Method for recycling fluorine-containing lithium batteries

Abstract

The application discloses a fluorine-containing lithium battery recycling method, comprising the following steps: S1, stripping the battery to obtain a battery core, and collecting positive and negative electrode sheets respectively; S2, connecting the positive and negative electrode sheets to the positive and negative terminal posts of a direct-current discharge device respectively for low-voltage discharge treatment; S3, using Na2SO4 aqueous solution to perform ultrasonic-assisted deep discharge on the positive and negative electrode sheets after low-voltage discharge treatment until the voltage is stably reduced to <0.1V; and S4, vacuum drying the positive and negative electrode sheets after deep discharge to remove electrolyte, and performing multi-stage crushing and screening to obtain electrode sheet powder; the application realizes ultrasonic-assisted deep discharge, guarantees the purity of target metal ions in a lithium-rich solution, monitors and controls the concentration of Ca 2+ after fluorine removal, avoids the interference of impurity ions, and makes the purity of recycled lithium salt and the purity of recycled copper foil and aluminum foil higher, so that the waste of valuable metals is reduced, and the raw material utilization rate of unit fluorine-containing lithium battery recycling is improved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery recycling technology, specifically a method for recycling fluorine-containing lithium batteries. Background Technology

[0002] Because fluorides in the electrolyte of fluorinated lithium batteries can react with metal ions in the recycling system to form insoluble fluoride precipitates, these precipitates can mix into the recycled lithium salts, causing a decrease in lithium salt purity and failing to meet the quality requirements for secondary utilization. Therefore, lithium batteries need to undergo defluorination treatment before lithium salt precipitation during recycling.

[0003] Traditionally, the removal of fluoride from fluorine-containing lithium batteries involves adding calcium salts to the fluorine-containing solution. Calcium ions react with fluoride ions to form calcium fluoride precipitate, which is then separated into solid and liquid phases through settling or filtration. However, excessive calcium ions can lead to calcium carbonate precipitation, contaminating the lithium salts. Insufficient calcium ions, on the other hand, reduce the lithium salt recovery rate. Furthermore, during the recycling process, the battery electrodes must be discharged first to prevent fire and explosion during subsequent breakage and drying. Current discharge treatment for fluorine-containing lithium batteries primarily uses traditional low-voltage discharge, which can reduce the voltage to around 0.1V, but the discharge cycle is long and the voltage drop is unstable, affecting recycling efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a method for recycling fluorine-containing lithium batteries, which shortens the discharge time and stabilizes the voltage by using ultrasonic-assisted deep discharge, and also improves the recovery of Ca after fluorine removal. 2+ Concentration control, combined with supercritical water leaching technology, enables the high-purity recovery of lithium salts.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for recycling fluorine-containing lithium batteries, comprising the following steps:

[0006] S1. Remove the battery to obtain the battery cell, and collect the positive and negative electrode plates respectively;

[0007] S2. Connect the positive and negative electrode plates to the positive and negative terminals of the DC discharge equipment respectively to perform low-voltage discharge treatment.

[0008] S3. Use Na2SO4 aqueous solution to perform ultrasonic-assisted deep discharge on the positive and negative electrode plates after low-voltage discharge treatment until the voltage stabilizes and drops to <0.1V.

[0009] S4. After deep discharge, the positive and negative electrode sheets are vacuum dried to remove the electrolyte, and then crushed and sieved in multiple stages to obtain electrode powder. The electrode powder is mixed evenly with deionized water and then injected into a high-pressure reactor for supercritical water leaching reaction.

[0010] S5. The reaction products are sieved to recover copper and aluminum foil;

[0011] S6. Perform solid-liquid separation on the slurry passing through the screen, and carry out defluorination pretreatment. After defluorination, adjust the pH of the solution and regulate the Ca content. 2+ concentration;

[0012] S7. Add a lithium precipitation agent to the solution to recover lithium salt, and then perform acid leaching on the reduction residue.

[0013] Preferably, in step S2, the low-voltage discharge process is performed in constant-voltage discharge mode, with a discharge voltage of 0.1V, and the discharge continues to the electrode plate with a current ≤0.01A, thus completing the conventional low-voltage discharge.

