Method for preparing battery-grade lithium carbonate from brine lithium carbonate

Abstract

A method for preparing battery-grade lithium carbonate from brine lithium carbonate, comprising the following steps: dissolving brine lithium carbonate to obtain a lithium-containing solution, and adding an extraction agent into the lithium-containing solution to perform extraction, to obtain an extraction solution and a raffinate; performing reverse extraction on the extraction solution to obtain a reverse extraction solution, and performing lithium precipitation processing or pyrolysis on the reverse extraction solution, to obtain battery-grade lithium carbonate, the extractant comprising a β-diketone and a co-extraction agent.

Description

A method for preparing battery-grade lithium carbonate from brine lithium carbonate Technical Field

[0001] The present invention belongs to the technical field of lithium extraction from salt lakes, and particularly relates to a method for preparing battery-grade lithium carbonate from brine lithium carbonate. Background Art

[0002] With the rapid adoption of lithium-ion batteries, lithium, a key element in these batteries, has attracted increasing attention from the industry. Lithium salt products, such as lithium carbonate and lithium hydroxide, are already in short supply, with prices remaining high. According to relevant statistics, salt lake brine lithium reserves account for approximately 70% of total lithium resources. Therefore, lithium extraction from salt lakes will inevitably become the primary focus of lithium salt production, making further development of salt lake lithium resources extremely urgent.

[0003] Salt lake brine has a complex composition, containing not only metallic elements like calcium, magnesium, and potassium, but also non-metallic elements like silicon, boron, and sulfur. Brine-derived lithium carbonate is produced by removing impurities from salt lake brine, which often contains significant amounts of boron impurities. The current purification process for brine-derived lithium carbonate is complex, energy-intensive, and consumes significant amounts of acid and alkali during the treatment process. Therefore, a low-cost, simple process for producing battery-grade lithium carbonate is urgently needed.

[0004] Summary of the Invention

[0005] This disclosure aims to provide a technology for purifying brine lithium carbonate. To this end, this disclosure proposes a method for preparing battery-grade lithium carbonate from brine lithium carbonate. This method is simple and environmentally friendly, effectively separating boron impurities and purifying lithium carbonate through extraction, without consuming liquid caustic soda and at a low cost, to obtain battery-grade lithium carbonate through a single-step stripping process.

[0006] According to a first aspect of the present disclosure, a method for preparing battery-grade lithium carbonate from brine lithium carbonate is proposed, comprising the following steps:

[0007] S1: dissolving lithium carbonate in brine to obtain a lithium-containing solution, adding an extractant to the lithium-containing solution for extraction to obtain an extract and a raffinate;

[0008] S2: stripping the extract to obtain a stripping solution, and subjecting the stripping solution to lithium precipitation or thermal decomposition to obtain battery-grade lithium carbonate;

[0009] Wherein, the extractant includes β-diketone and a co-extractant.

[0010] In some embodiments, the β-diketone is at least one of acetylacetone, propionylbutanone, or butyrylvalerone.

[0011] In some embodiments, the co-extractant is at least one of tri-n-octylphosphine oxide, tributylphosphine oxide, or triphenylphosphine oxide.

[0012] In some embodiments, the mass ratio of β-diketone to co-extractant in the extractant is 1:2-1:3.

[0013] In some embodiments, the organic loading of the extractant is about 2.5 g / L.

[0014] In some embodiments, in step S1, the lithium concentration in the lithium-containing solution is 1.5-2 g / L.

[0015] In some embodiments, in step S1, the volume ratio of the organic phase to the aqueous phase during the extraction process is (2.5-3.3):1.

[0016] In some embodiments, in step S1, the lithium concentration of the raffinate is 0.75-1 g / L.

[0017] Under alkaline conditions, during the extraction of lithium carbonate from brine, the β-diketone structure first undergoes an enol transformation, followed by Li / H substitution, to produce carbon dioxide, water, and lithium bicarbonate. Because this reaction is reversible, the addition of a co-extraction agent can ensure the stability of the lithium extraction process.

[0018] In some embodiments, in step S1, the raffinate is evaporated, concentrated, and pyrolyzed, followed by solid-liquid separation to obtain lithium carbonate solid. The lithium carbonate solid obtained in this process is dissolved and used as a lithium-containing solution for lithium extraction. The mother liquor obtained after solid-liquid separation is regularly discharged to remove boron.

