A recycling process for valuable metals from spent lithium batteries

Abstract

This invention relates to the field of metal material recycling technology and discloses a recycling process for valuable metals from waste lithium batteries. The process includes: grinding and activating waste lithium battery cathode powder, endogenous residual carbon, and pyrite particles to induce lattice distortion and construct a micro-couple network in the cathode powder; stabilizing and adjusting the resulting activated powder in deionized water to constrain the release rate of the redox potential at the solid-liquid interface using a low-ion concentration environment; and adjusting the flow rate of the reducing agent in the sulfuric acid leaching system to maintain the redox potential within the range where manganese is sparingly soluble. This invention utilizes a potential release buffer mechanism to suppress abrupt changes in the interface potential, ensuring that the leaching process is within the thermodynamically stable region of manganese. While extracting lithium, nickel, and cobalt, it achieves in-situ solid-phase retention of manganese, effectively reducing the impurity removal load in subsequent processes.

Description

Technical Field

[0001] This invention belongs to the field of metal material recycling technology, and in particular relates to a recycling process for valuable metals from waste lithium batteries. Background Technology

[0002] Current recycling processes for valuable metals from spent lithium batteries involve the targeted extraction of nickel, cobalt, manganese, and lithium from the battery cathode powder. The mainstream recycling method currently employs hydrometallurgical processes, utilizing acid and reducing agents to disrupt the crystal structure of the material, allowing the metal elements to enter the liquid phase. Due to the similar thermodynamic characteristics of the multi-metal components in a strong acid environment, existing processes exhibit indiscriminate co-leaching, leading to an increased load on subsequent impurity removal and extraction separation. The industry has attempted to introduce mechanochemical activation to improve reaction kinetics, but when the activated powder comes into contact with a high-conductivity electrolyte, its internal in-situ microcouple generates transient discharge. This physical discharge process causes fluctuations in the local redox potential at the solid-liquid interface, breaking down the insoluble boundary of manganese, causing the manganese element, which should have remained in the solid phase, to undergo reduction and dissolution.

[0003] In addition to the physical limitations of the pretreatment stage, the regulation of the chemical reaction process in the leaching stage is also insufficient. For example, Chinese invention patent application CN119082491A discloses a method for separating and recovering valuable metal elements and regenerating cathode materials from waste lithium-ion batteries. It uses a low eutectic solvent combined with mechanochemical activation to achieve metal leaching. Under complex working conditions, this type of process relies on the complexation equilibrium between organic acid anions and metal ions to achieve phase separation. It is difficult to overcome the problem of disordered discharge at the moment of solid-liquid contact caused by the release of internal energy induced by mechanical activation. Due to the lack of physical damping for the redox potential fluctuation caused by the discharge on the surface of the material, when processing mixed raw materials with fluctuating components, the local potential at the solid-liquid interface can easily break down the insoluble boundary of manganese, leading to the reduction and dissolution of manganese.

[0004] Therefore, how to utilize the intrinsic components of waste batteries to reconstruct the internal energy state of the materials and, in conjunction with a physical damping mechanism, suppress surface discharge to achieve metal gradient dissolution, becomes the technical problem to be solved by this invention. Summary of the Invention

[0005] This invention provides a process for recycling valuable metals from waste lithium batteries, comprising the following steps: Step 101: The material to be processed, which includes waste lithium battery cathode powder, endogenous residual carbon and pyrite particles, is fed into a grinding equipment for mechanochemical activation treatment. High-energy mechanical shear force is applied to induce lattice distortion and slip in the waste lithium battery cathode powder, and the endogenous residual carbon and pyrite particles are forced to be pressed and embedded into the solid cleavage surface generated by the waste lithium battery cathode powder. In order to construct a micro-couple network system with electronic conduction capability in situ inside the material to be processed, an activated powder carrying a preset lattice activation energy is obtained. Step 102: The activated powder is put into deionized water with a conductivity of no more than 5 μS / cm for stabilization and slurry preparation. The low ion concentration environment of the deionized water is used to construct a potential release buffer layer at the solid-liquid interface of the activated powder. The potential release buffer layer constrains the potential change rate of the microcouple network system inside the activated powder when it comes into contact with the electrolyte, so that the lattice activation energy carried by the activated powder is released slowly, and a leaching base material with the redox potential amplitude in a quasi-steady state is obtained. Step 103: Add sulfuric acid solution with a concentration of 1.5 mol / L to 2.5 mol / L to the leaching base material for selective leaching treatment. During the leaching process, monitor the redox potential and pH value of the leaching base material in real time. Adjust the supply flow rate of the reducing agent dynamically according to the deviation between the real-time measured value of the redox potential and the target potential. Force the redox potential to be constrained within the range of 0.6V to 0.8V, which is the potential range of the insoluble phase of manganese. While allowing lithium, nickel and cobalt elements in the waste lithium battery cathode powder to dissolve into the liquid phase, manganese elements are retained in the leaching residue in the form of solid insoluble matter.

[0006] Preferably, step 101 further includes the following sub-steps: Step 1011, controlling the mixing mass ratio of waste lithium battery cathode powder, endogenous residual carbon and pyrite particles to 100:2 to 5:1 to 3, to ensure that pyrite particles form discretely distributed active sites on the surface of waste lithium battery cathode powder; Step 1012, setting the grinding media filling rate of the grinding equipment to 55% to 65%, the rotation speed to 400 r / min to 600 r / min, and the processing time to 30 min to 60 min.