[0014] Preferably, in step S3, the Na2SO4 aqueous solution is prepared with a mass concentration of 0.5%, the Na2SO4 aqueous solution completely submerges the electrode, and after the positive and negative electrode are completely immersed in the Na2SO4 aqueous solution in the discharge tank, the distance between the electrode is maintained at 5-8 cm.

[0015] Preferably, in step S3, the ultrasonic-assisted deep discharge uses a discharge tank with an ultrasonic generator installed at the bottom. The ultrasonic frequency is set to 20-30kHz, the power is set to 300-500W, and the discharge is maintained at a constant voltage of 0.1V for 30-60 minutes. The voltage between the electrodes is collected once every 15 minutes.

[0016] Preferably, in step S4, vacuum drying is performed using a vacuum drying chamber, with the drying temperature set at 80-100℃. The vacuum pump is started to evacuate the chamber until the pressure inside reaches -0.09MPa, and this temperature and pressure condition is maintained for insulation. 2- 3h.

[0017] Preferably, in step S4, the multi-stage crushing screen includes a jaw crusher for coarse crushing of the electrode sheets and a planetary ball mill for fine crushing of the coarsely crushed electrode sheets.

[0018] Adjust the discharge port of the jaw crusher to the corresponding setting that can produce coarse particles with a particle size of 10-20mm, and the crushing time is 3-5 minutes.

[0019] Add agate grinding balls to a planetary ball mill with a ball-to-material mass ratio of 5:1. Set the ball mill speed to 200-300 r / min and grind for 1-2 hours.

[0020] Preferably, in step S6, the solid-liquid ratio of electrode powder to deionized water is set to 0.1-25:100;

[0021] The heating and pressurizing system of the reactor heats the water to 350-750℃ at a rate of 5-10℃ / min, while simultaneously injecting nitrogen gas through a high-pressure pump to pressurize it to 15-50MPa, so that the water in the reactor reaches a supercritical state. Under these conditions, a supercritical reduction reaction is carried out for 2-10 hours.

[0022] Preferably, in step S6, the reaction product is sieved using a vibrating screen with a 5mm aperture, an amplitude of 3-5mm, a frequency of 50Hz, and a sieving time of 10-15 minutes.

[0023] The screened current collector fragments are dried and demagnetized. The drying parameters are set as follows:

[0024] Drying temperature: 80-100℃;

[0025] Conveyor belt speed: 0.5-1m / min;

[0026] Hot air velocity: 2-3 m / s;

[0027] Demagnetization is performed using a drum-type magnetic separator with a magnetic field strength of 1000-1500 Gs on the surface of the magnetic drum. The material stays on the surface of the magnetic drum for 3-5 seconds. The demagnetized fragments are then sent to an air classifier.

[0028] Preferably, in step S7, the solid-liquid separation of the slurry is performed using a plate and frame filter press with a filter cloth pore size of 5-10 μm and the parameters set as follows: feed pump flow rate: 10-15 m³ / h. 3 / h;

[0029] Filtration pressure: 0.3-0.5 MPa;

[0030] Filtration time: 20-30 minutes;

[0031] The crude lithium-rich solution is pumped into a ceramic membrane filter for fine filtration to obtain a lithium-rich solution. The operating pressure is set to 0.1-0.2 MPa, the temperature to 25-40℃, and the circulation flow rate to 20-30 m³ / h. 3 / h.

[0032] Preferably, in step S6, during the defluorination pretreatment, Ca(OH)₂ is added to the lithium-rich solution to generate CaF₂, thereby removing F. - When adjusting the solution pH, add 0.5 mol / L H₂SO₄ solution to bring the pH back to 7.5-8.5, and then detect the Ca in the solution using an atomic absorption spectrophotometer. 2+ Concentration, ensuring Ca 2+ Concentration ≤50ppm;

[0033] A stainless steel reactor with a stirrer was used to heat the defluorinated lithium-rich solution to 80-90℃, and then...

