Method and system for leaching metal in waste lithium battery positive electrode material through microorganism-electrochemical coupling

Abstract

The invention discloses a method and system for leaching metal in a waste lithium battery positive electrode material through microorganism-electrochemical coupling, and belongs to the technical field of wet leaching. And the leaching efficiency of the metal in the waste lithium battery positive electrode material is remarkably improved. Compared with a traditional pure biological leaching technology, the leaching rate of lithium can reach 99% or above, the leaching rate of cobalt, nickel and manganese can reach 98% or above, and compared with the traditional biological leaching technology, the metal recovery rate is increased by 16%-22%. Meanwhile, the leaching reaction period is greatly shortened to be within 24-48 h, the problem that the traditional biological leaching reaction rate is low is effectively solved, and the turnover efficiency of industrial production is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of wet leaching, and particularly relates to a method and system for leaching metals in positive electrode materials of waste lithium batteries by microbial-electrochemical coupling. BACKGROUND

[0002] Retired batteries (such as ternary lithium batteries NCM / NCA and lithium cobalt batteries LCO) are rich in cobalt, nickel, lithium and other rare and high-value strategic metals in the positive electrode materials, and their recovery not only has significant economic value, but also bears the dual strategic significance of guaranteeing sustainable supply of resources and reducing environmental pressure. Therefore, developing efficient and environmentally friendly waste lithium battery metal recovery technology has become the focus of current industry and academia.

[0003] The current mainstream technology for metal recovery of waste lithium battery positive electrode materials mainly includes pyrometallurgy and hydrometallurgy. Specifically, the pyrometallurgical process realizes metal separation through high-temperature smelting, which has the advantages of large processing capacity and strong adaptability to raw materials. However, its inherent defects are also very significant, for example, the high energy consumption leads to high operating costs, and in the high-temperature reduction process, part of the high-value metals (such as lithium) are easily volatilized and lost, resulting in relatively low overall metal recovery rate. More worth noting is that toxic and harmful gases such as dioxins may be produced in the pyrometallurgical process, causing secondary pollution to the environment, which is contrary to the concept of green and sustainable development. In contrast, the traditional hydrometallurgical technology mainly relies on strong acids (such as sulfuric acid and nitric acid) as leaching agents, supplemented by strong reducing agents (such as hydrogen peroxide) to promote metal dissolution. This method shows a high level in metal recovery rate, but in actual operation, the dependence on strong corrosive chemicals makes the process cost high, and the treatment of acidic waste liquid after leaching is difficult, which easily causes serious secondary environmental pollution, and also fails to fundamentally solve the environmental friendliness problem.

[0004] Under this background, bioleaching technology has received widespread attention in recent years due to its environmental friendliness and mild operating conditions. The core of this technology is to use specific microorganisms, such as Acidithiobacillus ferrooxidans, to produce acid through their metabolic activity, and to oxidize divalent iron ions (Fe 2+ ) in the solution to generate trivalent iron ions (Fe 2+ ). Among them, Fe 3+ as a strong oxidizing agent can effectively attack and dissolve high-valence metal oxides in waste lithium battery positive electrode materials, thereby realizing the leaching of lithium, cobalt, nickel and other metals. The advantage of this method is that it avoids the direct need for strong acid and strong base, and the requirements for equipment are relatively low, showing potential green recovery prospects.

[0005] However, in practical applications, especially in the face of the complex characteristics of waste lithium battery cathode materials, the micro-mechanism on which pure bioleaching technology relies faces more profound challenges in efficiency and universality. The root cause lies in the fact that after multiple charge and discharge cycles, a dense and relatively stable passivation layer, such as lithium carbonate (Li2CO3) and cobalt tetroxide (Co3O4), is easily formed on the surface of waste lithium battery cathode materials. This passivation layer acts as a strong barrier, severely hindering the direct contact between microorganisms and the active substances inside the cathode material, and limiting the effective penetration of microbial metabolites (such as Fe 3+ and H + ) into the material interior. The biological activity of microorganisms and the diffusion rate of their metabolites essentially determine the overall reaction kinetics of bioleaching, and the presence of the passivation layer forms the main mass transfer and reaction resistance in this system.

[0006] Specifically, this inherent limitation at the principle level brings multiple negative effects. First, the physical barrier and chemical inertness of the passivation layer make the reaction rate of pure bioleaching extremely slow, usually requiring an immersion period of 3-7 days, and the cobalt leaching rate often difficult to break through 60%. Second, due to the limitation of leaching rate, metal ions (especially Co 2+ ) gradually accumulate in the reaction system over a long period of time, and when their concentration exceeds a certain threshold, they will have a significant toxic inhibition effect on acidophilic microorganisms, further reducing the activity of microorganisms, thus forming a negative feedback cycle, further hindering the improvement of leaching efficiency. In this case, the advantages of bioleaching, such as mildness and environmental friendliness, are offset by its inherent kinetic bottleneck, making it difficult to achieve the recovery efficiency required for industrial-scale application. Although researchers have tried to introduce physical pretreatment methods such as ultrasound, microwave irradiation, or mechanical activation to break the passivation layer, these methods generally have high energy consumption, complex operation, and difficulty in achieving large-scale continuous treatment, which is contrary to the original intention of bioleaching technology being "green and low-cost". Another literature proposes an electrochemical-assisted leaching technology, but it is usually not effectively coupled with the biological system and still relies on external chemical oxidants, which does not fundamentally solve the problem of chemical reagent consumption and secondary pollution, and also fails to fully utilize the environmental friendliness of bioleaching.

[0007] Therefore, how to develop a new green and efficient leaching technology that can not only maintain the advantages of bioleaching such as environmental friendliness and mild operation, but also effectively break the passivation layer on the surface of waste lithium battery cathode materials, significantly improve the leaching rate and metal recovery rate, and avoid the inhibition of high-concentration metal ions on microbial activity, has become a key challenge and technical problem that needs to be solved for technical personnel in the field. SUMMARY

[0008] In view of the problems of low leaching efficiency, high energy consumption, serious secondary pollution and inhibition of the passivation layer on the surface of the positive material and high-concentration metal ion toxicity in the biological leaching process in the existing recycling technology of waste lithium battery positive material, the present application provides a method and system for leaching metals in waste lithium battery positive material by microorganism-electrochemical coupling. 3+ Through the construction of the triple synergistic mechanism of "microbial metabolic acid and oxidation", "low-voltage microelectric field in-situ precise activation" and "electrochemical auxiliary Fe

[0009] To achieve the above-mentioned application purposes, the present application adopts the following technical solutions:

[0010] In the first aspect, the present application provides a system for leaching metals in waste lithium battery positive material by microorganism-electrochemical coupling, comprising: a reaction cavity, a microelectric field generating unit, an external constant voltage DC power supply, a magnetic stirring device, a temperature control monitoring module, a pH monitoring module, a redox potential monitoring module and a data acquisition and control unit; the microelectric field generating unit is installed inside the reaction cavity and is composed of an anode and a cathode, and the distance between the anode and the cathode is fixed by a mechanical locking mechanism; the anode and the cathode are connected to the external constant voltage DC power supply through sealed electrode leads; the magnetic stirring device comprises a magnetic stirring platform and a magnetic stirring sub, the magnetic stirring platform is installed at the bottom of the reaction cavity, and the magnetic stirring sub is placed inside the reaction cavity; the bottom of the magnetic stirring platform is integrated with a heating device.

