimizing reaction conditions. More importantly, no other impurities are generated during the entire reaction process, which means that the product has higher purity and eliminates the need for complex purification steps, directly reducing production costs and energy consumption.
[0012] The above methods are green, environmentally friendly, and pollution-free, fully in line with the concept of green chemistry. They also significantly reduce enterprises' environmental protection investment and operating costs, achieving a win-win situation for both economic and environmental benefits, and have significant industrial application value.
[0013] Preferably, the boron trifluoride complex is selected from one or more of boron trifluoride diethyl carbonate, boron trifluoride acetonitrile, boron trifluoride dimethyl carbonate, boron trifluoride diethyl ether, and boron trifluoride ethylene carbonate.
[0014] Preferably, the molar ratio of the oxalic acid to the complex of lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride is 1:0.5~0.55:0.5~0.55:0.5~0.55:0.5~0.55.
[0015] Preferably, the molar ratio of the oxalic acid to the complex of lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride is 1:0.5~0.52:0.5~0.52:0.5~0.52:0.525~0.55.
[0016] In one specific embodiment, the molar ratio of the oxalic acid to the lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride complex can be 1:0.5:0.5:0.5:0.5, 1:0.52:0.5:0.5:0.5, 1:0.5:0.52:0.5:0.5, 1:0.5:0.5:0.52:0.5, 1:0.5:0.5:0.52, 1 :0.52:0.5:0.5:0.52, 1:0.5:0.52:0.5:0.52, 1:0.5:0.5:0.52:0.52, 1:0.5:0.5:0.5:0.55, 1:0.52:0.5:0.5:0.55, 1:0.5:0.52:0.5:0.55, 1:0.5:0.5:0.52:0.55.
[0017] Preferably, the organic solvent is selected from one or more of ester solvents, ether solvents, and nitrile solvents.
[0018] Preferably, the ester solvent is selected from dimethyl carbonate and diethyl carbonate; the ether solvent is selected from diethyl ether and ethylene glycol dimethyl ether; and the nitrile solvent is selected from acetonitrile.
[0019] Preferably, the reaction temperature is 60~100℃ and the reaction time is 6~16h.
[0020] Preferably, the reaction temperature is 70~90℃ and the reaction time is 6~12h.
[0021] Experimental analysis shows that controlling the reaction temperature within the above-mentioned range can further improve the yield of the target product.
[0022] Preferably, the process parameters for vacuum concentration are: pressure of -0.09 to -0.095 MPa and temperature of 50 to 80°C.
[0023] Preferably, the cooling temperature is 0~30℃.
[0024] Preferably, the undesirable solvent is selected from one or more of dichloromethane, trichloromethane, toluene, xylene, and n-heptane.
[0025] Preferably, the undesirable solvent is composed of a mixture of dichloromethane and toluene in a weight ratio of 1:0.3~0.5.
[0026] Experimental analysis shows that the use of dichloromethane and toluene in the above weight ratio as a poor solvent can further improve the yield of the target product.
[0027] Preferably, the process parameters for vacuum drying are: pressure of -0.095 to -0.1 MPa and drying temperature of 70 to 110°C.
[0028] In summary, the technical solution of this application has the following effects: This application provides a novel preparation method for lithium difluorooxalate borate, which has the following advantages: the preparation method is simple, the product conversion rate is high, and no other impurities are generated; no waste is generated during the entire production process, which is environmentally friendly; and it avoids the disadvantages of other preparation processes, such as multiple reaction steps, large amounts of waste generated, and excessive impurities in the final product. Attached Figure Description
[0029] Figure 1 The image shows the X-ray diffraction pattern of lithium difluorooxalatoborate prepared in Example 1.
[0030] Figure 2 This is the X-ray diffraction pattern of standard lithium difluorooxalate borate. Detailed Implementation
[0031] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.
[0032] Example
[0033] Example 1 Example 1 provides a lithium difluorooxalate borate and its preparation method.
[0034] The specific preparation method of lithium difluorooxalate borate in this embodiment is shown below.
[0035] At room temperature, 360 g of dimethyl carbonate, 0.666 mol of anhydrous oxalic acid (60.00 g), 0.333 mol of boric acid (20.59 g), 0.333 mol of lithium fluoride (8.64 g), 0.333 mol of lithium hydroxide (7.98 g), and 0.35 mol of boron trifluoride DMC complex (55.34 g) were added to a sealed reactor. The reaction system was heated to 90 °C and the reaction was stopped after 8 h. After cooling to room temperature, the reaction solution was filtered through a 1 μm pore size filter to remove unreacted raw materials, yielding a reaction solution containing LiDFOB. The molar ratio of oxalic acid to lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride complex was 1:0.5:0.5:0.5:0.525.
