Method for efficiently preparing lithium difluoro (oxalato) borate
The preparation of lithium difluorooxalate borate by reacting lithium tetrafluoroborate with anhydrous aluminum oxalate solves the problems of high raw material cost, complex steps and environmental pollution in the existing technology, and realizes the efficient and environmentally friendly preparation of LiODFB, which is suitable for the industrial production of electrolyte salts for lithium-ion batteries.
Patent Information
- Application Number
- CN202511504536.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-21
- Publication Date
- 2026-01-09
AI Technical Summary
Existing methods for preparing LiODFB suffer from problems such as high raw material costs, harsh reaction conditions, complex steps, and environmental pollution, which limit their large-scale industrial production.
Lithium difluorooxalate borate was prepared by reacting lithium tetrafluoroborate with anhydrous aluminum oxalate through steps such as heating reaction, solid-liquid separation, crystallization and drying. The in-situ catalytic effect of anhydrous aluminum oxalate was utilized to generate lithium difluorooxalate borate and aluminum fluoride, which simplified the process.
It achieves low-cost, high-efficiency LiODFB preparation with a yield of over 96.5% and a purity of over 99.8%. It is environmentally friendly, with recyclable byproducts, and is suitable for large-scale industrial production.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery electrolyte salt preparation technology, specifically relating to a method for efficiently preparing lithium difluorooxalate borate, which involves reacting lithium tetrafluoroborate with anhydrous aluminum oxalate to prepare lithium difluorooxalate borate and aluminum fluoride. Background Technology
[0002] Lithium-ion batteries have become the mainstream power source for electric vehicles, portable electronic devices, and other fields due to their advantages such as high energy density, long cycle life, and no memory effect. The electrolyte, as a key component of lithium-ion batteries, directly affects the battery's cycle performance, safety performance, and adaptability to high and low temperatures. While traditional lithium hexafluorophosphate (LiPF6) possesses high ionic conductivity and good electrochemical performance, it suffers from poor thermal stability and is prone to hydrolysis, producing corrosive hydrogen fluoride gas, which limits its application in high-temperature environments and high-voltage batteries.
[0003] In recent years, lithium difluorooxalate borate (LiBF2C2O4, or LiDFOB or LiODFB) has attracted widespread attention as a novel electrolyte lithium salt. LiODFB combines the advantages of lithium tetrafluoroborate (LiBF4) and lithium bis(oxalate borate) (LiBOB), exhibiting high ionic conductivity, excellent thermal stability, and good film-forming properties. It can form a stable solid electrolyte interphase (SEI) film on the graphite anode surface, improving the battery's cycle performance and high / low temperature performance. Furthermore, LiODFB has a good passivation effect on aluminum current collectors, effectively inhibiting aluminum corrosion and improving battery safety and reliability.
[0004] Currently, the main methods for synthesizing LiODFB are as follows: The direct reaction method of boron trifluoride (BF3) with lithium oxalate (Li2C2O4) involves reacting BF3 with Li2C2O4 in an organic solvent, followed by purification through recrystallization and other steps to obtain LiODFB. The disadvantages of this method are that the reaction conditions are harsh, requiring a large amount of BF3 gas, resulting in poor operational safety, the presence of lithium tetrafluoroborate as a byproduct, and difficulty in controlling product purity.
[0005] The boron trifluoride diethyl ether (BF3·Et2O) reaction method with lithium oxalate: Boron trifluoride diethyl ether is used as the boron fluoride source and reacts with lithium oxalate in an organic solvent such as dimethyl carbonate (DMC). The resulting product, LiODFB, is then purified through recrystallization and other steps. The disadvantages of this method are high raw material costs and the generation of harmful gases during the reaction, making it environmentally unfriendly.
[0006] Lithium tetrafluoroborate reacting with oxalic acid: Lithium tetrafluoroborate is reacted with oxalic acid in an organic solvent, and then purified by recrystallization and other steps to obtain LiODFB. A disadvantage of this method is the need for a catalyst (such as silicon tetrachloride or trimethylchlorosilane).
