Recovery and regeneration method of iron-based fluorophosphate positive electrode material

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a recycling method of an iron-based fluorophosphate positive electrode material, which comprises the following steps: obtaining a waste positive plate using the iron-based fluorophosphate positive electrode material; baking the waste positive plate, stripping a positive electrode material from the waste positive plate, and preparing into recycled positive electrode powder; preparing a repairing reagent B by taking the proportion of each element in the newly prepared material as a standard, and mixing the recycled positive electrode powder with the optimizing reagent A and the repairing reagent B to obtain precursor slurry of which the proportion of each element is matched with the proportion of each element in the newly prepared material; the precursor slurry is taken, sanded and dried, and precursor powder is obtained; and sintering the precursor powder in a protective atmosphere at the sintering temperature of 500-700 DEG C to obtain a regenerated material of the iron-based fluorophosphate positive electrode material, the optimizing reagent A is an acid solution with reducibility. The scheme takes the recycled positive electrode powder as a reaction starting point, repairs and optimizes the microstructure of the waste positive electrode material to regenerate the performance, and is energy-saving and environment-friendly.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and particularly relates to a method for recycling and regenerating an iron-based fluorophosphate cathode material. Background Art

[0002] Iron-based fluorophosphate, abbreviated as NMFPF, is a material for sodium-ion batteries, and its structural general formula is Na2M x Fe y PO4F (M is selected from elements such as Ni, Co, Mn, Cu, Ca, Mg, Ti, Cr, V, etc.). Existing research shows that carbon coating and particle size control can optimize the microstructure and electrochemical performance of electrode materials, which is intuitively manifested as better rate performance and longer cycle life. In a previous patent of the applicant, a modified iron-based fluorophosphate cathode material and its preparation method were proposed. In this patent, divalent cations were doped into Na2FePO4F to convert Na1 without electrochemical activity into Na3 with electrochemical activity, thereby obtaining a cathode material with a structural general formula of Na2M x Fe 1-x PO4F. The cathode of this material shows good performance in specific capacity, rate performance, and cycling performance.

[0003] For electrode materials with good commercial prospects, the issue of their recycling and treatment after the end of the battery life cycle should also be considered. If the effective regeneration of the electrode sheet can be achieved after the battery is scrapped, not only can the excellent performance of the original material be retained, but also the energy and resource inputs required for manufacturing new electrodes can be significantly reduced. Summary of the Invention

[0004] In view of this, the present invention hopes to propose a method for recycling and regenerating an iron-based fluorophosphate cathode material, which can obtain an electrode material with performance close to or even consistent with that of newly prepared materials while reducing the preparation cost.

[0005] The present invention is achieved through the following technical solutions:

[0006] A method for recycling and regenerating an iron-based fluorophosphate cathode material, characterized by comprising the following steps:

[0007] S1. Obtain a waste cathode sheet using an iron-based fluorophosphate cathode material;

[0008] S2. Bake the waste cathode sheet, strip the cathode material from the waste cathode sheet, and make it into recycled cathode powder;

[0009] S3. Taking the element ratios in the newly prepared material as a standard, prepare a repair reagent B, mix the recycled cathode powder with an optimization reagent A and the repair reagent B to obtain a precursor slurry with element ratios matching those in the newly prepared material;

[0010] S4. Grind the precursor slurry and then dry it to obtain precursor powder;

[0011] S5. Sinter the precursor powder in a protective atmosphere at a sintering temperature of 500 - 700 °C to obtain the recycled material of the iron-based fluorophosphate cathode material;

[0012] The optimization reagent A is a reducing acidic solution.

[0013] When the cathode material is used in the initial preparation, it is called "newly prepared material", and the newly prepared material has an ideal element ratio. As the sodium-ion battery undergoes charge and discharge cycles, the structure of the cathode material gradually deteriorates or ages, and the element ratio in the cathode material of the discarded cathode sheet usually deviates from that in the newly prepared material. This solution takes the recycled cathode powder as the reaction starting point, uses the newly prepared material as the element ratio standard, uses the repair reagent B to repair the element composition of the discarded cathode material, and uses the optimization reagent A to provide an acidic environment to promote the combination of the repair reagent B and the discarded cathode material without heating, while providing a reducing environment to stabilize the valence state of Fe 2+ and improve the microscopic morphology of the recycled cathode material, ultimately optimizing the electrochemical performance of the recycled cathode material.