[0007] Preferably, in step 103, the pH value is controlled within the range of 1.0 to 2.0 during the leaching process; the reducing agent is hydrogen peroxide solution, which is used to directionally reduce the high-valence cobalt element in the waste lithium battery cathode powder to the low-valence cobalt ion that is easily soluble in sulfuric acid solution under the constraint of redox potential, while keeping the manganese element as a high-valence insoluble oxide.

[0008] Preferably, in step 103, the reaction temperature of the selective leaching treatment is set to 60°C to 80°C, and the stirring speed is 300 r / min to 500 r / min. After the selective leaching treatment is completed, the reaction system is subjected to solid-liquid separation to obtain a leaching solution rich in lithium, nickel, and cobalt ions and a leaching residue rich in manganese, thereby achieving the initial dissociation of transition metals in a single leaching section.

[0009] Preferably, the process further includes step 1031: adding an extractant to the leachate for multi-stage continuous solvent extraction to sequentially separate and extract cobalt, nickel and lithium elements from the leachate; since step 103 achieves in-situ retention of manganese elements in the solid phase, the manganese ion mass concentration in the leachate is less than 0.05 g / L, reducing the manganese removal load of the subsequent extraction stage.

[0010] Preferably, the process further includes step 1032: washing the leaching residue multiple times and drying it with hot air to obtain a manganese-rich recovery product; the mass fraction of manganese in the manganese-rich recovery product is not less than 25%, and the total mass fraction of residual lithium, nickel and cobalt impurities in the manganese-rich recovery product is less than 1%, which can be used as a manganese source supplement for the preparation of ternary precursor materials.

[0011] Preferably, in step 101, the particle size of the pyrite particles is controlled between 30 μm and 50 μm, and the endogenous residual carbon is the coating carbon layer component that falls off during the recycling pretreatment stage of the waste lithium battery negative electrode material; the pyrite particles are used as a micro-current conduction medium to synergistically enhance the electron migration efficiency inside the waste lithium battery positive electrode powder with the endogenous residual carbon.

[0012] Preferably, in step 103, the supply flow rate of the reducing agent is controlled by an automatic regulating valve based on the deviation signal between the redox potential and the lower threshold of 0.6V; when the redox potential shows a decreasing trend and approaches 0.6V, the automatic regulating valve reduces the supply flow rate of the reducing agent to prevent the potential from breaking through the potential range of the insoluble phase of manganese, which would cause manganese to dissolve.

[0013] Preferably, the deionized water containing heat energy generated in step 102 is cooled to room temperature by a heat exchanger and then recycled back to the slurry preparation process of the material to be treated in step 101 or the leaching residue washing process in step 1032, thereby realizing the closed-loop recycling of water resources and waste heat energy in the recycling process.

[0014] Compared with existing technologies, the recycling process for valuable metals from waste lithium batteries in this invention has the following advantages: 1. In the recycling of valuable metals from waste lithium batteries, the low ionic conductivity of deionized water is used as a physical damper to suppress the discharge intensity of the in-situ microcouple inside the activated powder when it comes into contact with the electrolyte. This prevents the uncontrolled drop in local redox potential at the solid-liquid interface, thus confining the leaching process within the insoluble phase region of manganese. While extracting lithium, nickel, and cobalt, manganese is retained in solid form. This mechanism not only cuts off the dissolution path of manganese ions at the source but also reduces the load on subsequent solvent extraction to remove manganese, making phase separation in complex multi-metal coexistence systems more accurate.

[0015] 2. By relying on high-energy shear force to induce slip and distortion in the lattice of the cathode powder, the endogenous residual carbon and pyrite particles are forced to intercalate into the solid-phase cleavage plane and construct a closely contacted conductive path. This transforms the endogenous components in the raw materials from chemically inert to electrochemically active. This energy pre-injection method replaces the traditional system's dependence on external reducing agents such as hydrogen peroxide, significantly reducing the consumption of external chemical reagents and reducing the operating cost of the valuable metal recovery process.

[0016] 3. Based on the feedback loop between mechanical specific energy input and leaching characteristics, and with dynamic acid addition to maintain the stability of the system's redox potential, the process scheme is adaptable to raw materials with different metal ratios. By reconstructing the solid-phase reaction starting point through physical and mechanical energy, the constraint of interfacial mass transfer rate on metal dissolution kinetics during liquid-phase leaching is overcome, thereby improving the process robustness under complex operating conditions. Attached Figure Description

