Method for reducing and recycling lithium in waste ternary positive electrode by synergistic effect of yeast residue and waste plastic

Abstract

The application discloses a method for reducing and recycling lithium in waste ternary positive electrodes by yeast residue and waste plastics, and belongs to the technical field of resource recycling of waste lithium ion battery positive electrode materials. The method comprises the following steps: mixing waste ternary positive electrode material powder and yeast residue-waste plastic composite reducing agent to obtain a mixture to be calcined; performing cooperative reduction calcination on the mixture to be calcined in an inert atmosphere, a vacuum or a closed atmosphere environment, and obtaining a calcined product after cooling; adding the calcined product into water, and performing carbon dioxide gas carbonation water leaching, solid-liquid separation, obtaining a lithium-containing leaching solution and an Ni, Co and Mn-rich leaching residue. The yeast residue and the waste plastics are used as the composite reducing calcination reducing agent, hydrogen-rich volatile components, light hydrocarbons, nitrogen-containing volatile components, reducing gases and solid-phase carbon components formed by the cooperation of the yeast residue and the waste plastics promote the conversion of lithium in the waste ternary positive electrode material into leachable lithium compounds, and the selective separation of lithium and transition metals is realized through subsequent carbonation water leaching.

Description

Technical Field

[0001] This invention belongs to the field of resource recycling of waste lithium-ion battery cathode materials and co-utilization of solid waste. Specifically, it relates to a method that uses yeast residue and waste plastic as composite reducing agents to co-reduc and roast waste ternary cathode materials, so that the lithium element is preferentially converted into leached lithium salts, and then lithium is recovered through selective leaching. Background Technology

[0002] The number of retired lithium-ion batteries after their service life ends is constantly increasing. Among them, ternary lithium-ion battery cathode materials contain multiple valuable metals such as lithium, nickel, cobalt, and manganese, posing both resource value and environmental risks. During long-term charging, discharging, and dismantling processes, waste ternary cathode materials typically experience structural degradation, changes in metal valence states, and increased surface residues. Direct stockpiling or improper disposal can not only lead to the loss of strategic metal resources such as lithium, nickel, and cobalt, but may also cause heavy metal migration and electrolyte residue pollution. Therefore, establishing efficient, clean, and selective recycling technologies for waste ternary cathode materials is of great significance for improving the recycling rate of lithium resources and reducing the environmental impact of waste batteries.

[0003] Currently, the recovery of valuable metals from waste ternary cathode materials mainly employs two technical routes: hydrometallurgy and pyrometallurgy. Hydrometallurgy typically uses inorganic acids, organic acids, or leaching agents to transfer metal components such as lithium, nickel, cobalt, and manganese into a solution, followed by separation and recovery through precipitation, extraction, and crystallization. It has advantages such as high metal leaching rates and relatively mild reaction conditions, but also suffers from high reagent consumption, heavy wastewater treatment burden, and complex metal separation processes. Pyrometallurgy, on the other hand, enriches valuable metals through high-temperature smelting or heat treatment, offering greater adaptability to raw materials. However, it usually consumes more energy, and lithium tends to enter the slag or flue gas phase, limiting efficient lithium recovery. Therefore, traditional hydrometallurgical and pyrometallurgical processes still have room for improvement in terms of selective lithium recovery, process energy consumption, and environmental friendliness.

[0004] To overcome the shortcomings of traditional hydrometallurgical and pyrometallurgical processes in the selective recovery of lithium, the reduction roasting-selective leaching process has gradually attracted attention. This process typically introduces a reducing agent to disrupt the layered crystal structure of waste ternary cathode materials during roasting, promoting the release of lattice lithium and its conversion into water-soluble or easily leached lithium salts. Simultaneously, transition metals such as nickel, cobalt, and manganese are converted into insoluble low-valence oxides or metallic phases, thus achieving preliminary separation of lithium from other metal components. Existing reduction roasting processes often use graphite, lignite, biomass, or organic solid waste as reducing agents. Traditional carbonaceous reducing agents such as graphite and lignite mainly rely on solid-phase carbothermic reduction, which typically requires high calcination temperatures and long reaction times, and has limited contact efficiency with cathode material particles. While single biomass reducing agents offer advantages such as renewability and wide availability, their pyrolysis behavior is significantly influenced by the raw material composition; some biomass has high oxygen content, easily leading to insufficient effective reducing gas proportions. Furthermore, relying solely on biomass char residue for reduction usually requires high calcination temperatures or large addition amounts, and may introduce significant amounts of ash and impurities, making it difficult to achieve stable and efficient reduction under low-temperature, low-dosage conditions. Therefore, combining different types of reducing agents, utilizing their differences in pyrolysis temperature range, volatile composition, hydrogen-to-carbon ratio, and char residue characteristics to construct a composite reduction system with synergistic effects of gas-phase and solid-phase reduction, could potentially further reduce calcination temperatures and reducing agent dosages, thereby improving the selective recovery efficiency of lithium from waste ternary cathode materials. Summary of the Invention

[0005] This invention aims to design a method for selectively recovering lithium from waste ternary cathode materials by using the synergistic pyrolysis of yeast residue and waste plastics as a composite reducing roasting reducing agent. This method addresses the problems of insufficient effective reducing atmosphere, high roasting temperature, large amount of reducing agent added, and insufficient process controllability and repeatability in the existing reduction roasting process with a single reducing agent, and improves the separation selectivity and recovery rate of lithium.

[0006] The advantage of this invention lies in the synergistic effect of nitrogen-containing volatiles, reducing gases, and solid biochar formed during the pyrolysis of yeast residue, and hydrogen-rich volatiles, light hydrocarbons, and free radical components released during the pyrolysis of waste plastics. This promotes the structural evolution and phase transformation of waste ternary cathode materials, thereby converting lithium in the ternary cathode materials into leached lithium compounds, while transition metals such as Ni, Co, and Mn are mainly retained in the solid phase. Subsequently, in conjunction with subsequent leaching processes, selective recovery of lithium from waste ternary cathode materials can be achieved, reducing the reduction roasting temperature and the amount of reducing agent added, and improving the controllability and repeatability of the recovery process.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for recycling lithium from waste ternary cathode materials by co-reduction of yeast residue and waste plastics, the method comprising the following steps:

[0009] (1) Preparation of waste ternary cathode material powder: Waste ternary lithium-ion batteries are subjected to safe discharge, dismantling, separation, peeling, drying, heat treatment, grinding and sieving to obtain waste ternary cathode material powder;

