A method for the intensified short-path production of battery-grade lithium carbonate from carbonization

Abstract

The application provides a method for preparing battery-grade lithium carbonate by shortening carbonization, comprising the following steps: preparing a lithium hydroxide solution, adding a surfactant, filtering through a microporous filter to obtain a refined lithium hydroxide solution; introducing industrial-grade carbon dioxide into the refined lithium hydroxide solution at a certain gas flow rate, performing a carbonization reaction, then performing solid-liquid separation and washing to obtain a carbonized solution and a wet residue, and drying and crushing the wet residue to obtain battery-grade lithium carbonate. The method can improve the carbonization efficiency and the utilization rate of carbon dioxide, and has the advantages of short process, simple operation, low cost, green environmental protection and the like, and is helpful to cope with the situation that the demand for battery-grade lithium carbonate is greater than that for battery-grade lithium hydroxide, and has considerable industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of lithium carbonate preparation technology, and particularly relates to a method for enhancing short-range carbonation preparation of battery-grade lithium carbonate. Background Technology

[0002] Lithium-ion batteries are the primary power batteries for new energy vehicles, and the lithium salt industry has attracted significant attention. Lithium carbonate and lithium hydroxide are both basic industrial products of lithium and are widely used in lithium-ion batteries, pharmaceuticals, and aerospace. Currently, the mainstream cathode materials for lithium-ion power batteries are lithium iron phosphate and high-nickel ternary cathode materials. Lithium iron phosphate uses battery-grade lithium carbonate as its lithium source, while high-nickel ternary cathode materials use battery-grade lithium hydroxide. Due to its safety and manufacturing cost advantages, lithium iron phosphate cathode materials have surpassed high-nickel ternary cathode materials in market share. Consequently, the market demand for battery-grade lithium hydroxide has gradually decreased, while the demand for battery-grade lithium carbonate has gradually increased. Since May 2023, the price of battery-grade lithium carbonate has surpassed that of battery-grade lithium hydroxide.

[0003] Driven by market prices, the production of battery-grade lithium carbonate has surged. However, battery-grade lithium carbonate has strict requirements for lithium content and impurities, and is usually prepared using industrial-grade lithium salts as raw materials. Currently, industrial methods for producing battery-grade lithium carbonate include hydrogenation pyrolysis, bipolar membrane carbonation, and causticization carbonation. Chinese patent document CN 115286017 A discloses a method for preparing battery-grade lithium carbonate, which utilizes the carbonation and hydrogenation reaction of carbon dioxide and crude lithium carbonate solution to obtain lithium bicarbonate solution. The lithium bicarbonate solution is then pyrolyzed to obtain battery-grade lithium carbonate. However, this technology suffers from difficult-to-control pyrolysis, significant lithium loss, and low carbonation and hydrogenation efficiency. Chinese patent document CN 107298450 B discloses a method for preparing lithium hydroxide and lithium carbonate using a soluble lithium salt solution. This method uses a bipolar membrane electrodialysis device to electrolyze the soluble lithium salt solution, obtaining a lithium hydroxide solution at the cathode, which is then carbonized to obtain high-purity lithium carbonate. This method involves a complex electrodialysis system, expensive membrane materials, and low efficiency in the lithium hydroxide carbonation process.

[0004] The carbonized liquid still contains lithium. Current treatment technologies for this liquid mainly include lithium carbonate-phosphate precipitation, extraction, and adsorption. Extraction and adsorption methods utilize lithium extractants and lithium-ion sieves to selectively extract lithium from the carbonized liquid, offering high lithium selectivity. However, the recovery and reuse of extractants and ion sieves are difficult and costly, hindering industrial development. Lithium carbonate-phosphate precipitation remains the most widely used treatment technology. Chinese patent document CN 104925837 A discloses a method for recovering battery-grade lithium carbonate precipitation mother liquor to prepare lithium salts. This method utilizes lithium phosphate precipitation, achieving a high lithium yield, but faces environmental and cost pressures related to phosphorus-containing wastewater treatment.

