Method for synergistic leaching of retired lithium ion battery cathode material

Abstract

This invention discloses a method for the co-leaching of cathode materials from retired lithium-ion batteries, belonging to the field of resource recycling. Bio-acid and ferric iron solutions are prepared separately using *Thiobacillus ferrooxidans*. The bio-acid is used to selectively leach lithium from ternary cathode powder, obtaining a lithium-containing leachate and acid leaching residue. The ferric iron solution is then used to replace and leach lithium iron phosphate cathode powder, yielding a leachate containing lithium and ferrous iron. The acid leaching residue is mixed with the ferrous iron-containing leachate, and ferrous iron is used to reduce and leach nickel, cobalt, and manganese from the acid leaching residue. This invention achieves a lithium leaching rate greater than 96%, a combined nickel, cobalt, and manganese leaching rate close to 100%, and a lithium iron phosphate slurry concentration of up to 15%. Iron ions form an internal cycle within the system: ferric iron → ferrous iron → ferric iron, significantly reducing chemical reagent consumption and waste generation. It has advantages such as high leaching efficiency, high treatment concentration, short cycle time, low cost, and environmental friendliness, and is suitable for the efficient co-leaching of retired ternary and lithium iron phosphate cathode materials.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling and mainly relates to a method for the co-leaching of cathode materials from retired lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries, as core components of new energy vehicles, have now entered a phase of large-scale retirement and scrapping. Cathode materials are the most valuable component in lithium-ion batteries, mainly including lithium iron phosphate (LFP) and ternary lithium (NCM) types, containing key metals such as nickel, cobalt, and lithium. These metals are expensive and highly dependent on imports; their recycling is crucial for alleviating upstream resource supply pressure and ensuring the security of the industrial chain. However, retired lithium-ion batteries come from complex and diverse sources, and how to build a green and efficient recycling system to achieve efficient leaching of these key metals remains a key technical challenge.

[0003] Currently, the main methods for recycling lithium-ion battery cathode materials include pyrometallurgy and hydrometallurgy. Pyrometallurgy is energy-intensive, generates large amounts of carbon, and has limited metal recovery rates; while hydrometallurgy can efficiently leach valuable metals, it requires large amounts of strong acids, strong alkalis, oxidants, and reducing agents, which can easily cause secondary pollution and pose a high environmental risk. To address these issues, bioleaching technology has received widespread attention in recent years. This technology utilizes the metabolic activity of microorganisms to dissolve and leach metals, offering advantages such as low cost and environmental friendliness.

[0004] However, existing bioleaching technologies still face numerous challenges when applied to the recycling of cathode materials from lithium-ion batteries. First, during direct biological contact leaching, the toxicity of the metal components in the cathode black powder inhibits microbial activity, resulting in low slurry concentrations in the leaching system (typically only around 1% w / v), long leaching cycles (7-15 days), or the need for stress-resistance acclimation of the microbial strains (e.g., CN119464724B). Second, existing research largely focuses on the leaching of single-type cathode materials (lithium iron phosphate or ternary lithium), with limited exploration of synergistic leaching processes for multi-source black powders with complex origins and diverse types. These issues limit the large-scale application of bioleaching technology in the field of lithium battery recycling.

[0005] In the leaching study of lithium iron phosphate cathode materials, trivalent iron ions (Fe3+) are... 3+ It has been proven to play an important role. Existing patent documents (such as CN120728070B, CN117165770A, CN117163928A) disclose methods for leaching lithium iron phosphate using trivalent iron salts, the principle of which is Fe 3+ It undergoes a displacement reaction with LiFePO4, removing Li + and Fe 2+It is released into the solution. However, ferric salts (such as ferric sulfate) are expensive, increasing process costs. During the leaching process of ternary cathode materials, Fe... 2+ It can be used as a reducing agent to reduce the high-valence nickel, cobalt, and manganese oxides that are difficult to dissolve in acids to acid-soluble low-valence oxides, thereby promoting their leaching.