[0010] (2) Preparation of yeast residue-waste plastic composite reducing agent: yeast residue is washed, dried, crushed and sieved to obtain yeast residue powder; waste plastic is washed, dried, sheared, crushed or crushed to obtain waste plastic particles; the yeast residue powder and waste plastic particles are mixed to obtain yeast residue-waste plastic composite reducing agent;

[0011] (3) Synergistic reduction roasting: The waste ternary cathode material powder obtained in step (1) is mixed with the yeast residue-waste plastic composite reducing agent obtained in step (2) to obtain a mixture to be roasted; then the mixture to be roasted is synergistically reduced roasted in an inert atmosphere, vacuum or closed atmosphere, so that the lithium element in the waste ternary cathode material is converted into leached lithium compounds, while transition metals such as Ni, Co, and Mn are mainly converted into insoluble low-valence oxides or metal phases, and the roasted product is obtained after cooling;

[0012] (4) Selective leaching and lithium salt recovery: The roasted product obtained in step (3) is added to water and carbon dioxide gas is introduced for carbonated water leaching, so that lithium elements preferentially enter the liquid phase; after leaching, solid-liquid separation is performed to obtain lithium-containing leachate and leaching residue rich in Ni, Co and Mn; the obtained lithium-containing leachate is concentrated by evaporation, crystallization, solid-liquid separation and drying to obtain lithium carbonate product.

[0013] Further, step (1) specifically involves: placing the waste ternary lithium-ion battery in a 5-15 wt% sodium sulfate solution for safe discharge for 6-48 h, disassembling and separating it to obtain waste ternary positive electrode sheets, and washing them with deionized water to remove residual electrolyte and soluble impurities from the surface; cutting the obtained positive electrode sheets into 0.5-5 cm sheet-like materials, placing them in deionized water for ultrasonic-assisted peeling, with a solid-liquid ratio of 10-100 g / L, an ultrasonic power of 100-800 W, a treatment temperature of 20-80 ℃, and a treatment time of 10-120 min; the peeled mixture is then sieved, filtered, or centrifuged to remove aluminum foil fragments, and the resulting solid is washed and dried, then heat-treated in air at 400-600 ℃ for 1-5 h to remove residual binder and conductive carbon, and finally ground and sieved to obtain waste ternary positive electrode material powder. Ultrasonic-assisted stripping utilizes cavitation and mechanical vibration to weaken the bond between the positive electrode active material layer and the aluminum foil current collector, allowing the positive electrode material to detach rapidly from the aluminum foil surface. This improves stripping efficiency and reduces aluminum foil entrainment and active material loss. Using deionized water as the stripping medium eliminates the need for strong acids, strong alkalis, or organic solvents, reducing the introduction of impurities and the burden of waste liquid treatment. Furthermore, it provides positive electrode material powder with lower aluminum content and a relatively stable composition for subsequent heat treatment and reduction calcination.

[0014] Further, in step (2), the particle size of the yeast residue powder is 50~100 mesh; the particle size of the waste plastic particles is 0.01~0.55 mm.

[0015] Furthermore, in step (2), the waste plastic is waste polyethylene and / or waste polypropylene.

[0016] Further, in step (2), the mass ratio of the yeast residue powder to the waste plastic particles is 0:10 to 10:0; preferably, the mass ratio of the yeast residue powder to the waste plastic particles is 2:8 to 8:2; more preferably, the mass ratio of the yeast residue powder to the waste plastic particles is 4:6 to 6:4.

[0017] Yeast residue is rich in protein, polysaccharides, and a certain amount of nitrogen-containing organic components. During pyrolysis, it can form carbon-containing solid residues and reducing gaseous products such as CO, H2, and CH4, thus achieving both gas-phase and solid-phase reduction. Waste plastics have high carbon and hydrogen content, and during pyrolysis, they can produce hydrogen-rich hydrocarbon gases and carbonaceous products, which is beneficial to improving the system's reducing capacity. Combining yeast residue with waste plastics utilizes the differences in their composition and pyrolysis behavior to regulate the release process of reducing gases and the amount of solid carbonaceous components generated, thereby enhancing the gas-solid synergistic reduction effect and achieving the synergistic resource utilization of both yeast residue and waste plastics.

[0018] The mass ratio of yeast residue powder to waste plastic granules was set to 0:10 to 10:0 to cover different scenarios of using waste plastic alone, using yeast residue alone, and using both in combination, in order to examine the independent and synergistic effects of the two reducing agents. A preferred mass ratio was 2:8 to 8:2 to avoid the disadvantage of one component being too low to fully utilize the advantages of the combination; a further preferred ratio was 4:6 to 6:4 to maintain a suitable proportion between the solid carbonaceous components produced by the yeast residue and the hydrogen-rich gaseous products produced by the waste plastics. This approach helps to balance the supply, release rate, and duration of reducing products, thereby improving the reduction and conversion degree of the waste ternary cathode material and the subsequent lithium leaching effect.

[0019] Furthermore, in step (3), the mass ratio of the waste ternary cathode material powder to the yeast residue-waste plastic composite reducing agent is 1:0.1~0.3.

[0020] Furthermore, in step (3), the calcination temperature of the synergistic reduction calcination is 450~650 ℃, the heating rate is 10~20 ℃ / min, and the holding time is 20~60 min.

[0021] Further, in step (4), the solid-liquid ratio of the carbonated water leaching is 10~50 g / L, the carbon dioxide gas flow rate is 50~200 mL / min, the leaching temperature is 20~80 ℃, and the leaching time is 0.5~3 h.