[0019] In some embodiments, in step S1, the raffinate is evaporated and concentrated, pyrolyzed, and then solid-liquid separation is performed to obtain a mother liquor which is discharged, and the boron concentration in the mother liquor is 50-80 mg / L.

[0020] In some embodiments, the concentration of boron in the mother liquor is 50 mg / L.

[0021] In some embodiments, in step S2, the stripping is carried out using acid or carbon dioxide.

[0022] In some embodiments, the acid solution is at least one of hydrochloric acid or sulfuric acid. When hydrochloric acid is used for stripping, the stripping solution is a solution containing lithium chloride; when sulfuric acid is used for stripping, the stripping solution is a solution containing lithium sulfate.

[0023] In some embodiments, the concentration of the acid solution is 2-5 mol / L.

[0024] In some embodiments, the volume ratio of the extract to the acid solution is 1:1-1:3.

[0025] In some embodiments, when carbon dioxide is used for stripping, the flow rate of carbon dioxide is 5-10 L / min and the time is 2-3 hours. Carbon dioxide is introduced for stripping, and the stripping solution is lithium bicarbonate solution.

[0026] In some embodiments, in step S2, when the stripping is performed using an acid solution, the lithium precipitation process is as follows: mixing the stripping solution with a carbonate solution to generate a lithium carbonate precipitate.

[0027] In some embodiments, the stripping solution is fed simultaneously with the carbonate solution.

[0028] In some embodiments, the concentration of the carbonate is 250-350 g / L; the amount of the carbonate solution used is 1.1-1.25 times the amount of lithium in the stripping solution on a molar basis.

[0029] In some embodiments, the carbonate solution is at least one of a sodium carbonate solution or a potassium carbonate solution.

[0030] In some embodiments, the carbonate solution is a sodium carbonate solution. The sodium chloride and sodium sulfate produced by the carbonization reaction are highly soluble and can be washed away by water, with little impact on the sodium or sulfate impurities in the lithium carbonate product.

[0031] In some embodiments, in step S2, when carbon dioxide is used for stripping, the pyrolysis process is: heating and decomposing the stripping solution to generate lithium carbonate precipitate.

[0032] In some embodiments, the temperature of the thermal decomposition is 80-100°C.

[0033] In some embodiments, the thermal decomposition temperature is about 90°C.

[0034] In some embodiments, the heating decomposition time is 1-3 hours.

[0035] In some embodiments, in step S2, the stripping solution is subjected to lithium precipitation treatment or pyrolysis to obtain a lithium precipitation mother liquor, and the lithium precipitation mother liquor is returned to step S1 to be mixed with the lithium-containing solution.

[0036] According to a second aspect of the present disclosure, a method for preparing a lithium-ion battery is provided, comprising the steps of the method described in the first aspect of the present disclosure.

[0037] According to a third aspect of the present disclosure, an application of the method described in the first aspect of the present disclosure in the preparation of a lithium-ion battery is proposed.

[0038] The boron removal principle of the method for preparing battery-grade lithium carbonate from brine lithium carbonate described in the first aspect of the present disclosure is as follows:

[0039] Typically, extractants require specific pH conditions for their extraction function, requiring the addition of alkali to adjust the pH to the desired level before extraction. This process requires the addition of a large amount of alkali. The extractant employed in the present disclosure can be activated by adding alkali or alkaline carbonates. However, the solution being extracted can provide carbonate ions to activate the extractant, eliminating the need for additional alkali. The extraction process is a reversible reaction, and its equilibrium constant limits the chemical reaction.

[0040] The present invention first dissolves lithium carbonate in brine to obtain brine lithium liquid, adds β-diketone + synergistic extraction system to extract lithium from the lithium liquid, and about half of the lithium is extracted into an organic phase. After back extraction and other treatments, battery-grade lithium carbonate is obtained; the remaining lithium remains in the raffinate, and the lithium in the raffinate is evaporated, concentrated and thermally decomposed to obtain lithium carbonate. The lithium carbonate is redissolved and cyclically extracted to extract lithium, and the evaporated mother liquor is regularly discharged to achieve the purpose of removing boron.

