Lithium hexafluorophosphate concentrated solution, preparation method and application thereof
By using continuous reaction and multi-step processing, a high-purity lithium hexafluorophosphate concentrate was prepared, which solved the problems of difficult impurity removal and safety risks in the existing technology, and realized efficient and safe lithium hexafluorophosphate production, which is suitable for lithium-ion battery electrolytes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HANGZHOU WANLIDA NEW ENERGY TECH CO LTD
- Filing Date
- 2023-10-30
- Publication Date
- 2026-07-28
AI Technical Summary
Existing lithium hexafluorophosphate production processes suffer from problems such as difficulty in removing impurities, long process routes, high safety risks, and high equipment investment. In particular, they fail to effectively remove chloride ions and hydrogen fluoride, affecting product purity and safety.
A continuous reaction process was used to prepare lithium hexafluorophosphate concentrate. A precursor solution was generated by reacting lithium halide with phosphorus pentachloride in a solvent, followed by reaction with hydrogen fluoride. The solution was then degassed, filtered, concentrated, diluted, and deacidified with resin. Impurities were removed by degasing, filtration, concentration, and deacidification with resin to produce a high-purity lithium hexafluorophosphate concentrate.
The preparation of high-purity lithium hexafluorophosphate with low impurity content and high safety has been achieved. Byproducts can be recycled, reducing production costs. It is suitable for lithium-ion battery electrolytes and has battery performance comparable to that of crystallization processes.
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Figure CN117430140B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of batteries and relates to a lithium hexafluorophosphate concentrate, its preparation method and application. Background Technology
[0002] Lithium hexafluorophosphate (LiPF6) is an important electrolyte salt primarily used in the non-aqueous electrolytes of lithium-ion batteries. Therefore, it requires very high purity (typically no less than 99.5%). The content of impurities such as water, alkali metals, heavy metals, chloride ions, sulfate ions, or free acids must be strictly controlled; otherwise, it will cause increased internal resistance, rapid capacity decay, and shortened cycle life, ultimately affecting battery safety. Therefore, obtaining high-purity LiPF6 products with low levels of harmful impurities is of significant practical importance.
[0003] The existing mainstream lithium hexafluorophosphate production processes mainly employ the following two methods:
[0004] For example, CN105036100A first uses hydrogen fluoride to react with phosphorus pentachloride to produce phosphorus pentafluoride, and then reacts with lithium fluoride to produce lithium hexafluorophosphate solution, which is then crystallized to obtain crystalline lithium hexafluorophosphate.
[0005] For example, CN108640129A uses high-purity phosphorus pentafluoride gas to react with lithium fluoride suspended in a non-aqueous solvent to generate lithium hexafluorophosphate, and then removes impurities by crystallization to obtain lithium hexafluorophosphate crystals.
[0006] However, CN105036100A faces the problem that the directly generated phosphorus pentafluoride is highly reactive and easily reacts with non-aqueous carbonate solvents, producing polysaccharide impurities. Furthermore, neither CN105036100A nor CN108640129A considers methods for removing chloride ions and hydrogen fluoride, nor does it address the safety issues associated with using hydrogen fluoride. In particular, the hydrogen chloride impurities introduced during the phosphorus pentafluoride gas production process in CN105036100A cannot be completely removed, which also affects the quality of the lithium hexafluorophosphate concentrate. Additionally, both of these solutions require crystallization purification. Considering that lithium hexafluorophosphate needs to return to a dissolved state when used in the electrolyte, if the crystallization purification step can be avoided while maintaining the purity of lithium hexafluorophosphate in solution, a significant amount of processing steps can be eliminated, thereby reducing equipment investment and land use, and lowering time and price costs.
