Method for recovering spent lithium iron phosphate battery by using electrochemical cathode and anode coupling wet process

Abstract

A method for recovering a spent lithium iron phosphate battery by using an electrochemical cathode and anode coupling wet process, which method belongs to the technical field of resource recovery of lithium batteries. The method comprises the following steps: S1, pre-treating a spent lithium iron phosphate battery to obtain a lithium iron phosphate waste material; S2, electrolysing an electrolyte by using an electrochemical system comprising a working electrode, a counter electrode and a reference electrode, with the lithium iron phosphate waste material being oxidiz and decomposed to obtain a mixed solution containing iron phosphate and Li+, wherein the electrolyte comprises an acid solution, and further comprises the lithium iron phosphate waste material; S3, filtering the mixed solution containing iron phosphate and Li+ to obtain iron phosphate and a filtrate containing Li+; and S4, introducing carbon dioxide into the filtrate containing Li+ of S3 to perform a lithium precipitation reaction, and after the reaction is completed, performing a filtering treatment to obtain lithium carbonate. The present invention has the advantages of not requiring the addition of any auxiliary agents, reduced equipment requirements, a simplified process flow, low costs, no secondary pollution, capable of continuous production, etc.

Description

A method for recycling retired lithium iron phosphate batteries using an electrochemical yin-yang coupled wet process Technical Field

[0001] The present invention belongs to the technical field of lithium battery resource recovery, and in particular relates to a method for recovering retired lithium iron phosphate batteries using an electrochemical yin-yang coupled wet process. Background Art

[0002] The world is currently facing intensifying environmental pollution and energy crises. Consequently, the increasing demands for global energy transformation and carbon emission reduction are prompting countries around the world to accelerate the development of the new energy vehicle industry. Research predicts that by around 2025, conventional fuel vehicles will be completely replaced by new energy vehicles (with sales accounting for only approximately 50% of total passenger car sales). New energy vehicles, such as pure electric vehicles, hybrid vehicles, and biofuel vehicles, will become the future development direction of the automotive industry.

[0003] Lithium-ion power batteries are key components of new energy vehicles. Lithium iron phosphate (LiFePO4) batteries, with their excellent cycle performance and safety, have been widely used in large passenger vehicles (e.g., electric buses and public transit buses). However, over long periods of cycling, lithium loss and electrochemical side reactions, as well as amorphous transformations of the electrode surface structure and oxygen consumption, lead to capacity degradation and eventual failure of LiFePO4 batteries, typically lasting 4-8 years. In recent years, large-scale decommissioning of LiFePO4 batteries has entered a phase of significant decommissioning, with over 1 million tons of spent lithium-ion batteries produced annually. Decommissioned LiFePO4 batteries contain significant amounts of non-ferrous metals such as lithium, iron, nickel, and cobalt. If not properly disposed of, not only will lithium resources be wasted, but fluorine-containing components in their electrolytes can pose potential environmental risks. Furthermore, with the rising price of lithium carbonate, the economic benefits of recycling decommissioned LiFePO4 batteries are becoming increasingly apparent, leading to the emergence of new technologies and processes for recycling decommissioned LiFePO4 batteries.

[0004] Currently, the processing methods for retired lithium iron phosphate batteries are mainly divided into pyrometallurgical and wet leaching. Pyrometallurgical processing is lengthy and prone to Li slagging, resulting in a low overall recovery rate for valuable metals. Wet leaching, through a leaching, impurity removal, and enrichment process, allows the valuable metals in retired lithium iron phosphate to enter solution and be recovered. This method offers the advantages of high metal recovery and impurity removal efficiency, as well as strong technical adaptability. FeLiPO4 has a highly stable olivine structure, and the conductive agent, binder, and graphite coating on the spent lithium iron phosphate material can also severely hinder its decomposition. To fully extract the lithium element, the wet leaching process requires the use of strong acid leaching agents (such as inorganic strong acids such as HCl, H2SO4, and H3PO4) and oxidants (H2O2) to disrupt its chemical structure. Currently, in the cascade recovery of valuable metals from retired lithium iron phosphate batteries, chelating agents and extractants are often used to improve the metal purity of the recovered slag phase. Therefore, wet leaching has disadvantages such as a complex recycling process and an imbalance between saving chemical usage and energy consumption, which increases the cost of process safety and environmental protection and makes it impossible to efficiently and greenly recycle retired lithium iron phosphate batteries.

