Method for electrochemical yin-yang coupling wet recovery of retired lithium iron phosphate battery

Abstract

The present application relates to a kind of electrochemical cathode and anode coupling wet recovery method of retired lithium iron phosphate battery, belong to lithium battery resource recovery technical field.The method of the present application includes the following steps, S1, retired lithium iron phosphate battery is pretreated, and lithium iron phosphate waste is obtained;S2, electrolyte is electrolyzed using the electrochemical system including working electrode, counter electrode and reference electrode, the lithium iron phosphate waste is oxidized and decomposed, and mixed solution containing iron phosphate and Li + Is obtained;The electrolyte includes acid solution;The electrolyte also includes lithium iron phosphate waste;S3, the mixed solution containing iron phosphate and Li + Is filtered, and iron phosphate and Li + Containing filtrate are obtained;S4, carbon dioxide is introduced into the Li + Containing filtrate of S3 and is subjected to lithium precipitation reaction, after reaction, filtration is carried out, and lithium carbonate is obtained.The method of the present application does not need to add any auxiliary agent, reduces the requirement to equipment, simplifies technological process, and has the advantages such as low cost, no secondary pollution and continuous production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium battery resource recycling, and particularly relates to a method for electrochemically recovering retired lithium iron phosphate batteries in a cathode-anode coupling wet process. BACKGROUND

[0002] At present, the world is facing the problem of intensifying environmental pollution and energy crisis. Therefore, the global energy transformation and upgrading and the increasing demand for carbon emission reduction have accelerated the pace of development of the new energy vehicle industry in various countries in the world. It is predicted that ordinary fuel vehicles will be completely replaced by new energy vehicles (the sales volume will account for about 50% of the total sales volume of passenger vehicles) by around 2025, and new energy vehicles such as pure electric vehicles, hybrid vehicles and biofuel vehicles will become the development direction of the future automobile industry.

[0003] Lithium ion power batteries are key components of new energy vehicles, and lithium iron phosphate (LiFePO4) batteries have been widely used in large passenger vehicles (electric buses, public buses, etc.) due to their excellent cycle performance and safety performance. However, during the long-term cycle process, the large loss of lithium and the electrochemical side reactions, as well as the amorphous transformation and oxygen consumption of the electrode surface structure, lead to the capacity attenuation and final failure of the lithium iron phosphate battery, and the service life is usually 4-8 years. In recent years, the lithium iron phosphate battery has entered the large-scale retirement stage, and more than 1 million tons of waste lithium ion batteries will be retired each year. Retired lithium iron phosphate batteries contain a large amount of lithium, iron, nickel, cobalt and other non-ferrous metal resources. If not properly disposed of, not only will it waste lithium resources, but the fluorine-containing components in the electrolyte will also pose a potential threat to the environment. In addition, with the continuous rise in the price of lithium carbonate, the economic benefits of recycling retired lithium iron phosphate batteries are gradually emerging, and emerging technologies and processes for recycling retired lithium iron phosphate batteries have emerged.

[0004] Currently, the treatment processes of retired lithium iron phosphate batteries mainly include pyrometallurgical process and hydrometallurgical process. Among them, the pyrometallurgical process has a long flow, and is easy to cause Li slagging, resulting in a low comprehensive recovery rate of valuable metals. The hydrometallurgical process makes the valuable metals in the retired lithium iron phosphate battery enter the solution through the processes of leaching, impurity removal and enrichment, and is recovered, and has the advantages of high metal recovery rate and impurity removal efficiency, and strong technical adaptability. FeLiPO4 has a high stability olivine structure, and the conductive agent, binder and graphite coating layer on the failed lithium iron phosphate material will also seriously hinder its decomposition. In order to realize the full extraction of lithium elements, the hydrometallurgical process needs to destroy its chemical structure with the aid of strong acid leaching agents (such as HCl, H2SO4, H3PO4 and other inorganic strong acids) and oxidizing agents (H2O2). At present, in the process of recovering valuable metals from retired lithium iron phosphate batteries in stages, complexing agents and extractants are often used to improve the metal purity of the recovery residue phase. Therefore, the hydrometallurgical process has the disadvantages of complex recovery process, imbalance between saving chemical consumption and energy consumption, and the like, increases the cost of process environmental protection, and cannot efficiently and greenly recover the retired lithium iron phosphate battery.