[0022] The advantages of this invention compared to existing technologies are as follows: This invention uses yeast residue and waste plastics as composite reducing roasting reducing agents. It utilizes the hydrogen-rich volatiles, light hydrocarbons, nitrogen-containing volatiles, reducing gases, and solid carbon components formed during the synergistic pyrolysis of these two materials during roasting to promote the conversion of lithium in waste ternary cathode materials into leached lithium compounds. Subsequent carbonated water leaching achieves selective separation of lithium from transition metals such as Ni, Co, and Mn. Compared to traditional solid carbonaceous reducing agents such as graphite, activated carbon, and coke, this invention not only relies on solid-phase carbothermal reduction but also utilizes the gaseous reducing components generated by the co-pyrolysis of yeast residue and waste plastics to promote structural destruction of the cathode material, which is beneficial for reducing roasting temperature and shortening reaction time. Compared to single biomass reducing agents, this invention introduces waste polyethylene or waste polypropylene with a high hydrogen-to-carbon ratio to enhance the hydrogen-rich reducing atmosphere in the roasting system, reducing the input of ash and impurities caused by the large addition of yeast residue alone. Compared to single waste plastic reducing agents, this invention utilizes the nitrogen-containing volatiles and solid biochar formed by the pyrolysis of yeast residue to improve the continuity and stability of the reduction process and enhance the selective conversion of lithium. Under preferred conditions, the mass ratio of waste ternary cathode material to composite reducing agent in this invention is 1:0.3, the mass ratio of yeast residue to waste plastic is 6:4, the synergistic reduction roasting temperature is 600 ℃, the heating rate is 10 ℃ / min, and the holding time is 40 min. Subsequently, carbonated water leaching is carried out under the conditions of a solid-liquid ratio of 20 g / L, a carbon dioxide gas flow rate of 100 mL / min, a leaching temperature of 50 ℃, and a leaching time of 2 h, so that lithium preferentially enters the liquid phase, while transition metals such as Ni, Co, and Mn are mainly retained in the solid phase. The resulting lithium-containing leachate can be obtained as lithium carbonate product after evaporation, concentration, crystallization, washing, and drying. This invention has the advantages of wide availability of reducing agent, high degree of co-utilization of solid waste, mild roasting conditions, high selective lithium recovery efficiency, low input of inorganic impurities, and low environmental impact. Attached Figure Description

[0023] Figure 1 A process flow diagram for the co-reduction and recycling of lithium from waste ternary cathode materials using yeast residue and waste plastics;

[0024] Figure 2 The image shows the XRD pattern of the waste ternary cathode material obtained after pretreatment.

[0025] Figure 3 Figure showing the effect of different mass ratios of yeast residue to waste plastic on lithium leaching rate;

[0026] Figure 4 The graph shows the effect of different composite reducing agents and the mass ratio of waste ternary cathode materials on lithium leaching rate.

[0027] Figure 5 The graph shows the effect of different calcination temperatures on lithium leaching rate.

[0028] Figure 6 The graph shows the effect of different roasting times on lithium leaching rate.

[0029] Figure 7 XRD patterns of the calcined product and the carbonated water leaching residue;

[0030] Figure 8 The image shows the XRD pattern of the recovered lithium carbonate product. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0032] The specific steps of the method for recycling lithium from waste ternary cathodes by co-reduction of yeast residue and waste plastics according to the present invention are as follows:

[0033] (1) Preparation of waste ternary cathode material powder: Waste ternary lithium-ion batteries were safely discharged in a 5-15 wt% sodium sulfate solution for 6-48 h. After disassembly and separation, waste ternary cathode sheets were obtained and washed with deionized water to remove residual electrolyte and soluble impurities from the surface. The obtained cathode sheets were cut into 0.5-5 cm pieces and placed in a stripping solution for ultrasonic-assisted stripping. The solid-liquid ratio was 10-100 g / L, the ultrasonic power was 100-800 W, the treatment temperature was 20-80 ℃, and the treatment time was 10-120 min. The stripped mixture was sieved, filtered, or centrifuged to remove aluminum foil fragments. The resulting solid was washed and dried, and then heat-treated in air at 400-600 ℃ for 1-5 h to remove residual binder and conductive carbon. Finally, it was ground and sieved to obtain waste ternary cathode material powder. Figure 2 It can be seen that the obtained powder retains the main crystal phase characteristics of the layered ternary cathode material, indicating that through the pretreatment steps of the present invention, such as discharge, disassembly, ultrasonic-assisted stripping, heat treatment to remove impurities and grinding and sieving, waste ternary cathode material powder suitable for subsequent yeast residue-waste plastic co-reduction roasting can be obtained.

[0034] (2) Preparation of yeast residue-waste plastic composite reducing agent: The yeast residue is washed with deionized water 1-5 times to remove soluble impurities on the surface, then dried at 60-120 °C for 6-24 h, and then pulverized and sieved to obtain yeast residue powder with a particle size of 50-100 mesh; waste polyethylene, waste polypropylene, or a mixture thereof is washed, dried, sheared, crushed or pulverized to obtain waste plastic particles with a particle size of 0.01-0.5 mm. The obtained yeast residue powder and waste plastic particles are mixed at a mass ratio of 1:9-9:1 to obtain the yeast residue-waste plastic composite reducing agent.

[0035] (3) Co-reduction roasting: The waste ternary cathode material powder obtained in step (1) is mixed with the yeast residue-waste plastic composite reducing agent obtained in step (2) to obtain a mixture to be roasted; wherein, the mass ratio of waste ternary cathode material powder to composite reducing agent is 1:0.1~0.3. The mixture to be roasted is placed in a roasting device and co-reduction roasted under an inert atmosphere, vacuum or oxygen-limited atmosphere. The roasting temperature is 450~650 ℃, the heating rate is 10~20 ℃ / min, and the holding time is 20~60 min. Figure 3 It can be seen that the lithium leaching rate first increases and then decreases with the increase of the proportion of yeast residue in the composite reducing agent, indicating that there is a suitable ratio between yeast residue and waste plastic, which can promote lithium conversion through gas-solid synergistic reduction. Figure 4 It can be seen that the lithium leaching rate first increases and then decreases with the increase of the amount of composite reducing agent, indicating that an appropriate amount of reducing agent is beneficial to enhancing the reduction effect, while excessive addition is detrimental to subsequent lithium leaching. Figure 5 It can be seen that the lithium leaching rate first increases and then decreases with increasing calcination temperature, indicating that a suitable temperature is beneficial for enhancing the synergistic reduction of yeast residue and waste plastics and promoting lithium conversion, while excessively high temperatures are detrimental to subsequent leaching. Figure 6 It can be seen that the lithium leaching rate first increases and then slightly decreases with the extension of roasting time, indicating that appropriately extending the roasting time is beneficial to lithium conversion, while further extending the time has limited improvement on the leaching effect. During the roasting process, the yeast residue and waste plastics are co-pyrolyzed to form a gas-solid synergistic reduction system involving hydrogen-rich volatiles, light hydrocarbons, nitrogen-containing volatiles, reducing gases, and solid carbon. This system promotes the structural destruction and phase transformation of the waste ternary cathode material, converting lithium into leached lithium compounds, while transition metals such as Ni, Co, and Mn are mainly converted into insoluble low-valence oxides or metallic phases. After cooling, the roasting product is obtained.