[0017] Figure 1 This is a flow chart of the process for activating and selectively leaching valuable metals from waste lithium batteries according to the present invention; Figure 2 This is a timing diagram of the mechanochemical activation of the positive electrode powder and the construction of the microcouple network in this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0019] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0020] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0021] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0022] A recycling process for valuable metals from spent lithium batteries includes the following steps: Step 101: The material to be processed, which includes waste lithium battery cathode powder, endogenous residual carbon and pyrite particles, is fed into a grinding equipment for mechanochemical activation treatment. High-energy mechanical shear force is applied to induce lattice distortion and slip in the waste lithium battery cathode powder, and the endogenous residual carbon and pyrite particles are forced to be pressed and embedded into the solid cleavage surface generated by the waste lithium battery cathode powder. In order to construct a micro-couple network system with electronic conduction capability in situ inside the material to be processed, an activated powder carrying a preset lattice activation energy is obtained. Step 102: The activated powder is put into deionized water with a conductivity of no more than 5 μS / cm for stabilization and slurry preparation. The low ion concentration environment of the deionized water is used to construct a potential release buffer layer at the solid-liquid interface of the activated powder. The potential release buffer layer constrains the potential change rate of the microcouple network system inside the activated powder when it comes into contact with the electrolyte, so that the lattice activation energy carried by the activated powder is released slowly, and a leaching base material with the redox potential amplitude in a quasi-steady state is obtained. Step 103: Add sulfuric acid solution with a concentration of 1.5 mol / L to 2.5 mol / L to the leaching base material for selective leaching treatment. During the leaching process, monitor the redox potential and pH value of the leaching base material in real time. Adjust the supply flow rate of the reducing agent dynamically according to the deviation between the real-time measured value of the redox potential and the target potential. Force the redox potential to be constrained within the range of 0.6V to 0.8V, which is the potential range of the insoluble phase of manganese. While allowing lithium, nickel and cobalt elements in the waste lithium battery cathode powder to dissolve into the liquid phase, manganese elements are retained in the leaching residue in the form of solid insoluble matter.

[0023] Preferably, step 101 further includes the following sub-steps: Step 1011, controlling the mixing mass ratio of waste lithium battery cathode powder, endogenous residual carbon and pyrite particles to 100:2 to 5:1 to 3, to ensure that pyrite particles form discretely distributed active sites on the surface of waste lithium battery cathode powder; Step 1012, setting the grinding media filling rate of the grinding equipment to 55% to 65%, the rotation speed to 400 r / min to 600 r / min, and the processing time to 30 min to 60 min.

[0024] Preferably, in step 102, the solid-liquid ratio of the activated powder to deionized water is 1:3 g / mL to 1:5 g / mL, and the stabilization and slurry conditioning time is 15 min to 25 min; during the stabilization and slurry conditioning process, the potential release law of the activated powder satisfies the following relationship: ,in, ΔE is the potential release coefficient, ΔE is the difference in oxidation-reduction potential of the activated powder at the start and end of the slurry preparation, Δt is the slurry preparation time, and σ is the conductivity of deionized water. The potential release coefficient is controlled within a preset range by adjusting the slurry preparation time.

[0025] Preferably, in step 103, the pH value is controlled within the range of 1.0 to 2.0 during the leaching process; the reducing agent is hydrogen peroxide solution, which is used to directionally reduce the high-valence cobalt element in the waste lithium battery cathode powder to the low-valence cobalt ion that is easily soluble in sulfuric acid solution under the constraint of redox potential, while keeping the manganese element as a high-valence insoluble oxide.

[0026] Preferably, in step 103, the reaction temperature of the selective leaching treatment is set to 60°C to 80°C, and the stirring speed is 300 r / min to 500 r / min. After the selective leaching treatment is completed, the reaction system is subjected to solid-liquid separation to obtain a leaching solution rich in lithium, nickel, and cobalt ions and a leaching residue rich in manganese, thereby achieving the initial dissociation of transition metals in a single leaching section.

[0027] Preferably, the process further includes step 1031: adding an extractant to the leachate for multi-stage continuous solvent extraction to sequentially separate and extract cobalt, nickel and lithium elements from the leachate; since step 103 achieves in-situ retention of manganese elements in the solid phase, the manganese ion mass concentration in the leachate is less than 0.05 g / L, reducing the manganese removal load of the subsequent extraction stage.

[0028] Preferably, the process further includes step 1032: washing the leaching residue multiple times and drying it with hot air to obtain a manganese-rich recovery product; the mass fraction of manganese in the manganese-rich recovery product is not less than 25%, and the total mass fraction of residual lithium, nickel and cobalt impurities in the manganese-rich recovery product is less than 1%, which can be used as a manganese source supplement for the preparation of ternary precursor materials.

[0029] Preferably, in step 101, the particle size of the pyrite particles is controlled between 30 μm and 50 μm, and the endogenous residual carbon is the coating carbon layer component that falls off during the recycling pretreatment stage of the waste lithium battery negative electrode material; the pyrite particles are used as a micro-current conduction medium to synergistically enhance the electron migration efficiency inside the waste lithium battery positive electrode powder with the endogenous residual carbon.

[0030] Preferably, in step 103, the supply flow rate of the reducing agent is controlled by an automatic regulating valve based on the deviation signal between the redox potential and the lower threshold of 0.6V; when the redox potential shows a decreasing trend and approaches 0.6V, the automatic regulating valve reduces the supply flow rate of the reducing agent to prevent the potential from breaking through the potential range of the insoluble phase of manganese, which would cause manganese to dissolve.

[0031] Preferably, the deionized water containing heat energy generated in step 102 is cooled to room temperature by a heat exchanger and then recycled back to the slurry preparation process of the material to be treated in step 101 or the leaching residue washing process in step 1032, thereby realizing the closed-loop recycling of water resources and waste heat energy in the recycling process.