[0007] Therefore, a new solution needs to be developed to directly obtain lithium hexafluorophosphate solution products with high purity and low impurity content, so as to eliminate subsequent crystallization and purification processes and realize its direct application in lithium-ion batteries. Summary of the Invention
[0008] In view of the problems existing in the prior art, the purpose of this invention is to provide a lithium hexafluorophosphate concentrate, its preparation method, and its application. The preparation method involves reacting lithium halide with phosphorus pentachloride in a solvent, followed by a reaction with hydrogen fluoride to generate a lithium hexafluorophosphate solution. This solution is then subjected to degassing, filtration, concentration, dilution, and resin deacidification to obtain the lithium hexafluorophosphate concentrate. This invention utilizes a continuous reaction scheme to mitigate the risks associated with the use of hydrogen fluoride and improve yield. Degassing, filtration, concentration, dilution, and resin deacidification remove impurities. Furthermore, byproducts can be collected to obtain high-purity hydrogen chloride for export and high-purity hydrogen fluoride for reuse.
[0009] To achieve this objective, the present invention adopts the following technical solution:
[0010] In a first aspect, the present invention provides a method for preparing a lithium hexafluorophosphate concentrate, the method comprising:
[0011] Lithium halide and phosphorus pentachloride are reacted in a solvent to generate a precursor solution;
[0012] The precursor solution is reacted with hydrogen fluoride in a second reaction to generate a lithium hexafluorophosphate solution.
[0013] The lithium hexafluorophosphate solution was sequentially degassed, filtered, concentrated, diluted, and deacidified with resin to obtain a concentrated lithium hexafluorophosphate solution.
[0014] To address the problems of complex preparation methods, large footprint, difficult impurity removal, significant impact of insoluble matter, long process routes, and high safety risks in existing lithium hexafluorophosphate preparation technologies, this invention provides a method for preparing lithium hexafluorophosphate concentrate. This method utilizes continuous reaction to mitigate the safety risks associated with the use of hydrogen fluoride and improve yield. Degassing, filtration, concentration, dilution, and deacidification resin removal are all beneficial for removing impurities. Furthermore, byproducts can be collected to obtain high-purity hydrogen chloride for external sale and high-purity hydrogen fluoride for reuse, thereby reducing overall costs.
[0015] The preparation method described herein employs mild reaction conditions, resulting in a product with high purity (99.5%–99.6%) lithium hexafluorophosphate and low impurity content (chloride ions less than 20 ppm, hydrofluoric acid (as HF) less than 50 ppm, moisture (Karl Fischer method) less than 20 ppm, Hazen color less than 150, all metal ions (Fe, Pb, Na, K, Ca) less than 3 ppm, and insoluble matter less than 10 ppm). It can be directly used as a lithium battery electrolyte, exhibiting battery performance equivalent to or better than that obtained through commonly used lithium hexafluorophosphate crystallization and impurity removal processes. The prepared method utilizes inexpensive and readily available raw materials, boasts high yield, simple operation, high safety, and allows for complete recycling of byproducts. Its overall cost is significantly lower than that of products obtained through commonly used lithium hexafluorophosphate crystallization processes, enabling applications in 3C, electric vehicles, and energy storage fields.
[0016] The continuous reaction refers to the process where the precursor solution and hydrogen fluoride, especially pressurized hydrogen fluoride (liquid), are continuously fed into a continuous reactor, such as a tubular reactor, in a specific ratio. After mixing and reaction, the resulting lithium hexafluorophosphate solution undergoes degassing, filtration, concentration, dilution, and resin deacidification processes to obtain the final product. Compared to the traditional batch reaction process for lithium hexafluorophosphate crystallization, the continuous reaction process for producing concentrated lithium hexafluorophosphate solution provided by this invention can effectively increase production capacity and improve safety. It features innovative characteristics such as low equipment investment, high safety, enhanced performance, simple operation, low cost, and complete recycling of by-products, making it more suitable for large-scale industrial production.
[0017] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.
[0018] As a preferred embodiment of the present invention, the lithium halide includes lithium chloride and / or lithium fluoride.
[0019] Preferably, the water content of the lithium halide is <50ppm, for example, it can be 48ppm, 45ppm, 40ppm, 35ppm, 30ppm, 25ppm, 20ppm, 15ppm, 10ppm, 5ppm or 0ppm, etc., but is not limited to the listed values, and other unlisted values within the above range are also used.