[0036] (4) Selective leaching and lithium salt recovery: The roasted product obtained in step (3) is added to deionized water, and carbon dioxide gas is introduced under stirring conditions to carry out carbonated water leaching, so that the leached lithium compounds in the roasted product are converted and enter the liquid phase; wherein, the solid-liquid ratio is 10~50 g / L, the carbon dioxide gas flow rate is 50~200 mL / min, the leaching temperature is 20~80 ℃, and the leaching time is 0.5~3 h. After leaching, the leaching slurry is filtered, centrifuged or settled to obtain lithium-containing leachate and leaching residue rich in Ni, Co, and Mn, which is then processed by the process. Figure 7 It can be seen that synergistic reduction roasting produces lithium carbonate, Ni, Co, and MnO; after water leaching, the characteristic peak of lithium carbonate disappears, while Ni, Co, and MnO remain in the residue, indicating that lithium and transition metals achieve selective separation. The resulting lithium-containing leachate is then subjected to evaporation concentration, cooling crystallization, solid-liquid separation, and drying to obtain the lithium carbonate product. Figure 8 It can be seen that the diffraction peaks of the recovered product match the standard peaks of lithium carbonate, and no obvious impurity peaks are observed, indicating that the obtained lithium carbonate has good phase purity.

[0037] Example 1

[0038] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials through the co-reduction roasting of yeast residue and waste plastics, specifically including the following steps:

[0039] (1) Preparation of waste ternary cathode material powder: Waste ternary lithium-ion batteries were placed in a 10 wt% sodium sulfate solution for safe discharge for 24 h. After discharge, the batteries were disassembled and separated to obtain waste ternary cathode sheets, which were washed with deionized water to remove residual electrolyte and soluble impurities from the surface. The obtained cathode sheets were cut into sheets of about 2 cm and placed in a stripping solution for ultrasonic-assisted stripping treatment. The solid-liquid ratio was 50 g / L, the ultrasonic power was 500 W, the treatment temperature was 50 ℃, and the treatment time was 60 min. The stripped mixture was filtered to remove aluminum foil fragments. The obtained solid was washed three times with deionized water and dried at 80 ℃ for 12 h. Subsequently, the dried solid was placed in an air atmosphere and heat-treated at 500 ℃ for 3 h to remove residual binder and remove or reduce the conductive carbon content. Finally, the waste ternary cathode material powder was obtained by grinding and sieving.

[0040] (2) Preparation of yeast residue-waste plastic composite reducing agent: The yeast residue was washed three times with deionized water to remove soluble impurities from the surface, then dried at 80 °C for 12 h, and then pulverized and sieved to obtain yeast residue powder with a particle size of 80-100 mesh. Waste polyethylene was washed, dried and pulverized to obtain waste plastic particles with a particle size of 0.1-0.2 mm. The obtained yeast residue powder and waste polyethylene particles were mixed at a mass ratio of 6:4 to obtain the yeast residue-waste plastic composite reducing agent.

[0041] (3) Co-reduction roasting: The waste ternary cathode material powder obtained in step (1) and the yeast residue-waste plastic composite reducing agent obtained in step (2) are mixed at a mass ratio of 1:0.3 to obtain the mixture to be roasted. The mixture to be roasted is placed in a tube furnace and co-reduction roasted under an inert atmosphere. The heating rate is 10 ℃ / min, the roasting temperature is 600 ℃, and the holding time is 40 min. During the roasting process, the yeast residue and waste plastic are co-pyrolyzed to form a gas-solid co-reduction system in which hydrogen-rich volatiles, light hydrocarbons, nitrogen-containing volatiles, reducing gases and solid carbon participate. This promotes the structural destruction and phase transformation of the waste ternary cathode material, so that the lithium element is converted into leached lithium compounds, while transition metals such as Ni, Co, and Mn are mainly converted into insoluble low-valence oxides or metal phases. After roasting, the mixture is cooled to room temperature under an inert atmosphere to obtain the roasted product.

[0042] (4) Selective leaching and lithium salt recovery: The roasted product obtained in step (3) is added to deionized water, and carbon dioxide gas is introduced under stirring conditions to carry out carbonated water leaching, so that the leached lithium compounds in the roasted product are converted and enter the liquid phase; wherein, the solid-liquid ratio is 20 g / L, the carbon dioxide gas flow rate is 100 mL / min, the leaching temperature is 50 ℃, and the leaching time is 2 h. After leaching, the leaching slurry is filtered and separated to obtain lithium-containing leachate and leaching residue rich in Ni, Co, and Mn. The obtained lithium-containing leachate is concentrated by evaporation, cooled and crystallized, separated by solid and liquid and dried to obtain lithium carbonate product.

[0043] The lithium leaching rate in this embodiment was 98.1% as tested. The calcination product mainly consisted of elemental nickel, elemental cobalt, manganese oxide, and lithium carbonate. After leaching with carbonated water, the leaching residue mainly retained elemental nickel, elemental cobalt, and manganese oxide, while the characteristic peak of lithium carbonate essentially disappeared. This indicates that lithium in the calcination product had effectively entered the liquid phase, while transition metals such as Ni, Co, and Mn were mainly retained in the solid residue. These results demonstrate that, under the conditions of a yeast residue to waste plastic mass ratio of 6:4, a waste ternary cathode material powder to composite reducing agent mass ratio of 1:0.3, a calcination temperature of 600 ℃, and a calcination time of 40 min, this invention can achieve highly efficient and selective recovery of lithium from waste ternary cathode materials.

[0044] Example 2

[0045] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials through the co-reduction calcination of yeast residue and waste plastics at a relatively low calcination temperature. The specific steps are as follows:

[0046] In this embodiment, the preparation methods of waste ternary cathode material powder, the preparation methods of yeast residue-waste plastic composite reducing agent, the composition of the composite reducing agent, and the subsequent carbonated water leaching and lithium salt recovery conditions are all the same as in Example 1. The difference is that during the synergistic reduction roasting process, the roasting temperature is reduced from 600 ℃ in Example 1 to 500 ℃, the heating rate remains 10 ℃ / min, and the holding time remains 40 min.

[0047] Specifically, waste ternary cathode material powder and yeast residue-waste plastic composite reducing agent are mixed at a mass ratio of 1:0.3, wherein the mass ratio of yeast residue to waste polyethylene is 6:4. The resulting mixture to be roasted is placed in a tube furnace, heated to 500 °C under an inert atmosphere and held for 40 min. After roasting, it is cooled to room temperature under an inert atmosphere to obtain the roasted product.

