A method for preparing a lithium hexafluorophosphate concentrate
By combining low-temperature reaction, multi-stage filtration, and vacuum low-temperature concentration processes with modified metal ion adsorbents, the problem of high impurity content in lithium hexafluorophosphate concentrate was solved, resulting in improved product purity and stability, and reduced costs.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HANGZHOU WANLIDA NEW ENERGY TECH CO LTD
- Filing Date
- 2026-05-11
- Publication Date
- 2026-06-09
Smart Images
Figure CN122166801A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium hexafluorophosphate concentrate technology, and in particular to a method for preparing lithium hexafluorophosphate concentrate. Background Technology
[0002] Lithium hexafluorophosphate (LiPF6) is the most important electrolyte salt in lithium-ion battery electrolytes, and its performance directly affects the energy density, cycle life, and safety performance of lithium-ion batteries. LiPF6 concentrate, as an intermediate product for preparing high-purity solid LiPF6 or directly used in electrolyte preparation, is of paramount importance in terms of quality and concentration.
[0003] Chinese Patent CN103069638B: A method for manufacturing lithium hexafluorophosphate concentrate, which involves reacting phosphorus trichloride, chlorine and lithium chloride in a non-aqueous organic solvent, then reacting the reaction product generated in the solvent with hydrogen fluoride to generate lithium hexafluorophosphate, filtering the reaction product after it has reacted with hydrogen fluoride, and further degassing and concentrating the filtrate to obtain lithium hexafluorophosphate concentrate.
[0004] Chinese Patent CN117430140A: Provides a lithium hexafluorophosphate concentrate, its preparation method and application. The preparation method involves reacting lithium halide with phosphorus pentachloride in a solvent, then reacting it with hydrogen fluoride to generate a lithium hexafluorophosphate solution, followed by degassing, filtration, concentration, dilution and resin deacidification to obtain the lithium hexafluorophosphate concentrate.
[0005] Existing preparation methods typically employ high-temperature reactions or simple concentration processes, resulting in high impurity content in the product, particularly the difficulty in controlling metal ion and moisture content, which affects the performance of subsequent products. Furthermore, the prepared lithium hexafluorophosphate concentrate exhibits poor stability, easily decomposing or deteriorating during storage, thus limiting its application range. Summary of the Invention
[0006] To address the above problems, this invention provides a method for preparing lithium hexafluorophosphate concentrate, the operation steps of which are as follows, in parts by mass: S1 Raw Material Pretreatment: Mix 5-10 parts of anhydrous lithium fluoride and 80-120 parts of anhydrous hydrofluoric acid until completely dissolved, filter, and obtain a lithium fluoride-hydrofluoric acid mixture. S2 reaction preparation: The mixture is introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas is slowly introduced at -5~5℃ for 30-60 min. The reaction is then stirred for 60-120 min. S3 multi-stage filtration: Add 0.1-0.5 parts of modified metal ion adsorbent to the solution after reaction, stir and mix, then first pass it through a ceramic membrane filter to remove larger particulate impurities in the solution; then filter it through an ultrafiltration membrane filter to remove colloidal substances and some organic impurities in the solution, thereby improving the purity of the solution; S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate.
[0007] In some embodiments, the stirring speed of S1 is 200-300 r / min, and the stirring time is 30-60 min.
[0008] In some embodiments, the introduction rate of the S2 phosphorus pentafluoride gas is 0.5-2 L / min.
[0009] In some embodiments, the operating temperature of the S3 multi-stage filtration is 10-20℃, and the operating pressure is 0.2-0.4MPa.
[0010] In some embodiments, the pore size of the S3 ceramic membrane is 0.1-0.2 μm.
[0011] In some embodiments, the S3 ultrafiltration membrane has a molecular weight cutoff of 1000-3000 Da.
[0012] In some embodiments, the vacuum degree of the S4 concentration is 0.08-0.095 MPa, the temperature is 30-45°C, and the stirring speed is 150-250 r / min.
[0013] In some embodiments, the modified metal ion adsorbent is prepared as follows, according to parts by mass: According to the mass fractions, 100-150 parts of D001 macroporous sulfonic acid resin, 2000-2500 parts of dichloroethane, 0.8-2.5 parts of ethyl 3-(2-pyrrole)acrylate, 3-5 parts of photoinitiator Irkgacure184, 10-23 parts of vinyl sulfonyl chloride, and 0.3-0.6 parts of dibutyltin dilaurate are added to a dry reaction vessel and stirred and mixed under nitrogen protection. The reaction is first carried out at room temperature for 20-40 minutes under ultraviolet light irradiation at a wavelength of 254nm, and then the temperature is raised to 50-60℃ and the reaction is continued for 3-5 hours. After the reaction is completed, the mixture is filtered and dried to obtain the modified metal ion adsorbent.