[0034] n(Li+ ):n(CO3 2- Slowly add saturated Na2CO3 solution in a ratio of 2:1.05, increase the stirring rate to 400-500 r / min, and continue the reaction for 90-120 min;

[0035] Acid-resistant reactors are used for acid leaching of the reduction residue, equipped with heating, stirring and tail gas absorption devices.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] 1. This invention ensures the purity of target metal ions in lithium-rich solutions through ultrasound-assisted deep discharge, while simultaneously monitoring and controlling Ca after fluoride removal. 2+ Concentration avoids interference from impurity ions, while also increasing the purity of recovered lithium salts, copper foil, and aluminum foil, thereby reducing waste of valuable metals and improving the utilization rate of raw materials recycled per unit of fluorine-containing lithium battery.

[0038] 2. This invention uses the vibration effect of ultrasonic-assisted deep discharge to break the ion diffusion boundary layer on the electrode surface and accelerate the reaction rate between the active material and ions in the electrolyte. Compared with traditional low-voltage discharge, which can only reduce the voltage to about 0.1V, this invention can reduce the risk of fire and explosion during subsequent crushing and drying processes, and also shortens the discharge cycle and stabilizes the discharge. Attached Figure Description

[0039] Figure 1 This is a flowchart of the present invention;

[0040] Figure 2 This is a comparison chart of the duration of ultrasound-assisted deep discharge and traditional low-voltage discharge according to the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0042] Please see Figure 1-2 This invention provides a technical solution: a method for recycling fluorine-containing lithium batteries, comprising the following steps:

[0043] S1. Remove the battery to obtain the battery cell, and collect the positive and negative electrode plates respectively;

[0044] S2. Connect the positive and negative electrode plates to the positive and negative terminals of the DC discharge equipment respectively to perform low-voltage discharge treatment.

[0045] Even when idle, fluorinated lithium batteries may retain a certain amount of charge. During subsequent crushing and drying processes, if the electrodes have a high charge level, they are prone to ignition and explosion due to friction or short circuits. By adopting a constant voltage discharge mode, the electrodes are continuously discharged. When the current is ≤0.01A, it indicates that most of the charge on the electrodes has been released. By controlling the discharge voltage and current, the charge on the electrodes is initially reduced while ensuring discharge safety, thus reducing the load for subsequent deep discharge.

[0046] S3. Use Na2SO4 aqueous solution to perform ultrasonic-assisted deep discharge on the positive and negative electrode plates after low-voltage discharge treatment until the voltage stabilizes and drops to <0.1V.

[0047] A 0.5% Na2SO4 aqueous solution is an electrolyte solution that enhances conductivity and forms a stable current loop between the positive and negative electrodes, providing an ion conduction channel for deep discharge. The liquid surface completely submerges the electrodes and controls the electrode spacing to 5-8 cm, ensuring sufficient contact between the electrodes and the electrolyte, avoiding localized discharge differences due to uneven contact, and guaranteeing discharge uniformity.

[0048] When propagating in solution, vibration and cavitation effects are generated. Vibration can break the ion diffusion boundary layer on the electrode surface, accelerating the reaction rate of active materials, such as lithium compounds in the positive electrode and carbon materials in the negative electrode, with ions in the electrolyte. When the tiny bubbles generated by cavitation break, they release energy, further promoting the electrode reaction. Maintaining a constant voltage discharge of 0.1V for 30-60 minutes, combined with voltage sampling every 15 minutes, can ensure that the voltage stabilizes and drops to <0.1V. Compared with traditional low-voltage discharge, the discharge cycle is significantly shortened, and the safety hazards caused by residual charge on the electrode are completely eliminated.

[0049] S4. After deep discharge, the positive and negative electrode sheets are vacuum dried to remove the electrolyte, and then crushed and sieved in multiple stages to obtain electrode powder. The electrode powder is mixed evenly with deionized water and then injected into a high-pressure reactor for supercritical water leaching reaction.