[0032] Example 1: In the continuous hydrometallurgical process for processing multiple batches of waste ternary lithium battery cathode powder with fluctuating composition, the thermodynamic characteristics of the multi-metal components are similar in a strong acid environment. Adding excessive reducing agent disrupts the material's crystal structure, inducing indiscriminate co-leaching of transition metals. The manganese ions entering the liquid phase increase the purification load and reagent consumption of subsequent extraction and separation processes. The primary step to address the aforementioned multi-metal co-leaching obstacle is to feed the waste lithium battery cathode powder, endogenous residual carbon, and pyrite particles with a particle size controlled between 30μm and 50μm into a grinding equipment at a mass ratio of 100:2 to 5:1 to 3. The grinding media filling rate is set to 55% to 65%, and the rotation speed is set to 400r / min to 600r / min. After 30 minutes... The high-energy mechanical shear-controlled grinding equipment, with an output mechanical specific energy ranging from n to 60 minutes, places the input domain between the critical shear stress of lattice slip and the limit of perfect cleavage fracture in waste ternary cathode materials. External mechanical work is preferentially converted into dislocation multiplication and stacking fault displacement energy within solid particles, inhibiting brittle fragmentation of polycrystalline particles along grain boundaries. In this grinding system, the endogenous residual carbon, with its layered graphite microcrystalline structure, extends to form a solid-phase lubrication buffer film with a thickness of 10nm to 50nm at the collision interface between the ball milling media and cathode grains. This buffer film exhibits highly plastic dissipation of high-energy mechanical impact force, converting the normal hard impact force in situ into tangential crystal shear stress and transmitting it to the surface of the cathode material. Thus, in the absence of an external softening liquid medium, the overall dry ball milling process... Under grinding conditions, the ternary cathode crystal and brittle phases such as pyrite were made to overcome the overall fracture limit. The stress shielding mechanism of the carbon-based film enabled a point-to-point transfer of energy to the surface lattice distortion, inducing lattice distortion and slippage in the waste lithium-ion battery cathode powder. This caused the endogenous residual carbon and pyrite particles to be pressed and embedded into the solid-phase cleavage plane, constructing an in-situ micro-couple network system with electronic conductivity. Subsequently, the activated powder carrying the preset lattice activation energy was added to deionized water with a conductivity not exceeding 5 μS / cm at a solid-liquid ratio of 1:3 g / mL to 1:5 g / mL for stabilization and slurry preparation for 15 to 25 minutes. The low ion concentration environment of the deionized water constructed a potential release buffer layer at the solid-liquid interface of the activated powder, resulting in an ultra-low conductivity liquid... The phase environment restricts the supply of opposite-sign compensating ion diffusion flux to the surface of solid particles. The ion mass transfer bottleneck accumulates at the solid-liquid phase interface of the activated powder, forming a high-resistance space charge depletion layer. This cuts off the liquid-side ion conduction pathway of the solid-phase in-situ microcouple closed loop, transforming the transient solid-interface charge transition that occurs on the order of microseconds into a minute-level delayed discharge process constrained by the ion diffusion rate. The specific connection of the surface action path lies in the fact that the preceding mechanical activation process generates a large number of open cleavage microcracks with a depth spanning hundreds of nanometers on the surface of the positive electrode particles. The microcouple network nodes composed of pyrite and residual carbon are exposed and embedded here. Deionized water penetrates and completely fills the interior of these nanoscale open cracks by capillary force, establishing a direct three-phase contact interface with the embedded conductive nodes.

[0033] Because the internal space of the crack is extremely confined and deionized water itself lacks intrinsic free ions, when the solid-state microcouple network attempts to repel electrons into the liquid phase to excite a microsecond-level discharge circuit, the solid-liquid microregions inside the microcrack cannot quickly recruit sufficient cations for local charge neutralization. Therefore, by utilizing the spatial confinement effect of the electric bilayer in the microcrack region, the electronic transition channels of the microcouple are physically locked at the nanoscale. This physical damping constrains the potential change rate of the microcouple network system within the activated powder upon contact with the electrolyte. The potential release law of the activated powder during stabilization and slurry conditioning satisfies the following relationship: ,in, ΔE represents the redox potential difference between the start and end times of slurry preparation, Δt represents the slurry preparation time, and σ represents the conductivity of deionized water. A 50g sample of the same batch of activated powder was added to deionized water at a solid-liquid ratio of 1:4g / mL. An online electrode recorded the potential decay sequence after contact at a sampling rate of 10Hz to establish the actual slurry preparation time in the industrial-grade main reactor. The control unit calculated the real-time first derivative of the potential sequence. The convergence point was determined when the absolute value of the derivative first remained below 2mV / s for 3 consecutive seconds. The extraction was performed from the zero point to convergence. Substituting the potential drop at a given moment into the above relationship, after verifying that the obtained potential release coefficient falls within the target process range, the convergence time is read and multiplied by the equipment volume conversion constant of 1.1 to 1.2 to generate a fixed numerical instruction periodically sent to the main vessel timer to drive the stirring system. The system collects the oxidation-reduction potential difference and adjusts the slurry conditioning time to control the potential release coefficient within the preset range. This mechanism converts the disordered discharge of high-energy solid material in contact with the liquid phase into controlled energy relaxation, redefines the starting point of wet leaching, and obtains the leaching base material with the oxidation-reduction potential amplitude in a quasi-steady state.

