A novel integrated method for recycling lithium iron phosphate and ternary materials

Abstract

A novel integrated method for recovering lithium iron phosphate and ternary materials is applied to the field of recycling and reuse of positive electrode materials for lithium-ion batteries. The preparation method comprises the following steps: an acid solution is prepared according to a stoichiometric ratio and placed in a beaker, lithium iron phosphate waste is added thereto, and a constant temperature magnetic stirrer is used to fully stir the solution to perform a leaching reaction. After the reaction is completed, the ternary material is added thereto for further stirring, and a chelating agent is added, and a coprecipitation reaction is performed by controlling the pH value, reaction time, reaction temperature, etc. After centrifugation and drying, the obtained material is subjected to high-temperature calcination to prepare a ternary positive electrode material with a phosphate composite coating layer. The present invention adopts an acid leaching process and a coprecipitation process to uniformly recover the ternary waste material and the lithium iron phosphate waste material, repairs the ternary waste material, and provides it with a composite coating layer such as phosphate, thereby obtaining a recycled material with excellent performance.

Description

Technical Field

[0001] The invention relates to a novel integrated method for recovering lithium iron phosphate and ternary materials, which is applied to the field of recycling and reusing positive electrode materials of lithium ion batteries. Background Art

[0002] Lithium-ion batteries (LIBs) have become an integral part of modern life, covering a wide range of applications from portable electronic devices to electric vehicles. The widespread adoption of LIBs has led to a significant increase in demand for key materials such as lithium, cobalt, and nickel. However, the extraction and processing of these materials are subject to environmental and social issues, including mineral contamination, water depletion, and child labor. As the stockpile of discarded LIBs continues to grow, the need for sustainable and responsible management of discarded batteries becomes increasingly urgent. Recycling LIBs can reduce the environmental impact of primary material extraction, reduce the risk of supply chain disruptions, and preserve natural resources for the future.

[0003] NCM ternary materials are cathode materials for lithium-ion batteries. They are known for their high energy density, long cycle life and relatively low cost. NCM materials have a layered structure, with lithium ions occupying the interlayer space. Nickel, cobalt and manganese elements help stabilize the structure and enhance the electrochemical performance in the material. Lithium iron phosphate (LFP) and lithium iron manganese phosphate (LMFP) with olivine structure have attracted widespread attention in the market due to their high safety, good electrochemical performance and relatively low cost. At present, LFP and LMFP, two cathode materials, are widely used in the market, but waste lithium-ion batteries containing these two materials still contain a large amount of transition metals. On the one hand, they are relatively expensive, and on the other hand, they have a very serious impact on the environment. Therefore, how to better recycle materials has become a top priority in the industry.

[0004] The main methods used by the industry to recycle lithium-ion battery positive electrode materials are as follows: high-temperature melting method, which melts waste battery materials and separates metal elements such as nickel, cobalt, manganese, etc.; mechanochemical method, which uses mechanical force and chemical reactions to crush and separate waste battery materials and extract metal elements; bioleaching method, which uses microorganisms or enzymes to decompose waste battery materials and extract metal elements; electrochemical method, which uses electrochemical methods to decompose waste battery materials and extract metal elements; solvent extraction method, which uses selective solvents to extract and separate metal elements from waste battery materials; direct reduction method, which directly reduces waste battery materials into metal powder or alloy.

[0005] Since the cost of lithium-ion battery recycling technology is still high and it is difficult to compete with primary production, the recycling industry lacks economic benefits; lithium-ion battery recycling technology requires complex processes and equipment, and requires highly skilled operators, which increases the cost and difficulty of recycling; the complexity of lithium-ion battery materials makes recycling and separation difficult, and requires the development and improvement of specialized technologies and equipment. In summary, there is a need to develop a new type of integrated recycling technology to recycle waste lithium-ion battery positive electrode materials. Summary of the invention

[0006] The purpose of the present invention is to solve the problems of difficulty and high cost in recycling lithium-ion batteries, and to provide a novel integrated method for recycling lithium iron phosphate and ternary materials. The preparation method realizes the integrated recycling of waste lithium iron phosphate and ternary materials by controlling the type, molar concentration, solid-liquid ratio and reaction time of the leaching acid in the acid leaching process and the type, pH value, reaction time and reaction temperature of the chelating agent in the coprecipitation process.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A novel integrated method for recovering lithium iron phosphate and ternary materials, the method comprising the following steps:

[0009] Step 1: Acid leaching of lithium iron phosphate waste: a mixed solution of acid and hydrogen peroxide is prepared according to the stoichiometric ratio and placed in a container, lithium iron phosphate waste is added thereto, and stirred fully using a constant temperature magnetic stirrer, and a condensation reflux device is provided; the condensation reflux device is used to cool the evaporated hydrogen peroxide in the condenser, and recirculate the condensed hydrogen peroxide into the system to save the amount of hydrogen peroxide used;