[0050] Fluorine-containing lithium battery electrolytes are mostly organic solutions, such as carbonates, which are volatile. If residual electrolyte remains during subsequent breakage, it can easily react with air or cause safety issues. Therefore, a vacuum drying oven is used to lower the boiling point of the liquid, allowing the electrolyte to evaporate rapidly at a lower temperature, thus preventing the oxidation or decomposition of the active materials on the electrodes due to high temperatures.

[0051] Supercritical water, with a temperature of 350-750℃ and a pressure of 15-50MPa, possesses unique physicochemical properties, such as a low dielectric constant, a high diffusion coefficient, and strong dissolving power. It can effectively dissolve metal ions, such as lithium, cobalt, and nickel, in electrode powder, while simultaneously disrupting the crystal structure of the electrode material and promoting the reaction between the active material and water. With a solid-liquid ratio of 0.1-25:100 between electrode powder and deionized water, and a reaction time of 2-10 hours, the valuable metals in the electrode powder are fully dissolved into the water, which is beneficial for subsequent separation and recovery.

[0052] S5. The reaction products are sieved to recover copper and aluminum foil;

[0053] The reaction products contain unreacted current collector fragments, copper foil, aluminum foil, magnetic impurities, and a small amount of unreacted electrode material particles. Using the inertial force generated by vibration, the particles are separated according to their size; current collector fragments larger than 5mm remain on the sieve, while slurry smaller than 5mm falls through the sieve. This process preliminarily separates the current collector from other materials, preparing for subsequent copper and aluminum foil purification.

[0054] S6. Perform solid-liquid separation on the slurry passing through the screen, and carry out defluorination pretreatment. After defluorination, adjust the pH of the solution and regulate the Ca content. 2+ concentration;

[0055] S7. Add a lithium precipitation agent to the solution to recover lithium salt, and then perform acid leaching on the reduction residue.

[0056] In step S2, the low-voltage discharge process is performed in constant-voltage discharge mode with a discharge voltage of 0.1V. The discharge continues until the electrode is reached, and the current is ≤0.01A, thus completing the conventional low-voltage discharge.

[0057] In step S3, the Na2SO4 aqueous solution is prepared with a mass concentration of 0.5%. The Na2SO4 aqueous solution completely submerges the electrode. After the positive and negative electrode are completely immersed in the Na2SO4 aqueous solution in the discharge tank, the distance between the electrode is maintained at 5-8 cm.

[0058] In step S3, ultrasonic-assisted deep discharge uses a discharge tank with an ultrasonic generator installed at the bottom. The ultrasonic frequency is set to 20-30kHz, the power is set to 300-500W, and the discharge is maintained at a constant voltage of 0.1V for 30-60 minutes. The voltage between the electrodes is collected every 15 minutes.

[0059] In step S4, vacuum drying is performed using a vacuum drying chamber with the drying temperature set at 80-100℃. The vacuum pump is started to evacuate the chamber until the pressure inside reaches -0.09MPa, and this temperature and pressure condition is maintained for 2-3 hours.

[0060] In step S4, the multi-stage crushing screen includes a jaw crusher for coarse crushing of the electrode sheets and a planetary ball mill for fine crushing of the coarsely crushed electrode sheets.

[0061] Adjust the discharge port of the jaw crusher to the corresponding setting that can produce coarse particles with a particle size of 10-20mm, and the crushing time is 3-5 minutes.

[0062] Add agate grinding balls to a planetary ball mill with a ball-to-material mass ratio of 5:1. Set the ball mill speed to 200-300 r / min and grind for 1-2 hours.

[0063] In step S6, the solid-liquid ratio of electrode powder to deionized water is set to 0.1-25:100;

[0064] The heating and pressurizing system of the reactor heats the water to 350-750℃ at a rate of 5-10℃ / min, while simultaneously injecting nitrogen gas through a high-pressure pump to pressurize it to 15-50MPa, so that the water in the reactor reaches a supercritical state. Under these conditions, a supercritical reduction reaction is carried out for 2-10 hours.

[0065] In step S6, the reaction product is sieved using a vibrating screen with a 5mm aperture, an amplitude of 3-5mm, a frequency of 50Hz, and a sieving time of 10-15 minutes. The material remaining on the screen mainly consists of copper foil and aluminum foil fragments, mixed with a small amount of magnetic impurities and unreacted electrode material particles.