[0020] Preferably, the molar ratio of lithium halide to phosphorus pentachloride is 1:(1 to 1.5), for example 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, 1:1.25, 1:1.3, 1:1.35, 1:1.4, 1:1.45 or 1:1.5, etc., but is not limited to the listed values. Other unlisted values within the above range are also used.
[0021] Preferably, the phosphorus pentachloride is a solid.
[0022] Preferably, the hydrogen fluoride is pressurized liquid hydrogen fluoride.
[0023] As a preferred embodiment of the present invention, when the lithium halide includes lithium chloride, the molar ratio of hydrogen fluoride to lithium chloride is (6-6.6):1, for example 6:1, 6.05:1, 6.1:1, 6.15:1, 6.2:1, 6.25:1, 6.3:1, 6.35:1, 6.4:1, 6.45:1, 6.5:1, 6.55:1, or 6.6:1, etc., but is not limited to the listed values. Other unlisted values within the above range are also applicable.
[0024] Preferably, when the lithium halide includes lithium fluoride, the molar ratio of lithium fluoride to hydrogen fluoride is (5-5.5):1, for example 5:1, 5.05:1, 5.1:1, 5.15:1, 5.2:1, 5.25:1, 5.3:1, 5.35:1, 5.4:1, 5.45:1 or 5.5:1, but is not limited to the listed values. Other unlisted values within the above range are also used.
[0025] As a preferred embodiment of the present invention, the solvent is a non-aqueous solvent.
[0026] Preferably, the water content of the non-aqueous solvent is <20ppm, for example, it can be 18ppm, 15ppm, 12ppm, 9ppm, 7ppm, 5ppm, 3ppm, 1ppm or 0ppm, etc., 0ppm and no water content, but it is not limited to the listed values. Other unlisted values within the above range are also used.
[0027] Preferably, the solvent comprises at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethyl acetate, dimethylformamide, ethylene glycol dimethyl ether, acetonitrile, and tetrahydrofuran. For example, it may be a combination of dimethyl carbonate and diethyl carbonate, a combination of methyl ethyl carbonate and ethyl acetate, a combination of dimethylformamide and ethylene glycol dimethyl ether, a combination of acetonitrile and tetrahydrofuran, a combination of diethyl carbonate and methyl ethyl carbonate, a combination of ethyl acetate and acetonitrile, a combination of dimethylformamide and dimethyl carbonate, a combination of dimethyl carbonate and ethylene glycol dimethyl ether, a combination of methyl ethyl carbonate and acetonitrile, or a combination of diethyl carbonate and tetrahydrofuran. However, it is not limited to the combinations listed above, and other unlisted combinations of the applicable substances described above are also applicable.
[0028] Preferably, the solvent is a mixture of at least two of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate, such as a combination of dimethyl carbonate and methyl ethyl carbonate, a combination of methyl ethyl carbonate and diethyl carbonate, or a combination of dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.
[0029] As a preferred embodiment of the present invention, the reaction temperature of lithium halide and phosphorus pentachloride in a solvent is 0 to 60°C, for example, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, and the reaction time is 4 to 8 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, or 8 hours, but it is not limited to the listed values. Other unlisted values within the above range are also applicable.
[0030] Preferably, the reaction temperature between the precursor solution and hydrogen fluoride is 0–60°C, for example 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, and the reaction time is 5–10 h, for example 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h, or 10 h, but it is not limited to the listed values. Other unlisted values within the above range are also used.
[0031] Preferably, the preparation method is carried out in the presence of an inert atmosphere.
[0032] Preferably, the inert atmosphere includes at least one of nitrogen, argon, or helium, for example, a combination of nitrogen and argon, a combination of nitrogen and helium, or a combination of argon and helium.
[0033] As a preferred embodiment of the present invention, the second reaction is carried out in a tubular reactor.
[0034] Preferably, the method further includes collecting the hydrogen chloride and / or hydrogen fluoride gas produced by the second reaction.
[0035] The second reaction produces byproducts, namely a mixed gas containing hydrogen chloride and hydrogen fluoride. The mixed gas is distilled to obtain high-purity hydrogen fluoride and hydrogen chloride products. The hydrogen fluoride product can be reused for reaction with the precursor solution, while the hydrogen chloride product is exported.
