Lithium fluoride purification method, high-purity lithium fluoride, lithium hexafluorophosphate, electrolyte and device

Abstract

The invention provides a lithium fluoride purification method, high-purity lithium fluoride, lithium hexafluorophosphate, an electrolyte and a device, and the lithium fluoride purification method comprises the following steps: carrying out water washing treatment on lithium fluoride to be purified at 0-50 DEG C to obtain a mixed material comprising a first solid-phase product; carrying out ultrasonic treatment on the mixed material at 20-25kHz, and filtering to obtain a second solid-phase product; carrying out fluorination reaction on the second solid-phase product and electronic-grade anhydrous hydrofluoric acid to obtain a third liquid-phase product, carrying out ion exchange on the third liquid-phase product by using chelate resin at 0-80 DEG C, then cooling, evaporating, crystallizing and filtering to obtain a fourth solid-phase product; and carrying out cleaning treatment on the fourth solid-phase product by adopting inert gas at 150-250 DEG C to obtain the high-purity lithium fluoride. According to the high-purity lithium fluoride prepared by the purification method disclosed by the invention, the content of lithium carbonate and other impurities is low, and the performance and the stability of subsequent products are favorably improved.

Description

Technical Field

[0001] The present invention relates to the field of chemical raw material preparation, and more specifically to a lithium fluoride purification method, high-purity lithium fluoride, lithium hexafluorophosphate, an electrolyte and a device. Background Art

[0002] In the field of industrial production, lithium fluoride is highly valued due to its wide application in the preparation of lithium-ion battery electrolytes, special glass, ceramics and other high-tech materials.

[0003] However, in the process of preparing lithium fluoride through chemical reaction using lithium carbonate as raw material, due to the complexity of the production process, lithium carbonate and other impurities may remain, reducing the purity of lithium fluoride, thus posing a threat to the performance and stability of subsequent products.

[0004] In view of the above problems, the prior art urgently needs to develop a lithium carbonate and lithium fluoride with low impurity content. Summary of the invention

[0005] The present invention provides a method for purifying lithium fluoride. The method can prepare high-purity lithium fluoride with low contents of lithium carbonate and other impurities, and the method has the advantages of simple process, low equipment requirements, high production efficiency, etc.

[0006] The present invention provides high-purity lithium fluoride, which is prepared by the above-mentioned purification method, wherein the content of lithium carbonate and other impurities is low, which is conducive to the subsequent wide application of high-purity lithium fluoride.

[0007] The present invention provides a lithium fluorophosphate. Since the lithium fluorophosphate is prepared from the above-mentioned high-purity lithium fluoride, it helps to improve the conductivity and chemical stability of the electrolyte, reduce the possibility of decomposition and degradation, and thus prolong the service life of the battery.

[0008] The present invention provides an electrolyte, which includes the above-mentioned high-purity lithium fluoride and can enable the battery to present excellent electrochemical performance.

[0009] The invention provides a device, which can provide excellent preparation conditions for the purification of lithium fluoride and is conducive to the preparation of high-purity lithium fluoride with low content of lithium carbonate and other impurities.

[0010] The present invention provides a method for purifying lithium fluoride, which comprises the following steps:

[0011] 1) washing the lithium fluoride to be purified with water at 0-50° C. to obtain a mixed material including a first solid phase product;

[0012] 2) subjecting the mixed material to ultrasonic treatment at 20-25 kHz, and filtering to obtain a second solid phase product;

[0013] 3) causing the second solid phase product to undergo a fluorination reaction with electronic grade anhydrous hydrofluoric acid to obtain a third liquid phase product, subjecting the third liquid phase product to ion exchange using a chelating resin at 0-80° C., followed by cooling and evaporation crystallization, and filtering to obtain a fourth solid phase product;

[0014] 4) The fourth solid phase product is cleaned with an inert gas at 150-250° C. to obtain high-purity lithium fluoride.

[0015] The purification method as described above, wherein the water washing treatment comprises: slurrying the lithium fluoride to be purified with water;

[0016] Wherein, the mass ratio of the lithium fluoride to be purified to water is 1:10-30, the stirring rate of the pulping treatment is 30-200r / min, and the time is 0.1-5h.

[0017] The purification method as described above, wherein the ultrasonic treatment comprises:

[0018] The first solid phase product is subjected to ultrasonic treatment at 0-50° C. until the mass percentage of carbonate ions in the liquid phase of the first solid phase product is greater than 80 ppm, thereby obtaining a second solid phase product.

[0019] The purification method as described above, wherein the amount of the electronic grade anhydrous hydrofluoric acid added is 0.95-1.05 equivalents of the carbonate ion content in the second solid phase product;

[0020] And / or, the temperature of the fluorination treatment is 60-100° C. and the time is 0.2-20 min.

[0021] The purification method as described above, wherein the cleaning process comprises:

[0022] The fourth solid phase product is dried by inert gas pressure purging until the mass percentage of water in the fourth solid phase product is less than 10 ppm, thereby obtaining the high-purity lithium fluoride;

[0023] Wherein, the pressure of the inert gas is 0.2-0.4 MPa.

[0024] In the purification method as described above, the impurities in the lithium fluoride to be purified include, in terms of mass percentage or mass concentration, 0.5-1wt% lithium carbonate, 50-200ppm sodium fluoride, 50-200ppm potassium fluoride, 50-200ppm sodium carbonate, 50-200ppm potassium carbonate, 0.5-1wt% water, and ≤100ppm ethylenediaminetetraacetic acid.

[0025] The present invention also provides high-purity lithium fluoride, which is prepared by the above-mentioned lithium fluoride purification method, wherein the impurities in the high-purity lithium fluoride include, by mass concentration, lithium carbonate ≤50ppm, sodium fluoride ≤50ppm, potassium fluoride ≤50ppm, sodium carbonate ≤10ppm, potassium carbonate ≤10ppm, water ≤10ppm, and ethylenediaminetetraacetic acid ≤10ppm.

[0026] The high-purity lithium fluoride as described above, wherein the D50 of the high-purity lithium fluoride is ≤100 μm and the specific surface area is 300-1000 m 2 / g, porosity is 30-75%.

[0027] The present invention also provides lithium hexafluorophosphate, which is prepared from the above-mentioned high-purity lithium fluoride.