[0066] The debris collected on the sieve is transferred to an air classifier with an air volume of 15-20 m³ / h. 3 / h, using airflow to blow away the attached light electrode powder, such as carbon powder and delithiated cathode material, and collect the heavy current collector fragments. The pre-cleaned current collector fragments are evenly spread on the dryer conveyor belt, with the spreading thickness controlled at 1-2cm to avoid stacking and uneven drying.

[0067] The screened current collector fragments are dried and demagnetized. The drying parameters are set as follows:

[0068] Drying temperature: 80-100℃. Too high a temperature can easily cause aluminum foil to oxidize, while too low a temperature will affect drying efficiency.

[0069] Conveyor belt speed: 0.5-1m / min;

[0070] Hot air velocity: 2-3 m / s, using a bottom-in, top-out hot air circulation method to ensure full contact between the hot airflow and the material. A humidity sensor is installed at the dryer outlet to monitor the moisture content of the collector fragments in real time, ensuring that the moisture content after drying is ≤0.5%, that it feels dry when squeezed by hand, and that the fragments naturally disperse when released. After drying, the collector fragments are cooled in the cooling section by air at room temperature for 3-5 minutes before being collected in a sealed silo for later use.

[0071] Demagnetization is performed using a drum-type magnetic separator with a magnetic field strength of 1000-1500 Gs on the surface of the magnetic drum. The material stays on the surface of the magnetic drum for 3-5 seconds. The demagnetized fragments are then sent to an air classifier.

[0072] The dried current collector fragments are fed into the magnetic separator at a uniform speed via a conveyor belt. As the fragments pass over the magnetic drum surface, ferromagnetic impurities, such as iron filings from battery casings and iron powder from equipment wear, are attracted to the magnetic drum surface by the magnetic field. These impurities then fall off as the drum rotates to the demagnetized zone and enter the impurity collection tank. A random sample of 100g of demagnetized current collector fragments is taken, and the magnetic impurity content is tested using a magnetic separator tube to ensure that the residual magnetic impurity content is ≤0.1%. If the impurity content exceeds the standard, the magnetic field strength of the magnetic drum or the feeding speed needs to be adjusted, and demagnetization must be repeated. (Note: The last sentence about aluminum foil density is unrelated and appears to be a separate, incomplete thought.) 3 The density of the copper foil is 8.9 g / cm³. 3 Adjust the airflow to 25-30m 3 / h, aluminum foil is more easily carried by airflow;

[0073] After demagnetization, the current collector fragments are fed into an airflow separator. Lighter aluminum foil fragments are carried by the airflow into the upper separation chamber and fall into the aluminum foil collection bin; heavier copper foil fragments fall into the lower separation chamber due to gravity and enter the copper foil coarse material bin. A heavy medium suspension is prepared by mixing ferrosilicon powder with water, and the density is adjusted to 5.0-6.0 g / cm³. 3 The density is between that of aluminum foil and copper foil, and it is injected into the heavy medium sorting tank.

[0074] The coarse copper foil after air separation is fed into the sorting tank. The aluminum foil, due to its lower density than the suspension, floats and enters the refined aluminum foil hopper through the overflow port. The copper foil, due to its higher density than the suspension, sinks and enters the refined copper foil hopper through the bottom discharge port. The sorted aluminum foil and refined copper foil are rinsed with deionized water 2-3 times to remove the attached heavy media powder. Then, they are centrifuged to dehydrate at a speed of 1500 r / min for 3-5 minutes. After that, they are transferred to a drying oven at a temperature of 60-80℃ for 1-2 hours.

[0075] Feed pump flow rate: 10-15 m³ / h 3 / h;

[0076] Filtration pressure: 0.3-0.5 MPa;

[0077] Filtration time: 20-30 minutes;

[0078] Wait until the filter cake thickness reaches 20-30mm and the filtrate flow rate is ≤0.1m³. 3 When the feed rate reaches 100 m / h, stop feeding, start the pressing pump, and press with 0.6-0.8 MPa compressed air for 10-15 minutes to reduce the moisture content of the filter cake to 30%-40%. Remove the filter cake; the filtrate is a lithium-rich crude liquid. Collect the filtrate into the storage tank.

