System, method and application for iodine-mediated recovery of waste lithium iron phosphate batteries

Abstract

The invention discloses a method for iodine-mediated recovery of waste lithium iron phosphate batteries, which comprises the following steps of: constructing a recyclable iodine redox-mediated lithium extraction reaction system by taking a metal electrode as a cathode, an inert material electrode as an anode and a solution containing zinc ions and oxidizable iodine species as electrolyte; in addition, the invention also provides a system for iodine-mediated recovery of waste lithium iron phosphate batteries and application. According to the method disclosed by the invention, a recyclable iodine redox-mediated lithium extraction reaction system is constructed, high-efficiency recovery of valuable metal lithium and simultaneous acquisition of high-reusability iron phosphate are realized, the lithium removal rate is as high as 93%, and the method has the characteristics of low energy consumption, no need of a large amount of acidic reagents and no discharge of waste liquid.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery material recycling, and particularly relates to a system, a method and an application for iodine-mediated recycling of waste lithium iron phosphate batteries. Background Art

[0002] The lithium recovery from waste lithium iron phosphate materials mainly adopts two methods: hydrometallurgy and pyrometallurgy. Lithium extraction by hydrometallurgy usually includes dissolution leaching and re-recovery by precipitation or solvent extraction. The dissolution leaching process usually uses inorganic acids, organic reagents to react with waste lithium iron phosphate materials. At present, there is also research showing that lithium in waste lithium iron phosphate can be dissolved by strong acids or mixed acids. This method has a relatively high lithium recovery rate, but usually has problems such as large environmental pollution, high consumption of solvent leaching reagents and complex operation. Moreover, the acidic reagents seriously damage the structure of lithium iron phosphate materials, restricting the reuse of iron phosphate. Lithium extraction by pyrometallurgy is usually based on high-temperature roasting of waste lithium iron phosphate materials to release lithium ions. The roasting temperature is usually 800 - 900 °C. Pyrometallurgical lithium extraction has the advantages of fast and efficient extraction process, but it consumes a large amount of energy. At the same time, harmful gases may be generated during the roasting process, posing potential environmental pollution hazards, and it is still difficult to avoid damaging the structure of iron phosphate materials, restricting recycling.

[0003] In the process of implementing the present invention, the inventors found that there are at least the following problems in the prior art: the current methods for recycling lithium iron phosphate materials usually aim at recycling valuable metal lithium, with high energy consumption, large environmental impact and poor material reusability. Providing a method with lower cost, environmental protection and capable of improving the reuse rate of recycled iron phosphate is one of the main ways to solve the above problems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a system, a method and an application for iodine-mediated recycling of waste lithium iron phosphate batteries in view of the above deficiencies of the prior art. This method realizes the simultaneous high-efficiency recovery of valuable metal lithium and high-reusability iron phosphate by constructing a recyclable iodine redox-mediated lithium extraction reaction system, and has the characteristics of low energy consumption, no need for a large amount of acidic reagents and no waste liquid discharge.

[0005] The present invention has the following advantages compared with the prior art:

[0006] 1. By constructing a recyclable iodine redox-mediated lithium extraction reaction system, the present invention realizes the efficient leaching of lithium in waste lithium iron phosphate, with a delithiation rate as high as 93%, and the total energy consumption is only 9.2 MJ / kg, nearly 32% lower than that of traditional wet recycling. The greenhouse gas emission is 1.19 kgCO2 / kg, 35% less than the 1.84 kgCO2 / kg of pyrometallurgical emissions. The method of the present invention can achieve efficient lithium extraction on the basis of avoiding consumption of a large amount of acidic reagents, waste liquid discharge and low energy consumption.

[0007] 2. The present invention creatively realizes the recycling of waste lithium iron phosphate based on the iodine redox system. By constructing a lithium extraction reaction system mediated by a recyclable iodine redox system, the low-oxidation-degree iodine species generated during lithium extraction are repeatedly oxidized into high-oxidation-degree iodine species through an electrochemical reaction, constructing a large iodine species circulation system. The construction process is spontaneous and does not require manual intervention. On the basis of avoiding complex processes and operating conditions, a continuous supply of high-oxidation-degree iodine species in the lithium extraction reaction is achieved.

