Method for selectively recovering valuable metal through co-pyrolysis of diaphragm and retired ternary lithium battery positive electrode material
Through the method of co-pyrolyzing of ceramic separators and the positive electrode material of retired ternary lithium battery, the complex and serious metal separation problems in traditional lithium battery recycling are solved, and the efficient and selective recycling of valuable metals is achieved, and the process flow is simplified.
Patent Information
- Application Number
- CN202510325649.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-19
- Publication Date
- 2025-06-13
AI Technical Summary
In traditional lithium battery recycling processes, it is difficult to achieve accurate separation of metals such as Ni, Co, Mn, etc., resulting in complex recycling processes and serious losses of valuable metals.
The ceramic separator is used to co-pyrolyze with the positive electrode material of the retired ternary lithium battery. Reducing gas is generated at high temperature through the ceramic separator, Co3+ and Ni3+ are selectively reduced, and efficient recovery of Li, Ni, and Co is achieved through acid leaching reaction, while Mn is treated by selective leaching residue.
The selective separation of Mn metals from retired ternary lithium batteries is achieved, the process flow is shortened, the recovery rate and purity of valuable metals is improved, and energy consumption and pollution are reduced.
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Figure CN120138342A_ABST
Abstract
Description
Technical Field:
[0001] The present invention relates to the technical field of waste lithium-ion battery recycling, and particularly relates to a method for selectively recovering valuable metals by co-pyrolysis of a separator and a cathode material of a retired ternary lithium battery. Background Art:
[0002] Lithium batteries are widely used in many fields such as small electronic devices, electric vehicles, and energy storage systems due to their high energy density, low self-discharge rate, and long service life. In the past few years, the global installed capacity of lithium batteries has increased rapidly, and the large accumulation of retired lithium batteries will further expand the lithium battery recycling market. Recycling NCM batteries has great economic value.
[0003] Traditional pyrometallurgical recycling of lithium batteries can effectively recover valuable metals such as Ni and Co, but Li is easily lost, the overall purity and recovery rate are low, and the energy consumption is high and the pollution is serious. In contrast, the hydrometallurgical process can recover high-purity metals through acid leaching and complex separation steps, and the leaching rate can be increased by introducing a reducing agent. However, the hydrometallurgical process is complex in operation, the process is cumbersome, and the environmental pressure is relatively high. The pyro-hydrometallurgical combined process combines the advantages of both, reduces energy consumption, reduces pollution, and realizes efficient recovery of valuable metals. This process destroys the structure of the cathode material through reduction roasting, reduces the metal valence state, and simplifies the subsequent leaching steps. However, traditional reduction methods such as carbothermal reduction, aluminothermic reduction, and salt-assisted roasting have poor selectivity for transition metals during the treatment process, usually resulting in the mixed recovery of metals such as Ni, Co, and Mn, and it is difficult to achieve precise separation. Therefore, after leaching, it is necessary to separate valuable metals one by one, which not only makes the entire recycling process more complex, but also the complicated separation process is prone to the loss of some valuable metals. Summary of the Invention:
[0004] The present invention solves the problems existing in the prior art and provides a method for selectively recovering valuable metals by co-pyrolysis of a separator and a cathode material of a retired ternary lithium battery. The present invention uses a ceramic separator to pyrolyze the cathode material of a retired ternary lithium battery, aiming to provide a method for selectively separating Mn metal from a retired ternary lithium battery only by roasting. The ceramic separator is the only reducing agent. While efficiently recovering valuable metals, Mn can be separated from other valuable metals only by acid leaching, shortening the process flow, and at the same time realizing the self-reduction recycling process of lithium batteries.
[0005] The object of the present invention is to provide a method for selectively recovering valuable metals by co-pyrolysis of a separator and a cathode material of a retired ternary lithium battery, comprising the following steps:
[0006] S1. After discharging the retired ternary lithium battery in an NaCl solution, separate the ceramic separator and the cathode sheet, cut the obtained cathode sheet into pieces, place it in the organic solvent NMP, ultrasonicate at room temperature, separate the aluminum foil, wash and dry it to obtain the positive electrode material of the retired ternary lithium battery;
[0007] S2. Mix the dried positive electrode material of the retired ternary lithium battery with the crushed ceramic separator to obtain a mixed material;
[0008] S3. Place the mixed material in a crucible, under a nitrogen atmosphere, after the temperature of the tubular furnace is raised to a predetermined temperature, push the crucible into the heating zone for co-roasting to obtain a roasted product;
[0009] S4. Carry out an acid leaching reaction on the obtained roasted product and selectively leach out Li, Ni, and Co elements;
[0010] S5. After the leaching is completed, through solid-liquid separation, obtain a sulfate solution containing Li, Ni, and Co ions and a leaching residue containing only MnO 2 of.
