A method for purifying lithium fluoride, high-purity lithium fluoride, lithium hexafluorophosphate, an electrolyte, and a device

Abstract

The application provides a purification method of lithium fluoride, high-purity lithium fluoride, lithium hexafluorophosphate, an electrolyte and a device, and the purification method of the lithium fluoride comprises the following steps: performing water washing treatment on the lithium fluoride to be purified at 0-50 DEG C to obtain a mixture containing a first solid-phase product; performing ultrasonic treatment on the mixture at 20-25 kHz to obtain a second solid-phase product through filtration; performing fluorination reaction on the second solid-phase product with electronic-grade anhydrous hydrofluoric acid to obtain a third liquid-phase product; performing ion exchange on the third liquid-phase product by using a chelating resin at 0-80 DEG C, and then performing cooling evaporation crystallization, and obtaining a fourth solid-phase product through filtration; and performing cleaning treatment on the fourth solid-phase product by using inert gas at 150-250 DEG C to obtain high-purity lithium fluoride. The high-purity lithium fluoride obtained by the purification method has low content of lithium carbonate and other impurities, and is beneficial to improving the performance and stability of subsequent products.

Description

Technical Field

[0001] This invention relates to the field of chemical raw material preparation, and more specifically to a method for purifying lithium fluoride, high-purity lithium fluoride, lithium hexafluorophosphate, electrolyte, and apparatus. Background Technology

[0002] In the industrial production sector, lithium fluoride is highly valued for its wide application in the preparation of lithium-ion battery electrolytes, specialty glasses, ceramics, and other high-tech materials.

[0003] However, in the process of preparing lithium fluoride from lithium carbonate through a chemical reaction, the complexity of the production process may lead to the residue of lithium carbonate and other impurities, which reduces the purity of lithium fluoride and thus threatens the performance and stability of subsequent products.

[0004] In view of the above problems, there is an urgent need to develop a lithium fluoride with low content of lithium carbonate and other impurities. Summary of the Invention

[0005] This invention provides a method for purifying lithium fluoride, which can produce high-purity lithium fluoride with low content of lithium carbonate and other impurities. This method has the advantages of simple process, low equipment requirements and high production efficiency.

[0006] This invention provides a high-purity lithium fluoride, which is obtained by the above-mentioned purification method. The lithium fluoride has low content of lithium carbonate and other impurities, which is beneficial to the subsequent wide application of high-purity lithium fluoride.

[0007] This invention provides a lithium fluorophosphate, which is prepared from the above-mentioned high-purity lithium fluoride. Therefore, it helps to improve the conductivity and chemical stability of the electrolyte, reduce the possibility of decomposition and degradation, and thus extend the battery's service life.

[0008] The present invention provides an electrolyte comprising the above-mentioned high-purity lithium fluoride, which enables the battery to exhibit excellent electrochemical performance.

[0009] This invention provides an apparatus that provides excellent preparation conditions for the purification of lithium fluoride, which is beneficial for the preparation of high-purity lithium fluoride with low content of lithium carbonate and other impurities.

[0010] This invention provides a method for purifying lithium fluoride, comprising the following steps:

[0011] 1) The lithium fluoride to be purified is washed with water at 0-50℃ to obtain a mixture including the first solid product;

[0012] 2) The mixture is subjected to ultrasonic treatment at 20-25 kHz and filtered to obtain a second solid product;

[0013] 3) The second solid product is reacted with electronic grade anhydrous hydrofluoric acid to produce a third liquid product. The third liquid product is ion-exchanged using a chelating resin at 0-80°C, followed by cooling, evaporation and crystallization. After filtration, a fourth solid product is obtained.

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

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

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

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

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

[0019] In the purification method described above, 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.

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

[0021] The purification method described above, wherein the washing process includes:

[0022] The fourth solid product was dried by pressurized inert gas purging until the mass percentage of water in the fourth solid product was less than 10 ppm, thus obtaining the high-purity lithium fluoride.