[0007] These existing methods generally suffer from problems such as high raw material costs, harsh reaction conditions, complex steps, low yields, and environmental pollution, which limit the large-scale industrial production of LiODFB. Therefore, developing an efficient, environmentally friendly, and low-cost method for preparing LiODFB is of significant practical importance. Based on this, this application was developed. Summary of the Invention
[0008] The purpose of this invention is to overcome the defects of the prior art and provide an efficient method for preparing lithium difluorooxalate borate. This method prepares lithium difluorooxalate borate and aluminum fluoride by reacting lithium tetrafluoroborate with anhydrous aluminum oxalate (Al2(C2O4)3). It has the advantages of mild reaction conditions, simple operation, low raw material cost, high yield and environmental friendliness. It can overcome the shortcomings of the prior art and is suitable for large-scale industrial production.
[0009] To achieve the above-mentioned objectives and technical effects, the present invention is implemented through the following technical solution: A method for efficiently preparing lithium difluorooxalate borate involves adding lithium tetrafluoroborate and anhydrous aluminum oxalate to an organic solvent to form a homogeneous reaction system. The reaction system is then heated under an inert atmosphere. After the reaction is complete, the solid and liquid are separated, and the filtrate is concentrated under reduced pressure, crystallized, filtered, and dried to obtain lithium difluorooxalate borate crystals.
[0010] The anhydrous aluminum oxalate used in this invention has extremely low solubility in organic solvents. To ensure reaction efficiency and improve reaction effect, the anhydrous aluminum oxalate is in powder form and can be obtained by grinding or other methods.
[0011] Specifically, the molar ratio of lithium tetrafluoroborate to anhydrous aluminum oxalate can be 3:(1-1.2), preferably 3:1.
[0012] Specifically, the organic solvent includes, but is not limited to, one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), acetonitrile, tetrahydrofuran (THF), etc.
[0013] Furthermore, 300-800 mL of organic solvent can be added for every 1 mol of lithium tetrafluoroborate.
[0014] Specifically, during the heating reaction, the reaction can be carried out at 30-80℃ for 5-9 hours.
[0015] A further preferred method is to heat the reaction at 45-60℃ for 6-8 hours.
[0016] In the method of this invention, specifically, after solid-liquid separation, a solid product and a filtrate are obtained. The solid product is aluminum fluoride, and the filtrate is a solution containing lithium difluorooxalate borate.
[0017] Specifically, an antisolvent can be added to induce crystallization. The antisolvent includes, but is not limited to, one or more of n-hexane, cyclohexane, diethyl ether, and dichloromethane.
[0018] Furthermore, the drying process can specifically be: vacuum drying at 100-130℃ for 10-14 hours.
[0019] The reaction equation for the method of this invention is as follows: 3 LiBF4+ Al2(C2O4)3→ 3 LiBF2C2O4+ 2 AlF3↓ The above reaction is a metathesis reaction, carried out in an organic solvent. Al in anhydrous aluminum oxalate 3+ The in-situ catalytic effect promotes the breaking of the BF bond in lithium tetrafluoroborate, while its oxalate ion coordinates with the boron center to form a stable difluorooxoborate ion. Under appropriate conditions, lithium tetrafluoroborate and anhydrous aluminum oxalate undergo ion exchange, with the oxalate ion in aluminum oxalate exchanging with the fluoride ion in lithium tetrafluoroborate to form lithium difluorooxoborate and aluminum fluoride. Since aluminum fluoride has extremely low solubility in organic solvents, it precipitates out as a solid, while lithium difluorooxoborate dissolves in the organic solvent, thus achieving product separation.
[0020] Compared with the prior art, the advantages and beneficial effects of the method of the present invention are as follows: 1) Low raw material cost: The price of anhydrous aluminum oxalate used in this invention is lower than that of oxalic acid used in the traditional way, and no expensive catalyst is required, which reduces production costs.
[0021] 2) Environmentally friendly: This invention does not use toxic and harmful BF3 gas or highly corrosive reagents, and there are no harmful gas emissions during the reaction process, making it environmentally friendly.
[0022] 3) Byproducts can be recycled: The aluminum fluoride produced by the reaction is an important chemical raw material that can be recycled, which improves resource utilization and reduces production costs.
