A method for producing lithium chloride

Abstract

The application provides a preparation method of lithium chloride, comprising the following steps: 1) mixing and slurring deionized water and lithium carbonate, and then carbonizing treatment is carried out by introducing carbon dioxide gas to obtain a lithium bicarbonate solution; 2) decomposing the lithium bicarbonate solution to obtain a mixture comprising lithium carbonate, wherein the mass M of the mixture and the mass N of the lithium bicarbonate solution satisfy 0.14 <= M / N <= 0.90; 3) solid-liquid separation treatment is carried out on the mixture comprising lithium carbonate to obtain refined lithium carbonate and a decomposition mother liquor; 4) acidification treatment is carried out on the refined lithium carbonate to obtain a lithium chloride solution; and 5) solidification treatment is carried out on the lithium chloride solution to obtain battery-grade lithium chloride. The preparation method of lithium chloride provided by the application can prepare lithium chloride with high purity.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, and particularly relates to a method for preparing lithium chloride. Background Technology

[0002] With the rapid development of the new energy and 3C industries, the demand for lithium-ion batteries both domestically and internationally has exploded, driving a rapid increase in the demand for lithium metal. Lithium metal is primarily produced through the molten salt electrolysis of lithium chloride. Therefore, to meet the demand for lithium metal, it is necessary to significantly increase the production of lithium chloride.

[0003] In traditional techniques, lithium chloride is mainly produced by acidifying lithium carbonate, followed by evaporation, crystallization, and drying of the solution. However, because impurity ions from lithium carbonate ultimately enter the lithium chloride product, it fails to meet the requirements for battery-grade lithium chloride, thus affecting the quality of the lithium metal product. Therefore, developing a method for preparing high-purity lithium chloride is a pressing technical problem that needs to be solved at present. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing lithium chloride, thereby solving the problem of low purity of lithium chloride.

[0005] This invention provides a method for preparing lithium chloride, comprising the following steps:

[0006] 1) After mixing and slurrying deionized water and lithium carbonate, carbon dioxide gas is introduced for carbonation treatment to obtain lithium bicarbonate solution;

[0007] 2) The lithium bicarbonate solution is decomposed to obtain a mixture containing lithium carbonate, wherein the mass M of the mixture and the mass N of the lithium bicarbonate solution satisfy Equation 1.

[0008] 0.14≤M / N≤0.90 Equation 1;

[0009] 3) The mixture containing lithium carbonate is subjected to solid-liquid separation treatment to obtain refined lithium carbonate and decomposition mother liquor;

[0010] 4) The refined lithium carbonate is acidified to obtain a lithium chloride solution;

[0011] 5) The lithium chloride solution is solidified to obtain battery-grade lithium chloride.

[0012] In the lithium chloride preparation method described above, the decomposition treatment temperature is 70-100℃; the stirring rate of the decomposition treatment is 200-500 rpm.

[0013] In the lithium chloride preparation method described above, the mass ratio of deionized water to lithium carbonate is (20-25):1.

[0014] In the lithium chloride preparation method described above, in step 1), the lithium carbonate contains a lithium carbonate content of not less than 99.5 wt% and a sodium content of 0.002%-0.1% by mass.

[0015] In the lithium chloride preparation method described above, the sodium content in the battery-grade lithium chloride is ≤0.0015%.

[0016] In the lithium chloride preparation method described above, the acidification treatment uses hydrochloric acid with a concentration of 0.1-12 mol / L.

[0017] In the lithium chloride preparation method described above, the sodium content in the hydrochloric acid is not higher than 0.5 mg / L.

[0018] In the lithium chloride preparation method described above, the carbon dioxide gas is introduced at a rate of 0.02-4 L / min.

[0019] In the lithium chloride preparation method described above, the solidification process sequentially includes evaporation crystallization, washing, centrifugation, and drying.

[0020] The method for preparing lithium chloride as described above involves using a sodium removal agent to remove sodium from the decomposition mother liquor, thereby obtaining recovered lithium carbonate, which is then recycled to participate in the mixed slurry process.

[0021] The sodium removal agent includes Li 1+x Al x Ge 2-x (PO4)3, 0.2≤x≤0.5, wherein the sodium removal treatment is performed at a temperature of 50-80℃ for 5-20 hours.