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

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

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

[0026] The high-purity lithium fluoride described above has a D50 ≤ 100 μm and a specific surface area of ​​300-1000 m². 2 / g, with a porosity of 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 comprising lithium hexafluorophosphate as described above.

[0029] The present invention also provides an apparatus for purifying lithium fluoride, comprising 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 connected in series via pipelines.

[0030] The lithium fluoride purification method provided by this invention involves washing the lithium fluoride to be purified with water to dissolve impurities such as lithium carbonate encapsulated inside and on the surface of the lithium fluoride into the aqueous phase, initially achieving physical separation of impurities such as lithium carbonate from lithium fluoride. Subsequently, the mixture including the first solid-phase product is ultrasonically treated to further promote the dissolution of impurities such as lithium carbonate and effectively remove organic contaminants adhering to the surface of the lithium fluoride. Then, hydrofluoric acid is used to fluorinate the second solid-phase product, converting lithium carbonate into lithium fluoride. Ion exchange of the lithium fluoride is performed using a chelating resin, followed by cooling and evaporation crystallization to further improve the purity of the lithium fluoride and increase raw material utilization. The resulting fourth solid-phase product is cleaned with a high-temperature inert gas to further remove residual organic contaminants from the surface and crystal lattice of the lithium fluoride, ultimately yielding high-purity lithium fluoride. Furthermore, this preparation method is simple, easy to operate, requires low equipment standards, and has high production efficiency.

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

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

[0033] The electrolyte provided by this invention includes high-purity lithium fluoride as described above. This electrolyte enables the battery to exhibit excellent electrochemical performance.

[0034] The apparatus provided by this 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. Attached Figure Description

[0035] The accompanying drawings, which are incorporated in and form 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 This is a schematic diagram of the device structure according to a specific embodiment of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

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

[0039] 1) The lithium fluoride to be purified is washed with water at 0-50℃ to obtain a mixture including the first solid product;

[0040] 2) The mixture is subjected to ultrasonic treatment at 20-25 kHz and filtered to obtain a second solid product;

[0041] 3) The second solid product is reacted with electronic grade anhydrous hydrofluoric acid to produce a third liquid product. The third liquid product is ion-exchanged using a chelating resin at 0-80°C, followed by cooling, evaporation and crystallization. After filtration, a fourth solid product is obtained.

[0042] 4) The fourth solid product is cleaned with an inert gas at 150-250℃ 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 mixture including a first solid product, wherein the first solid product is lithium fluoride.

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

[0045] Step 2): The mixture is ultrasonically treated at an ultrasonic frequency of 20-25 kHz and filtered to obtain the second solid product.

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

[0047] Step 3) Introduce electronic-grade anhydrous hydrofluoric acid 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 the third liquid-phase product.

[0048] The present invention does not limit the amount of electronic-grade anhydrous hydrofluoric acid added, and 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) The fourth solid phase product is cleaned with an inert gas to obtain high-purity lithium fluoride, wherein the temperature of the inert gas is 150-250℃.

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

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

[0053] This invention first washes the lithium fluoride to be purified with water. Utilizing the different solubilities of water for impurities such as lithium fluoride and lithium carbonate, the impurities such as lithium carbonate encapsulated inside and on the surface of the lithium fluoride are dissolved into the aqueous phase, initially achieving physical separation of impurities such as lithium carbonate from lithium fluoride. Subsequently, the mixture containing the first solid phase product is subjected to ultrasonic treatment. The strong cavitation effect and mechanical vibration generated by ultrasound further promote the dissolution of impurities such as lithium carbonate and effectively remove organic contaminants attached to the surface of lithium fluoride. Then, hydrofluoric acid is used to fluorinate the second solid phase product, converting lithium carbonate into lithium fluoride. Ion exchange of lithium fluoride is performed using chelating resin, followed by cooling evaporation and crystallization to further improve the purity of lithium fluoride and increase the utilization rate of raw materials, yielding a fourth solid phase product. Finally, the fourth solid phase product is cleaned with high-temperature inert gas to further remove residual organic contaminants on the surface and in the crystal lattice of lithium fluoride, ultimately obtaining high-purity lithium fluoride.

