Method for preparing battery-grade manganese sulfate from ternary lithium battery positive electrode material powder

Abstract

The invention discloses a method for preparing battery-grade manganese sulfate from ternary lithium battery positive electrode material powder, which comprises the following steps: S1, mixing the ternary lithium battery positive electrode material powder with a sulfuric acid solution and a reducing agent for leaching reaction, adding a lattice dopant into a reaction system, and performing solid-liquid separation after the reaction is completed, leach liquor and residues containing aluminum and copper are obtained; s2, a precipitant is added into the leachate obtained in the step S1 for a reaction, solid-liquid separation is conducted after the reaction is completed, and a high-purity manganese-containing solution and manganese-based compound sediment rich in impurities are obtained; and S3, the high-purity manganese-containing solution obtained in the step S2 is subjected to concentration, evaporative crystallization, centrifugal separation and drying, and a battery-grade manganese sulfate product is obtained. The method provided by the invention overturns the traditional multi-step chemical precipitation impurity removal process, realizes high-selectivity and short-distance separation of manganese, and has the outstanding advantages of extremely short flow, high yield, good product purity and low cost.

Description

Technical Field

[0001] This invention belongs to the field of waste lithium-ion battery resource utilization technology, specifically involving a method for preparing battery-grade manganese sulfate from recycled ternary lithium-ion battery cathode material (ternary lithium battery cathode material powder). Background Technology

[0002] With the explosive growth of the new energy vehicle industry, a large number of lithium-ion batteries are entering their end-of-life period. Ternary lithium battery cathode material powder (Li(Ni) x Co y Mn z O2 contains valuable metals such as nickel, cobalt, manganese, and lithium, and its efficient recycling is of great significance for resource recycling and environmental protection.

[0003] Currently, the conventional process for recovering manganese sulfate from ternary lithium battery cathode material powder typically includes: sulfuric acid + reducing agent leaching, neutralization to remove aluminum, sulfidation to remove copper, fluorination to remove calcium and magnesium, solvent extraction or deep precipitation to separate nickel and cobalt, and finally, crystallization of the manganese solution. These methods suffer from long processes, high reagent consumption, low manganese yield (due to losses from multiple precipitation processes), and difficulty in completely separating cobalt and nickel ions with similar properties to manganese, resulting in the final product purity failing to consistently meet battery-grade requirements.

[0004] Therefore, developing a new method for the short-process preparation of battery-grade manganese sulfate with short flow, high selectivity, and high yield has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a short-process and efficient method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder includes the following steps: S1. The ternary lithium battery cathode material powder is mixed with sulfuric acid solution and reducing agent to carry out leaching reaction. At the same time, a lattice dopant is added to the reaction system. After the reaction is completed, solid-liquid separation is carried out to obtain leaching solution and residue containing aluminum and copper. During the leaching reaction, the redox potential of the reaction system is controlled at 200-400 mV, and the pH value at the reaction endpoint is controlled at 1.5-3.0. The lattice dopant is a phosphate, and its addition amount is 1.0-1.5 times the theoretical amount, which is the amount required to completely precipitate 10-30% of the manganese ions in the leachate; S2. Add a precipitant to the leachate obtained in step S1 and react. After the reaction is complete, perform solid-liquid separation to obtain a high-purity manganese-containing solution and a manganese-based compound precipitate rich in impurities. The precipitant is a soluble phosphate, and the amount added is 1.05-1.2 times the theoretical amount required to completely precipitate the remaining manganese ions in the solution. S3. The high-purity manganese-containing solution obtained in step S2 is concentrated, evaporated and crystallized, centrifuged and dried to obtain battery-grade manganese sulfate product.

[0007] As a further improvement, step S4 is also included: the manganese-based compound precipitate rich in impurities obtained in step S2 is leached with dilute sulfuric acid solution by stirring to obtain a manganese-containing desorption solution and a secondary precipitate enriched with cobalt, nickel and lithium, and the manganese-containing desorption solution is returned to the leaching process of step S1 for recycling.

[0008] As a further improvement, the leaching reaction temperature in step S1 is 50-90°C.

[0009] As a further improvement, the concentration of the sulfuric acid solution in step S1 is 0.5-2 mol / L.