[0010] Step 2: Mixing and co-precipitating the ternary waste material with the lithium iron phosphate waste acid solution: directly adding the ternary waste material into the container of step 1 for stirring, with a solid-liquid mass ratio of 1:20-50, and adding a chelating agent, controlling the pH value, reaction time, and reaction temperature to carry out a co-precipitation reaction;

[0011] Step 3: Collect the ternary waste precursor by centrifugal drying: After the coprecipitation reaction in step 2 is completed, centrifuge it with a centrifuge, the precipitate obtained by centrifugation is the coprecipitation product, and the liquid obtained by centrifugation is the filtrate, so as to obtain the pre-treated ternary waste coprecipitation product and filtrate, wash the coprecipitation product, and dry it in a drying oven at 100°C for 12 hours to obtain the preliminary material;

[0012] Step 4: High-temperature solid-phase method for repairing materials: The preliminary product obtained in step 3 is pre-calcined at 500°C for 5 hours, and then calcined at high temperature for the second time to obtain a ternary recycling material containing a coating layer. The lithium source of the lithium-deficient ternary material comes from waste lithium iron phosphate, and the lithium iron phosphate is recycled into a coating layer on the surface of the ternary material to improve the battery rate, cycle and other performance. The lithium source of the coating layer comes from waste lithium iron phosphate.

[0013] Furthermore, in step 1, the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, oxalic acid, citric acid, and malic acid.

[0014] Furthermore, in step 1, the molar concentration of the acid solution is 0.1-1 mol / L; and the mass ratio of the lithium iron phosphate waste to the acid solution is 1:5-30.

[0015] Furthermore, in step 1, the reaction temperature is maintained at 40-80° C. during the acid leaching; and the reaction time during the acid leaching is 2-12 h.

[0016] Furthermore, in step 2, the chelating agent is a combination of ammonia water and one or more of polyphosphates, aminocarboxylic acids, 1,3-diketones, hydroxycarboxylic acids, polyamines or derivatives of the above chelating agents except ammonia water, and the amount of the chelating agents added except ammonia water is not more than 0.18 mol / L.

[0017] Furthermore, in step 2, the coprecipitation reaction time is 12-40h; and the reaction process temperature is 50-60°C.

[0018] Furthermore, in step 2, the coprecipitation adopts a phosphate / oxalate system, a hydroxide system or a carbonate system to control the pH; the pH value is controlled to be 4-6.5 (phosphate / oxalate system), 7.0-8.5 (carbonate system), 10.5-11.5 (hydroxyl system), and the total ammonia concentration is 0.5-1.5 mol / L.

[0019] Furthermore, in step 3, after the filtrate obtained by centrifugation is filtered and treated, step 1 can be repeated for acid leaching to achieve recycling and save costs. The first step is acid + hydrogen peroxide + water, where the filtrate can act as water during acid leaching.

[0020] Furthermore, in step 4, the temperature of the secondary high-temperature calcination is 700-850°C and the time is 12-18h.

[0021] The beneficial effects of the present invention compared to the prior art are:

[0022] (1) The present invention adopts an integrated recycling method of ternary materials and lithium iron phosphate materials. Compared with the traditional recycling method that requires manpower and material resources to classify materials, it greatly saves the recycling investment cost.

[0023] (2) The present invention adopts a process combining acid leaching and co-precipitation to directly process waste positive electrode materials into new positive electrode materials. Compared with the method of extracting metal elements, it greatly simplifies the recycling process and reduces the recycling cost.

[0024] (3) The waste liquid generated in the process of the present invention can be reused in the acid leaching process after further treatment, thereby realizing the recovery and internal circulation of process products and reducing the process production cost.

[0025] (4) The ternary positive electrode material with a lithium coating layer synthesized by the present invention has low cost and high value of the recycled product. The product performance has obvious advantages over the ternary materials on the market and is suitable for promotion and application in the waste lithium battery recycling industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of a novel integrated method for recovering lithium iron phosphate and ternary materials of the present invention;

[0027] Figure 2 This is a SEM image of the waste lithium iron phosphate to be recycled according to the present invention;

[0028] Figure 3 This is a SEM image of the waste ternary material to be recycled according to the present invention;

[0029] Figure 4 This is a SEM image of the ternary material successfully recovered by the present invention;

[0030] Figure 5 This is a TEM image of the lithium coating layer on the surface of the ternary material successfully recovered by the present invention;

[0031] Figure 6 This is a rate diagram of the successfully recycled ternary material Example 1 of the present invention;

[0032] Figure 7 This is a 2-fold rate diagram of the successfully recycled ternary material embodiment of the present invention;