[0008] 3. The method for iodine-mediated recycling of waste lithium iron phosphate batteries of the present invention can obtain iron phosphate, which can be directly developed into a high-performance oxygen evolution reaction catalyst (OER catalyst) as a raw material without additional purification or impurity removal treatment. It can achieve a high current density at a lower overpotential, and the overpotential is as low as 250 mV@10 mA·cm -2 , and its catalytic performance is superior to that of the commercially available noble metal catalyst RuO2 widely used at present.

[0009] 4. The method for iodine-mediated recycling of waste lithium iron phosphate batteries of the present invention can simultaneously obtain high-purity metallic zinc deposited on the negative electrode, with regular morphology and uniform texture, which can be directly used as a zinc-air battery. The method of the present invention can achieve the simultaneous acquisition of lithium extraction and high-value by-products, with significant economic benefits.

[0010] 5. The method for iodine-mediated recycling of waste lithium iron phosphate batteries of the present invention uses a zinc sheet coated with a sodium alginate coating as the negative electrode, which can not only avoid the consumption of iodine species and the generation of by-product hydrogen gas due to the reaction between iodide ions and zinc in the electrolyte, but also promote the uniform deposition of high-purity zinc on the electrode surface.

[0011] The technical solutions of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0012] Figure 1 is a schematic diagram of the principle of the method for iodine-mediated recycling of waste lithium iron phosphate batteries of the present invention;

[0013] Figure 2 is a UV-Vis spectrogram of the change in the oxidation degree of iodine species during the charge and discharge process;

[0014] Figure 3 is the energy demand curve in the IOR reaction and the OER reaction;

[0015] Figure 4 is the XRD pattern of the product in the method for iodine-mediated recycling of waste lithium iron phosphate batteries;

[0016] Figure 5 is the content of different elements in LFP before and after the method for iodine-mediated recycling of waste lithium iron phosphate batteries;

[0017] Figure 6 Scanning electron microscope image of zinc deposition on the cathode;

[0018] Figure 7 Coulombic efficiency of the cathode deposited with zinc as the electrode in the hydrogen production discharge test;

[0019] Figure 8 Catalytic performance of the ELFP-Ni catalyst prepared from FePO4 as the raw material;

[0020] Figure 9 Effect of different zinc ion concentrations in the electrolyte on the kinetics of lithium extraction;

[0021] Figure 10 Effect of different iodide ion concentrations in the electrolyte on the kinetics of lithium extraction. Detailed implementation manners

[0022] Next, the technical solutions will be described clearly and completely in combination with the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present application.

[0023] In the following description, the term "and / or" is used to describe the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: the case of A alone, the case of B alone, and the case of both A and B existing simultaneously. Where A and B can be singular or plural.

[0024] In the following description, the terms "include", "comprise", "have" and "contain" are all open-ended terms, that is, they are meant to include but not limited to.

[0025] Those skilled in the art should understand that in the following description of the embodiments of the present application, the sequence numbers do not mean the order of execution, and some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

[0026] Those skilled in the art should understand that the numerical ranges in the embodiments of the present application should be understood as specifically disclosing each intermediate value between the upper and lower limits of the range. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present application. The upper and lower limits of these smaller ranges can be independently included or excluded within the range.

[0027] Unless otherwise specified, the technical / scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the art to which this application belongs. Although this application only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this application. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0028] The technical principle adopted in the present invention: By constructing a recyclable iodine redox-mediated lithium extraction reaction system, the cycle of iodine species with different oxidation degrees is realized, and taking this as a mediator, the solid-liquid reaction between iodine species with high oxidation degree and lithium iron phosphate is driven.

[0029] On the one hand, a method for iodine-mediated recovery of waste lithium iron phosphate batteries is provided, including:

[0030] Using a metal electrode as the cathode, an inert material electrode as the anode, and a solution containing zinc ions and oxidizable iodine species as the electrolyte to construct a recyclable iodine redox-mediated lithium extraction reaction system.

[0031] Creatively based on the iodine redox system, a recyclable iodine redox-mediated lithium extraction reaction system is constructed. Using a solution containing oxidizable iodine species with a low oxidation degree as the electrolyte, iodine species with a high oxidation degree are continuously obtained, realizing continuous driving of lithium dissolution from waste lithium iron phosphate batteries.

[0032] In some embodiments, the metal electrode includes a copper electrode, a zinc electrode or a porous metal electrode. The metal electrode includes ordinary metal electrodes commonly used in electrolysis, such as a copper electrode or a zinc electrode, and the porous metal electrode includes a porous copper electrode or a porous zinc electrode.