[0079] The undersize slurry mainly consists of Li-containing materials. + F - It consists of a lithium-rich solution containing a small amount of impurity ions, and a reduction residue containing delithiated cathode material, carbon powder, and unreacted particles.

[0080] The crude lithium-rich solution is pumped into a ceramic membrane filter for fine filtration to obtain a lithium-rich solution. The operating pressure is set to 0.1-0.2 MPa, the temperature to 25-40℃, and the circulation flow rate to 20-30 m³ / h. 3 / h, fine particles in the solution, such as carbon dust and nano-sized delithiation particles, are retained by the membrane, and the permeate is a purified lithium-rich solution, Li + Concentration 1-3 g / L, turbidity ≤5 NTU;

[0081] When the membrane flux drops to 50% of its initial value, backwash with 0.5 mol / L HCl solution for 30 min to restore membrane performance.

[0082] In step S6, during the defluorination pretreatment, Ca(OH)₂ is added to the lithium-rich solution to generate CaF₂, thereby removing fluoride. - .

[0083] Transfer the purified lithium-rich solution into the reactor, turn on the stirrer (200-300 r / min), and monitor the pH value of the solution with a pH meter.

[0084] Slowly add 10% Ca(OH)2 suspension, adjust pH to 9-10, and continue stirring for 60 minutes to allow F to... - With Ca 2+ Full reaction;

[0085] After standing for 30 minutes, filter using a plate and frame filter press, and collect the defluorinated lithium-rich solution. - If the concentration is ≤10ppm, the CaF2 filter residue shall be disposed of in accordance with hazardous waste regulations;

[0086] The pH of the lithium-rich solution after defluorination is 9-10, while the subsequent lithium precipitation reaction requires weakly alkaline conditions, at pH 7.5-8.5. Therefore, 0.5 mol / L H₂SO₄ solution needs to be added before lithium precipitation to adjust the pH back to the target range. During this adjustment, acid should be added while stirring to avoid localized pH drops that could lead to lithium precipitation. + Loss. After defluorination, the Ca in the solution needs to be detected by atomic absorption spectrophotometry. 2+ Concentration, ensure ≤50ppm. If Ca... 2+ If the concentration is too high, it will react with CO3 during lithium precipitation. 2- The reaction produces CaCO3 precipitate, which mixes into the Li2CO3 product, leading to a decrease in purity, such as Ca... 2+At a concentration of 100 ppm, the purity of lithium salts may decrease from 99.5% to 98.8%. If Ca... 2+ If the concentration exceeds the standard, add 0.1 mol / L Na₂CO₃ solution, stir for 30 minutes, and then filter to remove CaCO₃.

[0087] A stainless steel reactor with a stirrer is used to heat the defluorinated lithium-rich solution to 80-90℃, and the reaction is carried out at the ratio of n(Li+):n(CO3). 2- The ratio is 2:1.05, with a 5% excess to ensure Li + After complete precipitation, slowly add saturated Na₂CO₃ solution, increase the stirring rate to 400-500 rpm, and continue the reaction for 90-120 minutes. During this period, take samples every 15 minutes to detect the Li content in the supernatant. + Concentration, up to Li + Stop the reaction when the concentration is ≤0.05g / L;

[0088] Turn off the heating device, cool the slurry to room temperature, and let it stand for 60 minutes to allow the Li2CO3 to settle completely. Control the excess Na2CO3 ratio to not exceed 8% to avoid Na... + Excessive residual lithium salts affect their purity; using hot water during washing can reduce the loss of Li2CO3 solubility.

[0089] Acid-resistant reactors are used for acid leaching of the reduction residue, equipped with heating, stirring and tail gas absorption devices.

[0090] The main component of the reduction residue is lithium-delithiated cathode material, such as Li1- X CoO2, Li1- X NiMnCoO2 carbon powder is separated from the carbon powder by dissolving valuable metals through acid leaching. The reduction residue is mixed with deionized water at a solid-liquid ratio of 1:5-1:8, added to the reaction vessel, and stirred at a speed of 200-300 r / min.

