System and method for recycling valuable metal of lithium ion battery through cooperation of wet grinding and vacuum pyrolysis

Abstract

The invention discloses a system and a method for recycling valuable metals of a lithium ion battery through cooperation of wet grinding and vacuum pyrolysis. The recycling method comprises the following steps: completely discharging a waste lithium ion battery, disassembling and separating a positive plate and a negative plate, crushing and sieving, and collecting undersize powder; mixing with a grinding medium, and carrying out ball milling by adopting a ball milling tank; the slurry is sieved after being dried, and screen underflow is collected and is electrode black powder; putting the electrode black powder into a vacuum pyrolysis reactor, vacuumizing and then pyrolyzing; and after the pyrolysis is finished, cooling to room temperature under vacuum or inert gas protection to obtain a valuable metal solid product. The method is carried out at a relatively low temperature, metal oxidation can be inhibited, generation of harmful gas is reduced, separation and pyrolysis with higher adaptability to raw materials are realized, and directional recovery is realized.

Description

A system and method for the synergistic recovery of valuable metals from lithium-ion batteries using wet grinding and vacuum pyrolysis. Technical Field

[0001] This invention belongs to the field of valuable metal recycling technology, specifically relating to a system and method for the synergistic recovery of valuable metals from lithium-ion batteries using wet grinding and vacuum pyrolysis. Background Technology

[0002] With the widespread adoption of electric vehicles and portable electronic devices, the consumption of lithium-ion batteries (LIBs) has increased dramatically, resulting in a large number of waste batteries and posing serious challenges to resource recycling and the environment. The cobalt, lithium, and other metals contained in cathode materials (such as LiCoO2) have extremely high economic value, and their efficient recycling is of great significance for ensuring the supply of strategic resources and reducing environmental pollution.

[0003] Industrial recovery of valuable metals from waste LIBs typically involves three main stages: pretreatment, metal extraction, and product purification. The pretreatment stage aims to efficiently and selectively dissociate and enrich the electrode active material from the current collector (aluminum / copper foil), and its effectiveness directly determines the complexity, cost, and overall efficiency of subsequent metallurgical processes.

[0004] Currently, mainstream pretreatment technologies mainly include two types of methods: mechanical separation and thermal treatment. However, both have significant technical bottlenecks. Mechanical methods, represented by dry ball milling, achieve dissociation through physical means such as crushing and sieving, but they have the following drawbacks: Due to the lack of media lubrication and cooling, intense impact friction leads to excessive breakage of aluminum and copper foils, resulting in a large amount of metal fragments mixed with active materials. The binder (such as PVDF) is firmly bonded, causing a large amount of active material to exist as an aggregate of active material, binder, and metal fragments, resulting in incomplete dissociation. The particle size distribution is not ideal, with the products mostly being large aggregates (38-850 μm), much larger than the primary particles of the active material (1-10 μm). This significantly reduces the subsequent leaching reaction rate, leading to a decrease in metal recovery. The separation process generates a large amount of dust containing metal and carbon, posing a health risk from inhalation and an explosion hazard. Material loss and environmental pollution are also significant problems. A large amount of mechanical energy is converted into heat energy, causing the system temperature to rise. This may cause the binder to melt and re-encapsulate the particles or the organic matter to decompose, thus hindering dissociation and generating harmful gases.

[0005] While the widely used inert atmosphere (such as N2) pyrolysis technology can decompose organic matter, it has inherent drawbacks: To achieve complete decomposition of binders and reduction of oxides, extremely high temperatures (>800 ℃ or even 1000 ℃) are typically required, resulting in enormous energy consumption. In the presence of trace amounts of oxygen or oxygen-containing atmospheres generated by pyrolysis, high temperatures easily oxidize copper current collectors to CuO / Cu2O, potentially leading to complex cobalt oxide phases. This not only causes metal loss but also increases subsequent acid consumption during leaching and the difficulty of solution purification. Pyrolysis produces complex, toxic, and corrosive gases containing HF (from incompletely separated PVDF), phosphorus oxides (from LiPF6), and various organic compounds, necessitating expensive and efficient gas purification systems, increasing costs and operational complexity. The high temperatures and corrosive gases place extremely high demands on reactor materials (such as high-nickel alloys), driving up equipment investment and maintenance costs. If initial mechanical dissociation is insufficient, large particles are prone to incomplete reactions due to insufficient heat and mass transfer during pyrolysis.