[0041] According to one embodiment of the present disclosure, there are at least the following beneficial effects:

[0042] (1) The present invention utilizes extraction to effectively separate boron impurities and purify lithium carbonate. The extraction process does not consume liquid alkali, thereby reducing the overall process cost.

[0043] (2) After stripping, the stripping solution is directly heated or carbonate is added to obtain battery-grade lithium carbonate in one step, which is a simple process. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The present disclosure is further described below with reference to the accompanying drawings and embodiments, wherein:

[0045] FIG1 is a process flow chart of the method for preparing battery-grade lithium carbonate from brine lithium carbonate according to Example 1 of the present disclosure. DETAILED DESCRIPTION

[0046] The following will clearly and completely describe the concept and technical effects of the present disclosure in conjunction with the examples to fully understand the purpose, features and effects of the present disclosure. The β-diketone and trialkylphosphine oxide used in the present disclosure are both selected from MacLean reagents.

[0047] Example 1

[0048] A method for preparing battery-grade lithium carbonate from brine lithium carbonate, referring to Figure 1, the specific process is as follows:

[0049] S1: Dissolve 200 g of brine lithium carbonate in 20 L of water to obtain a lithium solution with a Li content of 1.85 g / L;

[0050] S2: adding 50 L of an extractant (16 L of acetylacetone and 34 L of tri-n-octylphosphine oxide) to the obtained lithium solution and stirring to perform mixed extraction, and obtaining a lithium solution containing the extractant and a lithium bicarbonate raffinate after extraction and separation;

[0051] S3: The lithium solution containing the extractant is passed through 5 L / min of carbon dioxide gas for stripping for 1 hour;

[0052] S4: After stripping, the extractant and the stripping solution are separated. The stripping solution is a lithium bicarbonate solution. The lithium bicarbonate solution is heated to 95° C. for pyrolysis for 2 hours. After the heating is completed, the solution is filtered, washed, and dried to obtain battery-grade lithium carbonate.

[0053] S5: The raffinate in step S2 is evaporated and concentrated 5 times at 90°C. The evaporation and concentration process is accompanied by the decomposition of lithium bicarbonate. After centrifugal filtration, lithium carbonate solid is obtained. According to the ratio of steps S1 and S2, the lithium carbonate solid is redissolved in water to form lithium liquid. An extractant is added for cyclic extraction. The evaporated mother liquor is sampled and tested. The boron content is 50-80ppm, and B is regularly discharged.

[0054] The brine lithium carbonate of this embodiment, its composition after dissolution, and the battery-grade lithium carbonate obtained by thermal decomposition after stripping were detected by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorption spectrophotometry. The test results are shown in Table 1.

[0055] Table 1 Composition and extraction rate of brine lithium carbonate, lithium liquid, and product battery-grade lithium carbonate

[0056] Example 2

[0057] A method for preparing battery-grade lithium carbonate from brine lithium carbonate, the specific process is as follows:

[0058] S1: Dissolve 200 g of brine lithium carbonate in 20 L of water to obtain a lithium solution with a Li content of 1.79 g / L;

[0059] S2: adding 56 L of an extractant (18 L of acetylacetone and 38 L of tri-n-octylphosphine oxide) to the obtained lithium solution and stirring to perform mixed extraction, and obtaining a lithium solution containing the extractant and a lithium bicarbonate raffinate after extraction and separation;

[0060] S3: The lithium solution containing the extractant is passed through 5 L / min of carbon dioxide gas for stripping for 1 hour;

[0061] S4: After stripping, the extractant and the stripping solution are separated. The stripping solution is a lithium bicarbonate solution. The lithium bicarbonate solution is heated to 95° C. for pyrolysis for 2 hours. After the heating is completed, the solution is filtered, washed, and dried to obtain battery-grade lithium carbonate.

[0062] S5: The raffinate in step S2 is evaporated and concentrated 5 times at 90°C. The evaporation and concentration process is accompanied by the decomposition of lithium bicarbonate. After centrifugal filtration, lithium carbonate solid is obtained. According to the ratio of steps S1 and S2, the lithium carbonate solid is redissolved into lithium liquid, and an extractant is added for cyclic extraction. The evaporated mother liquor is sampled and tested. The boron content is 50-80ppm, and B is regularly discharged.