[0011] Further, the pH monitoring module, the redox potential monitoring module and the magnetic stirring device are respectively connected to the data acquisition and control unit through data lines; the temperature control monitoring module is connected to the magnetic stirring device through data lines; the top of the reaction cavity is provided with a detachable sealing cover, and the sealing cover is integrated with standard interfaces for installing electrodes, sensors, inlet and outlet liquid pipelines and gas discharge ports.

[0012] Further, the main body material of the reaction cavity is selected from polytetrafluoroethylene or polyvinyl chloride; the effective volume of the reaction cavity is 1-500L; the inner surface roughness R a <0.4μm.

[0013] Further, the anode is a porous titanium mesh; the cathode is a graphite plate; the distance between the anode and the cathode is 2-5cm; the electrode lead is selected from pure platinum gold wire or copper wire coated with polytetrafluoroethylene.

[0014] Furthermore, the porosity of the porous titanium mesh is 40%-50%, and the mesh size is 1mm×1mm-2mm×2mm; the size of the graphite plate is set to form a uniform electric field distribution with the anode, and the thickness of the graphite plate is 5-10mm.

[0015] Furthermore, the rated output voltage of the external constant voltage DC power supply is 0-10V, and the rated output current range is 0-5A.

[0016] Secondly, the present invention provides a method for leaching metals from waste lithium battery cathode materials using a microbial-electrochemical coupling method, comprising the following steps: placing waste lithium battery cathode black powder in pure water and stirring evenly to obtain a suspension slurry; placing the suspension slurry in the reaction chamber of the aforementioned microbial-electrochemical coupling leaching system for metals from waste lithium battery cathode materials; inoculating the reaction chamber with a solution of *Thiobacillus ferrooxidans*; controlling the temperature, pH, and redox potential of the reaction system using a temperature control monitoring module, a pH monitoring module, a redox potential monitoring module, and a data acquisition and control unit; stirring the suspension slurry using a magnetic stirring platform driven by a magnetic stir bar; simultaneously, applying a micro-electric field to the suspension slurry continuously through an external constant voltage DC power supply to carry out the leaching reaction; and performing solid-liquid separation after the reaction to obtain a leachate and residue containing lithium ions, cobalt ions, nickel ions, and manganese ions.

[0017] The micro-electric field applied by the external constant-voltage DC power supply mainly works through the following two mechanisms:

[0018] First, in-situ electrochemical activation and passivation layer destruction: Near the anode, the dense passivation layer (e.g., lithium carbonate, cobalt tetroxide) formed on the surface of spent lithium battery cathode material particles under the action of a micro-electric field is subjected to electrochemical oxidation. This electrochemical oxidation can selectively decompose or destroy the chemical bonds in the passivation layer, for example, promoting the decomposition of Li₂CO₃ into Li. + and CO3 2- This process can further oxidize Co3O4. The electrochemical activation process eliminates the need for traditional high-energy-consuming physical methods (such as ultrasound or microwave) or strong acid pretreatment, enabling in-situ, precise, and low-energy removal of the passivation layer. The removal of the passivation layer significantly increases the production of microbial metabolites (H2O). + Fe 3+ The direct contact area between the cathode material and the active material inside the cathode material significantly reduces the mass transfer resistance.

[0019] Second, Fe 2+ To Fe 3+ Electrochemical regeneration: On the surface of the porous titanium mesh anode, a micro-electric field can directly drive ferrous ions (Fe2+) in the solution. 2+ An electrochemical oxidation reaction occurs, producing ferric ions (Fe3+).3+ ), that is, Fe 2+ -e - →Fe 3+ This electrochemical regeneration mechanism works synergistically with the bio-oxidation of microorganisms to maintain a high concentration of Fe in the reaction system. 3+ This provides a continuous supply of the strong oxidizing power required for leaching. The aforementioned electrochemical regeneration mechanism effectively compensates for the Fe... 3+ The problem of potentially limited regeneration rates, especially when high concentrations of metal ions inhibit microbial activity, is addressed by electrochemical methods, which offer a rapid and stable solution for Fe. 3+ This supplementary pathway ensures a continuous driving force for metal dissolution. Furthermore, the micro-electric field can accelerate H+ dissolution through electrophoresis. + and Fe 3+ The migration of active species to the surface of the cathode material particles and the diffusion of metal ion products from the particle surface further enhance the overall reaction kinetics. The trivalent iron ions then undergo a redox reaction with the metal oxides in the spent lithium-ion battery cathode material, allowing lithium, cobalt, nickel, and other metals to be released in ionic form (Li... + Co 2+ Ni 2+ ) dissolves into the leachate, and at the same time Fe 3+ Reduced to Fe 2+ Fe 2+ It is oxidized again to Fe under the action of microorganisms and electrochemistry. 3+ To form highly efficient Fe 3+ / Fe 2+ Cyclic oxidation system.

[0020] Furthermore, the particle size of the waste lithium battery cathode black powder is 45-60μm.

[0021] Furthermore, the mass ratio of the waste lithium battery cathode black powder to water is 1:(5-15).

[0022] Furthermore, the viable bacterial concentration of the *Thiobacillus acidophilus* bacterial suspension is 1.0 × 10⁻⁶. 8 -1.0×10 10 The inoculum size is 5-15% of the total volume of the suspension slurry, with an inoculum size of 1 / mL.

[0023] Furthermore, the temperature of the reaction system is 28-32℃; the pH of the reaction system is 1.8-2.5; the stirring speed is 100-300 rpm; the oxidation-reduction potential is 650-700 mV; the external constant voltage DC power supply applies a micro-electric field by outputting a DC voltage of 0.3-0.8V; and the leaching reaction time is 24-48 h.