[0034] Selective leaching was performed by adding a sulfuric acid solution with a concentration of 1.5 mol / L to 2.5 mol / L to a quasi-steady-state leaching substrate. The reaction temperature was set to 60℃ to 80℃, and the stirring speed was maintained at 300 r / min to 500 r / min. Within this reaction system, a sensor network acquired the slurry pH and redox potential in real time using an online pH meter and an ORP electrode. While maintaining the pH value within the range of 1.0 to 2.0, the control system controlled an automatic regulating valve based on the deviation signal between the real-time measured redox potential and the 0.6V lower threshold. This dynamically adjusted the supply flow rate of hydrogen peroxide solution as a reducing agent. When the redox potential showed a decreasing trend and approached 0.6V, the supply flow rate of the reducing agent was reduced, thus confining the redox potential within the range of 0.6V to 0.8V, the potential range of the sparingly soluble phase of manganese. This dynamic feedback regulation loop solved the problem of... The technical contradiction between excessively high reduction potential leading to the dissolution of large amounts of manganese and insufficient reduction potential resulting in low cobalt and nickel extraction rates is addressed by directionally reducing high-valence cobalt in waste lithium battery cathode powder to low-valence cobalt ions that are easily soluble in sulfuric acid solution. After the above leaching process, the reaction system is connected to a filter press to complete solid-liquid separation. The system outputs a leachate rich in lithium, nickel, and cobalt ions with a manganese ion concentration of less than 0.05 g / L and a leaching residue with a manganese ion mass fraction of not less than 25% and a total residual impurity mass fraction of less than 1%. This achieves the initial dissociation of transition metals in a single leaching stage and the in-situ solid-phase retention of manganese. At the same time, the high-temperature deionized water generated in the stabilization slurry is cooled to room temperature by a heat exchanger and then recycled through a return pipeline for stabilization slurry preparation of the materials to be treated or for multiple washing processes of the leaching residue, forming a closed-loop circulation network of water resources and waste heat energy in the metallurgical recycling process.

[0035] Example 2: When a continuous hydrometallurgical system faces the actual condition that the internal lattice decay of different batches of waste ternary lithium battery cathode powder varies and the residual carbon content fluctuates randomly, a fixed-parameter leaching process can easily lead to runaway redox potential, resulting in a large amount of manganese dissolving into the liquid phase. To address this condition, a 50L jacketed reactor with precise zone temperature control is used. The temperature control accuracy of this reactor is set to ±0.5℃, and an online ORP sensor network with a sampling frequency of 10Hz and a measurement resolution of 1mV is used to acquire the actual redox potential fluctuation data of the slurry. Regarding the core parameter redox potential... The system seeks to balance the in-situ solid-phase retention rate of manganese and the leaching rate of cobalt and nickel by setting the lower limit threshold of the potential. The control system establishes a judgment model based on the Nernst equation and the thermodynamic phase diagram of the lithium manganese oxide system. When the redox potential monitored by the sensor network approaches the critical potential for the transformation of manganese from sparingly soluble manganese dioxide to easily soluble divalent manganese ions, the system reduces the supply flow rate of hydrogen peroxide solution as a reducing agent. For waste lithium battery cathode powder with different leaching characteristics of transition metals, the system uses this judgment model to determine 0.6V as the lower limit threshold of the redox potential, constraining the reaction system to be in the thermodynamically stable region of manganese.

[0036] Based on the above settings, multiple experimental groups and control groups were established for verification. Waste lithium battery cathode powder, endogenous residual carbon, and pyrite particles with a particle size ranging from 30μm to 50μm were selected as raw materials. The first experimental group, corresponding to the lower limit of parameters, was constructed with a mixing mass ratio of 100:2:1, a grinding media filling rate of 55%, a rotation speed of 400 r / min, and a solid-liquid ratio of 1:3 g / mL. The second experimental group, corresponding to the normal median value, was constructed with a mixing mass ratio of 100:3.5:2, a grinding media filling rate of 60%, a rotation speed of 500 r / min, and a solid-liquid ratio of 1:4 g / mL. The third experimental group, corresponding to the absolute upper limit, was constructed with a mixing mass ratio of... The grinding media filling rate was set at 65%, the rotation speed at 600 r / min, and the solid-liquid ratio at 1:5 g / mL. A first control group (containing no pyrite particles) and a second control group (with a redox potential below 0.6 V and no lower limit constraint) were established. During the experiment, sulfuric acid solutions with concentrations ranging from 1.5 mol / L to 2.5 mol / L were added to each group, the pH was maintained between 1.0 and 2.0, the reaction temperature was controlled between 60℃ and 80℃, and stabilization treatment with deionized water with a conductivity not exceeding 5 μS / cm was carried out for 15 to 25 minutes. Relevant parameters were recorded during slurry preparation, and the potential release coefficient was calculated. Its calculation satisfies the formula ,in, ΔE represents the potential release coefficient, ΔE represents the difference in oxidation-reduction potential of the activated powder at the start and end of the slurry preparation, Δt represents the slurry preparation time, and σ represents the conductivity of deionized water. The system limits this coefficient within a preset safety window by adjusting the slurry preparation time.

[0037] Under this verification process, the sensor network recorded high-frequency fluctuations in the original potential signal of the second experimental group, with a signal-to-noise ratio of approximately 20 dB. The low-ion concentration environment of the stabilized slurry treatment provided physical damping, filtering out high-frequency peaks from random potential disturbances caused by the heterogeneity of the powder. The oxidation-reduction potential smoothly entered the target range of 0.6 V to 0.8 V. The detection data after separation showed that the measured manganese ion mass concentrations in the leachate of the first, second, and third experimental groups were 0.041 g / L, 0.028 g / L, and 0.035 g / L, respectively. The measured manganese element mass fraction in the leaching residue was higher than 26.5%, and the measured total mass fraction of residual impurities was lower than 0.8%. The data confirmed that the global parameter range was complete. In-situ solid-phase retention of manganese elements; comparative analysis showed that the first control group, due to the lack of a micro-couple network constructed by pyrite particles, had insufficient activation of the powder lattice, and its measured comprehensive leaching rate of cobalt and nickel was 76.4%, lower than the average leaching level of over 97.2% measured in the experimental group, indicating a synergistic effect between the components; the second control group experienced performance degradation when the redox potential dropped to 0.4V, and the concentration of manganese ions in the liquid phase increased to 4.56g / L, showing a nonlinear deterioration trend after deviating from the optimal window; the data verified that the joint activation and potential boundary control mechanism solves the technical contradiction of multi-metal co-leaching, constrains the extraction path of valuable metals in waste lithium battery cathode powder within a specific physicochemical boundary, and outputs enriched liquid and manganese slag.

