A method and apparatus for recovering LFP-LMO cathode materials via coupled electrodialysis

Abstract

This invention belongs to the field of battery recycling, specifically disclosing a coupled electrodialysis recycling method for LFP-LMO cathode materials. The method involves coupled electrodialysis treatment of LFP and LMO cathode materials in an electrodialysis apparatus. The electrodialysis apparatus includes an electrolytic cell and a monovalent permeable cation exchange membrane dividing the electrolytic cell chamber into a cathode chamber and an anode chamber. The cathode chamber contains a cathode, and the anode chamber contains an anode. LFP cathode material and sulfate electrolyte are added to the anode chamber, while LMO and oxalate source electrolyte are added to the cathode chamber. The cathode and anode are electrically connected to the negative and positive terminals of a power source, respectively, for coupled electrodialysis. During the coupled electrodialysis, the pH in the anode chamber is controlled at 1.5–3, and the voltage range is 1–3V. After the coupled electrodialysis is completed, a lithium-rich solution is separated from the solution in the cathode chamber, and M-metal oxalate is separated from the cathode chamber. Iron phosphate is separated from the anode chamber. This invention achieves efficient coupled treatment of LFP and LMO.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery recycling technology, and in particular relates to a method for selectively recycling cathode materials of waste power lithium batteries. Background Technology

[0002] Lithium-ion batteries, as one of the most popular energy storage materials today, occupy an important position in China's new energy field and have a wide range of applications. However, due to the limited lifespan of lithium batteries, averaging 5-7 years, the recycling problem of used lithium batteries will become increasingly prominent as the lithium-ion battery market experiences explosive growth. It is estimated that by 2023, the annual amount of used lithium batteries will reach 101 GWh, approximately 1.16 million tons per year.

[0003] In terms of the value proportion of major components, cathode materials account for about 30% of waste lithium batteries, containing a large amount of valuable metals such as nickel, cobalt, manganese, and lithium. Lithium, in particular, is considered a strategic resource, partly due to my country's small lithium reserves and partly due to the high technical difficulty of extracting lithium from lithium deposits, which restricts the development of lithium metal in my country. Currently, the price of lithium carbonate has rapidly increased to around 500,000 yuan / ton. Conventional lithium extraction methods often extract lithium metal at the later stages, leading to lithium metal loss in the lengthy purification process at the front end, reducing the recovery rate of lithium carbonate products, and potentially introducing impurities into the product. Furthermore, current recycling processes are all designed for single cathode materials. This is because different crystal structures of cathode materials require different oxidation / reduction systems. If valuable metals from two different types of cathode materials could be recovered simultaneously within a single system, it would greatly promote the development of resource recycling in my country.

[0004] For waste cathode materials, the main processes in the industry are acid leaching and alkaline leaching. The selectivity, efficiency and effect of existing processes in separating lithium and other active metals are not ideal. Summary of the Invention

[0005] To address the shortcomings of traditional processes, this invention provides a method for the coupled electrodialysis recovery of LFP-LMO cathode materials, aiming to achieve coupled and synergistic processing of LFP-LMO and improve the efficiency and effectiveness of the combined processing.

[0006] A second objective of the present invention is to provide a coupled electrodialysis apparatus for implementing the method.

[0007] This invention is the first to propose the idea of ​​coupling LFP-LMO cathode materials with electrodialysis. However, early research revealed that inappropriate coupling electrodialysis methods would limit lithium recovery. Furthermore, it was difficult to simultaneously obtain iron phosphate and Li-M phase byproducts, resulting in unsatisfactory separation efficiency and selectivity for Li-Fe and Li-M. To address this problem, this invention, through in-depth research, provides the following improved solutions:

[0008] A method for recovering LFP-LMO cathode materials by coupled electrodialysis involves treating LFP and LMO cathode materials by coupled electrodialysis in an electrodialysis device.