[0005] For example, patent CN 116750746 A uses a large amount of oxidants, reducing agents and chelating agents to achieve full component recovery of phosphorus, iron and lithium. However, unreacted acid or reducing agent / oxidizing agent will eventually enter the effluent, increase the amount of waste liquid, and cause secondary pollution. Patent CN 102897804 A uses a reaction-extraction coupling method to obtain lithium carbonate with high purity using carbon dioxide as a carbon source, and adds an organic extractant to break the thermodynamic limitation and promote the reaction to produce lithium carbonate products. This method requires oil-water phase separation and stripping regeneration of the extractant, which is complicated and increases energy consumption and cost. Patent CN 115947353 A electrolyzes Cl-containing - The electrolyte generates chlorine, which reacts with water to produce HCl, HClO, and HClO3, which in turn promotes the oxidative decomposition of the lithium iron phosphate waste, resulting in lithium leaching. This method is highly corrosive to equipment, resulting in increased processing and maintenance costs.

[0006] Therefore, in view of the various problems existing in the existing wet recycling process of retired lithium iron phosphate batteries, it is necessary to develop a new method to achieve efficient recycling of retired lithium iron phosphate batteries.

[0007] Summary of the Invention

[0008] In order to solve the above technical problems, the present invention provides a method for recycling retired lithium iron phosphate batteries by electrochemical yin and yang coupling wet method, which realizes the oxidative decomposition of retired lithium iron phosphate batteries by electrolysis without adding any auxiliary agents. 2+ ions are directly oxidized to Fe 3+, promoting the dissociation process of lithium iron phosphate; at the same time, the H2O2 generated by the directional two-electron ORR on the cathode reacts with lithium iron phosphate to produce iron phosphate and ·OH, and the self-catalytic effect of ·OH will further promote the directional activation and deconstruction of lithium iron phosphate. This method has the advantages of mild process conditions, low cost, and no secondary pollution.

[0009] The purpose of the present invention is to provide a method for recycling retired lithium iron phosphate batteries by an electrochemical yin-yang coupled wet process, comprising the following steps:

[0010] S1. Pre-treating retired lithium iron phosphate batteries to obtain lithium iron phosphate waste;

[0011] S2, using an electrochemical system including a working electrode, a counter electrode and a reference electrode to electrolyze the electrolyte, and under the direct oxidation and indirect oxidation of electrons on the anode and cathode electrodes, the lithium iron phosphate waste is oxidized and decomposed to obtain iron phosphate and Li + The electrolyte comprises an acid solution having a concentration of 0.01 mol / L-0.2 mol / L; the electrolyte further comprises the lithium iron phosphate waste material described in S1;

[0012] S3, the iron phosphate and Li + The mixed solution is filtered to obtain iron phosphate and Li + filtrate;

[0013] S4, the Li-containing + Carbon dioxide is introduced into the filtrate to carry out lithium precipitation reaction, and after the reaction is completed, the filtrate is filtered to obtain lithium carbonate.

[0014] In one embodiment of the present invention, in S1, the pretreatment is to discharge, disassemble, crush, screen, and separate materials of retired lithium iron phosphate batteries.

[0015] In one embodiment of the present invention, in S1, the concentration of the acid solution is preferably 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.14 mol / L, 0.16 mol / L, or 0.18 mol / L.

[0016] In one embodiment of the present invention, in S1, the mass proportion of iron in the lithium iron phosphate waste is 30%-40%, and the mass proportion of lithium is 2%-6%.

[0017] In one embodiment of the present invention, in S2, the working electrode and the counter electrode are activated graphene aerogel GA electrodes; and the reference electrode is an Ag / AgCl electrode.

[0018] In one embodiment of the present invention, the activated graphene aerogel GA electrode uses activated graphene aerogel GA as the electrode material and nickel foam as the electrode substrate; the activated graphene aerogel GA is prepared by boiling the graphene aerogel GA with HNO3 and calcining it with N2.

[0019] In one embodiment of the present invention, the boiling time of the HNO3 boiling is 5 min-30 min; the calcination temperature of the N2 calcination is 360°C-540°C.

[0020] Furthermore, the boiling time of the HNO3 boiling is 10min-20min, such as 11min, 12min, 13min, 14min, 15min, 16min, 17min, 18min, and 19min; the calcination temperature of the N2 calcination is 400℃-500℃, such as 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, and 470℃.