[0006] In the field of biometallurgy, *Acidithiobacillus ferrooxidans* (A. ferrooxidans) is a commonly used model strain. This bacterium is a Gram-negative, chemoautotrophic abiotic that can utilize reducing sulfur to produce bioacids and can also convert Fe... 2+ Oxidized to Fe 3+ Based on this metabolic characteristic, theoretically, the acidic medium and oxidant required for leaching can be prepared at low cost through microbial metabolic processes, and then combined with non-contact chemical leaching to construct a novel bio-chemical synergistic treatment process. However, how to organically combine the above-mentioned bio-metabolic characteristics with the chemical leaching behavior of different types of cathode materials to achieve stepwise synergistic treatment of two typical cathode materials, lithium iron phosphate and ternary lithium, and to construct an internal recycling mechanism for iron ions, has not yet been publicly reported.

[0007] In conclusion, developing a synergistic leaching method that can meet the requirements of high efficiency, low cost, and green environmental protection, and is applicable to cathode materials of multi-source retired lithium-ion batteries, has significant practical significance and industrialization value. Summary of the Invention

[0008] To address the aforementioned problems in the existing technology, this invention provides a method for the co-leaching of cathode materials from retired lithium-ion batteries.

[0009] The technical solution adopted in this invention is as follows:

[0010] A method for co-leaching of cathode materials from retired lithium-ion batteries includes the following steps:

[0011] S1. Using *Acidithiobacillus ferrooxidans*, bioacids and Fe-containing compounds were prepared respectively. 3+ The solution;

[0012] S2. The bio-acid obtained in step S1 is mixed with ternary cathode black powder and subjected to the first stage of leaching to separate lithium-containing leachate and ternary acid leaching residue.

[0013] S3, the Fe-containing sample obtained in step S1 3+ The solution is mixed with lithium iron phosphate cathode black powder to form a slurry, which is then subjected to a second leaching process to separate Fe-containing materials. 2+ and Li +The leachate;

[0014] S4. The tribasic acid leaching residue obtained in step S2 and the Fe-containing residue obtained in step S3 2+ The leachate is mixed and the third leaching stage is carried out to leach out nickel, cobalt and manganese.

[0015] Furthermore, in step S4, Fe is present. 2+ Fe in the leachate 2+ As a reducing agent, the high-valence nickel, cobalt, and manganese oxides in the ternary acid leaching residue obtained in step S2 are reduced to acid-soluble low-valence oxides, while Fe... 2+ Oxidized to Fe 3+ Fe 3+ Hydrolysis produces H + It also enables the acid leaching of nickel, cobalt, and manganese.

[0016] Further, in step S1, the preparation conditions of the bio-acid include: a sulfur mass fraction of 0.5–2.0% in the culture medium, a culture time of 6–10 days, a final pH of 0.8–1.2, and an acidity of 0.25–0.40 mol-H⁺. + / L. For example, the sulfur content is 1.0%, the culture time is 8 days, the pH is 1.0, and the acidity is 0.33 mol-H. + / L.

[0017] Furthermore, in step S1, Fe is present. 3+ The preparation conditions for the solution include: the culture medium contains Fe 2+ The source was supplemented with FeSO4·7H2O in a semi-continuous manner, and the culture time was 6-10 days. The endpoint was Fe 3+ The concentration is 40–60 g / L, and the pH is 1.5–2.0. For example, Fe... 3+ The concentration was 50 g / L, the incubation time was 8 days, and the pH was 1.8.

[0018] Furthermore, in step S2, during the first stage of leaching, the liquid-to-solid ratio of the bio-acid to the ternary cathode black powder is 50–100:1 ml / g, the reaction temperature is 25–35℃, the reaction time is 2–4 hours, and the reactor rotation speed is 250–350 rpm; the lithium leaching rate is 96–100%. For example, the liquid-to-solid ratio is 60 mL:1 g, the reaction temperature is 30℃, the reaction time is 3 hours, and the rotation speed is 300 rpm.