[0028] The present invention also provides an electrolyte, which comprises the lithium hexafluorophosphate as described above.

[0029] The present invention also provides a device for purifying lithium fluoride, which comprises a water washing unit, an ultrasonic treatment unit, a fluorination reaction unit, an ion exchange unit, an evaporation crystallization unit and a cleaning treatment unit which are sequentially connected in series through a pipeline.

[0030] The purification method of lithium fluoride provided by the present invention, the lithium fluoride to be purified is washed with water, and the impurities such as lithium carbonate wrapped inside and on the surface of the lithium fluoride are dissolved into the aqueous phase, and the physical separation of impurities such as lithium carbonate and lithium fluoride is preliminarily achieved, and then the mixed material including the first solid phase product is ultrasonically treated to further promote the dissolution of impurities such as lithium carbonate, and effectively strip the organic pollutants attached to the surface of lithium fluoride, and then the second solid phase product is fluorinated with hydrofluoric acid to convert lithium carbonate into lithium fluoride, and the lithium fluoride is ion exchanged with a chelating resin, and the temperature is reduced. Evaporation and crystallization further improves the purity of lithium fluoride and improves the utilization rate of raw materials, and the fourth solid phase product obtained is cleaned with a high-temperature inert gas to further remove the residues of organic pollutants on the surface and in the lattice of lithium fluoride, and finally obtains high-purity lithium fluoride. In addition, the preparation method is simple in process, easy to operate, has low equipment requirements and high production efficiency.

[0031] The high-purity lithium fluoride provided by the present invention has low contents of lithium carbonate and other impurities. When the high-purity lithium fluoride is used as a raw material to participate in the reaction, it can be used to prepare lithium hexafluorophosphate with higher purity, which helps to improve the conductivity and chemical stability of the electrolyte, reduce the possibility of decomposition and degradation, and thus extend the service life of the battery.

[0032] The lithium hexafluorophosphate provided by the present invention is prepared from the above-mentioned high-purity lithium fluoride, which helps to improve the conductivity and chemical stability of the electrolyte, thereby extending the service life of the battery.

[0033] The electrolyte provided by the present invention comprises the high-purity lithium fluoride as described above and can make the battery exhibit excellent electrochemical performance.

[0034] The device provided by the present invention can provide preparation conditions for the preparation of high-purity lithium fluoride, thereby realizing the preparation of high-purity lithium fluoride with low impurity content such as lithium carbonate. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0036] Figure 1 It is a schematic diagram of the device structure of a specific embodiment of the present invention. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The present invention provides a method for purifying lithium fluoride, comprising the following steps:

[0039] 1) washing the lithium fluoride to be purified with water at 0-50° C. to obtain a mixed material including a first solid phase product;

[0040] 2) subjecting the mixed material to ultrasonic treatment at 20-25 kHz, and filtering to obtain a second solid phase product;

[0041] 3) causing the second solid phase product to undergo a fluorination reaction with electronic grade anhydrous hydrofluoric acid to obtain a third liquid phase product, subjecting the third liquid phase product to ion exchange using a chelating resin at 0-80° C., followed by cooling and evaporation crystallization, and filtering to obtain a fourth solid phase product;

[0042] 4) The fourth solid phase product is cleaned with an inert gas at 150-250° C. to obtain high-purity lithium fluoride.

[0043] Specifically, in step 1), the lithium fluoride to be purified is washed with water at 0-50° C. to obtain a mixed material including a first solid phase product, wherein the first solid phase product is lithium fluoride.

[0044] The present invention does not limit the specific parameters of the water washing treatment, which can be selected according to actual needs.

[0045] Step 2), subjecting the mixed material to ultrasonic treatment at an ultrasonic frequency of 20-25 kHz, and filtering to obtain a second solid phase product.

[0046] The present invention does not limit the specific parameters of the ultrasonic treatment, which can be selected according to actual needs.

[0047] Step 3), electronic grade anhydrous hydrofluoric acid is mixed into the second solid phase product, so that the second solid phase product and the electronic grade anhydrous hydrofluoric acid undergo a fluorination reaction to obtain a third liquid phase product.

[0048] The present invention does not limit the amount of electronic grade anhydrous hydrofluoric acid added, and the amount can be selected according to actual needs.

[0049] The present invention does not limit the specific parameters of the fluorination reaction, which can be selected according to actual needs.

[0050] Step 4), using an inert gas to clean the fourth solid phase product to obtain high-purity lithium fluoride, wherein the temperature of the inert gas is 150-250°C.

[0051] The present invention does not limit the specific selection of the inert gas, and the inert gas may be selected according to actual needs, such as nitrogen, argon, etc.

[0052] The present invention does not limit the specific parameters of the cleaning process, which can be selected according to actual needs.

[0053] The present invention firstly washes the lithium fluoride to be purified with water, and uses the different solubility of water in lithium fluoride and lithium carbonate and other impurities to dissolve the lithium carbonate and other impurities wrapped inside and on the surface of the lithium fluoride into the water phase, thereby preliminarily achieving physical separation of the lithium carbonate and other impurities from the lithium fluoride. Subsequently, the mixed material containing the first solid phase product is subjected to ultrasonic treatment, and the strong cavitation effect and mechanical oscillation effect generated by the ultrasonic wave further promote the dissolution of impurities such as lithium carbonate, and effectively strip off the organic pollutants attached to the surface of the lithium fluoride. Then, hydrofluoric acid is used to perform a fluorination reaction on the second solid phase product to convert the lithium carbonate into lithium fluoride, and a chelating resin is used to perform ion exchange on the lithium fluoride. The temperature is reduced and evaporated and crystallized to further improve the purity of the lithium fluoride and improve the utilization rate of the raw materials, thereby obtaining a fourth solid phase product. Finally, a high-temperature inert gas is used to clean the fourth solid phase product to further remove the residues of organic pollutants on the surface of the lithium fluoride and in the crystal lattice, thereby finally obtaining high-purity lithium fluoride.

[0054] The present invention does not limit the specific impurity content of the lithium fluoride to be purified, which can be selected according to actual needs.

[0055] In some embodiments, step 1) removes soluble impurities after filtration: potassium fluoride, sodium fluoride, sodium carbonate, potassium carbonate, etc.;

[0056] Step 2) further removing soluble impurities after filtration: potassium fluoride, sodium fluoride, sodium carbonate, potassium carbonate, etc.;

[0057] Step 3) After filtering, ethylenediaminetetraacetic acid (EDTA), potassium fluoride, sodium fluoride, etc. are further removed.