[0005] The preparation of battery-grade lithium carbonate using lithium hydroxide solution via carbonation is a commonly used industrial method. However, the carbonation process is time-consuming, inefficient, and the utilization rate of carbon dioxide needs improvement. Currently, the market demand for battery-grade lithium carbonate is greater than that for battery-grade lithium hydroxide, but efficient conversion methods are lacking. Therefore, developing a new technology for short-range, enhanced carbonation preparation of battery-grade lithium carbonate is of great practical significance. Summary of the Invention

[0006] To address the above problems, this invention provides a method for enhancing short-range carbonization to prepare battery-grade lithium carbonate.

[0007] To achieve the above objectives, this application proposes the following solution:

[0008] This method mainly includes three steps: preparation of refined solution, carbonation, and post-carbonation liquid treatment. Addressing the technical problems of long carbonation time and low efficiency in the existing technology of preparing lithium carbonate using lithium hydroxide solution, the applicant proposes a method that, in the process of preparing lithium carbonate by carbonizing lithium hydroxide solution with carbon dioxide, adds an appropriate amount of additive to the lithium hydroxide solution and then introduces carbon dioxide into the solution at a suitable gas flow rate to promote bubble generation and enhance the gas-liquid mass transfer process. This not only shortens the carbonation time but also improves the utilization rate of carbon dioxide.

[0009] Specifically, the present invention provides a method for enhancing short-range carbonization preparation of battery-grade lithium carbonate, comprising:

[0010] (1) Prepare a lithium hydroxide solution, add a surfactant, and filter through a micropore to obtain a refined lithium hydroxide solution;

[0011] (2) Industrial-grade carbon dioxide is introduced into the refined lithium hydroxide solution at a gas flow rate of 0.03-0.3 L / min per gram of lithium to carry out the carbonization reaction. After carbonization, solid-liquid separation and washing are performed to obtain carbonized liquid and wet residue. The wet residue is dried and crushed to obtain battery-grade lithium carbonate.

[0012] In this technical solution, the reaction formula for preparing lithium carbonate from carbon dioxide-lithium hydroxide solution is as follows:

[0013] CO2 + OH - = HCO3 - (1)

[0014] HCO3 - + OH - = CO3 2- + H2O (2)

[0015] 2Li + + CO3 2- = Li2CO3(3)

[0016] Carbon dioxide is first adsorbed into the solution to generate bicarbonate ions, i.e., formula (1). When hydroxide ions are present in the solution, bicarbonate ions will generate carbonate ions, i.e., formula (2), and form precipitated lithium carbonate, i.e., formula (3). Compared with the gas-liquid two-phase mass transfer between carbon dioxide and water, the three reactions in formulas (1), (2), and (3) are all fast. The gas-liquid mass transfer between carbon dioxide and water is the rate-controlling step of the carbonation reaction. Increasing the flow rate of carbon dioxide is beneficial to improving the reaction rate. However, when the carbon dioxide flow rate increases to a certain level, the gas overflows into the solution before it can be mass transferred, which leads to a significant reduction in the utilization rate of carbon dioxide. This invention utilizes an alkali-resistant, water-soluble surfactant added to a lithium hydroxide solution. When high-flow-rate carbon dioxide is bubbled into the lithium hydroxide solution, a large number of bubbles are generated, significantly improving gas-liquid mass transfer efficiency, thereby increasing the overall reaction rate and shortening the time to reach the carbonization endpoint, thus achieving enhanced carbonization. Specifically, the addition of the surfactant, under a certain gas flow rate, provides significant bubble formation, thereby enhancing gas-liquid mass transfer and increasing the upper limit of the carbon dioxide inlet rate to accelerate the reaction. Therefore, under controlled high gas flow rates, the addition of the surfactant improves gas utilization. Furthermore, the large number of bubbles generated during carbonization reduces the initial particle size of the product, significantly lowering the cost of subsequent crushing.

[0017] Preferably, in step (2), the industrial-grade carbon dioxide is controlled at a flow rate of 0.05 to 0.2 L / min per gram of lithium.

[0018] Preferably, in step (1), the surfactant is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium lauryl ether sulfate; the amount of surfactant added is determined according to 0.01 to 0.1 g per gram of lithium in the solution.