[0036] The reaction solution containing LiDFOB was concentrated under vacuum at -0.09 MPa and 60°C until a white solid precipitated. The solution was then cooled to 20°C, and 100 g of a poor solvent (a mixture of dichloromethane and toluene in a weight ratio of 1:0.3) was added to induce crystallization. The crystals were then filtered to obtain wet lithium difluorooxalate borate. The wet lithium difluorooxalate borate was then vacuum dried at -0.1 MPa and 80°C for 24 h to obtain 91.07 g of the target product, with a yield of 95.05%. The water content was <50 ppm, the acid content was <90 ppm, and the content of various metal impurities was <5 ppm.
[0037] like Figure 1 The image shows the X-ray diffraction pattern of lithium difluorooxalatoborate prepared in Example 1. Figure 2 This is the X-ray diffraction pattern of standard lithium difluorooxalate borate. A comparison shows that the X-ray diffraction pattern of the lithium difluorooxalate borate prepared in this application is consistent with the standard pattern. Figure 1 Lithium difluorooxalate borate was successfully prepared.
[0038] Example 2
[0039] Example 2 provides a lithium difluorooxalate borate and its preparation method.
[0040] The specific preparation method of lithium difluorooxalate borate in this embodiment is shown below.
[0041] At room temperature, 360 g of dimethyl carbonate, 0.666 mol anhydrous oxalic acid (60.00 g), 0.366 mol boric acid (22.65 g), 0.366 mol lithium fluoride (9.50 g), 0.333 mol lithium hydroxide (7.98 g), and 0.35 mol boron trifluoride DMC complex (55.34 g) were added to a sealed reactor. The reaction system was heated to 80 °C and the reaction was stopped after 12 h. After cooling to room temperature, the reaction solution was filtered through a 1 μm pore size filter to remove unreacted raw materials, yielding a reaction solution containing LiDFOB. The molar ratio of oxalic acid to lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride complex was 1:0.55:0.55:0.5:0.525.
[0042] The reaction solution containing LiDFOB was concentrated under vacuum at -0.09 MPa and 60°C until a white solid precipitated. The solution was then cooled to 20°C, and 100 g of a poor solvent (a mixture of dichloromethane and toluene in a weight ratio of 1:0.3) was added to induce crystallization. The crystals were then filtered to obtain wet lithium difluorooxalate borate. The wet lithium difluorooxalate borate was then vacuum dried at -0.1 MPa and 80°C for 24 h to obtain 91.83 g of the target product, with a yield of 95.85%. The water content was <50 ppm, the acid content was <90 ppm, and the content of various metal impurities was <5 ppm.
[0043] Example 3
[0044] Example 3 provides a lithium difluorooxalate borate and its preparation method.
[0045] The specific preparation method of lithium difluorooxalate borate in this embodiment is shown below.
[0046] At room temperature, 360 g of acetonitrile, 0.666 mol of anhydrous oxalic acid (60.00 g), 0.333 mol of boric acid (20.59 g), 0.333 mol of lithium fluoride (8.64 g), 0.333 mol of lithium hydroxide (7.98 g), and 0.35 mol of boron trifluoride acetonitrile complex (38.06 g) were added to a sealed reactor. The reaction system was heated to 80 °C and the reaction was stopped after 12 h. After cooling to room temperature, the reaction solution was filtered through a 1 μm pore size filter to remove unreacted raw materials, yielding a reaction solution containing LiDFOB. The molar ratio of oxalic acid to lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride complex was 1:0.5:0.5:0.5:0.525.
[0047] The reaction solution containing LiDFOB was concentrated under vacuum at -0.09 MPa and 60°C until a white solid precipitated. The solution was then cooled to 20°C, and 100 g of a poor solvent (a mixture of dichloromethane and toluene in a weight ratio of 1:0.3) was added to induce crystallization. The crystals were then filtered to obtain wet lithium difluorooxalate borate. The wet lithium difluorooxalate borate was then vacuum dried at -0.1 MPa and 80°C for 24 h to obtain 93.12 g of the target product, with a yield of 97.19%. The water content was <50 ppm, the acid content was <90 ppm, and the content of various metal impurities was <5 ppm.
[0048] Examples 4-7 Examples 4-7 provide a lithium difluorooxalatoborate and its preparation method, respectively.
[0049] The difference between Example 4 and Example 3 is that the reaction temperature is 50°C and the reaction is completed after 18 hours.
[0050] The difference between Example 5 and Example 3 is that the reaction temperature is 60°C and the reaction is completed after 12 hours.
[0051] The difference between Example 6 and Example 3 is that the reaction temperature is 100°C and the reaction is completed after 10 hours.
[0052] The difference between Example 7 and Example 3 is that the reaction temperature is 120°C and the reaction is completed after 10 hours.
[0053] All other process parameters in the above embodiments are the same as those in Embodiment 3.
[0054] The result is: Example 4 yielded 91.15 g of the target product, with a yield of 95.14%.
[0055] Example 5 yielded 92.79 g of the target product, with a yield of 96.85%.
[0056] Example 6 yielded 92.94 g of the target product, with a yield of 97.01%.
