A method for comprehensively recovering and treating the cathode material of waste lithium iron manganese phosphate batteries

Abstract

The present invention relates to a method for comprehensively recycling and treating the cathode material of waste lithium iron phosphate manganese batteries. A lithium leaching solution and a manganese-iron-phosphorus leaching solution are configured to sequentially leach the corresponding lithium and phosphorus in the cathode powder of waste lithium iron phosphate manganese batteries to obtain a lithium leaching solution and a solution containing manganese, iron, and phosphorus. After purification and refinement of the lithium leaching solution after leaching, high-purity lithium carbonate is obtained. The iron ions in the solution containing manganese, iron, and phosphorus after leaching are reduced to divalent iron ions, and after adding alkali for neutralization and filtration, crude manganese iron phosphate [II] is obtained. The crude manganese iron phosphate [II] is dissolved with a phosphoric acid solution, and the dissolved manganese iron phosphate [II] solution is injected into a reaction kettle at a certain flow rate to prepare a manganese iron phosphate precursor. At the same time, an alkali solution is injected into the reaction kettle at a certain ratio and flow rate. After filtration, the filter residue is taken and dried to obtain the manganese iron phosphate precursor. The present invention can achieve the comprehensive recycling of the cathode material of waste batteries, and high-value-added products such as battery-grade lithium carbonate and the precursor of the cathode material of lithium iron phosphate manganese batteries, manganese iron phosphate, are obtained during the recycling process.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery recycling, and relates to a method for treating waste lithium iron manganese phosphate batteries, in particular to a method for comprehensively recycling and treating the cathode materials of waste lithium iron manganese phosphate batteries. Background Art

[0002] LiFePO4 is one of the most widely used cathode materials for lithium-ion batteries in the current market, with advantages such as good cycle performance, safety and stability, and high cost performance. However, its further development is restricted by disadvantages such as low operating voltage, low conductivity, and insufficient rate performance. By combining Fe and Mn, using Mn-doped LiFePO4 as the cathode material for lithium-ion batteries - lithium iron manganese phosphate, various defects of LiFePO4 can be overcome. Compared with ternary materials, lithium iron manganese phosphate has high cost performance, high safety, and long cycle life; compared with lithium iron phosphate, lithium iron manganese phosphate has high energy density and good low-temperature performance. After the cost is reduced with the rapid advancement of industrialization, the replacement of the share of lithium iron phosphate can be accelerated. At present, battery companies and cathode material manufacturers are actively deploying the production capacity of lithium iron manganese phosphate. Industry analysts predict that domestic stable mass production will be achieved at the latest in 2023 and will be applied on a large scale. Currently, battery manufacturers with lithium iron manganese phosphate technology reserves include: CATL, BYD, Guoxuan High-Tech, etc., mainly focusing on patent technology research and development and investment layout. Currently, cathode material manufacturers that have already deployed in lithium iron manganese phosphate include: DFD Nanotech, Pengxin Resources, Dongsheng Technology, Zhongbei New Materials, Tianjin Strand, etc.

[0003] With the wide application of the cathode material of lithium manganese iron phosphate batteries, how to recycle waste lithium manganese iron phosphate batteries and achieve a closed-loop of battery materials has become a research hotspot for enterprises and scientific workers. A Chinese patent with the patent number CN 108736090 B discloses a recycling method for waste lithium manganese iron phosphate batteries, including the following steps: "First, dissolve the cathode material of the lithium manganese iron phosphate battery in an oxidizing acid solution, obtain an oxidized acidified slurry through an oxidation reaction, and then filter to obtain a lithium-rich solution and a manganese-iron slag, where the manganese-iron slag is a mixture of manganese oxide and iron phosphate; the lithium-rich solution is purified to obtain a lithium-rich purified solution, and the lithium-rich purified solution is precipitated with sodium carbonate to obtain lithium carbonate; the manganese-iron slag is roasted with sodium hydroxide, the obtained roasted material is dissolved in water to obtain an aqueous roasted material, and the aqueous roasted material is filtered to obtain a sodium manganate solution and iron phosphate; the sodium manganate solution is added with a reducing agent and undergoes an oxidation-reduction reaction to obtain manganese dioxide." This technical solution realizes the recycling of the cathode material of the lithium manganese iron phosphate battery and obtains lithium carbonate, iron phosphate, and manganese oxide products. However, this process requires roasting, has high energy consumption, and does not purify and deeply process the iron phosphate and manganese oxide products. Therefore, the present invention aims to develop a method that can achieve the full-component recycling of the cathode material of the lithium manganese iron phosphate battery with low energy consumption, and at the same time prepare battery-grade lithium carbonate and the precursor of the cathode material of the lithium manganese iron phosphate battery, iron manganese phosphate, to improve the added value of the product and better meet the actual production needs. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for the full-component recycling treatment of the cathode material of waste lithium manganese iron phosphate batteries, so as to solve the technical problem in the prior art that the full-component recycling of the cathode material of lithium manganese iron phosphate batteries cannot be achieved with low energy consumption and at the same time prepare the precursor products of battery-grade lithium carbonate and the cathode material of lithium manganese iron phosphate batteries.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] A method for the full-component recycling treatment of the cathode material of waste lithium manganese iron phosphate batteries, the key is to configure a lithium leaching solution and a manganese-iron-phosphorus leaching solution to successively leach the corresponding lithium and phosphorus in the cathode powder of the waste lithium manganese iron phosphate battery to obtain a lithium leaching solution and a solution containing manganese, iron, and phosphorus;