[0024] The working principle of this invention is as follows: In the provided microbial-electrochemical coupled leaching system for metals in waste lithium battery cathode materials, waste lithium battery cathode black powder is mixed with water to form a uniform slurry. By inoculating highly active *Thiobacillus acidophilus*, under suitable temperature conditions of 28-32°C and stirring conditions of 100-300 rpm, the microorganisms first initiate their metabolic activity, utilizing the inherent or slightly added Fe in the solution. 2+ As an electron donor, it is oxidized to Fe. 3+ And in the process, H is generated. + This stabilizes the slurry pH in an acidic environment of 1.8-2.5, creating conditions for the dissolution of metal oxides. The Fe... 3+ It is the main oxidizing leaching agent, capable of attacking and dissolving metal oxides such as lithium, cobalt, and nickel in cathode materials.

[0025] Simultaneously, a constant DC voltage of 0.3–0.8V is applied to the system, establishing a stable micro-electric field between the porous titanium mesh anode and the graphite plate cathode. This micro-electric field significantly accelerates the leaching process through the following multiple synergistic mechanisms:

[0026] First, on and near the anode surface, the micro-electric field can directly and in situ electrochemically activate and oxidize the dense passivation layer (e.g., Li₂CO₃, Co₃O₄) formed on the surface of the cathode material particles. The electrochemical force overcomes the mass transfer and reaction barriers caused by pure biological leaching of the passivation layer, thereby exposing more active sites for microbial metabolites (H₂O₃, H₂O₄). + and Fe 3+ Contact and reaction, this in-situ activation avoids energy-intensive physical pretreatment or strong acid pretreatment.

[0027] Secondly, the micro-electric field efficiently removes Fe produced by microbial metabolism or reduced during leaching from the anode surface. 2+ Electrochemical oxidation regeneration to Fe 3+ This electrochemical regeneration mechanism complements the bio-oxidation of microorganisms, ensuring the Fe content in the reaction system. 3+ The continuous high-concentration supply maintained a strong oxidative leaching capacity, thereby significantly accelerating the leaching rate. Electrochemical regeneration, especially in the later stages of leaching, resulted in Fe... 2+ At potentially high concentrations, it plays a crucial role in inhibiting microbial activity, ensuring Fe... 3+ The supply is not limited by microbial activity.

[0028] Furthermore, the micro-electric field-induced electrophoretic effect promotes the leaching of the leaching agent (H). + Fe 3+ The rapid migration of ions to the surface of cathode material particles accelerates the production of metal ion products (Li). + Co 2+Ni 2+ Diffusion from the particle surface effectively reduces the liquid film mass transfer resistance and further enhances the overall reaction kinetics.

[0029] Through microbial metabolic acid production and oxidation, in-situ precise activation by micro-electric field, and electrochemically assisted Fe 3+ Through the synergistic effect of recycling and regeneration, this invention can efficiently and rapidly dissolve valuable metals in spent lithium battery cathode materials, significantly shortening the reaction time to 24-48 hours. The leaching rates of lithium, cobalt, nickel, and manganese can reach over 99%, 98%, 98%, and 98%, respectively. After the reaction, a leachate rich in metal ions can be obtained through simple solid-liquid separation for subsequent metal separation and purification. Meanwhile, the residue is mainly composed of inert components, making it environmentally friendly.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] 1. Improved Leaching Efficiency: The microbial-electrochemical coupled leaching method used in this invention significantly improves the leaching efficiency of metals in waste lithium-ion battery cathode materials through a triple synergistic mechanism. Compared with traditional pure bioleaching technology, the leaching rate of lithium can reach over 99%, and the leaching rates of cobalt, nickel, and manganese can reach over 98%, resulting in a 16%-22% increase in metal recovery rate. Simultaneously, the leaching reaction cycle is significantly shortened to within 24-48 hours, effectively solving the problem of slow reaction rates in traditional bioleaching and improving the turnover efficiency of industrial production.

[0032] 2. No external chemical reagents required: Throughout the leaching process, this invention relies solely on microbial metabolites and electrochemical reactions, eliminating the need for additional reducing agents (such as H₂O₂ or Na₂S₂O₃). This avoids the high costs and potential secondary pollution associated with chemical reagents. The method utilizes Fe… 3+ / Fe 2+ The system's biological and electrochemical synergistic regeneration enables a continuous in-situ supply of the leachate.

[0033] 3. In-situ Destruction of Passivation Layer: The low-voltage micro-electric field introduced in this invention enables in-situ, precise, and low-energy electrochemical activation and destruction of dense passivation layers (such as Li2CO3 and Co3O4) on the surface of spent lithium-ion battery cathode materials. This mechanism effectively overcomes the limitation of the passivation layer on the leaching rate and eliminates the need for traditional physical pretreatment (such as high-energy-consuming ultrasonic, microwave irradiation, or mechanical activation), thereby reducing energy consumption and operational complexity. The micro-electric field avoids excessive damage to the internal crystal structure of the material, preserving the convenience of subsequent metal separation and purification.

[0034] 4. Environmentally Friendly: The method provided by this invention maintains the pH value of the system within a weakly acidic range of 1.8-2.5 throughout the entire leaching reaction process, avoiding the large consumption of strong acids and alkalis and the resulting corrosive waste liquids associated with traditional hydrometallurgy, thus reducing environmental pollution at the source. The operating conditions adopted in this invention are mild and in line with the concepts of green metallurgy and sustainable development.

[0035] 5. System Scalability: The microbial-electrochemical coupled leaching system for metals in spent lithium battery cathode materials provided by this invention adopts a modular design concept. Its acid-resistant reaction chamber, micro-electric field generation unit, stirring device, temperature control, and monitoring module all possess good scalability and integration. The system has a compact structure, is easy to operate, and can be easily scaled up from laboratory to pilot-scale and even industrial-scale applications, demonstrating good engineering prospects. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the system for leaching metals from waste lithium battery cathode materials using a microbial-electrochemical coupling method, as described in this invention.