[0022] This invention provides a method for preparing lithium chloride. The method involves carbonizing a lithium carbonate slurry to obtain a lithium bicarbonate solution, then decomposing the lithium bicarbonate solution to obtain a lithium carbonate mixture. Solid-liquid separation yields refined lithium carbonate. By controlling the mass ratio of the mixture to the lithium bicarbonate solution, i.e., controlling the water evaporation rate during the decomposition process, the sodium content in the refined lithium carbonate can be minimized. Subsequent acidification and solidification treatments result in lithium chloride with high purity, meeting the requirements for battery-grade lithium chloride, which can be used to prepare metallic lithium. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic flowchart of a method for preparing lithium chloride according to an embodiment of the present invention. Detailed Implementation

[0025] 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.

[0026] Figure 1 This is a schematic flowchart of a method for preparing lithium chloride according to an embodiment of the present invention, as shown below. Figure 1 As shown, the preparation method of lithium chloride includes the following steps:

[0027] 1) After mixing and slurrying deionized water and lithium carbonate, carbon dioxide gas is introduced for carbonation treatment to obtain lithium bicarbonate solution;

[0028] 2) The lithium bicarbonate solution is decomposed to obtain a mixture containing lithium carbonate, wherein the mass M of the mixture and the mass N of the lithium bicarbonate solution satisfy Equation 1.

[0029] 0.14≤M / N≤0.90 Equation 1;

[0030] 3) The mixture containing lithium carbonate is subjected to solid-liquid separation treatment to obtain refined lithium carbonate and decomposition mother liquor;

[0031] 4) The refined lithium carbonate is acidified to obtain a lithium chloride solution;

[0032] 5) The lithium chloride solution is solidified to obtain battery-grade lithium chloride.

[0033] In this embodiment of the invention, lithium carbonate is used as a raw material to prepare lithium chloride. In one embodiment, deionized water and lithium carbonate are first mixed to form a slurry system. Then, carbon dioxide gas is introduced into the slurry system for carbonation treatment. During this process, lithium carbonate, carbon dioxide, and water react to generate lithium bicarbonate. Lithium bicarbonate is soluble in water, and a lithium bicarbonate solution is obtained in this step. The lithium bicarbonate solution is then decomposed to generate lithium carbonate, carbon dioxide, and water. Because lithium carbonate has low solubility in water, the resulting mixture includes lithium carbonate. M is the mass of the mixture including lithium carbonate, and N is the mass of the lithium bicarbonate solution, satisfying 0.14≤M / N≤0.90. The mixture including solid lithium carbonate is subjected to solid-liquid separation treatment to obtain refined lithium carbonate and decomposition mother liquor. The obtained refined lithium carbonate is then acidified, i.e., lithium carbonate reacts with hydrochloric acid to generate lithium chloride, resulting in a lithium chloride solution. The lithium chloride solution is then solidified to obtain lithium chloride, the purity of which meets the requirements for battery-grade lithium chloride.

[0034] In step 1), deionized water and lithium carbonate are first mixed to form a slurry system for subsequent carbonation treatment of lithium carbonate. This embodiment does not specifically limit the ratio of deionized water to lithium carbonate; those skilled in the art can choose according to actual needs, as long as the lithium carbonate forms a slurry suitable for carbonation. In the carbonation step, carbon dioxide gas is introduced into the lithium carbonate slurry until all the solid lithium carbonate in the slurry dissolves to obtain a lithium bicarbonate solution. Specifically, by introducing carbon dioxide gas into the lithium carbonate slurry, solid lithium carbonate can be converted into lithium bicarbonate. Lithium bicarbonate is soluble in water, allowing lithium ions to enter the liquid phase. Calcium, magnesium, and other polyvalent ions in lithium carbonate can be easily separated and impurities removed during the lithium carbonate production process. Because sodium ions have similar properties to lithium ions, they coexist with lithium ions in the solution. According to a specific embodiment of the present invention, carbon dioxide gas can be introduced into the lithium carbonate slurry at 20-30°C. The inventors discovered that within a certain temperature range, increasing the temperature is beneficial to increasing the reaction rate. However, since the solubility of lithium carbonate and carbon dioxide decreases with increasing temperature, increasing the temperature actually reduces the reaction rate.

