A method for recovering battery-grade lithium carbonate from lithium mica lithium extraction mother liquor

Abstract

This invention relates to the field of lithium carbonate recovery technology, specifically to a method for recovering lithium-ion mother liquor from lepidolite to prepare battery-grade lithium carbonate. The method includes the following steps: evaporating and concentrating the lepidolite mother liquor to precipitate mixed salts, followed by cooling to obtain a low-temperature slurry; subjecting the low-temperature slurry to carbonation and solid-liquid separation to obtain a primary separation mother liquor; cooling the primary separation mother liquor to precipitate sodium and performing solid-liquid separation to obtain a frozen liquid and sodium sulfate decahydrate; subjecting the frozen liquid to pyrolysis and solid-liquid separation to obtain crude lithium carbonate and a primary pyrolysis mother liquor; slurrying the crude lithium carbonate for carbonation, followed by pyrolysis to precipitate lithium carbonate, and then performing solid-liquid separation to obtain refined lithium carbonate; and finally, drying the refined lithium carbonate to obtain battery-grade lithium carbonate. This method effectively recovers carbonate and lithium from lepidolite extraction, with low recovery costs and high-purity lithium carbonate that meets the requirements for battery-grade lithium carbonate.

Description

Technical Field

[0001] This invention relates to the field of lithium carbonate recovery technology, specifically to a method for recovering lithium mica mother liquor to prepare battery-grade lithium carbonate. Background Technology

[0002] With the rapid development of the global new energy industry and the continuous expansion of the electric vehicle market, the demand for lithium, as a key raw material, has exploded. However, constrained by the limited availability of lithium resources and high processing costs, lithium carbonate prices remain high, hindering the healthy development of the new energy industry. The main production process for lithium carbonate involves adding sodium carbonate to lithium-containing brine extracted from lithium ore or salt lakes to precipitate lithium, thereby purifying it to produce battery-grade lithium carbonate. Since lithium carbonate is a slightly soluble substance, the residual Li₂O concentration in the lithium extraction mother liquor is 4 g / L to 7 g / L, requiring further recycling. Traditional processes typically involve decarbonation, evaporation, and freezing to separate sodium, potassium, and lithium salts. The lithium-containing frozen liquid is then returned to the precipitation process for further lithium carbonate production. The problems with traditional processes include low ion utilization, especially for sodium carbonate, which is only 60% to 80%, and residual CO₂ in the mother liquor. 2- The concentration of ions in lithium carbonate mother liquor is as high as 15g / L to 20g / L. Furthermore, the decarbonization process involves large quantities of sulfuric acid and liquid alkali. It is estimated that the cost of using lithium extraction mother liquor to recover ions for lithium carbonate production is 6000-7000 yuan / t, accounting for 40%-50% of the direct processing cost. Therefore, developing a process that can effectively recover ions from lithium extraction mother liquor at a low cost has become an urgent problem to be solved in the lithium carbonate industry. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering lithium extraction mother liquor from lepidolite to prepare battery-grade lithium carbonate. This method can effectively recover carbonate and lithium from lepidolite extraction, and has low recovery costs and produces high-purity lithium carbonate that meets the requirements for battery-grade lithium carbonate.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for recovering lithium extraction mother liquor from lepidolite to prepare battery-grade lithium carbonate includes the following steps: S1. The lithium extraction mother liquor from lepidolite is evaporated and concentrated to precipitate mixed salts, resulting in a high-temperature evaporated crystal slurry. The high-temperature evaporated crystal slurry is then cooled to obtain a low-temperature crystal slurry. S2. Carbon dioxide is introduced into the low-temperature crystal slurry to carry out a carbonization reaction to obtain carbonized crystal slurry. The carbonized crystal slurry is then separated into solid and liquid to obtain primary separation mother liquor and potassium-sodium mixed salt. S3. Cool the primary separation mother liquor to precipitate sodium, and perform solid-liquid separation to obtain frozen liquid and sodium sulfate decahydrate. Heat the frozen liquid to pyrolyze and precipitate lithium carbonate. After solid-liquid separation, crude lithium carbonate and primary pyrolysis mother liquor are obtained. S4. The crude lithium carbonate is slurried to obtain lithium carbonate slurry. Carbon dioxide is introduced into the lithium carbonate slurry to carry out carbonation reaction to obtain carbonized liquid. The carbonized liquid is heated and thermally decomposed to obtain lithium carbonate. After solid-liquid separation, refined lithium carbonate and secondary pyrolysis mother liquor are obtained. S5. Battery-grade lithium carbonate is obtained by drying high-quality lithium carbonate.