[0010] As a further improvement, the reducing agent in step S1 is one of hydrogen peroxide, sodium sulfite, or sodium thiosulfate.

[0011] As a further improvement, step S2 is carried out at 60-80°C under stirring conditions.

[0012] As a further improvement, the total content of cobalt, nickel, and lithium impurities in the high-purity manganese-containing solution described in step S2 is less than 10 mg / L.

[0013] As a further improvement, the battery-grade manganese sulfate obtained in step S3 has a purity of not less than 99.5%, and the content of single impurities such as cobalt, nickel, and lithium is less than 10 ppm.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) Extremely short process: This invention replaces the multi-step chemical precipitation and impurity removal in the traditional process with two core steps: "directional leaching and lattice doping" and "lattice locking and deep impurity removal", which greatly shortens the lengthy process and realizes "short-range" preparation.

[0015] (2) High selectivity and high product purity: By utilizing the principle of "lattice doping", impurity ions are selectively fixed in the manganese-based compound lattice, rather than simple co-precipitation, resulting in extremely high separation efficiency. The obtained high-purity manganese-containing liquid can directly crystallize battery-grade manganese sulfate with extremely low (<10ppm) content of impurities such as Co, Ni, and Li.

[0016] (3) High manganese yield: Due to the avoidance of multiple precipitation-dissolution processes, the direct recovery rate of manganese is significantly improved (>95%). Combined with optional selective desorption steps, a closed-loop recycling of manganese can be achieved, and the total yield can approach 99%.

[0017] (4) Low cost and environmentally friendly: The process flow is short, the reagent consumption is low, the amount of wastewater and waste residue generated is small, and the economic and environmental benefits are significant. Detailed Implementation

[0018] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0019] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0020] 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.

[0021] In some specific embodiments, the method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder of the present invention includes the following steps: S1. Directional Leaching and Lattice Doping: Ternary lithium battery cathode material powder is mixed with sulfuric acid solution and a reducing agent for leaching reaction, while a lattice dopant is added to the reaction system. After the reaction is completed, solid-liquid separation is performed to obtain leachate and residue containing aluminum and copper.

[0022] Preferably, the concentration of the sulfuric acid solution is 0.5-2 mol / L.

[0023] Preferably, the leaching reaction is carried out at 50-90°C.

[0024] Preferably, the redox potential of the reaction system is controlled within the range of 200-400 mV (vs. SHE), and the final pH value is controlled within the range of 1.5-3.0. Maintaining the redox potential within this range ensures that all high-valent manganese is fully reduced to Mn. 2+ Furthermore, it can prevent certain impurities from undergoing adverse valence state changes. Maintaining the pH within the above range ensures leaching efficiency; if the pH is too high, Fe... 3+ Al 3 + Impurities and some Mn 2+ Hydrolysis may occur prematurely, forming hydroxide precipitates that could affect subsequent steps.

[0025] Preferably, the reducing agent is one of hydrogen peroxide, sodium sulfite, and sodium thiosulfate. The amount of reducing agent added is controlled to bring the redox potential within the aforementioned range. Manganese in the positive electrode material of a ternary lithium battery typically exists in the original material with a +3 or +4 valence. High-valence manganese has poor solubility in acid, making leaching difficult. The role of the reducing agent is to reduce high-valence manganese to soluble divalent manganese, thereby achieving efficient manganese leaching.

[0026] Preferably, the lattice dopant is a phosphate, and the amount added is 1.0-1.5 times the theoretical amount, which is the amount required to completely precipitate 10-30% of the manganese ions in the leachate.

[0027] The addition of lattice dopant during leaching is necessary and plays a crucial role. Adding lattice dopant simultaneously with the leaching reaction ensures that the dopant interacts with impurity ions the instant they dissolve from the ternary solid. During this dynamic leaching process, the concentrations of various ions are locally very high. The dopant preferentially combines with some manganese ions and impurity ions such as cobalt and nickel, forming extremely small, complex phosphate complex precursors or nuclei. If leaching is allowed to complete, and all ions are already uniformly dispersed in the solution, adding dopant at this point will significantly reduce the efficiency of impurity capture (i.e., the lattice doping effect) in the subsequent precipitation process due to the lack of the impurity-rich "oriented" precursor formed in step S1, resulting in substandard impurity removal.