[0048] Subsequently, the obtained calcined product was added to deionized water, and carbon dioxide gas was introduced under stirring conditions for carbonated water leaching. The solid-liquid ratio was 20 g / L, the carbon dioxide gas flow rate was 100 mL / min, the leaching temperature was 50 ℃, and the leaching time was 2 h. After leaching, solid-liquid separation was performed to obtain a lithium-containing leachate and a leaching residue rich in Ni, Co, and Mn. The lithium-containing leachate was then subjected to evaporation concentration, cooling crystallization, solid-liquid separation, and drying to obtain the lithium carbonate product.

[0049] This embodiment illustrates that, even at lower roasting temperatures, the co-pyrolysis of yeast residue and waste plastics can still form a gas-solid synergistic reduction system involving hydrogen-rich volatiles, nitrogen-containing volatiles, light hydrocarbons, reducing gases, and solid carbon. This system promotes structural destruction and lattice lithium release from waste ternary cathode materials, converting lithium into leached lithium compounds. Testing showed that the lithium leaching rate in this embodiment was 87.4%. Compared to Example 1, the lithium leaching rate decreased after lowering the roasting temperature, but effective selective recovery of lithium from waste ternary cathode materials is still possible, demonstrating the feasibility of this invention for lithium extraction through reduction roasting at lower temperatures. Figure 5 It can be seen that the lithium leaching rate first increases and then decreases with increasing calcination temperature, indicating that a suitable temperature is conducive to enhancing the synergistic reduction of yeast residue and waste plastic and promoting lithium conversion, while excessively high temperature is not conducive to subsequent leaching.

[0050] Example 3

[0051] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials through the synergistic reduction and roasting of yeast residue and waste plastics under conditions of low composite reducing agent dosage. The specific steps are as follows:

[0052] In this embodiment, the preparation methods of waste ternary cathode material powder, the preparation method of yeast residue-waste plastic composite reducing agent, the mass ratio of yeast residue to waste plastic, the synergistic reduction roasting temperature, the roasting time, and the subsequent carbonated water leaching and lithium salt recovery conditions are all the same as in Example 1. The difference is that the mass ratio of waste ternary cathode material powder to yeast residue-waste plastic composite reducing agent is reduced from 1:0.3 in Example 1 to 1:0.1.

[0053] Specifically, waste ternary cathode material powder and yeast residue-waste plastic composite reducing agent were mixed at a mass ratio of 1:0.1, wherein the mass ratio of yeast residue to waste polyethylene in the composite reducing agent was 6:4. The resulting mixture to be roasted was placed in a tube furnace and subjected to synergistic reduction roasting under an inert atmosphere. The heating rate was 10 °C / min, the roasting temperature was 600 °C, and the holding time was 40 min. After roasting, the mixture was cooled to room temperature under an inert atmosphere to obtain the roasted product.

[0054] Subsequently, the obtained calcined product was added to deionized water, and carbon dioxide gas was introduced under stirring conditions for carbonated water leaching. The solid-liquid ratio was 20 g / L, the carbon dioxide gas flow rate was 100 mL / min, the leaching temperature was 50 ℃, and the leaching time was 2 h. After leaching, solid-liquid separation was performed to obtain a lithium-containing leachate and a leaching residue rich in Ni, Co, and Mn. The lithium-containing leachate was then subjected to evaporation concentration, cooling crystallization, solid-liquid separation, and drying to obtain the lithium carbonate product.

[0055] This embodiment illustrates that, even with a reduced amount of composite reducing agent, yeast residue and waste plastics can still co-pyrolyze to produce reducing components such as hydrogen-rich volatiles, nitrogen-containing volatiles, light hydrocarbons, reducing gases, and solid carbon. This promotes the structural destruction of waste ternary cathode materials and the release of lattice lithium, converting lithium into leached lithium compounds. Testing showed that the lithium leaching rate in this embodiment was 85.6%. Compared to Example 1, the lithium leaching rate decreased after reducing the amount of composite reducing agent, but effective selective recovery of lithium from waste ternary cathode materials can still be achieved, indicating that the present invention still has good applicability under conditions of lower reducing agent dosage. Figure 4 It can be seen that the lithium leaching rate first increases and then decreases with the increase of the amount of composite reducing agent added, indicating that an appropriate amount of reducing agent is beneficial to enhancing the reduction effect, while excessive addition is not conducive to subsequent lithium leaching.

[0056] Example 4

[0057] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials by synergistic reduction of yeast residue-waste plastic composite reducing agent under different ratios of yeast residue to waste plastic.

[0058] In this embodiment, the preparation method of waste ternary cathode material powder, the pretreatment method of yeast residue and waste plastic, the mass ratio of waste ternary cathode material powder to composite reducing agent, the synergistic reduction roasting conditions, and the subsequent carbonated water leaching and lithium salt recovery conditions are all the same as in Example 1. The difference is that the mass ratio of yeast residue to waste polyethylene in the yeast residue-waste plastic composite reducing agent is adjusted from 6:4 in Example 1 to 2:8.

[0059] Specifically, waste ternary cathode material powder and yeast residue-waste plastic composite reducing agent were mixed at a mass ratio of 1:0.3, wherein the mass ratio of yeast residue to waste polyethylene in the composite reducing agent was 2:8. The resulting mixture to be roasted was placed in a tube furnace and heated to 600 °C at a heating rate of 10 °C / min under an inert atmosphere, held for 40 min, and then cooled to obtain the roasted product. Subsequently, the roasted product was leached with carbonated water under the conditions of a solid-liquid ratio of 20 g / L, a carbon dioxide gas flow rate of 100 mL / min, a leaching temperature of 50 °C, and a leaching time of 2 h. After solid-liquid separation, evaporation concentration, cooling crystallization, and drying, lithium carbonate product was obtained.

[0060] Testing showed that the lithium leaching rate in this embodiment was 94.1%. Compared to Example 1, when the proportion of yeast residue decreased and the proportion of waste plastic increased, the contributions of hydrogen-rich volatiles and light hydrocarbons in the system increased, but the contributions of nitrogen-containing volatiles and solid biochar decreased relatively. This led to a change in the matching degree between gas-phase reduction and solid-phase reduction, resulting in a change in the lithium leaching rate compared to Example 1. This result indicates that there is a suitable synergistic ratio between yeast residue and waste plastic. Figure 3 It can be seen that the lithium leaching rate first increases and then decreases with the increase of the proportion of yeast residue in the composite reducing agent, indicating that there is a suitable ratio between yeast residue and waste plastic, which can promote the conversion of lithium through gas-solid synergistic reduction.