[0033] Figure 8 This is a rate diagram of Example 3 of the ternary material successfully recovered by the present invention;

[0034] Fig. 9 This is the cycle diagram at 0.33C of the ternary material embodiment 1 successfully recovered by the present invention;

[0035] Fig.10 0.5C cycle diagram of the ternary material embodiment 2 and embodiment 3 which are successfully recycled in the present invention; DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0037] The present invention adopts an acid leaching process and a coprecipitation process, and by regulating various variables, a positive electrode recycling material with complete morphology and taking into account both capacity and circulation is prepared. At the same time, the method can realize the simultaneous recycling of ternary waste materials and lithium iron phosphate waste materials, repairing the ternary waste materials while providing them with a composite coating layer such as phosphate, thereby obtaining a recycling material with excellent performance. The material preparation method of the present invention has the advantages of simple process, simple operation, low cost, etc., and is suitable for large-scale industrial recycling and reuse.

[0038] Example 1

[0039] A novel integrated method for recycling lithium iron phosphate and ternary materials comprises the following steps:

[0040] Step 1: Prepare hydrochloric acid and hydrogen peroxide solution with molar concentrations of 0.5 mol / L and 2 mol / L respectively and place them in a beaker, add lithium iron phosphate waste (such as Figure 2 As shown), the mass ratio of solution to lithium iron phosphate waste is 1:5-30, and a constant temperature magnetic stirrer is used to maintain the reaction temperature at 60°C and stir for 6 hours; nickel, cobalt and manganese elements mainly exist in the form of +2, +3 and +4 valences. The chemical bond between transition metals and oxygen is very strong and not easy to leach. Hydrogen peroxide mainly acts as a reducing agent, breaking the chemical bond between transition metals and oxygen, making metal ions easier to leach.

[0041] Step 2: Ternary waste materials (such as Figure 3 As shown in the figure, the solid-liquid mass ratio is 1:20-50, and the carbonate system is selected. Ammonia water and polyamine are added as chelating agents, the pH value in the system is controlled to be 8-8.5, the total ammonia concentration is controlled to be 0.5-1.0 mol / L, the reaction time is 12-24h, and the reaction temperature is 50°C for coprecipitation reaction;

[0042] Step 3: After the reaction is completed, the precursor slurry is taken out from the reactor, the precursor slurry is washed with deionized water to remove impurities, and the precursor slurry is dried by blasting to remove moisture to obtain a pre-treated product, and then the pre-treated product is ground and mixed evenly and then loaded into a crucible;

[0043] Step 4: The crucible is sent into a tube furnace for sintering, the first calcination temperature is set to 500°C, the sintering time is 5h, and then the temperature is raised to the second calcination temperature of 800°C, the sintering time is 12h, and then sieved (sieve mesh number 300 mesh) to obtain a ternary positive electrode material containing a coating layer (such as Figure 4 As shown), the TEM of the coating layer is Figure 5 shown.

[0044] Example 2

[0045] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials. Except for maintaining the acid type of acid leaching as citric acid or malic acid, the system selects a hydroxide system, controls the pH value to be 10-11.5, and the secondary calcination temperature is 700°C. The rest is the same as Example 1.

[0046] Example 3

[0047] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials. In addition to maintaining the acid type of acid leaching as oxalic acid or phosphoric acid, the system selects an oxalate / phosphate system, controls the pH value to be 4-6.5, and the secondary calcination temperature is 760°C. The rest is the same as Example 1.

[0048] Example 4

[0049] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials, which is the same as that of Embodiment 1 except that the molar concentration of the acid is maintained at 0.5 mol / L.

[0050] Example 5

[0051] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials. Except for maintaining the molar concentration of the acid at 1 mol / L, the rest is the same as that of Example 1.

[0052] Example 6

[0053] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials, which is the same as that of Embodiment 1 except that the solid-liquid ratio is changed to 1:30.

[0054] Example 7

[0055] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials, which is the same as that of Embodiment 1 except that the acid leaching temperature is 80°C.

[0056] Example 8

[0057] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials, which is the same as that of Example 1 except that the acid leaching reaction time is 12 hours.

[0058] Example 9

[0059] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials, which is the same as that of Embodiment 1 except that the co-precipitated chelating agent is aminocarboxylic acid.

[0060] Example 10

[0061] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials, which is the same as that of Example 1 except that the coprecipitation reaction time is 18 hours.

[0062] Embodiment 11

[0063] This embodiment provides a novel integrated method for recovering lithium iron phosphate and ternary materials, which is the same as that of Embodiment 1 except that the coprecipitation reaction temperature is 60°C.