[0019] Further, in step S3, during the second leaching stage, the slurry concentration of lithium iron phosphate cathode black powder is 10-20%, and Fe... 3+The molar ratio of iron to lithium iron phosphate is 1:(0.9–1.1), the reaction time is 20–40 minutes, the reaction temperature is 25–35℃, and the reactor rotation speed is 250–350 rpm; the lithium leaching rate is 96–98%, and the Fe... 2+ The replacement rate is 95-98%.

[0020] Furthermore, in step S4, during the third leaching stage, the Fe-containing solution obtained in step S3... 2+ The mixing ratio of the leachate and the tribasic acid leaching residue obtained in step S2 is based on Fe 2+ The mass ratio of the initial ternary cathode black powder to the mass of the original ternary cathode black powder is (1.0-1.5):1. The reaction time is 50-120 minutes, the reaction temperature is 25-35℃, and the reactor rotation speed is 250-350 rpm. The comprehensive leaching rate of nickel, cobalt, and manganese is 95-100%.

[0021] Further, in step S4, during the third leaching stage, the final reaction pH is 2.0–2.5, and Fe… 2+ The residual concentration is 10–15 g / L, Fe 3+ The concentration of the product is 30–40 g / L.

[0022] The aforementioned reaction system for the co-leaching of cathode materials from decommissioned lithium-ion batteries includes: bio-acids produced by the metabolism of *A. ferrooxidans* and Fe-containing... 3+ The solution, composed of Fe 3+ The solution reacts with lithium iron phosphate cathode black powder to produce Fe-containing 2+ The leachate is a ternary acid leaching residue generated by the reaction of the bio-acid with ternary cathode black powder, wherein the Fe-containing... 2+ The leaching solution is mixed with the ternary acid leaching residue to form a reduction-acid leaching synergistic reaction system.

[0023] Furthermore, the valuable metals include at least one of lithium, nickel, cobalt, manganese, and iron.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] (1) In this invention, the lithium leaching rate of LFP and NCM cathode black powder can reach more than 96%, and the comprehensive leaching rate of NCM cathode black powder is close to 100%. The slurry concentration of LFP cathode black powder can reach 15% (w / v), and the slurry concentration of NCM cathode black powder can reach 4.5% (w / v), which is much higher than the approximately 1% of traditional biological leaching. The leaching time of the main process is shortened to several hours, overcoming the bottlenecks of long cycle and low concentration of traditional methods.

[0026] (2) This invention utilizes the metabolism of *Thiobacillus ferrooxidans* to prepare bioacids and high-concentration Fe. 3+The solution (e.g., 50 g / L) has low preparation cost of leaching reagents, and the consumption of chemicals such as strong acids and iron salts is significantly reduced; the non-contact leaching method avoids the toxic inhibition of microorganisms by black powder, and does not require strain domestication, making the process green and environmentally friendly.

[0027] (3) This invention constructs an internal circulation of iron elements to achieve synergistic leaching. Fe 3+ Oxidative leaching of lithium iron phosphate to produce Fe 2+ The latter is used to reduce the leaching residue from the ternary acid, where iron ions achieve "Fe" within the process. 3+ →Fe 2+ →Fe 3+ "Recycling reduces the addition of external iron salts and the generation of iron-containing waste residue, achieving synergistic processing and resource complementarity of the two cathode materials."

[0028] (4) The present invention designs a step-by-step leaching path based on the different chemical properties of lithium iron phosphate and ternary materials, which can effectively cope with the reality of complex sources and mixed types of retired lithium batteries, and provide a feasible technical solution for the efficient synergistic treatment of multi-source mixed cathode black powder. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the method of the present invention.

[0030] Figure 2 The image shows the XRD pattern of LFP cathode black powder.