[0014] Preferably, the structural general formula of the newly prepared material is Na2M x Fe y PO4F, where x + y = 1, and y > 0, x > 0, and M is selected from one of the elements Ni, Co, Mn, Cu, Ca, Mg, Ti, Cr, V; correspondingly, the element ratio of the precursor slurry in S3 is Na:(Fe + M):P:F (mol) = 2:1:1:1.

[0015] Preferably, the optimization reagent A is a solution of a reducing organic acid.

[0016] Preferably, the reducing organic acid is selected from at least one of oxalic acid, acetic acid, ascorbic acid, and citric acid.

[0017] Preferably, the ratio of the optimization reagent A to the recycled cathode powder is (3 - 5) L:1 kg.

[0018] The optimization reagent A is a reducing acidic solution. In this solution, the components of the optimization reagent A are further designed, and reducing organic acids such as oxalic acid, acetic acid, ascorbic acid, and citric acid are used as the components of the optimization reagent A. Compared with the mixed solution prepared from a reducing substance and an acidic substance, the reducing organic acid can have both reducing and acidic functions in a single component, and can also form a carbon-coated structure after sintering, reducing the introduction of impurity phases and improving the cycle performance of the electrode material.

[0019] Preferably, in S2, the baking temperature is 300-500 °C. At this temperature, the cathode material on the original cathode sheet can be fully peeled off from the current collector and the binder, and the microscopic framework structure of the cathode material will not be damaged.

[0020] Preferably, the components of the repair reagent B include at least one of a sodium source, an M element donor reagent, an iron source, a phosphate donor reagent, and a fluorine source; the sodium source is selected from at least one of sodium fluoride, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, and sodium oxalate; the M element donor reagent is a metal oxide of M, and M is selected from one of Ni, Co, Mn, Cu, Ca, Mg, Ti, Cr, and V; the iron source is selected from at least one of iron(III) oxide, iron phosphate, and iron oxalate; the phosphate donor reagent is selected from at least one of phosphoric acid, ammonium dihydrogen phosphate, ammonium hydrogen phosphate, sodium dihydrogen phosphate, sodium hydrogen phosphate, and iron phosphate; the fluorine source is selected from at least one of sodium fluoride and ammonium fluoride.

[0021] Preferably, when the repair reagent B includes the iron source, it also includes a reducing carbon source. The feeding dosage of the reducing carbon source is calculated according to the reaction dosage required for all Fe 3+ to be completely reduced to Fe 2+

[0022] The storage conditions of ferrous salt reagents are relatively strict, and they are prone to absorbing water to form hydrates with uncertain general formulas, and the dosage is not easy to accurately calculate. Since the optimized reagent A provides a reducing environment, more stable ferric iron is used as the iron source in the repair reagent B, and the conversion from Fe 3+ to Fe 2+ is completed in the recycling and regeneration step. In order to further improve the fineness of the reaction, a reducing carbon source is added separately in the repair reagent B to adjust the valence state of the Fe element. In the sintering step, the reducing carbon source can reduce ferric iron to ferrous iron and remove trace oxygen in the sintering atmosphere at the same time, improving the sintering effect.

[0023] Preferably, in S4, the particle size of the sanded slurry is 0.1 μm ≤ D50 ≤ 1 μm.

[0024] Preferably, in S4, the drying method is spray drying.

[0025] Spray drying can directly convert the sanded precursor slurry into precursor powder with uniform particles, controllable particle size, and good dispersibility, and form a delicate spherical particle morphology when entering the subsequent sintering process.

[0026] The technical effects of the present invention include:

[0027] ​1. Compared with the chemical extraction methods in the prior art, in the present invention, in S2, the binder and current collector on the surface of the cathode material are peeled off by baking. During the baking process, the frame form of the recycled material does not come into contact with chemical reagents, reducing the incorporation of impurity phases; the obtained product is in a dry form and can directly enter the next step after powdering, omitting the drying step.