[0014] I. Reaction Mechanism of Modified Metal Ion Adsorbents In the preparation of the modified metal ion adsorbent, D001 macroporous sulfonic acid resin undergoes swelling pretreatment to create sufficient space for subsequent grafting reactions. Nitrogen protection effectively avoids the risk of oxygen quenching the free radical reaction, ensuring the directional conduction of the reaction. Under 254nm ultraviolet light irradiation, the photoinitiator Irkgacure184 decomposes to generate active free radicals, successfully activating the resin skeleton and promoting the grafting of ethyl 3-(2-pyrrole)acrylate and vinyl sulfonyl chloride onto the resin surface via free radical copolymerization. Subsequently, dibutyltin dilaurate further catalyzes and enhances the stability of the grafted bonds, ultimately constructing a dual adsorption site structure with both sulfonic acid groups (-SO3H) and pyrrole rings (containing N atoms). The sulfonic acid groups can bind metal impurity ions through ion exchange, while the N atoms in the pyrrole rings can preferentially capture common metal impurities through specific coordination, while avoiding excessive adsorption of target lithium ions. This provides crucial structural support for subsequently improving the purity of lithium hexafluorophosphate concentrate and reducing impurity content.
[0015] II. Technical Effects Outstanding adsorption selectivity: The dual adsorption sites of the modified metal ion adsorbent can target common metal impurity ions in lithium hexafluorophosphate concentrate. Through the synergistic effect of ion exchange and specific coordination, it preferentially captures impurity ions while effectively avoiding the adsorption of target lithium ions, ensuring the effective retention of lithium hexafluorophosphate and helping to improve product purity.
[0016] High process adaptability: The timing of adding the modified metal ion adsorbent is highly compatible with multi-stage filtration processes (after ceramic membrane filtration and before ultrafiltration membrane filtration). At this point, the concentrate has already undergone preliminary impurity removal, and the adsorbent can fully react with the impurity ions. Subsequently, the adsorbent and concentrate can be separated by a conventional ultrafiltration membrane without modifying existing equipment, reducing process adjustment costs while ensuring stable purification performance.
[0017] Excellent product quality control: This invention, through the synergistic effect of low-temperature reaction control, multi-stage filtration and purification, and high-efficiency adsorbents, combined with vacuum low-temperature concentration process, can effectively suppress the generation and introduction of impurities during the reaction process, while stably controlling the retention rate of the target product, avoiding product quality instability due to process fluctuations, and ensuring the consistency of key indicators of lithium hexafluorophosphate concentrate. Attached Figure Description
[0018] Figure 1 It is the LiPF6 prepared in Example 1. 19 F nuclear magnetic resonance spectrum; Figure 2 It is the LiPF6 prepared in Example 1. 31 P nuclear magnetic resonance spectrum. Detailed Implementation
[0019] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description is provided in conjunction with embodiments and comparative examples: 1. Lithium hexafluorophosphate content: Detected using ion chromatography.
[0020] 2. Impurity ion (iron ion, sodium ion) content: Detected using inductively coupled plasma mass spectrometry.
[0021] Example 1 A method for preparing lithium hexafluorophosphate concentrate, comprising the following steps: S1 raw material pretreatment: 5 kg of anhydrous lithium fluoride and 80 kg of anhydrous hydrofluoric acid are stirred and mixed until completely dissolved, filtered, and a lithium fluoride-hydrofluoric acid mixture is obtained. S2 reaction preparation: The mixture was introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas was slowly introduced at -5℃ for 30 min, and the reaction was continued to be stirred for 60 min. S3 multi-stage filtration: Add 0.01 kg of modified metal ion adsorbent to the solution after reaction, stir and mix, then first pass it through a ceramic membrane filter to remove larger particulate impurities in the solution; then pass it through an ultrafiltration membrane filter to remove colloidal substances and some organic impurities in the solution, thereby improving the purity of the solution; S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate.
[0022] The stirring speed of S1 is 200 r / min, and the stirring time is 30 min.