[0058] In a specific embodiment, the water washing treatment includes: pulping the lithium fluoride to be purified with water; wherein the mass ratio of the lithium fluoride to be purified to water is 1:(10-30), for example, the mass ratio is 1:10, 1:12, 1:15, 1:18, 1:20, 1:22, 1:25, 1:27 or 1:30, and the stirring rate of the pulping treatment is 30-200r / min, for example, the stirring rate is 30r / min, 40r / min, 50r / min, 60r / min, 70r / min n, 80r / min, 90r / min, 100r / min, 110r / min, 120r / min, 130r / min, 140r / min, 150r / min, 160r / min, 170r / min, 180r / min, 190r / min or 200r / min, etc., and the time is 0.1-5h, for example, the time is 0.1h, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h or 5h, etc. When the lithium fluoride to be purified is slurried with water, the impurities such as lithium carbonate inside and on the surface of the lithium fluoride can be dissolved into the aqueous phase to a greater extent, reducing the residual amount of impurities on the surface and inside of the lithium fluoride, thereby further improving the purity of the lithium fluoride, which is beneficial to the subsequent preparation of high-purity products of high-purity lithium fluoride.

[0059] In a specific embodiment, the ultrasonic treatment includes: performing ultrasonic treatment on a mixture containing a first solid phase product at 0-50°C until the mass percentage of carbonate ions in the liquid phase of the mixture is greater than 80ppm, and filtering to obtain a second solid phase product. When the mixture is subjected to ultrasonic treatment at low temperature, the cavitation effect and mechanical oscillation of the ultrasonic wave can be utilized to a greater extent, so that impurities such as lithium carbonate are dissolved more into the aqueous phase, and organic pollutants can be stripped more effectively, thereby reducing the residual impurities on the surface and inside of lithium fluoride to a greater extent, making the purity of high-purity lithium fluoride greater, and laying the foundation for the subsequent application of high-purity lithium fluoride.

[0060] In a specific embodiment, the amount of electronic grade anhydrous hydrofluoric acid added is 0.95-1.05 equivalents of the carbonate ion content in the second solid phase product; and / or, the temperature of the fluorination treatment is 60-100°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C, etc., and the time is 0.2-20min, such as 0.2min, 1min, 2min, 4min, 6min, 8min, 10min, 12min, 14min, 16min, 18min or 20min, etc. The 0.95-1.05 equivalents of the carbonate ion content of the present invention refers to 0.95-1.05 times the molar ratio of the chemical reaction between hydrofluoric acid and carbonate ions, that is, the molar ratio of hydrofluoric acid to carbonate ions in the second solid phase product is 1.9-2.1. When the parameters of the fluorination treatment are respectively within the above ranges, the lithium carbonate in the second solid phase product can be fully converted into lithium fluoride, thereby reducing the content of lithium carbonate in the second solid phase product, further improving the purity of lithium fluoride, and further improving the raw material conversion rate of lithium fluoride to be purified, thereby reducing production costs.

[0061] In a specific embodiment, the cleaning treatment includes: drying the fourth solid phase product by pressurized purge with inert gas until the mass percentage of water in the fourth solid phase product is less than 10 ppm, so as to obtain high-purity lithium fluoride; wherein the pressure of the inert gas is 0.2-0.4 MPa, for example, the pressure is 0.21 MPa, 0.22 MPa, 0.23 MPa, 0.24 MPa, 0.25 MPa, 0.26 MPa, 0.27 MPa, 0.28 MPa, 0.29 MPa, 0.3 MPa, 0.31 MPa, 0.32 MPa, 0.33 MPa, 0.34 MPa, 0.35 MPa, 0.36 MPa, 0.37 MPa, 0.38 MPa, 0.39 MPa or 0.4 MPa, etc. When the fourth solid phase product is subjected to a pressurized purging and drying treatment using an inert gas, the high-temperature inert gas and the volatility of organic matter under high-temperature conditions can be utilized to deeply remove organic pollutants on the surface and in the crystal lattice of lithium fluoride, thereby further reducing the content of impurities in high-purity lithium fluoride, and at the same time being able to quickly remove the water phase in the fourth solid phase product, thereby achieving the preparation of high-purity lithium fluoride with high specific surface area, high porosity and small particle size.

[0062] In a specific embodiment, the impurities in the lithium fluoride to be purified include, by mass percentage or mass concentration, 0.5-1wt% lithium carbonate, 50-200ppm sodium fluoride, 50-200ppm potassium fluoride, 50-200ppm sodium carbonate, 50-200ppm potassium carbonate, 0.5-1wt% water, and 100ppm ethylenediaminetetraacetic acid. When the mass percentages of the impurities in the lithium fluoride to be purified are respectively within the above ranges, the content of impurities such as lithium carbonate in the lithium fluoride to be purified is low, so that the impurity content introduced during the preparation process is avoided to be too high, which is conducive to the preparation of high-purity lithium fluoride.

[0063] The present invention also provides high-purity lithium fluoride, which is obtained by the above purification method. The impurities in the high-purity lithium fluoride, measured by mass concentration, include: lithium carbonate ≤50ppm, sodium fluoride ≤50ppm, potassium fluoride ≤50ppm, sodium carbonate ≤10ppm, potassium carbonate ≤10ppm, water ≤10ppm, and ethylenediaminetetraacetic acid ≤10ppm.

[0064] Specifically, the mass percentage of impurities in the high-purity lithium fluoride of the present invention can be obtained through ion chromatography testing.

[0065] The high-purity lithium fluoride of the present invention has low lithium carbonate content and other impurities, which is conducive to the subsequent application of high-purity lithium fluoride. The inventor analyzed the reason and believed that the reason may be that when the lithium carbonate and other impurities in lithium fluoride are low, when high-purity lithium fluoride is used as a raw material to participate in the reaction, high-purity lithium hexafluorophosphate can be prepared, and when the high-purity lithium hexafluorophosphate is used in the electrolyte, the conductivity of the electrolyte can be improved, thereby improving the overall performance of the lithium-ion battery, including energy density, power density and cycle life, and can avoid the reaction of lithium carbonate with acidic substances in the electrolyte to cause the battery performance to decrease, which is conducive to the wide application of high-purity lithium fluoride.