[0019] Preferably, the lithium content in the lithium hydroxide solution is 25–35 g / L. When the lithium hydroxide concentration is too low, the addition of surfactant may reduce gas utilization. When carbonizing with a low-concentration lithium hydroxide solution, the rate-controlling step is the chemical reaction of hydroxide ions to carbonate ions. At this time, the addition of surfactant may actually exacerbate the escaping of carbon dioxide.

[0020] Preferably, in step (2), the carbonization temperature is 20–80°C, the endpoint pH value of the carbonization is 9.5–10.5, and the Li content in the carbonized solution is 2–6 g / L. The endpoint of carbonization is controlled by the pH value.

[0021] To utilize the lithium in the carbonized liquid, lithium carbonate is first prepared by precipitating lithium with sodium carbonate. Since the solubility of lithium phosphate is much lower than that of lithium carbonate, lithium phosphate can be prepared by precipitating lithium with sodium phosphate to further reduce the lithium content in the carbonized liquid. In addition, since the reagents used need to be in excess and the phosphorus-containing wastewater is highly hazardous, calcium salt precipitation is required to prepare calcium phosphate precipitate for the phosphorus-containing wastewater. The remaining precipitated liquid contains only soluble impurities such as sodium and potassium, which can be recycled as mother liquor. After the concentration increases, salt precipitation treatment can be performed. Preferably, step (3) is also included, which includes: adding sodium carbonate to the carbonized liquid, performing solid-liquid separation after sufficient reaction to obtain lithium carbonate, adding sodium phosphate to the liquid obtained from solid-liquid separation, performing secondary centrifugation and filtration after sufficient reaction to obtain lithium phosphate, and adding calcium salt to the secondary centrifugation filtrate to obtain calcium slag and precipitated liquid.

[0022] Preferably, the amount of sodium carbonate added is 1.05 to 1.1 times the theoretical amount of lithium precipitation.

[0023] Preferably, the amount of sodium phosphate added is 1.05 to 1.1 times the theoretical amount of lithium precipitation; the calcium salt is calcium oxide and / or calcium hydroxide, the amount of calcium salt is 1.05 to 1.1 times the theoretical amount of phosphorus precipitation, the calcium slag is used as building filler, and the phosphorus precipitation liquid can be recycled as mother liquor.

[0024] Preferably, in step (2), in order to avoid the reaction of a large amount of carbon dioxide and lithium carbonate to generate lithium bicarbonate, the carbon dioxide that escapes during the carbonization process is collected in a storage tank through a pipeline, compressed and purified, and then recycled.

[0025] In step (2), the solid-liquid separation is preferably centrifugal separation, but other conventional solid-liquid separation methods, such as filtration, can also be used.

[0026] Preferably, the lithium hydroxide solution is prepared using lithium hydroxide and water; the lithium hydroxide is one or more of battery-grade lithium hydroxide monohydrate, battery-grade anhydrous lithium hydroxide, industrial-grade lithium hydroxide monohydrate, and industrial-grade anhydrous lithium hydroxide, and the water is clean water or industrial pure water.

[0027] Preferably, in step (3), the solid-liquid separation is centrifugal filtration.

[0028] Preferably, in step (1), the pore size of the microporous filter is no greater than 0.5 μm.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention adds an alkali-resistant, water-soluble surfactant to the solution and then introduces a certain flow rate of carbon dioxide into the lithium hydroxide solution. During the carbonization process of the lithium hydroxide solution using carbon dioxide, a large number of bubbles are generated, which significantly improves the gas-liquid mass transfer of carbon dioxide, significantly shortens the time to reach the carbonization endpoint, and improves the utilization rate of carbon dioxide and production efficiency.

[0031] 2. The surfactant used in this invention is low in cost and has good water solubility. The prepared lithium carbonate product meets the requirements of battery grade. Furthermore, the initial particle size of the product is reduced by the generation of a large number of bubbles during the carbonization process, which significantly reduces the cost of subsequent crushing.