[0006] In summary, existing dry mechanical separation and inert atmosphere pyrolysis technologies suffer from a series of interconnected drawbacks, including low dissociation efficiency, poor selectivity, high energy consumption, easy oxidation of metals, severe environmental pollution, demanding equipment requirements, and poor adaptability to raw materials. These drawbacks result in a complex, costly, and environmentally unfriendly recycling process, severely hindering the development of the waste lithium-ion battery resource utilization industry. Therefore, there is an urgent need to develop a new method and system that can achieve efficient, clean, and low-energy pretreatment under relatively mild conditions to overcome the current technological bottlenecks. Summary of the Invention

[0007] To address at least one of the aforementioned problems, this invention provides a system and method for the synergistic recovery of valuable metals from lithium-ion batteries through wet grinding and vacuum pyrolysis. This system and method are carried out at relatively low temperatures, can suppress metal oxidation, reduce the generation of harmful gases, and are more adaptable to raw materials, thereby achieving targeted recovery.

[0008] To achieve the above objectives, the present invention employs the following technical means: The first aspect of the present invention provides a method for the co-processed recovery of valuable metals from lithium-ion batteries using wet grinding and vacuum pyrolysis, comprising the following steps: S1, the recovered waste lithium-ion batteries are fully discharged, and the positive and negative electrode sheets are disassembled and separated; S2, the positive and negative electrode sheets are crushed, passed through a 350-400 μm coarse sieve, and the sieve-underfill powder is collected; S3, the sieve-underfill powder is mixed with grinding media at a solid-liquid ratio of 1:(3-4), and ball-milled using a ball mill jar; S4, the ball-milled slurry is dried, passed through a 35-40 μm fine sieve, and the sieve-underfill material is collected as electrode black powder; S5, the electrode black powder is placed in a vacuum pyrolysis reactor, and after evacuation, the temperature of the reaction chamber is raised from room temperature to a pyrolysis temperature of 600-700 °C at a certain heating rate, and maintained for 50-60 min for pyrolysis; S6, after pyrolysis, the mixture is cooled to room temperature under vacuum or inert gas protection to obtain a valuable metal solid product.

[0009] In some embodiments of the present invention, the grinding medium is water.

[0010] In some embodiments of the present invention, in step S1, the method for discharging the waste lithium-ion battery is to place the battery in an 8-10 wt.% sodium chloride solution for discharge for no less than 6 hours, until the voltage across the battery terminals drops below 0.3 V. Preferably, the battery is placed in a 10 wt.% sodium chloride solution for discharge.

[0011] In some embodiments of the present invention, in step S3, the ball milling speed of the milling jar is 300-350 rpm; the ball milling time is 80-90 min. Preferably, the ball milling speed is 350 rpm; the ball milling time is 90 min.

[0012] In some embodiments of the present invention, in step S3, the grinding balls in the grinding jar are mixed grinding balls with a diameter of 5-10 mm, and the mass ratio of material to grinding balls is 1:(8-10). Preferably, the mass ratio of material to grinding balls is 1:10.

[0013] In some embodiments of the present invention, in step S5, the heating rate of the vacuum pyrolysis reactor is 5-15°C / min. Preferably, the heating rate of the vacuum pyrolysis reactor is 10°C / min.

[0014] In some embodiments of the present invention, in step S5, the target pyrolysis temperature of the vacuum pyrolysis reactor is 650 °C.

[0015] In some embodiments of the present invention, in step S5, the gaseous products generated by pyrolysis are extracted by a vacuum pump, pass through a condenser trap to capture condensable gases, and obtain an oily substance; the non-condensable gases are introduced into an alkaline absorption tower for neutralization and purification, and are discharged after meeting the standards.

[0016] In some embodiments of the present invention, in step S6, the valuable metal solid product is a mixture of Li2CO3, Co3O4 and metallic Co.

[0017] The Li2CO3 in the mixture can be recovered by direct water leaching, while the Co3O4 / Co mixture can be recovered by simple acid leaching or more environmentally friendly reduction leaching.