[0005] Furthermore, the concentrations of the main components of the lithium extraction mother liquor from lepidolite described in S1 are as follows: Li₂O concentration of 4 g / L to 10 g / L, potassium concentration of 1 g / L to 80 g / L, sodium concentration of 1 g / L to 130 g / L, and CO₃²⁻ concentration of 1 g / L to 10 g / L. 2- The concentration ranges from 1 g / L to 50 g / L.

[0006] Furthermore, the concentrations of the main components of the lithium extraction mother liquor from lepidolite described in S1 are as follows: Li₂O concentration of 4 g / L to 7 g / L, potassium concentration of 30 g / L to 60 g / L, sodium concentration of 30 g / L to 70 g / L, and CO₃²⁻ concentration of 10 g / L. 2- The concentration is 10 g / L to 40 g / L, and the pH value of the lithium extraction mother liquor from lepidolite is 10 to 14.

[0007] Furthermore, the density of the high-temperature evaporated crystal slurry described in S1 is 1 g / cm³. 3 ~2.0g / cm 3 The temperature of the high-temperature evaporation crystal slurry is 50℃~100℃; according to some preferred embodiments, the density of the high-temperature evaporation crystal slurry in S1 is 1.4g / cm³. 3 ~1.7g / cm 3 The temperature of the high-temperature evaporation crystal slurry is 85℃~100℃; Further, the temperature of the low-temperature crystal slurry in S1 is 10°C to 45°C. According to some preferred embodiments, the temperature of the low-temperature crystal slurry is 18°C ​​to 35°C.

[0008] Further, the carbonization reaction pressure in S2 is 0.01 MPa to 0.3 MPa, the carbonization reaction time is 0.5 h to 5 h, and the pH of the carbonized slurry is 8 to 10. According to some preferred embodiments, the carbonization reaction pressure in S2 is 0.05 MPa to 0.3 MPa, the carbonization time is 1 h to 5 h, and the pH of the carbonized slurry is 8 to 9.2.

[0009] After evaporating and concentrating the lithium extraction mother liquor from lepidolite to a certain density, it is cooled down. At this time, a large amount of mixed salt will precipitate out. Then, carbon dioxide is introduced into the low-temperature crystal slurry to convert the lithium carbonate in the mixed salt into lithium bicarbonate, which has good solubility. Sodium and potassium mixed salts are separated by solid-liquid separation.

[0010] The sodium-potassium mixed salt mainly consists of sodium sulfate and potassium sulfate, and contains a small amount of lithium. Furthermore, the sodium-potassium mixed salt described in S2 is recycled as a roasting aid for lepidolite. When used as a roasting aid, it can be mixed according to a formula of lepidolite concentrate: calcium sulfate: calcium carbonate: sodium-potassium sulfate mixed salt = 63:15:10:12, allowing the by-product sodium-potassium mixed salt to be reused and ensuring full utilization of its lithium content.

[0011] Further, the cooling temperature for sodium precipitation in step S3 is -20℃ to 5℃, and the Li₂O concentration in the frozen solution is 12g / L to 30g / L. According to some preferred embodiments, the cooling temperature for sodium precipitation in step S3 is -5℃ to 5℃, which further removes sodium salts. The separated sodium sulfate decahydrate, after purification, can be sold as a byproduct. The secondary separation mother liquor obtained by evaporating and separating the dissolved sodium sulfate decahydrate is returned to step S3 and mixed with the mother liquor for reuse.

[0012] Further, the temperature of the pyrolysis in S3 is 80℃~100℃, and the pyrolysis time is 1h~5h; according to some preferred embodiments, the temperature of the pyrolysis in S3 is 85℃~100℃, and the pyrolysis time is 1h~3h. Through the pyrolysis process, lithium bicarbonate is converted into lithium carbonate, and crude lithium carbonate can be obtained by solid-liquid separation.