[0038] Example 3: When the continuous hydrometallurgical system faces the condition of local reduction demand fluctuations caused by the agglomeration of high-valence transition metals in waste lithium battery cathode powder, the static leaching process with a fixed set value generates a lag in the redox potential response, causing manganese to be reduced and dissolved into the liquid phase. The premise for dealing with this fluctuating condition is to maintain the structural stability of the micro-couple network system on the solid cleavage surface. The system selects waste lithium battery cathode powder, endogenous residual carbon, and pyrite particles and inputs them into the grinding equipment in a preset ratio. The filling rate and rotation speed of the grinding media are set to apply high-energy mechanical shearing. The bypass sampling device periodically extracts solid powder samples and transports them to an X-ray diffractometer. A Cu-Kα radiation source is used to perform step scanning in the 2θ range of 20° to 80°. The data processing unit receives the diffraction pattern sequence, extracts the 003 and 104 characteristic diffraction peaks that characterize the layered structure of the cathode material, separates the diffraction peak broadening effect integral according to the Williamson-Hall plotting method, and calculates the integral that satisfies the relation. Where β is the measured half-width at half-maximum of the diffraction peak, θ is the Bragg diffraction angle, K is the shape factor constant of 0.89, λ is the incident X-ray wavelength of 0.154 nm, and D is the crystallite size. The processing unit fits the slope of the above straight line and outputs a quarter of the slope value as the lattice strain parameter ε to be measured. The analysis instrument extracts the lattice strain parameter of the activated powder. When the lattice strain parameter is determined to be not less than 0.3% and the electron microscope identifies that the average intercalation depth of pyrite particles on the cleavage surface of the waste lithium battery cathode powder is not less than 2 μm, the microcouple network system is confirmed to be completed, and the system outputs the activated powder.

[0039] After the activated powder is obtained and stabilized in deionized water, the control system injects sulfuric acid solution into the slurry and simultaneously starts the hydrogen peroxide solution supply pipeline to initiate the leaching reaction. Within this reaction system, a sensor network collects redox potentials at a sampling frequency of 5Hz to 10Hz. The control unit calculates the difference between the redox potential of the current sampling period and the 0.6V lower threshold, and simultaneously compares the redox potentials of adjacent sampling periods to obtain the slope of the potential change. The internal solidification flow compensation calculation logic of the control unit satisfies the formula... ,in, This represents the real-time adjustable flow rate of the hydrogen peroxide solution. The proportional response coefficient ranges from 5 to 15 (mL / min) / V, and ΔV represents the difference between the redox potential and the lower threshold. The slope damping coefficient represents the slope damping coefficient, which ranges from 1 to 3 (mL / min) / (V / s), and S represents the slope of the potential change. The above proportional response coefficient... With slope damping coefficient The boundary value is derived by combining the constraints of the overall mixing Reynolds number of the reactor under calibration conditions (Re>10000) and the intrinsic rate constant of the hydrogen peroxide reduction decomposition reaction in the leaching system within the range of 60℃ to 80℃. This specific boundary condition matches the physical response time constant of the valve mechanical opening change and the half-life kinetics of transition metal ions in a strong acid system, preventing local concentration overshoot oscillation or depletion of reducing power supply caused by the control gain exceeding the limit. When the redox potential is greater than 0.6V and the slope of the potential change is negative, the control unit calculates and outputs a decreasing flow control pulse in real time according to the formula, driving the automatic regulating valve to reduce the injection cross-sectional area of ​​the hydrogen peroxide solution. To address the physical time delay problem of fluid mixing and mass transfer in the overall reactor, the control unit integrates and runs the Smith predictor compensation algorithm to calculate the hydrodynamic transport time required for the reducing agent to flow through the online ORP sensor and the chemical kinetic half-life of hydrogen peroxide decomposition. The time constant is used as a pure time lag constant in the algorithm model to offset the detection phase lag. At the same time, the output of the automatic regulating valve is physically connected to a multi-point high-pressure spray ring pipe evenly distributed around the inner wall of the main reactor. The regulated hydrogen peroxide solution is injected into the slurry at multiple points in a micron-level atomized form. Through the synergy of spatially uniform dosing and time-axis prediction compensation algorithm, the potential detection overshoot caused by the mass transfer lag of the reaction system is overcome. This flow adaptive control loop reduces the kinetic energy of the reducing agent injection before the redox potential approaches the critical threshold. The control logic suppresses the potential inertial drop caused by the accumulation of hydrogen peroxide solution in the liquid phase, so that the redox potential of the reaction system converges within the safe range of 0.6V to 0.8V. The data output by the separation device shows that the cobalt and nickel extraction rate in the leaching solution reaches the preset process index, and the manganese element in the leaching residue remains in a solid phase. The multi-dimensional parameter linkage adjustment method eliminates the dependence on manual experience and establishes an automated separation control chain for directional reduction in a multi-metal coexistence system.