[0018] A second aspect of the present invention provides a system for the synergistic recovery of valuable metals from lithium-ion batteries through wet grinding and vacuum pyrolysis, comprising a wet grinding pretreatment unit and a vacuum pyrolysis unit. The wet grinding pretreatment unit includes a crusher; the crusher outlet is connected to the inlet of a coarse screening device; the undersize outlet of the coarse screening device is connected to the inlet of a ball mill, and the ball mill is also connected to a deionized water source and a grinding media addition port; the ball mill outlet is connected to a drying device, and the drying device outlet is connected to a fine screening device; the vacuum pyrolysis unit includes a vacuum pyrolysis furnace, a vacuum pump connected to the gas outlet of the vacuum pyrolysis furnace, a condenser located between the gas outlet of the vacuum pyrolysis furnace and a tail gas absorption device, and the tail gas absorption device connected to the condenser; the wet grinding pretreatment unit is connected to the vacuum pyrolysis unit via a closed screw conveyor and a vacuum feeder; the wet grinding pretreatment unit, the vacuum pyrolysis unit, and the closed screw conveyor are communicatively connected to a central control system.

[0019] Furthermore, the system also includes a thermal energy integration system, which includes a heat exchanger located before the exhaust gas absorption device and connected to the high-temperature exhaust gas from the vacuum pyrolysis furnace and the air inlet duct of the dryer.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This application employs wet dissociation, which improves dissociation efficiency and selectivity. Water, as the grinding medium, acts as a wedge, penetrating particle fissures and bonding interfaces, significantly reducing the bonding force between LiCoO2 and aluminum foil. Under the synergistic effect of mechanical force, a qualitative change from crushing to dissociation is achieved. In the final product, the recovery rate of LiCoO2 in the fine particle size (-38 μm) is significantly increased from about 30% with dry grinding to over 41%, with extremely high purity. Wet dissociation optimizes the particle size distribution; wet grinding effectively prevents over-grinding and agglomeration of particles, resulting in active material particles closer to their original primary particle size (D50 < 14 μm). This ultrafine, uniform particle size distribution greatly increases the specific surface area of ​​subsequent pyrolysis or leaching reactions, accelerates reaction kinetics, and is expected to shorten the process flow and time of subsequent processes, further improving the metal recovery rate.

[0021] This invention significantly reduces the reaction temperature, resulting in substantial energy savings and reduced consumption. The pyrolysis temperature is lowered from over 900 °C in traditional methods to 650 °C, a reduction of over 250 °C. According to the Arrhenius equation, this significant reduction in reaction temperature translates to an exponential decrease in energy consumption, significantly reducing operating costs and improving the process's economics. Vacuum pyrolysis effectively inhibits current collector oxidation, simplifying subsequent processes. The vacuum environment fundamentally eliminates oxygen, completely avoiding the oxidation problems of copper and aluminum foils. The pyrolysis products do not contain CuO / Cu2O, which reduces acid consumption in subsequent leaching processes, resulting in a purer leachate and greatly simplifying solution purification and separation steps.

[0022] In this invention, wet milling provides pure and fine ideal raw materials for vacuum pyrolysis, making low-temperature pyrolysis possible. Vacuum pyrolysis is carried out at low temperatures, avoiding the damage to the excellent properties of wet-milled products caused by high temperatures. The deep coupling of these two processes minimizes overall energy consumption and maximizes recovery efficiency. Through a thermal energy integration system, waste heat from pyrolysis is used for material drying, significantly reducing the system's external energy input; overall energy consumption is reduced by more than 20% compared to operating the two units independently. From material input to product output, the entire process is a closed-loop operation, with no dust or harmful gas leakage, achieving clean production. Automated conveying reduces human intervention and the risk of pollution. System-level control ensures the stability and optimization of operating parameters for each unit, thereby guaranteeing a high recovery rate (>98%) and high purity of the final product. The integrated design reduces equipment spacing and auxiliary facilities, lowering land and investment costs. The high-efficiency, low-energy, and high-value product output makes the entire recycling process highly economically competitive.