[0033] In some embodiments, the inert material electrode includes carbon cloth or carbon felt.

[0034] In the process of constructing this recyclable iodine redox-mediated lithium extraction reaction system, the anode is an inert material electrode with high conductivity and corrosion resistance, and the cathode is a metal electrode with high conductivity and deposition performance, which has higher reactivity and can realize efficient lithium extraction. In addition, high-performance and high-efficiency zinc deposition can also be achieved simultaneously.

[0035] In some embodiments, in the solution containing zinc ions and oxidizable iodine species, the source of zinc ions includes zinc sulfate or zinc acetate, and the source of oxidizable iodine species includes sodium iodide or potassium iodide.

[0036] In the process of constructing this cyclic iodine redox-mediated lithium extraction reaction system, the source of zinc ions in the electrolyte is zinc sulfate or zinc acetate, and the source of oxidizable iodine species is sodium iodide or potassium iodide. No toxic compounds are generated during the lithium extraction process, and the lithium extraction process is green and environmentally friendly.

[0037] In some embodiments, the solution containing zinc ions and oxidizable iodine species is a solution containing zinc sulfate and potassium iodide.

[0038] In some embodiments, the metal electrode is a metal electrode coated with a sodium alginate coating.

[0039] Furthermore, by covering the surface of the metal electrode with a sodium alginate coating, direct corrosion of the metal electrode by iodine species can be avoided, the service life of the system can be extended, hydrogen production as a by-product can be inhibited, and the uniformity of zinc deposition can be improved.

[0040] In some embodiments, the metal electrode coated with a sodium alginate coating is a metal electrode coated with a sodium alginate coating obtained by placing an electrode sheet in an aqueous sodium alginate solution and performing electrodeposition; the current density during electrodeposition is 10 - 40 mA·cm -2 , and the discharge time is 5 - 10 s.

[0041] Furthermore, through electrodeposition, a sodium alginate coating is formed on the surface of the zinc sheet to realize the electrodeposition assembly of the sodium alginate coating on the electrode surface. Using the metal electrode coated with a sodium alginate coating prepared by the above method as the electrode for the recyclable iodine redox-mediated lithium extraction reaction system, there is no bulging or falling off during lithium extraction, and it is combined with the electrolyte containing zinc sulfate and potassium iodide to achieve efficient lithium extraction and highly uniform zinc deposition.

[0042] In some embodiments, in the solution containing zinc ions and oxidizable iodine species, the concentration of zinc ions is 0.1 - 1.5 mol / L, and the concentration of oxidizable iodine species is 0.1 - 0.5 mol / L.

[0043] The inventors further found in the research that although the concentration of zinc ions has little effect on lithium extraction kinetics, when the concentration of zinc ions is too low, the zinc deposited on the electrode surface is uneven, and the concentration of oxidizable iodine species directly affects lithium extraction kinetics. When the concentration of iodine species increases, the lithium extraction kinetics accelerates.

[0044] In some embodiments, when using iodine-mediated lithium extraction from waste lithium iron phosphate batteries, the mass of the electrolyte is 100 times the mass of the waste lithium iron phosphate battery, and the current density during lithium extraction is 30 - 40 mA·cm -2 , and the lithium extraction time is 2 - 3 h.

[0045] On the other hand, a system for iodine-mediated recovery of waste lithium iron phosphate batteries is also provided, including an electrolytic cell for containing a solution containing zinc ions and oxidizable iodine species and waste lithium iron phosphate batteries, a metal electrode, and an inert material electrode.

[0046] On the other hand, an application of a system for iodine-mediated recovery of waste lithium iron phosphate batteries is also provided, including applications in lithium extraction and preparation of metallic zinc.

[0047] A series of experiments were conducted before the application of this invention. Now, some test results are listed to further describe the invention in detail, and detailed descriptions will be given in combination with the embodiments below.

[0048] It should be noted that all raw materials and reagents in the following embodiments can be obtained commercially or prepared by conventional methods well-known to those skilled in the art.