[0091] Slowly add concentrated H₂SO₄ (98% concentration) to adjust the pH of the solution to 1-2. Simultaneously add 30% H₂O₂ as a reducing agent, using 5%-8% of the mass of the reduction residue. Add Co... 3+ Ni 3+ Reduced to readily soluble Co 2+ Ni 2+ ;

[0092] Heat to 70-80℃ and react for 120-180 minutes, taking samples every 30 minutes to detect Co in the leachate. 2+ Ni 2+ Mn 2 +The concentration was adjusted until the metal leaching rate was ≥95%, at which point the reaction was stopped. After the acid leaching reaction was completed, the slurry was cooled to below 40°C and filtered using a plate and frame filter press. The filter cake was high-purity carbon powder with a moisture content ≤30%.

[0093] Wash the filter cake 2-3 times with deionized water, and add the washing liquid to the metal leaching solution to improve the metal recovery rate. Carbon powder treatment: Transfer the filter cake to a drying oven at 100-110℃ and dry. 2- After 3 hours, a carbon powder product with a purity of ≥98% was obtained, which can be used to prepare anode materials or fuels;

[0094] Leachate treatment: Co was separated by extraction. 2+ Ni 2+ Mn 2+ For example, using P204 extractant to separate Mn 2+ P507 extractant for the separation of Co 2+ with Ni 2+ Then, the corresponding metal salts, such as CoSO4·7H2O and NiSO4·6H2O, are prepared through precipitation and crystallization. H2O2 needs to be added slowly to prevent local over-addition and decomposition. The reaction temperature should not exceed 85℃ to avoid acid mist pollution caused by H2SO4 volatilization. The acid leaching tail gas contains a small amount of SO2 and needs to be treated by an alkaline absorption tower, such as a 10% NaOH solution, before being discharged. The extraction method for separating metal ions and the treatment of leaching tail gas are existing technologies and will not be described in detail here.

[0095] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for recycling fluorine-containing lithium batteries, characterized in that, Includes the following steps: S1. Remove the battery to obtain the battery cell, and collect the positive and negative electrode plates respectively; S2. Connect the positive and negative electrode plates to the positive and negative terminals of the DC discharge equipment respectively to perform low-voltage discharge treatment. S3. Use Na2SO4 aqueous solution to perform ultrasonic-assisted deep discharge on the positive and negative electrode plates after low-voltage discharge treatment until the voltage stabilizes and drops to <0.1V. S4. After deep discharge, the positive and negative electrode sheets are vacuum dried to remove the electrolyte, and then crushed and sieved in multiple stages to obtain electrode powder. The electrode powder is mixed evenly with deionized water and then injected into a high-pressure reactor for supercritical water leaching reaction. S5. The reaction products are sieved to recover copper and aluminum foil; S6. Perform solid-liquid separation on the slurry passing through the screen, and carry out defluorination pretreatment. After defluorination, adjust the pH of the solution and regulate the Ca content. 2+ concentration; S7. Add a lithium precipitation agent to the solution to recover lithium salt, and then perform acid leaching on the reduction residue.

2. The method for recycling fluorine-containing lithium batteries according to claim 1, characterized in that: In step S2, the low-voltage discharge process is performed in constant-voltage discharge mode with a discharge voltage of 0.1V. The discharge continues until the electrode is reached, and the current is ≤0.01A, thus completing the conventional low-voltage discharge.

3. The method for recycling fluorine-containing lithium batteries according to claim 2, characterized in that: In step S3, the Na2SO4 aqueous solution is prepared with a mass concentration of 0.5%. The Na2SO4 aqueous solution completely submerges the electrode. After the positive and negative electrode are completely immersed in the Na2SO4 aqueous solution in the discharge tank, the distance between the electrode is maintained at 5-8 cm.