[0007] After purification and refinement of the leached lithium leaching solution, high-purity lithium carbonate is obtained;

[0008] Reduce the iron ions in the solution containing manganese, iron, and phosphorus after leaching to divalent iron ions, neutralize with alkali and then filter to obtain crude iron manganese phosphate [Ⅱ];

[0009] Dissolve the crude iron manganese phosphate [Ⅱ] with phosphoric acid solution, inject the dissolved iron manganese phosphate [Ⅱ] solution into the reaction kettle at a certain flow rate to prepare the precursor of iron manganese phosphate. At the same time, inject an alkali solution into the reaction kettle at a certain ratio and flow rate, and after filtration, take the filter residue and dry it to obtain the precursor of iron manganese phosphate.

[0010] Specifically, it includes the following steps:

[0011] A. Prepare lithium leaching solution and manganese iron phosphorus leaching solution:

[0012] a. Use hydrogen peroxide, sodium persulfate and sulfuric acid to prepare lithium leaching solution for standby;

[0013] b. Use acid solution as manganese iron phosphorus leaching solution for standby;

[0014] B. Prepare battery-grade lithium carbonate: Take the positive electrode powder, add lithium leaching solution to it for leaching. After the leaching is completed, conduct the first filtration. The obtained filtrate is the lithium leaching solution. Process the lithium leaching solution in the order of purification and impurity removal - concentration and precipitation - carbonation purification to obtain battery-grade lithium carbonate;

[0015] C. Prepare crude manganese iron phosphate [Ⅱ]: Mix the filter residue obtained from the first filtration with manganese iron phosphorus leaching solution for reaction. After the reaction is completed, conduct the second filtration. The obtained filtrate is the solution containing manganese, iron and phosphorus. Add reducing iron powder to the filtrate to reduce the trivalent iron ions in the filtrate to divalent ferrous ions. Add alkali to the filtrate for neutralization and precipitation. The filter residue obtained after the third filtration after sufficient precipitation is crude manganese iron phosphate [Ⅱ];

[0016] D. Prepare manganese iron phosphate precursor: Add phosphoric acid solution to crude manganese iron phosphate [Ⅱ] to just dissolve the crude manganese iron phosphate [Ⅱ]. Add manganese sulfate to the dissolved solution to obtain manganese iron phosphate [Ⅱ] solution. Use a peristaltic pump to pump the dissolved manganese iron phosphate [Ⅱ] solution and alkali solution into the precursor reaction kettle in proportion to prepare manganese iron phosphate precursor. After the preparation is completed, conduct the fourth filtration to take the filter residue. After drying the filter residue, obtain manganese iron phosphate precursor.

[0017] In the step A, the mass fraction of sulfuric acid in the lithium leaching solution is 0.1% - 10%, the mass fraction of hydrogen peroxide is 1% - 8%, and the mass fraction of sodium persulfate is 0.1% - 1%;

[0018] The manganese iron phosphorus leaching solution is one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and the mass fraction of the acid is 5% - 50%.

[0019] Before adding lithium leaching solution to the positive electrode powder for leaching in the step B, water needs to be added to make the solid-liquid ratio of the positive electrode powder to water 1:5 - 20;

[0020] When adding lithium leaching solution to the positive electrode powder for leaching, pH monitoring needs to be carried out simultaneously. Stop adding lithium leaching solution when the pH reaches 4.0 - 4.5. The leaching temperature is 50 - 90°C, the leaching time is 20 - 120 min, and the stirring speed during the leaching process is 250 - 600 r / min;

[0021] In the process of purification and impurity removal, an alkali solution needs to be added to adjust the pH to 8 - 10, so that iron ions and manganese ions in the solution form hydroxide precipitates, and then centrifugal separation can be carried out;

[0022] In the process of concentration and precipitation, the solution obtained in the above purification and impurity removal process needs to be heated and concentrated first. During the heating and concentration process, sodium carbonate solution is added to the solution to obtain crude lithium carbonate;

[0023] In the process of purification by carbonation method, the crude lithium carbonate is prepared into battery-grade lithium carbonate.