[0035] In step 2), the lithium bicarbonate solution obtained in step 1) is decomposed to obtain a mixture containing lithium carbonate. Specifically, the decomposition process breaks down the lithium bicarbonate dissolved in the liquid phase into lithium carbonate, carbon dioxide, and water. During the decomposition process, the reaction solution is continuously stirred to help expel carbon dioxide gas, prevent overflow, and collect the generated carbon dioxide gas for recycling in the carbonization step. Water evaporation occurs during the decomposition process. M is the mass of the mixture containing lithium carbonate, and N is the mass of the lithium bicarbonate solution. When the relationship between M and N satisfies 0.14 ≤ M / N ≤ 0.90, the water evaporation rate during the decomposition process is considered to be within an appropriate range, ensuring that most sodium ions remain in the solution while the sodium ion content in the resulting lithium carbonate is extremely low. In this embodiment, the decomposition conditions are not particularly limited; those skilled in the art can select them according to actual needs, as long as the lithium bicarbonate is completely decomposed to obtain a mixture containing lithium carbonate.

[0036] In step 3), the mixture obtained in step 2), i.e., the mixture containing lithium carbonate, undergoes solid-liquid separation to obtain refined lithium carbonate and decomposition mother liquor. Because step 2) limits the relationship between the mass of the mixture and the mass of the lithium bicarbonate solution, i.e., controls the water evaporation rate during the decomposition process, sodium ions are distributed in a certain proportion in the lithium carbonate and the decomposition mother liquor. Through solid-liquid separation, most of the sodium ions are enriched in the decomposition mother liquor, while the refined lithium carbonate contains very little sodium ions, and the decomposition mother liquor also contains carbonate ions and some lithium ions dissolved in the mother liquor. In this embodiment, the method of solid-liquid separation is not particularly limited; those skilled in the art can choose according to actual needs, as long as the separation of refined lithium carbonate and decomposition mother liquor can be achieved. Optionally, the solid-liquid separation process employs one or more of the following methods: pressure filtration, vacuum filtration, and centrifugation.

[0037] In step 4), the refined lithium carbonate obtained in step 3) is acidified to obtain a lithium chloride solution. Because refined lithium carbonate has extremely low solubility in water, acidification generates lithium chloride, which dissolves in the solution to obtain a lithium chloride solution for further processing to obtain solid lithium chloride. Since the hydrochloric acid used for acidification contains a small amount of sodium impurity, some sodium ions are introduced into the lithium chloride solution obtained in this step. In this embodiment, the acid used for acidification is not particularly limited; those skilled in the art can choose according to actual needs, as long as it can react with refined lithium carbonate to obtain a lithium chloride solution.

[0038] In step 5), the lithium chloride solution obtained in step 4) is solidified to obtain solid lithium chloride. The final lithium chloride has high purity and extremely low sodium ion content, meeting the sodium requirement of battery-grade anhydrous lithium chloride (YS / T 744-2010), i.e., sodium content ≤ 0.0015%. In this embodiment, the solidification method is not particularly limited. Those skilled in the art can choose according to actual needs, as long as it can solidify the lithium chloride solution to obtain high-purity lithium chloride.

[0039] In this embodiment, lithium carbonate slurry is carbonized to obtain lithium bicarbonate solution, and then the lithium bicarbonate solution is decomposed to obtain lithium carbonate mixture. After solid-liquid separation, refined lithium carbonate is obtained. By controlling the mass ratio of the mixture to the lithium bicarbonate solution, i.e., controlling the water evaporation rate during the decomposition process, the sodium content in the refined lithium carbonate can be kept to a minimum. After subsequent acidification and solidification treatments, the final lithium chloride obtained has a high purity, meeting the requirements for battery-grade lithium chloride.

[0040] In some embodiments of the present invention, the temperature of the decomposition process is 70-100°C; the stirring rate of the decomposition process is 200-500 rpm.

[0041] It is understood that the above-mentioned decomposition treatment of lithium bicarbonate solution can be achieved by controlling a suitable temperature and stirring rate. In this embodiment, the temperature of the decomposition treatment is controlled at 70-100℃ and the stirring rate is controlled at 200-500rpm.