[0005] For example, patent CN 116750746A realizes the full-component recovery of phosphorus, iron and lithium by using a large amount of oxidizing agent, reducing agent and complexing agent. However, the unreacted acid or reducing agent / oxidizing agent will eventually enter the effluent, increasing the amount of waste liquid and causing secondary pollution. Patent CN 102897804 A obtains high-purity lithium carbonate by using carbon dioxide as a carbon source through a reaction-extraction coupling method, adding an organic extractant to break the thermodynamic limit and promote the reaction to proceed in the direction of generating lithium carbonate products. This method needs to separate the extractant into oil and water phases and regenerate by back extraction, and the process flow is complex, increasing energy consumption and cost. Patent CN 115947353 A generates chlorine gas by electrolyzing an electrolyte, and reacts with water to generate HCl, HClO and HClO3, thereby promoting the oxidative decomposition of lithium iron phosphate waste and leaching lithium. This method has strong corrosiveness to equipment, increasing the processing cost and maintenance cost. - Electrolyte, generate chlorine, and react with water to generate HCl, HClO and HClO3, thereby promoting the oxidative decomposition of lithium iron phosphate waste and leaching lithium. This method has strong corrosiveness to equipment, increasing the processing cost and maintenance cost.

[0006] Therefore, in view of various problems existing in the current hydrometallurgical recovery process of retired lithium iron phosphate batteries, a new way needs to be developed to realize the efficient recovery of retired lithium iron phosphate batteries. SUMMARY

[0007] To solve the above technical problems, the present application provides a method for electrochemically recovering retired lithium iron phosphate batteries by coupling anode and cathode, which realizes the oxidative decomposition of retired lithium iron phosphate batteries by electrolysis without adding any auxiliary agent, and Fe 2+ ion is directly oxidized to Fe 3+The method promotes the dissociation process of lithium iron phosphate; meanwhile, H2O2 produced by directional two-electron ORR on the cathode reacts with lithium iron phosphate to produce iron phosphate and ·OH, and the autocatalytic effect of ·OH further promotes the directional activation and deconstruction of lithium iron phosphate, and the method has the advantages of mild process conditions, low cost and no secondary pollution.

[0008] The application aims to provide an electrochemical cathode and anode coupling wet recovery method for retired lithium iron phosphate batteries, comprising the following steps,

[0009] S1, pretreating the retired lithium iron phosphate battery to obtain lithium iron phosphate waste;

[0010] S2, electrolyzing an electrolyte by using an electrochemical system comprising a working electrode, a counter electrode and a reference electrode; under the direct and indirect oxidation of electrons on the cathode and anode, the lithium iron phosphate waste is oxidized and decomposed to obtain a mixed solution containing iron phosphate and Li + ; the electrolyte comprises an acid solution with a concentration of 0.01-0.2 mol / L; the electrolyte further comprises the lithium iron phosphate waste in S1;

[0011] S3, filtering the mixed solution containing iron phosphate and Li + in S2 to obtain iron phosphate and a Li + containing filtrate;

[0012] S4, introducing carbon dioxide into the Li + containing filtrate in S3 to perform a lithium precipitation reaction, and performing filtering treatment after the reaction to obtain lithium carbonate.

[0013] In an embodiment of the application, in S1, the pretreatment is discharging, disassembling, crushing, screening and material distinguishing of the retired lithium iron phosphate battery.

[0014] In an embodiment of the application, 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.

[0015] In an embodiment of the application, in S1, the mass percentage of iron in the lithium iron phosphate waste is 30%-40%, and the mass percentage of lithium is 2%-6%.

[0016] In an embodiment of the application, in S2, the working electrode and the counter electrode are activated graphene aerogel GA electrodes; and the reference electrode is an Ag / AgCl electrode.

[0017] In one embodiment of the present application, the activated graphene aerogel GA electrode uses activated graphene aerogel GA as electrode material and uses foamed nickel as electrode substrate; the activated graphene aerogel GA is prepared by boiling and N2 calcining graphene aerogel GA with HNO3.

[0018] In one embodiment of the present application, the boiling time of the HNO3 boiling is 5 min-30 min; the calcining temperature of the N2 calcining is 360℃-540℃.

