Method for efficiently preparing battery-grade lithium carbonate

Abstract

The invention belongs to the technical field of lithium resource extraction, refining and lithium salt preparation, and particularly relates to a method for efficiently preparing battery-grade lithium carbonate. According to the method provided by the invention, the solid-gas reaction is adopted to replace the traditional gas-liquid reaction, the lithium hydroxide solution is vaporized to form small-particle-size lithium hydroxide, the small-particle-size lithium hydroxide is completely converted into lithium carbonate in the reaction process with the gas carbonizer, and the prepared lithium carbonate is relatively small in particle size, so that the subsequent preparation of the positive electrode material is facilitated; and the reaction and the drying are basically carried out at the same time, so that the product loss of the lithium carbonate in the reaction due to the processes of additional drying and the like is reduced, and the yield of the prepared lithium carbonate is improved from less than 80% in the traditional method to more than or equal to 99%. In addition, the preparation efficiency is greatly improved, and in the same batch preparation, the traditional reaction time is shortened from 1-2 hours to 5-10 minutes.

Description

Technical Field

[0001] This invention relates to the technical field of lithium resource extraction, refining, and lithium salt preparation, specifically a method for efficiently preparing battery-grade lithium carbonate. Background Technology

[0003] Currently, the mainstream power lithium batteries on the market are ternary lithium batteries and lithium iron phosphate batteries. Li₂CO₃ is one of the important raw materials for their synthesis. Among them, the sulfate and sodium content in lithium carbonate are the core impurity indicators. Excessive levels will affect the electrochemical performance of ternary lithium batteries or lithium iron phosphate batteries. In the industry, lithium carbonate is usually synthesized by adding sodium carbonate to lithium sulfate solution. Because lithium carbonate is easily soluble in solution, the lithium precipitation efficiency is generally low (<80%). At the same time, the synthesized lithium carbonate is easily contaminated with sodium and sulfate. If purification is required, further carbonization and pyrolysis are necessary, which will further cause lithium carbonate loss and significantly reduce profits. Based on this, researchers have proposed a series of improvement methods to address the problems of low primary lithium precipitation rate, reduced profits, and easy contamination with sodium and sulfate, which affects the electrochemical performance of downstream products.

[0004] For example, Chinese patent application CN 107298450 A 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 treat the lithium salt to obtain a lithium hydroxide solution, followed by evaporation and concentration processes to obtain a battery-grade lithium hydroxide solution. Finally, carbon dioxide gas is introduced to react and produce high-purity lithium carbonate. Another example is patent application CN 109650414 A, which discloses a method for preparing battery-grade and high-purity lithium hydroxide and lithium carbonate from a high-impurity lithium source. This method purifies the lithium salt using a composite electrodialysis method to obtain a lithium hydroxide solution, followed by concentration and other processes to obtain a high-purity wet lithium hydroxide solution. The wet solution is then dissolved in water and reacted with carbon dioxide to obtain lithium carbonate. While the lithium carbonate prepared by these methods has high purity, the methods are complex, energy-intensive, and involve liquid-gas reactions, which can lead to lithium source loss, reduced lithium carbonate product yield, or increased production costs, thus reducing profits. Summary of the Invention

[0005] This application provides a method for efficiently preparing battery-grade lithium carbonate, thereby solving the problems of low purity and yield in the preparation of lithium carbonate in related technologies.

[0006] In a first aspect, a method for efficiently preparing battery-grade lithium carbonate is provided, comprising: Step 1: Purify the lithium sulfate solution to obtain a lithium hydroxide solution; Step 2: Add dispersant to the lithium hydroxide solution and mix thoroughly; Step 3: Simultaneously introduce the carbonizing agent and lithium hydroxide solution into the reactor for vaporization, react under heating conditions, and collect the resulting product to obtain lithium carbonate.

[0007] In any embodiment, the purification method is as follows: Lithium sulfate solution is electrolyzed into lithium hydroxide solution and sulfuric acid solution using bipolar membrane electrodialysis technology; In any embodiment, the dispersant is one of sodium dodecylbenzenesulfonate, sodium lignosulfonate, polyvinylpyrrolidone, sodium polyacrylate, etc., and the amount added is 0.5%-2.0% of the mass of the lithium hydroxide solution.