[0036] Preferably, the collection method includes pressurized distillation using a pressurized distillation column.
[0037] Preferably, the distillation column has 12 to 30 trays, a reflux ratio of 0.5 to 2, a top temperature of -65 to 20°C, and a top pressure of 0.8 to 3 MPa. Hydrogen fluoride is collected from the bottom of the column, and hydrogen chloride is collected from the top. However, the values are not limited to those listed, and other unlisted values within the above range are also used.
[0038] Preferably, the purity of both the hydrogen fluoride product and the hydrogen chloride product is >99.99%; however, it is not limited to the listed values, and other unlisted values within the above range are also used.
[0039] Preferably, the resulting hydrogen fluoride product is used to react with the precursor solution.
[0040] As a preferred technical solution of the present invention, the degassing is used to remove residual hydrogen fluoride and hydrogen chloride, and the degassing method includes degassing under reduced pressure.
[0041] Preferably, the pressure range for degassing is 0.5 to 10 kPa, such as 0.5 kPa, 1 kPa, 1.5 kPa, 2 kPa, 2.5 kPa, 3 kPa, 3.5 kPa, 4 kPa, 4.5 kPa, 5 kPa, 5.5 kPa, 6 kPa, 6.5 kPa, 7 kPa, 7.5 kPa, 8 kPa, 8.5 kPa, 9 kPa, 9.5 kPa, or 10 kPa, but it is not limited to the listed values. Other unlisted values within the above range are also applicable.
[0042] Preferably, the degassing temperature is 0 to 60°C, for example, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, but is not limited to the listed values. Other unlisted values within the above range are also used.
[0043] Preferably, the degassing time is 5 to 10 hours, such as 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, or 10 hours, but it is not limited to the listed values. Other unlisted values within the above range are also used.
[0044] As a preferred technical solution of the present invention, the filtration uses a fluorinated resin filter element with a pore size of 0.02 to 2.0 mm, such as 0.02 mm, 0.05 mm, 0.08 mm, 0.1 mm, 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1 mm, 1.2 mm, 1.4 mm, 1.8 mm, or 2 mm, but is not limited to the listed values. Other unlisted values within the above range are also used.
[0045] Preferably, the pore size of the fluorinated resin filter element is between 0.08 and 0.15 mm, such as 0.08 mm, 0.09 mm, 0.1 mm, 0.11 mm, 0.12 mm, 0.13 mm, 0.14 mm, or 0.15 mm, but is not limited to the listed values. Other unlisted values within the above range are also used.
[0046] Preferably, the fluorinated resin filter element is made of PTFE.
[0047] As a preferred embodiment of the present invention, the concentration method includes vacuum heating.
[0048] Preferably, the pressure of the pressure reduction heating is 0.5 to 10 kPa, such as 0.5 kPa, 1 kPa, 2 kPa, 3 kPa, 4 kPa, 5 kPa, 6 kPa, 7 kPa, 8 kPa, 9 kPa or 10 kPa, but is not limited to the listed values. Other unlisted values within the above range are also used.
[0049] Preferably, the temperature range of the reduced pressure heating is 30 to 60°C, such as 30°C, 34°C, 38°C, 42°C, 46°C, 50°C, 53°C, 57°C, or 60°C, but it is not limited to the listed values. Other unlisted values within the above range are also used.
[0050] Concentration can further remove residual impurities, especially hydrogen fluoride and hydrogen chloride.
[0051] As a preferred technical solution of the present invention, the dilution method includes adding a solvent to make the mass fraction of lithium hexafluorophosphate 25% to 35%, such as 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34% or 35%, etc., but is not limited to the listed values, and other unlisted values within the above range are also applicable.
[0052] Preferably, the mass fraction of lithium hexafluorophosphate in the obtained lithium hexafluorophosphate concentrate is 28% to 32%, such as 28%, 28.5%, 29%, 29.5%, 30%, 30.5%, 31%, 31.5% or 32%, but is not limited to the listed values. Other unlisted values within the above range are also used.