[0066] In some embodiments, the impurities in high-purity lithium fluoride include, by mass concentration, 25-41 ppm lithium carbonate, 10-45 ppm sodium fluoride, 10-47 ppm potassium fluoride, 5-9 ppm sodium carbonate, 5-9 ppm potassium carbonate, 5-8 ppm water, and 5-9 ppm ethylenediaminetetraacetic acid.

[0067] In a specific embodiment, the D50 of high-purity lithium fluoride is ≤100 μm, for example, D50 is 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm or 99 μm, etc., and the specific surface area is 300-1000 m 2 / g, for example, the specific surface area is 300m 2 / g, 350m 2 / g, 400m 2 / g, 450m 2 / g、500m 2 / g, 550m 2 / g、600m 2 / g, 650m 2 / g、700m 2 / g, 750m 2 / g、800m 2 / g, 850m 2 / g、900m 2 / g, 950m 2 / g or 1000m 2 / g, etc., and the porosity is 30-75%, for example, the porosity is 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70% or 75%, etc. When the particle size, specific surface area and porosity of high-purity lithium fluoride are respectively within the above ranges, when lithium fluoride is used as a raw material to participate in the reaction, lithium fluoride can react quickly with other reaction raw materials before lithium carbonate, thereby preventing impurities generated after the reaction of lithium carbonate with other reaction raw materials from adhering to the surface of unreacted lithium fluoride, so that the final product forms a coating relationship with the impurities, resulting in the problem that the final product prepared with the lithium fluoride is difficult to extract and has insufficient performance.

[0068] Specifically, the D50 of the high-purity lithium fluoride of the present invention can be obtained by a laser particle size analyzer test, the specific surface area can be obtained by a BET test, and the porosity can be obtained by a gas replacement method test.

[0069] The present invention also provides lithium hexafluorophosphate, which is prepared from the above-mentioned high-purity lithium fluoride.

[0070] In a specific embodiment, high-purity lithium fluoride is put into a reaction kettle, anhydrous hydrogen fluoride is added for stirring and dissolution, and after the dissolution is completed, PF5 gas is directly introduced into the kettle, the temperature is controlled to be -20 to 20°C, and the pressure is within 0 to 2Mpa. The reaction solution is then cooled and crystallized, filtered and dried to obtain lithium hexafluorophosphate.

[0071] In a specific embodiment, the temperature of the stirring and dissolving is -10 to 10°C, the pressure is normal pressure, and the stirring time is 1 to 3 hours; the molar ratio of PF5 introduced to LIF is 1.01 to 1.1 (eq).

[0072] In a specific embodiment, the method further comprises using ICP to detect the metal content of lithium hexafluorophosphate, using filter drying and weighing method to detect the insoluble matter content, and using IC to test the lithium hexafluorophosphate content.

[0073] The present invention also provides an electrolyte, comprising the lithium hexafluorophosphate as described above. The present invention does not limit the selection of the organic solvent in the electrolyte and whether to add additives, which can be selected according to actual needs.

[0074] The electrolyte provided by the present invention has a low content of impurities such as lithium carbonate, which can avoid the side reactions caused by the impurities leading to a decrease in battery performance, thereby making the battery exhibit excellent electrochemical performance.

[0075] The present invention also provides a device for purifying lithium fluoride, such as Figure 1 As shown, the device includes a water washing unit, an ultrasonic treatment unit, a fluorination reaction unit, an ion exchange unit, an evaporation crystallization unit and a cleaning treatment unit which are sequentially connected in series through pipelines.

[0076] The water washing unit of the present invention is used for slurrying the lithium fluoride to be purified with water to obtain a mixed material containing a first solid phase product; the ultrasonic treatment unit is used for ultrasonically treating the mixed material including the first solid phase product and water, filtering to obtain a second solid phase product; the fluorination reaction unit is used for fluorination reaction of the second solid phase product with hydrofluoric acid to obtain a third liquid phase product, the ion exchange unit is used for ion exchange of the third liquid phase product, the evaporation crystallization unit is used for cooling evaporation crystallization to obtain a fourth solid phase product; the cleaning treatment unit is used for high-temperature inert gas purging and drying treatment of the fourth solid phase product; wherein the outlet of the water washing unit is connected to the inlet of the ultrasonic treatment unit, that is, the first solid phase product generated in the water washing unit is exported from the outlet of the water washing unit and introduced from the inlet of the ultrasonic treatment unit; the outlet of the ultrasonic treatment unit is connected to the inlet of the fluorination reaction unit The two units are connected, i.e., the second solid phase product generated in the ultrasonic treatment unit is led out from the outlet of the ultrasonic treatment unit and introduced into the inlet of the fluorination reaction unit; the outlet of the fluorination reaction unit is connected with the inlet of the ion exchange unit, i.e., the third liquid phase product generated in the fluorination reaction unit is led out from the outlet of the fluorination reaction unit and introduced into the inlet of the ion exchange unit; the outlet of the ion exchange unit is connected with the inlet of the evaporation crystallization unit, i.e., the third liquid phase product of the ion exchange unit after ion exchange is led out from the outlet of the ion exchange unit and introduced into the inlet of the evaporation crystallization unit; the outlet of the evaporation crystallization unit is connected with the inlet of the cleaning treatment unit, i.e., the fourth solid phase product generated in the fluorination reaction unit is led out from the outlet of the evaporation crystallization unit and introduced into the inlet of the cleaning treatment unit; finally, a high-temperature inert gas purging and drying treatment is performed in the cleaning treatment unit to obtain high-purity lithium fluoride.

[0077] Hereinafter, the present invention will be further described in detail through specific examples.