[0042] In one embodiment, the decomposition temperature can be 40-200℃, preferably 70-100℃; the stirring rate is 100-1000 rpm, preferably 200-500 rpm. The inventors have found that if the decomposition temperature is too low, the yield of refined lithium carbonate is low. As the temperature increases, the yield gradually increases. This is mainly because the decomposition of lithium bicarbonate is an endothermic reaction. Furthermore, the solubility of lithium carbonate decreases with increasing temperature; higher temperatures are more conducive to increasing the lithium carbonate yield. However, excessively high temperatures can lead to an increase in the concentration of impurities in the refined lithium carbonate, and temperatures exceeding 100℃ can cause abnormally vigorous reactions, releasing large amounts of carbon dioxide gas and easily causing overflow accidents. Simultaneously, a suitable stirring rate during the decomposition process helps to expel carbon dioxide gas, preventing overflow of the reaction liquid, and also promotes heat dissipation in the solution, preventing localized overheating that could lead to abnormal reactions and equipment damage. The decomposition process takes 0.1-2 hours.

[0043] This embodiment improves the yield of refined lithium carbonate by controlling the temperature and stirring rate of the decomposition process within a suitable range, and also avoids abnormal reactions and equipment damage caused by local overheating.

[0044] In some embodiments of the present invention, the mass ratio of deionized water to lithium carbonate is (20-25):1.

[0045] In one embodiment, the mass ratio of deionized water to lithium carbonate can be controlled to be (10-50):1, preferably (20-25):1, to better slurry the lithium carbonate. Optionally, the solid-liquid ratio of deionized water to lithium carbonate can be any value between 20:1, 21:1, 22:1, 23:1, 24:1, and 25:1.

[0046] The inventors discovered that when the mass of lithium carbonate is constant, although increasing the amount of deionized water leads to a longer contact time and increased contact area between the lithium carbonate slurry and carbon dioxide, resulting in a more complete reaction, the reaction rate does not continue to increase beyond a certain limit, as the amount of deionized water required to dissolve a certain amount of lithium carbonate is fixed. Instead, it increases energy consumption during the subsequent pyrolysis of the lithium bicarbonate solution. Therefore, in this embodiment, the mass ratio of deionized water to lithium carbonate is controlled at (20-25):1.

[0047] In this embodiment, the mass ratio of deionized water to lithium carbonate is controlled at (20-25):1, which allows the lithium carbonate to be better slurried and facilitates subsequent carbonization treatment of lithium carbonate.

[0048] In some embodiments of the present invention, in step 1), the lithium carbonate has a mass percentage content of not less than 99.5 wt% and a mass percentage content of sodium of 0.002%-0.1%.

[0049] It is understandable that to ensure high purity of the prepared lithium chloride, especially with sodium ion content within a specified range, the purity of the raw material lithium carbonate needs to be maintained within a certain range. In this embodiment, the mass percentage of lithium carbonate is controlled to be no less than 99.5 wt%, and the mass percentage of sodium element is 0.002%-0.1%. This ensures that the purity of the lithium chloride prepared by the preparation method provided by this invention using the above-mentioned lithium carbonate as raw material meets the requirements for battery-grade lithium chloride, guaranteeing product quality stability. Simultaneously, excessive impurities in the raw materials can be avoided during the production process, preventing production efficiency from being affected by impurity removal. Furthermore, higher purity raw materials also increase the stability of the production process.

[0050] In this embodiment, controlling the purity of the raw material lithium carbonate can ensure the stability of product quality and improve production efficiency.

[0051] In some embodiments of the present invention, the sodium content in the battery-grade lithium chloride is ≤0.0015%.

[0052] In this embodiment, the sodium content in battery-grade lithium chloride is controlled to be ≤0.0015%, which meets the sodium requirements in battery-grade anhydrous lithium chloride (YS / T 744-2010), meaning that the lithium chloride has high purity and can be used to prepare metallic lithium.

[0053] In some embodiments of the present invention, the acidification treatment uses hydrochloric acid with a concentration of 0.1-12 mol / L.

[0054] It is understood that when acidifying refined lithium carbonate, hydrochloric acid can be used to convert lithium into a soluble lithium salt that dissolves in solution. That is, acidifying refined lithium carbonate with hydrochloric acid yields lithium chloride, carbon dioxide, and water. Lithium chloride is a water-soluble lithium salt, and dissolving it in water produces a lithium chloride solution. In this embodiment, the concentration of hydrochloric acid can be 0.1-12 mol / L, preferably 7-11 mol / L.

[0055] In this embodiment, hydrochloric acid is used to acidify refined lithium carbonate, and the concentration of hydrochloric acid is limited to 7-11 mol / L. This can efficiently generate lithium chloride solution with high stability and low raw material cost.