[0053] As a preferred embodiment of the present invention, the resin used for deacidification includes an alkaline resin.
[0054] This invention preferably uses an alkaline resin, characterized in that the moisture from the deacidification byproducts is retained in the resin structure and does not affect product performance. Deacidification using this resin can reduce acidity and harmful impurities such as chloride ions.
[0055] Preferably, the temperature for resin deacidification is 0–60°C, for example, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, or 60°C, and the time is 5–10 hours, for example, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours, 8 hours, 8.5 hours, 9 hours, 9.5 hours, or 10 hours, but it is not limited to the listed values. Other unlisted values within the above range are also applicable.
[0056] In a second aspect, the present invention provides a lithium hexafluorophosphate concentrate, which is obtained by the preparation method described in the first aspect;
[0057] Preferably, the lithium hexafluorophosphate concentrate has a lithium hexafluorophosphate purity of 99.5%–99.6%, and a chloride ion content of <20 ppm, for example, 18 ppm, 15 ppm, 12 ppm, 9 ppm, 7 ppm, 5 ppm, 3 ppm, 1 ppm, or 0 ppm. The HF acid content, determined by titration, is <50 ppm, for example, 48 ppm, 40 ppm, 35 ppm, 30 ppm, 25 ppm, 20 ppm, 15 ppm, 10 ppm, 5 ppm, 3 ppm, 1 ppm, or 0 ppm. The moisture content, determined by Karl Fischer titration, is <20 ppm, for example, 18 ppm. 15ppm, 12ppm, 9ppm, 7ppm, 5ppm, 3ppm, 1ppm or 0ppm, etc., except for lithium, the content of other metal ions is <3ppm, for example, it can be 3ppm, 2ppm or 1ppm, etc., Hazen color <150, for example, it can be 148, 140, 130, 120, 110, 700, 90, 80, 70, 60, 50, 40, 30, 20, 10 or 5, etc., the content of insoluble matter is <10ppm, for example, it can be 10ppm, 5ppm or 0ppm, etc., but it is not limited to the listed values, other unlisted values within the above range also apply.
[0058] The above-mentioned indicators are used as the qualification criteria for the lithium hexafluorophosphate concentrate product of the present invention.
[0059] Thirdly, the present invention provides an application of the lithium hexafluorophosphate concentrate described in the second aspect in lithium-ion batteries.
[0060] Compared with existing technical solutions, the present invention has at least the following beneficial effects:
[0061] To address the problems of complex preparation methods, large footprint, difficult impurity removal, long process routes, and high safety risks in existing technologies for preparing lithium hexafluorophosphate products, this invention provides a method for preparing lithium hexafluorophosphate concentrate. This method utilizes continuous reaction to mitigate the risks associated with the use of hydrogen fluoride and improve yield. Impurities are removed through degassing, filtration, concentration, dilution, and deacidification resin. Furthermore, byproducts can be collected to obtain high-purity hydrogen chloride for external sale and high-purity hydrogen fluoride for reuse, which helps reduce overall costs.
[0062] The preparation method described herein employs mild reaction conditions, resulting in a product with high purity (99.5%–99.6%) and low impurity content (chloride ions less than 20 ppm, hydrofluoric acid (as HF) less than 50 ppm, moisture (Karl Fischer method) less than 20 ppm, Hazen color less than 150, and all metal ions except lithium ions (Fe, Pb, Na, K, Ca) less than 3 ppm, and insoluble matter less than 10 ppm). It can be directly used as a lithium battery electrolyte, exhibiting battery performance equivalent to or better than that obtained from commonly used lithium hexafluorophosphate crystallization and impurity removal processes. The preparation method utilizes inexpensive and readily available raw materials, boasts high yield, simple operation, high safety, and allows for complete recycling of byproducts. Its cost is lower than that of products from commonly used lithium hexafluorophosphate crystallization processes, enabling applications in 3C, electric vehicles, and energy storage fields. Attached Figure Description
[0063] Figure 1 A comparison graph showing the capacity decay of batteries assembled with the lithium hexafluorophosphate concentrate obtained in Example 1 and the lithium hexafluorophosphate solution obtained in Control Group 1 at 60°C.