[0031] Figure 3 The image shows the XRD pattern of NCM cathode black powder. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

[0033] Preparation and elemental analysis of LIBs cathode black powder:

[0034] The obtained retired lithium-ion batteries, including lithium iron phosphate batteries and ternary lithium batteries, were immersed in NaCl solution (5% w / v) and discharged for 24 h. After drying, the batteries were disassembled, and the positive and negative electrodes and separators were separated. The batteries were then air-dried in a fume hood for 48 h. The positive electrode sheets were cut into small pieces, ground into powder using a grinder, and then calcined in a muffle furnace at 200℃ for 1 h to remove organic matter. After the samples cooled, they were sieved through a 200-mesh sieve, and the product that passed through the sieve was the electrode black powder used in the experiment.

[0035] Analysis revealed the following main components and contents of the LFP cathode powder: Li 4.05%, Fe 32.63%, P 18.98%, and slurry pH 9.14.

[0036] The main components and contents of NCM cathode powder are: Li 7.43%, Ni 21.46%, Co 20.28%, Mn 18.14%, and slurry pH 11.11.

[0037] Figure 2 and Figure 3 The XRD patterns shown indicate that the crystal structure XRD patterns of LFP and NCM cathode black powders are similar to those of standard LiFePO4 and NCM111. Figure 1 The purity meets the experimental requirements.

[0038] Example 1

[0039] A method for co-leaching of cathode materials from retired lithium-ion batteries, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps:

[0040] S1. Using *Acidithiobacillus ferrooxidans*, bioacids and Fe-containing compounds were prepared respectively. 3+ The solution; the preparation conditions of the bioacid were: sulfur mass fraction in the culture medium of 1.0%, culture time of 8 days, culture endpoint pH of 1.0, and acidity of 0.33 mol-H. + / L; Contains Fe 3+ The preparation conditions for the solution are: the culture medium contains Fe 2+ The source was supplemented with FeSO4·7H2O in a semi-continuous manner, and the culture time was 8 days. The endpoint was Fe 3+ The concentration is 50 g / L, and the pH is 1.8.

[0041] S2. The bio-acid obtained in step S1 is mixed with ternary cathode black powder and subjected to the first stage of leaching. The liquid-solid ratio of bio-acid to ternary cathode black powder is 60:1 mL / g. The mixture is reacted in a constant temperature shaking shaker (300 rpm, 30℃) for 3 hours. The lithium-containing leaching solution and ternary acid leaching residue are separated, and the lithium leaching rate is 98.5%.

[0042] S3, the Fe-containing sample obtained in step S1 3+ The solution was mixed with lithium iron phosphate cathode black powder to form a slurry, which was then subjected to a second stage of leaching. The slurry concentration of lithium iron phosphate cathode black powder was 14%, and Fe... 3+ The iron content in lithium iron phosphate was 1:1. The mixture was reacted in a constant-temperature shaking table (300 rpm, 30°C) for 30 minutes to separate the Fe-containing compounds. 2+ and Li + The leaching solution showed a lithium leaching rate of 96.9% and an Fe leaching rate of 10%. 2+ The replacement rate was 96.2%.

[0043] S4, Nickel, Cobalt, and Manganese Leaching: The ternary acid leaching residue obtained in step S2 and the Fe-containing residue obtained in step S3 are leached together. 2+ The leachate is mixed and subjected to a third leaching process. The Fe-containing solution obtained in step S3 2+ The mixing ratio of the leachate and the tribasic acid leaching residue obtained in step S2 is based on Fe 2+ The mass ratio of Fe to the initial ternary cathode black powder was 1.1:1. The reaction was carried out in a constant-temperature shaking incubator (300 rpm, 30°C) for 60 minutes, with a final pH of 2.2. 2+ The residual concentration was 11.9 g / L, Fe 3+ The concentration was 35.8 g / L, and the overall leaching rate of nickel, cobalt, and manganese was 99.8%.

[0044] Example 2

[0045] A method for co-leaching of cathode materials from retired lithium-ion batteries includes the following steps:

[0046] S1. Using *Acidithiobacillus ferrooxidans*, bioacids and Fe-containing compounds were prepared respectively. 3+ The solution; the preparation conditions of the bioacid were: sulfur mass fraction in the culture medium of 2.0%, culture time of 6 days, culture endpoint pH of 0.8, and acidity of 0.25 mol-H. + / L; Contains Fe 3+ The preparation conditions for the solution are: the culture medium contains Fe 2+ The source was supplemented with FeSO4·7H2O in a semi-continuous manner, and the culture time was 6 days. The endpoint was Fe 3+ The concentration is 40 g / L, and the pH is 1.5.