[0061] Example 5

[0062] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials by synergistic reduction of yeast residue-waste plastic composite reducing agent under conditions of high yeast residue ratio.

[0063] In this embodiment, the preparation method of waste ternary cathode material powder, the pretreatment method of yeast residue and waste plastic, the mass ratio of waste ternary cathode material powder to composite reducing agent, the synergistic reduction roasting conditions, and the subsequent carbonated water leaching and lithium salt recovery conditions are all the same as in Example 1. The difference is that the mass ratio of yeast residue to waste polyethylene in the yeast residue-waste plastic composite reducing agent is adjusted from 6:4 in Example 1 to 8:2.

[0064] Specifically, waste ternary cathode material powder and yeast residue-waste plastic composite reducing agent were mixed at a mass ratio of 1:0.3, wherein the mass ratio of yeast residue to waste polyethylene in the composite reducing agent was 8:2. The resulting mixture to be roasted was placed in a tube furnace and heated to 600 °C at a heating rate of 10 °C / min under an inert atmosphere, held at that temperature for 40 min, and then cooled to obtain the roasted product. Subsequently, it was processed under the same carbonated water leaching and lithium salt recovery conditions as in Example 1 to obtain lithium carbonate product.

[0065] The lithium leaching rate in this embodiment was 95.4% as tested. Compared with Example 1, when the proportion of yeast residue was further increased, the nitrogen-containing volatiles and solid biochar produced by the pyrolysis of yeast residue increased, but the hydrogen-rich volatiles and light hydrocarbons released by the pyrolysis of waste plastics decreased relatively. At the same time, the influence of yeast residue ash and oxygen-containing pyrolysis products may have increased, resulting in a decrease in the lithium leaching rate compared with Example 1. This result further illustrates that a suitable mass ratio of yeast residue to waste plastic is beneficial to improving the synergistic reduction roasting effect.

[0066] Example 6

[0067] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials by synergistic reduction of yeast residue and waste plastics under different roasting time conditions.

[0068] In this embodiment, the preparation methods of waste ternary cathode material powder, the preparation method of yeast residue-waste plastic composite reducing agent, the mass ratio of yeast residue to waste plastic, the mass ratio of waste ternary cathode material powder to composite reducing agent, the calcination temperature, and the subsequent carbonated water leaching and lithium salt recovery conditions are all the same as in Example 1. The difference is that the holding time for synergistic reduction calcination is adjusted from 40 min in Example 1 to 20 min.

[0069] Specifically, waste ternary cathode material powder and yeast residue-waste plastic composite reducing agent were mixed at a mass ratio of 1:0.3, wherein the mass ratio of yeast residue to waste polyethylene was 6:4. The resulting mixture was placed in a tube furnace and heated to 600 °C at a heating rate of 10 °C / min under an inert atmosphere, held for 20 min, and then cooled to obtain the calcined product. Subsequently, the calcined product was leached with carbonated water under the conditions of a solid-liquid ratio of 20 g / L, a carbon dioxide gas flow rate of 100 mL / min, a leaching temperature of 50 °C, and a leaching time of 2 h. After solid-liquid separation, evaporation concentration, cooling crystallization, and drying, lithium carbonate product was obtained.

[0070] Testing showed that the lithium leaching rate in this embodiment was 95.0%. Compared with Example 1, when the roasting time was shortened from 40 min to 20 min, the lithium leaching rate only decreased slightly, indicating that the hydrogen-rich volatiles, nitrogen-containing volatiles, reducing gases, and solid carbon formed by the co-pyrolysis of yeast residue and waste plastics can exert a synergistic reduction effect in a short time, promoting the structural destruction of waste ternary cathode materials and the release of lattice lithium. This result shows that the synergistic reduction roasting process of the present invention has a fast reaction rate, and appropriately shortening the roasting time can still achieve a high level of lithium selective recovery, which is beneficial for reducing roasting energy consumption and improving process efficiency. Figure 6 It can be seen that the lithium leaching rate first increases and then slightly decreases with the extension of roasting time, indicating that appropriately extending the roasting time is beneficial to the conversion of lithium, while further extending the time has limited effect on improving the leaching effect.

[0071] Comparative Example 1

[0072] This comparative example provides a method for roasting and leaching waste ternary cathode materials without adding a reducing agent. The specific steps are as follows:

[0073] The preparation method of the waste ternary cathode material powder, the subsequent carbonated water leaching conditions, and the lithium salt recovery conditions in this comparative example are the same as in Example 1. The difference is that in this comparative example, no yeast residue-waste plastic composite reducing agent is added during the synergistic reduction roasting process, and only the waste ternary cathode material powder obtained in step (1) is roasted separately.

[0074] Specifically, the pretreated waste ternary cathode material powder was placed in a tube furnace and calcined under an inert atmosphere at a heating rate of 10 °C / min, a calcination temperature of 600 °C, and a holding time of 40 min. After calcination, the powder was cooled to room temperature under an inert atmosphere to obtain the calcined product.

[0075] Subsequently, the obtained roasted product was added to deionized water, and carbon dioxide gas was introduced under stirring conditions for carbonated water leaching. The solid-liquid ratio was 20 g / L, the carbon dioxide gas flow rate was 100 mL / min, the leaching temperature was 50 ℃, and the leaching time was 2 h. After leaching, the leachate and leaching residue were obtained by solid-liquid separation, and the lithium content in the leachate was detected.

[0076] The lithium leaching rate in this comparative example was 4.8%. Compared with Example 1, without the addition of a reducing agent, the layered structure of the waste ternary cathode material was difficult to be fully destroyed, and the conversion of lattice lithium to leached lithium compounds was lower, resulting in a significant decrease in the lithium leaching rate during carbonated water leaching. This result indicates that the yeast residue-waste plastic composite reducing agent plays an important role in promoting the structural transformation and selective release of lithium in waste ternary cathode materials.

[0077] Comparative Example 2

[0078] This comparative example provides a method for roasting and leaching waste ternary cathode materials using yeast residue as a reducing agent alone. The specific steps are as follows:

[0079] In this comparative example, the preparation method of waste ternary cathode material powder, the yeast residue pretreatment method, the subsequent carbonated water leaching conditions, and the lithium salt recovery conditions are all the same as in Example 1. The difference is that the reducing agent used in this comparative example is only yeast residue powder, without the addition of waste plastics, that is, the mass ratio of yeast residue to waste plastics is 10:0.