[0064] Figure 2 This is a schematic diagram of the continuous reaction process in the preparation method of Example 1. Detailed Implementation
[0065] The technical solution of the present invention will be further illustrated below through specific embodiments.
[0066] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.
[0067] Example 1
[0068] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate, the preparation method comprising:
[0069] In a 1000 mL three-necked flask, under nitrogen protection, 600 mL of methyl ethyl carbonate as solvent, lithium fluoride and phosphorus pentachloride were added, ensuring that the molar ratio of lithium fluoride to phosphorus pentachloride was 1:1.2. The mixture was stirred and the temperature was slowly increased to 60 °C for 6 hours to generate a lithium pentachlorophosphate solution.
[0070] like Figure 2As shown, after the reaction is complete, the lithium pentachlorophosphate solution and liquid hydrogen fluoride are introduced into a continuous reactor (tubular reactor) at the same temperature at a molar ratio of hydrogen fluoride to lithium fluoride of 5.2:1 until the reaction is complete. During the reaction, hydrogen chloride gas is generated and introduced into a pressurized distillation column for separation by pressurized distillation. The distillation column has 21 trays, a reflux ratio of 1.2, a top temperature of 5°C, and a top pressure of 1.8 MPa, yielding reusable hydrogen fluoride (mass ratio greater than 99.99%) and exportable hydrogen chloride (mass ratio greater than 99.99%).
[0071] After the reaction is complete, while maintaining the same temperature, the vacuum pump is turned on to slowly evacuate and degas the reaction flask. This process takes approximately 6 hours at a pressure of 5 kPa. The degassed lithium hexafluorophosphate solution is then filtered using a PTFE filter with a pore size of 0.08–0.15 mm. The pressure is controlled at 0.5–10 kPa and the temperature at 60°C for reduced pressure heating to concentrate the solution. The concentration is then adjusted using methyl ethyl carbonate as a solvent. Finally, the solution is deacidified using an alkaline resin at 60°C, and after precision filtration, a concentrated lithium hexafluorophosphate solution is obtained.
[0072] Example 2
[0073] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method maintains the molar ratio of lithium fluoride to phosphorus pentachloride at 1:1.2 and adjusts the molar ratio of hydrogen fluoride to lithium fluoride from 5.2:1 to 5.45:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0074] Example 3
[0075] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method maintains the molar ratio of lithium fluoride to phosphorus pentachloride at 1:1.2 and adjusts the molar ratio of hydrogen fluoride to lithium fluoride from 5.2:1 to 5.1:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0076] Example 4
[0077] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.05, and keeps the molar ratio of hydrogen fluoride to lithium fluoride at 5.2:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0078] Example 5
[0079] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.45, and keeps the molar ratio of hydrogen fluoride to lithium fluoride at 5.2:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0080] Example 6
[0081] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.45 and the molar ratio of hydrogen fluoride to lithium fluoride from 5.2:1 to 5.6:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0082] Example 7
[0083] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium fluoride to phosphorus pentachloride from 1:1.2 to 1:0.9, and keeps the molar ratio of hydrogen fluoride to lithium fluoride at 5.2:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0084] Example 8
[0085] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.6, and keeps the molar ratio of hydrogen fluoride to lithium fluoride at 5.2:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0086] Example 9
[0087] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate, the preparation method comprising:
[0088] In a 1000 mL three-necked flask, under nitrogen protection, 600 mL of methyl ethyl carbonate as solvent, along with lithium chloride and phosphorus pentachloride, were added, ensuring that the molar ratio of lithium chloride to phosphorus pentachloride was 1:1.1. The mixture was stirred and the temperature was slowly increased to 60 °C for 6 hours to generate a lithium hexachlorophosphate solution.
[0089] After the reaction is complete, the lithium hexachlorophosphate solution and liquid hydrogen fluoride are introduced into a continuous reactor at the same temperature at a molar ratio of hydrogen fluoride to lithium fluoride of 6.2:1 until the reaction is complete. During the reaction, hydrogen chloride gas is generated and introduced into a distillation column for separation by pressurized distillation. The distillation column has 21 trays, a reflux ratio of 1.2, a top temperature of 5°C, and a top pressure of 1.8 MPa, yielding reusable hydrogen fluoride (mass ratio greater than 99.99%) and exportable hydrogen chloride (mass ratio greater than 99.99%).