[0038] Figure 2 This is a flowchart of the method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to the present invention. Detailed Implementation

[0039] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0040] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0041] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0042] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0043] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0044] This invention provides a system for leaching metals from waste lithium battery cathode materials using a microbial-electrochemical coupling method. The system includes: a reaction chamber, a micro-electric field generating unit, an external constant-voltage DC power supply, a magnetic stirring device, a temperature control monitoring module, a pH monitoring module, a redox potential monitoring module, and a data acquisition and control unit. The micro-electric field generating unit, installed inside the reaction chamber, consists of an anode and a cathode, with the distance between them fixed by a mechanical locking mechanism. Both the anode and cathode are connected to the external constant-voltage DC power supply via sealed electrode leads. The magnetic stirring device includes a magnetic stirring platform and a magnetic stir bar. The magnetic stirring platform is installed at the bottom of the reaction chamber, and the magnetic stir bar is placed inside the reaction chamber. The bottom of the magnetic stirring platform integrates a heating function. The pH monitoring module, redox potential monitoring module, and magnetic stirring device are connected to the data acquisition and control unit via data cables. The temperature control monitoring module is connected to the magnetic stirring device via a data cable. The top of the reaction chamber has a removable sealing cover, which integrates standard interfaces for installing electrodes, sensors, inlet / outlet liquid pipelines, and gas exhaust ports.

[0045] In some preferred embodiments, the reaction chamber is a one-piece molded cylindrical or rectangular container with a wall thickness of 3-10 mm, typically 5 mm, to ensure sufficient structural strength and long-term corrosion resistance under acidic environments and stirring conditions. The main body material of the reaction chamber is selected from polytetrafluoroethylene (PTFE) or medical-grade polyvinyl chloride (PVC) materials that are resistant to strong acids, high temperatures (up to 120°C), and have high mechanical strength. PTFE is usually the preferred choice due to its superior chemical inertness and temperature resistance. The effective volume of the reaction chamber is designed to be 1-500 L to accommodate various conditions. From laboratory-scale research and pilot-scale verification to industrial-scale production applications, a 10L reaction chamber typically has a diameter of 200mm and a height of 320mm. The chamber usually has an integrated jacket structure for circulating a constant-temperature liquid (such as a water bath or heat transfer oil) to achieve precise temperature control of the reaction system. The jacket is connected to an external constant-temperature circulator, and heat exchange occurs between the jacket and the reaction chamber wall through the circulating liquid, thereby maintaining the set temperature of the slurry inside the chamber. The internal surface of the reaction chamber is finely machined to a mirror-polished finish with a surface roughness R... a With a micrometer diameter of <0.4μm, it effectively prevents the formation of microbial films and reduces material adsorption, facilitating cleaning and maintenance. The top of the reaction chamber is equipped with a removable sealing cap, which typically uses a flange connection and O-ring seal to ensure the airtightness of the reaction system. The sealing cap integrates multiple standard interfaces, which are threaded and equipped with acid-resistant sealing gaskets for installing electrode leads, Pt100 temperature sensors, pH sensors, ORP sensors, inlet and outlet liquid lines, and gas exhaust ports for gas exchange and pressure balancing.

[0046] In some preferred embodiments, the micro-electric field generating unit is precisely installed inside the reaction chamber and is the core component for electrochemical assisted leaching. It consists of an anode and a cathode, and is equipped with an electrode spacing adjustment and fixing mechanism. The anode is a porous titanium mesh structure made of industrial pure titanium selected from ASTM B265 Grade 1 or Grade 2, without any coating treatment, ensuring excellent corrosion resistance and stability in a strongly acidic environment of pH 1.8-2.5. The porous titanium mesh is prepared using precision stamping or laser cutting processes to ensure the uniformity of the mesh openings. Its porosity is 40%-50% to maximize the effective reaction surface area while maintaining good slurry permeability. The mesh size is 1mm×1mm-2mm×2mm, preferably a 1.5mm×1.5mm square mesh, to provide the maximum effective electrochemical reaction area and minimize slurry flow resistance. The anode is fixed inside the reaction chamber by an insulating bracket made of polytetrafluoroethylene or polyether ether ketone (PEEK) to ensure electrical insulation between it and the chamber wall and the cathode. The insulating bracket also serves to support and position the electrode, preventing it from shaking during stirring. The anode is connected to an external constant voltage DC power supply via sealed electrode leads. The electrode leads are made of acid-resistant and highly conductive pure platinum wire or copper wire coated with polytetrafluoroethylene. The connection between the electrode leads and the electrode body is welded or riveted and then sealed with PTFE to prevent acid corrosion and short circuits.

[0047] In some preferred embodiments, the cathode is a high-purity graphite plate with a carbon content of not less than 99.95% and an ash content of less than 0.05%, ensuring extremely high chemical inertness and excellent conductivity in acidic environments. The graphite plate is prepared using isostatic pressing or flexible graphite pressing processes to obtain a uniform and dense structure. The dimensions of the graphite plate are designed to form a uniform electric field distribution with the anode; typically, its effective area is slightly larger than or equal to the effective area of ​​the anode, and its thickness is 5-10 mm, preferably 6 mm, to ensure sufficient mechanical strength and charge transfer capability. The cathode is also fixed inside the reaction chamber by an acid-resistant insulating support and connected to an external power source via sealed electrode leads, the material of which is the same as that of the anode leads.

[0048] The microbial-electrochemical coupling leaching system for metals in spent lithium battery cathode materials is equipped with a precise electrode spacing adjustment mechanism. This mechanism allows for stepless adjustment of the distance between the anode and cathode within a range of 2-5 cm to adapt to different reaction systems and optimize electric field distribution. The adjustment mechanism typically consists of a screw or slide rail structure and is secured by a mechanical locking mechanism (such as a locking nut) to ensure the stability of the spacing once set, preventing displacement during operation. All components of this mechanism that come into contact with the reaction solution are made of acid-resistant insulating materials such as polytetrafluoroethylene, polyetheretherketone (PEEK), or high-purity ceramics to ensure long-term reliability in corrosive environments.

[0049] In some preferred embodiments, the external constant voltage DC power supply is an external, independent or integrated high-precision programmable DC power supply, such as the Keysight E3631A or similar industrial-grade power supply. Its rated output voltage range is 0-10V, and its rated output current range is 0-5A, sufficient to meet the low voltage and low current requirements described in this invention. The power supply has a precise constant voltage output mode and can operate stably at a preset voltage value of 0.3-0.8V, with a voltage accuracy of ±0.01V and voltage fluctuation of less than 0.5%. The power supply integrates real-time voltage and current monitoring and display functions, which can display the current voltage and current output values ​​in real time on an LED or LCD screen. Simultaneously, to ensure the safety of system operation, the power supply has multiple built-in protection mechanisms, including overload protection, overvoltage protection, overcurrent protection, and short-circuit protection, ensuring the safety of system operation and automatically cutting off the output when an abnormal situation is detected. The power supply is reliably electrically connected to the anode and cathode through wires with good insulation and acid corrosion resistance; these wires are typically high-purity copper cables with PTFE insulation.