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

[0055] In some embodiments, step 1) involves removing soluble impurities after filtration, such as potassium fluoride, sodium fluoride, sodium carbonate, and potassium carbonate.

[0056] Step 2) Further removal of soluble impurities after filtration: potassium fluoride, sodium fluoride, sodium carbonate, potassium carbonate, etc.

[0057] Step 3) After filtration, further remove ethylenediaminetetraacetic acid (EDTA), potassium fluoride, sodium fluoride, etc.

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

[0059] In one specific embodiment, the ultrasonic treatment includes: ultrasonically treating 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 80 ppm, followed by filtration to obtain a second solid-phase product. Ultrasonic treatment of the mixture at low temperatures allows for greater utilization of the cavitation effect and mechanical vibration of ultrasound, resulting in more impurities such as lithium carbonate dissolving into the aqueous phase and more effectively stripping away organic contaminants. This significantly reduces the residual impurities on and inside the lithium fluoride surface, leading to higher purity lithium fluoride and laying the foundation for its subsequent applications.

[0060] In one 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 fluorination treatment temperature is 60-100°C, for example, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C, and the time is 0.2-20 min, for example, 0.2 min, 1 min, 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, or 20 min. The 0.95-1.05 equivalents of carbonate ion content in this invention refers to 0.95-1.05 times the molar ratio of hydrofluoric acid to carbonate ions in the chemical reaction, 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 within the above range, the lithium carbonate in the second solid product can be fully converted into lithium fluoride, thereby reducing the lithium carbonate content in the second solid product, further improving the purity of lithium fluoride, and further improving the conversion rate of the raw material of the lithium fluoride to be purified, thus reducing the production cost.

[0061] In one specific embodiment, the cleaning process includes: drying the fourth solid phase product by pressurized purging with inert gas until the mass percentage of water in the fourth solid phase product is less than 10 ppm, thereby obtaining high-purity lithium fluoride; wherein the pressure of the inert gas is 0.2-0.4 MPa, for example, 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. When the fourth solid phase product is subjected to pressure purging and drying with inert gas, the volatility of organic matter under high temperature conditions and the high temperature of inert gas can be used to deeply remove organic pollutants on the surface and in the lattice of lithium fluoride, thereby further reducing the impurity content in high-purity lithium fluoride. At the same time, it can quickly remove the aqueous 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 one specific embodiment, the impurities in the lithium fluoride to be purified, by mass percentage or mass concentration, include: lithium carbonate 0.5-1 wt%, sodium fluoride 50-200 ppm, potassium fluoride 50-200 ppm, sodium carbonate 50-200 ppm, potassium carbonate 50-200 ppm, water 0.5-1 wt%, and ethylenediaminetetraacetic acid ≤100 ppm. When the mass percentage of impurities in the lithium fluoride to be purified is within the above ranges, 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, which is beneficial to the preparation of high-purity lithium fluoride.

[0063] The present invention also provides a high-purity lithium fluoride, which is obtained by the above purification method. The impurities in the high-purity lithium fluoride, according to the 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 by ion chromatography testing.

[0065] The high-purity lithium fluoride of this invention has low lithium carbonate and other impurity content, which is beneficial for its subsequent applications. The inventors analyzed the reasons and believe that the low lithium carbonate and other impurity content in the lithium fluoride allows for the production of high-purity lithium hexafluorophosphate when used as a raw material in the reaction. Furthermore, when this high-purity lithium hexafluorophosphate is applied to the electrolyte, it improves the electrolyte's conductivity, thereby enhancing the overall performance of the lithium-ion battery, including energy density, power density, and cycle life. This also avoids the reaction between lithium carbonate and acidic substances in the electrolyte, which could lead to a decrease in battery performance, thus facilitating the widespread application of high-purity lithium fluoride.