[0057] Example 7 yielded 90.85 g of the target product, with a yield of 94.83%.
[0058] In the above embodiments, the target product has a water content of <50ppm, an acid content of <90ppm, and a content of each metal impurity of <5ppm.
[0059] Examples 8-12 Examples 8-12 provide a lithium difluorooxalatoborate and its preparation method, respectively.
[0060] The difference between Example 8 and Example 3 is that the molar ratio of oxalic acid (0.666 mol) to the complex of lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride in the raw materials is 1:0.5:0.5:0.5:0.55.
[0061] The difference between Example 9 and Example 3 is that the molar ratio of oxalic acid (0.666 mol) to the complex of lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride in the raw materials is 1:0.5:0.5:0.5:0.5.
[0062] The difference between Example 10 and Example 3 is that the poor solvent is composed of a mixture of dichloromethane and xylene in a weight ratio of 1:0.3.
[0063] The difference between Example 11 and Example 3 is that the poor solvent is composed of a mixture of dichloromethane and toluene in a weight ratio of 0.3:1.
[0064] The difference between Example 12 and Example 3 is that the poor solvent is composed of a mixture of dichloromethane and toluene in a weight ratio of 1:0.5.
[0065] All other process parameters in the above embodiments are the same as those in Embodiment 3.
[0066] The result is: Example 8 yielded 92.92 g of the target product, with a yield of 96.99%.
[0067] Example 9 yielded 90.82 g of the target product, with a yield of 94.79%.
[0068] Example 10 yielded 91.03 g of the target product, with a yield of 95.01%.
[0069] Example 11 yielded 90.84 g of the target product, with a yield of 94.81%.
[0070] Example 12 yielded 92.75 g of the target product, with a yield of 96.81%.
[0071] In the above embodiments, the target product has a water content of <50ppm, an acid content of <90ppm, and a content of each metal impurity of <5ppm.
[0072] By comparing the test results of Examples 3-7, it can be seen that the reaction temperature has a significant impact on the yield of the target product. This application controls the reaction temperature to 60-100℃, which can significantly improve the yield of the target product.
[0073] Comparing the test results of Examples 3 and 8-9, it is evident that the molar ratio of oxalic acid to the lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride complex in the raw materials has a significant impact on the yield of the target product. This application controls the molar ratio of oxalic acid to the lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride complex to 1:0.5~0.52:0.5~0.52:0.5~0.52:0.525~0.55, which can significantly improve the yield of the target product.
[0074] By comparing the test results of Examples 3 and 10-12, it can be seen that the type of unsuitable solvent has a significant impact on the yield of the target product. This application selects a mixture of dichloromethane and toluene in a weight ratio of 1:0.3~0.5 as the unsuitable solvent, which can significantly improve the yield of the target product.
[0075] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.
Claims
1. A method for preparing lithium difluorooxalate borate, characterized in that, This includes the following steps: (1) Mix oxalic acid, lithium fluoride, boric acid, lithium hydroxide, boron trifluoride complex and organic solvent, heat and react, filter to obtain a reaction solution containing LiDFOB; wherein the reaction temperature is 50~120℃ and the reaction time is 4~48h; (2) The reaction solution containing LiDFOB is concentrated under vacuum until a white solid precipitates out. The solution is then cooled, a poor solvent is added to induce crystallization, and the solution is filtered to obtain a wet product. The target product is obtained by vacuum drying.
2. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The boron trifluoride complex is selected from one or more of boron trifluoride diethyl carbonate, boron trifluoride acetonitrile, boron trifluoride dimethyl carbonate, boron trifluoride diethyl ether, and boron trifluoride ethylene carbonate.
3. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The molar ratio of the oxalic acid complex with lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride is 1:0.5~0.55:0.5~0.55:0.5~0.55:0.5~0.
55.
4. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The molar ratio of the oxalic acid complex with lithium fluoride, boric acid, lithium hydroxide, and boron trifluoride is 1:0.5~0.52:0.5~0.52:0.5~0.52:0.525~0.
55.
5. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The organic solvent is selected from one or more of ester solvents, ether solvents, and nitrile solvents; the ester solvent is selected from dimethyl carbonate and diethyl carbonate; the ether solvent is selected from diethyl ether and dimethyl ethylene glycol ether; and the nitrile solvent is selected from acetonitrile.
6. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The reaction temperature is 60~100℃, and the reaction time is 6~16h.
7. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The process parameters for vacuum concentration are: pressure of -0.09 to -0.095 MPa and temperature of 50 to 80°C.
8. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The cooling temperature is 0~30℃.
9. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The undesirable solvent is selected from one or more of dichloromethane, trichloromethane, toluene, xylene, and n-heptane.
10. The method for preparing lithium difluorooxalatoborate according to claim 1, characterized in that, The process parameters for vacuum drying are: pressure of -0.095 to -0.1 MPa and drying temperature of 70 to 110°C.