[0050] In some preferred embodiments, the magnetic stirring device is a key piece of equipment for achieving uniform mixing of the slurry. It typically includes an external permanent magnet synchronous motor-driven magnetic stirring platform mounted at the bottom of the reaction chamber. This platform drives a PTFE-coated magnetic stir bar inside the reaction chamber to rotate and agitate the slurry via magnetic coupling. The magnetic stir bar uses a high-strength permanent magnet material (such as neodymium iron boron) as its core, and is entirely coated with a uniformly thick layer of PTFE, giving it excellent acid resistance, wear resistance, and biocompatibility. The stir bar is preferably olive-shaped or cylindrical, with a length of 50-100 mm to accommodate reaction chambers of different volumes. The magnetic stirring device features stepless speed regulation, controlled by a microprocessor, allowing precise adjustment of the stirring speed within the range of 100-300 rpm. It also has speed feedback control, using a Hall sensor to monitor the stir bar speed in real time and performing PID closed-loop control to ensure the stability of the stirring speed, with fluctuations strictly controlled within ±2 rpm. The bottom of the stirring platform is usually integrated with a heating function. By precisely controlling the heating power and working with a temperature sensor (such as PT100), the reaction system can be indirectly heated to maintain the set temperature. The heating power can be continuously adjusted within the range of 0-500W.

[0051] In some preferred embodiments, the temperature control monitoring module, pH monitoring module, and redox potential monitoring module are the core components for ensuring precise control and real-time monitoring of reaction conditions, and include high-precision sensors and intelligent control units.

[0052] The temperature control monitoring module includes a high-precision Pt100 temperature sensor. Its sensing element is a platinum resistance thermometer, offering high stability, high sensitivity, and linearity. The temperature sensor is directly immersed in the reaction slurry and encapsulated in a 1mm thick PTFE protective sleeve to prevent corrosion and ensure measurement accuracy. The temperature sensor is connected to an intelligent temperature controller with a PID (proportional-integral-derivative) control algorithm, such as the Omron E5CC series. The controller analyzes the deviation between the temperature value fed back by the sensor and the set value, precisely controlling the heating power of the magnetic stirring device (or the external circulating constant temperature water bath heating / cooling system) to accurately maintain the reaction system temperature within a preset range of 28-32℃, typically set to 30℃, with temperature fluctuations strictly controlled to no more than ±0.5℃.

[0053] The pH monitoring module includes a combined glass electrode pH sensor, such as the Mettler Toledo InPro3253 / 120 / Pt100 type. Its sensing part is made of acid-resistant high-strength glass and equipped with an Ag / AgCl reference electrode. The pH sensor is also encapsulated with a polytetrafluoroethylene protective sleeve to protect the sensitive part and prevent corrosion, and to measure the pH value of the reaction slurry in real time online. The pH sensor is connected to a high-precision pH meter, such as the Mettler Toledo SevenExcellence TM pH meter. The measuring range of the pH meter is 0 - 14, the accuracy is ±0.02 pH units, and the resolution is 0.01 pH. The pH meter has data storage and output functions, and can transmit data to the central control unit through RS232 or USB interfaces.

[0054] The ORP monitoring module includes a platinum electrode / Ag - AgCl reference electrode composite ORP sensor, such as the Hanna HI2000B type. Its sensing part is high-purity pure platinum to ensure stability in the redox system. The ORP sensor is encapsulated with a polytetrafluoroethylene sleeve and measures the redox potential of the reaction slurry in real time online. The ORP sensor is connected to a high-precision ORP meter, such as the Hanna HI98190 type. The measuring range of the ORP meter is -1000~+1500 mV, the accuracy is ±1 mV, and the resolution is 1 mV. The ORP meter also has data storage and output functions.

[0055] The temperature control, pH and ORP monitoring modules are all connected to a central data acquisition and control unit, such as an automation system based on LabVIEW TM or a Siemens PLC (Programmable Logic Controller). The unit has multi-channel analog signal inputs (for receiving sensor data), digital signal processing, and a human-machine interface (HMI, usually a touch screen), which can display, record and store various parameter data in real time and visually present them through a data visualization interface. The unit can联动调节 and optimize the control of parameters such as heating power, stirring speed and applied voltage according to a preset program, and realize the automated and intelligent operation of the entire leaching process. The system also has functions such as displaying data historical trend graphs, alarm management and remote monitoring.

[0056] The structural design of the system for microbial-electrochemical coupled leaching of metals from the cathode materials of waste lithium batteries provided by the present invention fully considers the requirements of corrosion resistance, operation convenience, precise control and scale-up application.

[0057] This invention provides a method for the microbial-electrochemical coupling leaching of metals from spent lithium-ion battery cathode materials, aiming to efficiently and environmentally recover valuable metals such as lithium, cobalt, nickel, and manganese from these materials. The core of this technical solution lies in constructing a microbial metabolic acid production and oxidation process, in-situ precise activation using a low-voltage micro-electric field, and electrochemically assisted Fe... 3+ The triple synergistic mechanism of recycling and regeneration.

[0058] Figure 1 This is a schematic diagram of the system for leaching metals from waste lithium battery cathode materials using a microbial-electrochemical coupling method, as described in this invention.

[0059] This invention provides a method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials. The method comprises specific and interconnected operational steps, forming an efficient recycling process. The method includes the following precisely controlled steps:

[0060] (1) Pretreatment and preparation of suspension slurry for waste lithium battery cathode materials

[0061] The purpose of this step is to convert waste lithium batteries into a homogeneous slurry suitable for microbial-electrochemical coupled leaching reactions. First, the waste lithium batteries are safely disassembled and thoroughly discharged to eliminate potential short-circuit and thermal runaway risks. The discharged batteries are then mechanically crushed, for example, by a hammer crusher, followed by fine grinding using a ball mill or air jet mill to obtain a uniformly sized powder. The ground material is then precisely sieved using a vibrating screen or air jet sieve to ensure that the final waste lithium battery cathode black powder has a particle size distribution in the range of 20-80 μm. This waste lithium battery cathode black powder mainly contains lithium cobalt oxide (e.g., LiCoO2, with a purity potentially exceeding 97%) and lithium nickel cobalt manganese oxide (e.g., Li(Ni)O2)... 0.5 Co 0.2 Mn 0.3 O2 (commonly known as ternary materials) or lithium nickel cobalt aluminum oxide (e.g., Li(Ni)) 0.8 Co 0.15 Al 0.05 The black powder contains various active substances such as O2 (commonly known as NCA material). In addition, it contains approximately 5%-10% (by mass) of conductive agents (such as carbon black and graphite) and approximately 2%-5% of binders (such as polyvinylidene fluoride PVDF). Subsequently, the precisely weighed waste lithium battery cathode black powder is mixed with strictly treated purified water at a solid-liquid mass ratio of 1:(5-15). The mixed material is transferred to a pretreatment container equipped with a stirring paddle and stirred at a rate between 150-300 rpm for 30-60 minutes to form a uniform suspension slurry without obvious particle agglomeration.