[0024] In step C, manganese-iron-phosphorus leaching solution is added to the filter residue, and the filter residue reacts with the manganese-iron-phosphorus leaching solution. The addition of the manganese-iron-phosphorus leaching solution is stopped when the pH reaches 0 - 0.5; the leaching temperature is 75 - 90 °C, the leaching time is 30 - 120 min; the stirring speed during the leaching process is 250 - 600 r / min;

[0025] During the process of adding alkali for neutralization and precipitation, the pH of the solution needs to be adjusted to 4.5 - 5.5.

[0026] In step D, the mass fraction of the phosphoric acid solution added to the crude manganese iron (II) phosphate is 5% - 15%; after the phosphoric acid dissolves the crude manganese iron (II) phosphate, a phosphoric acid solution with pH = 2 needs to be added to dilute it so that the molar concentration of manganese iron phosphate in the solution is 1 - 3 mol / L;

[0027] The diluted manganese iron phosphate solution is added to the reaction kettle through a peristaltic pump at a rate of 0.2 - 1.2 ml / L. The addition rate of the alkali solution to the reaction kettle is adjusted by feedback from a pH meter to maintain the pH of the reaction kettle at 4.5 - 5.5;

[0028] During the preparation of the manganese iron phosphate precursor, an inert gas needs to be introduced into the reaction kettle for protection. The inert gas is one of nitrogen, helium, and argon. The temperature of the reaction kettle is controlled by an oil bath to maintain the temperature of the reaction kettle at 45 - 55 °C. The stirring speed in the reaction kettle is 700 - 1000 r / min, and the reaction time is 600 - 1800 min.

[0029] In steps C and D, the molar concentration of the added alkali solution is 1 - 3 mol / L. The added alkali solution can be ammonia water, a mixed solution of ammonia water and sodium hydroxide, or a mixed solution of ammonia water and potassium hydroxide.

[0030] When the alkali solution is a mixed solution of ammonia water and sodium hydroxide, the molar concentration of ammonia water is greater than that of sodium hydroxide.

[0031] When the alkali solution is a mixed solution of ammonia water and potassium hydroxide, the molar concentration of ammonia water is greater than that of potassium hydroxide.

[0032] The beneficial effects of adopting the above technical solutions are as follows:

[0033] A method for comprehensively recovering and treating the cathode material of waste lithium iron phosphate manganese batteries provided by the present invention utilizes the synergistic oxidation of hydrogen peroxide and sodium persulfate, as well as the difference in the leaching pH values of lithium, manganese, iron, and phosphorus in lithium iron phosphate manganese, to achieve the targeted leaching of lithium, manganese, iron, and phosphorus. Under the conditions of introducing an inert gas into the lithium iron phosphate manganese solution and adding ammonia in the presence of amine, Fe2+, Mn2+, and PO43+ co-precipitate in the form of lithium iron phosphate [II] in an environment with a pH of 4.5 - 5.5. Among them, the amine can coordinate with Fe2+ and Mn2+, enabling manganese and iron to co-precipitate.

[0034] Compared with the traditional recovery process, the method provided by the present invention not only reduces the recovery energy consumption but also enables the comprehensive recovery of the cathode material of waste batteries. During the recovery process, products such as battery-grade lithium carbonate and the precursor of the cathode material of lithium iron phosphate manganese batteries, lithium iron phosphate, are obtained. The added value of the products is high, which can improve the economic benefits of enterprises and better meet the needs of actual production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a process diagram of a method for comprehensively recovering and treating the cathode material of waste lithium iron phosphate manganese batteries provided by the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In order to better understand the purpose, structure, and function of the present invention, the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0037] As Figure 1 shown, the present invention provides a method for comprehensively recovering and treating the cathode material of waste lithium iron phosphate manganese batteries. The key is to configure a lithium leaching solution and a manganese, iron, and phosphorus leaching solution to successively leach the corresponding lithium and phosphorus in the cathode powder of waste lithium iron phosphate manganese batteries to obtain a lithium leaching solution and a solution containing manganese, iron, and phosphorus. Utilizing the difference in the leaching pH values of lithium, manganese, iron, and phosphorus in lithium iron phosphate manganese, the targeted leaching of lithium, manganese, iron, and phosphorus is achieved;

[0038] After the leached lithium leaching solution is purified to remove impurities, concentrated and precipitated, sodium carbonate is added to obtain a crude lithium carbonate precipitate, which is then purified by carbonation to obtain battery-grade lithium carbonate;

[0039] Reduce the iron ions in the leached manganese-iron-phosphorus solution to divalent iron ions, filter to obtain crude manganese iron phosphate [II] after adding alkali for neutralization, dissolve the crude manganese iron phosphate [II] with phosphoric acid solution, and inject the dissolved manganese iron phosphate [II] solution into the reaction kettle at a certain flow rate. At the same time, inject an alkali solution into the reaction kettle at a certain ratio and flow rate, and introduce an inert gas into the reaction kettle for protection. Under the conditions of introducing an inert gas and the presence of an amine into the manganese iron phosphate solution, Fe2+, Mn2+, and PO43+ co-precipitate in the form of manganese iron phosphate [II] in an environment with a pH of 4.5 - 5.5. The amine can coordinate with Fe2+ and Mn2+, enabling the co-precipitation of manganese and iron, thereby preparing a manganese iron phosphate precursor. After filtration, the filter residue is taken and dried to obtain the manganese iron phosphate precursor.