[0013] The resulting primary pyrolysis mother liquor contains a significant amount of residual lithium, potassium, and sodium. Further, the primary pyrolysis mother liquor from S3 is returned to S1 and mixed with the lithium mica lithium extraction mother liquor for recycling. According to some preferred embodiments, the mixing volume ratio of the primary pyrolysis mother liquor from S3 to the lithium mica lithium extraction mother liquor is 1.5-2.5:10. Furthermore, the slurry preparation method in S4 is to prepare the crude lithium carbonate slurry using secondary pyrolysis mother liquor and / or water, and the liquid-to-solid ratio used for slurry preparation is 20-30:1. Furthermore, the slurry preparation method in S4 is to prepare the crude lithium carbonate slurry using a mixture of secondary pyrolysis mother liquor and water to obtain a lithium carbonate slurry. Furthermore, the ratio of the secondary pyrolysis mother liquor to water is 10 to 1:1.

[0014] Further, the carbonization reaction pressure in S4 is 0.001 MPa to 0.3 MPa, the carbonization reaction time is 0.5 h to 5 h, and the pH of the carbonized slurry is 8 to 10. According to a further preferred embodiment, the carbonization reaction pressure in S4 is 0.003 MPa to 0.12 MPa, the carbonization reaction time is 3 h to 5 h, and the pH of the carbonized slurry is 8.5 to 9.5. Further, the pyrolysis temperature in S4 is 80°C to 100°C, and the pyrolysis time is 1 h to 5 h. According to a further preferred embodiment, the pyrolysis temperature in S4 is 85°C to 95°C, and the pyrolysis time is 1.5 h to 3.5 h.

[0015] Furthermore, the wet lithium carbonate is dried in an oven at a temperature of 220℃ to 280℃ for 1 to 5 hours.

[0016] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention provides a method for recovering lithium extraction mother liquor from lepidolite to prepare battery-grade lithium carbonate. Using lepidolite lithium extraction mother liquor as raw material, the mother liquor is evaporated and concentrated to precipitate potassium and sodium salts and lithium carbonate. After cooling, carbon dioxide is introduced to dissolve the lithium carbonate in the slurry into lithium bicarbonate. For further pyrolysis purification, the principle that the solubility of potassium and sodium salts decreases sharply under freezing low-temperature conditions is utilized to preferentially separate the potassium and sodium salts from the solution. The frozen liquid is then purified again to produce battery-grade lithium carbonate. This method efficiently recovers residual lithium and carbonate ions from the lithium extraction mother liquor, the produced lithium carbonate meets battery-grade standards, and the byproduct potassium and sodium salts containing lithium can be used as calcination aids, improving the overall lithium yield. Furthermore, this process consumes only low-cost carbon dioxide and water during the recycling of battery-grade lithium carbonate, without the need for additional recycling reagents. The primary separation mother liquor, secondary separation mother liquor, primary pyrolysis mother liquor, and secondary pyrolysis mother liquor generated during the recycling process can all be returned to the system for reuse. No wastewater or solid waste is generated during the recycling process. The process is environmentally friendly and simple, making it easy to industrialize. It improves the lithium extraction yield from lepidolite and reduces the production cost of lithium extraction from lepidolite. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the lithium extraction mother liquor from lepidolite to prepare battery-grade lithium carbonate in the embodiments of this application. Detailed Implementation

[0018] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] The main components of the lithium extraction mother liquor from lepidolite in the following embodiments of this application are shown in Table 1 below: Table 1: Main components of lithium extraction mother liquor from lepidolite

[0020] Unless otherwise specified, all methods described herein are conventional methods, and all raw materials described herein are available from publicly available commercial sources.