[0040] Example 4: When the continuous hydrometallurgical system is faced with the feeding of waste ternary lithium battery cathode powder of unknown origin, different degrees of attenuation of the powder correspond to specific initial mechanical shear energy baselines. Before continuous feeding, the system starts a pre-calibration program, extracts a 1kg powder sample and places it in a test grinding equipment, mixes it with endogenous residual carbon and pyrite particles according to a preset ratio, sets the rotation speed gradient from 300r / min to 600r / min in increments of 50r / min for pre-grinding, extracts a subsample in each step interval and puts it into deionized water to measure the initial open circuit potential change rate, compares the minimum speed critical coordinate where the open circuit potential change rate tends to converge and the lattice strain parameter reaches a preset threshold, multiplies it by the engineering conversion factor used to calculate the equipment volume scaling ratio to generate the baseline rotation speed of the formal production equipment, and the control unit receives the baseline rotation speed as the initial operating parameter to start the continuous feeding and grinding process.

[0041] For the reduction stage of the powder leaching process, the control unit initiates an offline titration calibration program to establish a feedback reference zero point for the dynamic adjustment of the hydrogen peroxide solution. A standard volume of slurry sample after preparation is extracted and placed in a constant-temperature water bath titration tank. Sulfuric acid and hydrogen peroxide solutions are injected into the slurry at a fixed flow rate under constant stirring speed. Simultaneously, the redox potential of the slurry and the real-time dissolved concentration of manganese ions in the liquid phase are recorded, and the derivative of manganese ion concentration with respect to time is calculated. The derivative satisfies the formula ,in, The figure represents the manganese ion dissolution rate, ΔC represents the manganese ion concentration difference between adjacent sampling points, and Δτ represents the sampling time interval. The system then uses the real-time acquired redox potential values ​​as the x-axis and the calculated manganese ion dissolution rate as the y-axis. A two-dimensional correlation mapping curve is plotted using the vertical axis. When the control unit detects that the vertical axis of the curve exceeds the preset threshold of 0.005 g / (L·s), it is determined that the system has broken through the interface passivation resistance and officially entered the irreversible dissolution period of accelerated collapse of the lithium manganese oxide lattice. The system locates the potential coordinate corresponding to the dissolution rate increment exceeding the preset threshold on the correlation mapping curve, extracts the potential coordinate, and adds a compensation constant to generate the lower limit threshold for monitoring feedback from the control unit. The control system drives the automatic regulating valve in the main reactor to adjust the flow rate of hydrogen peroxide solution based on the lower limit threshold, and outputs leachate and leaching residue.

[0042] Example 5: When the continuous hydrometallurgical system encounters waste lithium battery cathode powder with varying degrees of surface passivation, the control unit initiates a pre-baseline calibration program before feeding. A powder sample is extracted, and internal residual carbon and pyrite particles are mixed according to a preset mixing mass ratio to initiate pre-grinding. Activated powder is obtained and added to deionized water. Multiple parallel slurry conditioning time gradients are set from 5 min to 30 min, with 5-min increments, to sequentially initiate stabilization slurry conditioning. At the end of each interval, the actual conductivity of the deionized water system is measured. Based on the difference between the actual conductivity and the redox potential, the corresponding potential release coefficient is calculated. Simultaneously, the convergence time for the system's redox potential to reach a constant amplitude under the current state is recorded. A nonlinear relationship curve between the potential release coefficient and the convergence time is fitted. The stationary point coordinate interval where the absolute value of the slope drops sharply and the convergence time tends to a constant is extracted from the curve. The potential release coefficient value corresponding to this coordinate interval is input into the control unit and determined as the safe boundary for the potential release coefficient of this specific batch of activated powder. The system is calibrated to meet the operating benchmark for the initial state differences of different batches of materials.

[0043] When establishing the baseline for hydrogen peroxide solution flow feedback control, the system initiates an offline parameter optimization program to calibrate the initial reference value of the slope damping coefficient. A sulfuric acid solution with a concentration of 1.5 mol / L to 2.5 mol / L is prepared in the reactor and heated to a reaction temperature of 60°C to 80°C. After injecting a measured amount of quasi-steady-state leaching substrate, a step signal for hydrogen peroxide solution injection is applied at a constant flow rate step size. Within this reaction system, a sensor network synchronously collects the redox potential and the concentration of manganese ions in the liquid phase. The control unit obtains the data based on the comparison of data from adjacent sampling periods. The potential change slope is taken to lock the critical point of the potential change slope corresponding to the manganese ion concentration crossing the lower limit threshold of 0.05 g / L. A three-dimensional mapping data matrix containing the flow step increment, potential change slope and dissolution concentration is constructed. The safe data range where the manganese ion concentration does not exceed the lower limit threshold and the potential change slope remains negative is extracted. The average ratio of a specific flow step increment to the corresponding potential change slope is calculated. The absolute value of the average ratio is written into the control unit and set as the initial reference value of the slope damping coefficient, driving the dynamic feedback adjustment loop to adapt to the actual dissolution characteristics of metal ions.