[0078] Example 1

[0079] The preparation process of lithium fluoride provided in this embodiment comprises the following steps:

[0080] 1. Mixing the lithium fluoride to be purified with water at 20° C. and performing a slurry treatment to obtain a mixed material including a first solid phase product;

[0081] The impurities in the lithium fluoride to be purified include, by mass percentage, 0.8% lithium carbonate, 100 ppm sodium fluoride, 100 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 0.8% water, and 100 ppm ethylenediaminetetraacetic acid (EDTA);

[0082] The mass ratio of the lithium fluoride to be purified to water is 1:20, and the stirring rate of the pulping treatment is 80 r / min, and the time is 3 h;

[0083] 2. The mixed material is subjected to ultrasonic treatment at 20° C. and 24 kHz until the mass percentage of carbonate ions in the liquid phase of the mixed material is 85 ppm, and a second solid phase product is obtained by filtration;

[0084] 3. Fluorination reaction of the second solid phase product with electronic grade anhydrous hydrofluoric acid to obtain a third liquid phase product, ion exchange of the third liquid phase product with a chelating resin at 30° C., cooling to 20° C., evaporation and crystallization followed by filtration to obtain a fourth solid phase product;

[0085] Wherein, the amount of hydrofluoric acid added is 1 equivalent of the carbonate ion content in the second solid phase product;

[0086] The temperature of fluorination treatment was 80°C and the time was 15 min;

[0087] 4. Using nitrogen to perform high-pressure purging and drying treatment on the fourth solid phase product until the mass percentage of water in the fourth solid phase product is 9 ppm, thereby obtaining high-purity lithium fluoride;

[0088] The temperature of the nitrogen is 200°C and the pressure of the nitrogen is 0.3 MPa.

[0089] According to the tests of ion chromatography (Ic) and Karl Fischer tester, the impurities in high-purity lithium fluoride include, by mass concentration, 30 ppm lithium carbonate, 10 ppm sodium fluoride, 10 ppm potassium fluoride, 5 ppm sodium carbonate, 5 ppm potassium carbonate, 9 ppm EDTA, and 8 ppm water.

[0090] According to the laser particle size analyzer test, the D50 of high-purity lithium fluoride is 80μm; according to the BET test, the specific surface area of ​​high-purity lithium fluoride is 800m 2 / g; According to the test of the porosity tester, the porosity of high-purity lithium fluoride is 65%.

[0091] The preparation process of lithium fluoride provided in Example 2-35 is substantially the same as that in Example 1, and the specific parameters are shown in Table 1. The test results of high-purity lithium fluoride of Example 2-35 are shown in Table 2.

[0092] Table 1

[0093]

[0094]

[0095] Table 2

[0096]

[0097]

[0098]

[0099] The preparation process of lithium fluoride provided in Examples 36-39 is substantially the same as that in Example 1, and the specific parameters are shown in Table 3. The test results of high-purity lithium fluoride of Examples 36-39 are shown in Table 4.

[0100] Table 3

[0101]

[0102] Table 4

[0103]

[0104] Comparative Example 1

[0105] The preparation process of lithium fluoride provided in this comparative example comprises the following steps:

[0106] 1. Perform ultrasonic treatment on the mixture of lithium fluoride to be purified and water at 20°C and 24kHz until the mass percentage of carbonate ions in the liquid phase of the mixed system is 85ppm, and filter to obtain a first solid phase product;

[0107] The impurities in the lithium fluoride to be purified include, by mass percentage, 0.8% lithium carbonate, 100 ppm sodium fluoride, 100 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 0.8% water, and 100 ppm ethylenediaminetetraacetic acid (EDTA);

[0108] 2. Fluorination reaction is performed on the first solid phase product with electronic grade anhydrous hydrofluoric acid to obtain a fluorinated mixture, and the fluorinated mixture is filtered to obtain a second solid phase product with a moisture content of 20%;

[0109] Wherein, the amount of hydrofluoric acid added is 1 equivalent of the carbonate ion content in the first solid phase product;

[0110] The temperature of fluorination treatment was 80°C and the time was 15 min;

[0111] 3. Using nitrogen to perform high-pressure purging and drying treatment on the second solid phase product until the mass percentage of water in the second solid phase product is 9 ppm, thereby obtaining high-purity lithium fluoride;

[0112] The temperature of the nitrogen is 200°C and the pressure of the nitrogen is 0.3 MPa.

[0113] According to ion chromatography (Ic) and Karl Fischer tester tests, the impurities in high-purity lithium fluoride include, by mass percentage, 61 ppm lithium carbonate, 51 ppm sodium fluoride, 71 ppm potassium fluoride, 12 ppm sodium carbonate, 15 ppm potassium carbonate, 15 ppm EDTA, and 10 ppm water.

[0114] According to the laser particle size analyzer test, the D50 of high-purity lithium fluoride is 132μm; according to the BET test, the specific surface area of ​​high-purity lithium fluoride is 345m 2 / g; According to the test of the porosity tester, the porosity of high-purity lithium fluoride is 29%.

[0115] Comparative Example 2

[0116] The preparation process of lithium fluoride provided in this comparative example comprises the following steps:

[0117] 1. At 20° C., mix the lithium fluoride to be purified with water, perform pulping treatment, and filter to obtain a first solid phase product;

[0118] The impurities in the lithium fluoride to be purified include, by mass percentage, 0.8% lithium carbonate, 100 ppm sodium fluoride, 100 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 0.8% water, and 100 ppm ethylenediaminetetraacetic acid (EDTA);

[0119] The mass ratio of the lithium fluoride to be purified to water is 1:20, and the stirring rate of the pulping treatment is 80 r / min, and the time is 3 h;

[0120] 2. Fluorination reaction is performed on the first solid phase product with electronic grade anhydrous hydrofluoric acid to obtain a fluorinated mixture, and the fluorinated mixture is filtered to obtain a second solid phase product with a moisture content of 20%;

[0121] Wherein, the amount of hydrofluoric acid added is 1 equivalent of the carbonate ion content in the first solid phase product;

[0122] The temperature of fluorination treatment was 80°C and the time was 15 min;

[0123] 3. Using nitrogen to perform high-pressure purging and drying treatment on the second solid phase product until the mass percentage of water in the second solid phase product is 9 ppm, thereby obtaining high-purity lithium fluoride;

[0124] The temperature of the nitrogen is 200°C and the pressure of the nitrogen is 0.3 MPa.

[0125] According to ion chromatography (Ic) and Karl Fischer tester tests, the impurities in high-purity lithium fluoride include, by mass percentage, 55 ppm lithium carbonate, 42 ppm sodium fluoride, 58 ppm potassium fluoride, 51 ppm sodium carbonate, 53 ppm potassium carbonate, 13 ppm EDTA, and 15 ppm water.