[0009] The electrodialysis device includes an electrolytic cell and a monovalent permeable cation exchange membrane that divides the electrolytic cell chamber into a cathode chamber and an anode chamber; the cathode chamber is provided with a cathode, and the anode chamber is provided with an anode;

[0010] LFP cathode material and sulfate electrolyte are added to the anode chamber, and LMO and oxalate source electrolyte are added to the cathode chamber. The cathode and anode are then electrically connected to the negative and positive terminals of the same power source, respectively, for coupled electrodialysis.

[0011] The LFP cathode material is a waste lithium iron phosphate cathode material, and the LMO cathode material is a waste lithium-containing M metal oxide, wherein M is at least one of nickel, cobalt, and manganese.

[0012] During coupled electrodialysis, the pH in the anode chamber is controlled at 1.5–3; the voltage range is 1–3V.

[0013] After coupled electrodialysis is completed, a lithium-rich solution is separated from the solution in the cathode chamber, and M metal oxalate is separated from the cathode chamber; iron phosphate is separated from the anode chamber.

[0014] This invention innovatively proposes a coupled electrodialysis process where LFP is placed in the anode chamber and LMO in the cathode chamber. Furthermore, it combines this with the joint control of process parameters such as electrolyte solution and voltage in both the cathode and anode chambers. This achieves synergistic effects, improving lithium extraction efficiency and the separation selectivity of Li-Fe and Li-M. Moreover, it can simultaneously obtain high-purity iron phosphate and M oxalate phases as byproducts, enabling efficient and simultaneous processing of LFP and LMO.

[0015] In this invention, the coupled electrodialysis method of placing LFP in the anode chamber and LMO in the cathode chamber, as well as the joint control of parameters such as electrolyte in the anode and cathode chambers and voltage and electrode spacing during the processing, are key to synergistically improving the coupled processing effect, improving lithium extraction rate and extraction efficiency, and simultaneously obtaining iron phosphate and M oxalate byproducts.

[0016] In this invention, the LMO cathode material can be any lithium-containing oxide of at least one element in nickel, cobalt, or manganese, for example, it can be waste LiCoO2 or waste LiNi. x Co y Mn z At least one of O2.

[0017] In this invention, the cathode and LFP materials can participate in the electrodialysis treatment in a composite or non-composite form. Similarly, the anode and LMO materials can also participate in the electrodialysis treatment in a composite or non-composite form.

[0018] The non-composite form, as the name suggests, refers to a form where the electrode material and the electrode sheet are not pre-composite. A specific implementation method includes, for example, using a conventional conductive electrode as the anode or cathode, peeling off the corresponding LFP or LMO cathode material from a waste cathode sheet, and placing the peeled cathode material in a corresponding electrode chamber for coupling treatment. The anode or cathode in this embodiment can be a conventional conductive electrode used in the industry, such as a graphite electrode, a metal electrode such as stainless steel, or a lead-silver alloy electrode.

[0019] In another embodiment of the present invention, the LFP cathode material is composited on the surface of the anode, and the LMO cathode material is composited on the surface of the cathode. For example, the LFP cathode stripped from waste lithium iron phosphate batteries can be directly used as the anode, and the LMO cathode stripped from waste LMO batteries can be directly used as the cathode. In this invention, using waste LFP and waste LMO cathodes as the anode and cathode for coupled electrodialysis simplifies the processing procedure and also helps improve the treatment effect.

[0020] In this invention, in order to further improve processing efficiency, multiple LFP waste positive electrodes or multiple LMO waste positive electrodes can be electrically connected to each other and then processed together.

[0021] In this invention, the electrolytic cell can be a single-chamber electrolytic cell, in which a monovalent permeable cation exchange membrane is placed in the middle of the cell to separate the electrolyte in the left and right cathode and anode chambers. Alternatively, the electrolytic cell of this invention can also be a dual-chamber electrolytic cell connected in series by pipelines, wherein the monovalent permeable cation exchange membrane is placed in the series pipeline section to separate the electrolyte between the cells.