[0044] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A process for recycling valuable metals from waste lithium batteries, characterized in that, Includes the following steps: Step 101: The material to be processed, which includes waste lithium battery cathode powder, endogenous residual carbon and pyrite particles, is fed into a grinding equipment for mechanochemical activation treatment. High-energy mechanical shear force is applied to induce lattice distortion and slip in the waste lithium battery cathode powder, and the endogenous residual carbon and pyrite particles are forced to be pressed and embedded into the solid cleavage surface generated by the waste lithium battery cathode powder. In order to construct a micro-couple network system with electronic conduction capability in situ inside the material to be processed, an activated powder carrying a preset lattice activation energy is obtained. Step 102: The activated powder is put into deionized water with a conductivity of no more than 5 μS / cm for stabilization and slurry preparation. The low ion concentration environment of the deionized water is used to construct a potential release buffer layer at the solid-liquid interface of the activated powder. The potential release buffer layer constrains the potential change rate of the microcouple network system inside the activated powder when it comes into contact with the electrolyte, so that the lattice activation energy carried by the activated powder is released slowly, and a leaching base material with the redox potential amplitude in a quasi-steady state is obtained. Step 103: Add sulfuric acid solution with a concentration of 1.5 mol / L to 2.5 mol / L to the leaching base material for selective leaching treatment. During the leaching process, monitor the redox potential and pH value of the leaching base material in real time. Adjust the supply flow rate of the reducing agent dynamically according to the deviation between the real-time measured value of the redox potential and the target potential. Force the redox potential to be constrained within the range of 0.6V to 0.8V, which is the potential range of the insoluble phase of manganese. While allowing lithium, nickel and cobalt elements in the waste lithium battery cathode powder to dissolve into the liquid phase, manganese elements are retained in the leaching residue in the form of solid insoluble matter.

2. The recycling process for valuable metals from waste lithium batteries according to claim 1, characterized in that, Step 101 further includes the following sub-steps: Step 1011, controlling the mixing mass ratio of waste lithium battery cathode powder, endogenous residual carbon and pyrite particles to 100:2 to 5:1 to 3, to ensure that pyrite particles form discretely distributed active sites on the surface of waste lithium battery cathode powder. Step 1012: Set the grinding media filling rate of the grinding equipment to 55% to 65%, the rotation speed to 400 r / min to 600 r / min, and the processing time to 30 min to 60 min.

3. The recycling process for valuable metals from waste lithium batteries according to claim 1, characterized in that, In step 103, the pH value during the leaching process is controlled within the range of 1.0 to 2.0; the reducing agent is hydrogen peroxide solution, which is used to directionally reduce the high-valence cobalt element in the waste lithium battery cathode powder to the low-valence cobalt ion that is easily soluble in sulfuric acid solution under the constraint of redox potential, while keeping the manganese element as a high-valence insoluble oxide.

4. The recycling process for valuable metals from waste lithium batteries according to claim 1, characterized in that, In step 103, the reaction temperature of the selective leaching treatment is set to 60°C to 80°C, and the stirring speed is 300 r / min to 500 r / min. After the selective leaching treatment is completed, the reaction system is subjected to solid-liquid separation to obtain a leaching solution rich in lithium, nickel and cobalt ions and a leaching residue rich in manganese, thereby achieving the initial dissociation of transition metals in a single leaching section.

5. The recycling process for valuable metals from waste lithium batteries according to claim 4, characterized in that, The process further includes step 1031: adding an extractant to the leachate for multi-stage continuous solvent extraction to sequentially separate and extract cobalt, nickel and lithium elements from the leachate; since step 103 achieves in-situ retention of manganese elements in the solid phase, the manganese ion mass concentration in the leachate is less than 0.05 g / L, reducing the manganese removal load of the subsequent extraction stage.

6. The recycling process for valuable metals from waste lithium batteries according to claim 4, characterized in that, The process further includes step 1032: washing the leaching residue multiple times and drying it with hot air to obtain a manganese-rich recovery product; the mass fraction of manganese in the manganese-rich recovery product is not less than 25%, and the total mass fraction of residual lithium, nickel and cobalt impurities in the manganese-rich recovery product is less than 1%, which can be used as a manganese source supplement for the preparation of ternary precursor materials.

7. The recycling process for valuable metals from waste lithium batteries according to claim 1, characterized in that, In step 101, the particle size of the pyrite particles is controlled between 30 μm and 50 μm, and the endogenous residual carbon is the coating carbon layer component that falls off during the recycling pretreatment stage of the waste lithium battery negative electrode material; the pyrite particles are used as a micro-current conduction medium to synergistically enhance the electron migration efficiency inside the waste lithium battery positive electrode powder with the endogenous residual carbon.

8. The recycling process for valuable metals from waste lithium batteries according to claim 1, characterized in that, In step 103, the supply flow rate of the reducing agent is controlled by an automatic regulating valve based on the deviation signal between the redox potential and the lower threshold of 0.6V. When the redox potential shows a decreasing trend and approaches 0.6V, the automatic regulating valve reduces the supply flow rate of the reducing agent to prevent the potential from breaking through the potential range of the insoluble phase of manganese, which would cause manganese to dissolve.

9. The recycling process for valuable metals from waste lithium batteries according to claim 1, characterized in that, The deionized water containing heat energy generated in step 102 is cooled to room temperature by a heat exchanger and then recycled back to the slurry preparation process of the material to be treated in step 101 or the leaching residue washing process in step 1032, thereby realizing the closed-loop recycling of water resources and waste heat energy in the recycling process.

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