[0080] Specifically, the waste ternary cathode material powder obtained in step (1) is mixed with yeast residue powder at a mass ratio of 1:0.3 to obtain a mixture to be calcined. The mixture to be calcined is placed in a tube furnace and calcined under an inert atmosphere at a heating rate of 10 ℃ / min, a calcination temperature of 600 ℃, and a holding time of 40 min. After calcination, it is cooled to room temperature under an inert atmosphere to obtain the calcined product.

[0081] Subsequently, the obtained calcined product was added to deionized water, and carbon dioxide gas was introduced under stirring conditions for carbonated water leaching. The solid-liquid ratio was 20 g / L, the carbon dioxide gas flow rate was 100 mL / min, the leaching temperature was 50 ℃, and the leaching time was 2 h. After leaching, lithium-containing leachate and leaching residue were obtained by solid-liquid separation, and the lithium content in the lithium-containing leachate was detected.

[0082] The lithium leaching rate in this comparative example was 90.6%. Compared with Example 1, when yeast residue was used alone as a reducing agent, although the pyrolysis of yeast residue could produce a certain amount of reducing gas, nitrogen-containing volatiles, and solid biochar, which had a certain promoting effect on the structural destruction and lithium release of waste ternary cathode materials, the lack of hydrogen-rich volatiles, light hydrocarbons, and free radical components released by the pyrolysis of waste plastics resulted in relatively insufficient gas-phase reduction capacity and gas-solid synergistic reduction effect in the roasting system, leading to a lower lithium leaching rate than the yeast residue-waste plastic composite reducing agent system. This result indicates that introducing waste plastics as a hydrogen-rich co-reducing component is beneficial to enhancing the synergistic effect of the yeast residue reduction roasting process and improving the selective recovery efficiency of lithium.

[0083] Comparative Example 3

[0084] This comparative example provides a method for roasting and leaching waste ternary cathode materials using waste plastics as a reducing agent alone. The specific steps are as follows:

[0085] In this comparative example, the preparation method of waste ternary cathode material powder, the pretreatment method of waste plastics, the subsequent carbonated water leaching conditions, and the lithium salt recovery conditions are all the same as in Example 1. The difference is that the reducing agent used in this comparative example is only waste polyethylene particles, and no yeast residue is added; that is, the mass ratio of yeast residue to waste plastics is 0:10.

[0086] Specifically, the waste ternary cathode material powder obtained in step (1) is mixed with waste polyethylene particles at a mass ratio of 1:0.3 to obtain a mixture to be calcined. The mixture to be calcined is placed in a tube furnace and calcined under an inert atmosphere at a heating rate of 10 ℃ / min, a calcination temperature of 600 ℃, and a holding time of 40 min. After calcination, it is cooled to room temperature under an inert atmosphere to obtain the calcined product.

[0087] Subsequently, the obtained calcined product was added to deionized water, and carbon dioxide gas was introduced under stirring conditions for carbonated water leaching. The solid-liquid ratio was 20 g / L, the carbon dioxide gas flow rate was 100 mL / min, the leaching temperature was 50 ℃, and the leaching time was 2 h. After leaching, lithium-containing leachate and leaching residue were obtained by solid-liquid separation, and the lithium content in the lithium-containing leachate was detected.

[0088] The lithium leaching rate in this comparative example was 84.5%. Compared with Example 1, when waste plastic was used alone as a reducing agent, the pyrolysis of waste polyethylene could produce hydrogen-rich volatiles, light hydrocarbons, and free radical components, which had a certain promoting effect on the reduction and conversion of waste ternary cathode materials. However, due to the lack of nitrogen-containing volatiles, reducing gases, and solid biochar produced by yeast residue pyrolysis, the synergistic effect of gas-phase reduction and solid-phase reduction in the roasting system was insufficient, making it difficult to fully promote the destruction of the layered structure and the release of lattice lithium in the waste ternary cathode material, resulting in a lower lithium leaching rate than the yeast residue-waste plastic composite reducing agent system. This result indicates that yeast residue plays an important role in the composite reducing agent system, and the combined use of yeast residue and waste plastic is beneficial to forming a more effective gas-solid synergistic reduction system.

[0089] Comparative Example 4

[0090] This comparative example provides a method for roasting and leaching waste ternary cathode materials using graphite as a reducing agent. The specific steps are as follows:

[0091] In this comparative example, the preparation method of the waste ternary cathode material powder, the subsequent carbonated water leaching conditions, and the lithium salt recovery conditions are all the same as in Example 1. The difference is that in this comparative example, the yeast residue-waste plastic composite reducing agent in Example 1 is replaced with a graphite reducing agent to verify the effect of ordinary solid carbonaceous reducing agents on the selective lithium extraction effect of waste ternary cathode materials.

[0092] Specifically, the waste ternary cathode material powder obtained in step (1) is mixed with graphite powder at a mass ratio of 1:0.3 to obtain a mixture to be calcined. The mixture to be calcined is placed in a tube furnace and calcined under an inert atmosphere at a heating rate of 10 ℃ / min, a calcination temperature of 600 ℃, and a holding time of 40 min. After calcination, it is cooled to room temperature under an inert atmosphere to obtain the calcined product.

[0093] Subsequently, the obtained calcined product was added to deionized water, and carbon dioxide gas was introduced under stirring conditions for carbonated water leaching. The solid-liquid ratio was 20 g / L, the carbon dioxide gas flow rate was 100 mL / min, the leaching temperature was 50 ℃, and the leaching time was 2 h. After leaching, lithium-containing leachate and leaching residue were obtained by solid-liquid separation, and the lithium content in the lithium-containing leachate was detected.

[0094] The lithium leaching rate in this comparative example was 88.2%. Compared with Example 1, when graphite was used as a reducing agent, it mainly participated in the reaction through solid-phase carbothermic reduction. At lower calcination temperatures and shorter holding times, the contact and reaction between graphite and the waste ternary cathode material particles were limited, making it difficult to form the gaseous reducing components such as hydrogen-rich volatiles, light hydrocarbons, nitrogen-containing volatiles, and reducing gases generated during the co-pyrolysis of the yeast residue-waste plastic composite reducing agent. Therefore, the graphite reduction system had a weaker promoting effect on the destruction of the layered structure and the release of lattice lithium in the waste ternary cathode material than the composite reducing agent system described in this invention, resulting in a lower lithium leaching rate than in Example 1. This result indicates that the highly efficient and selective lithium extraction effect of this invention cannot be achieved simply by replacing ordinary carbonaceous reducing agents, but mainly stems from the gas-solid synergistic reduction effect formed by the synergistic pyrolysis of yeast residue and waste plastic.