[0022] In this invention, the use of a monovalent permeable cation exchange membrane to divide the chambers of the electrolyzer can be understood as the monovalent permeable cation exchange membrane having an anode chamber electrolyte on one side and a cathode chamber electrolyte on the other side.

[0023] In this invention, the monovalent permeable cation exchange membrane is at least one of polyvinyl alcohol-based composite membrane and sulfonated polyether ether ketone nanofibers;

[0024] In this invention, the innovative synergistic coupling electrodialysis of the LFP and LMO special electrode chambers, combined with the joint control of the electrolyte in the cathode and anode chambers and the processing conditions of the coupled electrodialysis, can synergistically improve the lithium extraction effect. Moreover, it can also facilitate the simultaneous acquisition of M oxalate by-product in the cathode chamber and ferric phosphate phase by-product in the anode chamber.

[0025] In this invention, the sulfate electrolyte in the anode chamber is an aqueous solution of sodium sulfate and potassium sulfate, and the concentration of the sulfate is preferably 1-3M.

[0026] Preferably, in the oxalic acid source electrolyte of the cathode chamber, the oxalic acid source is at least one of oxalic acid and water-soluble salts of oxalic acid.

[0027] Preferably, the concentration of the oxalic acid source is 1–10 M.

[0028] Preferably, the oxalic acid source electrolyte is a mixture of 2-4M oxalic acid and 2-4M ammonium oxalate.

[0029] Preferably, the electrode spacing is 5–20 cm during coupled electrodialysis.

[0030] Preferably, the temperature during the coupled electrodialysis process is 30–50°C; the preferred time is 5–8 hours.

[0031] In this invention, lithium and M oxalate can be separated from the cathode chamber and iron phosphate can be separated from the anode chamber using existing methods.

[0032] Preferably, after coupled electrodialysis, the solution in the cathode chamber is collected, and then a lithium precipitation agent is added for lithium precipitation treatment to obtain lithium precipitate;

[0033] Preferably, the solution is purified with sodium oxalate before lithium precipitation.

[0034] Preferably, the purification temperature is 40–60°C; the purification time is preferably 1–3 hours.

[0035] Preferably, the lithium precipitation agent is at least one of sodium carbonate and sodium phosphate;

[0036] Preferably, the excess coefficient of the lithium precipitation agent is 1.05 to 1.5;

[0037] Preferably, the temperature for the lithium precipitation reaction is 60–90°C;

[0038] Preferably, the lithium precipitation reaction time is 1 to 5 hours.

[0039] The present invention also provides an electrodialysis apparatus for implementing the method.

[0040] Preferably, the electrodialysis device includes an electrolytic cell and a monovalent permeable cation exchange membrane that divides the electrolytic cell chamber into an anode chamber and a cathode chamber. The anode chamber is provided with a waste LFP positive electrode, and the cathode chamber is provided with a waste LMO positive electrode. The LFP positive electrode and the waste LMO positive electrode are electrically connected to the positive and negative terminals of the same power source, respectively.

[0041] In this invention, during the coupled electrodialysis process using an electrodialysis device, sulfate electrolyte is added to the anode chamber and oxalic acid source electrolyte is added to the cathode chamber. The electrolytes soak the respective electrodes, and then the power is turned on to perform coupled electrodialysis.

[0042] Preferably, the electrolytic cell is a dual-chamber electrolytic cell connected by a series pipeline, and the monovalent permeable cation exchange membrane is installed at the connection pipeline to separate the electrolyte in the cathode chamber and the anode chamber.