[0023] The product of this invention has a relatively simple composition, which facilitates targeted recovery. Under optimized temperature and time, the vacuum pyrolysis product mainly consists of Li2CO3, Co3O4, and Co, with a relatively simple and well-defined phase composition. Li2CO3 can be directly recovered by water leaching, while the Co3O4 / Co mixture can be recovered through simple acid leaching or a more environmentally friendly reductive leaching process, resulting in a clear process flow. Attached Figure Description

[0024] Figure 1 shows a schematic diagram of the lithium-ion battery valuable metal recycling system of the present invention; Figure 2 shows an SEM image of the product in Example 7 of the present invention, wherein the left is the untreated product and the right is the product after wet milling for 90 minutes. Detailed Implementation

[0025] The following examples are used to illustrate preferred embodiments of the invention. Those skilled in the art will understand that the techniques disclosed in the examples represent techniques discovered by the inventors that can be used to implement the invention, and therefore can be considered preferred embodiments for implementing the invention. However, those skilled in the art should understand from this specification that many modifications can be made to the specific embodiments disclosed herein, still yielding the same or similar results, without departing from the spirit or scope of the invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials disclosed herein and cited therein are incorporated herein by reference. Many equivalent techniques of specific embodiments of the invention described herein will be recognized or can be understood by ordinary experimentation by those skilled in the art. These equivalents will be included in the claims.

[0027] The technical solution of this application will be further described in detail below with reference to specific embodiments.

[0028] Example 1: A lithium-ion battery valuable metal recovery system includes a wet grinding pretreatment unit and a vacuum pyrolysis unit. The wet grinding pretreatment unit includes a crusher; the crusher outlet is connected to the inlet of a vibrating screen (850 μm vibrating screen); the undersize outlet of the vibrating screen is connected to the inlet of a planetary ball mill, which is also connected to a deionized water source and a grinding bead addition port; the planetary ball mill outlet is connected to a drying chamber, and the drying chamber outlet is connected to a vibrating screen (38 μm vibrating screen); its function is to receive the disassembled electrode sheets and produce high-purity, fine-grained black powder.

[0029] The vacuum pyrolysis unit includes a vacuum pyrolysis furnace, a vacuum pump connected to the gas outlet of the vacuum pyrolysis furnace, a condenser located between the gas outlet of the vacuum pyrolysis furnace and the tail gas absorption device, and the tail gas absorption device connected to the condenser; its function is to decompose the organic matter in the black powder and realize the conversion of metal compounds.

[0030] The wet milling pretreatment unit is connected to the vacuum pyrolysis unit via a closed screw conveyor and a vacuum feeder; the dried black powder produced by the wet milling unit is automatically and in a closed manner transported to the feed port of the vacuum pyrolysis furnace.

[0031] The wet milling pretreatment unit, vacuum pyrolysis unit, and closed screw conveyor are connected to the central control system. The central control system adopts a PLC or DCS system, which integrates the electrical parameters of each unit (such as ball mill speed, pyrolysis furnace temperature, vacuum degree), material parameters (such as conveying volume), and product quality feedback signals (such as online particle size analyzer and gas composition analyzer) to achieve the linkage, optimization, and stable control of the entire system.

[0032] The system also includes a thermal energy integration system, which comprises a heat exchanger located before the exhaust gas absorption device. The heat exchanger connects the high-temperature exhaust gas from the vacuum pyrolysis furnace to the air inlet duct of the dryer. The high-temperature exhaust gas generated by the vacuum pyrolysis furnace transfers its heat to the air flowing into the drying chamber through the heat exchanger, providing a heat source for drying the material after wet grinding and achieving cascaded energy utilization.

[0033] Example 2: Twenty discarded Apple iPhone 6 lithium batteries (model: 616-0671), with a total weight of approximately 530 g, were collected. First, the batteries were placed in a 10 wt.% NaCl solution (5 L) for complete discharge for 36 hours. After discharge, the batteries were manually disassembled using insulated pliers and scissors, separating the plastic casing, positive electrode, negative electrode, and separator. The positive and negative electrode plates (not separated initially) were cut into small pieces of approximately 1.5 cm × 1.5 cm, totaling approximately 408 g.

[0034] A FRITSCH Pulverisette 19 rotary cutting crusher, equipped with a 2 mm aperture screen, was used for initial crushing of small electrode pieces for 5 minutes. The crushed material was then sieved through an 850 μm standard vibrating screen for 5 minutes. The oversize material (mainly Al and Cu foil) weighed 125 g and was collected for later use. The undersize material (electrode material powder) weighed 278 g.