[0023] 4) High reaction efficiency: The reaction of this invention is a one-step synthesis, with simple steps, short reaction time, and the yield of LiODFB can reach more than 96.5% and the purity is more than 99.8%. Attached Figure Description
[0024] Figure 1 Lithium difluorooxalate borate prepared in Example 1 19F-NMR spectrum, test frequency: 400MHz, deuterated reagent: deuterated dimethyl sulfoxide. The figure shows that the fluorine chemical shift value of lithium difluorooxalate borate is -150.71ppm, and that of lithium tetrafluoroborate is -148.23ppm. Based on the NMR spectra, the purity of lithium difluorooxalate borate is calculated to be 99.8%. Figure 2 The lithium difluorooxalate borate prepared in Example 2 19 F-NMR spectrum, test frequency: 400MHz, deuterated reagent: deuterated dimethyl sulfoxide. The figure shows that the fluorine chemical shift value of lithium difluorooxalate borate is -150.72ppm, and that of lithium tetrafluoroborate is -148.23ppm. Based on the NMR spectra, the purity of lithium difluorooxalate borate is calculated to be 99.9%. Figure 3 Lithium difluorooxalate borate prepared in Example 3 19 F-NMR spectrum, test frequency: 400MHz, deuterated reagent: deuterated dimethyl sulfoxide. The figure shows that the fluorine chemical shift value of lithium difluorooxalate borate is -150.73ppm, and that of lithium tetrafluoroborate is -148.24ppm. Based on the NMR spectra, the purity of lithium difluorooxalate borate is calculated to be 99.9%. Figure 4 Lithium difluorooxalate borate prepared in Example 4 19 F-NMR spectrum, test frequency: 400MHz, deuterated reagent: deuterated dimethyl sulfoxide. The figure shows that the fluorine chemical shift value of lithium difluorooxalate borate is -150.70ppm, and that of lithium tetrafluoroborate is -148.21ppm. Based on the NMR spectra, the purity of lithium difluorooxalate borate is calculated to be 99.6%. Detailed Implementation
[0025] This invention provides a method for preparing lithium difluorooxalate borate, which can be used as an additive in battery electrolytes. Those skilled in the art can refer to the content of this document and appropriately modify the process parameters to achieve the same result. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and fall within the scope of this invention. The methods described in this invention have been described in detail through preferred embodiments. Those skilled in the art can obviously modify or appropriately change and combine the methods described herein without departing from the content, spirit, and scope of this invention to implement and apply the technology of this invention.
[0026] To further illustrate the present invention, the following describes in detail, with reference to embodiments, a method for efficiently preparing lithium difluorooxalate borate provided by the present invention.
[0027] In the following embodiments, all raw materials used are common commercially available products that can be directly purchased in the art or can be prepared according to conventional methods in the art. Operations not described in detail can be performed using conventional techniques in the art.
[0028] Example 1 A method for efficiently preparing lithium difluorooxalate borate includes the following steps: 93.74 g (1.0 mol) of lithium tetrafluoroborate, 106 g (0.33 mol) of anhydrous aluminum oxalate powder, and 700 mL of dimethyl carbonate were added to a 1000 mL jacketed reactor. Under nitrogen protection, the reaction system was heated to 60 °C and stirred for 7 hours. After the reaction was complete, the reaction mixture was filtered to obtain a white solid product and a filtrate. The white solid product was aluminum fluoride, and the filtrate contained lithium difluorooxalate borate. The filtrate was concentrated under reduced pressure to 1 / 3 of its original volume at 60 °C, cooled to room temperature, and then 500 mL of cyclohexane was added. The mixture was stirred at room temperature, and white crystals precipitated. These crystals were then filtered, and the resulting white crystals were dried under vacuum at 120 °C for 12 hours to obtain 140 g of LiODFB product, with a yield of 97.4%. The product obtained in Example 1 was then subjected to… 19 F-NMR analysis showed that the product had low impurity content and a purity of up to 99.8% (see F-NMR analysis). Figure 1 ).