[0090] After the reaction is complete, while maintaining the same temperature, the vacuum pump is turned on to slowly evacuate and degas the reaction flask. This process takes approximately 6 hours at a pressure of 5 kPa. The degassed lithium hexafluorophosphate solution is then filtered using a PTFE filter with a pore size of 0.08–0.15 mm. The pressure is controlled at 0.5–10 kPa and the temperature at 60°C for reduced pressure heating to concentrate the solution. The concentration is then adjusted using methyl ethyl carbonate as a solvent. Finally, the solution is deacidified using an alkaline resin at 60°C, and after precision filtration, a concentrated lithium hexafluorophosphate solution is obtained.
[0091] Example 10
[0092] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.3, and keeps the molar ratio of hydrogen fluoride to lithium chloride at 6.2:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0093] Example 11
[0094] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.45, and keeps the molar ratio of hydrogen fluoride to lithium chloride at 6.2:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0095] Example 12
[0096] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.3 and the molar ratio of hydrogen fluoride to lithium chloride from 6.2:1 to 6.0:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0097] Example 13
[0098] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.15 and the molar ratio of hydrogen fluoride to lithium chloride from 6.2:1 to 6.5:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0099] Example 14
[0100] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.3 and the molar ratio of hydrogen fluoride to lithium chloride from 6.2:1 to 6.6:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0101] Example 15
[0102] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.62, and keeps the molar ratio of hydrogen fluoride to lithium chloride at 6.2:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0103] Example 16
[0104] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.3 and the molar ratio of hydrogen fluoride to lithium chloride from 6.2:1 to 6.8:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0105] Example 17
[0106] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.3 and the molar ratio of hydrogen fluoride to lithium chloride from 6.2:1 to 5.8:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0107] Example 18
[0108] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method uses dimethyl carbonate instead of ethyl methyl carbonate, and adjusts the molar ratio of lithium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.4, so that the molar ratio of hydrogen fluoride to lithium fluoride is maintained at 5.2:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0109] Example 19
[0110] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method uses dimethyl carbonate instead of ethyl methyl carbonate, and adjusts the molar ratio of lithium fluoride to phosphorus pentachloride from 1:1.2 to 1:1.3, and the molar ratio of hydrogen fluoride to lithium fluoride from 5.2:1 to 5.3:1. Except for the above, the other conditions are exactly the same as in Example 1.
[0111] Example 20
[0112] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method uses dimethyl carbonate instead of ethyl methyl carbonate, adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.3, and adjusts the molar ratio of hydrogen fluoride to lithium chloride from 6.2:1 to 6.3:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0113] Example 21
[0114] This embodiment provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method uses dimethyl carbonate instead of ethyl methyl carbonate, adjusts the molar ratio of lithium chloride to phosphorus pentachloride from 1:1.1 to 1:1.2, and adjusts the molar ratio of hydrogen fluoride to lithium chloride from 6.2:1 to 6.4:1. Except for the above, the other conditions are exactly the same as in Example 9.
[0115] Comparative Example 1
[0116] This comparative example provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method does not involve resin deacidification, and all other conditions are exactly the same as in Example 1.
[0117] Comparative Example 2
[0118] This comparative example provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method does not involve reduced pressure heating, i.e., no concentration is performed. Except for the above, the other conditions are exactly the same as in Example 1.
[0119] Comparative Example 3
[0120] This comparative example provides a method for preparing lithium hexafluorophosphate concentrate. The preparation method does not involve vacuum degassing, and all other conditions are exactly the same as in Example 1.
[0121] Control group 1
[0122] In this control group, the purchased lithium hexafluorophosphate crystals were dissolved in methyl ethyl carbonate to form a lithium hexafluorophosphate solution.