[0064] The LAND test system was used for testing. At 25°C, all prepared samples were subjected to 3-4.3V charge and discharge tests. Example 1 was tested at 0.1C, 0.2C, 0.33C and 0.5C charge and discharge rates (such as Figure 6 As shown, at 0.1C, 0.2C, 0.33C and 0.5C, the capacities are 204.46mAh / g, 191.31mAh / g, 187.05mAh / g and 180.41mAh / g, respectively. At 0.1C, 0.2C, 0.33C and 0.5C, the capacities of Example 2 are 199.20mAh / g, 182.68mAh / g, 178.27mAh / g and 171.87mAh / g, respectively. At 0.1C, 0.2C, 0.33C and 0.5C, the capacities of Example 3 are 195.18mAh / g, 177.19mAh / g, 167.40mAh / g and 159.5mAh / g. The cycle retention rate of Example 1 after 50 cycles at 3-4.3V and 0.33C is 97.94%, the cycle retention rate of Example 2 after 50 cycles at 3-4.3V and 0.5C is 86.70%, and the cycle retention rate of Example 3 after 50 cycles at 3-4.3V and 0.5C is 94.10%.

[0065] In summary, the present invention repairs the structure of waste materials through a novel integrated method for recycling lithium iron phosphate and ternary materials, and the positive electrode material prepared by this method has good electrochemical properties.

Claims

1. A novel integrated method for recovering lithium iron phosphate and ternary materials, characterized in that: The method comprises the following steps: Step 1: Acid leaching of lithium iron phosphate waste: a mixed solution of acid and hydrogen peroxide is prepared according to the stoichiometric ratio and placed in a container, lithium iron phosphate waste is added thereto, and stirred fully using a constant temperature magnetic stirrer, and a condensation reflux device is used; Step 2: Mixing and co-precipitating the ternary waste material with the lithium iron phosphate waste acid solution: directly adding the ternary waste material to the container of step 1 for stirring, with a solid-liquid mass ratio of 1:20-50, and adding a chelating agent, controlling the pH value, reaction time, and reaction temperature to carry out a co-precipitation reaction; the co-precipitation adopts a phosphate / oxalate system, a hydroxide system, or a carbonate system to control the pH; the pH value of the phosphate / oxalate system is controlled to be 4-6.5, the pH value of the carbonate system is controlled to be 7.0-8.5, the pH value of the hydroxide system is controlled to be 10.5-11.5, and the total ammonia concentration is 0.5-1.5 mol / L; Step 3: Collect the ternary waste precursor by centrifugal drying: After the coprecipitation reaction in step 2 is completed, centrifuge it with a centrifuge, the precipitate obtained by centrifugation is the coprecipitation product, and the liquid obtained by centrifugation is the filtrate, so as to obtain the pre-treated ternary waste coprecipitation product and filtrate, wash the coprecipitation product, and dry it in a drying oven at 100°C for 12 hours to obtain the preliminary material; Step 4: High-temperature solid-phase repair material: The preliminary product obtained in the above step 3 is pre-calcined at 500°C for 5h, and then calcined at high temperature for a second time to obtain a ternary recovery material containing a coating layer.

2. A novel integrated method for recovering lithium iron phosphate and ternary materials according to claim 1, characterized in that: In step 1, the acid is one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, oxalic acid, citric acid, and malic acid.

3. A novel integrated method for recovering lithium iron phosphate and ternary materials according to claim 1, characterized in that: In step 1, in the mixed solution of the acid and hydrogen peroxide, the molar concentration of the acid is 0.1-1 mol / L; and the mass ratio of the lithium iron phosphate waste to the mixed solution is 1:5-30.

4. A novel integrated method for recovering lithium iron phosphate and ternary materials according to claim 1, characterized in that: In step 1, the reaction temperature is maintained at 40-80° C. during the acid leaching; and the reaction time during the acid leaching is 2-12 h.

5. A novel integrated method for recovering lithium iron phosphate and ternary materials according to claim 1, characterized in that: In step 2, the chelating agent is a combination of ammonia and one or more of polyphosphate, aminocarboxylic acid, 1,3-diketone, hydroxycarboxylic acid, polyamine or derivatives of the above chelating agents except ammonia.

6. A novel integrated method for recovering lithium iron phosphate and ternary materials according to claim 1, characterized in that: In step 2, the reaction time of the coprecipitation is 12-40h; and the reaction temperature is 50-60°C.

7. A novel integrated method for recovering lithium iron phosphate and ternary materials according to claim 1, characterized in that: In step 3, after filtering the filtrate obtained by centrifugation, step 1 can be repeated for acid leaching.

8. A novel integrated method for recovering lithium iron phosphate and ternary materials according to claim 1, characterized in that: In step 4, the temperature of the secondary high-temperature calcination is 700-850°C and the time is 12-18 hours.

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