[0040] Example 1

[0041] As Figure 1 shown, a method for comprehensively recycling and treating the cathode material of waste lithium manganese iron phosphate batteries in this example specifically includes the following steps:

[0042] A. Prepare a lithium leaching solution and a manganese-iron-phosphorus leaching solution: Use hydrogen peroxide, sodium persulfate, and sulfuric acid to prepare a lithium leaching solution for standby, where the mass fraction of sulfuric acid is 6%, the mass fraction of sodium persulfate is 0.1%, and the mass fraction of hydrogen peroxide is 4%;

[0043] Prepare a sulfuric acid solution with a mass fraction of 10% as the manganese-iron-phosphorus leaching solution for standby;

[0044] B. Prepare battery-grade lithium carbonate: Weigh 100 g of lithium manganese iron phosphate cathode powder, and use ICP to measure the contents of each component in the cathode powder as follows: lithium 3.9%, manganese 21.3%, iron 9.7%, and phosphorus 14.1%. Add 1000 g of water to the cathode powder, and then continuously add the lithium leaching solution to the cathode powder for leaching until the addition of the lithium leaching solution is stopped when the pH = 4.0. Leach for 20 minutes in an environment at 80°C, and during the leaching process, the stirring speed is 500 r / min. After the leaching is completed, the filtrate obtained from the first filtration is the lithium leaching solution. Add a 2 mol / L potassium hydroxide solution to the lithium leaching solution to adjust the pH of the lithium leaching solution to 9. The iron ions and manganese ions in the solution form hydroxide precipitates, and after centrifugal separation, the purified lithium leaching solution is obtained. Evaporate and concentrate it until crystals start to precipitate, then add 300 mL of a 1.5 mol / L sodium carbonate solution to it. After centrifugation, a crude lithium carbonate precipitate is obtained, and it is purified by the carbonization method to obtain high-purity lithium carbonate. After drying, the lithium carbonate product weighs 18.8 g, and the recovery rate of lithium is 91%;

[0045] C. Preparation of crude manganese iron (II) phosphate: Add 500 g of water to the filter residue obtained from the first filtration, then add the manganese iron phosphorus leaching solution thereto until the pH of the solution is 0.5, and leach for 100 minutes at 75 °C. During the leaching process, the stirring speed is 250 r / min. After the leaching is completed, perform the second filtration to obtain a solution containing manganese, iron, and phosphorus. Add 5 g of reduced iron powder to the filtrate to reduce ferric ions to ferrous ions. Then, add alkali to the filtrate to neutralize and precipitate. After sufficient precipitation, perform the third filtration, and the obtained filter residue is crude manganese iron (II) phosphate;

[0046] D. Preparation of manganese iron phosphate precursor: Add a phosphoric acid solution with a mass fraction of 5% to the crude manganese iron (II) phosphate to just dissolve the crude manganese iron (II) phosphate. After dissolution, add 0.5 g of battery-grade manganese sulfate dihydrate thereto to make the molar ratio of manganese to iron 6:4, obtaining a manganese iron phosphate solution. Add a phosphoric acid solution with pH = 2 to the solution to dilute the manganese iron phosphate solution to 200 mL, so that the molar concentration of manganese iron phosphate in the solution is 1.1 mol / L. Add the manganese iron phosphate solution and an ammonia water solution with a molar concentration of 1 mol / L into the reaction kettle through two peristaltic pumps respectively. Among them, the flow rate of the manganese iron phosphate solution is 0.2 mL / min, and the addition rate of ammonia water to the reaction kettle is adjusted according to the information fed back by the pH meter to maintain the pH of the reaction kettle at 4.5. At 45 °C, control the stirring speed in the reaction kettle at 700 r / min, introduce nitrogen into the reaction kettle, and the solution in the reaction kettle reacts for 1200 min under nitrogen protection. After the reaction is completed, perform the fourth filtration, and take the filter residue for washing and drying to obtain the manganese iron phosphate precursor, that is, the (Fe0.4Mn0.6)3(PO4)2 precursor.