[0095] Comparative Example 5

[0096] This comparative example provides a method for roasting and leaching waste ternary cathode materials using common biomass as a reducing agent. The specific steps are as follows:

[0097] In this comparative example, the preparation method of the waste ternary cathode material powder, the subsequent carbonated water leaching conditions, and the lithium salt recovery conditions are all the same as in Example 1. The difference is that in this comparative example, the yeast residue-waste plastic composite reducing agent in Example 1 is replaced with a common biomass reducing agent, which is soybean residue or corn distillers' grains.

[0098] Specifically, soybean residue or corn distillers' grains are washed three times with deionized water to remove soluble impurities from the surface, then dried at 80 °C for 12 h, and then pulverized and sieved to obtain ordinary biomass powder with a particle size of 50-100 mesh. The waste ternary cathode material powder obtained in step (1) is mixed with the ordinary biomass powder at a mass ratio of 1:0.3 to obtain the mixture to be roasted.

[0099] The mixture to be calcined was placed in a tube furnace and calcined under an inert atmosphere at a heating rate of 10°C / min, a calcination temperature of 600°C, and a holding time of 40 min. After calcination, it was cooled to room temperature under an inert atmosphere to obtain the calcined product.

[0100] Subsequently, the obtained calcined product was added to deionized water, and carbon dioxide gas was introduced under stirring conditions for carbonated water leaching. The solid-liquid ratio was 20 g / L, the carbon dioxide gas flow rate was 100 mL / min, the leaching temperature was 50 ℃, and the leaching time was 2 h. After leaching, lithium-containing leachate and leaching residue were obtained by solid-liquid separation, and the lithium content in the lithium-containing leachate was detected.

[0101] The lithium leaching rate in this comparative example was 86.1%. Compared with Example 1, when using common biomass such as soybean residue or corn distillers' grains as a single reducing agent, although a certain amount of reducing gas and solid biochar can be generated during the pyrolysis process, which has a certain promoting effect on the structural destruction and lithium release of waste ternary cathode materials, the gas-phase reduction capacity and gas-solid synergistic reduction effect in the system are relatively insufficient due to the lack of hydrogen-rich volatiles, light hydrocarbons and free radical components released by the pyrolysis of waste plastics. At the same time, the composition of common biomass is complex, and ash and oxygen-containing pyrolysis products may affect the phase transformation of the roasted products and the subsequent lithium leaching effect, resulting in a lower lithium leaching rate than in Example 1. This result shows that the yeast residue-waste plastic composite reducing agent system of the present invention has a better synergistic reduction effect and lithium selective recovery efficiency than a single common biomass reducing agent.

Claims

1. A method for recovering lithium from waste ternary cathode materials by co-reduction of yeast residue and waste plastics, characterized in that: The method includes the following steps: (1) Preparation of waste ternary cathode material powder: Waste ternary lithium-ion batteries are subjected to safe discharge, dismantling, separation, peeling, drying, heat treatment, grinding and sieving to obtain waste ternary cathode material powder; (2) Preparation of yeast residue-waste plastic composite reducing agent: yeast residue is washed, dried, crushed and sieved to obtain yeast residue powder; waste plastic is washed, dried, sheared, crushed or crushed to obtain waste plastic particles; the yeast residue powder and waste plastic particles are mixed to obtain yeast residue-waste plastic composite reducing agent; (3) Synergistic reduction roasting: The waste ternary cathode material powder obtained in step (1) is mixed with the yeast residue-waste plastic composite reducing agent obtained in step (2) to obtain a mixture to be roasted; then the mixture to be roasted is synergistically reduced roasted in an inert atmosphere, vacuum or closed atmosphere, so that the lithium element in the waste ternary cathode material is converted into leached lithium compounds, while transition metals such as Ni, Co, and Mn are mainly converted into insoluble low-valence oxides or metal phases, and the roasted product is obtained after cooling; (4) Selective leaching and lithium salt recovery: The roasted product obtained in step (3) is added to water and carbon dioxide gas is introduced for carbonated water leaching, so that lithium elements preferentially enter the liquid phase; after leaching, solid-liquid separation is performed to obtain lithium-containing leachate and leaching residue rich in Ni, Co and Mn; the obtained lithium-containing leachate is concentrated by evaporation, crystallization, solid-liquid separation and drying to obtain lithium carbonate product.

2. The method according to claim 1, characterized in that: The specific steps (1) are as follows: waste ternary lithium-ion batteries are placed in a 5-15 wt% sodium sulfate solution for safe discharge for 6-48 h. After disassembly and separation, waste ternary positive electrode sheets are obtained and washed with deionized water to remove residual electrolyte and soluble impurities from the surface. The obtained positive electrode sheets are cut into 0.5-5 cm sheet materials and placed in deionized water for ultrasonic-assisted peeling. The solid-liquid ratio is 10-100 g / L, the ultrasonic power is 100-800W, the treatment temperature is 20-80 ℃, and the treatment time is 10-120 min. The peeled mixture is sieved, filtered, or centrifuged to remove aluminum foil fragments. The obtained solid is washed and dried and then heat-treated in air at 400-600 ℃ for 1-5 h to remove residual binder and conductive carbon. Finally, it is ground and sieved to obtain waste ternary positive electrode material powder.

3. The method according to claim 1, characterized in that: In step (2), the particle size of the yeast residue powder is 50~100 mesh; the particle size of the waste plastic particles is 0.01~0.55 mm.

4. The method according to claim 1, characterized in that: In step (2), the waste plastic is waste polyethylene and / or waste polypropylene.

5. The method according to claim 1, characterized in that: In step (2), the mass ratio of the yeast residue powder to the waste plastic particles is 0:10 to 10:

0.

6. The method according to claim 1, characterized in that: In step (3), the mass ratio of the waste ternary cathode material powder to the yeast residue-waste plastic composite reducing agent is 1:0.1~0.

3.

7. The method according to claim 1, characterized in that: In step (3), the calcination temperature of the synergistic reduction calcination is 450~650 ℃, the heating rate is 10~20 ℃ / min, and the holding time is 20~60 min.

8. The method according to claim 1, characterized in that, In step (4), the solid-liquid ratio of the carbonated water leaching is 10~50 g / L, the carbon dioxide gas flow rate is 50~200 mL / min, the leaching temperature is 20~80 ℃, and the leaching time is 0.5~3 h.

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