[0028] S2. Lattice Locking and Deep Impurity Removal: A precipitant is added to the leachate obtained in step S1 to react with the precipitant, causing some of the manganese ions in the solution to form a sparingly soluble manganese-based compound precipitate. Simultaneously, impurity ions (cobalt, nickel, and lithium ions) in the solution are captured and incorporated into the lattice of this precipitate. After the reaction is complete, solid-liquid separation is performed to obtain a high-purity manganese-containing solution and a manganese-based compound precipitate rich in impurities.

[0029] Preferably, the reaction is carried out at 60-80°C with stirring for 1-3 hours.

[0030] Preferably, the precipitant is a soluble phosphate that can form an insoluble compound with manganese. The amount of precipitant added is 1.05-1.2 times the theoretical amount required to completely precipitate the remaining manganese ions in the solution (70-90% of the manganese ions in the leachate).

[0031] Preferably, the total content of cobalt, nickel, and lithium impurities in the high-purity manganese-containing solution is less than 10 mg / L.

[0032] The microscopic precursors / nuclei containing impurities formed in S1 serve as "seeds" or "templates" for subsequent precipitation reactions. When a large amount of precipitant is added in S2, manganese ions rapidly grow into insoluble manganese-based compound precipitates using these precursors as cores. Because the ionic radii of the impurity ions are close to those of the manganese ions, they are "locked" in the newly formed manganese compound lattice and removed along with the precipitate. Since the impurity ions can replace the manganese ions in forming phosphate ions to form a precipitate, most of the manganese ions remain in the solution, resulting in a high-purity manganese-containing solution.

[0033] S3. Evaporation and crystallization: The high-purity manganese-containing solution obtained in step S2 is concentrated, evaporated and crystallized, centrifuged and dried to obtain battery-grade manganese sulfate product.

[0034] Preferably, the obtained battery-grade manganese sulfate has a purity of not less than 99.5%, and the content of single impurities such as cobalt, nickel, and lithium is less than 10 ppm.

[0035] Preferably, the process further includes step S4: selective desorption and manganese recovery: the manganese-based compound precipitate rich in impurities obtained in step S2 is leached with a 0.5-2 mol / L dilute sulfuric acid solution by stirring, selectively desorbing the manganese ions encapsulated in the precipitate, obtaining a manganese-containing desorption solution and a secondary precipitate enriched with cobalt, nickel, and lithium. The manganese-containing desorption solution is returned to the leaching process of step S1 for recycling.

[0036] The method of this invention achieves efficient and selective separation of manganese and impurity metals simultaneously during the leaching process. The process is extremely simple, with high manganese yield, good product purity, and can directly meet battery-grade standards at a low cost.

[0037] Example 1 100g of ternary lithium battery cathode material powder (NCM523, composition: Ni: 20.1%, Co: 12.5%, Mn: 19.8%, Li: 6.2%) was mixed with 2 mol / L sulfuric acid solution at a liquid-to-solid ratio (mass ratio) of 5:1, and an appropriate amount of hydrogen peroxide was added as a reducing agent. Sodium dihydrogen phosphate was added as a lattice dopant, the amount of which was the theoretical amount required to precipitate 10g of manganese. The redox potential of the reaction system was 300mV. The mixture was stirred and leached at 80℃ for 2 hours, and the final pH of the reaction was controlled at 2.0.

[0038] After leaching, the solution is filtered to obtain leachate and aluminum-containing slag.

[0039] Sodium phosphate solution was added to the leachate as a precipitant (the amount used was 1.1 times the theoretical amount of remaining manganese to be precipitated), and the mixture was stirred at 70°C for 2 hours. After the reaction was completed, the solution was filtered to obtain a high-purity manganese-containing solution and a manganese phosphate precipitate rich in Co, Ni, and Li.