[0028] 2. In the prior art, the element deficiency and structural defects in the recycled sodium battery cathode sheets are repaired by hydrothermal reaction or solid-phase reaction. The hydrothermal reaction needs to react at 150 - 180 °C for more than 12 hours, and the solid-phase reaction needs to be heated in an environment of 750 °C for more than 4 hours. The present invention uses the optimized reagent A with acidity and reducibility as the repair environment for the recycled material, which has multiple beneficial effects. First, the optimized reagent A has a shaping function; specifically, the optimized reagent A is a solution, making the mixture of the recycled cathode powder and reagent A in S3 naturally have a slurry form. This form can not only enable the materials to be fully mixed and contacted, but also smoothly connect with the subsequent sanding step, without the need to change the physical state for the process equipment, reducing the operation steps; Second, the optimized reagent A can provide a reducing environment to stabilize the Fe 2+ valence state; Third, the acidic environment provided by the optimized reagent A is conducive to the repair elements provided by the repair reagent B entering the structure of the recycled cathode material, and the reaction can occur without additional heating, saving energy; Fourth, the acidic environment provided by the optimized reagent A allows the M element donor reagent to be fed in the form of metal oxide rather than metal salt, reducing the introduction of impurity phases and also reducing the reaction raw material cost;

[0029] 3. Further, the present invention selects a reducing organic acid as the component of the optimized reagent A. Compared with the composite reagent prepared from a reducing agent and an acid, the advantages of the reducing organic acid include: First, the organic acid will be converted into a thin carbon coating structure during the sintering step, optimizing the microstructure and electrochemical performance of the electrode material; Second, in the slurry-state system, the organic acid may play a dispersant role, improving the homogeneity of the slurry and optimizing the morphology of the sintered electrode material; Third, the reducing organic acid material is easily available and easy to store, reducing the reaction threshold and being easy to promote. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the first charge-discharge curve of the recycled cathode materials obtained in Example 1 and Comparative Example 3;

[0031] Figure 2 is the SEM characterization diagram of the recycled cathode material obtained in Example 1;

[0032] Figure 3 is the SEM characterization diagram of the recycled cathode material obtained in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. In addition, the embodiments of the present invention described below generally only represent some of the embodiments of the present invention, rather than all of the embodiments. Therefore, all other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0034] Example 1

[0035] S1. Obtain waste positive electrode sheets, and the corresponding new material of the positive electrode sheets is Na2Fe 0.6 Mn 0.4 PO4F, and the element ratio of the new material is Na:Fe:Mn:P:F = 2:0.6:0.4:1:1;

[0036] S2. Bake the waste positive electrode sheets at 400 °C, strip to obtain flaky positive electrode materials, powder them and pass through a 200-mesh sieve to obtain 0.8 kg of recycled positive electrode powder;

[0037] S3. Use ICP (Inductively Coupled Plasma Spectrometer) to measure the contents of sodium, iron, manganese, phosphorus, and fluorine elements in the recycled positive electrode powder, and measure the content of ferric ions, and calculate the supplementary feeding amounts of sodium source, iron source, manganese source, phosphorus source, fluorine source, reducing carbon source, organic acid, and dispersant (the feeding mass range is 0.2% - 0.5% of the mass of the recycled powder);

[0038] S4. Take 500 g of the recycled positive electrode powder obtained in S2, supplement 3.957 g of sodium carbonate, 6.271 g of sodium fluoride, 7.097 g of iron phosphate, 0.665 g of manganese oxide, 0.777 g of reducing carbon source glucose monohydrate, and 1.5 g of dispersant polyethylene glycol (calculated at 0.3% in this example), mix them evenly and add them to 1.5 L of 0.03 mol / L oxalic acid solution to obtain a precursor slurry; the concentration of Na + in the precursor slurry is 3.095 mol / L, the concentration of Fe 2+ &Fe 3+ is 0.928 mol / L, the concentration of Mn 2+ is 0.619 mol / L, and the concentrations of F and P are 1.547 mol / L;

[0039] S5. Grind the precursor slurry obtained in S4 for 4 h to make the particle size after grinding satisfy 0.1 ≤ D50 ≤ 1 μm; add the ground slurry to a spray drying device, and set the inlet temperature of the spray drying to 220 °C and the outlet temperature to 110 °C;

[0040] S6. Take the dried powder obtained in S5 and sinter it at 550 °C for 15 h in an argon atmosphere to obtain the regenerated cathode material Na2Fe 0.6 Mn 0.4 PO4F.

[0041] In this example, 0.03 mol / L oxalic acid solution is selected as the optimization reagent A, and sodium carbonate, sodium fluoride, iron phosphate, manganese oxide, and glucose monohydrate are selected as the components of the repair reagent B. According to the general common technical knowledge of those skilled in the art, the optimization reagent A includes, but is not limited to, a mixture of a non-metallic reducing agent and a non-reducing organic acid, a mixture of a metallic reducing agent and a non-reducing inorganic acid, etc.