[0023] The S2 phosphorus pentafluoride gas is introduced at a rate of 0.5 L / min.
[0024] The S3 filter operates at a temperature of 10°C and a pressure of 0.2 MPa.
[0025] The S3 ceramic membrane has a pore size of 0.2 μm.
[0026] The S3 ultrafiltration membrane has a molecular weight cutoff of 3000 Da.
[0027] The vacuum degree of the S4 vacuum concentration is 0.08 MPa, the temperature is 30℃, and the stirring speed is 150 r / min.
[0028] The preparation method of the modified metal ion adsorbent is as follows: 100g of D001 macroporous sulfonic acid resin (sodium type), 2000g of dichloroethane, 0.8g of ethyl 3-(2-pyrrole)acrylate (CAS: 2433-65-0), 3g of photoinitiator Irgacure184, 10g of vinyl sulfonyl chloride, and 0.3g of dibutyltin dilaurate were added to a dry reaction vessel and stirred and mixed under nitrogen protection. The mixture was first reacted at room temperature for 20 minutes under 254nm ultraviolet light irradiation, and then heated to 50℃ and reacted for another 3 hours. After the reaction was completed, the mixture was filtered and dried to obtain the modified metal ion adsorbent.
[0029] Example 2 A method for preparing lithium hexafluorophosphate concentrate, comprising the following steps: S1 raw material pretreatment: 6 kg of anhydrous lithium fluoride and 90 kg of anhydrous hydrofluoric acid are stirred and mixed until completely dissolved, filtered, and a lithium fluoride-hydrofluoric acid mixture is obtained. S2 reaction preparation: The mixture was introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas was slowly introduced at -2℃ for 40 min, and the reaction was continued to be stirred for 80 min. S3 multi-stage filtration: Add 0.02 kg of modified metal ion adsorbent to the solution after reaction, stir and mix, then first pass it through a ceramic membrane filter to remove larger particulate impurities in the solution; then pass it through an ultrafiltration membrane filter to remove colloidal substances and some organic impurities in the solution, thereby improving the purity of the solution; S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate.
[0030] The stirring speed of S1 is 250 r / min, and the stirring time is 40 min.
[0031] The rate at which the S2 phosphorus pentafluoride gas is introduced is 1 L / min.
[0032] The S3 filter operates at a temperature of 15°C and a pressure of 0.3 MPa.
[0033] The S3 ceramic membrane has a pore size of 0.2 μm.
[0034] The S3 ultrafiltration membrane has a molecular weight cutoff of 2000 Da.
[0035] The vacuum degree of the S4 vacuum concentration is 0.09 MPa, the temperature is 35℃, and the stirring speed is 200 r / min.
[0036] The preparation method of the modified metal ion adsorbent is as follows: 110g of D001 macroporous sulfonic acid resin (sodium type), 2100g of dichloroethane, 1.3g of ethyl 3-(2-pyrrole)acrylate (CAS: 2433-65-0), 4g of photoinitiator Irgacure184, 15g of vinyl sulfonyl chloride, and 0.4g of dibutyltin dilaurate were added to a dry reaction vessel and stirred and mixed under nitrogen protection. The mixture was first reacted at room temperature for 25 minutes under ultraviolet light irradiation at a wavelength of 254nm, and then the temperature was raised to 55℃ and the reaction was continued for 4 hours. After the reaction was completed, the mixture was filtered and dried to obtain the modified metal ion adsorbent.
[0037] Example 3 A method for preparing lithium hexafluorophosphate concentrate, comprising the following steps: S1 raw material pretreatment: 8 kg of anhydrous lithium fluoride and 110 kg of anhydrous hydrofluoric acid are stirred and mixed until completely dissolved, filtered, and a lithium fluoride-hydrofluoric acid mixture is obtained. S2 reaction preparation: The mixture is introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas is slowly introduced at 1°C for 50 min. The reaction is then stirred for 100 min. S3 multi-stage filtration: Add 0.04 kg of modified metal ion adsorbent to the solution after reaction, stir and mix, then first pass it through a ceramic membrane filter to remove larger particulate impurities in the solution; then pass it through an ultrafiltration membrane filter to remove colloidal substances and some organic impurities in the solution, thereby improving the purity of the solution. S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate.
[0038] The stirring speed of S1 is 250 r / min, and the stirring time is 50 min.