[0021] In one embodiment of the present invention, the preparation of the activated graphene aerogel GA electrode specifically includes the following steps:

[0022] S21, dissolving the graphene aerogel GA in HNO3, boiling and washing;

[0023] Under an S22 and N2 atmosphere, the graphene aerogel GA washed with S21 is calcined to obtain an activated graphene aerogel GA;

[0024] S23, pressing the activated graphene aerogel GA described in S2 onto the nickel foam by physical methods to form the activated graphene aerogel GA electrode.

[0025] In one embodiment of the present invention, in S2, the electrolysis conditions are: electrode potential is 0V-5V, and electrolysis time is 0.75h-5h.

[0026] Furthermore, in S2, the electrolysis conditions are: electrode potential is 0.1V-2V, and electrolysis time is 0.75h-3h.

[0027] Preferably, in S2, the electrolysis conditions are: electrode potential is 0.3V-1V, such as 0.4V, 0.5V, 0.6V, 0.7V, 0.8V, 0.9V; and electrolysis time is 0.75h-2h, such as 1h, 1.25h, 1.5h, 1.75h.

[0028] In one embodiment of the present invention, in S2, the mass ratio of the electrolyte to the lithium iron phosphate waste is 4.5-10:1.

[0029] Furthermore, in S2, the mass ratio of the electrolyte to the lithium iron phosphate waste is 4.5-8:1.

[0030] Preferably, in S2, the mass ratio of the electrolyte to the lithium iron phosphate waste is 4.5-6:1, such as (5:1), (5.5:1).

[0031] In one embodiment of the present invention, in S2, the acid is selected from one or more of sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid and citric acid.

[0032] In one embodiment of the present invention, in S2, the principle of the oxidative decomposition is as follows:

[0033] The following reactions occur at the anode: Fe 2+ -e - →Fe 3+

[0034] That is, under direct oxidation, the lithium iron phosphate waste is oxidatively dissociated.

[0035] The reaction at the cathode is as follows: O2+2H + +2e - →H2O2 H2O2+Fe 2+ →Fe 3+ +OH - +·OH Fe 2+ +·OH→Fe 3+ +OH -

[0036] That is, there are two indirect oxidation effects at the cathode. The H2O2 produced by the directional two-electron ORR at the cathode has an indirect oxidation effect on the lithium iron phosphate waste powder, and the reaction produces iron phosphate and ·OH, and the self-catalytic effect of ·OH will further promote the directional activation and deconstruction of the lithium iron phosphate waste.

[0037] In one embodiment of the present invention, in S4, the temperature of the lithium precipitation reaction is 10° C.-100° C., and the time is 0.1 h-5 h.

[0038] Furthermore, in S4, the temperature of the lithium precipitation reaction is 20° C.-90° C., and the time is 0.3 h-3 h.

[0039] Preferably, in S4, the temperature of the lithium precipitation reaction is 30°C-60°C, such as 35°C, 40°C, 45°C, 50°C, 55°C; and the time is 0.5h-2h, such as 0.75h, 1h, 1.25h, 1.5h, 1.75h.

[0040] In one embodiment of the present invention, the recovered iron phosphate and lithium carbonate can be reused in lithium-ion batteries.

[0041] The technical solution of the present invention has the following advantages over the prior art:

[0042] (1) The method of the present invention realizes the oxidative decomposition of lithium iron phosphate batteries by electrolyzing low-concentration media. The whole process does not require the consumption of electrolyte, and does not require the consumption of excessive acid and alkali to neutralize the solution, thereby reducing waste liquid discharge, eliminating secondary pollution, and significantly reducing costs. In addition, electrolytes with lower acid concentrations are conducive to the formation of iron phosphate precipitation, reducing Fe in the solution. 3+ ion content, thereby improving the purity of subsequent recovered lithium products.

[0043] (2) The method described in the present invention does not require the addition of any auxiliary agents, such as O2, Cl2, H2O2, etc., which reduces transportation and storage costs, lowers equipment requirements, simplifies the process flow, is simple to operate, has no secondary pollution, and can be produced continuously.