[0047] S2. The bio-acid obtained in step S1 is mixed with ternary cathode black powder and subjected to the first stage of leaching. The liquid-solid ratio of bio-acid to ternary cathode black powder is 50:1 mL / g. The mixture is reacted in a constant temperature shaking shaker (250 rpm, 25℃) for 2 hours. The lithium-containing leachate and ternary acid leaching residue are separated, and the lithium leaching rate is 96.2%.

[0048] S3, the Fe-containing sample obtained in step S1 3+ The solution is mixed with lithium iron phosphate cathode black powder to form a slurry, which is then subjected to a second-stage leaching. The slurry concentration of lithium iron phosphate cathode black powder is 5%, and Fe... 3+ The molar ratio of iron in the compound to that in lithium iron phosphate was 1:0.9. The mixture was reacted in a constant-temperature shaking table (250 rpm, 25°C) for 20 minutes to separate the Fe-containing compound. 2+ and Li + The leaching solution showed a lithium leaching rate of 96.1% and an Fe leaching rate of 10%. 2+The replacement rate was 95.2%.

[0049] S4, Nickel, Cobalt, and Manganese Leaching: The ternary acid leaching residue obtained in step S2 and the Fe-containing residue obtained in step S3 are leached together. 2+ The leachate is mixed and subjected to a third leaching process. The Fe-containing solution obtained in step S3 2+ The mixing ratio of the leachate and the tribasic acid leaching residue obtained in step S2 is based on Fe 2+ The mass ratio of Fe to the initial ternary cathode black powder was 1.0:1. The reaction was carried out in a constant-temperature shaking incubator (250 rpm, 25°C) for 50 minutes, with a final pH of 2.0. 2+ The residual concentration was 10.0 g / L, Fe 3+ The concentration was 30.0 g / L, and the overall leaching rate of nickel, cobalt, and manganese was 95.3%.

[0050] Example 3

[0051] A method for co-leaching of cathode materials from retired lithium-ion batteries includes the following steps:

[0052] S1. Using *Acidithiobacillus ferrooxidans*, bioacids and Fe-containing compounds were prepared respectively. 3+ The solution; the preparation conditions of the bioacid were: sulfur mass fraction in the culture medium of 2.0%, culture time of 10 days, pH at the culture endpoint of 1.2, and acidity of 0.40 mol-H. + / L; Contains Fe 3+ The preparation conditions for the solution are: the culture medium contains Fe 2+ The source was supplemented with FeSO4·7H2O in a semi-continuous manner, and the culture time was 10 days. The endpoint was Fe 3+ The concentration is 60 g / L, and the pH is 2.0.

[0053] S2. The bio-acid obtained in step S1 is mixed with ternary cathode black powder and subjected to the first stage of leaching. The liquid-solid ratio of bio-acid to ternary cathode black powder is 100:1 mL / g. The mixture is reacted in a constant temperature shaking shaker (350 rpm, 35℃) for 4 hours. The lithium-containing leaching solution and ternary acid leaching residue are separated, and the lithium leaching rate is 99.8%.

[0054] S3, the Fe-containing sample obtained in step S1 3+ The solution is mixed with lithium iron phosphate cathode black powder to form a slurry, which is then subjected to a second stage of leaching. The slurry concentration of lithium iron phosphate cathode black powder is 15%, Fe 3+ The molar ratio of iron in the compound to that in lithium iron phosphate was 1:1.1. The mixture was reacted in a constant-temperature shaking table (350 rpm, 35°C) for 40 minutes to separate Fe-containing compounds. 2+ and Li+ The leaching solution showed a lithium leaching rate of 97.8% and an Fe leaching rate of 10%. 2+ The replacement rate was 97.9%.