[0039] The S2 phosphorus pentafluoride gas is introduced at a rate of 1.5 L / min.
[0040] The S3 filter operates at a temperature of 15°C and a pressure of 0.3 MPa.
[0041] The S3 ceramic membrane has a pore size of 0.1 μm.
[0042] The S3 ultrafiltration membrane has a molecular weight cutoff of 2000 Da.
[0043] The vacuum degree of the S4 vacuum concentration is 0.09 MPa, the temperature is 40℃, and the stirring speed is 200 r / min.
[0044] The preparation method of the modified metal ion adsorbent is as follows: 140g of D001 macroporous sulfonic acid resin (sodium type), 2400g of dichloroethane, 2.1g of ethyl 3-(2-pyrrole)acrylate (CAS: 2433-65-0), 4g of photoinitiator Irgacure184, 20g of vinyl sulfonyl chloride, and 0.5g of dibutyltin dilaurate were added to a dry reaction vessel and stirred and mixed under nitrogen protection. The mixture was first reacted at room temperature for 35 minutes under 254nm ultraviolet light irradiation, and then the temperature was raised to 55℃ and the reaction was continued for 4 hours. After the reaction was completed, the mixture was filtered and dried to obtain the modified metal ion adsorbent.
[0045] Example 4 A method for preparing lithium hexafluorophosphate concentrate, comprising the following steps: S1 raw material pretreatment: 10 kg of anhydrous lithium fluoride and 120 kg of anhydrous hydrofluoric acid are stirred and mixed until completely dissolved, filtered, and a lithium fluoride-hydrofluoric acid mixture is obtained. S2 reaction preparation: The mixture was introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas was slowly introduced at 5°C for 60 min. The reaction was then stirred for 120 min. S3 multi-stage filtration: Add 0.05 kg of modified metal ion adsorbent to the solution after reaction, stir and mix, then first pass it through a ceramic membrane filter to remove larger particulate impurities in the solution; then pass it through an ultrafiltration membrane filter to remove colloidal substances and some organic impurities in the solution, thereby improving the purity of the solution. S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate.
[0046] The stirring speed of S1 is 300 r / min, and the stirring time is 60 min.
[0047] The rate at which the S2 phosphorus pentafluoride gas is introduced is 2 L / min.
[0048] The S3 filter operates at a temperature of 20°C and a pressure of 0.4 MPa.
[0049] The S3 ceramic membrane has a pore size of 0.1 μm.
[0050] The S3 ultrafiltration membrane has a molecular weight cutoff of 1000 Da.
[0051] The vacuum degree of the S4 vacuum concentration is 0.095 MPa, the temperature is 45℃, and the stirring speed is 250 r / min.
[0052] The preparation method of the modified metal ion adsorbent is as follows: 150g of D001 macroporous sulfonic acid resin (sodium type), 2500g of dichloroethane, 2.5g of ethyl 3-(2-pyrrole)acrylate (CAS: 2433-65-0), 5g of photoinitiator Irgacure184, 23g of vinyl sulfonyl chloride, and 0.6g of dibutyltin dilaurate were added to a dry reaction vessel and stirred and mixed under nitrogen protection. The mixture was first reacted at room temperature for 40 minutes under 254nm ultraviolet light irradiation, and then the temperature was raised to 60℃ and the reaction was continued for 5 hours. After the reaction was completed, the mixture was filtered and dried to obtain the modified metal ion adsorbent.
[0053] Comparative Example 1 A method for preparing lithium hexafluorophosphate concentrate, comprising the following steps: S1 raw material pretreatment: 5 kg of anhydrous lithium fluoride and 80 kg of anhydrous hydrofluoric acid are stirred and mixed until completely dissolved, filtered, and a lithium fluoride-hydrofluoric acid mixture is obtained. S2 reaction preparation: The mixture was introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas was slowly introduced at -5℃ for 30 min, and the reaction was continued to be stirred for 60 min. S3 multi-stage filtration: The reacted solution is first passed through a ceramic membrane filter to remove larger particulate impurities; then it is filtered through an ultrafiltration membrane filter to remove colloidal substances and some organic impurities, thereby improving the purity of the solution. S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate.
[0054] The stirring speed of S1 is 200 r / min, and the stirring time is 30 min.
[0055] The S2 phosphorus pentafluoride gas is introduced at a rate of 0.5 L / min.
[0056] The S3 filter operates at a temperature of 10°C and a pressure of 0.2 MPa.