[0008] In any embodiment, the carbonizing agent is selected from at least one of carbon dioxide and carbonic acid; In any embodiment, the reactor includes, but is not limited to, a spray dryer; the function of the reactor is to rapidly vaporize lithium hydroxide into solid particles when the lithium hydroxide solution is introduced. In any embodiment, the lithium hydroxide solution is atomized into micron-sized (≤20μm) droplets using a high-pressure nozzle, and the carbonizing agent is introduced in the reverse or radial direction; the purpose is to ensure that the lithium hydroxide solution and the carbonizing agent are in full contact under the action of centrifugal force inside the reactor, thereby improving the reaction efficiency.

[0009] When lithium hydroxide solution is introduced into the reactor, it rapidly transforms into solid particles at high temperature. At the same time, the water in the solution quickly vaporizes into water vapor. At this time, in the solid-gas reaction system of lithium hydroxide and carbonizing agent, a small amount of water vapor exists, which can act as a reaction medium to promote the adsorption of gas and solid surfaces, accelerate the reaction rate, and increase the yield. However, the introduction of excessive water vapor will cause the lithium hydroxide surface to deliquesce, resulting in the agglomeration of solid particles and reducing the effective reaction surface area.

[0010] In any embodiment, the reaction temperature is 80°C to 100°C, and the reaction pressure is 6.4 kPa to 101.325 kPa; Preferably, the reaction temperature is 80°C and the reaction pressure is 6.4 kPa.

[0011] In any embodiment, the reaction time is 5 to 10 minutes.

[0012] In any embodiment, the molar ratio of lithium hydroxide to carbonizing agent in the introduced lithium hydroxide solution is ≤2.

[0013] Secondly, a battery-grade lithium carbonate is provided, which is prepared by the method described above.

[0014] The beneficial effects of the technical solution provided in this application include: 1. The method provided in this application uses a solid-gas reaction instead of a traditional gas-liquid reaction. After the lithium hydroxide solution is vaporized, it forms small-particle lithium hydroxide, which is completely converted into lithium carbonate during the reaction with the gaseous carbonizing agent. With the dispersant and high-pressure atomization, micron-sized lithium hydroxide particles can be prepared. The generated lithium carbonate has a smaller particle size, which is more conducive to improving the performance of the cathode material prepared using it. 2. The method provided in this application avoids the loss caused by the high solubility of lithium carbonate in traditional liquid-phase reactions through solid-gas reactions. The reaction and drying are carried out almost simultaneously, reducing product loss of lithium carbonate during the reaction due to additional drying processes, and improving the yield of prepared lithium carbonate from <80% in traditional methods to ≥99%. Furthermore, it greatly improves the preparation efficiency, shortening the reaction time from 1~2h in the traditional method to 5~10min in the same batch preparation. 3. Because the reagents used in this method are environmentally friendly and do not produce wastewater or pollutants, the reaction tail gas can be continuously recycled into the reactor after being dehydrated and dried, which improves the utilization rate of the carbonizing agent, avoids greenhouse gas emissions, and saves raw material costs. Compared with traditional processes, it can reduce carbon emissions by more than 50%, and has the advantage of being environmentally friendly in the preparation process. In addition, the method of this invention also has the significant advantage of being simple in preparation, making it suitable for industrial application. Detailed Implementation

[0015] The technical solution of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0016] Example 1 Step 1: First, lithium sulfate solution is electrolyzed into lithium hydroxide solution and sulfuric acid solution using bipolar membrane electrodialysis technology. Influent parameters: TDS maintained at 110-120 g / L; effluent parameters: H₂O of acid solution... + ≥2mol / L, alkali solution OH - ≥2mol / L, the bipolar membrane material is LANCYTOM bipolar membrane + lithium solution special anion / cation membrane; Step 2: Mix lithium hydroxide solution and carbonic acid (or CO2) in a molar ratio of 2:1, pass the mixture into a spray dryer, and spray dry at 100°C under 1 standard atmosphere for 10 minutes. Collect the sample and test the purity of the product.

