A method of recycling a battery

Abstract

This invention belongs to the field of battery recycling technology, and specifically relates to a battery recycling method, including the following steps: (1) disassembling and separating waste lithium batteries after discharge to obtain positive electrode sheets, cleaning and drying the positive electrode sheets; (2) coating the surface of the dried positive electrode sheets with an organic intercalation solvent; (3) placing the dried positive electrode sheets in a sealed container, introducing CO2 into the sealed container and raising the temperature and pressure in the sealed container to make CO2 supercritical, and then using supercritical CO2 to perform intercalation treatment on the surface of the positive electrode sheets under heat preservation and pressure preservation; (4) depressurizing the sealed container to reduce the pressure in the sealed container to normal pressure; (5) taking out the positive electrode sheets in the sealed container and subjecting them to electron beam irradiation; (6) vibrating and peeling off the electron beam irradiated material to obtain black powder.

Description

Technical Field

[0001] This invention belongs to the field of battery recycling technology, and specifically relates to a method for recycling batteries. Background Technology

[0002] Lithium-ion battery cathode sheets are composite materials comprising aluminum foil, a PVDF binder coated on the aluminum foil, and black powder (positive electrode active material) adhered to the binder. During the recycling of spent lithium-ion batteries, the positive electrode black powder is the core valuable component. Therefore, efficiently separating the black powder from the aluminum foil is a crucial step for subsequent resource recovery. Existing methods for separating positive electrode black powder mainly include high-temperature roasting and chemical alkaline washing. High-temperature roasting requires temperatures above 600°C to pyrolyze the PVDF binder, resulting in high energy consumption, the generation of harmful gases such as HF, and the high temperature can cause lattice collapse and volatilization of valuable metals in the cathode material, reducing the black powder recovery rate. Chemical alkaline washing consumes large amounts of strong alkali, producing high-salt wastewater, and the alkaline solution easily penetrates into the active material lattice, causing lithium loss, leading to high subsequent wastewater treatment costs.

[0003] Given the aforementioned problems, it is necessary to provide a new battery recycling method. Summary of the Invention

[0004] This invention aims to at least solve one of the technical problems existing in related technologies. To this end, this invention proposes a battery recycling method that has low energy consumption, a high recovery rate of black powder, and high quality of the recovered black powder.

[0005] The above-mentioned technical objective of the present invention is achieved through the following technical solution: A method for recycling batteries includes the following steps: (1) Discharge the waste lithium battery and disassemble it to obtain the positive electrode sheet. Clean the positive electrode sheet and dry it. (2) Coating the surface of the dried positive electrode with an organic intercalation solvent; (3) Place the treated positive electrode in a sealed container, introduce CO2 into the sealed container and raise the temperature and pressure in the sealed container to make CO2 become supercritical, and then use supercritical CO2 to perform intercalation treatment on the surface of the positive electrode under heat preservation and pressure preservation. (4) Depressurize the sealed container to reduce the pressure inside to atmospheric pressure; (5) After removing the positive electrode from the sealed container, perform electron beam irradiation; (6) Vibrate and peel off the material after electron beam irradiation to obtain black powder.

[0006] In one embodiment, in step (1), the discharge is to connect the waste lithium battery to a programmable high-power resistor load box via wires and slowly discharge it to a safe voltage with a constant small current.

[0007] In one embodiment, in step (1), the voltage of the discharged waste lithium battery is ≤0.05V.

[0008] In one embodiment, in step (1), the cleaning is performed by placing the positive electrode sheet in an organic solvent for cleaning.

[0009] In one embodiment, in step (1), the cleaning is performed by ultrasonic cleaning 2-3 times at a power of 80-120W, each time for 8-15 minutes.

[0010] In one embodiment, in step (1), the drying is performed at 60-75°C for 2-5 hours.

[0011] In one embodiment, in step (2), the organic intercalation solvent is a mixture of benzyl alcohol, ethylene glycol butyl ether and dipropylene glycol methyl ether in a weight ratio of (3-5):(3-5):(2-4).

[0012] In one embodiment, in step (3), the sealed container is a supercritical reactor.