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

[0067] In one specific embodiment, the D50 of high-purity lithium fluoride is ≤100μm, for example, D50 is 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, 65μm, 70μm, 75μm, 80μm, 85μm, 90μm, 95μm, or 99μm, etc., and the specific surface area is 300-1000m². 2 / g, for example, a specific surface area of ​​300m² 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., with a porosity of 30-75%, for example, porosities of 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, or 75%. When the particle size, specific surface area, and porosity of high-purity lithium fluoride are within the above ranges, when lithium fluoride is used as a raw material in the reaction, it can preferentially react with other reactants as well as lithium carbonate. This avoids impurities generated after the reaction of lithium carbonate with other reactants adhering to the surface of unreacted lithium fluoride, preventing the final product from being coated with impurities and resulting in problems such as difficulty in extraction and insufficient performance of the final product prepared from this lithium fluoride.

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

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

[0070] In one specific embodiment, high-purity lithium fluoride is introduced into a reaction vessel, anhydrous hydrogen fluoride is added and stirred to dissolve it. After dissolution, PF5 gas is directly introduced into the vessel, and the temperature is controlled at -20 to 20°C and the pressure is within 0 to 2 MPa. Subsequently, the reaction solution is cooled and crystallized, filtered and dried to obtain lithium hexafluorophosphate.

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

[0072] In one specific embodiment, the method further includes using ICP to detect the metal content of lithium hexafluorophosphate, using a filtration-drying-weighing method to detect the insoluble content, and using IC testing to determine the lithium hexafluorophosphate content.

[0073] The present invention also provides an electrolyte comprising lithium hexafluorophosphate as described above. The present invention does not limit the selection of organic solvents in the electrolyte or whether additives are added; selection can be made according to actual needs.

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

[0075] The present invention also provides an apparatus 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 connected in series via pipelines.

[0076] The present invention includes a water washing unit for slurry treatment of lithium fluoride to be purified with water to obtain a mixture containing a first solid phase product; an ultrasonic treatment unit for ultrasonic treatment of the mixture containing the first solid phase product and water, followed by filtration to obtain a second solid phase product; a fluorination reaction unit for fluorination reaction of the second solid phase product with hydrofluoric acid to obtain a third liquid phase product; an ion exchange unit for ion exchange of the third liquid phase product; an evaporation crystallization unit for cooling evaporation crystallization to obtain a fourth solid phase product; and a cleaning treatment unit for high-temperature inert gas purging and drying of the fourth solid phase product. The outlet of the water washing unit is connected to the inlet of the ultrasonic treatment unit, meaning the first solid phase product generated in the water washing unit is discharged from the outlet of the water washing unit and introduced into 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 process involves several interconnections: the second solid-phase product generated in the ultrasonic processing unit is exported from the outlet of the ultrasonic processing unit and introduced into the inlet of the fluorination reaction unit; the outlet of the fluorination reaction unit is connected to the inlet of the ion exchange unit, meaning the third liquid-phase product generated in the fluorination reaction unit is exported 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 to the inlet of the evaporation crystallization unit, meaning the third liquid-phase product after ion exchange is exported from the outlet of the ion exchange unit and introduced into the inlet of the evaporation crystallization unit; and the outlet of the evaporation crystallization unit is connected to the inlet of the cleaning treatment unit, meaning the fourth solid-phase product generated in the fluorination reaction unit is exported from the outlet of the evaporation crystallization unit and introduced into the inlet of the cleaning treatment unit. Finally, high-temperature inert gas purging and drying treatment is performed in the cleaning treatment unit to obtain high-purity lithium fluoride.

[0077] The present invention will be further described in detail below through specific embodiments.