[0011] The specific steps of solid-liquid separation are: vacuum filter the solid-liquid mixture obtained in step S3 in a Buchner funnel, and rinse it 3-4 times with a 2% nitric acid solution to obtain a leaching residue and a leaching solution.
[0012] Preferably, the specific steps of step S1 are: after discharging the retired ternary lithium battery in a 5% NaCl solution, manually disassemble and separate the ceramic separator and the cathode sheet, cut the obtained cathode sheet into small pieces of 2-3 cm, place it in the organic solvent NMP, ultrasonicate at room temperature for 2-4 min, separate the aluminum foil, wash and dry it to obtain the positive electrode material of the retired ternary lithium battery.
[0013] Preferably, the mass ratio of the ceramic separator to the positive electrode material of the retired ternary lithium battery in step S2 is 0.1-0.3:1. Further preferably, the mass ratio of the separator to the positive electrode material of the retired ternary lithium battery is 0.15:1.
[0014] Preferably, the positive electrode material of the retired ternary lithium battery in step S2 includes NCM111, NCM523, NCM622, NCM811, and the ceramic separator is an alumina-based separator loaded with PP / PE, where the proportion of the PP / PE material is about 60%.
[0015] Preferably, the conditions for co-roasting in step S3 are: roasting time 30-90 min, roasting temperature 600°C-750°C, and nitrogen gas flow rate 20-100 mL / min.
[0016] Further preferably, the conditions for co-roasting in step S3 are: roasting time 60 min, roasting temperature 600°C, and nitrogen gas flow rate 50 mL / min.
[0017] Preferably, in step S3, the tubular furnace is for constant-temperature sampling. The mixed materials in the tubular furnace are for constant-temperature sampling.
[0018] Preferably, in step S4, an acid leaching reaction is carried out using dilute sulfuric acid. The concentration of the dilute sulfuric acid is 1-2 mol / L, the acid leaching temperature is 80°C - 90°C, the acid leaching time is 50 - 70 min, and the liquid-solid ratio is 15 - 25 mL / g.
[0019] More preferably, in step S4, the concentration of the dilute sulfuric acid is 1-2 mol / L, the acid leaching temperature is 85°C, the acid leaching time is 60 min, and the liquid-solid ratio is 20 mL / g.
[0020] Compared with the prior art, the present invention has the following advantages: In the method proposed by the present invention, the separator is shredded and mixed with the cathode material of the retired ternary lithium battery, and then calcined in an N 2 atmosphere at 600°C to 750°C. During the co-calcination of the cathode material and the ceramic separator, the separator generates reducing gases, which reduce part of the Co 3+ , Ni 3+ to Co 2+ , Ni 2+ , while the generated reducing gases are not sufficient to reduce Mn 4+ to Mn 2+ . Therefore, selective reduction of valuable metals can be achieved under low-temperature calcination at 600°C to 750°C. In the cathode material of the ternary lithium battery after calcination, Ni mainly exists in the form of Ni 2+ , Co is partially transformed into Co 2+ , and Mn all exists in the form of Mn 4+ . Using the separator as a reducing agent at high temperature does not introduce reducing agents such as acids and alkalis, preventing the generation of corrosive gases; at the same time, it does not introduce high-value lithium battery components such as graphite, improving economic benefits. This process not only realizes the selective recovery of metal ions in the cathode material, shortens the entire recovery process, but also treats the separator, solving the problem of treating waste separators. After calcination and leaching treatment, the leaching rates of Li, Ni, and Co are all above 95%, while the leaching rate of Mn remains below 1%. Description of the drawings:
[0021] Figure 1 is the scanning electron microscope image of the raw material of the cathode material of the retired ternary lithium battery in Example 1 of the present invention and its calcination with the separator at 600°C;
[0022] Figure 2 is the X-ray photoelectron spectroscopy image of the raw material of the cathode material of the retired ternary lithium battery in Example 1 of the present invention and its calcination with the separator at 600°C;
[0023] Figure 3 It is the X-ray diffraction pattern of the acid-leaching residue in Example 1 of the present invention. Specific implementation manner:
[0024] The following examples are further illustrations of the present invention rather than limitations thereof.