[0042] In this example, the operation sequence is to first quantitatively recover the cathode powder, then calculate the feeding amounts of the optimization reagent A and the repair reagent B, and finally mix the three to make the precursor slurry. In an alternative example, the operation sequence can be to first mix the optimization reagent A and the recovered cathode powder, then quantitatively calculate the feeding amount of the repair reagent B, and finally add the repair reagent B to make the precursor slurry.

[0043] Example 2

[0044] S1. Obtain a waste cathode sheet. The new material corresponding to the waste cathode sheet is Na2Fe 0.6 Mn 0.4 PO4F, and the element ratio of the new material is Na:Fe:Mn:P:F = 2:0.6:0.4:1:1;

[0045] S2. Bake the waste cathode sheet at 400 °C, peel off to obtain a flaky cathode material, powder it and pass it through a 200-mesh sieve to obtain 0.8 kg of recovered cathode powder;

[0046] S3. Use ICP (Inductively Coupled Plasma Spectrometer) to measure the contents of sodium, iron, manganese, phosphorus, and fluorine elements in the recovered material, and measure the content of ferric ions, and calculate the supplementary feeding amounts of sodium source, iron source, manganese source, phosphorus source, fluorine source, reducing carbon source, dispersant, and organic acid;

[0047] S4. Take 500 g of the recovered cathode powder obtained in S2, supplement 6.332 g of sodium carbonate, 3.583 g of sodium dihydrogen phosphate, 7.097 g of iron phosphate, 0.665 g of manganese oxide, 0.777 g of reducing carbon source glucose monohydrate, and 1.5 g of dispersant polyethylene glycol, mix well and add it to 1.5 L of 0.03 mol / L oxalic acid solution to obtain a precursor slurry; the concentration of Na + in the precursor slurry is 3.095 mol / L, the concentration of Fe 2+ &Fe 3+ is 0.928 mol / L, the concentration of Mn 2+The concentration of [substance] is 0.619 mol / L, and the concentrations of F and P are 1.547 mol / L;

[0048] S5. Grind the precursor slurry obtained in S4 for 4 h to make the particle size after grinding satisfy 0.1 ≤ D50 ≤ 1 μm; Add the ground slurry to a spray drying device, and set the inlet temperature of spray drying to 220 °C and the outlet temperature to 110 °C;

[0049] S6. Take the dried powder obtained in S5 and sinter it at 550 °C for 15 h in an argon atmosphere to obtain the regenerated cathode material Na2Fe 0.6 Mn 0.4 PO4F.

[0050] Example 3

[0051] The difference between this example and Example 1 is that the sintering temperature in S6 is 650 °C.

[0052] Example 4

[0053] The difference between this example and Example 1 is that the baking temperature in S2 is 300 °C.

[0054] Example 5

[0055] S1. Obtain waste cathode sheets, and the corresponding new material of the waste cathode sheets is Na2Fe 0.95 Cu 0.05 PO4, and the element ratio of the new material is Na:Fe:Cu:P:F = 2:0.95:0.05:1:1;

[0056] S2. Bake the waste cathode sheets at 400 °C, strip to obtain flaky cathode materials, powder them and pass through a 200-mesh sieve to obtain 0.6 kg of recycled cathode powder;

[0057] S3. Use ICP (Inductively Coupled Plasma Spectrometer) to measure the contents of sodium, iron, copper, phosphorus, and fluorine elements in the recycled material, and measure the content of ferric ions, and calculate the supplementary feeding amounts of sodium source, iron source, copper source, phosphorus source, fluorine source, reducing carbon source, dispersant, and organic acid;

[0058] S4. Take 500 g of the recycled cathode powder obtained in S2, supplement 3.307 g of sodium carbonate, 5.240 g of sodium fluoride, 4.786 g of iron phosphate, 0.649 g of copper oxide, 0.524 g of reducing carbon source glucose monohydrate, and 1.5 g of dispersant polyvinyl alcohol, mix well and add them to 1.5 L of 1 mol / L acetic acid solution to obtain a precursor slurry; The concentration of Na + in the precursor slurry is 3.084 mol / L, the concentration of Fe 2+ &Fe 3+ is 0.925 mol / L, the concentration of Cu 2+The concentration of Na is 0.617 mol / L, and the concentrations of F and P are 1.542 mol / L;

[0059] S5. Grind the precursor slurry obtained in S4 for 4 h to make the particle size after grinding satisfy 0.1 ≤ D50 ≤ 1 μm; Add the ground slurry to a spray drying device, and set the inlet temperature of spray drying to 220 °C and the outlet temperature to 110 °C;

[0060] S6. Take the dried powder obtained in S5 and sinter it at 550 °C for 15 h in an argon atmosphere to obtain the regenerated cathode material Na2Fe 0.95 Cu 0.05 PO4F.