[0013] In one embodiment, in step (3), the temperature after the increase is 32-50°C and the pressure after the increase is 7.5-10 MPa.

[0014] In one embodiment, in step (3), the heat preservation and pressure holding time is 30-90 minutes.

[0015] In one embodiment, in step (3), the intercalation process is also accompanied by stirring at a rate of 50-100 r / min.

[0016] In one embodiment, in step (4), the time taken for depressurization is 1-5 seconds.

[0017] In one embodiment, in step (4), the CO2 and gaseous organic matter generated in the sealed container are recovered simultaneously with the depressurization.

[0018] In one embodiment, in step (5), after the positive electrode is taken out, it is laid flat on a conveyor belt and then irradiated with an electron beam. The thickness of the material after being laid flat is 0.5-2cm, and the conveying speed of the conveyor belt is 5-10m / min.

[0019] In one embodiment, in step (5), the electron beam irradiation parameters are: the electron beam irradiation energy is 1-5 MeV, the electron beam current is 1-10 mA, and the electron beam dose in the irradiated area is 100-300 kGy.

[0020] In one embodiment, in step (6), the vibration stripping is carried out using a linear vibrating screen with a vibration frequency of 30-100Hz, a mesh size of 20-80 mesh, and a material conveying speed of 5-10m / min on the linear vibrating screen.

[0021] The beneficial effects of this invention are: (1) The recycling method of the battery of the present invention first utilizes supercritical CO2, with its strong permeability, in conjunction with a specific organic intercalation solvent to rapidly penetrate into the micro-nano gaps between the aluminum current collector, PVDF binder, and black powder material of the positive electrode sheet. Through the physical expansion effect, uniform expansion of the gaps between the layers is achieved, increasing the interlayer gap. At the same time, the organic intercalation solvent can act on the PVDF binder, causing the PVDF binder to swell and thus its mechanical strength to decrease sharply, breaking the tight bonding state between the layers. Subsequently, rapid depressurization is performed (reducing to atmospheric pressure within 1-5 seconds). The supercritical CO2 at the interface between the PVDF binder and the supercritical CO2 instantly vaporizes and expands, generating a powerful microscopic bursting force. This bursting force can effectively... The aluminum foil-PVDF binder interface is prefabricated with a continuous micron-level separation layer and a large number of microcracks, which allows the subsequent electron beam to penetrate uniformly into the binder layer. At the same time, due to the swelling of the PVDF binder caused by the organic intercalation solvent, the spacing between PVDF molecules increases. After the PVDF binder is irradiated by the electron beam, the CC and CF in the PVDF molecules are more likely to break, and after breaking, they are less likely to re-crosslink. This greatly improves the binder degradation efficiency, reduces the electron beam irradiation dose, and reduces the process cost. Through the synergistic effect of "intercalation and crack expansion + electron beam irradiation degradation", the final black powder recovery rate can reach more than 98.7% and the purity of the black powder can reach more than 99.2%. (2) The recycling method of the battery of the present invention does not require high temperature or strong acid and alkali reagents. Supercritical CO2 can be recycled. The black powder after stripping has a complete crystal form and no obvious agglomeration. The aluminum current collector is non-corrosive and can be directly reused. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments.