[0049] Example 1

[0050] This embodiment provides a method for iodine-mediated recovery of waste lithium iron phosphate batteries, including:

[0051] Step 1: Provide zinc sheets coated with sodium alginate:

[0052] Step 101: Dissolve 1 g of sodium alginate in 50 mL of deionized water to obtain a sodium alginate solution; the sodium alginate is purchased from Macklin, 1% aqueous solution, and the viscosity at 20 °C is 200 - 550 mPa·s;

[0053] Step 102: Place 2 zinc sheets with dimensions of 2 cm × 1 cm each in the sodium alginate solution, and use a BlueTEC electrochemical test system to perform electrodeposition with the two zinc sheets as the anode and cathode respectively to obtain zinc sheets coated with sodium alginate; during the electrodeposition process, the current density is 20 mA·cm -2 , and the discharge time is 5 s;

[0054] Step 2: Construct a recyclable iodine redox-mediated lithium extraction reaction system:

[0055] Step 201: Provide 50 mL of a solution containing zinc sulfate and potassium iodide as the electrolyte; in the electrolyte, the concentration of zinc sulfate is 1 mol / L, and the concentration of potassium iodide is 0.5 mol / L;

[0056] Step 202: Place 0.5 g of waste lithium iron phosphate cathode powder in the electrolyte; the roughly measured lithium content in the waste lithium iron phosphate cathode powder is 43 g / kg;

[0057] Step 203: Use the zinc sheets coated with sodium alginate as the cathode and a carbon cloth with dimensions of 2 cm × 1 cm as the anode, and place them in the above electrolyte containing waste lithium iron phosphate cathode powder to obtain a recyclable iodine redox-mediated lithium extraction reaction system;

[0058] Step 3: Perform lithium extraction:

[0059] Step 301: Connect the anode and cathode in the above-mentioned recyclable iodine redox-mediated lithium extraction reaction system to a Lanhe electrochemical test system, set the current density to 40 mA·cm -2 , the stirring speed to 400 rpm, and perform lithium extraction for 3 h; driven by an external electrical input, I - ions near the anode are oxidized to generate iodine species with a high degree of oxidation. Under the action of the iodine species with a high degree of oxidation, lithium in lithium iron phosphate dissolves out. At the same time, the iodine species are reduced to iodine species with a low degree of oxidation, and the iodine species with a low degree of oxidation continue to be oxidized at the anode, realizing the continuous supply of iodine species with a high degree of oxidation and the continuous dissolution of lithium ions; meanwhile, zinc ions react at the cathode, and high-purity metallic zinc deposits at the cathode; the reaction principle is as Figure 1 shown.

[0060] Step Four: Obtain a lithium carbonate solid product:

[0061] Step 401: Filter the system after lithium extraction to obtain a filtrate and a filtrate containing lithium ions. The filtrate is the solid phase after lithium removal, i.e., FePO4;

[0062] Step 402: Adjust the pH of the filtrate containing lithium ions to 10 with a 1 mol / L potassium hydroxide solution to completely precipitate zinc ions in the filtrate containing lithium ions. Filter to obtain a lithium-containing filtrate. Add a saturated sodium carbonate solution to the lithium-containing filtrate, stir at 90 °C for about 1 h until no more precipitate is formed. The obtained precipitate is lithium carbonate. Dry the precipitate to obtain a lithium carbonate solid product.

[0063] Performance and effects:

[0064] 1.1 Verification of the construction of the recyclable iodine redox-mediated lithium extraction reaction system

[0065] Use UV-Vis spectroscopy to study the change in the oxidation degree of iodine species during the charge and discharge process. The specific process is as follows: Provide a zinc sheet covered with a sodium alginate coating according to Step 1 of Example 1, provide an electrolyte according to Step 201, use the zinc sheet covered with a sodium alginate coating as the cathode, and use a carbon cloth with a size of

[0066] 2 cm × 1 cm as the anode, place it in the above-mentioned electrolyte, set the current density to 40 mA·cm -2 , the stirring speed to 400 rpm. During the experiment, take samples of the electrolyte every 30 s for UV-Vis spectroscopy testing, and observe the changes in the characteristic peaks at 288 nm and 351 nm. The results are as Figure 2 shown in a of Figure 2 . As can be seen from a of - , characteristic peaks attributed to I3 - appear at 288 nm and 351 nm. As time prolongs, the intensity of the characteristic peaks increases significantly, indicating the continuous generation of iodine species with a high degree of oxidation in the electrolyte.