[0047] The detection results of the components of the high-purity lithium carbonate prepared in this example are as follows in the table:

[0048] Table 1 Detection results of the components of high-purity lithium carbonate in Example 1

[0049]

[0050] The parameters of the manganese iron phosphate precursor prepared in this example are as follows in the table:

[0051] Table 2 Detection results of the parameters of the manganese iron phosphate precursor in Example 1

[0052]

[0053] Example 2

[0054] As Figure 1 shown, a method for comprehensively recycling and treating the cathode material of waste lithium manganese iron phosphate batteries in this example specifically includes the following steps:

[0055] A. Preparation of lithium leaching solution and manganese-iron-phosphorus leaching solution: Prepare a lithium leaching solution for standby using hydrogen peroxide, sodium persulfate, and sulfuric acid. Among them, the mass fraction of sulfuric acid is 6%, the mass fraction of sodium persulfate is 0.1%, and the mass fraction of hydrogen peroxide is 4%.

[0056] Prepare a sulfuric acid solution with a mass fraction of 10% as the manganese-iron-phosphorus leaching solution for standby;

[0057] B. Preparation of battery-grade lithium carbonate: Weigh 100 g of lithium iron phosphate cathode powder. Using ICP, the contents of each component in the cathode powder are measured as follows: lithium 3.9%, manganese 21.3%, iron 9.7%, and phosphorus 14.1%. Add 1000 g of water to the cathode powder, and then continuously add the lithium leaching solution to the cathode powder for leaching until the pH = 4.3, then stop adding the lithium leaching solution. Leach for 20 minutes at 80 °C. During the leaching process, the stirring speed is 500 r / min. After the leaching is completed, the filtrate obtained from the first filtration is the lithium leaching solution. Add a 2 mol / L potassium hydroxide solution to the lithium leaching solution to adjust the pH of the lithium leaching solution to 9, and then perform centrifugal separation to obtain the purified lithium leaching solution. Evaporate and concentrate it until crystals start to precipitate, then add 300 mL of a 1.5 mol / L sodium carbonate solution to it. After centrifugation, a crude lithium carbonate precipitate is obtained, and it is purified by the carbonization method to obtain high-purity lithium carbonate. After drying, weigh to obtain 18.6 g of lithium carbonate product, and the lithium recovery rate is 90%;

[0058] C. Preparation of crude manganese iron (II) phosphate: Add 500 g of water to the filter residue obtained from the first filtration, and then add the manganese-iron-phosphorus leaching solution to it until the pH of the solution is 0.5. Leach for 100 minutes at 75 °C. During the leaching process, the stirring speed is 250 r / min. After the leaching is completed, perform a second filtration to obtain a solution containing manganese, iron, and phosphorus. Add 5 g of reduced iron powder to the filtrate to reduce ferric ions to ferrous ions, and then add alkali to neutralize and precipitate. After sufficient precipitation, the filter residue obtained from the third filtration is the crude manganese iron (II) phosphate;

[0059] D. Preparation of manganese iron phosphate precursor: Add phosphoric acid solution with a mass fraction of 5% to crude manganese iron phosphate [II] until the crude manganese iron phosphate [II] is just dissolved. After dissolution, add 0.5 g of battery-grade manganese sulfate dihydrate to it to make the molar ratio of manganese to iron 6:4, obtaining a manganese iron phosphate solution. Add phosphoric acid solution with pH = 2 to dilute the manganese iron phosphate solution to 200 mL, so that the molar concentration of manganese iron phosphate in the solution is 1.1 mol / L. Add the manganese iron phosphate solution and ammonia water solution with a molar concentration of 1 mol / L into the reaction kettle through two peristaltic pumps respectively. Among them, the flow rate of the manganese iron phosphate solution is 0.5 mL / min, and the addition rate of ammonia water into the reaction kettle is adjusted according to the information feedback by the pH meter to maintain the pH of the reaction kettle at 4.5. Under the environment of 45 °C, control the stirring speed in the reaction kettle at 700 r / min, introduce nitrogen into the reaction kettle, and the solution in the reaction kettle reacts for 1200 min under nitrogen protection. After the reaction is completed, perform the fourth filtration, and take the filter residue for washing and drying to obtain the manganese iron phosphate precursor, that is, the (Fe0.4Mn0.6)3(PO4)2 precursor.

[0060] The detection results of the components of the high-purity lithium carbonate prepared in this example are as follows in the table:

[0061] Table 3 Detection results of the components of high-purity lithium carbonate in Example 2

[0062]

[0063] The parameters of the manganese iron phosphate precursor prepared in this example are as follows in the table:

[0064] Table 4 Detection results of the parameters of the manganese iron phosphate precursor in Example 2

[0065]

[0066] Example 3

[0067] A method for comprehensively recycling and treating the cathode material of waste lithium manganese iron phosphate batteries in this example specifically includes the following steps:

[0068] A. Prepare lithium leaching solution and manganese iron phosphorus leaching solution: Prepare lithium leaching solution for standby using hydrogen peroxide, sodium persulfate and sulfuric acid, where the mass fraction of sulfuric acid is 0.5%, the mass fraction of sodium persulfate is 1%, and the mass fraction of hydrogen peroxide is 2%;

[0069] Prepare sulfuric acid solution with a mass fraction of 10% as manganese iron phosphorus leaching solution for standby.