[0019] Further, the boiling time of the HNO3 boiling is 10 min-20 min, such as 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min; the calcining temperature of the N2 calcining is 400℃-500℃, such as 410℃, 420℃, 430℃, 440℃, 450℃, 460℃, 470℃.

[0020] In one embodiment of the present application, the preparation of the activated graphene aerogel GA electrode specifically comprises the following steps:

[0021] S21, dissolving graphene aerogel GA in HNO3 and boiling and washing;

[0022] S22, calcining graphene aerogel GA washed in S21 under N2 atmosphere to obtain activated graphene aerogel GA;

[0023] S23, attaching the activated graphene aerogel GA in S2 on foamed nickel by physical method to form the activated graphene aerogel GA electrode.

[0024] In one embodiment of the present application, in S2, the electrolysis condition is that the electrode potential is 0V-5V and the electrolysis time is 0.75h-5h.

[0025] Further, in S2, the electrolysis condition is that the electrode potential is 0.1V-2V and the electrolysis time is 0.75h-3h.

[0026] Preferably, in S2, the electrolysis condition is that the electrode potential is 0.3V-1V, such as 0.4V, 0.5V, 0.6V, 0.7V, 0.8V, 0.9V; and the electrolysis time is 0.75h-2h, such as 1h, 1.25h, 1.5h, 1.75h.

[0027] In one embodiment of the present application, in S2, the mass ratio of the electrolyte to the lithium iron phosphate waste is 4.5-10:1.

[0028] Further, in S2, the mass ratio of the electrolyte to the lithium iron phosphate waste is 4.5-8:1.

[0029] 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).

[0030] In an embodiment of the present application, in S2, the acid is selected from one or more of sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid and citric acid.

[0031] In an embodiment of the present application, in S2, the principle of oxidative decomposition is as follows:

[0032] The reaction on the anode is as follows:

[0033] Fe 2+ -e - →Fe 3+

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

[0035] The reaction on the cathode is as follows:

[0036] O2+2H + +2e - →H2O2

[0037] H2O2+Fe 2+ →Fe 3+ +OH - +·OH

[0038] Fe 2+ +·OH→Fe 3+ +OH -

[0039] That is, there are two kinds of indirect oxidation on the cathode, the H2O2 produced by the directional two-electron ORR on the cathode has indirect oxidation on the lithium iron phosphate waste powder, and the reaction generates iron phosphate and ·OH, and the autocatalytic effect of ·OH further promotes the directional activation and deconstruction of the lithium iron phosphate waste.

[0040] In an embodiment of the present application, in S4, the temperature of the lithium deposition reaction is 10-100℃, and the time is 0.1-5h.

[0041] Further, in S4, the temperature of the lithium deposition reaction is 20-90℃, and the time is 0.3-3h.

[0042] Preferably, in S4, the temperature of the lithium precipitation reaction is 30-60°C, such as 35°C, 40°C, 45°C, 50°C, 55°C; the time is 0.5-2h, such as 0.75h, 1h, 1.25h, 1.5h, 1.75h.

[0043] In an embodiment of the present application, the recovered iron phosphate and lithium carbonate can be reused in lithium ion batteries.

[0044] The technical solution of the present application has the following advantages compared with the prior art:

[0045] (1) The method described in the present application realizes the oxidative decomposition of lithium iron phosphate batteries by electrolyzing low-concentration medium. The entire process does not consume electrolyte, does not consume excess acid and base to neutralize the solution, reduces waste liquid discharge, has no secondary pollution, and significantly reduces costs. In addition, the electrolyte with low acid concentration is conducive to the formation of iron phosphate precipitation, reduces the Fe 3+ ion content in the solution, and improves the purity of the subsequent recovered lithium product.

[0046] (2) The method described in the present application does not need to add any auxiliary agents such as O2, Cl2, H2O2, etc., reduces transportation and storage costs, reduces the requirements for equipment, simplifies the process flow, is easy to operate, has no secondary pollution, and can be continuously produced, etc.