[0067] After electrolyzing for 2 min according to the above electrolysis process, turn off the power supply, place 0.5 g of waste lithium iron phosphate powder in the system after the electrolysis reaction to obtain a lithium extraction reaction system. Stir the lithium extraction reaction system at a rotation speed of 400 rpm, sample every 5 s for UV-Vis spectral testing, and observe the changes in the characteristic peaks at 288 nm and 351 nm. The results are as Figure 2 shown in b of Figure 2 As can be seen from b of - , as the stirring time prolongs, the characteristic absorption peak intensities at 288 nm and 351 nm attributed to I3

[0068] Combined with Figure 2 As can be seen, the recyclable iodine redox-mediated lithium extraction reaction system of the present invention can achieve the regeneration cycle of the iodine redox system, and can achieve the generation and continuous supply of highly oxidized iodine species to continuously drive lithium leaching.

[0069] 1.2 Energy consumption analysis

[0070] The energy requirement of the iodine oxidation reaction (IOR) based on the present invention was verified by linear sweep voltammetry (LSV). In the test of IOR, a 2 cm × 1 cm carbon cloth was used as the working electrode, a carbon rod as the counter electrode, a saturated Ag / AgCl electrode as the reference electrode, and the electrolyte was 50 mL of a potassium iodide solution with a concentration of 0.5 mol / L. A Chenhua electrochemical workstation was used to test the current-potential curve to determine the operating potential of IOR; the energy requirement of the oxygen evolution reaction (OER) was used as a comparison. The test of OER was the same as that of IOR, except that the electrolyte was 50 mL of a potassium hydroxide solution with a concentration of 1 mol / L. The energy requirement test results are as Figure 3 shown. The operating potential of IOR is 0.28 V (vs. Ag / AgCl), and the operating potential of OER is 1.09 V (vs. Ag / AgCl). The operating potential of IOR is significantly lower than that of OER, indicating that the I3 - / I - system reaction has the advantage of low energy consumption compared with OER. Compared with the traditional zinc-air battery charging reaction for zinc production (OER for zinc production), the process of obtaining high-value-added zinc metal in the present invention has lower energy consumption.

[0071] 1.3 Lithium extraction efficiency and product characterization

[0072] The crystal phase of the product in the method for recycling waste lithium iron phosphate batteries mediated by iodine in Example 1 was tested. The test method included: during the lithium extraction process carried out according to the method of Example 1 for 3 h, sampling was performed at preset times, followed by filtration to obtain filter residues. The filter residues were dried to a constant weight, and the crystal phase structure was characterized using a Bruker D8 Advance X-ray diffractometer with a CuKα radiation source. The tube voltage was 40 kV and the tube current was 30 mA. The results are as Figure 4 shown. Based on Figure 4 It can be seen that as the reaction time extended, the characteristic peaks attributed to lithium iron phosphate gradually disappeared, and the characteristic diffraction peaks attributed to FePO4 appeared and their peak intensities gradually increased. Moreover, when the reaction was completed, the characteristic peaks in the XRD pattern were basically consistent with the standard FePO4 pattern, indicating that the method of the present invention can promote the complete conversion of lithium iron phosphate to FePO4.

[0073] The element content of the dried filter residues was tested using an Agilent 5800 ICP-OES spectrometer. The results are as Figure 5 shown. The results showed that compared with the waste lithium iron phosphate powder before delithiation, the lithium content in the filter residues after delithiation decreased significantly, only being 3 g / kg, and the delithiation rate was 93.0%. The calculation formula for the delithiation rate is (lithium content in lithium iron phosphate before delithiation - lithium content in the solid phase after delithiation) / lithium content in lithium iron phosphate before delithiation.

[0074] 1.4 Verification of Zinc Deposition

[0075] The zinc sheet in step 102 of Example 1 was replaced with a galvanized copper sheet of the same size, and lithium extraction was carried out according to the methods of steps one to three in Example 1, with the lithium extraction time being 0.5 h. The cathode was taken out and the zinc deposition morphology was observed under a scanning electron microscope. The results are as Figure 6 shown, where Figure 6 a shows the zinc morphology deposited on the surface of the above-mentioned galvanized copper sheet, and Figure 6 b shows the zinc deposition morphology on the surface of the galvanized copper sheet without the protection of the sodium alginate coating. According to Figure 6 It can be seen that the zinc morphology deposited on the cathode surface after lithium extraction in the present invention is uniform and dense. Compared with the galvanized copper sheet without the sodium alginate coating, the regularity of its morphology is significantly improved, indicating that the method of the present invention can simultaneously achieve high-uniformity zinc deposition.