[0035] Take 100 g of the sieved material and mix it with 300 g of deionized water in a beaker, stirring to form a slurry. Transfer the slurry to the zirconia grinding jar (500 ml volume) of a Changsha Tianchuang QXQM-2L planetary ball mill, and add 5 mm and 10 mm zirconia grinding balls (total mass ratio of material: grinding balls = 1:8). Set the ball mill's revolution speed to 350 rpm and its rotation speed to 700 rpm, and run for 90 minutes. After wet milling, pour the slurry into a crystallizing dish and place it in a DHG-9070A electric heating forced-air drying oven, drying at 60 °C for 5 hours until constant weight.

[0036] The dried powder became extremely loose. The dried powder was finely sieved using a Φ200 mm standard test sieve (38 μm mesh size) and an ultrasonic vibrating sieve separator (USK-206S) for 15 minutes. After sieving, the oversize (+38 μm) was accurately weighed at 58.2 g, and the undersize (-38 μm) at 38.5 g. Calculations showed that the yield of the target product (-38 μm black powder) was 38.5% (relative to the initial 100 g undersize electrode powder), with a Co content of 65.8%.

[0037] The obtained undersize product was characterized: Laser particle size analysis (Malvern Mastersizer 3000) showed that the volume average particle size D was 11.7 μm, Dv(50) was 9.8 μm, and Dv(90) was 16.2 μm. More than 92% of the particles were distributed between 5 and 18 μm. This allows the ball-milled dried powder to be separated into particles by a 38.5 μm sieve before vacuum pyrolysis. Larger particles will remain on the sieve, mainly containing impurities such as aluminum and copper foil fragments. This separation avoids contamination.

[0038] SEM-EDS analysis (Zeiss Sigma 300) showed that the particles were irregularly flaky and porous, with no obvious large metal foil pieces attached. EDS surface scanning analysis (selecting at least 5 different fields of view) showed that the average weight percentage of Co was 65.8±2.1%, Al was 6.5±0.8%, Cu was 5.2±0.6%, and F was below the detection limit (<0.5%).

[0039] XRD analysis (Bruker D8 Advance): The main phases are LiCoO2 and graphite (C). No obvious diffraction peaks of Al or Cu were detected, which is consistent with the EDS results, indicating that the metal impurities mainly exist in the form of extremely fine physical mixtures rather than chemical bonds.

[0040] Example 3 follows the same steps as Example 1, except that wet grinding is not performed; the material after preliminary crushing and screening is directly screened (-38 μm).

[0041] Results: The yield of the -38 μm product was only 9.1%, and the Co content was only 41.2%.

[0042] The product obtained without wet milling in Example 3 and the product obtained after wet milling at 350 rpm for 90 min in Example 2 were analyzed by SEM, as shown in Figure 2.

[0043] SEM images show that after 90 minutes of wet milling, the reduction in particle size and the difference in particle shape are more significant.

[0044] The steps in Example 4 are the same as in Example 1, except that the wet grinding speed is 200 rpm and the time is 90 min.

[0045] Results: The yield of the -38 μm product was 22.4%, and the Co content was 58.3%.

[0046] The steps in Example 5 are the same as in Example 1, except that the wet milling speed is 500 rpm and the time is 90 min.

[0047] Results: The yield of the -38 μm product was 40.1%, but the Co content decreased slightly to 62.5%, and the energy consumption increased significantly.

[0048] The steps in Example 6 are the same as in Example 1, except that the wet grinding speed is 350 rpm and the time is 30 min.

[0049] Results: The yield of the -38 μm product was 18.7%, and the Co content was 55.1%.

[0050] The steps in Example 7 are the same as in Example 1, except that the solid-liquid ratio in wet milling is 1:1.

[0051] Results: The slurry was too thick, resulting in low grinding efficiency, a yield of 25.6%, and a Co content of 59.8%.

[0052] The results of Examples 2-7 above demonstrate that the parameters selected in this invention—350 rpm, 90 min, and a solid-liquid ratio of 1:3—are optimal in terms of yield and product purity.