[0070] B. Preparation of battery-grade lithium carbonate: Weigh 100 g of lithium iron phosphate cathode powder. Using ICP, the contents of each component in the cathode powder are measured as follows: lithium 3.9%, manganese 21.3%, iron 9.7%, and phosphorus 14.1%. Add 800 g of water to the cathode powder, and then continuously add lithium leaching solution to the cathode powder for leaching until the pH = 4.5, then stop adding the lithium leaching solution. Leach for 100 minutes at 50 °C. During the leaching process, the stirring speed is 300 r / min. After the leaching is completed, the filtrate obtained by the first filtration is the lithium leaching solution. Add 1 mol / L sodium hydroxide solution to the lithium leaching solution to adjust the pH of the lithium leaching solution to 9, and then perform centrifugal separation to obtain the purified lithium leaching solution. Evaporate and concentrate it until crystals start to precipitate, then add 400 mL of 1 mol / L sodium carbonate solution to it. After centrifugation, obtain the crude lithium carbonate precipitate, and purify it by the carbonation method to obtain high-purity lithium carbonate. After drying, weigh to obtain 18.6 g of lithium carbonate product, and the recovery rate of lithium is 90%;

[0071] C. Preparation of crude manganese iron phosphate [Ⅱ]: Add 800 g of water to the filter residue obtained by the first filtration, and then add manganese iron phosphorus leaching solution to it until the pH of the solution is 0. Leach for 30 minutes at 90 °C. During the leaching process, the stirring speed is 500 r / min. After the leaching is completed, perform the second filtration to obtain a solution containing manganese, iron, and phosphorus. Add 5 g of reduced iron powder to the filtrate to reduce ferric ions to ferrous ions, and then add alkali to neutralize and precipitate in the filtrate. After sufficient precipitation, perform the third filtration, and the filter residue obtained is the crude manganese iron phosphate [Ⅱ];

[0072] D. Preparation of manganese iron phosphate precursor: Add a phosphoric acid solution with a mass fraction of 8% to the crude manganese iron phosphate [Ⅱ] to just dissolve the crude manganese iron phosphate [Ⅱ]. After dissolution, add 37 g of manganese sulfate dihydrate and 60 g of sodium phosphate to it to make the molar ratio of manganese to iron 7:3, obtaining a manganese iron phosphate solution. Add phosphoric acid with a pH of 2 to dilute the solution to 200 mL, so that the molar concentration of manganese iron phosphate in the solution is 1.4 mol / L. Add the manganese iron phosphate solution and an ammonia water solution with a molar concentration of 2 mol / L into the reaction kettle through two peristaltic pumps respectively. Among them, the flow rate of the manganese iron phosphate solution is 1.2 mL / min, and the speed of adding ammonia water to the reaction kettle is adjusted according to the information fed back by the pH meter to maintain the pH of the reaction kettle at 5.0. At 55 °C, control the stirring speed in the reaction kettle at 1000 r / min, and introduce nitrogen into the reaction kettle. The solution in the reaction kettle reacts for 800 min under nitrogen protection. After the reaction is completed, perform the fourth filtration, and take the filter residue, wash and dry it to obtain the manganese iron phosphate precursor, that is, the (Fe0.3Mn0.7)3(PO4)2 precursor.

[0073] The detection results of the components of the high-purity lithium carbonate prepared in this example are as follows in the table:

[0074] Table 5 Detection Results of the Composition of High-Purity Lithium Carbonate in Example 3

[0075]

[0076] The parameters of the prepared iron manganese phosphate precursor in this example are as follows in the table:

[0077] Table 6 Detection Results of the Parameters of the Iron Manganese Phosphate Precursor in Example 3

[0078]

[0079] Comparative Example 1

[0080] The method for treating the cathode material of waste lithium iron manganese phosphate battery and preparing battery-grade lithium carbonate and iron manganese phosphate precursor in this comparative example includes the following steps:

[0081] A. Prepare lithium leaching solution and manganese iron phosphorus leaching solution: Prepare a lithium leaching solution for standby using hydrogen peroxide, sodium persulfate and sulfuric acid. The mass fraction of sulfuric acid is 6%, the mass fraction of sodium persulfate is 0.1%, and the mass fraction of hydrogen peroxide is 4%;

[0082] Prepare a sulfuric acid solution with a mass fraction of 10% as the manganese iron phosphorus leaching solution for standby;