[0021] Example 1 First-stage evaporation: 10m of the solution containing potassium sulfate, sodium sulfate, and lithium carbonate as listed in Table 1... 3 The lithium extraction mother liquor from lepidolite is transferred to an evaporator for evaporation and concentration, and mixed salts are precipitated. When the density of the crystal slurry reaches 1.5 g / cm³... 3 Discharge begins at that time, ultimately yielding 4.35m. 3 High-temperature evaporation crystal slurry at a temperature of 92℃; Cooling and temperature reduction: The high-temperature evaporated crystal paste is completely transferred to a cooler to be cooled to 23°C, thus obtaining a low-temperature crystal paste; Primary carbonization: The low-temperature crystal slurry is transferred to the carbonizer, stirring is started, and carbon dioxide is introduced to maintain the pressure inside the reactor at 0.25 MPa. After carbonization for 1.5 hours, when the online pH meter shows a pH value of 8.46, the pressure is released and the material is discharged to obtain the carbonized crystal slurry. The carbonized crystals are then separated by a centrifuge to obtain 4.08m³ crystals. 3 The primary separation mother liquor contained 12.75 g / L Li₂O, 40 g / L K, and 120 g / L Na. The potassium-sodium sulfate mixed salt weighed 1092 kg, containing 0.84% ​​Li₂O, 30.84% ​​K, and 10.11% Na. Sodium precipitation by freezing: 4.08m 3 The mother liquor from the primary separation was transferred to a cryogenic crystallizer for cooling and sodium precipitation. Once the crystal slurry temperature reached 0°C, it was transferred to a centrifuge for solid-liquid separation, yielding 2.12 ml of the solution. 3 The frozen solution contained 22.05 g / L Li₂O, 35 g / L K, and 40 g / L Na. 2832.68 kg of sodium sulfate decahydrate was produced. Further pulping, dissolving, and evaporating the sodium sulfate decahydrate yielded 1034 kg of potassium sodium sulfate mixed salt, containing 0.0051% Li₂O and 0.94 m³ of mother liquor from the sodium sulfate decahydrate evaporation. 3 The concentration of Li₂O was 5.5 g / L. First pyrolysis: 2.12m 3 After freezing, the liquid was transferred to a pyrolysis reactor, heated to 95°C, and held for 2 hours to precipitate lithium carbonate. After solid-liquid separation, 95.56 kg of crude lithium carbonate was obtained, with a main content of 97.76%, K content of 0.25%, Na content of 0.32%, and SO42-. 2- Content 1.16%. The volume of the mother liquor from the first pyrolysis was 1.978 m³.3 The concentrations of Li₂O, K, and Na were 4.57 g / L, 37.45 g / L, and 42.78 g / L, respectively. Carbonation and slurry preparation: 95.56 kg of crude lithium carbonate was added to 2.1 ml of deionized water at a liquid-to-solid ratio of 22:1. 3 ; Secondary carbonization: After carbonization and pulping, the pulp is transferred to a carbonizer. Carbon dioxide is introduced to maintain the pressure inside the reactor at 0.08 MPa. After carbonization for 4 hours, when the online pH meter shows a pH value of 9.33, the pressure is released and the pulp is discharged, yielding 2.12 m³ of material. 3 The solution after secondary carbonization has a Li2O concentration of 17.9 g / L. Secondary pyrolysis: After secondary carbonization, the liquid was heated to 90℃ and held at this temperature for 1.8 hours to precipitate lithium carbonate. After solid-liquid separation, 75.9 kg of wet refined lithium carbonate and 2.08 m³ of [unspecified product] were obtained. 3 The secondary pyrolysis mother liquor contained a Li₂O concentration of 4.32 g / L. Drying: The wet high-quality lithium carbonate was transferred into an oven and dried at 250℃ for 2 hours to obtain 71.42 kg of battery-grade lithium carbonate. The product specifications are shown in Table 2.

[0022] Example 2 1.978m in Example 1 3 First pyrolysis mother liquor and 10m 3 The lithium extraction mother liquor is mixed and then further recovered using this method.