[0062] (2) Inoculation of microbial culture

[0063] The prepared suspension slurry was precisely transferred into the reaction chamber, which possessed excellent acid corrosion resistance, within the microbial-electrochemical coupled leaching system for metals in spent lithium-ion battery cathode materials. The main body of the reaction chamber was preferably made of polytetrafluoroethylene (PTFE) or medical-grade polyvinyl chloride (PVC). Inside the reaction chamber, a cultured and enriched solution of *Acidithiobacillus ferrooxidans* was inoculated; the inoculation amount was 5%-15% (v / v) of the total volume of the suspension slurry. For example, an inoculation amount of 10% of the total volume was selected, resulting in a system potential greater than 600 mV and a viable bacterial concentration greater than 1.0 × 10⁻⁶ at the end of the process. 8 The *Acidithiobacillus acidophilus* strain, such as ATCC 23270, has been continuously domesticated and optimized in the laboratory to maintain high metabolic activity under low pH (1.5-2.5) and high concentrations of metal ions (e.g., 5 wt.% of waste lithium battery cathode black powder). Before inoculation, the viable cell concentration of the bacterial solution was accurately counted using a hemocytometer to achieve 1.0 × 10⁻⁶ cells / mL. 8 -1.0×10 10 To avoid introducing other microorganisms and contaminating the reaction system, the bacterial solution must be filtered through a sterile filter membrane with a pore size of 0.22 μm before inoculation, and the inoculation operation must be completed in a clean bench. The enrichment culture of the bacterial solution is usually carried out in 9K medium, which contains (NH4)2SO4 3.0 g / L, K2HPO4 0.5 g / L, MgSO4·7H2O 0.5 g / L, KCl 0.1 g / L, Ca(NO3)2 0.01 g / L and FeSO4·7H2O 44.3 g / L. The initial pH is adjusted to 1.6, the culture temperature is set at 30℃, and the culture is shaken until the late logarithmic growth phase.

[0064] (3) Setting up and applying the micro electric field generating unit

[0065] Inside the reaction chamber, a customized micro-electric field generating unit is precisely installed. This unit primarily consists of a porous titanium mesh anode and a graphite plate cathode. The porous titanium mesh anode is made of industrial pure titanium (ASTM B265 Grade 1 or Grade 2). The porosity of the titanium mesh is designed to be between 30% and 60%, preferably 45%. The mesh diameter is 0.5 to 2 mm, preferably a 1.0 mm × 1.0 mm square mesh. The anode is fixed by an insulating support made of polytetrafluoroethylene (PTFE) or polyetheretherketone (PEEK) and connected to an external power source via sealed electrode leads. The electrode leads are made of acid-resistant and highly conductive pure platinum wire or copper wire coated with PTFE. The graphite plate cathode is made of high-purity isostatic graphite or flexible graphite material with a carbon content of over 99.95% and an ash content of less than 0.05%. For example, the cathode dimensions are 100mm × 80mm × 5mm (length × width × thickness); the anode and cathode are precisely fixed together using a non-conductive PTFE bracket to ensure that the distance between them is maintained within the range of 2-5cm, preferably 3cm. The micro-electric field generating unit is electrically connected to an external constant voltage DC power supply via acid-resistant insulated wires. The external constant voltage DC power supply is a high-precision programmable DC power supply with precise control capability for outputting a DC voltage of 0.3-0.8V, preferably with an applied voltage of 0.6V, and its voltage accuracy can reach ±0.01V. This power supply integrates constant voltage output, constant current output, overcurrent protection, overvoltage protection, and short circuit protection functions.

[0066] (4) Microbial-electrochemical coupled leaching reaction

[0067] Within the reaction chamber, the temperature of the reaction system is precisely controlled at 28-32℃, preferably 30℃. Temperature control is achieved through a heating module integrated into the bottom of a magnetic stirrer located outside the reaction chamber, in conjunction with a Pt100 temperature sensor and a PID (proportional-integral-derivative) controller immersed inside the chamber. The magnetic stirrer, driven by a PTFE-coated magnetic stir bar (typically olive-shaped, 60mm in length) inside the reaction chamber, continuously and uniformly stirs the slurry at a speed controlled within the range of 100-300 rpm, preferably 200 rpm. The leaching reaction lasts for 24-48 hours, preferably 30 hours. During this reaction cycle, the *Thiobacillus acidophilus*, through its metabolic activity, first utilizes the ferrous ions (Fe2+) present in the solution. 2+ As an energy source, it is oxidized to produce ferric ions (Fe3+). 3+ The process generates sulfuric acid (H2SO4) or other acidic metabolites, thus maintaining the pH of the reaction system within an acidic range of 1.8-2.5. The Fe... 3+It is a strong oxidant capable of oxidizing and dissolving high-valence metal oxides (such as LiCoO2 and Co3O4) in the cathode materials of spent lithium batteries. Simultaneously, the micro-electric field applied by the constant-voltage DC power supply continuously acts on the slurry system, creating a localized electrochemical environment on and around the electrode surface.

[0068] (5) Separation of leachate and residue

[0069] After the leaching reaction is completed, the reaction products are separated using solid-liquid separation techniques, including vacuum filtration, centrifugation, or plate and frame filtration. The separated product is rich in lithium ions (Li). + ), cobalt ions (Co) 2+ Nickel ions (Ni) 2+ ) and manganese ions (Mn 2+ The leachate is then further processed by solvent extraction, ion exchange, or precipitation crystallization units for fine separation and purification of the metal. The residue mainly consists of unreacted carbonaceous conductive agent, a small amount of residual aluminum foil fragments, and incompletely reacted inert components. After multi-stage washing, the wash water can be recycled or discharged after simple neutralization. The washed residue, after drying, can be further processed (such as carbon recovery) or safely disposed of according to local environmental regulations. This separation step ensures the effective recovery of valuable metals and the reduction and harmless treatment of solid waste.

[0070] Figure 2 This is a flowchart of the method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to the present invention.