[0025] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specified, the experimental materials and reagents in this article are all commercially available products commonly used in this technical field. The cathode materials of retired ternary lithium batteries proposed by the present invention include NCM111, NCM523, NCM622, and NCM811. In the following examples, preferably, the cathode material of the retired ternary lithium battery is NCM523.
[0026] Example 1
[0027] A method for co-pyrolyzing a separator and a cathode material of a retired ternary lithium battery to selectively recover valuable metals, specifically including the following steps:
[0028] S1. After discharging the retired ternary lithium battery in 5% NaCl solution, manually separate the ceramic separator and the cathode sheet, cut the obtained cathode sheet into pieces of 2-3 mm, place it in the organic solvent NMP, ultrasonically treat it at room temperature for 3 min to separate the aluminum foil, rinse it with deionized water 3-4 times, and place it in a blast drying oven at 105 °C for drying for 6 h to obtain the cathode material of the retired ternary lithium battery.
[0029] S2. Cut the ceramic separator loaded with PP / PE into small pieces of about 3 mm * 3 mm, and place it in a closed container with the cathode material of the retired ternary lithium battery at a mass ratio of 15 wt.%, and transfer it to a quartz crucible after simple shaking and mixing. The ceramic separator is an alumina-based separator loaded with PP / PE, and the proportion of PP / PE material is about 60%.
[0030] S3. Pass N into the tubular furnace 2 Maintain for 20 min until the air is fully discharged. After the temperature of the tubular furnace rises to 600 °C, adjust the N 2 flow rate to 50 mL / min, place the quartz crucible containing the mixed material in the tubular furnace for roasting for 60 min, take out the crucible after the tubular furnace cools to room temperature, and obtain the roasted product.
[0031] S4. After grinding the obtained roasted product for 10 min, place it in 1 mol / L dilute sulfuric acid, with a liquid-solid ratio of 20 mL / g, and carry out an acid-leaching reaction at a temperature of 85 °C for 60 min.
[0032] S5. The solid-liquid mixture obtained after leaching is vacuum filtered in a Buchner funnel and rinsed 3 times with a 2% nitric acid solution to obtain leaching residues and leachate. Finally, the leaching rates of Li, Ni, and Co elements are 95.63%, 99.93%, and 99.52% respectively, and Mn is not leached at all, showing a very high selectivity effect of co-calcination of the separator and ternary material.
[0033] Figure 1 Figure 4 is the scanning electron microscope images of the original and calcined samples in Example 1. Among them, Figure 1 a in Figure 4 is the morphology of the cathode material of the retired ternary lithium battery without treatment, and b is the morphology after calcination of the separator and the cathode material. It can be observed that the surface of the cathode material presents a square or cubic structure, the surface is smooth, and the gap between particles is small. After calcination, the shape of the particles becomes irregular, and obvious surface roughness and pores appear. These changes indicate that the reducing gas released by the separator at high temperature reacts with the cathode material, resulting in a significant change in the surface structure of the cathode material.
[0034] Figure 2 Figure 5 is the X-ray photoelectron spectroscopy images of the original and calcined samples in Example 1. In the original sample, Ni element mainly exists in the form of Ni 3+ , accounting for 66.96%. After calcination with the separator, Ni mainly exists in the form of Ni 2+ , accounting for 70.51%; the valence states of Co in the original sample are all Co 3+ . After calcination with the separator, a part of Co is reduced. Among them, Co 2+ accounts for 31.66%, and Co 3+ accounts for 69.34%; the valence states of Mn do not change significantly before and after calcination. These results further verify that co-calcination of the separator and the cathode material of the retired ternary lithium battery helps to promote the selective recovery of valuable metals.
[0035] Figure 3 Figure 6 is the X-ray diffraction pattern of the acid leaching residue of Example 1. It can be found that only MnO 2 exists in the residue after leaching.