[0076] The cathode with deposited zinc was used as the negative electrode, and a 1 mol / L KOH solution was used as the electrolyte. Hydrogen production discharge tests were carried out at a current density of 20 mA·cm -2 . The results are as Figure 7As shown, the experimental results show that the Coulombic efficiency of the uncoated electrode sheet is 78%, and that of the electrode sheet coated with sodium alginate coating is 92%. It shows that the method of the present invention can achieve the deposition of highly conductive zinc metal, and the coating of sodium alginate can effectively inhibit the loss of zinc caused by the spontaneous reaction between iodine and zinc during charging, significantly improving the Coulombic efficiency of the sample.

[0077] 1.5 Performance verification of high-value by-product catalyst (ELFP-Ni)

[0078] Taking the FePO4 obtained in Step 4 of Example 1 as the raw material, the ELFP-Ni catalyst was prepared, and the performance of the catalyst for catalytic oxygen evolution reaction (OER) was tested. The preparation method includes: dispersing 50 mg of the above-mentioned FePO4 in 10 mL of a NiSO4·7H2O solution with a concentration of 20 mg / mL, and performing ultrasonic oscillation treatment for 1 hour to fully react FePO4 with nickel ions, centrifuging to collect the solid phase, drying overnight at 60 °C, mixing the dried powder with acetylene black according to a mass ratio of 7:3, adding 960 μL of isopropanol and 40 μL of Nafion solution, stirring and mixing evenly to obtain catalyst ink, ultrasonically treating the catalyst ink for 1 hour to make it uniformly mixed, and uniformly dripping and coating it on the surface of carbon cloth to obtain a catalyst electrode, and drying the catalyst electrode at 60 °C to obtain a carbon cloth electrode loaded with the ELFP-Ni catalyst.

[0079] Using the carbon cloth electrode loaded with the ELFP-Ni catalyst as the working electrode, the counter electrode is a carbon rod, the reference electrode is Hg / HgO, and the electrolyte is 50 mL of a potassium hydroxide solution with a concentration of 1 mol / L. The OER reaction is carried out with a Chenhua electrochemical workstation, and the results are as Figure 8 shown. According to Figure 8 It can be seen that at a current density of 10 mA·cm -2 , the overpotential of the ELFP-Ni catalyst for catalyzing OER is only 250 mV, which is better than 290 mV of the industrially commonly used RuO2 catalyst, indicating that the ELFP-Ni catalyst has excellent catalytic performance in the OER reaction.

[0080] 1.6 Influence of zinc ion concentration and iodine ion concentration in the electrolyte on the kinetics of lithium extraction

[0081] LSV was used to test the influence of different zinc ion concentrations or different iodine ion concentrations on the kinetics of lithium extraction. The test method is the same as the IOR test method in 1.2, except that the electrolyte is 50 mL of a solution containing zinc sulfate and potassium iodide. When measuring the influence of different zinc ion concentrations, the concentration of potassium iodide in the electrolyte is 0.5 mol / L, and when measuring the influence of different iodine ion concentrations, the concentration of zinc sulfate in the electrolyte is 1 mol / L. The measurement results are as Figure 9 and Figure 10As shown, among which Figure 9 is the influence of different zinc ion concentrations on the kinetics of lithium extraction, Figure 10 is the influence of different iodide ion concentrations on the kinetics of lithium extraction. According to Figure 9 it can be seen that under different zinc ion concentrations, the LSV curves basically coincide, indicating that the zinc ion concentration has little effect on the kinetics of iodine oxidation. According to Figure 10 it can be seen that as the iodide ion concentration increases, the increasing rate of the LSV curve significantly increases, indicating that the rate of the iodine oxidation reaction significantly accelerates and the kinetics of lithium extraction accelerates.

[0082] Example 2

[0083] This example provides a method for recycling waste lithium iron phosphate batteries mediated by iodine. It is the same as Example 1, except that in step 301, the current density is 30 mA·cm -2 .

[0084] In this example, the de-lithiation rate is 69%.

[0085] Example 3

[0086] This example provides a method for recycling waste lithium iron phosphate batteries mediated by iodine. It is the same as Example 1, except that in step 301, the current density is 20 mA·cm -2 .