[0078] Example 1

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

[0080] 1. At 20°C, the lithium fluoride to be purified is mixed with water and pulped to obtain a mixture including the first solid product.

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

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

[0083] 2. The mixture was ultrasonically treated at 20℃ and 24kHz until the mass percentage of carbonate ions in the liquid phase of the mixture was 85ppm, and then filtered to obtain the second solid phase product.

[0084] 3. The second solid product is reacted with electronic grade anhydrous hydrofluoric acid to produce a third liquid product. The third liquid product is then subjected to ion exchange with a chelating resin at 30°C. After cooling to 20°C, the product is evaporated, crystallized, and filtered to obtain a fourth solid product.

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

[0086] The fluorination treatment was carried out at a temperature of 80°C for 15 minutes.

[0087] 4. The fourth solid phase product is subjected to high-pressure purging and drying with nitrogen until the mass percentage of water in the fourth solid phase product is 9 ppm, thus obtaining high-purity lithium fluoride.

[0088] The nitrogen gas has a temperature of 200℃ and a pressure of 0.3MPa.

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

[0090] According to laser particle size analyzer testing, the D50 of high-purity lithium fluoride is 80 μm; according to BET testing, the specific surface area of ​​high-purity lithium fluoride is 800 m². 2 / g; According to the porosity tester, the porosity of high-purity lithium fluoride is 65%.

[0091] The preparation process of lithium fluoride provided in Examples 2-35 is basically the same as that in Example 1, and the specific parameters are shown in Table 1. The test results of high-purity lithium fluoride in Examples 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 basically the same as that in Example 1, and the specific parameters are shown in Table 3. The test results of high-purity lithium fluoride in Examples 36-39 are shown in Table 4.

[0100] Table 3

[0101]

[0102] Table 4

[0103]

[0104] Comparative Example 1

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

[0106] 1. At 20℃ and 24kHz, the lithium fluoride to be purified was mixed with water and ultrasonically treated until the mass percentage of carbonate ions in the liquid phase of the mixture was 85ppm. The mixture was then filtered to obtain the first solid phase product.

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

[0108] 2. The first solid product is reacted with electronic-grade anhydrous hydrofluoric acid to produce a fluorinated mixture. The fluorinated mixture is then filtered to obtain a second solid product with a moisture content of 20%.

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

[0110] The fluorination treatment was carried out at a temperature of 80°C for 15 minutes.

[0111] 3. The second solid product is subjected to high-pressure purging and drying with nitrogen until the water content in the second solid product is 9 ppm by mass, thus obtaining high-purity lithium fluoride.

[0112] The nitrogen gas has a temperature of 200℃ and a pressure of 0.3MPa.

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

[0114] According to laser particle size analyzer testing, the D50 of high-purity lithium fluoride is 132 μm; according to BET testing, the specific surface area of ​​high-purity lithium fluoride is 345 m². 2 / g; According to the porosity tester, the porosity of high-purity lithium fluoride is 29%.

[0115] Comparative Example 2

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

[0117] 1. At 20°C, the lithium fluoride to be purified is mixed with water, pulped, and filtered to obtain the first solid product;

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

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

[0120] 2. The first solid product is reacted with electronic-grade anhydrous hydrofluoric acid to produce a fluorinated mixture. The fluorinated mixture is then filtered to obtain a second solid product with a moisture content of 20%.

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

[0122] The fluorination treatment was carried out at a temperature of 80°C for 15 minutes.

[0123] 3. The second solid product is subjected to high-pressure purging and drying with nitrogen until the water content in the second solid product is 9 ppm by mass, thus obtaining high-purity lithium fluoride.

[0124] The nitrogen gas has a temperature of 200℃ and a pressure of 0.3MPa.

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

[0126] According to laser particle size analyzer testing, the D50 of high-purity lithium fluoride is 156 μm; according to BET testing, the specific surface area of ​​high-purity lithium fluoride is 275 m². 2 / g; According to the porosity tester, the porosity of high-purity lithium fluoride is 28%.