[0017] The Li content setting in the lithium hydroxide solution and the purity test of the resulting product are shown in Table 1.

[0018] Increasing the lithium content helps improve product purity, mainly because a higher concentration of Li in the influent leads to a higher concentration of LiOH obtained from electrolysis, thus improving product purity.

[0019] Higher lithium hydroxide concentrations result in smaller lithium carbonate particle sizes because higher concentrations produce more lithium carbonate per unit time. Within the high-temperature chamber, these particles undergo collisions, leading to a gradual decrease in particle size. Battery-grade lithium carbonate standards require a D50 of <15μm. This embodiment, by adjusting the lithium hydroxide solution concentration, not only effectively improves product yield and quality but also controls product particle size, reducing subsequent air jet milling processes and thus lowering energy consumption.

[0020] Example 2 Step 1: First, lithium sulfate solution is electrolyzed into lithium hydroxide solution and sulfuric acid solution using bipolar membrane electrodialysis technology. Influent parameters: TDS maintained at 110-120 g / L, Li content in lithium hydroxide solution 8 g / L. Effluent parameters: Acid solution H... + ≥2mol / L, alkali solution OH - ≥2mol / L, the bipolar membrane material is LANCYTOM bipolar membrane + lithium solution special anion / cation membrane; Step 2: Mix lithium hydroxide solution and carbonic acid (or CO2) in a molar ratio of 2:1, pass the mixture into a spray dryer, and spray dry at a certain temperature under a standard atmosphere for 10 minutes. Collect the sample and test the purity of the product.

[0021] The temperature settings and test results in this embodiment are shown in Table 2.

[0022] Table 2

[0023] As temperature increases, product purity improves to some extent, mainly due to the more thorough evaporation of moisture at higher temperatures, leading to a higher product yield. This increase in yield, in turn, results in improved product purity. However, beyond a certain temperature range, the yield and purity of lithium carbonate become limited. Furthermore, higher temperatures also lead to energy waste and increased production costs.

[0024] In addition, as the temperature increases, lithium carbonate crystals grow faster per unit time, resulting in smaller particle sizes of the prepared lithium carbonate.

[0025] Example 3 Step 1: First, lithium sulfate solution is electrolyzed into lithium hydroxide solution and sulfuric acid solution using bipolar membrane electrodialysis technology. Influent parameters: TDS maintained at 110-120 g / L, Li content in lithium hydroxide solution 8 g / L. Effluent parameters: Acid solution H... + ≥2mol / L, alkali solution OH - ≥2mol / L, the bipolar membrane material is LANCYTOM bipolar membrane + lithium solution special anion / cation membrane; Step 2: Mix lithium hydroxide solution and carbonic acid (or CO2) in a molar ratio of 2:1, pass the mixture into a spray dryer, spray dry at 100°C for 30 minutes, collect the sample, and test the purity of the product.

[0026] The pressure settings and test results for this embodiment are shown in Table 3. Table 3

[0027] This indicates that as the negative pressure increases, the boiling point of water gradually decreases. At 100℃ and 6.4Kpa, the lithium hydroxide solution dries more easily and quickly, resulting in smaller lithium hydroxide particles with a larger specific surface area and more active sites for reaction with carbon dioxide. This not only significantly reduces the preparation cycle but also results in smaller particle size of the lithium carbonate product.

[0028] In addition, at the same temperature, as the pressure inside the system gradually decreases, the system becomes negatively pressured, allowing more product to enter per unit time, and the moisture in the product evaporates more easily, thus gradually increasing the product yield.