[0126] According to the laser particle size analyzer test, the D50 of high-purity lithium fluoride is 156μm; according to the BET test, the specific surface area of ​​high-purity lithium fluoride is 275m 2 / g; According to the test of the porosity tester, the porosity of high-purity lithium fluoride is 28%.

[0127] Comparative Example 3

[0128] The preparation process of lithium fluoride provided in this comparative example comprises the following steps:

[0129] 1. Mixing the lithium fluoride to be purified with water at 20° C. and performing a slurry treatment to obtain a mixed material including a first solid phase product;

[0130] The impurities in the lithium fluoride to be purified include, by mass percentage, 0.8% lithium carbonate, 100 ppm sodium fluoride, 100 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 0.8% water, and 100 ppm ethylenediaminetetraacetic acid (EDTA);

[0131] The mass ratio of the lithium fluoride to be purified to water is 1:20, and the stirring rate of the pulping treatment is 80 r / min, and the time is 3 h;

[0132] 2. The mixed material was subjected to ultrasonic treatment at 20° C. and 24 kHz until the mass percentage of carbonate ions in the liquid phase of the first solid phase product was 85 ppm, and the second solid phase product was obtained by filtration;

[0133] 3. Using nitrogen to perform high-pressure purging and drying treatment on the second solid phase product until the mass percentage of water in the second solid phase product is 9 ppm, thereby obtaining high-purity lithium fluoride;

[0134] The temperature of the nitrogen is 200°C and the pressure of the nitrogen is 0.3 MPa.

[0135] According to ion chromatography (Ic) and Karl Fischer tester tests, the impurities in high-purity lithium fluoride include, by mass percentage, 6500 ppm lithium carbonate, 10 ppm sodium fluoride, 10 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 9 ppm EDTA, and 8 ppm water.

[0136] According to the laser particle size analyzer test, the D50 of high-purity lithium fluoride is 110μm; according to the BET test, the specific surface area of ​​high-purity lithium fluoride is 277m 2 / g; According to the test of the porosity tester, the porosity of high-purity lithium fluoride is 27%.

[0137] Comparative Example 4

[0138] The preparation process of lithium fluoride provided in this comparative example comprises the following steps:

[0139] 1. Mixing the lithium fluoride to be purified with water at 20° C. and performing a slurry treatment to obtain a mixed material containing a first solid phase product;

[0140] The impurities in the lithium fluoride to be purified include, by mass percentage, 0.8% lithium carbonate, 100 ppm sodium fluoride, 100 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 0.8% water, and 100 ppm ethylenediaminetetraacetic acid (EDTA);

[0141] The mass ratio of the lithium fluoride to be purified to water is 1:20, and the stirring rate of the pulping treatment is 80 r / min, and the time is 3 h;

[0142] 2. The mixed material is subjected to ultrasonic treatment at 20° C. and 24 kHz until the mass percentage of carbonate ions in the liquid phase of the mixed material is 85 ppm, and a second solid phase product is obtained by filtration;

[0143] 3. Fluorination reaction of the second solid phase product with electronic grade anhydrous hydrofluoric acid to obtain a third liquid phase product, ion exchange of the third liquid phase product with a chelating resin at 30° C., cooling to 20° C., evaporation and crystallization thereof, and then filtration to obtain a fourth solid phase product;

[0144] Wherein, the amount of hydrofluoric acid added is 1 equivalent of the carbonate ion content in the second solid phase product;

[0145] The temperature of fluorination treatment was 80°C and the time was 15 min;

[0146] 4. The fourth solid phase product is dried at a temperature of 60° C. until the mass percentage of water in the fourth solid phase product is 9 ppm, thereby obtaining high-purity lithium fluoride.

[0147] According to ion chromatography (Ic) and Karl Fischer tester tests, the impurities in high-purity lithium fluoride include, by mass percentage, 120 ppm lithium carbonate, 15 ppm sodium fluoride, 14 ppm potassium fluoride, 52 ppm sodium carbonate, 54 ppm potassium carbonate, 29 ppm EDTA, and 15 ppm water.

[0148] According to the laser particle size analyzer test, the D50 of high-purity lithium fluoride is 187μm; according to the BET test, the specific surface area of ​​high-purity lithium fluoride is 245m 2 / g; According to the test of the porosity tester, the porosity of high-purity lithium fluoride is 25%.

[0149] Comparative Example 5

[0150] The preparation process of lithium fluoride provided in this comparative example comprises the following steps:

[0151] 1. Mixing the lithium fluoride to be purified with water at 60° C. and performing a slurry treatment to obtain a mixed material containing a first solid phase product;

[0152] The impurities in the lithium fluoride to be purified include, by mass percentage, 0.8% lithium carbonate, 100 ppm sodium fluoride, 100 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 0.8% water, and 100 ppm ethylenediaminetetraacetic acid (EDTA);

[0153] The mass ratio of the lithium fluoride to be purified to water is 1:20, and the stirring rate of the pulping treatment is 80 r / min, and the time is 3 h;

[0154] 2. The mixed material is subjected to ultrasonic treatment at 20° C. and 24 kHz until the mass percentage of carbonate ions in the liquid phase of the mixed material is 85 ppm, and a second solid phase product is obtained by filtration;

[0155] 3. Fluorination reaction of the second solid phase product with electronic grade anhydrous hydrofluoric acid to obtain a third liquid phase product, ion exchange of the third liquid phase product with a chelating resin at 30° C., cooling to 20° C., evaporation and crystallization thereof, and then filtration to obtain a fourth solid phase product;

[0156] Wherein, the amount of hydrofluoric acid added is 1 equivalent of the carbonate ion content in the second solid phase product;

[0157] The temperature of fluorination treatment was 80°C and the time was 15 min;

[0158] 4. Using nitrogen to perform high-pressure purging and drying treatment on the fourth solid phase product until the mass percentage of water in the fourth solid phase product is 9 ppm, thereby obtaining high-purity lithium fluoride;

[0159] The temperature of the nitrogen is 200°C and the pressure of the nitrogen is 0.3 MPa.

[0160] According to ion chromatography (Ic) and Karl Fischer tester tests, the impurities in high-purity lithium fluoride include, by mass percentage, 67 ppm lithium carbonate, 61 ppm sodium fluoride, 51 ppm potassium fluoride, 55 ppm sodium carbonate, 51 ppm potassium carbonate, 9 ppm EDTA, and 8 ppm water.