[0127] Comparative Example 3

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

[0129] 1. At 20°C, the lithium fluoride to be purified is mixed with water and pulped to obtain a mixture including the first solid product.

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

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

[0132] 2. The mixture was ultrasonically treated at 20℃ and 24kHz until the mass percentage of carbonate ions in the liquid phase of the first solid product was 85ppm, and then filtered to obtain the second solid product.

[0133] 3. The second solid product is subjected to high-pressure purging and drying with nitrogen until the water content in the second solid product is 9 ppm by mass, thus obtaining high-purity lithium fluoride.

[0134] The nitrogen gas has a temperature of 200℃ and a pressure of 0.3MPa.

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

[0136] According to laser particle size analyzer testing, the D50 of high-purity lithium fluoride is 110 μm; according to BET testing, the specific surface area of ​​high-purity lithium fluoride is 277 m². 2 / g; According to the porosity tester, the porosity of high-purity lithium fluoride is 27%.

[0137] Comparative Example 4

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

[0139] 1. At 20°C, the lithium fluoride to be purified is mixed with water and pulped to obtain a mixture containing the first solid phase product;

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

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

[0142] 2. The mixture was ultrasonically treated at 20℃ and 24kHz until the mass percentage of carbonate ions in the liquid phase of the mixture was 85ppm, and then filtered to obtain the second solid phase product.

[0143] 3. The second solid product is reacted with electronic grade anhydrous hydrofluoric acid to produce a third liquid product. The third liquid product is then subjected to ion exchange with a chelating resin at 30°C. After cooling to 20°C, the product is evaporated and crystallized, and then filtered to obtain the fourth solid product.

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

[0145] The fluorination treatment was carried out at a temperature of 80°C for 15 minutes.

[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, thus obtaining high-purity lithium fluoride.

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

[0148] According to laser particle size analyzer testing, the D50 of high-purity lithium fluoride is 187 μm; according to BET testing, the specific surface area of ​​high-purity lithium fluoride is 245 m². 2 / g; According to the porosity tester, the porosity of high-purity lithium fluoride is 25%.

[0149] Comparative Example 5

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

[0151] 1. At 60°C, the lithium fluoride to be purified is mixed with water and pulped to obtain a mixture containing the first solid phase product;

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

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

[0154] 2. The mixture was ultrasonically treated at 20℃ and 24kHz until the mass percentage of carbonate ions in the liquid phase of the mixture was 85ppm, and then filtered to obtain the second solid phase product.

[0155] 3. The second solid product is reacted with electronic grade anhydrous hydrofluoric acid to produce a third liquid product. The third liquid product is then subjected to ion exchange with a chelating resin at 30°C. After cooling to 20°C, the product is evaporated and crystallized, and then filtered to obtain the fourth solid product.

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

[0157] The fluorination treatment was carried out at a temperature of 80°C for 15 minutes.

[0158] 4. The fourth solid phase product is subjected to high-pressure purging and drying with nitrogen until the mass percentage of water in the fourth solid phase product is 9 ppm, thus obtaining high-purity lithium fluoride.

[0159] The nitrogen gas has a temperature of 200℃ and a pressure of 0.3MPa.

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

[0161] According to laser particle size analyzer testing, the D50 of high-purity lithium fluoride is 117 μm; according to BET testing, the specific surface area of ​​high-purity lithium fluoride is 256 m². 2 / g; According to the porosity tester, the porosity of high-purity lithium fluoride is 28%.

[0162] Comparative Example 6

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

[0164] 1. At 20°C, the lithium fluoride to be purified is mixed with water and pulped to obtain a mixture containing the first solid phase product;

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

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

[0167] 2. The mixture was ultrasonically treated at 20℃ and 15kHz until the mass percentage of carbonate ions in the liquid phase of the mixture was 85ppm, and then filtered to obtain the second solid phase product.