[0044] (3) The method of the present invention can be used for continuous and long-term production, can bring better environmental and economic benefits, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein:

[0046] FIG1 is a process flow chart of the method for recycling retired lithium iron phosphate batteries using an electrochemical cation-coupled wet process according to the present invention;

[0047] FIG2 is a schematic diagram showing the principle of the method for recycling retired lithium iron phosphate batteries using an electrochemical cathode-ion coupling wet process according to the present invention;

[0048] FIG3 is a characterization diagram of the activated graphene aerogel GA according to an embodiment of the present invention; wherein a is a SEM image and b is a Raman spectrum diagram;

[0049] FIG4 is a graph showing the electrical performance of the working electrode of the present invention; wherein a is the electron spin resonance (ESR) spectrum, b is the constant current charge-discharge curve, and c is the long-period cycle curve. DETAILED DESCRIPTION

[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0051] In the present invention, unless otherwise specified, the pretreatment in the embodiments is to discharge, disassemble, crush, screen, etc. the retired lithium iron phosphate batteries, and to separate materials such as the separator, adhesive, and aluminum foil.

[0052] In the present invention, unless otherwise specified, the preparation of the activated graphene aerogel GA electrode used in the examples specifically includes the following steps: (1) boiling 100 mg of graphene aerogel GA in 4 mL of HNO3 for 15 min, and then washing it with ultrapure water multiple times; (2) calcining the washed graphene aerogel GA at 450°C for 1 h in a tubular furnace under N2 atmosphere to obtain activated graphene aerogel GA; (3) pressing the activated graphene aerogel GA onto nickel foam by physical methods to form an activated graphene aerogel GA electrode, which is then dried for later use.

[0053] Example 1

[0054] 1 , the electrochemical cation-coupled wet process for recycling retired lithium iron phosphate batteries of the present invention specifically comprises the following steps:

[0055] S1. After pre-processing, retired lithium iron phosphate batteries are obtained to obtain lithium iron phosphate waste powder with Fe accounting for about 35% by mass and Li accounting for 4.4% by mass;

[0056] S2, using 0.1M H2SO4 solution as electrolyte, activated graphene aerogel GA electrode as working electrode / counter electrode (cation electrode), Ag / AgCl electrode as reference electrode, and connected to CHI760E electrochemical workstation, controlling the electrode potential to 0.6V, electrolysis time to 1h, electrochemical oxidation decomposition of lithium iron carbonate waste to obtain iron phosphate and Li + wherein the electrolyte further comprises lithium iron phosphate waste, and the mass ratio of the electrolyte to the lithium iron phosphate waste is 5:1;

[0057] S3, after the electrolysis is completed, the iron phosphate and Li + The mixture was filtered, washed twice with water, and dried in an oven at 100 ° C for 2 h to obtain iron phosphate and Li-containing + filtrate;

[0058] S4, to contain Li + Carbon dioxide was introduced into the filtrate to carry out lithium precipitation reaction, wherein the reaction temperature was 40℃ and the reaction time was 1h. + After the precipitation reaction is completed, the product is filtered, washed twice with water, and dried in a vacuum drying oven at 80° C. for 4 h to obtain lithium carbonate precipitate.

[0059] After testing, the Li + The leaching rate (mass of Li element in the electrolyte after electrolysis / mass of Li element in the lithium iron phosphate waste powder before electrolysis × 100%) is 99.55%. In this embodiment, the proportion of iron atoms in the lithium carbonate precipitate is 0.076%. The electrolysis principle is shown in Figure 2.

[0060] Example 2

[0061] The electrochemical cation-coupled wet process for recycling retired lithium iron phosphate batteries of the present invention specifically comprises the following steps:

[0062] S1. After pre-processing, retired lithium iron phosphate batteries are obtained to obtain lithium iron phosphate waste powder with Fe accounting for about 35% by mass and Li accounting for 4.4% by mass;

[0063] S2, using 0.1M H3PO4 solution as electrolyte, activated graphene aerogel GA electrode as working electrode / counter electrode (cation electrode), Ag / AgCl electrode as reference electrode, and connected to CHI760E electrochemical workstation, controlling the electrode potential to 0.6V, electrolysis time to 1h, electrochemical oxidation decomposition of waste in iron carbonate to obtain iron phosphate and Li + wherein the electrolyte further comprises lithium iron phosphate waste, and the mass ratio of the electrolyte to the lithium iron phosphate waste is 5:1;

[0064] S3, after the electrolysis is completed, the iron phosphate and Li + The mixture was filtered, washed twice with water, and dried in an oven at 100 ° C for 2 h to obtain iron phosphate and Li-containing + filtrate;

[0065] S4, to contain Li + Carbon dioxide was introduced into the filtrate to carry out lithium precipitation reaction, wherein the reaction temperature was 40℃ and the reaction time was 1h. + After the precipitation reaction is completed, the product is filtered, washed twice with water, and dried in a vacuum drying oven at 80° C. for 4 h to obtain lithium carbonate precipitate.