[0071] Example 1: A method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials

[0072] 1. Material preparation:

[0073] Used ternary lithium batteries (Li(Ni) 0.5 Co 0.2 Mn 0.3 The O2 type cathode material is subjected to discharge, crushing, ball milling and sieving to obtain cathode black powder with a particle size range of 45-60μm. Its main metal composition is: Ni 14.5% (wt), Co 10.3% (wt), Mn 6.2% (wt) and Li 5.5% (wt).

[0074] Deionized water with a conductivity of less than 2 μS / cm.

[0075] A bacterial suspension of *Acidithiobacillus ferrooxidans* (ATCC 23270 domesticated strain) with a viable cell concentration of 1.2 × 10⁻⁶. 8per mL.

[0076] 2. Experimental setup and parameter settings:

[0077] Reaction chamber: A PTFE cylindrical reactor with an effective volume of 2L and a wall thickness of 5mm.

[0078] Micro-electric field generating unit:

[0079] Anode: ASTM B265 Grade 2 porous titanium mesh, 80mm×80mm in size, 45% porosity, and 1.5mm×1.5mm mesh size.

[0080] Cathode: High-purity isostatic graphite plate, with dimensions of 80mm×80mm×6mm.

[0081] Electrode spacing: 3.0cm, fixed by PTFE bracket.

[0082] Constant voltage DC power supply: Programmable DC power supply with a set voltage of 0.6V.

[0083] Magnetic stirring device: external magnetic stirring platform with built-in heating function, PTFE-coated olive-shaped magnetic stir bar (70mm long), stirring speed set to 200rpm.

[0084] Temperature control monitoring module: Pt100 temperature sensor;

[0085] pH monitoring module: composite glass pH electrode;

[0086] Oxidation-reduction potential monitoring module: platinum electrode ORP sensor;

[0087] All of the above sensors are immersed in the slurry and connected to the data acquisition and control unit.

[0088] Initial solid-liquid mass ratio: positive electrode black powder : pure water = 1 : 10 (i.e. 200g black powder, 2000mL pure water).

[0089] Inoculation volume: 200 mL (10% v / v of the total volume of the reaction system).

[0090] Initial pH: Adjusted to 2.0 with concentrated sulfuric acid (AR grade).

[0091] Reaction temperature: 30±0.3℃.

[0092] Reaction time: 30 hours.

[0093] 3. Experimental procedure:

[0094] 200g of positive electrode black powder was mixed with 2000mL of purified water and magnetically stirred to form a suspension slurry. An anode and cathode, a Pt100 temperature sensor, a composite glass pH electrode, a platinum electrode ORP sensor, and a magnetic stir bar were installed in a 2L PTFE reaction chamber. The suspension slurry was transferred into the reaction chamber and inoculated with 200mL of acclimation bacterial solution. Temperature and stirring speed were precisely controlled by a data acquisition and control unit, and a constant DC voltage of 0.6V was applied. During the reaction, samples were taken every 6 hours to analyze the metal ion concentration, pH value, and ORP value in the leachate.

[0095] 4. Experimental Results:

[0096] During the 30-hour reaction period, the pH value fluctuated steadily between 1.9 and 2.2. The ORP value gradually increased from an initial value of approximately 400 mV (relative to Ag / AgCl) and stabilized between 650 and 700 mV, indicating that Fe... 3+ / Fe 2+ The system has strong oxidizing properties, and the changes in the concentrations of nickel, cobalt, and lithium ions in the leachate over time are shown in Table 1.

[0097] Table 1

[0098] As shown in Table 1, after 30 hours of leaching, the leaching rates of lithium, cobalt, nickel, and manganese reached 99.46%, 98.94%, 98.31%, and 99.16%, respectively. This fully demonstrates that the method of the present invention achieves efficient metal leaching in a short time, without the addition of additional chemical oxidants during the leaching process, and generates a small amount of waste liquid.

[0099] Comparative Example 1: Leaching of metals from waste lithium battery cathode materials using pure microorganisms

[0100] This comparative example uses the same positive electrode material, bacterial solution, initial solid-liquid mass ratio, reaction temperature, stirring speed and initial pH as Example 1, but no micro-electric field is applied, that is, no external constant voltage DC power supply and micro-electric field generating unit are connected, and the other conditions are the same as those in Example 1.

[0101] 1. Material preparation:

[0102] Same as Example 1.

[0103] 2. Experimental setup and parameter settings:

[0104] The reaction chamber, magnetic stirring device, temperature control and pH and ORP monitoring modules are the same as in Example 1, but the micro electric field generating unit is not installed or is not powered on.

[0105] The initial solid-liquid mass ratio, bacterial inoculum amount, initial pH, reaction temperature and reaction time were kept consistent with those in Example 1, namely, the solid-liquid ratio was 1:10, the bacterial inoculum amount was 10% (v / v), the initial pH was 2.0, the reaction temperature was 30±0.3℃, and the reaction time was 30 hours.

[0106] 3. Experimental procedure:

[0107] 200g of positive electrode black powder was mixed with 2000mL of deionized water and stirred magnetically to form a suspension slurry. A Pt100 temperature sensor, a composite glass pH electrode, a platinum electrode ORP sensor, and a magnetic stir bar were installed in a 2L PTFE reaction chamber. The suspension slurry was transferred into the reaction chamber and inoculated with 200mL of acclimation bacterial solution. Temperature and stirring speed were precisely controlled by a data acquisition and control unit. During the reaction, samples were taken every 6 hours to analyze the metal ion concentration, pH value, and ORP value in the leachate.

[0108] 4. Experimental Results:

[0109] During the 30-hour reaction period, the pH value fluctuated between 2.0 and 2.4, slightly higher than in Example 1. The ORP value gradually increased from an initial value of approximately 400 mV to approximately 550-600 mV, lower than the ORP value in Example 1, indicating that Fe... 3+ / Fe 2+ The system has relatively weak oxidation capacity. The changes in the concentrations of nickel, cobalt, and lithium ions in the leachate over time are shown in Table 2.

[0110] Table 2

[0111] As shown in Table 2, after 30 hours of pure microbial leaching, the leaching rates of lithium, cobalt, nickel, and manganese reached 82.90%, 78.80%, 76.44%, and 78.86%, respectively. Compared with Example 1, the metal leaching rate of the pure microbial leaching method was significantly lower, indicating that the passivation layer on the surface of the cathode material and Fe... 3+ Insufficient regeneration efficiency has significantly limited the leaching process.

[0112] Table 3 summarizes the main performance indicators of Example 1 and Comparative Example 1 under a reaction time of 30 h.