4. The method for recycling fluorine-containing lithium batteries according to claim 3, characterized in that: In step S3, ultrasonic-assisted deep discharge uses a discharge tank with an ultrasonic generator installed at the bottom. The ultrasonic frequency is set to 20-30kHz, the power is set to 300-500W, and the discharge is maintained at a constant voltage of 0.1V for 30-60 minutes. The voltage between the electrodes is collected every 15 minutes.

5. The method for recycling fluorine-containing lithium batteries according to claim 4, characterized in that: In step S4, vacuum drying is performed using a vacuum drying chamber with the drying temperature set at 80-100℃. The vacuum pump is started to evacuate the chamber until the pressure inside reaches -0.09MPa, and this temperature and pressure condition is maintained for 2-3 hours.

6. The method for recycling fluorine-containing lithium batteries according to claim 2, characterized in that: In step S4, the multi-stage crushing screen includes a jaw crusher for coarse crushing of the electrode sheets and a planetary ball mill for fine crushing of the coarsely crushed electrode sheets. Adjust the discharge port of the jaw crusher to the corresponding setting that can produce coarse particles with a particle size of 10-20mm, and the crushing time is 3-5 minutes. Add agate grinding balls to a planetary ball mill with a ball-to-material mass ratio of 5:

1. Set the ball mill speed to 200-300 r / min and grind for 1-2 hours.

7. The method for recycling fluorine-containing lithium batteries according to claim 6, characterized in that: In step S6, the solid-liquid ratio of electrode powder to deionized water is set to 0.1-25:100; The heating and pressurizing system of the reactor heats the water to 350-750℃ at a rate of 5-10℃ / min, while simultaneously injecting nitrogen gas through a high-pressure pump to pressurize it to 15-50MPa, so that the water in the reactor reaches a supercritical state. Under these conditions, a supercritical reduction reaction is carried out for 2-10 hours.

8. The method for recycling fluorine-containing lithium batteries according to claim 7, characterized in that: In step S6, the reaction product is sieved using a vibrating screen with a 5mm aperture, an amplitude of 3-5mm, a frequency of 50Hz, and a sieving time of 10-15 minutes. The screened current collector fragments are dried and demagnetized. The drying parameters are set as follows: Drying temperature: 80-100℃; Conveyor belt speed: 0.5-1m / min; Hot air velocity: 2-3 m / s; Demagnetization is performed using a drum-type magnetic separator with a magnetic field strength of 1000-1500 Gs on the surface of the magnetic drum. The material stays on the surface of the magnetic drum for 3-5 seconds. The demagnetized fragments are then sent to an air classifier.

9. A method for recycling fluorine-containing lithium batteries according to claim 2, characterized in that: In step S7, the solid-liquid separation of the slurry is performed using a plate and frame filter press with a filter cloth pore size of 5-10 μm. The parameters are set as follows: feed pump flow rate: 10-15 m³ / h. 3 / h; Filtration pressure: 0.3-0.5 MPa; Filtration time: 20-30 minutes; The crude lithium-rich solution is pumped into a ceramic membrane filter for fine filtration to obtain a lithium-rich solution. The operating pressure is set to 0.1-0.2 MPa, the temperature to 25-40℃, and the circulation flow rate to 20-30 m³ / h. 3 / h.

10. A method for recycling fluorine-containing lithium batteries according to claim 9, characterized in that: In step S6, during the defluorination pretreatment, Ca(OH)₂ is added to the lithium-rich solution to generate CaF₂, thereby removing fluoride. - When adjusting the solution pH, add 0.5 mol / L H₂SO₄ solution to bring the pH back to 7.5-8.5, and then detect the Ca in the solution using an atomic absorption spectrophotometer. 2+ Concentration, ensuring Ca 2+ Concentration ≤50ppm; A stainless steel reactor with a stirrer is used to heat the defluorinated lithium-rich solution to 80-90℃, and then proceed according to n(Li + ):n(CO3 2- Slowly add saturated Na2CO3 solution in a ratio of 2:1.05, increase the stirring rate to 400-500 r / min, and continue the reaction for 90-120 min; Acid-resistant reactors are used for acid leaching of the reduction residue, equipped with heating, stirring and tail gas absorption devices.

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