[0063] The brine lithium carbonate of this embodiment, the lithium solution after dissolution, and the battery-grade lithium carbonate obtained by thermal decomposition after stripping were detected by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorption spectrophotometry. The test results are shown in Table 2.

[0064] Table 2 Composition and extraction rate of brine lithium carbonate, lithium liquid, and product battery-grade lithium carbonate

[0065] Example 3

[0066] A method for preparing battery-grade lithium carbonate from brine lithium carbonate, the specific process is as follows:

[0067] S1: Dissolve 200 g of brine lithium carbonate in 20 L of water to obtain a lithium solution with a Li content of 1.72 g / L;

[0068] S2: adding 54 L of an extractant (17 L of propionyl butanone and 37 L of tri-n-octylphosphine oxide) to the obtained lithium solution and stirring to perform mixed extraction, and obtaining a lithium solution containing the extractant and a lithium bicarbonate raffinate after extraction and separation;

[0069] S3: Add 60L 2.5mol / L hydrochloric acid to the lithium solution containing the extractant for stripping;

[0070] S4: After stripping, the extractant and the stripping solution are separated. The stripping solution is a lithium chloride solution. The lithium chloride solution and 0.21L 280g / L soda ash are simultaneously added to the reactor to precipitate lithium. After the reaction is completed, the solution is filtered, washed, and dried to obtain battery-grade lithium carbonate.

[0071] S5: The raffinate in step S2 is evaporated and concentrated 6 times at 90°C. The evaporation and concentration process is accompanied by the decomposition of lithium bicarbonate. After centrifugal filtration, lithium carbonate solid is obtained. According to the ratio of steps S1 and S2, the lithium carbonate solid is redissolved into lithium liquid, and an extractant is added for cyclic extraction. The evaporated mother liquor is sampled and tested. The boron content is 50-80ppm, and B is regularly discharged.

[0072] The brine lithium carbonate of this embodiment, the lithium solution after dissolution, and the battery-grade lithium carbonate obtained by thermal decomposition after stripping were detected by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorption spectrophotometry. The test results are shown in Table 3.

[0073] Table 3 Composition and extraction rate of brine lithium carbonate, lithium liquid, and product battery-grade lithium carbonate

[0074] Example 4

[0075] A method for preparing battery-grade lithium carbonate from brine lithium carbonate, the specific process is as follows:

[0076] S1: Dissolve 200 g of brine lithium carbonate in 20 L of water to obtain a lithium solution with a Li content of 1.81 g / L;

[0077] S2: adding 52 L of an extractant (16 L of propionyl butanone and 36 L of tri-n-octylphosphine oxide) to the obtained lithium solution and stirring to perform mixed extraction, and obtaining a lithium solution containing the extractant and a lithium bicarbonate raffinate after extraction and separation;

[0078] S3: Add 65L 3mol / L sulfuric acid to the lithium solution containing the extractant for stripping;

[0079] S4: After stripping, the extractant and the stripping solution are separated. The stripping solution is a lithium sulfate solution. The lithium sulfate solution and 0.25L 320g / L soda ash are simultaneously added to the reactor to precipitate lithium. After the reaction is completed, the solution is filtered, washed, and dried to obtain battery-grade lithium carbonate.

[0080] S5: The raffinate in step S2 is evaporated and concentrated 5 times at 90°C. The evaporation and concentration process is accompanied by the decomposition of lithium bicarbonate. After centrifugation, lithium carbonate solid is obtained. According to the ratio of steps S1 and S2, the lithium carbonate solid is redissolved into lithium liquid, and an extractant is added for cyclic extraction. The evaporated mother liquor is sampled and tested. The boron content is 50-80ppm, and B is regularly discharged.

[0081] The brine lithium carbonate of this embodiment, the lithium solution after dissolution, and the battery-grade lithium carbonate obtained by thermal decomposition after stripping were detected by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorption spectrophotometry. The test results are shown in Table 4.