[0023] Example 1: A method for recycling batteries, characterized by comprising the following steps: (1) Connect the waste lithium battery to a programmable high-power resistor load box through wires and slowly discharge it with a constant small current until the voltage is ≤0.05V. After discharge, disassemble and separate the positive electrode sheet. Place the positive electrode sheet in anhydrous ethanol and clean it three times with an ultrasonic power of 80W for 15min each time. Then dry it in vacuum at 60℃ for 5h. (2) Coating the surface of the dried positive electrode with an organic intercalation solvent, which is a mixture of benzyl alcohol, ethylene glycol butyl ether and dipropylene glycol methyl ether in a weight ratio of 3:3:2; (3) Place the treated positive electrode in a supercritical reactor, introduce CO2 into the supercritical reactor and raise the temperature in the supercritical reactor to 32°C, raise the pressure in the supercritical reactor to 7.5 MPa, so that CO2 becomes supercritical and the supercritical CO2 covers the positive electrode in the supercritical reactor. Maintain a stirring speed of 50 r / min and keep the temperature and pressure for 90 min so that the supercritical CO2 can perform intercalation treatment on the surface of the positive electrode. (4) Depressurize the supercritical reactor to reduce the pressure in the supercritical reactor to atmospheric pressure. The time required for depressurization is 3s, and CO2 and the generated gaseous organic matter are recovered. (5) After taking out the positive electrode sheet from the supercritical reactor, place it on the conveyor belt and spread it flat for electron beam irradiation. The thickness of the material after spreading is 0.5 cm, the conveyor belt speed is 10 m / min, and the electron beam irradiation parameters are: the electron beam irradiation energy is 1 MeV, the electron beam current is 1 mA, and the electron beam dose in the irradiation area is 100 kGy. (6) The material after electron beam irradiation is separated by vibration using a linear vibrating screen. The vibration frequency of the linear vibrating screen is 30Hz, the mesh size of the linear vibrating screen is 20 mesh, and the conveying speed of the material on the linear vibrating screen is 5m / min. Black powder and aluminum foil are separated. The recovery rate of the obtained black powder is 98.7%, and the purity of the black powder is 99.2%.

[0024] Example 2: A method for recycling batteries, characterized by comprising the following steps: (1) Connect the waste lithium battery to a programmable high-power resistor load box through wires, and slowly discharge it with a constant small current until the voltage is ≤0.05V. After discharge, disassemble and separate the positive electrode sheet. Place the positive electrode sheet in anhydrous ethanol and clean it twice with an ultrasonic cleaner of 120W for 8 minutes each time. Then dry it in vacuum at 75℃ for 2 hours. (2) Coating the surface of the dried positive electrode with an organic intercalation solvent, which is a mixture of benzyl alcohol, ethylene glycol butyl ether and dipropylene glycol methyl ether in a weight ratio of 5:5:4; (3) Place the treated positive electrode in a supercritical reactor, introduce CO2 into the supercritical reactor and raise the temperature in the supercritical reactor to 50°C, raise the pressure in the supercritical reactor to 10MPa, so that CO2 becomes supercritical, and make the supercritical CO2 submerge the positive electrode in the supercritical reactor. Maintain a stirring speed of 100r / min and keep the temperature and pressure for 30min so that the supercritical CO2 can perform intercalation treatment on the surface of the positive electrode. (4) Depressurize the supercritical reactor to reduce the pressure in the supercritical reactor to atmospheric pressure. The time required for depressurization is 5s, and CO2 and the generated gaseous organic matter are recovered. (5) After taking out the positive electrode sheet from the supercritical reactor, place it on the conveyor belt and spread it flat for electron beam irradiation. The thickness of the material after spreading is 2cm, the conveyor belt speed is 5m / min, and the electron beam irradiation parameters are: the electron beam irradiation energy is 5MeV, the electron beam current is 10mA, and the electron beam dose in the irradiation area is 300kGy. (6) The material after electron beam irradiation is separated by vibration using a linear vibrating screen. The vibration frequency of the linear vibrating screen is 100Hz, the mesh size of the linear vibrating screen is 80 mesh, and the conveying speed of the material on the linear vibrating screen is 10m / min. Black powder and aluminum foil are separated. The recovery rate of the obtained black powder is 98.9%, and the purity of the black powder is 99.3%.