[0043] Beneficial effects

[0044] This invention innovatively proposes a coupled electrodialysis process where LFP is placed in the anode chamber and LMO in the cathode chamber. Furthermore, it combines this with the joint control of process parameters such as electrolyte solution, electrode spacing, and voltage in both the cathode and anode chambers. This achieves synergistic effects, improving lithium extraction efficiency. Moreover, it simultaneously yields iron phosphate and M oxalate phases as byproducts, enabling efficient and simultaneous processing of LFP and LMO. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the coupled electrodialysis device of the present invention;

[0046] Figure 2 This is a flowchart of the technical solution of the present invention; Detailed Implementation

[0047] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0048] The coupled electrodialysis device of this invention is shown below. Figure 1The system includes an electrolytic cell 1, with a valence-permeable cation exchange membrane (located in series) dividing the chamber of the electrolytic cell 1 into an anode chamber 2 and a cathode chamber 3. A lithium iron phosphate positive electrode dismantled from a spent lithium iron phosphate battery is used as the anode and connected to the positive terminal of the power supply, and is immersed in the electrolyte in the anode chamber. A positive electrode sheet dismantled from a spent LMO battery is used as the cathode and connected to the negative terminal of the power supply, and is immersed in the electrolyte in the cathode chamber. The electrolyte in the anode chamber is a sulfate solution, and the electrolyte in the cathode chamber is a mixed solution of oxalate and ammonium oxalate.

[0049] Monovalent permeation cation exchange membranes can be made of membranes that allow monovalent ions to permeate, which are common in the industry. For example, in the following case, a monovalent permeation polyvinyl alcohol-based composite membrane is used.

[0050] Example 1:

[0051] ① Pretreatment: The waste power lithium battery was placed in 2mol / L salt water for 12h discharge treatment. The discharged battery was dried at 80℃ and then disassembled to separate 2cm×4cm LiCoO2 positive electrode sheet and LiFePO4 positive electrode sheet.

[0052] ② Coupled Electrodialysis: The LiCoO2 positive electrode is immersed in the cathode electrolyte, and the LiFePO4 positive electrode is immersed in the anode electrolyte. A monovalent permeable cation exchange membrane is used in between. The anode electrolyte is a 2 mol / L Na2SO4 solution, and the cathode electrolyte is a mixed solution of 2 mol / L H2C2O4 and 2 mol / L NH4C2O4. Electrolysis is started by connecting the power supply, with the voltage controlled at 3V, the electrode spacing at 15cm, the electrolysis temperature at 40℃, and the electrolysis time at 8h.

[0053] ③ Lithium precipitation: The solution in the cathode chamber is filtered to obtain a lithium-containing solution. First, it is purified using a 35 g / L Na₂C₂O₄ solution to remove residual transition metal ions at 60℃ for 2 hours. After purification, Na₂CO₃ is used as a precipitant to precipitate lithium, with an excess precipitant coefficient of 1.2, a reaction temperature of 90℃, and a reaction time of 1 hour. Finally, the solution is filtered and washed several times while hot to obtain the Li₂CO₃ product.

[0054] ④ Separation and recovery of transition metals: The filter residue in the cathode chamber after filtration, i.e., cathode mud, is a CoC2O4 product, while the pH of the solution in the anode chamber is adjusted to 2 during electrodialysis, and the anode mud obtained after electrodialysis treatment is a FePO4 product.

[0055] The recovery rates for lithium, cobalt, and iron in the entire process were 98.5%, 97.5%, and 99.2%, respectively. The purity of the obtained Li₂CO₃ product was 99.0%, the purity of the CoC₂O₄ product was 98.7%, and the purity of the FePO₄ product was 97.4%.

[0056] Example 2:

[0057] ① Pretreatment: The spent power lithium batteries were placed in 3mol / L salt water for 10 hours for discharge treatment. After discharge, the batteries were dried at 80℃, and 2.5cm×3.5cm LiNi were separated from them. x Co y Mn z O2 cathode and LiFePO4 cathode;

[0058] ② Coupled electrodialysis: The above LiNi x Co y Mn z An O2 cathode is immersed in the cathode electrolyte, and a LiFePO4 cathode is immersed in the anode electrolyte. A monovalent permeable cation exchange membrane is used in between. The anode electrolyte is a 3 mol / L Na2SO4 solution, and the cathode electrolyte is a mixed solution of 3 mol / L H2C2O4 and 3 mol / L NH4C2O4. Electrolysis is started with the power supply connected, the voltage controlled at 2.5V, the electrode spacing at 10 cm, the electrolysis temperature at 50℃, and the electrolysis time at 8 h.