[0057] The S3 ceramic membrane has a pore size of 0.2 μm.
[0058] The S3 ultrafiltration membrane has a molecular weight cutoff of 3000 Da.
[0059] The vacuum degree of the S4 vacuum concentration is 0.08 MPa, the temperature is 30℃, and the stirring speed is 150 r / min.
[0060] Comparative Example 2 A method for preparing lithium hexafluorophosphate concentrate, comprising the following steps: S1 raw material pretreatment: 5 kg of anhydrous lithium fluoride and 80 kg of anhydrous hydrofluoric acid are stirred and mixed until completely dissolved, filtered, and a lithium fluoride-hydrofluoric acid mixture is obtained. S2 reaction preparation: The mixture was introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas was slowly introduced at -5℃ for 30 min, and the reaction was continued to be stirred for 60 min. S3 multi-stage filtration: Add 0.01 kg of modified metal ion adsorbent to the solution after reaction, stir and mix, then first pass it through a ceramic membrane filter to remove larger particulate impurities in the solution; then pass it through an ultrafiltration membrane filter to remove colloidal substances and some organic impurities in the solution, thereby improving the purity of the solution; S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate.
[0061] The stirring speed of S1 is 200 r / min, and the stirring time is 30 min.
[0062] The S2 phosphorus pentafluoride gas is introduced at a rate of 0.5 L / min.
[0063] The S3 filter operates at a temperature of 10°C and a pressure of 0.2 MPa.
[0064] The S3 ceramic membrane has a pore size of 0.2 μm.
[0065] The S3 ultrafiltration membrane has a molecular weight cutoff of 3000 Da.
[0066] The vacuum degree of the S4 vacuum concentration is 0.08 MPa, the temperature is 30℃, and the stirring speed is 150 r / min.
[0067] The preparation method of the modified metal ion adsorbent is as follows: 100g of D001 macroporous sulfonic acid resin (sodium type), 2000g of dichloroethane, 3g of photoinitiator Irgacure184, 10g of vinyl sulfonyl chloride, and 0.3g of dibutyltin dilaurate were added to a dry reaction vessel and stirred and mixed under nitrogen protection. The mixture was first reacted at room temperature for 20 minutes under ultraviolet light with a wavelength of 254nm, and then the temperature was raised to 50℃ and the reaction was continued for 3 hours. After the reaction was completed, the mixture was filtered and dried to obtain the modified metal ion adsorbent.
[0068] Comparative Example 3 A method for preparing lithium hexafluorophosphate concentrate, comprising the following steps: S1 raw material pretreatment: 5 kg of anhydrous lithium fluoride and 80 kg of anhydrous hydrofluoric acid are stirred and mixed until completely dissolved, filtered, and a lithium fluoride-hydrofluoric acid mixture is obtained. S2 reaction preparation: The mixture was introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas was slowly introduced at -5℃ for 30 min, and the reaction was continued to be stirred for 60 min. S3 multi-stage filtration: Add 0.01 kg of modified metal ion adsorbent to the solution after reaction, stir and mix, then first pass it through a ceramic membrane filter to remove larger particulate impurities in the solution; then pass it through an ultrafiltration membrane filter to remove colloidal substances and some organic impurities in the solution, thereby improving the purity of the solution; S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate.
[0069] The stirring speed of S1 is 200 r / min, and the stirring time is 30 min.
[0070] The S2 phosphorus pentafluoride gas is introduced at a rate of 0.5 L / min.
[0071] The S3 filter operates at a temperature of 10°C and a pressure of 0.2 MPa.
[0072] The S3 ceramic membrane has a pore size of 0.2 μm.
[0073] The S3 ultrafiltration membrane has a molecular weight cutoff of 3000 Da.
[0074] The vacuum degree of the S4 vacuum concentration is 0.08 MPa, the temperature is 30℃, and the stirring speed is 150 r / min.
[0075] The preparation method of the modified metal ion adsorbent is as follows: 100g of D001 macroporous sulfonic acid resin (sodium type), 2000g of dichloroethane, 0.8g of ethyl 3-(2-pyrrole)acrylate (CAS: 2433-65-0), 3g of photoinitiator Irgacure184, and 10g of vinyl sulfonyl chloride were added to a dry reaction vessel and stirred and mixed under nitrogen protection. The mixture was first reacted at room temperature for 20 minutes under 254nm ultraviolet light irradiation, and then heated to 50℃ and continued to react for 3 hours. After the reaction was completed, the mixture was filtered and dried to obtain the modified metal ion adsorbent.