[0161] According to the laser particle size analyzer test, the D50 of high-purity lithium fluoride is 117μm; according to the BET test, the specific surface area of ​​high-purity lithium fluoride is 256m 2 / g; According to the test of the porosity tester, the porosity of high-purity lithium fluoride is 28%.

[0162] Comparative Example 6

[0163] The preparation process of lithium fluoride provided in this comparative example comprises the following steps:

[0164] 1. Mixing the lithium fluoride to be purified with water at 20° C. and performing a slurry treatment to obtain a mixed material containing a first solid phase product;

[0165] The impurities in the lithium fluoride to be purified include, by mass percentage, 0.8% lithium carbonate, 100 ppm sodium fluoride, 100 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 0.8% water, and 100 ppm ethylenediaminetetraacetic acid (EDTA);

[0166] The mass ratio of the lithium fluoride to be purified to water is 1:20, and the stirring rate of the pulping treatment is 80 r / min, and the time is 3 h;

[0167] 2. The mixed material is subjected to ultrasonic treatment at 20° C. and 15 kHz until the mass percentage of carbonate ions in the liquid phase of the mixed material is 85 ppm, and a second solid phase product is obtained by filtration;

[0168] 3. Fluorination reaction of the second solid phase product with electronic grade anhydrous hydrofluoric acid to obtain a third liquid phase product, ion exchange of the third liquid phase product with a chelating resin at 30° C., cooling to 20° C., evaporation and crystallization thereof, and then filtration to obtain a fourth solid phase product;

[0169] Wherein, the amount of hydrofluoric acid added is 1 equivalent of the carbonate ion content in the second solid phase product;

[0170] The temperature of fluorination treatment was 80°C and the time was 15 min;

[0171] 4. Using nitrogen to perform high-pressure purging and drying treatment on the fourth solid phase product until the mass percentage of water in the fourth solid phase product is 9 ppm, thereby obtaining high-purity lithium fluoride;

[0172] The temperature of the nitrogen is 200°C and the pressure of the nitrogen is 0.3 MPa.

[0173] According to ion chromatography (Ic) and Karl Fischer tester tests, the impurities in high-purity lithium fluoride include, by mass percentage, 58 ppm lithium carbonate, 41 ppm sodium fluoride, 55 ppm potassium fluoride, 50 ppm sodium carbonate, 13 ppm potassium carbonate, 13 ppm EDTA, and 10 ppm water.

[0174] According to the laser particle size analyzer test, the D50 of high-purity lithium fluoride is 115μm; according to the BET test, the specific surface area of ​​high-purity lithium fluoride is 394m 2 / g; According to the test of the porosity tester, the porosity of high-purity lithium fluoride is 29%.

[0175] Comparative Example 7

[0176] The preparation process of lithium fluoride provided in this comparative example comprises the following steps:

[0177] 1. Mixing the lithium fluoride to be purified with water at 20° C. and performing a slurry treatment to obtain a mixed material containing a first solid phase product;

[0178] The impurities in the lithium fluoride to be purified include, by mass percentage, 0.8% lithium carbonate, 100 ppm sodium fluoride, 100 ppm potassium fluoride, 100 ppm sodium carbonate, 100 ppm potassium carbonate, 0.8% water, and 100 ppm ethylenediaminetetraacetic acid (EDTA);

[0179] The mass ratio of the lithium fluoride to be purified to water is 1:20, and the stirring rate of the pulping treatment is 80 r / min, and the time is 3 h;

[0180] 2. The mixed material is subjected to ultrasonic treatment at 20° C. and 24 kHz until the mass percentage of carbonate ions in the liquid phase of the mixed material is 85 ppm, thereby obtaining a second solid phase product;

[0181] 3. Fluorination reaction of the second solid phase product with electronic grade anhydrous hydrofluoric acid to obtain a third liquid phase product, ion exchange of the third liquid phase product with a chelating resin at 30° C., cooling to 20° C., evaporation and crystallization thereof, and then filtration to obtain a fourth solid phase product;

[0182] Wherein, the amount of hydrofluoric acid added is 1 equivalent of the carbonate ion content in the second solid phase product;

[0183] The temperature of fluorination treatment was 80°C and the time was 15 min;

[0184] 4. Using nitrogen to perform high-pressure purging and drying treatment on the fourth solid phase product until the mass percentage of water in the fourth solid phase product is 9 ppm, thereby obtaining high-purity lithium fluoride;

[0185] The temperature of the nitrogen is 300°C and the pressure of the nitrogen is 0.3 MPa.

[0186] According to ion chromatography (Ic) and Karl Fischer tester tests, the impurities in high-purity lithium fluoride include, by mass percentage, 30 ppm lithium carbonate, 10 ppm sodium fluoride, 10 ppm potassium fluoride, 5 ppm sodium carbonate, 5 ppm potassium carbonate, 9 ppm EDTA, and 8 ppm water.

[0187] According to the laser particle size analyzer test, the D50 of high-purity lithium fluoride is 20μm; according to the BET test, the specific surface area of ​​high-purity lithium fluoride is 1350m 2 / g; According to the test of the porosity tester, the porosity of high-purity lithium fluoride is 85%.

[0188] In summary, according to the comparison between Example 1 and Comparative Example 1, it can be seen that the residual amount of impurities on the surface and inside of lithium fluoride can be reduced by water washing treatment, and the purity of lithium fluoride can be improved; according to the comparison between Example 1 and Comparative Example 2, it can be seen that ultrasonic treatment can effectively strip impurities on the surface and inside of lithium fluoride, so that the purity of high-purity lithium fluoride is greater; according to the comparison between Example 1 and Comparative Example 3, it can be seen that fluorination treatment can fully convert residual lithium carbonate into lithium fluoride, thereby improving the purity of lithium fluoride; according to the comparison between Example 1 and Comparative Example 4, it can be seen that cleaning treatment can deeply remove impurities on the surface and in the crystal lattice of lithium fluoride, and can quickly take away the water phase, so as to achieve the preparation of high-purity lithium fluoride with high specific surface area, high porosity and small particle size; according to Examples 1-3 and From the comparison of comparative example 5, it can be seen that the water washing treatment at 0-50°C can dissolve the impurities such as lithium carbonate wrapped inside and on the surface of lithium fluoride into the aqueous phase, realize the physical separation of impurities such as lithium carbonate from lithium fluoride, and improve the purity of lithium fluoride; from the comparison of Examples 1, 12, 13 and Comparative Example 6, it can be seen that at an ultrasonic frequency of 20-25kHz, the strong cavitation effect and mechanical oscillation effect generated by the ultrasonic wave can better promote the dissolution of impurities such as lithium carbonate, thereby improving the purity of lithium fluoride; from the comparison of Examples 1, 29-31 and Comparative Example 7, it can be seen that the use of an inert gas at 150-250°C for cleaning treatment can obtain high-purity lithium fluoride with a suitable specific surface area and porosity, which is beneficial to the subsequent application of high-purity lithium fluoride.