[0056] In some embodiments of the present invention, the sodium content in the hydrochloric acid is not higher than 0.5 mg / L.

[0057] It is understandable that when using hydrochloric acid to acidify refined lithium carbonate to generate lithium chloride solution, the lower the content of sodium impurities introduced, the better. Commercially available hydrochloric acid contains a certain amount of sodium ions, which will inevitably introduce sodium impurities into the lithium chloride solution. To ensure that the sodium content in the final prepared lithium chloride solid meets the requirements for battery-grade anhydrous lithium chloride, the sodium content in the hydrochloric acid used for acidification needs to be limited. The inventors have discovered that when the sodium content in the hydrochloric acid is no higher than 0.5 mg / L, the lithium chloride prepared according to the method provided by this invention has a high purity, meeting the requirements for battery-grade anhydrous lithium chloride.

[0058] In this embodiment, the sodium content in the hydrochloric acid is controlled to be no higher than 0.5 mg / L, which can ensure that the final lithium chloride has high purity, meets the requirements of battery-grade anhydrous lithium chloride, and guarantees the stability of the lithium chloride product.

[0059] In some embodiments of the present invention, the carbon dioxide gas is introduced at a rate of 0.02-4 L / min.

[0060] In this embodiment, the carbon dioxide introduction rate is controlled at 0.02-4 L / min. Within a suitable range, the reaction rate can be appropriately controlled to make the carbonization process more complete, thereby converting all lithium carbonate in the slurry system into lithium bicarbonate, which exists in the solution and can improve the subsequent lithium yield.

[0061] In this embodiment, by controlling the rate of carbon dioxide introduction, the carbonization process can be made more complete, and all lithium carbonate is converted into lithium bicarbonate, thereby increasing the lithium yield.

[0062] In some embodiments of the present invention, the curing process includes, in sequence, evaporation crystallization, washing, centrifugation, and drying.

[0063] The drying process is carried out at a temperature of 80-200℃.

[0064] In this embodiment, the lithium chloride solution obtained through acidification is evaporated and crystallized to obtain a wet crude lithium chloride product. Then, it is washed with deionized water to remove impurities, especially sodium, from the surface of the wet crude lithium chloride product. This step further removes sodium impurities. The washed wet crude lithium chloride product is then centrifuged to separate most of the deionized water used in the washing process from the lithium chloride product, leaving impurities such as sodium in the deionized water. Finally, the wet crude lithium chloride product is dried to obtain a lithium chloride product with higher purity.

[0065] According to a specific embodiment of the present invention, the drying process can be completed at a temperature of 80-200°C. The inventors have discovered that drying at 80-200°C can prevent the lithium chloride product from undergoing a chemical reaction or decomposition during the drying process, thereby further improving the quality of the lithium chloride product. If the drying temperature is too low, the residual water in the product will evaporate too slowly, resulting in low efficiency; if the drying temperature is too high, it will cause the lithium chloride product to decompose or react with other substances.

[0066] In this embodiment, the lithium chloride solution is subjected to evaporation crystallization, washing, centrifugation and drying in sequence, and the drying temperature is controlled at 80-200℃, which can make the final lithium chloride have a high purity.

[0067] In some embodiments of the present invention, the decomposition mother liquor is treated with a sodium removal agent to remove sodium, thereby obtaining recovered lithium carbonate which is recycled to participate in the mixed slurry.

[0068] The sodium removal agent includes Li 1+x Al x Ge 2-x (PO4)3, 0.2≤x≤0.5, wherein the sodium removal treatment is performed at a temperature of 50-80℃ for 5-20 hours.

[0069] In this embodiment, a sodium removal agent is added to the obtained decomposition mother liquor for sodium removal treatment, and then lithium carbonate in the decomposition mother liquor is recovered. The recovered lithium carbonate is returned to the mixing and slurry treatment process for recycling to prepare lithium chloride, which can achieve the purpose of saving raw materials.

[0070] According to a specific embodiment of the present invention, the sodium removal agent may be Li 1+x Al x Ge 2-x (PO4)3, 0.2≤x≤0.5, sodium removal treatment can be completed at 50-80℃ for 5-20 hours. The inventors discovered that the sodium removal agent Li 1+x Al x Ge 2-x (PO4)3, with a crystalline structure of 0.2 ≤ x ≤ 0.5, has a body-centered cubic form. Internal interconnected ion channels form three-dimensional ion channels, allowing lithium ions to migrate between them. Sodium ion removal is achieved through the exchange of lithium and sodium ions. The sodium removal temperature is 50-80℃, preferably 60-70℃.