[0032] 3. The technical solution provided by this invention has the advantages of short process, simple operation, low cost and green environmental protection, which helps to cope with the situation that the market demand for battery-grade lithium carbonate is greater than that for battery-grade lithium hydroxide, and has considerable industrial application prospects. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a process flow diagram used in Embodiment 1 of the present invention.

[0035] Figure 2 This is a process flow diagram of the post-carbonization liquid treatment used in Embodiment 2 of the present invention. Detailed Implementation

[0036] To facilitate understanding of the present invention, the invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0038] Example 1:

[0039] Use such as Figure 1The process flow shown involves preparing 4 L of lithium hydroxide solution with a lithium content of 25 g / L using industrial-grade LiOH·H₂O (LiOH content 56.6%) and industrial pure water. 2 L of this solution, labeled Group A, is supplemented with 0.5 g of sodium dodecyl sulfate additive, while the remaining 2 L is treated without additives (Group B). Both Group A and Group B solutions are filtered through a 0.5 μm micropore filter and then subjected to carbon dioxide at a constant temperature of 20°C and a gas flow rate of 5 L / min. Group A produces significantly more bubbles than Group B. Group A solution reaches pH 9.5 after 16 minutes of reaction, producing a large amount of white precipitate, at which point carbonation ends. Group B solution reaches pH 9.5 after 27 minutes of reaction, also producing a large amount of white precipitate, at which point carbonation ends. The two suspensions are centrifuged, filtered, washed, and dried to obtain two groups of lithium carbonate. The particle size D of the lithium carbonate in Group A is determined. 50 The particle size of lithium carbonate in group B is 32 μm. 50 The particle size was 67 μm. Results showed that the addition of sodium dodecyl sulfate significantly shortened the time to reach the carbonization endpoint. Analysis revealed that the presence of the surfactant increased the upper limit of the gas velocity in the traditional carbonization reactor (i.e., the usable carbon dioxide gas flow rate), or in other words, increased the gas velocity in the traditional carbonization reactor became the upper limit of the rate control step. The addition of the surfactant increased the effective upper limit of the gas flow rate, thereby improving the carbonization efficiency. Furthermore, it significantly reduced the initial particle size of the dried lithium carbonate, significantly reducing the pressure on subsequent crushing processes. The lithium ion concentration in the carbonized liquid was 1.76 g / L.

[0040] After airflow crushing, the lithium carbonate product obtained from Group A had a particle size D50 of 4 μm and a purity of 99.80%. Other indicators are shown in Table 1. The results show that all indicators of Group A lithium carbonate meet the national standard for battery-grade lithium carbonate.

[0041] Table 1. Chemical composition of battery-grade lithium carbonate obtained from Group A in Example 1 (unless otherwise specified, all units are wt%)

[0042]

[0043] Example 2:

[0044] Use such as Figure 2The process flow shown describes the treatment of the carbonized liquid from Group A in Example 1. First, sodium carbonate (1.05 times the theoretical amount for lithium precipitation) is added to the carbonized liquid. After filtration, solid lithium carbonate and filtrate are obtained. Sodium phosphate (1.05 times the theoretical amount for lithium precipitation) is then added to the filtrate to obtain lithium carbonate and lithium phosphate. The purity of these two materials is tested to be 98.6% and 98.2%, respectively, meeting the standards for industrial-grade lithium carbonate and lithium phosphate. These materials can be sold externally or used for causticization to prepare lithium hydroxide. Calcium hydroxide (1.05 times the theoretical amount for phosphorus precipitation) is then added to the lithium-precipitated liquid to obtain calcium slag composed of calcium phosphate and calcium carbonate. This slag can be used as building filler. The phosphorus-precipitated liquid is tested to be free of phosphorus and can be recycled as mother liquor.