[0025] Example 3: A method for recycling batteries, characterized by comprising the following steps: (1) Connect the waste lithium battery to a programmable high-power resistor load box through wires, and slowly discharge it with a constant small current until the voltage is ≤0.05V. After discharge, disassemble and separate the positive electrode sheet. Place the positive electrode sheet in anhydrous ethanol and clean it twice with an ultrasonic cleaner of 100W for 10min each time. Then dry it in vacuum at 70℃ for 3h. (2) Coating the surface of the dried positive electrode with an organic intercalation solvent, which is a mixture of benzyl alcohol, ethylene glycol butyl ether and dipropylene glycol methyl ether in a weight ratio of 4:4:3; (3) Place the treated positive electrode in a supercritical reactor, introduce CO2 into the supercritical reactor and raise the temperature in the supercritical reactor to 35°C, raise the pressure in the supercritical reactor to 8MPa, so that CO2 becomes supercritical, and make the supercritical CO2 submerge the positive electrode in the supercritical reactor. Maintain a stirring speed of 80r / min and keep the temperature and pressure for 60min so that the supercritical CO2 can perform intercalation treatment on the surface of the positive electrode. (4) Depressurize the supercritical reactor to reduce the pressure in the supercritical reactor to atmospheric pressure. The time required for depressurization is 4s, and CO2 and the generated gaseous organic matter are recovered. (5) After taking out the positive electrode sheet from the supercritical reactor, place it on the conveyor belt and spread it flat for electron beam irradiation. The thickness of the material after spreading is 1 cm, the conveyor belt speed is 6 m / min, and the electron beam irradiation parameters are: the electron beam irradiation energy is 3 MeV, the electron beam current is 6 mA, and the electron beam dose in the irradiation area is 260 kGy. (6) The material after electron beam irradiation is vibrated and stripped using a linear vibrating screen. The vibration frequency of the linear vibrating screen is 80 Hz, the mesh size of the linear vibrating screen is 40 mesh, and the conveying speed of the material on the linear vibrating screen is 6 m / min. Black powder and aluminum foil are separated. The recovery rate of the obtained black powder is 99.2%, and the purity of the black powder is 99.6%.

[0026] Comparative Example 1: (The only difference from Example 3 is that supercritical CO2 was not used for treatment before electron beam irradiation) A method for recycling batteries, characterized by comprising the following steps: (1) Connect the waste lithium battery to a programmable high-power resistor load box through wires, and slowly discharge it with a constant small current until the voltage is ≤0.05V. After discharge, disassemble and separate the positive electrode sheet. Place the positive electrode sheet in anhydrous ethanol and clean it twice with an ultrasonic cleaner of 100W for 10min each time. Then dry it in vacuum at 70℃ for 3h. (2) Coating the surface of the dried positive electrode with an organic intercalation solvent, which is a mixture of benzyl alcohol, ethylene glycol butyl ether and dipropylene glycol methyl ether in a weight ratio of 4:4:3; (3) The processed positive electrode sheet was laid flat on the conveyor belt and then irradiated with electron beam. The thickness of the material after laying was 1 cm, the conveyor belt speed was 6 m / min, and the electron beam irradiation parameters were: the electron beam irradiation energy was 3 MeV, the electron beam current was 6 mA, and the electron beam dose in the irradiated area was 260 kGy. (4) The material after electron beam irradiation is separated by vibration using a linear vibrating screen. The vibration frequency of the linear vibrating screen is 80 Hz, the mesh size of the linear vibrating screen is 40 mesh, and the conveying speed of the material on the linear vibrating screen is 6 m / min. Black powder and aluminum foil are separated. The recovery rate of the black powder is 92.5%, and the purity of the black powder is 97.3%.