[0061] Example 6

[0062] S1. Obtain a waste cathode sheet. The material of the newly prepared material corresponding to this waste cathode sheet is Na2Fe 0.95 Cu 0.05 PO4, and the element ratio of the newly prepared material is Na:Fe:Cu:P:F = 2:0.95:0.05:1:1;

[0063] S2. Bake the waste cathode sheet at 400 °C, strip it to obtain a flaky cathode material, powder it and pass it through a 200-mesh sieve to obtain 0.6 kg of recycled cathode powder;

[0064] S3. Use ICP (Inductively Coupled Plasma Spectrometer) to measure the contents of sodium, iron, copper, phosphorus, and fluorine elements in the recycled material, and measure the content of ferric ions, and calculate the supplementary feeding amounts of sodium source, iron source, copper source, phosphorus source, fluorine source, reducing carbon source, dispersant, and organic acid;

[0065] S4. Take 500 g of the recycled cathode powder obtained in S2, add 6.448 g of sodium carbonate, 0.374 g of sodium dihydrogen phosphate, 4.786 g of iron phosphate, 0.649 g of copper oxide, 0.524 g of reducing carbon source glucose monohydrate, and 1.5 g of dispersant polyvinyl alcohol, mix them evenly and add them to 1.5 L of 1 mol / L acetic acid solution to obtain a precursor slurry; The concentration of Na + in the precursor slurry is 3.084 mol / L, the concentration of Fe 2+ &Fe 3+ is 0.925 mol / L, the concentration of Cu 2+ is 0.617 mol / L, and the concentrations of F and P are 1.542 mol / L;

[0066] S5. Grind the precursor slurry obtained in S4 for 4 h to make the particle size after grinding satisfy 0.1 ≤ D50 ≤ 1 μm; Add the ground slurry to a spray drying device, and set the inlet temperature of spray drying to 220 °C and the outlet temperature to 110 °C;

[0067] S6. Take the dried powder obtained in S5 and sinter it at 550 °C for 15 h in an argon atmosphere to obtain the regenerated cathode material Na2Fe 0.95 Cu 0.05 PO4F.

[0068] Example 7

[0069] The difference between this example and Example 5 is that the sintering temperature in S6 is 650 °C.

[0070] Example 8

[0071] The difference between this example and Example 5 is that the baking temperature in S2 is 300 °C.

[0072] Comparative Example 1

[0073] The difference between Comparative Example 1 and Example 1 is that the 1.5 L of 0.03 mol / L oxalic acid solution used in S4 is changed to: 1.5 L of deionized water.

[0074] Comparative Example 2

[0075] The difference between Comparative Example 2 and Example 1 is that no reducing carbon source, glucose monohydrate, is added in S4.

[0076] Comparative Example 3

[0077] The difference between Comparative Example 3 and Example 1 is that the sanding and spray drying steps in S5 are changed to: drying the precursor slurry obtained in S4 and using a powder machine to make the precursor powder.

[0078] The electrochemical properties of the regenerated cathode materials obtained in Examples 1 - 8 and Comparative Examples 1 - 3 were tested, and the experimental results are shown in Table 1.

[0079] Table 1 Comparison of the electrochemical properties of the regenerated cathode materials obtained in Examples 1 - 8 and Comparative Examples 1 - 3

[0080] Example Capacity of 0.1C g-1 / mAh Retention rate after 50 cycles at 1C / % Example 1 101.93 95.58 Example 2 102.76 95.31 Example 3 99.01 94.36 Example 4 92.70 92.72 Example 5 102.76 97.63 Example 6 95.53 96.58 Example 7 93.53 96.32 Example 8 92.18 95.81 Comparative Example 1 85.78 90.64 Comparative Example 2 86.91 93.21 Comparative Example 3 42.56 89.98