[0076] The test results of the examples and comparative examples are shown in Table 1.
[0077] Table 1
[0078] The data shows a significant difference in the quality of the lithium hexafluorophosphate concentrate between the examples and the comparative examples. Regarding the lithium hexafluorophosphate content, the examples generally outperformed the comparative examples, indicating that the preparation process of this invention (including raw material pretreatment, low-temperature reaction, adsorption purification, etc.) is more conducive to the enrichment and retention of the target product. In terms of impurity content such as iron and sodium ions, the examples were lower than the comparative examples, confirming the effectiveness of combining the modified metal ion adsorbent with the multi-stage filtration process, which can accurately reduce impurity ion levels. In summary, the preparation method of this invention can simultaneously improve the purity and control impurities of the lithium hexafluorophosphate concentrate, fully demonstrating the technical advantages and feasibility of this method.
[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.
Claims
1. A method for preparing lithium hexafluorophosphate concentrate, comprising the following steps, in parts by mass: S1 Raw Material Pretreatment: Mix 5-10 parts of anhydrous lithium fluoride and 80-120 parts of anhydrous hydrofluoric acid until completely dissolved, filter, and obtain a lithium fluoride-hydrofluoric acid mixture. S2 reaction preparation: The mixture is introduced into the reaction vessel. Under the protection of nitrogen, phosphorus pentafluoride gas is slowly introduced at -5~5℃ for 30-60 min. The reaction is then stirred for 60-120 min. S3 multi-stage filtration: Add 0.1-0.5 parts of modified metal ion adsorbent to the solution after reaction, stir and mix, then pass through a ceramic membrane filter, and then through an ultrafiltration membrane filter to improve the purity of the solution; S4 Vacuum Low-Temperature Concentration: The filtered solution is placed in a vacuum concentration device for concentration to obtain lithium hexafluorophosphate concentrate; The modified metal ion adsorbent is prepared by reacting D001 macroporous sulfonic acid resin, ethyl 3-(2-pyrrole) acrylate, photoinitiator Irkgacure184, ethylene sulfonyl chloride, and dibutyltin dilaurate under ultraviolet light.
2. The method for preparing a lithium hexafluorophosphate concentrate according to claim 1, characterized in that: The stirring speed of S1 is 200-300 r / min, and the stirring time is 30-60 min.
3. The method for preparing a lithium hexafluorophosphate concentrate according to claim 1, characterized in that: The S2 phosphorus pentafluoride gas is introduced at a rate of 0.5-2 L / min.
4. The method for preparing a lithium hexafluorophosphate concentrate according to claim 1, characterized in that: The operating temperature of the S3 multi-stage filter is 10-20℃, and the operating pressure is 0.2-0.4MPa.
5. The method for preparing a lithium hexafluorophosphate concentrate according to claim 1, characterized in that: The S3 ceramic membrane has a pore size of 0.1-0.2 μm.
6. The method for preparing a lithium hexafluorophosphate concentrate according to claim 1, characterized in that: The S3 ultrafiltration membrane has a molecular weight cutoff of 1000-3000 Da.
7. The method for preparing a lithium hexafluorophosphate concentrate according to claim 1, characterized in that: The vacuum degree of the S4 concentration is 0.08-0.095 MPa, the temperature is 30-45℃, and the stirring speed is 150-250 r / min.
8. The method for preparing a lithium hexafluorophosphate concentrate according to claim 1, characterized in that: The preparation method of the modified metal ion adsorbent is as follows: According to the mass fractions, 100-150 parts of D001 macroporous sulfonic acid resin, 2000-2500 parts of dichloroethane, 0.8-2.5 parts of ethyl 3-(2-pyrrole)acrylate, 3-5 parts of photoinitiator Irkgacure184, 10-23 parts of vinyl sulfonyl chloride, and 0.3-0.6 parts of dibutyltin dilaurate are added to a dry reaction vessel and stirred and mixed under nitrogen protection. The reaction is first carried out at room temperature for 20-40 minutes under ultraviolet light irradiation at a wavelength of 254nm, and then the temperature is raised to 50-60℃ and the reaction is continued for 3-5 hours. After the reaction is completed, the mixture is filtered and dried to obtain the modified metal ion adsorbent.