[0071] The temperature is set at ℃, and the treatment time is 5-20 hours, preferably 10-16 hours, to ensure sufficient exchange between lithium ions and sodium ions, thereby achieving the purpose of sodium removal.

[0072] This embodiment improves the sodium removal effect by adding a sodium removal agent to the decomposition mother liquor and controlling the sodium removal conditions, resulting in higher purity of the recovered lithium carbonate, which is then recycled into the mixing and slurry step, leading to higher purity of the final lithium chloride.

[0073] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0074] Example 1

[0075] The method for preparing lithium chloride in this embodiment includes the following steps:

[0076] 1) Weigh 10g of lithium carbonate (lithium carbonate content is 99.7wt%, sodium content is 0.02%) and 250g of deionized water respectively, add them to the reaction vessel and mix them into a slurry. Introduce carbon dioxide gas into the reaction vessel at a rate of 0.1L / min to obtain a lithium bicarbonate solution. Weigh the lithium bicarbonate solution and find that the mass is 266g.

[0077] 2) The lithium bicarbonate solution was heated at a decomposition temperature of 95℃ and stirred at a stirring rate of 300 rpm. White powdery lithium carbonate precipitated out, and a mixture containing lithium carbonate was obtained. The mass of the mixture was weighed as 120 g.

[0078] 3) The mixture of lithium carbonates is centrifuged to obtain refined lithium carbonate and decomposition mother liquor;

[0079] 4) Mix 0.15 L of 2 mol / L hydrochloric acid (sodium content 0.5 mg / L) with purified lithium carbonate and stir to produce an acidification reaction, thus obtaining a lithium chloride solution;

[0080] 5) The lithium chloride solution was evaporated, crystallized, washed, centrifuged, and dried at 120°C to obtain solid lithium chloride. The sodium content was tested to be 0.0006%, which meets the sodium requirements (Na≤0.0015%) of battery-grade anhydrous lithium chloride (YS / T 744-2010).

[0081] 6) Add 10g of sodium removal agent Li to the above decomposition mother liquor. 1.5 Al 0.5 Ge 1.5 (PO4)3 was reacted at 60°C for 10 hours, then filtered, evaporated and crystallized, and dried to obtain recovered lithium carbonate with a purity of 99.5 wt%, which can be returned to step 1) for recycling.

[0082] The lithium yield in this process is the mass ratio of lithium in lithium chloride and lithium in recovered lithium carbonate to the lithium brought in by the sodium removal agent and the lithium in lithium carbonate used when forming the slurry.

[0083] Examples 2-5

[0084] The preparation methods of lithium chloride in Examples 2-5 are the same as those in Example 1, except that the mass ratio of the lithium carbonate mixture to the lithium bicarbonate solution is different. The specific parameters are shown in Table 1.

[0085] Table 1

[0086]

[0087] Examples 6-11

[0088] The preparation methods of lithium chloride in Examples 6-11 are the same as those in Example 1, except that the decomposition temperature and stirring rate are different. The specific parameters are shown in Table 2.

[0089] Table 2

[0090]

[0091] Examples 12-15

[0092] Examples 12-15 are prepared using the same method as in Example 1 for lithium chloride, except that the mass ratio of deionized water to lithium carbonate is different. The specific parameters are shown in Table 3.

[0093] Table 3

[0094]

[0095] Examples 16-19

[0096] Examples 16-19 are prepared using the same method as Example 1 for lithium chloride, except that the lithium carbonate and sodium content in the lithium carbonate added in step 1) are different. The specific parameters are shown in Table 4.

[0097] Table 4

[0098]

[0099] Examples 20-24

[0100] Examples 20-24 are prepared using the same method as in Example 1 for lithium chloride, except that the concentration of hydrochloric acid added and the sodium content in the hydrochloric acid are different. Specific parameters are shown in Table 5.

[0101] Table 5

[0102]

[0103]

[0104] Examples 25-30

[0105] Examples 25-30 are prepared using the same method as in Example 1 for lithium chloride, except that the carbon dioxide introduction rate and the drying temperature of the lithium chloride solution are different. The specific parameters are shown in Table 6.