[0081] The results of Examples 1 to 8 show that during actual feeding, there is a certain optional range for the specific material compositions of the optimized reagent A and the repair reagent B, and both show good performance within the optional range. From the comparison between Comparative Example 1 and Example 1, it can be seen that after adding the reducing organic acid, the 0.1C specific capacity / mAh g-1 of the obtained cathode material increased by 18.8% (calculation method: (101.93 - 85.78) / 85.78×100%), and the retention rate / % after 50 cycles at 1C was also optimized. From the comparison between Comparative Example 1, Comparative Example 2 and Example 1, it can be seen that when only using the optimized reagent A, the optimized reagent A can partially undertake the function of the reducing carbon source; after adding the optimized reagent A and the reducing carbon source at the same time, the performance of the cathode material is further improved. From the comparison between Comparative Example 3 and Example 1, it can be seen that the combination of sanding - spray drying significantly improved the 0.1C specific capacity / mAh g-1 of the corresponding cathode material.

[0082] Figure 1 Figure 4 is the first charge-discharge curve of the sodium-ion battery prepared from the newly prepared material and the recycled material obtained in Example 1. The performance of the material obtained in Example 1 is basically the same as that of the newly prepared material.

[0083] Figure 2 、 Figure 3 Figures 5 and 6 are the SEM morphologies of the recycled electrode materials obtained in Example 1 and Comparative Example 3, respectively. The particles of the material obtained in Example 1 are uniform in size and have a smaller particle size, while Comparative Example 3 contains more irregularly agglomerated large particles and has a poorer morphology.

Claims

1. A method for recycling and regenerating an iron-based fluorophosphate positive electrode material, characterized in that: The following steps are involved: S1. Obtaining a discarded positive electrode sheet using an iron-based fluorophosphate positive electrode material; S2, baking the waste positive electrode sheet, stripping the positive electrode material from the waste positive electrode sheet and preparing a recycled positive electrode powder; S3, preparing a repair reagent B based on the ratio of each element in the newly prepared material, mixing the recovered positive electrode powder with the optimized reagent A and the repair reagent B to obtain a precursor slurry in which the ratio of each element matches the ratio of each element in the newly prepared material; S4, grinding the precursor slurry and drying it to obtain a precursor powder; S5, sintering the precursor powder in a protective atmosphere at a sintering temperature of 500-700° C. to obtain a regenerated material of the iron-based fluorophosphate positive electrode material; The optimized reagent A is an acidic solution with reducing properties.

2. The recycling method according to claim 1, characterized in that: The general structural formula of the new material is Na2M x Fe y PO4F, wherein x+y=1, y>0, x>0, and M is selected from one of the elements Ni, Co, Mn, Cu, Ca, Mg, Ti, Cr, and V; accordingly, the element ratio of the precursor slurry in S3 is Na:(Fe+M):P:F(mol)=2:1:1:

1.

3. The recycling method according to claim 1, characterized in that: The optimized reagent A is a solution of a reducing organic acid.

4. The recycling method according to claim 3, characterized in that: The reducing organic acid is selected from at least one of oxalic acid, acetic acid, ascorbic acid and citric acid.

5. The recycling method according to claim 3, characterized in that: The ratio of the optimized reagent A to the recovered positive electrode powder is (3-5) liters: 1 kilogram.

6. The recycling method according to claim 1, characterized in that: In S2, the baking temperature is 300-500°C.

7. The recycling method according to claim 2, characterized in that: The components of the repair reagent B include at least one of a sodium source, an M element donor reagent, an iron source, a phosphate donor reagent and a fluorine source; the sodium source is selected from at least one of sodium fluoride, sodium carbonate, sodium bicarbonate, sodium dihydrogen phosphate, and sodium oxalate; the M element donor reagent is a metal oxide of M, and M is selected from one of Ni, Co, Mn, Cu, Ca, Mg, Ti, Cr, and V; the iron source is selected from at least one of ferric oxide, ferric phosphate, and ferric oxalate; the phosphate donor reagent is selected from at least one of phosphoric acid, ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, and ferric phosphate; the fluorine source is selected from at least one of sodium fluoride and ammonium fluoride.

8. The recycling method according to claim 7, characterized in that: When the repair reagent B includes the iron source, it also includes a reducing carbon source.

9. The recycling method according to claim 1, characterized in that: In S4, the particle size of the slurry after sand grinding is 0.1 μm≤D50≤1 μm.

10. The recycling method according to claim 1, characterized in that: In S4, the drying method is spray drying.

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