[0082] Table 4 Composition and extraction rate of brine lithium carbonate, lithium liquid, and product battery-grade lithium carbonate

[0083] Comparative Example 1

[0084] S1: Dissolve 200 g of brine lithium carbonate in 20 L of water to obtain a lithium solution with a Li content of 1.81 g / L;

[0085] S2: adding 52 L of acetylacetone extractant to the obtained lithium solution and stirring to perform mixed extraction, and obtaining a lithium solution containing the extractant and a lithium bicarbonate raffinate after extraction and separation;

[0086] S3: Add 65L 3mol / L sulfuric acid to the lithium solution containing the extractant for stripping;

[0087] S4: After stripping, the extractant and the stripping solution are separated. The stripping solution is a lithium sulfate solution. The lithium sulfate solution and 0.20 L 320 g / L soda ash are simultaneously added to the reactor to precipitate lithium. After the reaction is completed, the solution is filtered, washed, and dried to obtain battery-grade lithium carbonate.

[0088] S5: The raffinate in step S2 is evaporated and concentrated 5 times at 90°C. The evaporation and concentration process is accompanied by the decomposition of lithium bicarbonate. After centrifugation, lithium carbonate solid is obtained. According to the ratio of steps S1 and S2, the lithium carbonate solid is redissolved into lithium liquid, and β-diketone extractant is added for cyclic extraction. The evaporated mother liquor is sampled and tested. The boron content is 50-80ppm, and B is regularly discharged.

[0089] The comparative example brine lithium carbonate, the lithium solution after dissolution, and the lithium carbonate obtained by thermal decomposition after stripping were detected by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic absorption spectrophotometer. The test results are shown in Table 5.

[0090] Table 5 Composition and extraction rate of brine lithium carbonate, lithium liquid, and product battery-grade lithium carbonate

[0091] In Comparative Example 1, only β-diketone extractant was used without adding a co-extractant. On the one hand, the stability of the extracted lithium was poor, and the selection of lithium extraction also had a certain impact. The concentration of lithium obtained after stripping was low, resulting in a relatively low purity of the lithium carbonate product obtained by lithium precipitation or thermal decomposition, and an increase in the impurity content.

Claims

1. A method for preparing battery-grade lithium carbonate from brine lithium carbonate, characterized in that: The following steps are involved: S1: dissolving lithium carbonate in brine to obtain a lithium-containing solution, adding an extractant to the lithium-containing solution for extraction to obtain an extract and a raffinate; S2: stripping the extract to obtain a stripping solution, and obtaining battery-grade lithium carbonate by lithium precipitation or pyrolysis of the stripping solution; Wherein, the extractant comprises β-diketone and a co-extractant.

2. The method according to claim 1, characterized in that The β-diketone is at least one of acetylacetone, propionylbutanone or butyrylvalerone.

3. The method according to claim 1, characterized in that The synergistic extractant is at least one of tri-n-octylphosphine oxide, tributylphosphine oxide or triphenylphosphine oxide.

4. The method according to claim 1, characterized in that: The mass ratio of β-diketone to co-extraction agent in the extractant is 1:2-1:

3.

5. The method according to claim 1, characterized in that In step S1, the lithium concentration in the lithium-containing solution is 1.5-2 g / L.

6. The method according to claim 1, characterized in that In step S1, the volume ratio of the organic phase to the aqueous phase during the extraction process is (2.5-3.3):

1.

7. The method according to claim 1, characterized in that In step S2, the stripping adopts acid solution or carbon dioxide.

8. The method according to claim 7, characterized in that The acid solution is at least one of hydrochloric acid or sulfuric acid.

9. The method according to claim 7, characterized in that: The concentration of the acid solution is 2-5 mol / L.

10. The method according to claim 7, characterized in that The volume ratio of the extract to the acid solution is 1:1-1:

3.

11. The method according to claim 7, characterized in that When carbon dioxide is used for the stripping, the flow rate of carbon dioxide is 5-10 L / min and the time is 2-3 h.

12. The method according to claim 7, characterized in that In step S2, when the stripping is performed using an acid solution, the lithium precipitation process is as follows: mixing the stripping solution with a carbonate solution to generate lithium carbonate precipitate.

13. The method according to claim 7, characterized in that In step S2, when carbon dioxide is used for the stripping, the pyrolysis process is: heating and decomposing the stripping solution to generate lithium carbonate precipitate.

14. The method according to claim 13, characterized in that The temperature of the heating decomposition is 80-100°C.

15. A method for preparing a lithium ion battery, comprising the steps of the method according to any one of claims 1 to 14.

16. Use of the method according to any one of claims 1 to 14 in preparing lithium ion batteries.

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