[0029] Example 2 A method for efficiently preparing lithium difluorooxalate borate includes the following steps: 140.61 g (1.5 mol) of lithium tetrafluoroborate, 165.36 g (0.52 mol) of anhydrous aluminum oxalate powder, and 500 mL of diethyl carbonate were added to a 1000 mL jacketed reactor. Under nitrogen protection, the reaction system was heated to 60 °C and stirred for 8 hours. After the reaction was complete, the reaction mixture was filtered to obtain a white solid product and a filtrate. The white solid product was aluminum fluoride, and the filtrate contained lithium difluorooxalate borate. The filtrate was concentrated under reduced pressure to 1 / 3 of its original volume at 65 °C, cooled to room temperature, and then 700 mL of dichloromethane was added. The mixture was stirred at room temperature, and white crystals precipitated. After filtration, the white crystals were dried under vacuum at 120 °C for 12 hours to obtain 208 g of LiODFB product, with a yield of 96.5%. The product obtained in Example 2 was then subjected to further analysis. 19 F-NMR analysis showed that the product had low impurity content and a purity of up to 99.9% (see F-NMR analysis). Figure 2 ).
[0030] Example 3 Referring to Example 1, the difference is that the organic solvent dimethyl carbonate was replaced with acetonitrile. The LiODFB product was prepared in 97.1% yield and with a purity of 99.9% (see Example 1). Figure 3 ).
[0031] Example 4 Referring to Example 1, the difference is that the organic solvent dimethyl carbonate was replaced with tetrahydrofuran. The LiODFB product was prepared in 96.3% yield and with a purity of 99.6% (see Example 1). Figure 4 ).
[0032] Comparative Example 1 Referring to Example 1, the difference is that anhydrous aluminum oxalate is replaced with anhydrous oxalic acid, and the reaction system cannot produce lithium difluorooxalate borate. This is because anhydrous oxalic acid is a weak acid and is difficult to react with lithium tetrafluoroborate to form the more acidic hydrofluoric acid. A catalyst (such as silicon tetrachloride or trimethylchlorosilane) is required to synthesize lithium difluorooxalate borate.
[0033] Comparative Example 2 Referring to Example 1, the difference is that the amount of lithium tetrafluoroborate was changed to 123.74 g (1.32 mol), and the molar ratio of lithium tetrafluoroborate to anhydrous aluminum oxalate was 4:1. After the reaction, the lithium tetrafluoroborate in the system was not completely reacted, and the purity of the product was only 83%. Therefore, controlling the amount of raw materials is crucial to the purity of the product.
[0034] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for efficiently preparing lithium difluorooxalate borate, characterized in that, Lithium tetrafluoroborate and anhydrous aluminum oxalate were added to an organic solvent and heated under an inert atmosphere. After the reaction was completed, the solid and liquid were separated, and the filtrate was concentrated under reduced pressure, crystallized, filtered, and dried to obtain lithium difluorooxalate borate crystals.
2. The method for efficiently preparing lithium difluorooxalate borate as described in claim 1, characterized in that, The molar ratio of lithium tetrafluoroborate to anhydrous aluminum oxalate is 3:(1-1.2).
3. The method for efficiently preparing lithium difluorooxalate borate as described in claim 1, characterized in that, The organic solvent is one or more of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, acetonitrile, and tetrahydrofuran.
4. The method for efficiently preparing lithium difluorooxalatoborate as described in claim 3, characterized in that, For every 1 mol of lithium tetrafluoroborate, add 300-800 mL of organic solvent.
5. The method for efficiently preparing lithium difluorooxalate borate as described in claim 1, characterized in that, Heat the mixture at 30-80℃ for 5-9 hours.
6. The method for efficiently preparing lithium difluorooxalatoborate as described in claim 5, characterized in that, Heat the mixture at 45-60℃ for 6-8 hours.
7. The method for efficiently preparing lithium difluorooxalatoborate as described in claim 1, characterized in that, After solid-liquid separation, a solid product and a filtrate are obtained. The solid product is aluminum fluoride, and the filtrate is a solution containing lithium difluorooxalate borate.
8. The method for efficiently preparing lithium difluorooxalatoborate as described in claim 1, characterized in that, Crystallization is carried out by adding an antisolvent, wherein the antisolvent is one or more of n-hexane, cyclohexane, diethyl ether, and dichloromethane.
9. The method for efficiently preparing lithium difluorooxalate borate as described in claim 1, characterized in that, The drying process involves vacuum drying at 100-130℃ for 10-14 hours.