[0189] According to the comparison of Examples 1-7, when the mass ratio of the lithium fluoride to be purified to water is in the range of 1: (10-30) during the pulping treatment, it is beneficial to improve the purity of the lithium fluoride; according to the comparison of Examples 1 and 7-11, when the stirring speed and stirring time of the pulping treatment are in the range of 30-200r / min and 0.1-5h, respectively, the purity of the high-purity lithium fluoride can be improved; according to the comparison of Examples 1 and 14-17, when the temperature of the ultrasonic treatment is in the range of 0-50°C until the mass percentage of carbonate ions in the liquid phase is greater than 80ppm, the purity of the high-purity lithium fluoride can be further improved; according to the comparison of Examples 1 and 18-21, when the amount of hydrofluoric acid added in the fluorination reaction is 0.95-1.05 equivalents of the carbonate ion content in the second solid phase product, the purity of the high-purity lithium fluoride can be further improved. , lithium carbonate can be fully converted into lithium fluoride, which is beneficial to the improvement of the purity of high-purity lithium fluoride; according to the comparison of Examples 1, 22-25, it can be seen that when the temperature of the fluorination treatment is 60-100°C and the time is 0.2-20min, the lithium carbonate can fully undergo fluorination reaction and reduce the content of impurities in the high-purity lithium fluoride; according to the comparison of Example 1, when an inert gas with a pressure of 0.2-0.4MPa is used for purging until the mass percentage of water in the fourth solid phase product is less than 10ppm, the specific surface area and porosity of the high-purity lithium fluoride are higher; according to the comparison of Examples 1, 36-39, it can be seen that when the impurities in the lithium fluoride to be purified are within the above range, the content of impurities such as lithium carbonate in the lithium fluoride to be purified is low, avoiding excessive impurity content introduced during the preparation process, and making the prepared high-purity lithium fluoride have high purity.

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for purifying lithium fluoride, characterized in that: The following steps are involved: 1) washing the lithium fluoride to be purified with water at 0-50° C. to obtain a mixed material including a first solid phase product; 2) subjecting the mixed material to ultrasonic treatment at 20-25 kHz, and filtering to obtain a second solid phase product; 3) causing the second solid phase product to undergo a fluorination reaction with electronic grade anhydrous hydrofluoric acid to obtain a third liquid phase product, subjecting the third liquid phase product to ion exchange using a chelating resin at 0-80° C., followed by cooling and evaporation crystallization, and filtering to obtain a fourth solid phase product; 4) The fourth solid phase product is cleaned with an inert gas at 150-250° C. to obtain high-purity lithium fluoride.

2. The method for purifying lithium fluoride according to claim 1, characterized in that: The water washing treatment comprises: slurrying the lithium fluoride to be purified with water; Wherein, the mass ratio of the lithium fluoride to be purified to water is 1:10-30, the stirring rate of the pulping treatment is 30-200r / min, and the time is 0.1-5h.

3. The method for purifying lithium fluoride according to claim 1 or 2, characterized in that: The ultrasonic treatment comprises: The first solid phase product is subjected to ultrasonic treatment at 0-50° C. until the mass percentage of carbonate ions in the liquid phase of the first solid phase product is greater than 80 ppm, thereby obtaining the second solid phase product.

4. The method for preparing lithium fluoride according to any one of claims 1 to 3, characterized in that: The amount of the electronic grade anhydrous hydrofluoric acid added is 0.95-1.05 equivalents of the carbonate ion content in the second solid phase product; And / or, the temperature of the fluorination treatment is 60-100° C. and the time is 0.2-20 min.

5. The method for purifying lithium fluoride according to any one of claims 1 to 4, characterized in that: The cleaning process comprises: The fourth solid phase product is dried by inert gas pressure purging until the mass percentage of water in the fourth solid phase product is less than 10 ppm, thereby obtaining the high-purity lithium fluoride; Wherein, the pressure of the inert gas is 0.2-0.4 MPa.

6. The method for purifying lithium fluoride according to any one of claims 1 to 5, characterized in that: The impurities in the lithium fluoride to be purified include, in terms of mass percentage or mass concentration, 0.5-1wt% lithium carbonate, 50-200ppm sodium fluoride, 50-200ppm potassium fluoride, 50-200ppm sodium carbonate, 50-200ppm potassium carbonate, 0.5-1wt% water, and ≤100ppm ethylenediaminetetraacetic acid.

7. A high-purity lithium fluoride, characterized in that: Prepared by the lithium fluoride purification method according to any one of claims 1 to 6; The impurities in the high-purity lithium fluoride include, by mass concentration, lithium carbonate ≤50ppm, sodium fluoride ≤50ppm, potassium fluoride ≤50ppm, sodium carbonate ≤10ppm, potassium carbonate ≤10ppm, water ≤10ppm, and ethylenediaminetetraacetic acid ≤10ppm.

8. The high-purity lithium fluoride according to claim 7, characterized in that: The D50 of the high-purity lithium fluoride is ≤100 μm, and the specific surface area is 300-1000 m 2 / g, porosity is 30-75%.

9. A lithium hexafluorophosphate, characterized in that: Prepared from the high-purity lithium fluoride described in claim 7 or 8.

10. An electrolyte, characterized in that: Including the lithium hexafluorophosphate as described in claim 9.

11. A device for purifying lithium fluoride, characterized in that: The invention comprises a water washing unit, an ultrasonic treatment unit, a fluorination reaction unit, an ion exchange unit, an evaporation crystallization unit and a cleaning treatment unit which are connected in series in sequence through pipelines.

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