[0029] Example 4 Step 1: First, lithium sulfate solution is electrolyzed into lithium hydroxide solution and sulfuric acid solution using bipolar membrane electrodialysis technology. Influent parameters: TDS maintained at 110-120 g / L, Li content in lithium hydroxide solution 8 g / L. Effluent parameters: Acid solution H... + ≥2mol / L, alkali solution OH - ≥2mol / L, the bipolar membrane material is LANCYTOM bipolar membrane + lithium solution special anion / cation membrane; Step 2: Add a certain amount of dispersant (taking sodium dodecylbenzenesulfonate as an example) to the lithium hydroxide solution, mix the lithium hydroxide solution and carbonic acid (or CO2) in a molar ratio of 2:1, pass the mixture into a spray dryer, and spray dry at 100°C under a pressure of 6.4 kPa. Collect the sample and test the purity and particle size of the product.

[0030] The dispersant dosage setting and test results for this embodiment are shown in Table 4. Table 4

[0031] As the amount of dispersant increases, the product yield gradually improves. This is mainly attributed to the dispersant enhancing the dispersion stability of the lithium hydroxide solution, further reducing the droplet size of lithium hydroxide, refining the dried lithium hydroxide particles, increasing the contact area and reaction sites with carbon dioxide, resulting in a more complete reaction and a gradually increasing yield. At the same time, the generated lithium carbonate particles are smaller, meeting the requirements of the battery-grade lithium carbonate industry.

[0032] As a raw material for lithium iron phosphate products, small-particle-size lithium carbonate is more conducive to the mixing of raw materials, thereby preparing lithium iron phosphate with uniform morphology and improving its electrochemical performance.

[0033] Example 5 Step 1: First, lithium sulfate solution is electrolyzed into lithium hydroxide solution and sulfuric acid solution using bipolar membrane electrodialysis technology. Influent parameters: TDS maintained at 110-120 g / L, Li content in lithium hydroxide solution 8 g / L. Effluent parameters: Acid solution H... + ≥2mol / L, alkali solution OH - ≥2mol / L, the bipolar membrane material is LANCYTOM bipolar membrane + lithium solution special anion / cation membrane; Step 2: Add 1.0% sodium dodecylbenzenesulfonate to the lithium hydroxide solution, mix the lithium hydroxide solution and carbonic acid (or CO2) in a molar ratio of 2:1, pass the mixture into a spray dryer, and spray dry at 80°C under a pressure of 6.4 kPa. Collect the sample and test the purity and particle size of the product.

[0034] The lithium carbonate prepared in this embodiment has a purity of 99.9%, a particle size (D50, μm) of 6.0, and a yield of 99.1%, as tested.

[0035] Compared to traditional lithium carbonate preparation methods, the lithium carbonate prepared in this embodiment has higher purity, smaller particle size, and higher yield, exhibiting significant advantages. However, due to the lower temperature compared to Example 4, the yield is slightly lower, and the particle size is slightly larger. Based on lithium carbonate industry standards, the purity of the product obtained at this point is already extremely high, and the yield and particle size show no significant difference compared to the conditions at 100℃. In summary, under suitable temperature and negative pressure conditions, not only can the purity of the product be further improved and the particle size optimized, but the system temperature can also be lowered, further reducing the energy consumption of the preparation process and saving preparation costs.

[0036] Comparative Example 1 Step 1: First, lithium sulfate solution is electrolyzed into lithium hydroxide solution and sulfuric acid solution using bipolar membrane electrodialysis technology. Influent parameters: TDS maintained at 110-120 g / L, Li content in lithium hydroxide solution 9 g / L. Effluent parameters: Acid solution H... + ≥2mol / L, alkali solution OH- ≥2mol / L, the bipolar membrane material is LANCYTOM bipolar membrane + lithium solution special anion / cation membrane; Step 2: Pass CO2 into a lithium hydroxide solution (where the molar ratio of lithium hydroxide to carbon dioxide is 2.1), react at 1 standard atmosphere and 100°C, collect the sample, dry it in a 100°C forced-air drying oven, and then test the purity and yield of the product.

[0037] After the reaction was completed, the mass of lithium carbonate obtained after filtration (yield < 75%) was much smaller than the mass of the product obtained under the same reaction conditions in Example 1 (yield > 90%). This is attributed to the solubility of lithium carbonate, some of which dissolved in the lithium hydroxide solution and could not be recovered. At the same time, some CO2 was lost due to overflow under high temperature conditions. Therefore, the overall yield was < 75%.