[0059] ③ Lithium precipitation: The solution in the cathode chamber is filtered to obtain a lithium-containing solution. First, it is purified using a 40 g / L Na₂C₂O₄ solution to remove residual transition metal ions at 40°C for 3 hours. After purification, Na₃PO₄ is used as a precipitant to precipitate lithium, with an excess precipitant coefficient of 1.1, a reaction temperature of 90°C, and a reaction time of 1 hour. Finally, the solution is filtered and washed several times while hot to obtain the Li₃PO₄ product.

[0060] ④ Separation and recovery of transition metals: The filter residue in the cathode chamber obtained after filtration, i.e., cathode mud, is a (Ni-Co-Mn)C2O4 precursor. During the electrodialysis process, the pH of the solution in the anode chamber is adjusted to 2.5, and the anode mud obtained after electrodialysis treatment is FePO4 product.

[0061] Throughout the entire process, the recovery rates were 97.7% for lithium, 98.2% for nickel, 97.9% for cobalt, 98.5% for manganese, and 98.8% for iron. The purity of the obtained Li3PO4 product was 98.5%, the purity of the (Ni-Co-Mn)C2O4 precursor was 97.9%, and the purity of the FePO4 product was 96.9%.

[0062] Example 3:

[0063] ① Pretreatment: The waste power lithium battery was placed in 4mol / L salt water for 10h discharge treatment. The discharged battery was dried at 80℃ and then disassembled to separate 1cm×3cm LiCoO2 positive electrode sheet and LiFePO4 positive electrode sheet.

[0064] ② Coupled electrodialysis: The LiCoO2 positive electrode is immersed in the cathode electrolyte and the LiFePO4 positive electrode is immersed in the anode electrolyte. A monovalent permeable cation exchange membrane is used in between. The anode electrolyte is a 1.5 mol / L Na2SO4 solution, and the cathode electrolyte is a mixed solution of 2.5 mol / L H2C2O4 and 2.5 mol / L NH4C2O4. Electrolysis is started by connecting the power supply, with the voltage controlled at 2.8V, the electrode spacing at 8 cm, the electrolysis temperature at 40℃, and the electrolysis time at 6 h.

[0065] ③ Lithium precipitation: The solution in the cathode chamber is filtered to obtain a lithium-containing solution. First, it is purified using a 45 g / L Na₂C₂O₄ solution to remove residual transition metal ions at 60°C for 2 hours. After purification, Na₃PO₄ is used as a precipitant to precipitate lithium, with an excess precipitant coefficient of 1.05 at 80°C for 2 hours. Finally, the solution is filtered and washed several times while hot to obtain the Li₃PO₄ product.

[0066] ④ Separation and recovery of transition metals: The filter residue in the cathode chamber after filtration, i.e., cathode mud, is a CoC2O4 product, while the pH of the solution in the anode chamber is adjusted to 2 during electrodialysis, and the anode mud obtained after electrodialysis treatment is a FePO4 product.

[0067] The recovery rates for lithium, cobalt, and iron in the entire process were 97.8%, 96.9%, and 98.8%, respectively. The purity of the obtained Li3PO4 product was 98.6%, the purity of the CoC2O4 product was 97.3%, and the purity of the FePO4 product was 96.2%.

[0068] Example 4:

[0069] ① Pretreatment: The spent power lithium batteries were placed in 3mol / L brine for 10 hours for discharge treatment. The discharged batteries were then dried at 80℃, and 2cm×3cm LiNi were separated from them. x Co y Mn z O2 cathode and LiFePO4 cathode;

[0070] ② Coupled electrodialysis: The above LiNi x Co y Mn zAn O2 cathode is immersed in the cathode electrolyte, and a LiFePO4 cathode is immersed in the anode electrolyte. A monovalent permeable cation exchange membrane is used in between. The anode electrolyte is a 2 mol / L Na2SO4 solution, and the cathode electrolyte is a mixed solution of 3.5 mol / L H2C2O4 and 3.5 mol / L NH4C2O4. Electrolysis is started by connecting the power supply, with the voltage controlled at 3.0V, the electrode spacing at 12 cm, the electrolysis temperature at 35℃, and the electrolysis time at 7 h.