[0045] Example 3:

[0046] Use such as Figure 1 The process flow shown involves preparing 4 L of lithium hydroxide solution with a lithium content of 35 g / L using industrial-grade LiOH·H₂O (LiOH content 56.6%) and industrial pure water. 2 L of this solution, labeled Group C, is supplemented with 7 g of sodium dodecylbenzenesulfonate additive, while the remaining 2 L is treated without additives and designated Group D. Both Groups C and D are filtered through a 0.5 μm micropore filter and then subjected to carbon dioxide at a constant temperature of 80℃ and a gas flow rate of 5 L / min. Group C produces significantly more bubbles than Group D. Group C solution reaches pH 10.5 after 21 min of reaction, producing a large amount of white precipitate, at which point carbonation ends. Group D solution reaches pH 10.5 after 32 min of reaction, also producing a large amount of white precipitate, at which point carbonation ends. Both suspensions are centrifuged, filtered, washed, and dried to obtain two groups of lithium carbonate. The particle size of the lithium carbonate in Group C is determined by testing the particle size of Group D. 50 The particle size of lithium carbonate in group D is 34 μm. 50 The particle size was 66 μm. The results showed that the addition of sodium dodecylbenzenesulfonate significantly shortened the time to reach the carbonization endpoint, significantly reduced the initial particle size of the dried lithium carbonate, and significantly reduced the pressure of the subsequent crushing process. The lithium ion concentration in the carbonization solution was 2.04 g / L.

[0047] After airflow crushing, the lithium carbonate product obtained from Group C has a particle size D50 of 4μm and a purity of 99.62%. All other indicators meet the national standard for battery-grade lithium carbonate.

[0048] Example 4:

[0049] Use such as Figure 1The process flow shown involves preparing 4 L of lithium hydroxide solution with a lithium content of 30 g / L using industrial-grade LiOH·H₂O (LiOH content 56.6%) and industrial pure water. 2 L of this solution, labeled group E, is treated with 1 g of sodium lauryl ether sulfate additive, while the remaining 2 L is treated without additives (group F). Both groups E and F are filtered through a 0.5 μm micropore and then subjected to carbon dioxide purging at a constant temperature of 50 °C at a flow rate of 5 L / min. Group E produces significantly more bubbles than group F. Group E requires 20 min to reach pH 10, producing a large amount of white precipitate, at which point carbonation ends. Group F requires 28 min to reach pH 10, also producing a large amount of white precipitate, at which point carbonation ends. The two suspensions are centrifuged, filtered, washed, and dried to obtain two groups of lithium carbonate. The particle size D of the lithium carbonate in group E is determined. 50 The particle size of lithium carbonate in group F is 35 μm. 50 The particle size was 62 μm. The results showed that the addition of sodium lauryl ether sulfate significantly shortened the time to reach the carbonization endpoint, significantly reduced the initial particle size of the dried lithium carbonate, and significantly reduced the pressure of the subsequent crushing process. The lithium ion concentration in the carbonization solution was 1.84 g / L.

[0050] After airflow crushing of lithium carbonate in Group E, the resulting lithium carbonate product has a particle size D50 of 5μm and a purity of 99.77%, with all other indicators meeting the national standard for battery-grade lithium carbonate.

[0051] Example 5:

[0052] Use such as Figure 1 The process flow shown involves preparing 2 L of lithium hydroxide solution with a lithium content of 30 g / L using industrial-grade LiOH·H₂O (LiOH content 56.6%) and industrial pure water. One L of this solution, labeled Group G, is supplemented with 0.5 g of sodium dodecyl sulfate additive, while the remaining 1 L is treated without additives and designated Group H. Both Group G and Group H solutions are filtered through a 0.5 μm micropore filter and then subjected to carbon dioxide permeation at a constant temperature of 50 °C and a flow rate of 6 L / min. Group G produces significantly more bubbles than Group H. Group G solution reaches pH 10 after 11 minutes of reaction, producing a large amount of white precipitate, at which point carbonation ceases. Group H solution reaches pH 10 after 15 minutes of reaction, also producing a large amount of white precipitate, at which point carbonation ceases. The two suspensions are centrifuged, filtered, washed, and dried to obtain two groups of lithium carbonate. The particle size D50 of lithium carbonate in Group G is 29 μm, and that in Group H is 52 μm. The results showed that the addition of sodium dodecyl sulfate significantly shortened the time to reach the carbonization endpoint, reduced the initial particle size of the dried lithium carbonate, and decreased the pressure on subsequent crushing processes. The lithium ion concentration in the carbonization solution was 1.87 g / L.