[0038] Comparative Example 2 Step 1: Take analytical grade solid lithium hydroxide, pass CO2 into the solid lithium hydroxide (where the molar ratio of lithium hydroxide to carbon dioxide is 2.1), react at 100°C for 10 min under 1 standard atmosphere, collect the sample, dry it in a 100°C forced-air drying oven, and then test the purity and yield of the product.

[0039] At the end of the reaction, the product is still solid lithium hydroxide. Because the solid lithium hydroxide particles are relatively large and the activation energy is low, it cannot react with carbon dioxide under the above conditions. In the example, the lithium hydroxide solution is directly spray-dried to contact carbon dioxide. The resulting lithium hydroxide particles are as small as nanometers, have a large specific surface area, and a high activation energy, thus they can be converted into lithium carbonate.

[0040] Furthermore, the method of the present invention can prepare 1 ton of lithium carbonate in 1 hour, while the existing method can prepare the same amount of lithium carbonate in 8 hours. It can be seen that the method of the present invention has a higher preparation efficiency than the existing technology.

[0041] The cost of preparing 1 ton of lithium carbonate using the method of this invention is approximately 1,870 yuan, while the cost of preparing the same lithium carbonate using existing methods is 5,000 yuan. It is evident that the method of this invention has a higher preparation cost and significantly higher profit compared to existing technologies.

[0042] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for efficiently preparing battery-grade lithium carbonate, characterized in that, include: Step 1: Purify the lithium sulfate solution to obtain a lithium hydroxide solution; Step 2: Add dispersant to the lithium hydroxide solution and mix thoroughly; Step 3: Simultaneously introduce the carbonizing agent and lithium hydroxide solution into the reactor for vaporization, react under heating conditions, and collect the resulting product to obtain lithium carbonate.

2. The method for efficiently preparing battery-grade lithium carbonate according to claim 1, characterized in that, The lithium hydroxide solution contains Li ≤ 10 g / L.

3. The method for efficiently preparing battery-grade lithium carbonate according to claim 1, characterized in that, The purification described in step 1 involves electrolyzing a lithium sulfate solution into a lithium hydroxide solution and a sulfuric acid solution using bipolar membrane electrodialysis technology.

4. The method for efficiently preparing battery-grade lithium carbonate according to claim 1, characterized in that, The dispersant mentioned in step 2 is one of sodium dodecylbenzenesulfonate, sodium lignosulfonate, polyvinylpyrrolidone, sodium polyacrylate, etc., and the amount added is 0.5%-2.0% of the mass of lithium hydroxide solution.

5. The method for efficiently preparing battery-grade lithium carbonate according to claim 1, characterized in that, In step 2, the lithium hydroxide solution is atomized into micron-sized (≤20μm) droplets using a high-pressure nozzle, and the carbonizing agent is introduced in the reverse or radial direction; the reaction temperature is 80~100℃, and the reaction pressure is 6.4~101.325Kpa.

6. The method for efficiently preparing battery-grade lithium carbonate according to claim 1, characterized in that, The reaction temperature in step 3 is 80°C, and the reaction pressure is 6.4 kPa.

7. The method for efficiently preparing battery-grade lithium carbonate according to claim 1, characterized in that, The carbonizing agent mentioned in step 3 is selected from at least one of carbon dioxide and carbonic acid.

8. The method for efficiently preparing battery-grade lithium carbonate according to claim 1, characterized in that, The reactor mentioned in step 3 includes, but is not limited to, a spray dryer.

9. The method for efficiently preparing battery-grade lithium carbonate according to claim 1, characterized in that, In step 3, the molar ratio of lithium hydroxide to the carbonizing agent in the lithium hydroxide solution is ≤2, and the reaction time is 5~10 min.

10. A battery-grade lithium carbonate, characterized in that, It is prepared by the method described in any one of claims 1 to 9.

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