[0036] Comparative Example 1
[0037] This comparative example is the comparative example of Example 1, and its specific steps are as follows:
[0038] S1. After discharging the retired ternary lithium battery in 5% NaCl solution, manually separate the ceramic separator and the cathode sheet, cut the obtained cathode sheet into pieces of 2-3 mm, place it in the organic solvent NMP, ultrasonically treat it at room temperature for 3 min to separate the aluminum foil, rinse it with deionized water 3-4 times, and place it in a blast drying oven at 105 °C for drying for 6 h to obtain the positive electrode material of the retired ternary lithium battery. Transfer the positive electrode material of the retired ternary lithium battery to a quartz crucible.
[0039] S2. Pass N 2 into the tubular furnace and maintain it for 20 min until the air is fully exhausted. After the temperature of the tubular furnace rises to 600 °C, adjust the flow rate of N 2 to 50 mL / min, place the quartz crucible carrying the positive electrode material of the retired ternary lithium battery in the tubular furnace for roasting for 60 min. After the tubular furnace cools to room temperature, take out the crucible to obtain the roasted positive electrode material.
[0040] S3. After grinding the obtained roasted product for 10 min, place it in 1 mol / L dilute sulfuric acid, with a liquid-solid ratio of 20 mL / g, and perform acid leaching at a leaching temperature of 85 °C for 60 min.
[0041] S4. The solid-liquid mixture obtained after leaching is vacuum filtered in a Buchner funnel and rinsed 3 times with 2% nitric acid solution to obtain the leaching residue and the leaching solution. Finally, the leaching rates of Li, Ni, Co, and Mn elements are 66.60%, 32.88%, 34.75%, and 28.14% respectively.
[0042] Comparative Example 2
[0043] This comparative example is the comparative example of Example 1, using the same experimental materials, and the specific process is as follows:
[0044] S1. After discharging the retired ternary lithium battery in 5% NaCl solution, manually separate the ceramic separator and the cathode sheet, cut the obtained cathode sheet into pieces of 2-3 mm, place it in the organic solvent NMP, ultrasonically treat it at room temperature for 3 min to separate the aluminum foil, rinse it with deionized water 3-4 times, and place it in a blast drying oven at 105 °C for drying for 6 h to obtain the positive electrode material of the retired ternary lithium battery;
[0045] S2. Cut the ceramic separator loaded with PP / PE into small pieces of about 3 mm * 3 mm, and place it in a closed container with the positive electrode material of the retired ternary lithium battery at a mass ratio of 15 wt.% for simple shaking and mixing, and then transfer it to a quartz crucible.
[0046] S3. Pass N 2 into the tubular furnace and maintain it for 20 min until the air is fully exhausted. After the temperature of the tubular furnace rises to 500 °C, adjust the flow rate of N 2Adjust the flow rate to 50 mL / min, place the quartz crucible containing the mixed material in a tube furnace and calcine for 60 min. After the tube furnace cools to room temperature, take out the crucible to obtain the calcined product.
[0047] S4. After grinding the obtained calcined product for 10 min, place it in 1 mol / L dilute sulfuric acid with a liquid-solid ratio of 20 mL / g, and perform acid leaching for 60 min at a leaching temperature of 85 °C.
[0048] S5. The solid-liquid mixture obtained after leaching is vacuum filtered in a Buchner funnel and rinsed 3 times with 2% nitric acid solution to obtain the leaching residue and leaching solution. Finally, the leaching rates of Li, Ni, Co, and Mn elements are 94.01%, 59.88%, 54.59%, and 14.70% respectively.
[0049] Example 2
[0050] Same as Example 1, except that after the temperature of the tube furnace rises to 750 °C, N 2 Adjust the flow rate to 50 mL / min, place the quartz crucible containing the mixed material in a tube furnace and calcine for 60 min. After the tube furnace cools to room temperature, take out the crucible to obtain the calcined product. Finally, the leaching rate of Li element is 94.63%, Ni and Co elements are completely leached, while Mn cannot be leached at all and is completely separated from Li, Co, and Ni elements.
[0051] By comparing Example 1, Example 2, and Comparative Examples 1-2, using a ceramic diaphragm as a reducing agent to calcine with the cathode material can significantly improve the leaching efficiency and selectivity of valuable metals. In addition, with the increase of the calcination temperature, the selectivity of valuable metals is further improved until the leaching efficiency and selectivity no longer increase significantly at 750 °C, indicating that this method has obvious advantages in selectively recovering metals and improving metal recovery efficiency. This technology not only realizes the efficient selective recovery of valuable metals, but also realizes the reuse of lithium battery diaphragms, which has practical significance.