[0087] In this example, the de-lithiation rate is 45%.

[0088] Example 4

[0089] This example provides a method for recycling waste lithium iron phosphate batteries mediated by iodine. It is the same as Example 1, except that in step 301, the current density is 10 mA·cm -2 .

[0090] In this example, the de-lithiation rate is 23%.

[0091] Example 5

[0092] This example provides a method for recycling waste lithium iron phosphate batteries mediated by iodine. It is the same as Example 1, except that in step 301, the lithium extraction time is 2.5 h.

[0093] In this example, the de-lithiation rate is 77%.

[0094] Example 6

[0095] This example provides a method for recycling waste lithium iron phosphate batteries mediated by iodine. It is the same as Example 1, except that in step 301, the lithium extraction time is 2 h.

[0096] In this example, the de-lithiation rate is 62%.

[0097] Example 7

[0098] This example provides a method for recovering waste lithium iron phosphate batteries mediated by iodine. It is the same as Example 1, except that in step 301, the lithium extraction time is 1.5 h.

[0099] In this example, the delithiation rate is 46%.

[0100] Example 8

[0101] This example provides a method for recovering waste lithium iron phosphate batteries mediated by iodine. It is the same as Example 1, except that in step 301, the lithium extraction time is 1 h.

[0102] In this example, the delithiation rate is 31%.

[0103] Example 9

[0104] This example provides a system for recovering waste lithium iron phosphate batteries mediated by iodine, including an electrolytic cell, a metal electrode, and an inert material electrode for containing a solution of zinc ions and oxidizable iodine species and waste lithium iron phosphate batteries; wherein the solution of zinc ions and oxidizable iodine species is a solution containing zinc sulfate and potassium iodide, the metal electrode is a zinc sheet coated with sodium alginate, and the inert material electrode is carbon cloth.

[0105] The application method of the system for recovering waste lithium iron phosphate batteries mediated by iodine in this example is the same as that in Example 1.

Claims

1. A method for recycling waste lithium iron phosphate batteries mediated by iodine, characterized in that, Comprising: Using a metal electrode as the cathode, an inert material electrode as the anode, and a solution containing zinc ions and oxidizable iodine species as the electrolyte to construct a recyclable iodine redox-mediated lithium extraction reaction system.

2. The method for iodine-mediated recycling of waste lithium iron phosphate batteries according to claim 1, wherein, The metal electrode includes a copper electrode, a zinc electrode, or a porous metal electrode.

3. The method for iodine-mediated recycling of waste lithium iron phosphate batteries according to claim 1, wherein The inert material electrode includes carbon cloth or carbon felt.

4. The method for iodine-mediated recovery of waste lithium iron phosphate batteries according to claim 1, wherein In the solution containing zinc ions and oxidizable iodine species, the source of zinc ions includes zinc sulfate or zinc acetate, and the source of oxidizable iodine species includes sodium iodide or potassium iodide.

5. The method for iodine-mediated recycling of waste lithium iron phosphate batteries according to claim 4, wherein The solution containing zinc ions and oxidizable iodine species is a solution containing zinc sulfate and potassium iodide.

6. The method for iodine-mediated recovery of waste lithium iron phosphate batteries according to claim 1, wherein The metal electrode is a metal electrode coated with a sodium alginate coating.

7. The method for iodine-mediated recycling of waste lithium iron phosphate batteries according to claim 6, wherein The metal electrode coated with sodium alginate is obtained by placing an electrode sheet in an aqueous sodium alginate solution and subjecting it to electrodeposition; during the electrodeposition process, the current density is 10 - 40 mA·cm -2 , and the discharge time is 5 - 10 s.

8. The method for iodine-mediated recycling of waste lithium iron phosphate batteries according to claim 1, wherein In the solution containing zinc ions and oxidizable iodine species, the concentration of zinc ions is 0.1 - 1.5 mol / L, and the concentration of oxidizable iodine species is 0.1 - 0.5 mol / L.

9. A system for iodine-mediated recycling of waste lithium iron phosphate batteries, characterized in that, Including an electrolytic cell, a metal electrode, and an inert material electrode for containing the solution of zinc ions and oxidizable iodine species and the waste lithium iron phosphate battery.

10. Use of a system for iodine-mediated recovery of waste lithium iron phosphate batteries as described in claim 9, characterized in that, Including applications in lithium extraction and the preparation of metallic zinc.

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