[0123] The purity, Hazen color, LiPF6 content, free acid, moisture and metal ion content of the lithium hexafluorophosphate concentrate products obtained in Examples 1-21 and Comparative Examples 1-3 were determined, and the product qualification was judged according to the product standards mentioned above. The results are recorded in Table 1.
[0124] Table 1
[0125]
[0126]
[0127] Lithium hexafluorophosphate electrolytes were prepared using the lithium hexafluorophosphate concentrate product from Example 1 and the lithium hexafluorophosphate solution from Control Group 1, respectively. The batches, types, and concentrations of other electrolyte raw materials were kept consistent. The resulting electrolytes were added to pouch cells with identical designs (including NMC ternary cathode, artificial graphite anode, separator, and other battery materials). Accelerated cycle life tests were conducted under the same test conditions (charging: CC-CV, 1C, 4.2V; discharging: CC, 1C; ambient temperature: 60℃).
[0128] Figure 1 The performance of batteries obtained by comparing the lithium hexafluorophosphate concentrate product of Application Example 1 with that obtained by commonly used lithium hexafluorophosphate crystals (control group) was compared. The results showed that the concentrate obtained by the present invention has excellent performance in all aspects, especially in terms of insoluble matter, which is lower than that of commercially available lithium hexafluorophosphate crystal solutions. Therefore, the resulting batteries have equivalent or better battery performance.
[0129] The present invention has been illustrated with detailed structural features through the above embodiments, but the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for selected components, additions of auxiliary components, and selection of specific methods all fall within the protection and disclosure scope of the present invention.
[0130] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
[0131] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.
[0132] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.
Claims
1. A method for preparing a lithium hexafluorophosphate concentrate, characterized in that, The preparation method includes: Lithium halide is reacted with phosphorus pentachloride in a solvent to generate a precursor solution; the lithium halide is lithium chloride or lithium fluoride. The precursor solution and hydrogen fluoride are continuously introduced into a tubular reactor to carry out a second reaction to generate a lithium hexafluorophosphate solution; the lithium hexafluorophosphate solution is then subjected to degassing, filtration, concentration, dilution and resin deacidification in sequence to obtain a concentrated lithium hexafluorophosphate solution. The molar ratio of lithium halide to phosphorus pentachloride is 1:(1.1~1.4); The preparation method further includes collecting the hydrogen chloride and hydrogen fluoride gases produced in the second reaction; The collection method is pressure distillation using a pressure distillation column; The distillation column has 21 trays, a reflux ratio of 1.2, a top temperature of 5°C, and a top pressure of 1.8 MPa. Hydrogen fluoride is collected from the bottom of the column, and hydrogen chloride is collected from the top. The purity of both the hydrogen fluoride and hydrogen chloride products is >99.99% by mass. The collected hydrogen fluoride gas is used to react with the precursor solution; When the lithium halide is lithium chloride, the molar ratio of hydrogen fluoride to lithium chloride is (6.2~6.5):1; when the lithium halide is lithium fluoride, the molar ratio of hydrogen fluoride to lithium fluoride is (5~5.5):
1. The solvent is a non-aqueous solvent; The preparation method is carried out under an inert atmosphere at 0~60℃; The degassing method is depressurization degassing; the pressure range of the depressurization degassing is 0.5~10kPa, and the temperature is 0~60℃. The filtration uses a fluorinated resin filter element with a pore size of 0.02~2.0mm; The concentration method is vacuum heating, wherein the pressure range of vacuum heating is 0.5~10 kPa and the temperature range is 30~60℃; The dilution method involves adding the same solvent as in the first reaction, so that the mass fraction of lithium hexafluorophosphate is 25% to 35%. The resin used for deacidification is an alkaline resin; The lithium hexafluorophosphate concentrate has a lithium hexafluorophosphate purity of 99.5%~99.6%, chloride ion content <20ppm, HF acid content <50ppm by titration, moisture content <20ppm by Karl Fischer method, and the content of other metal ions except lithium <3ppm. The Hazen color is <150, and the insoluble matter content is <10ppm.
2. The preparation method according to claim 1, characterized in that, The non-aqueous solvent includes any one or a mixture of at least two of ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate.