Method for selectively extracting lithium and regenerating waste ternary positive electrode material

Abstract

The invention belongs to the technical field of battery waste recovery, and particularly discloses a method for selective lithium extraction and regeneration of a waste ternary positive electrode material. The method comprises the following steps: putting waste ternary positive electrode material powder into a reactor, and carrying out high-energy field in-situ lattice reconstruction treatment to obtain treated powder; adding the powder into a solvent, carrying out leaching reaction, and carrying out solid-liquid separation to obtain a lithium-rich solution and leaching residues; and performing lithium precipitation treatment on the lithium-rich solution to obtain lithium carbonate precipitate, mixing the lithium carbonate precipitate with the leaching residues, and calcining to obtain the regenerated ternary positive electrode material. According to the method, in-situ lattice reconstruction of the waste ternary positive electrode material is realized from the aspects of energy action mechanism and crystal structure design, separation of lithium and other metals is realized, the high-quality ternary positive electrode material is obtained through further regeneration, waste resource utilization is realized, and the whole process is green, environment-friendly and low in cost.

Description

Technical Field

[0001] This invention relates to the field of battery waste recycling technology, and in particular to a method for selective lithium extraction and regeneration of waste ternary cathode materials. Background Technology

[0002] Currently, the recovery of valuable metals from spent lithium-ion batteries mostly involves a wet recycling process using reducing acid leaching to dissolve metal ions, followed by precipitation, extraction, crystallization, and resynthesis. While the wet recycling route is mature and adaptable, it suffers from drawbacks such as a long process, low metal recovery rate, and high auxiliary material costs. Besides dissolution methods, pyrometallurgy is also used in the industry. In pyrometallurgy, spent battery materials are fed into a high-temperature pyrolysis furnace, and the reaction is controlled within different temperature ranges. The spent lithium-ion battery cathode materials undergo a series of physicochemical changes, and valuable metal elements are separated based on the differences in the properties of the resulting products. Pyrometallurgical recycling is the simplest process for treating spent batteries, with large battery throughput and a high degree of automation. However, it faces challenges such as difficulty in controlling the pyrolysis furnace temperature, high safety risks, high impurity content and alloy content in the produced black powder, and difficulties in post-processing.

[0003] Therefore, it is necessary to explore more new methods for recycling waste lithium battery cathode materials to achieve efficient and selective recycling of valuable metals. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention provides a method for selectively extracting lithium from waste ternary cathode materials using a high-energy process and regenerating the ternary cathode materials. This invention achieves in-situ lattice reconstruction of waste ternary cathode materials from the perspectives of "energy action mechanism" and "crystal structure design," and then combines this with a water leaching reaction to achieve the separation of lithium from other metals. The obtained high-purity lithium carbonate is then calcined with specifically treated leaching residue to obtain high-quality regenerated ternary cathode materials.

[0005] This invention provides a method for selective lithium extraction and regeneration of waste ternary cathode materials, comprising the following steps:

[0006] S1. Place the waste ternary cathode material powder in a reactor for high-energy field in-situ lattice reconstruction treatment to obtain the treated powder.

[0007] S2. Add the treated powder to the solvent, leaching reaction, solid-liquid separation to obtain lithium-rich solution and leaching residue;

[0008] S3. Add sodium carbonate to the lithium-rich solution, heat to react, and separate the solid and liquid to obtain lithium carbonate precipitate. Mix the lithium carbonate precipitate with the leaching residue and calcine to obtain the regenerated ternary cathode material.

[0009] The high-energy field in-situ lattice reconstruction process includes: microwave selective excitation reconstruction, low-temperature plasma selective etching and reconstruction, or pulsed laser-induced surface reconstruction.

[0010] According to some embodiments of the present invention, the waste ternary cathode material powder is waste cathode powder obtained by discharging, disassembling cathode sheets, and stripping current collectors from waste ternary lithium batteries.

[0011] According to some embodiments of the present invention, the reactor used for microwave selective excitation and reconstruction is a pulsed microwave sintering system; specifically, an atmosphere-protected box-type pulsed microwave sintering system.

[0012] According to some embodiments of the present invention, the processing parameters of the pulsed microwave sintering system are as follows: microwave power is 3~5kW, pulse mode is intermittent pulse, microwave is turned on for 5~15s, turned off for 2~5s, temperature rises to 950~1050℃ in 2~3min, and the highest temperature is maintained for 4~6min, during which oxygen is introduced at a rate of 200~500mL / min.

[0013] According to some preferred embodiments of the present invention, the maximum temperature is 1000±10℃.

[0014] According to some embodiments of the present invention, the oxygen is high-purity oxygen (purity ≥ 99.5%), and the flow rate of the oxygen is 250~350 mL / min.

[0015] This invention utilizes optimal pulsed microwave processing parameters. The appropriate microwave power ensures that the target processing temperature is reached in a short time, while avoiding local overheating caused by excessive power. The pulse mode employs intermittent pulses with appropriate parameters to effectively prevent material temperature runaway and promotes lattice destruction by utilizing the "thermal shock effect".

[0016] The specific mechanism of pulsed microwave treatment of waste cathode materials in this invention is as follows: Mn 4+ (d) 3 The electronic configuration and the surrounding lattice oxygen have specific dielectric loss factors under a particular microwave field, and will be preferentially and rapidly heated, leading to violent local lattice vibrations or even "melting"; the rapid bulk heating characteristics of microwaves cause the Mn-O octahedrons to twist and change their connection mode, forming a structure favorable for Li + The structure is a metastable, diffused structure, while the Ni / Co-O region retains its structure due to less energy absorption.

[0017] According to some embodiments of the present invention, the reactor used for the low-temperature plasma selective etching and reconstruction is a low-temperature plasma processing system.

[0018] According to some preferred embodiments of the present invention, the cryogenic plasma treatment system is a capacitively coupled parallel plate cryogenic plasma treatment system.

[0019] According to some embodiments of the present invention, the processing parameters of the low-temperature plasma processing system are as follows: a 12~16MHz radio frequency power supply with a power density of 0.5~1.5W / cm². 2 The reaction chamber pressure is 10~100Pa, the processing time is 5~30min, the sample temperature is 25~75℃, and oxygen is introduced at 50~200sccm during the process.

[0020] According to some preferred embodiments of the present invention, the sample temperature is 40~60°C, and using this suitable processing temperature helps to promote the desorption of reaction byproducts.

[0021] According to some preferred embodiments of the present invention, the processing time is 10 to 20 minutes to avoid insufficient processing due to too short a processing time, and excessive processing time may lead to over-etching or low efficiency.

[0022] This invention utilizes low-temperature plasma to treat ternary cathode materials at relatively low temperatures below 300°C in an oxygen atmosphere. The high-energy active particles in the plasma (such as O2)... + O2 + It will preferentially interact with higher-energy sites in the crystal lattice (such as Li-O-Mn) to "knock out" Li. + This leads to the breaking and recombination of Mn-O bonds. Plasma bombardment creates a large number of defects on the particle surface and at grain boundaries. These defects are reconstructed around Mn ions, forming a fast path for lithium ion diffusion. At the same time, the oxygen atmosphere ensures that Ni / Co is not reduced.

[0023] According to some embodiments of the present invention, the reactor used for the pulsed laser-induced surface reconstruction is a pulsed laser processing system.

[0024] According to some preferred embodiments of the present invention, the pulsed laser processing system is an airflow pulsed laser processing system, which allows the ternary cathode powder to pass through the nanosecond laser beam scanning area under the transport of airflow.

[0025] According to some embodiments of the present invention, the processing parameters of the pulsed laser processing system are as follows: using a laser with a wavelength of 1064 nm or 532 nm, a pulse energy of 50~400 mJ / pulse, a pulse frequency of 10~40 kHz, a spot diameter of 50~200 μm at the focal point of the waste ternary cathode material powder flow, a galvanometer scanning speed of 100~200 mm / s, a carrier gas of compressed air or oxygen with a flow rate of 10~50 m / s, a powder feeding rate of 5~50 g / min, and a powder flow concentration of 10~100 g / m³. 3 During this period, a slight negative pressure of -10 to -50 Pa is applied to the cavity.

[0026] According to some preferred embodiments of the present invention, the pulse energy is 50~200mJ / pulse and the pulse frequency is 20~50kHz; the frequency determines the number of pulses irradiating the powder per unit time. The optimal pulse energy and frequency process parameters explored in this invention can avoid insufficient modification effect due to too low energy and excessive vaporization of powder due to too high energy.

[0027] According to some preferred embodiments of the present invention, the carrier gas is compressed air; the appropriate airflow velocity of the present invention can ensure that the powder is fully dispersed and accelerated to form a stable powder flow.

[0028] According to some preferred embodiments of the present invention, the powder feeding rate is 10~20g / min, and the powder feeding rate is matched with the laser parameters to ensure that each powder particle has a high probability of being effectively irradiated. At the same time, by controlling an appropriate powder flow concentration, the inter-particle shielding effect is avoided, and the uniformity of laser processing is guaranteed.

[0029] This invention employs short-pulse, high-energy-density lasers to process waste ternary cathode materials. The high energy density of nanosecond lasers enables the surface layer of ternary particles (micrometer level) to absorb energy and reach the phase transition temperature in an extremely short time (nanosecond level), inducing amorphization or phase transition in the surface layer. The laser parameters of this invention are precisely controlled to ensure that only the Mn-rich local area undergoes structural changes, forming an "activation layer" with high lithium-ion conductivity, while the internal lattice and Ni / Co valence state remain unchanged.

[0030] According to some embodiments of the present invention, in step S2, the liquid-solid mass ratio of the leaching reaction is (5~50):1; the solvent is water or a dilute weak acid solution; preferably, the solvent is water; more preferably, the water is hot water at 40~70°C.

[0031] According to some embodiments of the present invention, in step S3, the mass ratio of the lithium carbonate precipitate to the leaching residue is 0.3~0.5:1.

[0032] According to some embodiments of the present invention, the calcination conditions are as follows: treatment at 800~1000℃ for 5~7 hours in an air atmosphere.

[0033] The beneficial effects of this invention are:

[0034] The method of this invention exhibits extreme selectivity, achieving the separation of lithium from other metals at the levels of "energy action mechanism" and "crystal structure design." The lithium leaching rate is >98%, while the co-leaching rate of Ni, Co, and Mn is <2%, far exceeding any existing technology. This invention also boasts advantages of extremely simple process and low cost. The core steps require only one high-energy treatment and water leaching treatment, eliminating the need for strong acids and complex separation processes, significantly reducing reagent and energy costs. Furthermore, it generates almost no wastewater or waste acid discharge, achieving green recycling. In addition, the product obtained by this invention has high value, with high purity lithium-rich solutions and simple subsequent processing. The obtained nickel-cobalt-manganese-rich solid is an ideal precursor for regenerated cathode materials, making it extremely valuable. The technical barriers of this invention are high, as the method relies on a deep understanding of the interaction between high-energy fields and materials, has a narrow process parameter window, and exhibits significant innovation and technical barriers.

[0035] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Detailed Implementation

[0036] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0037] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0038] Example 1

[0039] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials using pulsed microwave selective excitation and reconstruction. The specific steps are as follows:

[0040] 1) Place the waste ternary lithium battery in 2 mol / L salt water for 30 hours of discharge treatment, dry the discharged battery at 85℃, disassemble and separate the positive electrode sheet, soak the positive electrode sheet in N-methylpyrrolidone, separate the current collector in the electrode sheet, filter, wash and dry to obtain waste positive electrode powder.

[0041] 2) Pulse microwave treatment: Oxygen is introduced into a pulse microwave device, and the waste ternary powder is treated using pulse microwaves; the specific equipment and operation methods are as follows:

[0042] This embodiment employs an atmosphere-protected box-type pulsed microwave sintering system for pulsed microwave processing. The system includes: ① A microwave generator: a 2.45 GHz magnetron with continuously adjustable microwave power from 0 to 6 kW; ② A reaction chamber: made of stainless steel, lined with microwave-transmitting materials (such as high-purity quartz or corundum), and equipped with a high-temperature resistant sealing flange to ensure airtightness; ③ A pulse control unit: capable of precisely setting the pulse period (i.e., "on-off" time) of the microwave output; ④ A temperature control system: employing a non-contact, high-precision infrared thermometer to monitor and provide real-time feedback on material temperature, achieving precise temperature control through linkage with microwave power; ⑤ An atmosphere system: equipped with a mass flow meter for precise control of the type and flow rate of the introduced gas, and a safety pressure relief valve; ⑥ A sample container: using a microwave-transparent corundum crucible or quartz crucible resistant to temperatures above 1000℃.

[0043] Specific operation method:

[0044] Sample loading: Spread the waste positive electrode powder obtained in step 1) evenly in the corundum crucible, with a powder thickness of 8mm (not exceeding 10mm to ensure uniform microwave heating), and then place it in the uniform temperature zone of the microwave oven cavity.

[0045] Sealing and purging: Close the furnace door and ensure it is sealed. Turn on the atmosphere system and first introduce an inert gas (nitrogen or argon) to purge the furnace cavity for 10-15 minutes at a flow rate of 500 mL / min to ensure that all air is completely removed.

[0046] Atmosphere switching and heating: Switch the ventilation gas to oxygen and adjust the flow rate to 300 mL / min; then start the microwave system and temperature control program. The system automatically heats up according to the set pulse mode and power (microwave power is 4 kW, pulse mode adopts intermittent pulse: microwave on for 10 seconds, off for 3 seconds), and heats the material to 1000℃ in about 2~3 minutes.

[0047] Insulation treatment: When the infrared thermometer shows that the material temperature reaches 1000℃, the system automatically maintains this temperature and continues to operate in pulse mode for a total of 5 minutes.

[0048] Cooling and Sampling: After processing, immediately stop microwave emission. Under continuous oxygen flow protection, allow the sample to cool naturally in the furnace chamber to below 200°C (this process takes about 1-2 hours); then shut down the atmosphere system, open the furnace door and remove the sample.

[0049] 3) Water leaching separation: The sample powder treated by pulse microwave is added to room temperature water at a liquid-to-solid ratio of 10:1 and leached for 1 hour. The lithium-rich solution and leaching residue are obtained by filtration. The lithium-rich solution is prepared by lithium carbide precipitation process, with the addition of an appropriate amount of sodium carbonate. After reaction at 90°C, the solid lithium carbonate is obtained by hot filtration.

[0050] 4) Ternary material regeneration: The leaching residue obtained in step 3) and lithium carbonate are mixed evenly at a mass ratio of 1:0.4 and calcined in air at 900°C for 6 hours to regenerate ternary cathode material.

[0051] In this embodiment, the leaching rate of Li in the lithium-rich solution of step 3) was 99.2%, and the leaching rates of Ni, Co and Mn were 0.1%, 0.5% and 0.6%, respectively.

[0052] Example 2

[0053] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials using low-temperature plasma selective etching and reconstruction. The specific steps are as follows:

[0054] 1) Place the waste ternary lithium battery in 2 mol / L salt water for 30 hours of discharge treatment, dry the discharged battery at 85℃, disassemble and separate the positive electrode sheet, soak the positive electrode sheet in N-methylpyrrolidone, separate the current collector in the electrode sheet, filter, wash and dry to obtain waste positive electrode powder.

[0055] 2) Low-temperature plasma treatment: In the low-temperature plasma treatment system, plasma is used to treat ternary powders; the specific equipment and operating methods are as follows:

[0056] This embodiment uses a capacitively coupled parallel-plate low-temperature plasma treatment system for low-temperature plasma treatment. The system includes: ① a plasma generator: using a radio frequency power supply with a frequency of 13.56MHz or 40kHz, and a power continuously adjustable within the range of 100~2000W; ② a vacuum reaction chamber: made of stainless steel, equipped with at least one pair of parallel-plate electrodes (one of the upper or lower electrode connected to the radio frequency power supply, and the other grounded), and the chamber has an observation window, gas inlet and outlet, and a vacuum gauge interface; ③ a vacuum system: a two-stage vacuum unit consisting of a mechanical pump and a molecular pump, ensuring a base vacuum of 10... -3 ④ Gas supply system: Equipped with a multi-channel mass flow controller for precise control of the type and flow rate of the incoming reaction gas and auxiliary gas; ⑤ Sample stage: As one of the electrodes (usually the lower electrode), it has a temperature control function and can maintain the sample temperature at room temperature to 150℃ during the process.

[0057] Specific operation method:

[0058] Sample loading: Spread the waste cathode powder obtained in step 1) evenly in the special tray of the plasma equipment sample stage, with a powder thickness of 4mm (not exceeding 5mm to ensure full contact between plasma and material), and then send the sample stage into the center of the reaction chamber.

[0059] Vacuuming: Close the chamber door, and sequentially start the mechanical pump and molecular pump to evacuate the chamber pressure to below the background vacuum (<5.0×10⁻⁶). -3 Pa);

[0060] Gas introduction and pressure stabilization: Turn on the mass flow meter of the selected gas and introduce the working gas (100 sccm of high-purity oxygen) into the chamber at the set flow rate; through the feedback of the vacuum gauge, fine-tune the inlet valve or pump valve to stabilize the pressure in the chamber at the set working pressure (30 Pa).

[0061] Initiating plasma treatment: After confirming that all parameters are set correctly, start the 13.56MHz RF power supply and gradually apply the set power (1.0W / cm²). 2 At this point, a bright glow discharge can be observed in the chamber through the observation window, indicating that the plasma has been successfully excited.

[0062] Processing: The powder is processed continuously for a set time (50°C, 15 min) at a set power, pressure, and temperature. During this process, highly reactive particles (oxygen free radicals, electrons, etc.) in the plasma physically bombard and chemically react with the powder surface.

[0063] Post-processing and sampling: After the processing time is up, first turn off the RF power supply and the glow discharge disappears; continue to introduce working gas for 1-2 minutes to remove residual active substances in the chamber; turn off the gas and restart the vacuuming program to remove any volatile products that may be generated during the reaction; finally, fill the chamber with high-purity nitrogen or argon to atmospheric pressure, open the chamber door, and take out the processed sample.

[0064] 3) Water leaching separation: The sample powder treated with low temperature plasma was added to room temperature water at a liquid-to-solid ratio of 10:1 and leached for 1 hour. The solution was filtered to obtain a lithium-rich solution and leaching residue. The lithium-rich solution was prepared by lithium carbide precipitation process, with the addition of an appropriate amount of sodium carbonate. After reaction at 90°C, the solution was filtered while hot to obtain solid lithium carbonate.

[0065] 4) Ternary material regeneration: The leaching residue obtained in step 3) and lithium carbonate are mixed evenly at a mass ratio of 1:0.4 and calcined in air at 900°C for 6 hours to regenerate ternary cathode material.

[0066] In this embodiment, the leaching rate of Li in the lithium-rich solution of step 3) was 99.4%, and the leaching rates of Ni, Co and Mn were 0.3%, 0.6% and 0.7%, respectively.

[0067] Example 3

[0068] This embodiment provides a method for selectively recovering lithium from waste ternary cathode materials using pulsed laser-induced surface reconstruction. The specific steps are as follows:

[0069] 1) Place the waste ternary lithium battery in 2 mol / L salt water for 30 hours of discharge treatment, dry the discharged battery at 85℃, disassemble and separate the positive electrode sheet, soak the positive electrode sheet in N-methylpyrrolidone, separate the current collector in the electrode sheet, filter, wash and dry to obtain waste positive electrode powder.

[0070] 2) Pulsed laser processing: Ternary powders are processed using nanosecond pulsed lasers in a pulsed laser; specific equipment and operating methods are as follows:

[0071] This embodiment uses an airflow-type pulsed laser processing system for pulsed laser processing. This system includes: ① A laser generator: employing a nanosecond pulsed laser, such as an Nd:YAG laser (wavelength 1064nm or its frequency doubling wavelength 532nm) or a fiber laser, with a pulse width ranging from 5 to 200 nanoseconds; ② An optical scanning system: including a beam expander, a reflector, and a galvanometer scanning head, used to quickly and accurately guide the laser beam to the processing area; ③ A powder conveying system: consisting of a powder feeder, an airflow generator (air compressor or fan), and nozzles. The airflow carries and accelerates the powder, allowing it to pass through the laser scanning area in a high-speed dispersed state; ④ A reaction chamber and collection system: a sealed stainless steel reaction chamber with a laser-resistant glass window on the side for the laser beam to enter. A cyclone separator and a bag filter are connected to the end of the chamber for collecting the processed powder; ⑤ A control system: an integrated computer for synchronously controlling laser parameters, galvanometer movement, powder feeding rate, and airflow.

[0072] Specific operation method:

[0073] System preparation: Load the waste ternary cathode powder obtained in step 1) into the powder feeder hopper, turn on the air duct system of the reaction chamber to form a stable micro negative pressure (-30Pa) in the chamber, and turn on the cooling system to ensure the normal operating temperature of the laser and optical components;

[0074] Parameter setting and startup: Set the laser parameters (wavelength 1064nm, pulse energy 100mJ, frequency 30kHz, spot diameter at the powder flow focal point 100μm), galvanometer scanning parameters (scanning speed 1000mm / s, linear scanning), and powder feeding parameters (powder feeding rate 15g / min, airflow velocity 20m / s, powder flow concentration 40g / m³) on the control computer. 3 )

[0075] Operation Process: First, start the airflow generator to introduce compressed air; then start the powder feeder to send powder into the airflow, forming a uniform powder flow; after confirming that the powder flow stably passes through the laser scanning area, start the laser to emit light according to the aforementioned settings; the high-energy pulsed laser beam, controlled by a galvanometer, scans and irradiates the high-speed falling powder flow; each powder particle experiences an extremely high energy density (10^-10^-10^-1) at the nanosecond level when passing through the laser beam. 6 ~10 9 W / cm 2 The process involves instantaneous heating, melting, vaporization, and plasma effects, thereby achieving surface modification and lattice activation (the entire process is a continuous feeding process, and the total processing time for a single treatment depends on the total amount of powder to be treated).

[0076] Collection and post-processing: The laser-treated powder is carried by the airflow into the cyclone separator and the end filter, where it is effectively collected; the processing continues until all the powder has been processed; the laser and powder feeder are turned off, and the airflow continues for several minutes to purge the residual powder, and finally the entire system is shut down; the processed powder is taken out from the collector for subsequent steps.

[0077] 3) Water leaching separation: The sample powder treated by pulsed laser is added to room temperature water at a liquid-to-solid ratio of 10:1 and leached for 1 hour. The lithium-rich solution and leaching residue are obtained by filtration. The lithium-rich solution is prepared by lithium carbide precipitation process, with the addition of an appropriate amount of sodium carbonate. After reaction at 90°C, the solid lithium carbonate is obtained by hot filtration.

[0078] 4) Ternary material regeneration: The leaching residue obtained in step 3) and lithium carbonate are mixed evenly at a mass ratio of 1:0.4 and calcined in air at 900°C for 6 hours to regenerate ternary cathode material.

[0079] In this embodiment, the leaching rate of Li in the lithium-rich solution of step 3) was 99.8%, and the leaching rates of Ni, Co and Mn were 0.35%, 0.8% and 0.8% respectively.

[0080] Comparative Example 1

[0081] This comparative example provides a method for selectively recovering lithium from waste ternary cathode materials using pulsed microwave selective excitation and reconstruction. This comparative example is basically the same as Example 1, except that the oxygen atmosphere during microwave pulse treatment in step 2) is replaced with argon.

[0082] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 73.7%, and the leaching rates of Ni, Co and Mn were 5.6%, 6.4% and 8.9%, respectively.

[0083] Comparative Example 2

[0084] This comparative example provides a method for selectively recovering lithium from waste ternary cathode materials using low-temperature plasma selective etching and reconstruction. This comparative example is basically the same as Example 2, except that the oxygen atmosphere during plasma treatment in step 2) is replaced with argon.

[0085] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 78.2%, and the leaching rates of Ni, Co and Mn were 6.5%, 8.1% and 13.1%, respectively.

[0086] Comparative Example 3

[0087] This comparative example provides a method for selectively recovering lithium from waste ternary cathode materials using pulsed laser-induced surface reconstruction. This comparative example is basically the same as Example 3, except that the compressed air atmosphere during pulsed laser treatment in step 2) is replaced with argon gas.

[0088] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 82.7%, and the leaching rates of Ni, Co and Mn were 9.6%, 12.4% and 18.3%, respectively.

[0089] Comparative Example 4

[0090] This comparative example provides a method for selectively recovering lithium from waste ternary cathode materials using pulsed microwave selective excitation and reconstruction. This comparative example is basically the same as Example 1, except that the microwave power during microwave pulse processing in step 2) is adjusted to 6 kW.

[0091] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 99.6%, and the leaching rates of Ni, Co and Mn were 4.7%, 3.9% and 8.7%, respectively.

[0092] Comparative Example 5

[0093] This comparative example provides a method for selectively recovering lithium from waste ternary cathode materials using pulsed microwave selective excitation and reconstruction. This comparative example is basically the same as Example 1, except that in step 2), the microwave pulse processing is performed with the intermittent pulse frequency turned on for 20 seconds and then turned off for 20 seconds.

[0094] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 99.5%, and the leaching rates of Ni, Co and Mn were 4.1%, 3.4% and 8.3%, respectively.

[0095] Comparative Example 6

[0096] This comparative example provides a method for selectively recovering lithium from waste ternary cathode materials using pulsed microwave selective excitation and reconstruction. This comparative example is basically the same as Example 1, except that the microwave pulse processing temperature in step 2) is set to 1200°C.

[0097] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 99.6%, and the leaching rates of Ni, Co and Mn were 4.4%, 3.8% and 8.9%, respectively.

[0098] Comparative Example 7

[0099] This comparative example provides a method for selectively recovering lithium from waste ternary cathode materials using low-temperature plasma selective etching and reconstruction. This comparative example is basically the same as Example 2, except that the plasma treatment temperature in step 2) is adjusted to 80°C.

[0100] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 99.7%, and the leaching rates of Ni, Co and Mn were 5.7%, 4.8% and 10.6%, respectively.

[0101] Comparative Example 8

[0102] This comparative example provides a method for selectively recovering lithium from spent ternary cathode materials using low-temperature plasma selective etching and reconstruction. This comparative example is essentially the same as Example 2, except that the power in step 2) is adjusted to 2.0 W / cm². 2 .

[0103] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 99.6%, and the leaching rates of Ni, Co and Mn were 5.5%, 4.9% and 10.8%, respectively.

[0104] Comparative Example 9

[0105] This comparative example provides a method for selectively recovering lithium from waste ternary cathode materials using pulsed laser-induced surface reconstruction. This comparative example is basically the same as Example 3, except that the pulse frequency in step 2) is increased to 50 kHz.

[0106] The leaching rate of Li in the lithium-rich solution of step 3) of this comparative example was 99.9%, and the leaching rates of Ni, Co and Mn were 8.9%, 11.8% and 16.1%, respectively.

[0107] The reason is that as the temperature increases, the degradation of transition metals nickel, cobalt, and manganese increases, leading to more leaching of these metals. This disrupts the ternary layered structure, resulting in a decrease in the electrochemical performance of the regenerated ternary material. Furthermore, the increased leaching rate of transition metals causes an imbalance in the elemental composition, which is also one of the reasons for the reduced reversible capacity.

[0108] Performance testing of regenerated ternary cathode materials:

[0109] Weigh the regenerated ternary cathode material, conductive agent, and PVDF according to a mass ratio of 92:4:4. First, dissolve the PVDF in NMP (8% concentration), then add the conductive agent and the regenerated ternary cathode material. Stir magnetically until a uniform slurry (viscosity approximately 3000 mPa·s) is formed. Coat the slurry evenly onto aluminum foil. Pre-dry at 80℃ for 30 min, then transfer to a 120℃ vacuum drying oven for 12 h to remove solvent and moisture. Cut into 14 mm diameter discs using a die-cutting machine. Accurately weigh the electrode discs and calculate the active material loading. In a glove box, use 1 mol / L LiPF6 as the electrolyte (EC:DEC:EMC = 1:1:1), a Celgard 2400 polypropylene membrane as the separator, and a lithium electrode as the counter electrode. Place the battery components in the following order: negative electrode shell → lithium electrode (diameter slightly smaller than the shell) → electrolyte-wetted separator → lithium cobalt oxide cathode sheet → spring sheet → cathode shell. Lithium foil (0.4 mm thick) is used directly as both the counter and anode. 90 μL of electrolyte is added dropwise using a microsyringe, ensuring complete wetting of the separator. The battery is sealed using a sealing machine at 4 MPa pressure to ensure airtightness. It is then allowed to stand for 12 hours to allow for full electrolyte wetting.

[0110] The reversible capacity of the recycled ternary cathode materials in each embodiment and comparative example was tested at a rate of 0.1C at room temperature. The test results are shown in Table 1 below:

[0111] Based on the selective lithium extraction results of the above embodiments and comparative examples, and the performance test results of the recycled waste lithium cobalt oxide cathode material, it can be seen that the present invention achieves selective extraction of Li and regenerates high-quality cathode material.

[0112] In Comparative Examples 1-3, under an inert argon atmosphere, the redox environment of the entire reaction was fundamentally altered. Due to the lack of an external oxygen source, at high temperatures, some oxygen (lattice oxygen) in the material's crystal lattice may escape, leading to the formation of a localized reducing environment. This, in turn, results in: 1) the reduction of transition metals: Ni, Co, and Mn are easily reduced to lower valence states (such as Ni). 2+ Co 2+ Mn 2+ / Mn 3+ 1) Low-valence ions typically have larger radii, and their oxides (such as NiO, CoO, and MnO) are less stable than high-valence oxides; 2) Structural instability and damage: The loss of lattice oxygen and the reduction of transition metal valence states can lead to severe damage to the original ternary layered structure. However, the newly formed structure may be a porous, disordered, and defective mixed low-valence oxide rather than a dense and stable structure. This disordered structure is more susceptible to attack; 3) Competition for lithium migration: Although lithium will still migrate out, the stability of the entire material structure will decrease significantly. In subsequent leaching steps, water leaching not only dissolves the lithium compounds on the surface but also more easily corrodes and dissolves those unstable, low-valence Ni, Co, and Mn oxides. Ultimately, this leads to a decrease in the lithium leaching rate due to different structural change paths, but a significant increase in the leaching rate of Ni, Co, and Mn. For regenerated ternary materials, structural damage and the imbalance of transition metal content are the main reasons for the reduced cycle performance.

[0113] The excessively high microwave power in the pulsed microwave treatment in Comparative Example 4, the excessively low intermittent pulse frequency in Comparative Example 5, and the excessively high treatment temperature in Comparative Example 6 all led to a greater leaching of Ni, Co, and Mn in the subsequent leaching reaction. This is because as the power, treatment time, and treatment temperature increase, the high-energy treatment causes greater damage to the transition metals nickel, cobalt, and manganese, resulting in more leaching of the transition metals. Furthermore, the destruction of the ternary layered structure leads to a decrease in the electrochemical performance of the regenerated ternary material. Moreover, the increased leaching rate of the transition metals leads to an imbalance in the elemental ratio, which is also one of the reasons for the decrease in reversible capacity.

[0114] The excessively high plasma treatment temperature in Comparative Example 7 and the excessively high power density in Comparative Example 8 both led to a greater leaching of Ni, Co, and Mn in the subsequent leaching reaction. This is because the excessively high plasma treatment temperature and power density both increased the destruction of transition metals nickel, cobalt, and manganese, resulting in more leaching of transition metals and thus destroying the ternary layered structure, which reduced the electrochemical performance of the regenerated ternary material. Moreover, the increased leaching rate of transition metals led to an imbalance in the elemental ratio, which is also one of the reasons for the reduction in reversible capacity.

[0115] In Comparative Example 9, the excessively high frequency of the pulsed laser also led to a greater leaching of Ni, Co, and Mn in the subsequent leaching reaction. This was because as the temperature increased, the damage to the transition metals nickel, cobalt, and manganese increased, resulting in more leaching of the transition metals and thus destroying the ternary layered structure, which reduced the electrochemical performance of the regenerated ternary material. Moreover, the increased leaching rate of the transition metals led to an imbalance in the elemental ratio, which was also one of the reasons for the decrease in reversible capacity.

[0116] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A method for selective lithium extraction and regeneration of waste ternary cathode materials, characterized in that, Includes the following steps: S1. Place the waste ternary cathode material powder in a reactor for high-energy field in-situ lattice reconstruction treatment to obtain the treated powder. S2. Add the treated powder to the solvent, leaching reaction, solid-liquid separation to obtain lithium-rich solution and leaching residue; S3. Add sodium carbonate to the lithium-rich solution, heat to react, and separate the solid and liquid to obtain lithium carbonate precipitate. Mix the lithium carbonate precipitate with the leaching residue and calcine to obtain the regenerated ternary cathode material. The high-energy field in-situ lattice reconstruction process includes: microwave selective excitation reconstruction, low-temperature plasma selective etching and reconstruction, or pulsed laser-induced surface reconstruction.

2. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 1, characterized in that, The waste ternary cathode material powder is obtained by discharging, dismantling the cathode sheet, and stripping the current collector from waste ternary lithium batteries.

3. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 1, characterized in that, The reactor used for microwave selective excitation and reconstruction is a pulsed microwave sintering system.

4. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 3, characterized in that, The processing parameters of the pulsed microwave sintering system are as follows: microwave power is 3~5kW, pulse mode is intermittent pulse, microwave is turned on for 5~15s, turned off for 2~5s, temperature rises to 950~1050℃ in 2~3min, and the highest temperature is maintained for 4~6min, during which oxygen is introduced at a rate of 200~500mL / min.

5. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 1, characterized in that, The reactor used for the low-temperature plasma selective etching and reconstruction is a low-temperature plasma processing system.

6. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 5, characterized in that, The processing parameters of the low-temperature plasma processing system are as follows: a 12~16MHz radio frequency power supply with a power density of 0.5~1.5W / cm³. 2 The reaction chamber pressure is 10~100Pa, the processing time is 5~30min, the sample temperature is 25~75℃, and oxygen is introduced at 50~200sccm during the process.

7. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 1, characterized in that, The reactor used for pulsed laser-induced surface reconstruction is a pulsed laser processing system.

8. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 7, characterized in that, The processing parameters of the pulsed laser processing system are as follows: using a laser with a wavelength of 1064nm or 532nm, a pulse energy of 50~400mJ / pulse, a pulse frequency of 10~40kHz, a spot diameter of 50~200μm at the focal point of the waste ternary cathode material powder flow, a galvanometer scanning speed of 100~200mm / s, a carrier gas of compressed air or oxygen with a flow rate of 10~50m / s, a powder feeding rate of 5~50g / min, and a powder flow concentration of 10~100g / m³. 3 During this period, a slight negative pressure of -10 to -50 Pa is applied to the cavity.

9. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 1, characterized in that, In step S2, the liquid-to-solid mass ratio of the leaching reaction is (5~50):1; the solvent is water or a dilute weak acid solution.

10. The method for selective lithium extraction and regeneration of waste ternary cathode materials according to claim 1, characterized in that, In step S3, the mass ratio of the lithium carbonate precipitate to the leaching residue is 0.3~0.5):1; the calcination conditions are 800~1000℃ for 5~7h in air atmosphere.

Images