[0168] 3. The second solid product is reacted with electronic grade anhydrous hydrofluoric acid to produce a third liquid product. The third liquid product is then subjected to ion exchange with a chelating resin at 30°C. After cooling to 20°C, the product is evaporated and crystallized, and then filtered to obtain the fourth solid product.

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

[0170] The fluorination treatment was carried out at a temperature of 80°C for 15 minutes.

[0171] 4. The fourth solid phase product is subjected to high-pressure purging and drying with nitrogen until the mass percentage of water in the fourth solid phase product is 9 ppm, thus obtaining high-purity lithium fluoride.

[0172] The nitrogen gas has a temperature of 200℃ and a pressure of 0.3MPa.

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

[0174] According to laser particle size analyzer testing, the D50 of high-purity lithium fluoride is 115 μm; according to BET testing, the specific surface area of ​​high-purity lithium fluoride is 394 m². 2 / g; According to the porosity tester, the porosity of high-purity lithium fluoride is 29%.

[0175] Comparative Example 7

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

[0177] 1. At 20°C, the lithium fluoride to be purified is mixed with water and pulped to obtain a mixture containing the first solid phase product;

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

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

[0180] 2. The mixture was ultrasonically treated at 20℃ and 24kHz until the mass percentage of carbonate ions in the liquid phase of the mixture was 85ppm, thus obtaining the second solid phase product.

[0181] 3. The second solid product is reacted with electronic grade anhydrous hydrofluoric acid to produce a third liquid product. The third liquid product is then subjected to ion exchange with a chelating resin at 30°C. After cooling to 20°C, the product is evaporated and crystallized, and then filtered to obtain the fourth solid product.

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

[0183] The fluorination treatment was carried out at a temperature of 80°C for 15 minutes.

[0184] 4. The fourth solid phase product is subjected to high-pressure purging and drying with nitrogen until the mass percentage of water in the fourth solid phase product is 9 ppm, thus obtaining high-purity lithium fluoride.

[0185] The nitrogen gas has a temperature of 300℃ and a pressure of 0.3MPa.

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

[0187] According to laser particle size analyzer testing, the D50 of high-purity lithium fluoride is 20 μm; according to BET testing, the specific surface area of ​​high-purity lithium fluoride is 1350 m². 2 / g; According to the porosity tester, the porosity of high-purity lithium fluoride is 85%.

[0188] In summary, based on the comparison between Example 1 and Comparative Example 1, it can be seen that water washing can reduce the residual amount of impurities on and inside the lithium fluoride surface, thereby improving the purity of lithium fluoride; based on the comparison between Example 1 and Comparative Example 2, it can be seen that ultrasonic treatment can effectively remove impurities on and inside the lithium fluoride surface, resulting in higher purity lithium fluoride; based on 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; based on the comparison between Example 1 and Comparative Example 4, it can be seen that cleaning treatment can deeply remove impurities on the surface and within the lattice of lithium fluoride, and can quickly remove the aqueous phase, achieving the preparation of high-purity lithium fluoride with high specific surface area, high porosity, and small particle size; based on Examples 1-3 and Comparison with Example 5 shows that water washing at 0-50℃ can dissolve impurities such as lithium carbonate inside and on the surface of lithium fluoride into the aqueous phase, achieving physical separation of impurities such as lithium carbonate from lithium fluoride and improving the purity of lithium fluoride. Comparison with Examples 1, 12, 13 and Comparative Example 6 shows that at an ultrasonic frequency of 20-25kHz, the strong cavitation effect and mechanical oscillation generated by ultrasound can better promote the dissolution of impurities such as lithium carbonate, thereby improving the purity of lithium fluoride. Comparison with Examples 1, 29-31 and Comparative Example 7 shows that cleaning with inert gas at 150-250℃ can obtain high-purity lithium fluoride with suitable specific surface area and porosity, which is beneficial for the subsequent application of high-purity lithium fluoride.