[0055] S4, Nickel, Cobalt, and Manganese Leaching: The ternary acid leaching residue obtained in step S2 and the Fe-containing residue obtained in step S3 are leached together. 2+ The leachate is mixed and subjected to a third leaching process. The Fe-containing solution obtained in step S3 2+ The mixing ratio of the leachate and the tribasic acid leaching residue obtained in step S2 is based on Fe 2+ The mass ratio of Fe to the initial ternary cathode black powder was 1.5:1. The reaction was carried out in a constant-temperature shaking incubator (350 rpm, 35°C) for 120 minutes, with a final pH of 2.5. 2+ The residual concentration was 15.0 g / L, Fe 3+ The concentration was 40.0 g / L, and the overall leaching rate of nickel, cobalt, and manganese was 99.7%.

[0056] Comparative Example 1

[0057] Compared with Example 1, the remaining steps and parameters are exactly the same, except that the leaching conditions of the first stage of step S2 are changed: the liquid-solid ratio of bioacid to ternary cathode black powder is 20:1 mL / g, the reaction time is 1 hour, and the rotation speed is 200 rpm.

[0058] Experimental results show that the leaching rate of lithium is only 47.97%, while nickel, cobalt, and manganese cannot be effectively leached.

[0059] Comparative Example 2

[0060] Compared to Example 1, the remaining steps and parameters are exactly the same, except for the leaching conditions in the second stage of step S3, which are changed: Fe-containing 3+ The solution is not adjusted with sulfuric acid, and the initial pH is maintained at 1.8.

[0061] Experimental results show that the lithium leaching rate is 75.5%, and the Fe... 2+ The replacement rate was 77.2%, and the leaching effect was significantly reduced.

[0062] Comparative Example 3

[0063] Compared with Example 1, the remaining steps and parameters are exactly the same, except that the leaching conditions in the third stage of step S4 are changed: the reaction time is 30 minutes.

[0064] Experimental results show that the leaching rates of nickel, cobalt, and manganese are only 58.99%, 65.64%, and 56.85%, respectively, with a significant reduction in the overall leaching rate.

[0065] Comparative Example 4

[0066] Compared with Example 1, the remaining steps and parameters are exactly the same, except that the leaching conditions in the third stage of step S4 are changed: the initial pH is adjusted to 3.07.

[0067] Experimental results show that Fe during the reaction 3+ Precipitation occurs and metal ions are adsorbed, significantly reducing the leaching rates of nickel, cobalt, and manganese, making efficient leaching impossible.

[0068] Comparative Example 5

[0069] Compared to Example 1, this comparative example uses the existing pyrometallurgical recycling process for retired lithium battery cathode materials (traditional pyrometallurgical process), but does not employ the bio-chemical synergistic leaching method of this invention. Specifically, the cathode black powder is subjected to high-temperature roasting, reduction smelting, and slag-gold separation to extract valuable metals, without preparing bioacids or Fe. 3+ Solution, non-step leaching, no iron circulation.

[0070] Experimental results show that the lithium recovery rate is only about 75%, the comprehensive recovery rate of nickel, cobalt and manganese is about 80%, iron recycling cannot be achieved, a large amount of slag and flue gas are generated, and the energy consumption and carbon emissions are high.

[0071] Comparative Example 6

[0072] Compared to Example 1, this comparative example uses the existing microbial direct contact leaching process (traditional single biological direct leaching process), and does not use the stepwise non-contact synergistic leaching of this invention. Specifically, the *Thiobacillus ferrooxidans* bacterial solution is directly mixed with the positive electrode black powder for leaching, and the bioacid and Fe are not prepared separately. 3+ The solution has a slurry concentration of only 1%, a leaching cycle of about 10 days, and no iron ion circulation or synergistic mechanism.

[0073] Experimental results show that the lithium leaching rate is about 67%, and the combined leaching rate of nickel, cobalt, and manganese is about 58%. The slurry concentration is low and the cycle is long, which cannot meet the requirements of industrialization.