[0053] In Example 8, 50.0 g of the prepared -38 μm black powder (Co: 65.8%) was accurately weighed and evenly spread in a corundum crucible (99% Al2O3), with a layer thickness of approximately 5 mm. The crucible was placed in a self-built vacuum tube pyrolysis furnace. The furnace body was made of 310S stainless steel, with an inner diameter of 100 mm and an effective heating zone length of 600 mm. Both ends were sealed with water-cooled flanges and silicone sealing rings. The furnace body was connected to a rotary vane mechanical vacuum pump (ultimate vacuum 0.1 Pa) and a vortex dry pump (for high vacuum evacuation). The vacuum level was measured by a resistance vacuum gauge and an ionization vacuum gauge, respectively.

[0054] After closing the furnace door, activate the vacuum system to evacuate the furnace and stabilize the pressure at 0.8 kPa (absolute pressure). Start the programmed temperature control system, raising the temperature from room temperature to 650 °C at a rate of 10 °C / min. Once at 650 °C, maintain this temperature for 60 minutes. Throughout the heating and holding process, the vacuum pump operates continuously to maintain a dynamic vacuum in the system. The gases produced by pyrolysis first pass through a cold trap (-196 °C) cooled with liquid nitrogen at the furnace outlet, where volatile organic compounds (VOCs) and moisture are condensed and collected. Then, the non-condensable gases are passed through two series-connected bubbling absorption flasks containing a 2 mol / L NaOH solution to absorb acidic gases (such as HF, CO2, and P2O5 hydrolysis products).

[0055] After pyrolysis, the furnace was cooled at a rate of 5 °C / min to below 200 °C, then heating was stopped, and the furnace was allowed to cool naturally to room temperature. A vacuum was maintained throughout the process until the temperature dropped below 100 °C. After the vacuum was broken, the crucible was removed, and the mass of the solid product was measured to be 41.5 g, with a mass loss rate of 17.0%.

[0056] XRD diffraction patterns showed that the product mainly consisted of three crystalline phases: Li₂CO₃, Co₃O₄, and metallic Co. Semi-quantitative analysis using Rietveld refinement revealed the following weight percentages: Li₂CO₃: 38.2%, Co₃O₄: 45.1%, and Co: 16.7%. No diffraction peaks were detected for CuO, Cu₂O, or Al.

[0057] SEM-EDS analysis: The product exhibits a loose and porous aggregate morphology. EDS point analysis and area scanning showed that Co and O elements were uniformly distributed, corresponding to the distribution of Co3O4 and Co; the distribution of C and O elements corresponded to Li2CO3; the signal intensity of Al, Cu, and F elements was extremely weak, and their contents were all less than 1 wt.%.

[0058] The steps in Example 9 are the same as in Example 8, except that the pyrolysis temperature is 550 °C.

[0059] XRD analysis showed that the product still contained a large amount of unreacted LiCoO2 and graphite, with very weak diffraction peaks for Co3O4 and Li2CO3, and no detectable metallic Co. The reaction was incomplete.

[0060] The steps in Example 10 are the same as in Example 8, except that the pyrolysis temperature is 750 °C.

[0061] XRD analysis showed a significant enhancement in the diffraction peaks of metallic Co, a weakening of the Co3O4 peak, and no change in the Li2CO3 peak. This indicates that increased temperature promotes further reduction of Co3O4 to Co. However, this increases energy consumption and places higher demands on the long-term temperature resistance of the equipment.

[0062] Considering the results of Examples 8-10, the reaction integrity, product controllability, and energy consumption, 650 °C is the optimal temperature.

[0063] Comparative Example 1: Take the same 50.0 g of black powder, pass high-purity N2 through a tube furnace at a flow rate of 200 ml / min, and pyrolyze it at 900 °C for 30 min.

[0064] XRD results showed that the products were Li₂CO₃, CoO, and a small amount of Cu₂O. The presence of Cu₂O indicates that oxidation occurred.

[0065] Obvious sintering was observed on the inner wall of the crucible and the surface of the material, with the particles becoming larger.

[0066] Energy consumption calculations show that the amount of electricity required to reach and maintain 900 °C is 2.8 times that required for vacuum pyrolysis at 650 °C.

[0067] Compared with the traditional N2-high temperature pyrolysis method, the present invention has a lower pyrolysis temperature, no oxidation, and is more energy-efficient.

[0068] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by this application.