[0052] Comparative Example 3
[0053] Same as Example 1, except that the diaphragm is a PP / PE composite diaphragm, and the same mass ratio of reactants is used, that is, 9 wt.% PP / PE diaphragm.
[0054] Finally, the leaching rates of Li, Ni, Co, and Mn elements are 92.31%, 86.25%, 84.69%, and 7.84% respectively.
[0055] Comparing Example 1 with Comparative Example 3, Example 1 uses a ceramic diaphragm, and the metal leaching rate and selectivity for Mn are significantly higher than those of Comparative Example 3.
[0056] Example 3
[0057] A method for selectively recovering valuable metals by co-pyrolysis of a separator and the cathode material of a retired ternary lithium battery, specifically including the following steps:
[0058] S1. After discharging the retired ternary lithium battery in a 5% NaCl solution, manually separate the ceramic separator and the cathode sheet, cut the obtained cathode sheet into pieces of 2-3 mm, place it in the organic solvent NMP, ultrasonically treat it at room temperature for 3 min to separate the aluminum foil, rinse it with deionized water 3-4 times, and place it in a blast drying oven at 105 °C for drying for 6 h to obtain the cathode material of the retired ternary lithium battery.
[0059] S2. Cut the ceramic separator loaded with PP / PE into small pieces of about 3 mm * 3 mm, and place it in a sealed container with the cathode material of the retired ternary lithium battery at a mass ratio of 15 wt.%, and transfer it to a quartz crucible after simple shaking and mixing. The ceramic separator is an alumina-based separator loaded with PP / PE, and the proportion of the PP / PE material is about 60%.
[0060] S3. Pass N 2 into the tubular furnace and maintain it for 20 min until the air is fully discharged. After the temperature of the tubular furnace rises to 600 °C, adjust the flow rate of N 2 to 50 mL / min, place the quartz crucible containing the mixed material in the tubular furnace for roasting for 60 min, take out the crucible after the tubular furnace cools to room temperature to obtain the roasted product.
[0061] S4. Grind the obtained roasted product for 10 min, place it in 1.5 mol / L dilute sulfuric acid, with a liquid-solid ratio of 20 mL / g, and perform acid leaching for 60 min at a leaching temperature of 85 °C.
[0062] S5. Vacuum filter the solid-liquid mixture obtained after leaching in a Buchner funnel, and rinse it 3 times with a 2% nitric acid solution to obtain the leaching residue and the leaching solution. Finally, the leaching rate of Li element is 96.82%, the Ni and Co elements are completely leached, and the leaching rate of Mn remains at a very low level, only 0.38%.
[0063] Example 4
[0064] A method for selectively recovering valuable metals by co-pyrolysis of a separator and the cathode material of a retired ternary lithium battery, specifically including the following steps:
[0065] S1. After discharging the retired ternary lithium battery in a 5% NaCl solution, manually separate the ceramic separator and the cathode sheet, cut the obtained cathode sheet into pieces of 2-3 mm, place it in the organic solvent NMP, ultrasonically treat it at room temperature for 3 min to separate the aluminum foil, rinse it with deionized water 3-4 times, and place it in a blast drying oven at 105 °C for drying for 6 h to obtain the cathode material of the retired ternary lithium battery.
[0066] S2. Cut the ceramic separator loaded with PP / PE into small pieces of about 3 mm * 3 mm, and place them in a closed container with the cathode material of the retired ternary lithium battery at a mass ratio of 15 wt.%. After simple shaking and mixing, transfer them to a quartz crucible. The ceramic separator is an alumina-based separator loaded with PP / PE, and the proportion of PP / PE material is about 60%.
[0067] S3. Pass N 2 into the tubular furnace and maintain it for 20 min until the air is fully exhausted. After the temperature of the tubular furnace rises to 600 °C, adjust the N 2 flow rate to 50 mL / min, place the quartz crucible containing the mixed materials in the tubular furnace and calcine for 60 min. After the tubular furnace cools to room temperature, take out the crucible to obtain the calcined product.
[0068] S4. Grind the obtained calcined product for 10 min, then place it in 2 mol / L dilute sulfuric acid with a liquid-solid ratio of 20 mL / g, and perform acid leaching for 60 min at an acid leaching temperature of 85 °C.