[0047] (3) The method described in the present application can be used for continuous and long-period production, can bring better environmental and economic benefits, and has good application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to make the content of the present application easier to be clearly understood, the present application will be further described in detail below according to specific embodiments of the present application and in combination with the drawings, in which:

[0049] Figure 1 The process flow chart of the method for electrochemically recovering retired lithium iron phosphate batteries by coupling wet cathode and anode in the present application;

[0050] Figure 2 The principle schematic diagram of the method for electrochemically recovering retired lithium iron phosphate batteries by coupling wet cathode and anode in the present application;

[0051] Figure 3 The characterization diagram of activated graphene aerogel GA in the embodiment of the present application; wherein, a is a SEM image, and b is a Raman spectrum diagram;

[0052] Figure 4 The electrical performance test diagram of the working electrode in the present application; wherein, a is an electron spin resonance (ESR) spectrum, b is a constant current charge-discharge curve, and c is a long-period cycle curve. DETAILED DESCRIPTION

[0053] The present application will be further described in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand and implement the present application, but the embodiments are not limiting to the present application.

[0054] In the present application, unless otherwise specified, the pretreatment in the examples is to discharge, disassemble, crush, sieve, etc. the retired lithium iron phosphate battery, and separate the materials such as the separator, the adhesive, and the aluminum foil for separate treatment.

[0055] In the present application, unless otherwise specified, the preparation of the activated graphene aerogel GA electrode used in the examples specifically includes the following steps: (1) 100 mg of graphene aerogel GA is boiled in 4 mL of HNO3 for 15 min, and then washed with ultrapure water multiple times; (2) the washed graphene aerogel GA is calcined at 450℃ for 1 h in a tube furnace under N2 atmosphere to obtain the activated graphene aerogel GA; (3) the activated graphene aerogel GA is attached to the foam nickel by physical method to form the activated graphene aerogel GA electrode, and dried for standby use.

[0056] Example 1

[0057] Referring to Figure 1 The method for electrochemical cathode and anode coupling wet recovery of retired lithium iron phosphate battery of the present application specifically includes the following steps:

[0058] S1, the retired lithium iron phosphate battery is pretreated to obtain lithium iron phosphate waste powder with a mass percentage of Fe of about 35% and a mass percentage of Li of 4.4%;

[0059] S2, using 0.1M H2SO4 solution as the electrolyte, using the activated graphene aerogel GA electrode as the working electrode / counter electrode (cathode and anode), using the Ag / AgCl electrode as the reference electrode, and connecting to the CHI760E electrochemical workstation, the electrode potential is controlled at 0.6V, and the electrolysis time is 1h, the electrochemical oxidation and decomposition of the lithium iron carbonate waste is carried out, and a mixed solution containing lithium iron phosphate and Li + is obtained; wherein the electrolyte further includes the lithium iron phosphate waste, and the mass ratio of the electrolyte to the lithium iron phosphate waste is 5:1;

[0060] S3, after the electrolysis is completed, the mixed solution containing lithium iron phosphate and Li + is filtered, then washed with water twice, and dried in a 100℃ oven for 2h to obtain the lithium iron phosphate and the Li + containing filtrate;

[0061] S4, carbon dioxide is introduced into the Li + containing filtrate for lithium precipitation reaction, wherein the reaction temperature is 40℃, the reaction time is 1h, and after the Li +After the precipitation reaction was complete, the mixture was filtered, washed twice with water, and dried in a vacuum drying oven at 80°C for 4 hours to obtain lithium carbonate precipitate.

[0062] Upon testing, the Li in the decommissioned lithium iron phosphate battery in this embodiment was found to be... + The leaching rate (mass of Li in the electrolyte after electrolysis / mass of Li in the lithium iron phosphate waste powder before electrolysis × 100%) was 99.55%. In this embodiment, the iron atom ratio in the lithium carbonate precipitate was 0.076%. The electrolysis principle is as follows: Figure 2 As shown.

[0063] Example 2

[0064] The electrochemical anodic-cation coupling wet process for recycling retired lithium iron phosphate batteries of the present invention specifically includes the following steps:

[0065] S1. Retired lithium iron phosphate batteries, after pretreatment, yield lithium iron phosphate waste powder with a mass percentage of approximately 35% Fe and 4.4% Li.