[0023] First-stage evaporation: The mixed 12.1m 3 The mother liquor is transferred to an evaporator for evaporation and concentration, and mixed salts are precipitated. The concentration is reached when the slurry density reaches 1.67 g / cm³. 3 The material discharge begins at that time, ultimately yielding 3.6m. 3 High-temperature evaporation crystal slurry at a temperature of 98℃; Cooling and temperature reduction: The high-temperature evaporated crystal paste is completely transferred to a cooler to be cooled to 32°C to obtain a low-temperature crystal paste; Primary carbonization: The low-temperature crystal slurry is transferred to the carbonizer, stirring is started, and carbon dioxide is introduced to maintain the pressure inside the reactor at 0.05 MPa. After carbonization for 5 hours, when the online pH meter shows a pH value of 9.02, the pressure is released and the material is discharged to obtain the carbonized crystal slurry. The carbonized crystal slurry is then separated by a centrifuge to obtain 2.99 m³ of the slurry. 3 The primary separation mother liquor contained 15.275 g / L Li₂O, 40.3 g / L K, and 118.5 g / L Na. The potassium-sodium sulfate mixed salt weighed 2020.12 kg, containing 1.22% Li₂O, 22.5% K, and 16.14% Na. Sodium precipitation by freezing: 2.99m 3The mother liquor from the primary separation was transferred to a cryo-crystallizer for cooling and sodium precipitation. Once the crystallizer reached 5°C, it was transferred to a centrifuge for solid-liquid separation, yielding 1.79 m³ of sodium crystals. 3 The frozen liquid contained 22.91 g / L Li₂O, 35 g / L K, and 40 g / L Na. 2008.5 kg of sodium sulfate decahydrate was produced. Further pulping, dissolving, and evaporating the sodium sulfate decahydrate yielded 634.65 kg of potassium sodium sulfate mixed salt, containing 0.0072% Li₂O and 0.82 ml of sodium sulfate decahydrate evaporation mother liquor. 3 The concentration of Li₂O was 5.3 g / L. First pyrolysis: 1.79m 3 After freezing, the liquid was transferred to a pyrolysis reactor, heated to 85°C, and held at this temperature for 1 hour to precipitate lithium carbonate. After solid-liquid separation, 81.25 kg of crude lithium carbonate was obtained, with a main content of 98.21%, K content of 0.2%, Na content of 0.33%, and SO4 content of [missing information]. 2- Content 1.33%. The volume of the mother liquor from the first pyrolysis was 1.778 m³. 3 The concentrations of Li₂O, K, and Na were 4.84 g / L, 35.21 g / L, and 40.2 g / L, respectively. Carbonation and slurry preparation: 81.25 kg of crude lithium carbonate was added to 1.63 ml of deionized water at a liquid-to-solid ratio of 20:1. 3 ; Secondary carbonization: After carbonization and pulping, the pulp is transferred to a carbonizer. Carbon dioxide is introduced to maintain the pressure inside the reactor at 0.003 MPa. After carbonization for 5 hours, when the online pH meter shows a pH value of 8.57, the pressure is released and the pulp is discharged, yielding 1.66 m³ of pulp. 3 The solution after secondary carbonization has a Li2O concentration of 19.57 g / L. Secondary pyrolysis: After secondary carbonization, the liquid was heated to 90℃ and held at this temperature for 3 hours to precipitate lithium carbonate. After solid-liquid separation, 66.74 kg of wet refined lithium carbonate and 1.62 m³ of [unclear - possibly referring to a specific product or solution] were obtained. 3 The secondary pyrolysis mother liquor contained a Li₂O concentration of 4.38 g / L. Drying: The wet high-quality lithium carbonate was transferred into an oven and dried at 250℃ for 2 hours to obtain 63.08 kg of battery-grade lithium carbonate. The product specifications are shown in Table 2.

[0024] Example 3 The 2020.12 kg of potassium sodium sulfate (with a Li2O content of 1.22%) from Example 2 was reused as a calcination aid for lepidolite.

[0025] The following mixtures were prepared: lithium mica concentrate: calcium sulfate: calcium carbonate: potassium sodium sulfate mixed salt = 63:15:10:12. 63 kg of lithium mica concentrate (Li₂O content 1.976%), 15 kg of calcium sulfate, 10 kg of calcium carbonate, and 12 kg of potassium sodium sulfate mixed salt were mixed thoroughly and roasted for later use.

[0026] The mixed material was placed into a sagger and put into a high-temperature furnace. The temperature of the high-temperature furnace was adjusted to 1000℃ and kept at that temperature for 1 hour. After the high-temperature furnace was turned off, the material was taken out and crushed after cooling to room temperature. 95.25 kg of clinker was obtained by weighing.

[0027] The obtained clinker was added to 95L of water at a liquid-to-solid ratio of 1, stirred for 1 hour, and then filtered under pressure to obtain 82.53kg of leaching residue and 80.76L of leachate. The metal balance data of this example are shown in Table 3.

[0028] Table 2: Main Components of Battery-Grade Lithium Carbonate Produced in Examples

[0029] Table 3: Metal Balance Table for Example 3

[0030] This invention presents a technology for recovering lithium from lithium extraction mother liquor to prepare battery-grade lithium carbonate. It eliminates the consumption of sodium carbonate, liquid alkali, and sulfuric acid, reducing production costs by 40-50%. The resulting lithium-encapsulated potassium and sodium salts are further recycled as calcination aids for lepidolite, improving lithium recovery. This method not only enhances the lithium recovery rate from lepidolite lithium extraction mother liquor but also effectively recovers carbonate ions from the mother liquor. The prepared lithium carbonate product meets battery-grade standards (YS / T582-2013). This method features a simple production process, low recovery costs, and ease of industrialization, significantly improving the utilization rate of carbonate and lithium ions in the lithium extraction mother liquor.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and not to limit them; although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of this application or equivalent substitutions can be made to some technical features, all of which should be covered within the scope of the technical solutions claimed in this application.