[0053] After airflow crushing of lithium carbonate in Group G, the resulting lithium carbonate product has a particle size D50 of 4μm and a purity of 99.67%, with all other indicators meeting the national standard for battery-grade lithium carbonate.

[0054] It is worth noting that when the gas flow rate reaches 0.2 L / min per gram of lithium, although the additive still has a 26.7% reduction effect on the time to reach the carbonization endpoint, the faster gas flow rate leads to a significant reduction in the time for carbon dioxide to contact the solution, resulting in a carbon dioxide utilization rate that is not as good as in Examples 1, 3, and 4.

[0055] Comparative Example 1:

[0056] Use such as Figure 1 The process flow shown involves preparing 4 L of lithium hydroxide solution with a lithium content of 30 g / L using industrial-grade LiOH·H₂O (LiOH content 56.6%) and industrial pure water. 2 L of this solution, labeled group g, is supplemented with 0.5 g of sodium dodecyl sulfate additive, while the remaining 2 L is treated without additives and designated group h. Both groups g and h are filtered through a 0.5 μm micropore and then subjected to carbon dioxide purging at a constant temperature of 50 °C at a flow rate of 1 L / min. Both groups produce relatively few bubbles. Group g requires 128 min to reach pH 10, producing a large amount of white precipitate, at which point carbonation is complete. Group h requires 130 min to reach pH 10, also producing a large amount of white precipitate, at which point carbonation is complete. The two suspensions are centrifuged, filtered, washed, and dried to obtain two groups of lithium carbonate. The particle size D of the lithium carbonate in group g is determined. 50 The particle size of lithium carbonate tested in group h is 32 μm. 50 The particle size was 74 μm. The results showed that when the carbon dioxide flow rate was reduced to 0.017 L / min per gram of lithium, the addition of sodium dodecyl sulfate additive could not significantly shorten the time to reach the carbonization endpoint, but it could reduce the initial particle size of the dried lithium carbonate.

[0057] Compared with Examples 1-4, the results show that foaming additives such as sodium dodecyl sulfate can generate a large number of bubbles under high gas flow rates, significantly shortening the carbonation time. However, at low gas flow rates, they cannot significantly increase the number of bubbles during the reaction, nor can they significantly shorten the carbonation time. Furthermore, because the surfactant adheres to the product surface, it hinders the aggregation of lithium carbonate; therefore, adding the surfactant has the effect of reducing particle size.

[0058] Comparative Example 2:

[0059] Use such as Figure 1The process flow shown involves preparing 4 L of lithium hydroxide solution with a lithium content of 20 g / L using industrial-grade LiOH·H₂O (LiOH content 56.6%) and industrial pure water. 2 L of this solution, labeled group i, is treated with 0.5 g of sodium dodecyl sulfate additive, while the remaining 2 L is treated without additives (group j). Both groups i and j are filtered through a 0.5 μm micropore and then subjected to carbon dioxide purging at a constant temperature of 50 °C at a flow rate of 3 L / min. Group i produces significantly more bubbles than group j, and there is noticeable carbon dioxide escaping and waste in the reaction of group i. Group i requires 32 min to reach pH 10, producing a large amount of white precipitate, at which point carbonation ends. Group j requires 28 min to reach pH 10, also producing a large amount of white precipitate, at which point carbonation ends. The two suspensions are centrifuged, filtered, washed, and dried to obtain two groups of lithium carbonate. The particle size D of the lithium carbonate in group i is determined. 50 The particle size D of lithium carbonate in group j is 26 μm. 50 It is 65μm.

[0060] The results show that when the lithium content in the solution is 20 g / L, the additive no longer shortens the carbonation time when a large flow rate of carbon dioxide is introduced. This is because under this lithium concentration condition, the gas-liquid mass transfer of carbon dioxide is no longer a rate-controlling step. When a large flow rate of carbon dioxide is introduced, the carbon dioxide cannot react with the lithium hydroxide in the solution to form lithium carbonate in time, resulting in a waste of carbon dioxide. Furthermore, the presence of the additive increases the amount of bubbles. The large number of bubbles generated here not only fails to shorten the reaction time but also leads to more carbon dioxide escaping, reducing the reaction efficiency. From the perspective of production efficiency, the lithium content should be as high as possible. In the embodiments of the present invention, a solution with a low lithium content will lead to the generation of a large number of bubbles during the reaction, resulting in a significant loss of carbon dioxide. Therefore, the lithium content of the lithium hydroxide solution described in the present invention is preferably 25–35 g / L.