[0083] B. Prepare battery-grade lithium carbonate: Weigh 100 g of lithium iron manganese phosphate cathode powder. The contents of each component in the cathode powder measured by ICP are as follows: lithium 3.9%, manganese 21.3%, iron 9.7%, and phosphorus 14.1%. Add 1000 g of water to the cathode powder, and then continuously add the lithium leaching solution to the cathode powder for leaching until the addition of the lithium leaching solution is stopped when pH = 5.5, and leach for 20 minutes in an environment of 80°C. During the leaching process, the stirring speed is 500 r / min. After the leaching is completed, the filtrate obtained by the first filtration is the lithium leaching solution. Add 2 mol / L potassium hydroxide to the lithium leaching solution to adjust the pH of the lithium leaching solution to 9, and centrifuge to obtain the purified lithium leaching solution. When it is evaporated and concentrated until crystals start to precipitate, add 300 mL of 1.5 mol / L sodium carbonate solution to it, and obtain a crude lithium carbonate precipitate after centrifugation. After purification by the carbonation method, high-purity lithium carbonate is prepared. After drying and weighing, 8.0 g of lithium carbonate product is obtained, and the lithium recovery rate is 39%;

[0084] C. Preparation of crude manganese iron (II) phosphate: Add 500 g of water to the filter residue obtained from the first filtration, then add the manganese iron phosphorus leaching solution to make the pH of the solution 0.5, and leach for 100 minutes at 75 °C. During the leaching process, the stirring speed is 250 r / min. After the leaching is completed, perform the second filtration to obtain a solution containing manganese, iron, and phosphorus. Add 5 g of reduced iron powder to the filtrate to reduce ferric ions to ferrous ions. Then, add alkali to the filtrate to neutralize and precipitate. After sufficient precipitation, perform the third filtration, and the filter residue obtained is crude manganese iron (II) phosphate;

[0085] D. Preparation of manganese iron phosphate precursor: Add a phosphoric acid solution with a mass fraction of 5% to the crude manganese iron (II) phosphate to just dissolve the crude manganese iron (II) phosphate. After dissolution, add 0.5 g of battery-grade manganese sulfate dihydrate to make the molar ratio of manganese to iron 6:4, obtaining a manganese iron phosphate solution. Add phosphoric acid with pH = 2 to dilute the solution to 200 mL, so that the molar concentration of manganese iron phosphate in the solution is 1.1 mol / L. Add the manganese iron phosphate solution and 1 mol / L ammonia water solution to the reaction kettle through two peristaltic pumps respectively. Among them, the flow rate of the manganese iron phosphate solution is 2.5 mL / min, and the speed of adding ammonia water to the reaction kettle is adjusted according to the information fed back by the pH meter to maintain the pH of the reaction kettle at 4.5. At 45 °C, control the stirring speed in the reaction kettle at 400 r / min, and introduce nitrogen into the reaction kettle. The solution in the reaction kettle reacts for 1200 min under the protection of nitrogen. After the reaction is completed, perform the fourth filtration, and take the filter residue, wash and dry it to obtain the manganese iron phosphate precursor, that is, the (Fe0.4Mn0.6)3(PO4)2 precursor.

[0086] The detection results of the components of the high-purity lithium carbonate prepared in this example are as follows in the table:

[0087] Table 7 Detection results of the components of the high-purity lithium carbonate in Example 1

[0088]

[0089] The parameters of the manganese iron phosphate precursor prepared in this example are as follows in the table:

[0090] Table 8 Detection results of the parameters of the manganese iron phosphate precursor in Example 1

[0091]

[0092] It is understood that the present invention is described by way of some embodiments. Those skilled in the art will know that, without departing from the spirit and scope of the present invention, various changes or equivalent substitutions can be made to these features and embodiments. Additionally, under the teaching of the present invention, these features and embodiments can be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A method for comprehensively recovering and treating the cathode material of waste lithium iron phosphate manganese batteries, characterized in that, Specifically, it includes the following steps: A. Prepare lithium leaching solution and manganese-iron-phosphorus leaching solution: a. Prepare lithium leaching solution for standby by using hydrogen peroxide, sodium persulfate and sulfuric acid; b. Use acid solution as manganese-iron-phosphorus leaching solution for standby; B. Prepare battery-grade lithium carbonate: Take the positive electrode powder, add lithium leaching solution to it for leaching. After the leaching is completed, conduct the first filtration. The obtained filtrate is the lithium leaching solution. Process the lithium leaching solution in the order of purification and impurity removal - concentration and precipitation - carbonation purification to obtain battery-grade lithium carbonate; C. Prepare crude manganese-iron-phosphorus [II] phosphate: Mix the filter residue obtained from the first filtration with manganese-iron-phosphorus leaching solution for reaction. After the reaction is completed, conduct the second filtration. The obtained filtrate is the solution containing manganese, iron and phosphorus. Add reduced iron powder to the filtrate to reduce ferric ions in the filtrate to ferrous ions. Add alkali to neutralize and precipitate in the filtrate. The filter residue obtained after sufficient precipitation and the third filtration is crude manganese-iron-phosphorus [II] phosphate; D. Prepare manganese-iron-phosphorus phosphate precursor: Add phosphoric acid solution to crude manganese-iron-phosphorus [II] phosphate to just dissolve the crude manganese-iron-phosphorus [II] phosphate. Add manganese sulfate to the dissolved solution to obtain manganese-iron-phosphorus [II] phosphate solution. Use a peristaltic pump to pump the dissolved manganese-iron-phosphorus [II] phosphate solution and alkali solution into the precursor reaction kettle in proportion to prepare the manganese-iron-phosphorus phosphate precursor. After the preparation is completed, conduct the fourth filtration to take the filter residue. After drying the filter residue, obtain the manganese-iron-phosphorus phosphate precursor; During the process of preparing the manganese-iron-phosphorus phosphate precursor, it is necessary to introduce inert gas into the reaction kettle for protection; The added alkali solution can be ammonia water, a mixed solution of ammonia water and sodium hydroxide, or a mixed solution of ammonia water and potassium hydroxide.