[0066] S2. Using 0.1M H3PO4 solution as the electrolyte, an activated graphene aerogel GA electrode as the working / counter electrode (cathode and cathode), and an Ag / AgCl electrode as the reference electrode, and connected to a CHI760E electrochemical workstation, the electrode potential was controlled at 0.6V and the electrolysis time was 1h to perform electrochemical oxidative decomposition of waste ferric carbonate, yielding iron phosphate and Li. + The mixture; wherein the electrolyte also includes lithium iron phosphate waste, and the mass ratio of electrolyte to lithium iron phosphate waste is 5:1;

[0067] S3. After electrolysis is complete, for products containing ferric phosphate and Li... + The mixture was filtered, washed twice with water, and dried in an oven at 100°C for 2 hours to obtain ferric phosphate and Li-containing compounds. + filtrate;

[0068] S4, Towards Li + Carbon dioxide was bubbled into the filtrate to carry out a lithium precipitation reaction, with the reaction temperature at 40℃ and the reaction time at 1 hour, until Li + After the precipitation reaction was complete, the mixture was filtered, washed twice with water, and dried in a vacuum drying oven at 80°C for 4 hours to obtain lithium carbonate precipitate.

[0069] Upon testing, the Li in the decommissioned lithium iron phosphate battery in this embodiment was found to be... + The leaching rate was 99.18%, and the proportion of iron atoms in the lithium carbonate precipitate in this embodiment was 0.051%.

[0070] Example 3

[0071] The electrochemical anodic-cation coupling wet process for recycling retired lithium iron phosphate batteries of the present invention specifically includes the following steps:

[0072] S1. Retired lithium iron phosphate batteries, after pretreatment, yield lithium iron phosphate waste powder with a mass percentage of approximately 35% Fe and 4.4% Li.

[0073] S2. Using 0.1M acetic acid solution as the electrolyte, an activated graphene aerogel GA electrode as the working / counter electrode (cathode and cathode), and an Ag / AgCl electrode as the reference electrode, and connected to a CHI760E electrochemical workstation, the electrode potential was controlled at 0.6V, and the electrolysis time was 1h to perform electrochemical oxidative decomposition of waste ferric carbonate, yielding iron phosphate and Li. + The mixture; wherein the electrolyte also includes lithium iron phosphate waste, and the mass ratio of electrolyte to lithium iron phosphate waste is 5:1;

[0074] S3. After electrolysis is complete, for products containing ferric phosphate and Li... + The mixture was filtered, washed twice with water, and dried in an oven at 100°C for 2 hours to obtain ferric phosphate and Li-containing compounds. + filtrate;

[0075] S4, Towards Li + Carbon dioxide was bubbled into the filtrate to carry out a lithium precipitation reaction, with the reaction temperature at 40℃ and the reaction time at 1 hour, until Li + After the precipitation reaction was complete, the mixture was filtered, washed twice with water, and dried in a vacuum drying oven at 80°C for 4 hours to obtain lithium carbonate precipitate.

[0076] Upon testing, the Li in the decommissioned lithium iron phosphate battery in this embodiment was found to be... + The leaching rate was 99.04%, and the iron atom ratio in the lithium carbonate precipitate in this embodiment was 0.088%.

[0077] Comparative Example 1

[0078] The process is basically the same as in Example 1, except that the calcination temperature of the activated graphene aerogel GA electrode is 350°C.

[0079] Testing revealed that the Li in the retired lithium iron phosphate batteries in this comparative example... + The leaching rate was 94.37%, and the iron atomic ratio in the lithium carbonate precipitate product in this embodiment was 0.824%.

[0080] Comparative Example 2

[0081] The process is basically the same as in Example 1, except that the activated graphene aerogel GA electrode is calcined at 550°C.

[0082] Testing revealed that the Li in the retired lithium iron phosphate batteries in this comparative example... + The leaching rate was 96.33%, and the iron atomic ratio in the lithium carbonate precipitate product in this embodiment was 0.501%.

[0083] Comparative Example 3

[0084] The process is basically the same as in Example 1, except that the mass ratio of electrolyte to lithium iron phosphate waste is 4:1.

[0085] Testing revealed that the Li in the retired lithium iron phosphate batteries in this comparative example... + The leaching rate was 97.16%, and the iron atomic ratio in the lithium carbonate precipitate product in this embodiment was 0.182%.

[0086] Comparative Example 4

[0087] The process is basically the same as in Example 1, except that the electrolysis time is 0.5 hours.

[0088] Testing revealed that the Li in the retired lithium iron phosphate batteries in this comparative example... + The leaching rate was 85.64%, and the iron atomic ratio in the lithium carbonate precipitate product in this embodiment was 1.557%.