[0061] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for enhancing short-range carbonization preparation of battery-grade lithium carbonate, characterized in that, include: (1) Prepare a lithium hydroxide solution, add a surfactant, and filter through a micropore to obtain a refined lithium hydroxide solution; The lithium content in the lithium hydroxide solution is 25-35 g / L; the amount of surfactant added is determined according to 0.01-0.1 g per gram of lithium in the solution; (2) Industrial-grade carbon dioxide is introduced into the refined lithium hydroxide solution at a gas flow rate of 0.03-0.3 L / min per gram of lithium to carry out the carbonization reaction. Then, after solid-liquid separation and washing, carbonized liquid and wet residue are obtained. The wet residue is dried and crushed to obtain battery-grade lithium carbonate.

2. The method for enhancing short-range carbonization to prepare battery-grade lithium carbonate as described in claim 1, characterized in that, The surfactant is one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium lauryl ether sulfate.

3. The method for enhancing short-range carbonization to prepare battery-grade lithium carbonate as described in claim 1, characterized in that, Industrial-grade carbon dioxide is controlled at a flow rate of 0.05–0.2 L / min per gram of lithium.

4. The method for enhancing short-range carbonization to prepare battery-grade lithium carbonate as described in claim 1, characterized in that, In step (2), the temperature of the carbonization reaction is 20-80℃; the final pH value of the carbonization reaction is 9.5-10.5; and the Li content in the carbonized liquid is 1.5-6 g / L.

5. The method for preparing battery-grade lithium carbonate by enhanced carbonization short-range preparation as described in any one of claims 1 to 4, characterized in that, It also includes step (3), which includes: adding sodium carbonate to the carbonized liquid, performing solid-liquid separation after sufficient reaction to obtain lithium carbonate, adding sodium phosphate to the liquid obtained from solid-liquid separation, performing solid-liquid separation after sufficient reaction to obtain lithium phosphate, adding calcium salt to the solution obtained from solid-liquid separation, and reacting to obtain calcium slag and precipitated phosphorus liquid.

6. The method for enhancing short-range carbonization to prepare battery-grade lithium carbonate as described in claim 5, characterized in that, The amount of sodium carbonate added is 1.05 to 1.1 times the theoretical amount used for lithium precipitation; The amount of sodium phosphate added is 1.05 to 1.1 times the theoretical amount of lithium precipitation; the calcium salt is calcium oxide and / or calcium hydroxide, and the amount of calcium salt used is 1.05 to 1.1 times the theoretical amount of phosphorus precipitation.

7. The method for enhancing short-range carbonization to prepare battery-grade lithium carbonate as described in claim 5, characterized in that, The calcium slag is used as a building filler, and the precipitated phosphorus solution can be recycled as a mother liquor.

8. The method for enhancing short-range carbonization to prepare battery-grade lithium carbonate as described in claim 5, characterized in that, In step (3), the solid-liquid separation is centrifugal filtration.

9. The method for preparing battery-grade lithium carbonate by enhanced carbonization short-range as described in any one of claims 1 to 4, characterized in that, The lithium hydroxide solution is prepared using lithium hydroxide and water; the lithium hydroxide is one or more of battery-grade lithium hydroxide monohydrate, battery-grade anhydrous lithium hydroxide, industrial-grade lithium hydroxide monohydrate, and industrial-grade anhydrous lithium hydroxide, and the water is clean water or industrial pure water.

10. The method for preparing battery-grade lithium carbonate by enhanced carbonization short-range as described in any one of claims 1 to 4, characterized in that, In step (2), the carbon dioxide released during the carbonization process is collected in a storage tank through a pipeline, compressed and purified, and then recycled. In step (2), the solid-liquid separation is centrifugal filtration.

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