2. The method for comprehensively recycling and treating the cathode material of waste lithium iron phosphate manganese batteries according to claim 1, characterized in that, In the step A, the mass fraction of sulfuric acid in the lithium leaching solution is 0.1% - 10%, the mass fraction of hydrogen peroxide is 1% - 8%, and the mass fraction of sodium persulfate is 0.1% - 1%; The manganese-iron-phosphorus leaching solution is one or more of sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and the mass fraction of the acid is 5% - 50%.

3. The method for comprehensively recycling and treating the cathode material of waste lithium iron phosphate manganese batteries according to claim 1, wherein In the step B, before adding lithium leaching solution to the positive electrode powder for leaching, it is necessary to add water to make the solid-liquid ratio of the positive electrode powder to water be 1:5 - 20; When adding lithium leaching solution to the positive electrode powder for leaching, it is necessary to monitor the pH simultaneously. Stop adding lithium leaching solution when the pH reaches 4.0 - 4.

5. The leaching temperature is 50 - 90 °C, the leaching time is 20 - 120 min, and the stirring speed during the leaching process is 250 - 600 r / min; In the process of purification and impurity removal, it is necessary to add alkali solution to adjust the pH = 8 - 10. Ferric ions and manganese ions in the solution form hydroxide precipitates, and then centrifugal separation can be carried out; In the process of concentration and precipitation, it is necessary to first heat and concentrate the solution obtained in the above purification and impurity removal process. During the heating and concentration process, add sodium carbonate solution to the solution to obtain crude lithium carbonate; In the carbonation purification process, crude lithium carbonate is prepared into battery-grade lithium carbonate.

4. The method for comprehensively recycling and treating the cathode material of waste lithium iron phosphate manganese batteries according to claim 1, wherein In the step C, add manganese-iron-phosphorus leaching solution to the filter residue. The filter residue reacts with the manganese-iron-phosphorus leaching solution. Stop adding manganese-iron-phosphorus leaching solution when the pH reaches 0 - 0.

5. The leaching temperature is 75 - 90 °C, the leaching time is 30 - 120 min, and the stirring speed during the leaching process is 250 - 600 r / min; During the process of adding alkali for neutralization precipitation, it is necessary to adjust the pH of the solution to 4.5 - 5.

5.

5. A method for comprehensively recycling and treating the cathode material of waste lithium iron manganese phosphate batteries according to claim 1, characterized in that, In step D, the mass fraction of the phosphoric acid solution added to the crude manganese (II) iron phosphate is 5% - 15%; after the crude manganese (II) iron phosphate is dissolved by phosphoric acid, it is necessary to add a phosphoric acid solution with pH = 2 to dilute it so that the molar concentration of manganese (II) iron phosphate in the solution is 1 - 3 mol / L; The diluted manganese (II) iron phosphate solution is added to the reaction kettle through a peristaltic pump at a rate of 0.2 - 1.2 ml / L, and the addition rate of the alkali solution to the reaction kettle is adjusted after being fed back by a pH meter to maintain the pH of the reaction kettle at 4.5 - 5.5; The inert gas is one of nitrogen, helium, and argon. The temperature of the reaction kettle is controlled by an oil bath to maintain the temperature of the reaction kettle at 45 - 55 °C, the stirring speed in the reaction kettle is 700 - 1000 r / min, and the reaction time is 600 - 1800 min.

6. A method for comprehensively recycling and treating the cathode material of waste lithium iron manganese phosphate batteries according to claim 4 or 5, characterized in that, In steps C and D, the molar concentration of the added alkali solution is 1 - 3 mol / L.

7. A method for comprehensively recycling and treating the cathode material of waste lithium iron phosphate manganese batteries according to claim 6, characterized in that, When the alkali solution is a mixed solution of ammonia water and sodium hydroxide, the molar concentration of ammonia water is greater than that of sodium hydroxide.

8. A method for comprehensively recycling and treating the cathode material of waste lithium iron phosphate manganese batteries according to claim 6, characterized in that When the alkali solution is a mixed solution of ammonia water and potassium hydroxide, the molar concentration of ammonia water is greater than that of potassium hydroxide.

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