[0040] The high-purity manganese-containing solution was analyzed, with Co < 2 mg / L, Ni < 3 mg / L, and Li < 5 mg / L. The solution was evaporated and concentrated, cooled to crystallize, centrifuged, and dried to obtain 46.2 g of battery-grade manganese sulfate. ICP testing showed that the product purity reached 99.5%, and the content of all impurities was far below the standard requirements of GB / T 23834-2018 for battery-grade manganese sulfate.

[0041] The manganese phosphate precipitate rich in impurities is desorbed with 1 mol / L sulfuric acid, and the desorbed solution is returned to the next leaching process.

[0042] Comparative Example 1 Using the same raw materials as in Example 1 and employing conventional processes, the process involved leaching with sulfuric acid and hydrogen peroxide, followed by sequential removal of aluminum through neutralization, copper through sodium sulfide, and calcium and magnesium through sodium fluoride. Nickel and cobalt were then separated by P507 extraction, and finally, manganese solution was crystallized. The final product yielded 40.1g of manganese sulfate. The process consisted of six steps, took up to 12 hours, and contained 25 ppm of cobalt.

[0043] The comparison shows that the method of the present invention is significantly superior to the traditional method in terms of process length, recovery rate and product purity.

[0044] Comparative Example 2 The same raw materials as in Example 1 were used, except that no lattice dopant was added during leaching, and after leaching, a sodium phosphate solution was added to the leachate (the molar amount of phosphate was the same as the total molar amount of sodium dihydrogen phosphate and sodium phosphate in Example 1). The manganese-containing solution was evaporated, concentrated, cooled, crystallized, centrifuged, and dried. The resulting manganese sulfate product, after ICP testing, had a purity of only 85.7%. The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Therefore, any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder, characterized in that, Includes the following steps: S1. The ternary lithium battery cathode material powder is mixed with sulfuric acid solution and reducing agent to carry out leaching reaction. At the same time, a lattice dopant is added to the reaction system. After the reaction is completed, solid-liquid separation is carried out to obtain leaching solution and residue containing aluminum and copper. During the leaching reaction, the redox potential of the reaction system is controlled at 200-400 mV, and the pH value at the reaction endpoint is controlled at 1.5-3.

0. The lattice dopant is a phosphate, and its addition amount is 1.0-1.5 times the theoretical amount, which is the amount required to completely precipitate 10-30% of the manganese ions in the leachate; S2. Add a precipitant to the leachate obtained in step S1 and react. After the reaction is complete, perform solid-liquid separation to obtain a high-purity manganese-containing solution and a manganese-based compound precipitate rich in impurities. The precipitant is a soluble phosphate, and the amount added is 1.05-1.2 times the theoretical amount required to completely precipitate the remaining manganese ions in the solution. S3. The high-purity manganese-containing solution obtained in step S2 is concentrated, evaporated and crystallized, centrifuged and dried to obtain battery-grade manganese sulfate product.

2. The method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder according to claim 1, characterized in that, The process also includes step S4: leaching the manganese-based compound precipitate rich in impurities obtained in step S2 with dilute sulfuric acid solution by stirring to obtain a manganese-containing desorption solution and a secondary precipitate enriched with cobalt, nickel, and lithium. The manganese-containing desorption solution is then returned to the leaching process in step S1 for recycling.

3. The method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder according to claim 1 or 2, characterized in that, The leaching reaction temperature in step S1 is 50-90℃.

4. The method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder according to claim 1 or 2, characterized in that, The concentration of the sulfuric acid solution in step S1 is 0.5-2 mol / L.

5. The method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder according to claim 1 or 2, characterized in that, The reducing agent mentioned in step S1 is one of hydrogen peroxide, sodium sulfite, and sodium thiosulfate.

6. The method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder according to claim 1 or 2, characterized in that, Step S2 is carried out at 60-80℃ with stirring.

7. The method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder according to claim 1 or 2, characterized in that, In the high-purity manganese-containing solution described in step S2, the total content of cobalt, nickel, and lithium impurities is less than 10 mg / L.

8. The method for preparing battery-grade manganese sulfate from ternary lithium battery cathode material powder according to claim 1 or 2, characterized in that, The battery-grade manganese sulfate obtained in step S3 has a purity of not less than 99.5%, and the content of single impurities such as cobalt, nickel, and lithium is less than 10 ppm.