[0071] ③ Lithium precipitation: The solution in the cathode chamber is filtered to obtain a lithium-containing solution. First, it is purified using a 45 g / L Na₂C₂O₄ solution to remove residual transition metal ions at 60℃ for 2 hours. After purification, Na₂CO₃ is used as a precipitant to precipitate lithium, with an excess precipitant coefficient of 1.25, a reaction temperature of 85℃, and a reaction time of 3 hours. Finally, the solution is filtered and washed several times while hot to obtain the Li₂CO₃ product.

[0072] ④ Separation and recovery of transition metals: The filter residue in the cathode chamber obtained after filtration, i.e., cathode mud, is a (Ni-Co-Mn)C2O4 precursor, while the anode mud obtained by adjusting the pH of the solution in the anode chamber to 3 during electrodialysis is a FePO4 product.

[0073] Throughout the entire process, the recovery rates were 98.3% for lithium, 98.6% for nickel, 97.3% for cobalt, 98.9% for manganese, and 98.1% for iron. The purity of the obtained Li₂CO₃ product was 99.0%, the purity of the (Ni-Co-Mn)C₂O₄ precursor was 98.3%, and the purity of the FePO₄ product was 97.0%.

[0074] Example 5:

[0075] ① Pretreatment: The waste power lithium battery was placed in 3.5mol / L salt water for 12h discharge treatment. The discharged battery was dried at 80℃ and then disassembled to separate 1.5cm×3.5cm LiCoO2 positive electrode sheet and LiFePO4 positive electrode sheet.

[0076] ② Coupled Electrodialysis: The LiCoO2 positive electrode is immersed in the cathode electrolyte and the LiFePO4 positive electrode is immersed in the anode electrolyte. A monovalent permeable cation exchange membrane is used in between. The anode electrolyte is a 3 mol / L Na2SO4 solution, and the cathode electrolyte is a mixed solution of 3.5 mol / L H2C2O4 and 3.5 mol / L NH4C2O4. Electrolysis is started by connecting the power supply, with the voltage controlled at 2.6V, the electrode spacing at 5 cm, the electrolysis temperature at 50℃, and the electrolysis time at 6 h.

[0077] ③ Lithium precipitation: The solution in the cathode chamber is filtered to obtain a lithium-containing solution. First, it is purified with a 50 g / L Na₂C₂O₄ solution to remove residual transition metal ions at 60°C for 1.5 hours. After purification, Na₃PO₄ is used as a precipitant to precipitate lithium, with an excess precipitant coefficient of 1.3, a reaction temperature of 85°C, and a reaction time of 1 hour. Finally, the solution is filtered and washed several times while hot to obtain the Li₃PO₄ product.

[0078] ④ Separation and recovery of transition metals: The filter residue in the cathode chamber after filtration, i.e., cathode mud, is a CoC2O4 product, while the anode mud obtained by adjusting the pH of the solution in the anode chamber to 2.5 during electrodialysis is a FePO4 product.

[0079] The recovery rates for lithium, cobalt, and iron in the entire process were 98.5%, 97.6%, and 98.0%, respectively. The purity of the obtained Li3PO4 product was 97.7%, the purity of the CoC2O4 product was 97.6%, and the purity of the FePO4 product was 97.3%.