[0089] Test Example 1

[0090] The surface morphology of the activated graphene aerogel GA electrode used in the examples was characterized, and the results are as follows: Figure 3 As shown. From Figure 3 The scanning electron microscope image of GA shows that it is a highly porous structure composed of graphene sheets, with a specific surface area of ​​143.2 m². 2 / g, with an average pore diameter of 3.5nm. From Figure 3 The Raman spectrum of b shows that the activated graphene aerogel GA electrode material at 1358 cm⁻¹ -1 and 1591cm -1 The two distinct peaks at the point 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 transfer and electrocatalytic performance of ORR.

[0091] Test Example 2

[0092] Based on Example 1, the electrical performance of the working electrode was tested, and the electron spin resonance (ESR) spectrum is shown below. Figure 4 As shown in a. From Figure 4As can be seen from Fig. 2a, 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 beneficial to the directional two-electron self-selected resonance redox reaction of the electrode. The galvanostatic charge-discharge (GCD) test was carried out at a current density of 0.2 A / g to determine the capacitance of the activated graphene aerogel GA electrode material, as shown in Fig. 2b. Figure 4 As can be seen from Fig. 2b, the discharge time at 0.2 A / g is large, and the electrode has good capacitance. Figure 4 As can be seen from Fig. 2c, the activated graphene aerogel GA electrode has superior charge-discharge performance and good cycle stability of 10,000 cycles. Figure 4 As can be seen from Fig. 2c, the activated graphene aerogel GA electrode has superior charge-discharge performance and good cycle stability of 10,000 cycles. Figure 4 As can be seen from Fig. 2c, the activated graphene aerogel GA electrode has superior charge-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.

[0093] Obviously, the above examples are only examples for clearly illustrating, not limiting the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, it is not necessary and impossible to enumerate all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for electrochemically coupled wet recycling of decommissioned lithium iron phosphate batteries, characterized in that, Includes the following steps, S1. Pre-treat retired lithium iron phosphate batteries to obtain lithium iron phosphate waste. S2. Electrolysis of the electrolyte is performed using an electrochemical system comprising a working electrode, a counter electrode, and a reference electrode. Under the direct and indirect oxidation of electrons at the cathode and anode, the lithium iron phosphate waste is oxidized and decomposed to obtain a product containing iron phosphate and Li. + The electrolyte comprises a mixture of the following: the electrolyte includes an acid solution with a concentration of 0.01 mol / L to 0.2 mol / L; the electrolyte also includes the lithium iron phosphate waste described in S1; the working electrode and the counter electrode are activated graphene aerogel GA electrodes; 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 graphene aerogel GA with HNO3 and calcining with N2; the calcination temperature of N2 is 360℃-540℃; the reference electrode is an Ag / AgCl electrode; the electrolysis conditions are: electrode potential of 0V-5V, electrolysis time of 0.75h-5h; the mass ratio of the electrolyte to the lithium iron phosphate waste is 4.5-10:1; the acid is selected from one or more of sulfuric acid, phosphoric acid, formic acid, acetic acid, oxalic acid, and citric acid. S3, regarding the iron phosphate and Li contained in S2 + The mixture was filtered to obtain ferric phosphate and Li-containing compounds. + filtrate; S4, Li-containing compounds as described in S3 + Carbon dioxide is passed through the filtrate to carry out a lithium precipitation reaction. After the reaction is complete, the solution is filtered to obtain lithium carbonate.

2. The method for electrochemically coupled wet recycling of decommissioned lithium iron phosphate batteries according to claim 1, characterized in that, In S1, the pretreatment involves discharging, disassembling, crushing, screening, and material differentiation of retired lithium iron phosphate batteries.

3. The method for electrochemically coupled wet recycling of decommissioned lithium iron phosphate batteries according to claim 1, characterized in that, In S1, the mass percentage of iron in the lithium iron phosphate waste is 30%-40%, and the mass percentage of lithium is 2%-6%.

4. The method for electrochemically coupled wet recycling of decommissioned lithium iron phosphate batteries according to claim 1, characterized in that, In S2, the boiling time of the HNO3 is 5 min to 30 min.

5. The method for electrochemically coupled wet recycling of decommissioned lithium iron phosphate batteries according to claim 1, characterized in that, In S4, the lithium precipitation reaction is carried out at a temperature of 10℃-100℃ for a time of 0.1h-5h.

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