[0066] After testing, the Li + The leaching rate is 99.18%, and the proportion of iron atoms in the lithium carbonate precipitate in this embodiment is 0.051%.

[0067] Example 3

[0068] The electrochemical cation-coupled wet process for recycling retired lithium iron phosphate batteries of the present invention specifically comprises the following steps:

[0069] S1. After pre-processing, retired lithium iron phosphate batteries are obtained to obtain lithium iron phosphate waste powder with Fe accounting for about 35% by mass and Li accounting for 4.4% by mass;

[0070] S2, using 0.1M acetic acid solution as electrolyte, activated graphene aerogel GA electrode as working electrode / counter electrode (cation electrode), Ag / AgCl electrode as reference electrode, and connected to CHI760E electrochemical workstation, controlling the electrode potential to 0.6V, electrolysis time to 1h, electrochemical oxidation decomposition of waste in iron carbonate to obtain iron phosphate and Li + wherein the electrolyte further comprises lithium iron phosphate waste, and the mass ratio of the electrolyte to the lithium iron phosphate waste is 5:1;

[0071] S3, after the electrolysis is completed, the iron phosphate and Li + The mixture was filtered, washed twice with water, and dried in an oven at 100 ° C for 2 h to obtain iron phosphate and Li-containing + filtrate;

[0072] S4, to contain Li + Carbon dioxide was introduced into the filtrate to carry out lithium precipitation reaction, wherein the reaction temperature was 40℃ and the reaction time was 1h. + After the precipitation reaction is completed, the product is filtered, washed twice with water, and dried in a vacuum drying oven at 80° C. for 4 h to obtain lithium carbonate precipitate.

[0073] After testing, the Li + The leaching rate is 99.04%. In this embodiment, the iron element atoms in the lithium carbonate precipitate account for 0.088%.

[0074] Comparative Example 1

[0075] The method is basically the same as Example 1, except that the calcination temperature of the activated graphene aerogel GA electrode is 350°C.

[0076] After testing, the Li + The leaching rate is 94.37%. In this embodiment, the iron element atoms in the lithium carbonate precipitation product account for 0.824%.

[0077] Comparative Example 2

[0078] The method is basically the same as Example 1, except that the activated graphene aerogel GA electrode is calcined at 550°C.

[0079] After testing, the Li + The leaching rate is 96.33%. In this embodiment, the iron element atoms in the lithium carbonate precipitation product account for 0.501%.

[0080] Comparative Example 3

[0081] The method is basically the same as Example 1, except that the mass ratio of the electrolyte to the lithium iron phosphate waste is 4:1.

[0082] After testing, the Li + The leaching rate is 97.16%. In this embodiment, the iron element atoms in the lithium carbonate precipitation product account for 0.182%.

[0083] Comparative Example 4

[0084] The process is basically the same as in Example 1, except that the electrolysis time is 0.5 h.

[0085] After testing, the Li + The leaching rate is 85.64%. In this embodiment, the proportion of iron atoms in the lithium carbonate precipitation product is 1.557%.

[0086] Test Example 1

[0087] The surface morphology of the activated graphene aerogel GA electrode used in the embodiment was characterized, and the results are shown in Figure 3. From the scanning electron microscope image in Figure 3a, it can be seen that GA is a highly porous structure composed of graphene sheets with a specific surface area of ​​143.2 m 2 / g, and the average pore diameter is 3.5nm. As can be seen from the Raman spectrum of Figure 3b, the activated graphene aerogel GA electrode material has a Raman peak at 1358cm -1 and 1591cm -1 The two clear peaks at 30° correspond to the D band of disordered carbon and the G band of graphitic carbon, respectively, with ID / IG values ​​of 0.98, indicating the presence of highly active defect sites. The results show that the excellent electronic, structural, and catalytic properties of activated graphene aerogel GA can enhance the mass transport and electrocatalytic performance of ORR.