Claims

1. A method for recovering battery grade lithium carbonate from lithium mica lithium extraction mother liquor, characterized in that, Includes the following steps: S1. The lithium extraction mother liquor from lepidolite is evaporated and concentrated to precipitate mixed salts, resulting in a high-temperature evaporated crystal slurry. This high-temperature evaporated crystal slurry is then cooled to obtain a low-temperature crystal slurry. The concentrations of the main components of the lithium extraction mother liquor from lepidolite in S1 are: Li₂O concentration 4 g / L–7 g / L, potassium concentration 30 g / L–60 g / L, sodium concentration 30 g / L–70 g / L, and CO₃²⁻. 2- The concentration is 10 g / L to 40 g / L, and the pH value of the lithium extraction mother liquor from lepidolite is 10 to 14; the density of the high-temperature evaporation crystal slurry in S1 is 1 g / cm³. 3 ~2.0g / cm 3 The temperature of S1 high-temperature evaporation crystal paste is 50℃~100℃; the temperature of low-temperature crystal paste is 10℃~45℃. S2. Carbon dioxide is introduced into the low-temperature crystal slurry to carry out a carbonization reaction to obtain a carbonized crystal slurry. The carbonized crystal slurry is then subjected to solid-liquid separation to obtain a primary separation mother liquor and a potassium-sodium mixed salt. The potassium-sodium mixed salt in S2 is used as a calcination aid for lepidolite. The pressure of the carbonization reaction in S2 is 0.01MPa to 0.3MPa, the carbonization reaction time is 0.5h to 5h, and the pH of the carbonized crystal slurry is 8 to 10. S3. The mother liquor from the primary separation is cooled to precipitate sodium, and solid-liquid separation is performed to obtain a frozen liquid and sodium sulfate decahydrate. The frozen liquid is then heated to pyrolyze to precipitate lithium carbonate. After solid-liquid separation, crude lithium carbonate and a primary pyrolysis mother liquor are obtained. The temperature for cooling to precipitate sodium in S3 is -20℃ to 5℃, and the concentration of Li2O in the frozen liquid is 12g / L to 30g / L. The temperature for pyrolysis in S3 is 80℃ to 100℃, and the pyrolysis time is 1h to 5h. The primary pyrolysis mother liquor from S3 is returned to S1 and mixed with the lithium mica lithium extraction mother liquor. S4. The crude lithium carbonate is slurried to obtain lithium carbonate slurry. Carbon dioxide is introduced into the lithium carbonate slurry to carry out carbonation reaction to obtain carbonized liquid. The carbonized liquid is heated and thermally decomposed to obtain lithium carbonate. After solid-liquid separation, refined lithium carbonate and secondary pyrolysis mother liquor are obtained. S5. Battery-grade lithium carbonate is obtained by drying high-quality lithium carbonate.

2. The method for preparing battery-grade lithium carbonate from lithium mica mother liquor according to claim 1, characterized in that, The slurry preparation method in S4 is to prepare crude lithium carbonate slurry using secondary pyrolysis mother liquor and / or water, with a liquid-to-solid ratio of 20 to 30:

1.

3. The method for preparing battery-grade lithium carbonate from lithium mica mother liquor according to claim 2, characterized in that, The slurry preparation method in S4 is to prepare crude lithium carbonate slurry by mixing it with a mixture of secondary pyrolysis mother liquor and water.

4. The method for preparing battery-grade lithium carbonate by recovering lithium mica mother liquor according to claim 3, characterized in that, The ratio of secondary pyrolysis mother liquor to water is 10 to 1:

1.

5. The method for preparing battery-grade lithium carbonate from lithium mica mother liquor according to claim 1, characterized in that, The carbonization reaction described in S4 is carried out at a pressure of 0.001 MPa to 0.3 MPa, for a reaction time of 0.5 h to 5 h, and the pH of the carbonized solution is 8 to 10.

6. The method for preparing battery-grade lithium carbonate by recovering lithium mica mother liquor according to claim 1, characterized in that, The pyrolysis temperature described in S4 is 80℃~100℃, and the pyrolysis time is 1h~5h.

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