[0106] Table 6

[0107]

[0108] Examples 31-36

[0109] Examples 31-36 are prepared using the same method as in Example 1 for lithium chloride, except that the temperature and time for sodium removal are different. The specific parameters are shown in Table 7.

[0110] Table 7

[0111]

[0112]

[0113] Comparative Examples 1-2

[0114] The preparation methods of lithium chloride in Comparative Examples 1-2 and Example 1 are the same, except that the mass ratio of the lithium carbonate mixture to the lithium bicarbonate solution does not satisfy Equation 1. The specific parameters are shown in Table 8.

[0115] Table 8

[0116]

[0117] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, the present invention can obtain lithium chloride with high purity by controlling the mass ratio of lithium carbonate mixture to lithium bicarbonate solution, thus meeting the requirements of battery-grade anhydrous lithium chloride.

[0118] Comparative Example 3

[0119] The preparation method of lithium chloride in this comparative example includes the following steps:

[0120] 1) Mix 0.15 L of 2 mol / L hydrochloric acid (sodium content 0.5 mg / L) with 10 g of lithium carbonate (lithium carbonate content 99.7 wt%, sodium content 0.02%) and stir to produce an acidification reaction, resulting in a lithium chloride solution;

[0121] 2) The lithium chloride solution was evaporated and crystallized, washed, centrifuged, and dried at 120°C to obtain solid lithium chloride. Specific parameters are shown in Table 9.

[0122] Table 9

[0123]

[0124] As can be seen from the comparison between Example 1 and Comparative Example 3, the lithium chloride prepared by the method of the present invention has high purity and can meet the requirements of battery-grade anhydrous lithium chloride.

[0125] As can be seen from Tables 8 and 9, compared with the comparative example, the lithium chloride prepared by the method of the present invention has higher purity and can meet the requirements of battery-grade anhydrous lithium chloride.

[0126] 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 preparing lithium chloride, characterized in that, Includes the following steps: 1) After mixing and slurrying deionized water and lithium carbonate, carbon dioxide gas is introduced for carbonation treatment to obtain lithium bicarbonate solution; 2) The lithium bicarbonate solution is decomposed to obtain a mixture containing lithium carbonate, wherein the mass M of the mixture and the mass N of the lithium bicarbonate solution satisfy Equation 1. 0.14≤M / N≤0.90 Equation 1; 3) The mixture containing lithium carbonate is subjected to solid-liquid separation treatment to obtain refined lithium carbonate and decomposition mother liquor; 4) The refined lithium carbonate is acidified to obtain a lithium chloride solution; 5) The lithium chloride solution is solidified to obtain battery-grade lithium chloride; The decomposition process is carried out at a temperature of 70-100℃ and a stirring rate of 200-500 rpm. The carbon dioxide gas generated during the decomposition process is collected and returned to the carbonization process for recycling.

2. The method for preparing lithium chloride according to claim 1, characterized in that, The mass ratio of deionized water to lithium carbonate is (20-25):

1.

3. The method for preparing lithium chloride according to claim 2, characterized in that, In step 1), the lithium carbonate has a mass percentage content of not less than 99.5 wt% and a mass percentage content of sodium of 0.002%-0.1%.

4. The method for preparing lithium chloride according to claim 3, characterized in that, The sodium content in the battery-grade lithium chloride is ≤0.0015%.

5. The method for preparing lithium chloride according to any one of claims 1-4, characterized in that, The acidification treatment uses hydrochloric acid with a concentration of 0.1-12 mol / L.

6. The method for preparing lithium chloride according to claim 5, characterized in that, The sodium content in the hydrochloric acid is no higher than 0.5 mg / L.

7. The method for preparing lithium chloride according to any one of claims 1-4, characterized in that, The carbon dioxide gas is introduced at a rate of 0.02-4 L / min.

8. The method for preparing lithium chloride according to any one of claims 1-4, characterized in that, The curing process includes evaporation crystallization, washing, centrifugation and drying in sequence; The drying process is carried out at a temperature of 80-200℃.

9. The method for preparing lithium chloride according to any one of claims 1-4, characterized in that, The mother liquor is treated with a sodium removal agent to remove sodium, and recovered lithium carbonate is recycled to participate in the mixed slurry. The sodium removal agent includes Li 1+x Al x Ge 2-x (PO4)3, 0.2≤x≤0.5, wherein the sodium removal treatment is performed at a temperature of 50-80℃ for 5-20 hours.

Images