[0113] Table 3

[0114] *Note: The electrochemical portion of the total energy consumption is calculated based on a voltage of 0.6V, an average current of 0.5A, 30 hours, and 200g of black powder; the stirring / temperature control portion is an estimate.

[0115] As shown in Table 3, the microbial-electrochemical coupled leaching method for metals in spent lithium-ion battery cathode materials provided by this invention has a significant advantage in leaching efficiency compared to the pure microbial leaching method. The leaching rates of lithium, cobalt, nickel, and manganese increased by 16.56%, 20.14%, 21.87%, and 20.30%, respectively. This demonstrates that the micro-electric field effectively activates the passivation layer in situ and promotes the extraction of Fe... 2+ The synergistic effect of electrochemical regeneration can effectively overcome the bottleneck problems faced by pure bioleaching. A high ORP value directly reflects the Fe content in the coupled system. 3+ The concentration is maintained at a high level, thus providing continuous oxidation power. Although additional electrochemical energy consumption is introduced, the electrochemical energy consumption of this invention is controllable and more environmentally friendly compared to the costs and environmental impacts of strong oxidants (such as H2O2) consumed in conventional hydrometallurgy. For example, conventional H2SO4 / H2O2 leaching methods may require higher acid concentrations and H2O2 consumption to achieve similar leaching rates, while also incurring higher costs for subsequent wastewater treatment. This invention achieves an optimized balance between energy consumption and leaching efficiency through a low-voltage, low-current operating mode.

[0116] Furthermore, this invention demonstrates a high degree of integration and reliability in its system design. The acid-resistant reaction chamber, made of PTFE or PVC, exhibits excellent chemical inertness and mechanical strength under harsh acidic environments, ensuring long-term stable operation of the system. The selection of titanium mesh anode and graphite cathode materials in the micro-electric field generating unit, combined with a precise electrode spacing control mechanism, ensures the high efficiency and uniformity of the electrochemical reaction. A high-precision constant-voltage DC power supply guarantees the stability of the applied electric field, while the integration of a magnetic stirring device and temperature, pH, and ORP monitoring modules enables precise control and real-time feedback of reaction conditions, providing a solid foundation for the optimization and automation of the entire process.

[0117] In a more specific application scenario, this system can be used in recycling plants processing tens of thousands of tons of waste lithium-ion battery cathode materials annually. At this scale, the reaction chamber volume can be expanded to 500L, and production capacity can be increased by connecting multiple reaction units in parallel. The system, through a central data acquisition and control unit, enables centralized monitoring and intelligent scheduling of all reaction units. For example, when the pH value in a reaction chamber deviates from the set range, the control unit can automatically trigger the addition of a small amount of acid or alkali solution; when the ORP value is too low, the applied voltage can be adjusted appropriately to accelerate Fe production. 2+ Electrochemical regeneration. All pipes, valves, pumps, etc., that come into contact with materials are made of acid-resistant materials (such as PP, PE, PTFE, titanium alloys, etc.) to ensure leak-free and long-life operation of the entire process.

[0118] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A system for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials, characterized in that, include: The system comprises a reaction chamber, a micro-electric field generating unit, an external constant-voltage DC power supply, a magnetic stirring device, a temperature control monitoring module, a pH monitoring module, a redox potential monitoring module, and a data acquisition and control unit. The micro-electric field generating unit, installed inside the reaction chamber, consists of an anode and a cathode, with the distance between them fixed by a mechanical locking mechanism. Both the anode and cathode are connected to the external constant-voltage DC power supply via sealed electrode leads. The magnetic stirring device includes a magnetic stirring platform and a magnetic stir bar. The magnetic stirring platform is installed at the bottom of the reaction chamber, and the magnetic stir bar is placed inside the reaction chamber. A heating device is integrated at the bottom of the magnetic stirring platform.

2. The system for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to claim 1, characterized in that, The main body of the reaction chamber is selected from polytetrafluoroethylene or polyvinyl chloride; the effective volume of the reaction chamber is 1-500L; the inner surface roughness R of the reaction chamber is... a <0.4μm.

3. The system for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to claim 1, characterized in that, The anode is a porous titanium mesh; the cathode is a graphite plate; the distance between the anode and the cathode is 2-5 cm; the electrode leads are selected from pure platinum wire or copper wire coated with polytetrafluoroethylene.

4. The system for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to claim 4, characterized in that, The porous titanium mesh has a porosity of 40%-50% and a mesh size of 1mm×1mm-2mm×2mm; the graphite plate is sized to form a uniform electric field distribution with the anode, and the thickness of the graphite plate is 5-10mm.

5. The system for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to claim 1, characterized in that, The rated output voltage of the external constant voltage DC power supply is 0-10V, and the rated output current range is 0-5A.

6. A method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials, characterized in that, The process includes the following steps: placing waste lithium battery cathode black powder in water and stirring it evenly to obtain a suspension slurry; placing the suspension slurry in the reaction chamber of the microbial-electrochemical coupling leaching system for metals in waste lithium battery cathode materials as described in any one of claims 1-5; inoculating the reaction chamber with a solution of *Thiobacillus ferrooxidans*; controlling the temperature, pH, and oxidation-reduction potential of the reaction system through a temperature control monitoring module, a pH monitoring module, an oxidation-reduction potential monitoring module, and a data acquisition and control unit; stirring the suspension slurry with a magnetic stirrer driven by the magnetic stirring platform; simultaneously, applying a micro-electric field to the suspension slurry continuously through an external constant voltage DC power supply to carry out the leaching reaction; and performing solid-liquid separation after the reaction to obtain a leachate and residue containing lithium ions, cobalt ions, nickel ions, and manganese ions.

7. The method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to claim 6, characterized in that, The particle size of the waste lithium battery cathode black powder is 45-60μm.

8. The method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to claim 6, characterized in that, The mass ratio of the waste lithium battery cathode black powder to water is 1:(5-15).

9. The method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to claim 6, characterized in that, The viable cell concentration of the *Acidithiobacillus acidophilus* bacterial suspension was 1.0 × 10⁻⁶. 8 -1.0×10 10 The inoculum size is 5-15% of the total volume of the suspension slurry, with an inoculum size of 1 / mL.

10. The method for microbial-electrochemical coupling leaching of metals from waste lithium battery cathode materials according to claim 6, characterized in that, The temperature of the reaction system is 28-32℃; the pH of the reaction system is 1.8-2.5; the redox potential is 650-700mV; the stirring speed is 100-300rpm; the external constant voltage DC power supply applies a micro electric field by outputting a DC voltage of 0.3-0.8V; the leaching reaction time is 24-48h.

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