[0088] Test Example 2

[0089] Based on Example 1, the working electrode was subjected to an electrical performance test, and the electron spin resonance (ESR) spectrum is shown in Figure 4a. As can be seen from Figure 4a, the activated graphene aerogel GA electrode has a strong ESR intensity, indicating that the oxygen vacancy concentration of the activated graphene aerogel GA is high, which is conducive to the redox reaction of the electrode-oriented double electron self-selected resonance. A constant current charge and discharge (GCD) test was carried out under a current density of 0.2A / g to determine the capacitance of the activated graphene aerogel GA electrode material, as shown in Figure 4b. As can be seen from Figure 4b, the discharge time at 0.2A / g is large and has good capacitance. Under a current density of 5A / g, the long-term cycle curve of the activated graphene aerogel GA electrode is shown in Figure 4c. As can be seen from Figure 4c, the activated graphene aerogel GA electrode has excellent charge and discharge performance and good cycle stability of 10,000 cycles. The results show that the activated graphene aerogel GA electrode material has excellent stability and can be reused.

[0090] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for recycling retired lithium iron phosphate batteries by electrochemical yin-yang coupling wet process, characterized in that: The following steps are included: S1. Pre-treating retired lithium iron phosphate batteries to obtain lithium iron phosphate waste; S2, using an electrochemical system including a working electrode, a counter electrode and a reference electrode to electrolyze the electrolyte, and under the direct oxidation and indirect oxidation of electrons on the positive and negative electrodes, the lithium iron phosphate waste is oxidized and decomposed to obtain iron phosphate and Li + The electrolyte comprises an acid solution having a concentration of 0.01 mol / L-0.2 mol / L; the electrolyte also comprises the lithium iron phosphate waste described in S1; S3, the iron phosphate and Li + The mixed solution is filtered to obtain iron phosphate and Li + filtrate; S4, the Li-containing + Carbon dioxide is introduced into the filtrate to perform lithium precipitation reaction, and after the reaction is completed, the filtrate is filtered to obtain lithium carbonate.

2. The method for recycling retired lithium iron phosphate batteries by electrochemical cation-coupled wet method according to claim 1, characterized in that: In S1, the pretreatment is to discharge, disassemble, crush, screen and classify the materials of the retired lithium iron phosphate batteries.

3. The method for recycling retired lithium iron phosphate batteries by electrochemical yin-yang coupling wet method according to claim 1, characterized in that: In S1, the mass proportion of iron in the lithium iron phosphate waste is 30%-40%, and the mass proportion of lithium is 2%-6%.

4. The method for recycling retired lithium iron phosphate batteries by electrochemical yin-yang coupling wet method according to claim 1, characterized in that: In S2, the working electrode and the counter electrode are activated graphene aerogel GA electrodes; and the reference electrode is an Ag / AgCl electrode.

5. The method for recycling retired lithium iron phosphate batteries by electrochemical yin-yang coupling wet method according to claim 4, characterized in that: The activated graphene aerogel GA electrode uses activated graphene aerogel GA as an electrode material and nickel foam as an electrode substrate; the activated graphene aerogel GA is prepared by boiling the graphene aerogel GA with HNO3 and calcining it with N2.

6. The method for recycling retired lithium iron phosphate batteries by electrochemical yin-yang coupling wet method according to claim 5, characterized in that: The boiling time of the HNO3 boiling is 5 min-30 min; the calcination temperature of the N2 calcination is 360°C-540°C.

7. The method for recycling retired lithium iron phosphate batteries by electrochemical yin-yang coupling wet method according to claim 1, characterized in that: In S2, the electrolysis conditions are: electrode potential is 0V-5V, and electrolysis time is 0.75h-5h.

8. The method for recycling retired lithium iron phosphate batteries by electrochemical cation-coupled wet method according to claim 1, characterized in that: In S2, the mass ratio of the electrolyte to the lithium iron phosphate waste is 4.5-10:

1.

9. The method for recycling retired lithium iron phosphate batteries by electrochemical cation-coupled wet method according to claim 1, characterized in that: In S2, the acid is selected from one or more of sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid and citric acid.

10. The method for recycling retired lithium iron phosphate batteries by electrochemical cation-coupled wet method according to claim 1, characterized in that: In S4, the temperature of the lithium precipitation reaction is 10°C-100°C, and the time is 0.1h-5h.

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