[0080] Example 6:

[0081] ① Pretreatment: The spent power lithium batteries were placed in 3mol / L brine for 12 hours for discharge treatment. After discharge, the batteries were dried at 80℃, and 2.5cm×4cm LiNi were separated from them. x Co y Mn z O2 cathode and LiFePO4 cathode;

[0082] ② Coupled electrodialysis: The above LiNi x Co y Mn z An O2 cathode is immersed in the cathode electrolyte, and a LiFePO4 cathode is immersed in the anode electrolyte. A monovalent permeable cation exchange membrane is used in between. The anode electrolyte is a 3 mol / L Na2SO4 solution, and the cathode electrolyte is a mixed solution of 4 mol / L H2C2O4 and 4 mol / L NH4C2O4. Electrolysis is started by connecting the power supply, with the voltage controlled at 3.0V, the electrode spacing at 20 cm, the electrolysis temperature at 50℃, and the electrolysis time at 8 h.

[0083] ③ Lithium precipitation: The solution in the cathode chamber is filtered to obtain a lithium-containing solution. First, it is purified with a 50 g / L Na₂C₂O₄ solution to remove residual transition metal ions at 40℃ for 2 hours. After purification, Na₂CO₃ is used as a precipitant to precipitate lithium, with an excess precipitant coefficient of 1.35, a reaction temperature of 90℃, and a reaction time of 3 hours. Finally, the solution is filtered and washed several times while hot to obtain the Li₂CO₃ product.

[0084] ④ Separation and recovery of transition metals: The filter residue in the cathode chamber obtained after filtration, i.e., cathode mud, is a (Ni-Co-Mn)C2O4 precursor, while the anode mud obtained by adjusting the pH of the solution in the anode chamber to 2 during electrodialysis is a FePO4 product.

[0085] Throughout the entire process, the recovery rates were 98.7% for lithium, 98.8% for nickel, 97.6% for cobalt, 99.1% for manganese, and 98.4% for iron. The purity of the obtained Li₂CO₃ product was 99.3%, the purity of the (Ni-Co-Mn)C₂O₄ precursor was 98.7%, and the purity of the FePO₄ product was 97.5%.

[0086] Comparative Example 1:

[0087] All other conditions and steps were the same as in Example 1, except that: the LiCoO2 cathode was immersed in the electrolyte in the anode chamber as the anode, and the LiFePO4 cathode was immersed in the electrolyte in the cathode chamber as the cathode, resulting in a Li recovery rate of only 11.2%.

[0088] Comparative Example 2: No coupling processing performed:

[0089] Compared to Example 1, the only difference is that no coupling treatment was performed, and the experimental groups are as follows:

[0090] Group A: The anode in the anode chamber is a graphite electrode, and other operations and parameters are the same as in Example 1;

[0091] Group B: The cathode in the cathode chamber is a stainless steel electrode, and other operations and parameters are the same as in Example 1.

[0092] The test results are as follows:

[0093] Group A: The cobalt recovery rate was only 87.3%, and the cathode powder was not completely dissolved.

[0094] Group B: The Li recovery rate was only 83.2%, and no FePO4 product was obtained from the anode mud.

[0095] Comparative Example 3:

[0096] All other conditions and steps were the same as in Example 1, except that a divalent permeable cation exchange membrane was used between the anode and cathode, resulting in a CoC2O4 product with a purity of only 80.1%.

[0097] Comparative Example 4:

[0098] Compared to Example 1, the only difference is that the electrolyte in the electrode chamber is changed, and the experimental groups are as follows:

[0099] Group A: The electrolyte in the anode chamber is 1M NaOH, and other operations and parameters are the same as in Example 1;

[0100] Group B: The cathode electrolyte is Na2SO4, and other operations and parameters are the same as in Example 1;

[0101] The test results are as follows:

[0102] Group A: No FePO4 product was obtained; the anode mud was a mixture of Fe3O4 and Fe2O3; P was not effectively recovered.

[0103] Group B: No CoC2O4 product was found in the cathode chamber, and the total lithium recovery rate was 97.6%, which was lower than that in Example 1. In addition, the purity of the obtained Li2CO3 product was 93.2%, which was lower than that in Example 1.