[0074] Comparative Example 7

[0075] Compared to Example 1, this comparative example uses a conventional pure chemical wet leaching process, without using bio-acids or biologically prepared Fe. 3+ The solution is specifically prepared by leaching with concentrated sulfuric acid and concentrated hydrochloric acid, with the addition of chemical oxidants, reducing agents, and iron salts. The leaching process is the same as in Example 1, but all industrial chemical reagents are used.

[0076] Experimental results show that the consumption of acid and chemical reagents is about 5 times that of the present invention, resulting in high cost, large volume of acidic waste liquid, high risk of secondary pollution, no internal iron circulation, and the need to add iron salts.

Claims

1. A method for the co-leaching of cathode materials from retired lithium-ion batteries, characterized in that, Includes the following steps: S1. Using *Thiobacillus ferrooxidans* to prepare bioacids and Fe-containing compounds, respectively. 3+ The solution; S2. The bio-acid obtained in step S1 is mixed with ternary cathode black powder and subjected to the first stage of leaching to separate lithium-containing leachate and ternary acid leaching residue. S3, the Fe-containing sample obtained in step S1 3+ The solution is mixed with lithium iron phosphate cathode black powder to form a slurry, which is then subjected to a second leaching process to separate Fe-containing materials. 2+ and Li + The leachate; S4. The tribasic acid leaching residue obtained in step S2 and the Fe-containing residue obtained in step S3 2+ The leachate is mixed and the third leaching stage is carried out to leach out nickel, cobalt and manganese.

2. The method according to claim 1, characterized in that, In step S4, Fe 2+ Fe in the leachate 2+ As a reducing agent, the high-valence nickel, cobalt, and manganese oxides in the ternary acid leaching residue obtained in step S2 are reduced to acid-soluble low-valence oxides, while Fe... 2+ Oxidized to Fe 3+ Fe 3+ Hydrolysis produces H + It also enables the acid leaching of nickel, cobalt, and manganese.

3. The method according to claim 1 or 2, characterized in that, In step S1, the preparation conditions for the bioacid include: a sulfur mass fraction of 0.5–2.0% in the culture medium, a culture time of 6–10 days, a final pH of 0.8–1.2, and H₂O. + The concentration is 0.25–0.40 mol / L.

4. The method according to claim 1 or 2, characterized in that, In step S1, Fe 3+ The preparation conditions for the solution include: the culture medium contains Fe 2+ The source was supplemented with FeSO4·7H2O in a semi-continuous manner, and the culture time was 6-10 days. The endpoint was Fe 3+ The concentration is 40–60 g / L, and the pH is 1.5–2.

0.

5. The method according to claim 1, characterized in that, In step S2, during the first leaching stage, the liquid-to-solid ratio of bio-acid to ternary cathode black powder is 50–100:1 mL / g, the reaction temperature is 25–35℃, the reaction time is 2–4 hours, and the reactor rotation speed is 250–350 rpm.

6. The method according to claim 1, characterized in that, In step S3, during the second leaching stage, the slurry concentration of lithium iron phosphate cathode black powder is 5-15%, and Fe... 3+ The molar ratio of iron in lithium iron phosphate to iron is 1:(0.9-1.1), the reaction time is 20-40 minutes, the reaction temperature is 25-35℃, and the reactor rotation speed is 250-350 rpm.

7. The method according to claim 1, characterized in that, In step S4, during the third leaching stage, the Fe-containing solution obtained in step S3... 2+ The mixing ratio of the leachate and the tribasic acid residue obtained in step S2 is based on Fe 2+ The mass ratio of the initial ternary cathode black powder to the mass of the initial ternary cathode black powder is (1.0~1.5):

1. The reaction time is 50~120 minutes, the reaction temperature is 25~35℃, and the reactor rotation speed is 250~350 rpm.

8. The method according to claim 1, 2, or 7, characterized in that, In step S4, during the third leaching stage, the final reaction pH is 2.0–2.5, and Fe… 2+ The residual concentration is 10–15 g / L, Fe 3+ The concentration of the product is 30–40 g / L.

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