Claims

1. A method for the synergistic recovery of valuable metals from lithium-ion batteries using wet grinding and vacuum pyrolysis, characterized in that, The process includes the following steps: S1. Completely discharge the recycled waste lithium-ion batteries and disassemble them to separate the positive and negative electrode sheets; S2. Crush the positive and negative electrode sheets, pass them through a 350-400 μm coarse sieve, and collect the sieve powder; S3. Mix the sieve powder with grinding media at a solid-liquid ratio of 1:(3-4) and ball mill them in a ball mill jar; S4. Dry the ball-milled slurry, pass it through a 35-40 μm fine sieve, and collect the sieve material as electrode black powder; S5. Place the electrode black powder in a vacuum pyrolysis reactor, evacuate the reactor, and raise the temperature of the reaction chamber from room temperature to a pyrolysis temperature of 600-700 ℃ at a certain heating rate, and maintain the temperature for 50-60 min for pyrolysis; S6. After pyrolysis, cool the mixture to room temperature under vacuum or inert gas protection to obtain a valuable metal solid product.

2. The method for wet milling-vacuum pyrolysis co-processing of valuable metals from lithium-ion batteries according to claim 1, characterized in that, In step S1, the method for discharging waste lithium-ion batteries is to place the batteries in an 8-10 wt.% sodium chloride solution for discharge for no less than 6 hours until the voltage at both ends of the battery drops below 0.3 V.

3. The method for wet milling-vacuum pyrolysis synergistic recovery of valuable metals from lithium-ion batteries according to claim 1, characterized in that, In step S3, the ball milling speed of the ball mill jar is 300-350 rpm; the ball milling time is 80-90 min.

4. The method for wet milling-vacuum pyrolysis co-processing recovery of valuable metals from lithium-ion batteries according to claim 3, characterized in that, In step S3, the grinding balls in the grinding jar are mixed grinding balls with a diameter of 5-10 mm, and the mass ratio of material to grinding balls is 1:(8-10).

5. The method for wet milling-vacuum pyrolysis co-processing of valuable metals from lithium-ion batteries according to claim 1, characterized in that, In step S5, the heating rate of the vacuum pyrolysis reactor is 5-15 °C / min.

6. The method for wet milling-vacuum pyrolysis co-processing of valuable metals from lithium-ion batteries according to claim 1, characterized in that, In step S5, the target pyrolysis temperature of the vacuum pyrolysis reactor is 650 °C.

7. The method for wet milling-vacuum pyrolysis co-processing of valuable metals from lithium-ion batteries according to claim 1, characterized in that, In step S5, the gaseous products generated by pyrolysis are extracted by a vacuum pump, pass through a condenser trap to capture condensable gases, and obtain an oily substance; the non-condensable gases are introduced into an alkaline absorption tower for neutralization and purification, and are discharged after meeting the standards.

8. The method for wet milling-vacuum pyrolysis co-processing of valuable metals from lithium-ion batteries according to claim 1, characterized in that, In step S6, the valuable metal solid product is a mixture of Li2CO3, Co3O4 and metallic Co.

9. A system for the synergistic recovery of valuable metals from lithium-ion batteries through wet grinding and vacuum pyrolysis, characterized in that, The system includes a wet grinding pretreatment unit and a vacuum pyrolysis unit. The wet grinding pretreatment unit includes a crusher; the crusher outlet is connected to the inlet of a coarse screening device; the undersize outlet of the coarse screening device is connected to the inlet of a ball mill, which is also connected to a deionized water source and a grinding media addition port; the ball mill outlet is connected to a drying device, and the drying device outlet is connected to a fine screening device. The vacuum pyrolysis unit includes a vacuum pyrolysis furnace, a vacuum pump connected to the gas outlet of the vacuum pyrolysis furnace, a condenser located between the gas outlet of the vacuum pyrolysis furnace and a tail gas absorption device, and the tail gas absorption device connected to the condenser. The wet grinding pretreatment unit is connected to the vacuum pyrolysis unit via a closed screw conveyor and a vacuum feeder. The wet grinding pretreatment unit, the vacuum pyrolysis unit, and the closed screw conveyor are communicatively connected to a central control system.

10. A system for the synergistic recovery of valuable metals from lithium-ion batteries via wet grinding and vacuum pyrolysis according to claim 9, characterized in that, The system also includes a thermal energy integration system, which includes a heat exchanger located before the exhaust gas absorption device and connected to the high-temperature exhaust gas from the vacuum pyrolysis furnace and the air inlet duct of the dryer.

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