[0104] Comparative Example 5:

[0105] All other conditions and steps were the same as in Example 1, except that during the electrodialysis treatment stage, the pH of the solution in the anode chamber was adjusted to 0.5, and no FePO4 product was found to be produced.

[0106] Comparative Example 6

[0107] All other conditions and steps were the same as in Example 1, except that the voltage was controlled at 0.6V, and the results showed that the lithium recovery rate was only 38.1% and the cobalt recovery rate was only 27.2%.

Claims

1. A LFP-LMO positive electrode material coupled electrodialysis recovery method, characterized in that, The LFP positive electrode material and the LMO positive electrode material are subjected to coupling electrodialysis treatment in an electrodialysis device; The electrodialysis device comprises an electrolytic cell and a monovalent permeable cation exchange membrane separating the electrolytic cell chamber into a cathode chamber and an anode chamber; the cathode chamber is provided with a cathode, and the anode chamber is provided with an anode; LFP positive electrode material and sulfate electrolyte are added to the anode chamber, and LMO and oxalic acid source electrolyte are added to the cathode chamber; the cathode and the anode are respectively conductively connected to the negative electrode and the positive electrode of a power supply to perform coupling electrodialysis; The LFP positive electrode material is waste lithium iron phosphate positive electrode material, and the LMO positive electrode material is waste lithium-containing M metal oxide, wherein M is at least one of nickel, cobalt and manganese; During the coupling electrodialysis process, the pH in the anode chamber is controlled to be 1.5-3, and the voltage interval is 1-3V; After the coupling electrodialysis is completed, a lithium-rich solution is separated from the solution in the cathode chamber, and M metal oxalate is separated from the cathode chamber; and iron phosphate is separated from the anode chamber.

2. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 1, wherein, The LMO positive electrode material is at least one of waste LiCoO2, waste LiNi x Co y Mn z O 2 ​ 3. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 1, wherein, The monovalent permeable cation exchange membrane is at least one of a polyvinyl alcohol-based composite membrane and sulfonated polyether ether ketone nanofiber.

4. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 1, wherein, In the anode chamber, the LFP positive electrode material is compounded on the surface of the anode, and the LMO positive electrode material is compounded on the surface of the cathode.

5. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 1, wherein, The LFP positive electrode directly stripped from the waste lithium iron phosphate battery is used as the anode, and the LMO positive electrode directly stripped from the waste LMO battery is used as the cathode.

6. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 1, wherein, In the anode chamber, the sulfate electrolyte is an aqueous solution of sodium sulfate and potassium sulfate, and the concentration of the sulfate is 1-3M.

7. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 1, wherein, In the oxalic acid source electrolyte of the cathode chamber, the oxalic acid source is at least one of oxalic acid and a water-soluble salt of oxalic acid.

8. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 7, wherein, The concentration of the oxalic acid source is 1-10M.

9. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 8, wherein, The oxalic acid source electrolyte is a mixture of 2-4M oxalic acid and 2-4M ammonium oxalate.

10. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 1, wherein, During the coupling electrodialysis process, the distance between the electrode plates is 5-20cm; The temperature is 30-50℃, and the time is 5-8h.

11. The LFP-LMO cathode material coupled electrodialysis recovery method according to any one of claims 1-10, characterized in that, After the coupling electrodialysis, the solution in the cathode chamber is collected, and then a lithium precipitation agent is added for lithium precipitation treatment to obtain lithium precipitate.

12. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 11, wherein, Before the lithium precipitation treatment, the solution is purified by sodium oxalate in advance.

13. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 12, wherein, The purification temperature is 40-60℃, and the purification time is 1-3h.

14. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 11, wherein, The lithium precipitation agent is at least one of sodium carbonate and sodium phosphate.

15. The LFP-LMO cathode material coupled electrodialysis recovery method of claim 14, wherein, The excess coefficient of the lithium precipitation agent is 1.05-1.5; The temperature of the lithium precipitation reaction is 60-90℃; The time of the lithium precipitation reaction is 1-5h.

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