[0189] A comparison of Examples 1-7 shows that when the mass ratio of lithium fluoride to water to be purified is in the range of 1:(10-30) during pulping, it is beneficial to improve the purity of lithium fluoride. A comparison of Examples 1 and 7-11 shows that when the stirring speed and stirring time during pulping are in the ranges of 30-200 r / min and 0.1-5 h, respectively, the purity of high-purity lithium fluoride can be improved. A comparison of Examples 1 and 14-17 shows that when the ultrasonic treatment temperature is in the range of 0-50℃ until the mass percentage of carbonate ions in the liquid phase is greater than 80 ppm, the purity of high-purity lithium fluoride can be further improved. A comparison of Examples 1 and 18-21 shows that 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... Lithium carbonate can be fully converted into lithium fluoride, which is beneficial to improving the purity of high-purity lithium fluoride. A comparison of Examples 1 and 22-25 shows that when the fluorination treatment temperature is 60-100℃ and the time is 0.2-20min, lithium carbonate can undergo a complete fluorination reaction, reducing the impurity content in the high-purity lithium fluoride. A comparison of Example 1 shows that when purging with an inert gas at a pressure of 0.2-0.4MPa 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. A comparison of Examples 1 and 36-39 shows 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 resulting in high purity of the prepared high-purity lithium fluoride.

[0190] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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, Includes the following steps: 1) At 0-50℃, the lithium fluoride to be purified is pulped with water to obtain a mixture including the first solid product; 2) The mixture is subjected to ultrasonic treatment at 20-25 kHz and filtered to obtain a second solid product; 3) The second solid product is reacted with electronic grade anhydrous hydrofluoric acid to produce a third liquid product. The third liquid product is ion-exchanged using a chelating resin at 0-80°C, followed by cooling, evaporation and crystallization. After filtration, a fourth solid product is obtained. 4) The fourth solid phase product is cleaned by inert gas pressurization purging at 150-250℃ to obtain high-purity lithium fluoride, wherein the pressure of the inert gas is 0.2-0.4MPa.

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

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

4. The method for purifying lithium fluoride according to claim 3, characterized in that, 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 fluorination treatment is performed at a temperature of 60-100°C for a time of 0.2-20 min.

5. The method for purifying lithium fluoride according to any one of claims 1-4, characterized in that, The cleaning process includes: The fourth solid product was dried by pressurized inert gas purging until the mass percentage of water in the fourth solid product was less than 10 ppm, thus obtaining the high-purity lithium fluoride.

6. The method for purifying lithium fluoride according to any one of claims 1-4, characterized in that, The impurities in the lithium fluoride to be purified, by mass percentage or mass concentration, include: lithium carbonate 0.5-1 wt%, sodium fluoride 50-200 ppm, potassium fluoride 50-200 ppm, sodium carbonate 50-200 ppm, potassium carbonate 50-200 ppm, water 0.5-1 wt%, and ethylenediaminetetraacetic acid ≤100 ppm.

7. A high-purity lithium fluoride, characterized in that, It is prepared by the purification method of lithium fluoride according to any one of claims 1-6; The impurities in the high-purity lithium fluoride, by mass concentration, include: lithium carbonate ≤ 50 ppm, sodium fluoride ≤ 50 ppm, potassium fluoride ≤ 50 ppm, sodium carbonate ≤ 10 ppm, potassium carbonate ≤ 10 ppm, moisture ≤ 10 ppm, and ethylenediaminetetraacetic acid ≤ 10 ppm. The high-purity lithium fluoride has a D50 ≤ 100 μm and a specific surface area of ​​300-1000 m². 2 / g, with a porosity of 30-75%.

8. A lithium hexafluorophosphate, characterized in that, It is prepared from the high-purity lithium fluoride described in claim 7.

9. An electrolyte, characterized in that, Including the lithium hexafluorophosphate as described in claim 8.

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