[0027] Comparative Example 2: (The only difference from Example 3 is that it is not coated with an organic intercalation solvent) A method for recycling batteries, characterized by comprising the following steps: (1) Connect the waste lithium battery to a programmable high-power resistor load box through wires, and slowly discharge it with a constant small current until the voltage is ≤0.05V. After discharge, disassemble and separate the positive electrode sheet. Place the positive electrode sheet in anhydrous ethanol and clean it twice with an ultrasonic cleaner of 100W for 10min each time. Then dry it in vacuum at 70℃ for 3h. (2) Place the treated positive electrode in a supercritical reactor, introduce CO2 into the supercritical reactor and raise the temperature in the supercritical reactor to 35°C, raise the pressure in the supercritical reactor to 8MPa, so that CO2 becomes supercritical, and make the supercritical CO2 submerge the positive electrode in the supercritical reactor. Maintain a stirring speed of 80r / min and keep the temperature and pressure for 60min so that the supercritical CO2 can perform intercalation treatment on the surface of the positive electrode. (3) Depressurize the supercritical reactor to reduce the pressure in the supercritical reactor to atmospheric pressure. The time required for depressurization is 4s, and CO2 and the generated gaseous organic matter are recovered. (4) After taking out the positive electrode sheet from the supercritical reactor, place it on the conveyor belt and spread it flat for electron beam irradiation. The thickness of the material after spreading is 1 cm, the conveyor belt speed is 6 m / min, and the electron beam irradiation parameters are: the electron beam irradiation energy is 3 MeV, the electron beam current is 6 mA, and the electron beam dose in the irradiation area is 260 kGy. (5) The material after electron beam irradiation was separated by vibration using a linear vibrating screen. The vibration frequency of the linear vibrating screen was 80 Hz, the mesh size of the linear vibrating screen was 40 mesh, and the conveying speed of the material on the linear vibrating screen was 6 m / min. Black powder and aluminum foil were separated. The recovery rate of the black powder was 94.3%, and the purity of the black powder was 98.2%.

[0028] As can be seen from Examples 1-3, the recycling method of the battery of the present invention can achieve a final black powder recovery rate of over 98.7% and a black powder purity of over 99.2%. Comparing Example 3 with Comparative Example 1 and Comparative Example 2, it can be seen that when other conditions remain unchanged, if the positive electrode is not treated with supercritical CO2 or coated with an organic intercalation solvent before electron beam irradiation, the final black powder recovery rate and purity will decrease significantly.

Claims

1. A method for recycling batteries, characterized in that: Includes the following steps: (1) Discharge the waste lithium battery and disassemble it to obtain the positive electrode sheet. Clean the positive electrode sheet and dry it. (2) Coating the surface of the dried positive electrode with an organic intercalation solvent; (3) Place the treated positive electrode in a sealed container, introduce CO2 into the sealed container and raise the temperature and pressure in the sealed container to make CO2 become supercritical, and then use supercritical CO2 to perform intercalation treatment on the surface of the positive electrode under heat preservation and pressure preservation. (4) Depressurize the sealed container to reduce the pressure inside to atmospheric pressure; (5) After removing the positive electrode from the sealed container, perform electron beam irradiation; (6) Vibrate and peel off the material after electron beam irradiation to obtain black powder.

2. The battery recycling method according to claim 1, characterized in that: In step (1), the cleaning is performed by placing the positive electrode sheet in an organic solvent.

3. The battery recycling method according to claim 1, characterized in that: In step (2), the organic intercalation solvent is a mixture of benzyl alcohol, ethylene glycol butyl ether and dipropylene glycol methyl ether in a weight ratio of (3-5):(3-5):(2-4).

4. The battery recycling method according to claim 1, characterized in that: In step (3), the temperature after the increase is 32-50℃ and the pressure after the increase is 7.5-10MPa.

5. The battery recycling method according to claim 1, characterized in that: In step (3), the heat preservation and pressure preservation time is 30-90 minutes.

6. A battery recycling method according to claim 1, characterized in that: In step (3), the intercalation process is accompanied by stirring at a rate of 50-100 r / min.

7. The battery recycling method according to claim 1, characterized in that: In step (4), the time taken for depressurization is 1-5 seconds.

8. A battery recycling method according to claim 1, characterized in that: In step (5), after the positive electrode is taken out, it is laid flat on the conveyor belt and then irradiated with an electron beam. The thickness of the material after being laid flat is 0.5-2cm, and the conveying speed of the conveyor belt is 5-10m / min.

9. A battery recycling method according to claim 1, characterized in that: In step (5), the electron beam irradiation parameters are: the electron beam irradiation energy is 1-5 MeV, the electron beam current is 1-10 mA, and the electron beam dose in the irradiated area is 100-300 kGy.

10. A battery recycling method according to claim 1, characterized in that: In step (6), the vibration stripping is carried out using a linear vibrating screen with a vibration frequency of 30-100Hz, a mesh size of 20-80 mesh, and a material conveying speed of 5-10m / min on the linear vibrating screen.