[0069] S5. Vacuum filter the solid-liquid mixture obtained after leaching in a Buchner funnel, and rinse it 3 times with 2% nitric acid solution to obtain the leaching residue and leaching solution. Finally, the leaching rate of Li element is 99.32%, the Ni and Co elements are completely leached, and the leaching rate of Mn is 1.01%.
[0070] Example 5
[0071] Same as Example 1, except that: in step S2, the mass ratio of the ceramic separator to the cathode material of the retired ternary lithium battery is 0.1:1; in step S3, the co-calcination conditions are: calcination time 30 min, calcination temperature 750 °C, and nitrogen flow rate 20 mL / min; in step S4, use dilute sulfuric acid for acid leaching reaction, the concentration of dilute sulfuric acid is 1 mol / L, the acid leaching temperature is 80 °C, the acid leaching time is 70 min, and the liquid-solid ratio is 25 mL / g.
[0072] Example 6
[0073] Same as Example 1, except that: in step S2, the mass ratio of the ceramic separator to the cathode material of the retired ternary lithium battery is 0.3:1; in step S3, the co-calcination conditions are: calcination time 90 min, calcination temperature 600 °C, and nitrogen flow rate 100 mL / min; in step S4, use dilute sulfuric acid for acid leaching reaction, the concentration of dilute sulfuric acid is 2 mol / L, the acid leaching temperature is 90 °C, the acid leaching time is 50 min, and the liquid-solid ratio is 15 mL / g.
[0074] The description of the above embodiments is only used to help understand the technical solution and its core idea of the present invention. It should be noted that for those skilled in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.
Claims
1. A method for selectively recovering valuable metals by co-pyrolysis of a separator and a retired ternary lithium battery positive electrode material, characterized in that: The following steps are involved: S1. After discharging the retired ternary lithium battery in a NaCl solution, the ceramic diaphragm and the cathode sheet are separated, and the obtained cathode sheet is cut into pieces, placed in an organic solvent NMP, ultrasonicated at room temperature, and the aluminum foil is separated, washed and dried to obtain the retired ternary lithium battery positive electrode material; S2, mixing the dried retired ternary lithium battery positive electrode material with the broken ceramic separator to obtain a mixed material; S3, placing the mixed material in a crucible, and in a nitrogen atmosphere, after the temperature of the tube furnace is raised to a predetermined temperature, pushing the crucible into a heating zone for co-baking to obtain a calcined product; S4, subjecting the obtained roasted product to an acid leaching reaction, and selectively leaching Li, Ni and Co elements; S5. After leaching is completed, a sulfate solution containing Li, Ni and Co ions and a leaching residue containing only MnO2 are obtained by solid-liquid separation.
2. The method according to claim 1, characterized in that The specific steps of step S1 are: after discharging the retired ternary lithium battery in a 5% NaCl solution, manually disassemble and separate the ceramic diaphragm and the cathode sheet, and cut the obtained cathode sheet into small pieces of 2-3 cm, place it in an organic solvent NMP, and ultrasonicate it at room temperature for 2-4 minutes. After separating the aluminum foil, wash and dry it to obtain the retired ternary lithium battery positive electrode material.
3. The method according to claim 1 or 2, characterized in that: The mass ratio of the ceramic diaphragm described in step S2 to the retired ternary lithium battery positive electrode material is 0.1-0.3:
1.
4. The method according to claim 1, characterized in that The retired ternary lithium battery positive electrode materials described in step S2 include NCM111, NCM523, NCM622, and NCM811.
5. The method according to claim 1 or 4, characterized in that: The ceramic diaphragm described in step S2 is an alumina-based diaphragm loaded with PP / PE.
6. The method according to claim 1, characterized in that The co-calcination conditions in step S3 are: calcination time 30-90 min, calcination temperature 600° C.-750° C., and nitrogen flow rate 20-100 mL / min.
7. The method according to claim 1, characterized in that In step S3, the tube furnace is used for constant temperature sample injection.
8. The method according to claim 1, characterized in that In step S4, dilute sulfuric acid is used for acid leaching reaction, the concentration of the dilute sulfuric acid is 1-2 mol / L, the acid leaching temperature is 80°C-90°C, the acid leaching time is 50-70 min, and the liquid-to-solid ratio is 15-25 mL / g.
9. The method according to claim 8, characterized in that In step S4, the concentration of dilute sulfuric acid is 1-2 mol / L, the acid leaching temperature is 85° C., the acid leaching time is 60 min, and the liquid-to-solid ratio is 20 mL / g.