Universal Lithium-ion Battery Recycling

Waste lithium-ion battery recycle such as NMC (nickel-manganese-cobalt) lithium battery packs and LFP (lithium iron phosphate) battery packs are processed through battery pre-treatment lines to obtain electrode powder. The NMC battery electrode powder and waste materials are further processed through acid leaching and solvent extraction lines to extract metals such as nickel, cobalt, and manganese, while the LFP battery electrode powder and waste materials are processed through acid leaching lines to extract lithium.

1. Disassembly process of waste lithium battery pack

1 battery pack disassembly workshop, used for performance testing and disassembly of waste lithium battery packs in the whole plant. The specific production process of waste lithium battery pack disassembly is as follows:

1.1. Incoming inspection & segregated storage

The waste lithium battery packs in the plant are first tested. For the damaged waste lithium batteries with deformation, cracks, burns, bulges, leakage, etc., they are stored separately in the damaged battery storage warehouse in special containers to avoid the environmental risks caused by the spontaneous combustion of waste lithium batteries. A damaged battery storage warehouse with an area of 100m² is set up in the discharge workshop. The main pollutants in the waste gas generated are volatile organic compounds; a micro-negative pressure gas collection system with an air volume of 5000m³/h is set up in the damaged battery storage warehouse. The collected waste gas and the discharge waste gas are treated by "two-stage alkali spray" and then discharged through a 20m high exhaust pipe.

All the used lithium battery packs that have been inspected completely upon entering the plant are stored in the battery warehouse. Used lithium iron phosphate battery packs and used ternary lithium battery packs are stored in separate areas away from light, and the ambient temperature of the storage area is controlled to avoid environmental risks caused by high-temperature spontaneous combustion. The ground of each storage area is hardened, impermeable and anti-corrosion designed, with side ditch collection systems set up around it, and each is equipped with a 5m3 liquid collection tank, pump and spare empty barrels.

1.2. Battery pack disassembly

The waste lithium battery packs are transported from the battery warehouse to the battery pack disassembly workshop by forklifts for residual energy detection and unpacking. The waste lithium battery packs are lifted by special lifting equipment to the disassembly tooling platform, and the battery packs are disassembled by the manipulator and pneumatic disassembly tools on the disassembly tooling platform to obtain iron shells, aluminum shells and brackets, copper bars and wiring harnesses, BMS systems, battery modules, etc. The battery modules are further disassembled after residual energy detection, and other disassembly products are sold to material recycling companies as general solid waste.

1.3. Battery module residual energy detection and disassembly

The disassembled battery modules are tested for residual energy. When the voltage and capacity reach 60% of the design value, they are directly collected and stored, and regularly sold to recycling companies. Unusable battery modules are further dismantled on the disassembly tooling platform to obtain single cells, soft packs, connecting pieces and wires. The single cells are tested for residual energy in the next step, and other disassembly products are sold to material recycling companies as general solid waste.

The dismantling products obtained after the dismantling process of the waste lithium battery pack are divided into iron parts, aluminum parts, copper parts, BMS system, plastic and single battery. Among them, the iron parts are mainly iron shells and soft packs; the aluminum parts are mainly brackets and connecting pieces; the copper parts are mainly removed copper bars, wiring harnesses and wires; the plastics are mainly diaphragms.

1.4. Single battery remaining energy detection

According to the national policy of "establishing a traceability mechanism for power battery products with traceable sources, traceable destinations, and controllable nodes" during the recycling of power batteries, the single battery is tested for residual energy and a special national network information platform is used to implement the registration of various traceable information of power batteries. That is, the manufacturer, battery type, production date and other information can be obtained through the coding of waste single batteries.

When the voltage and capacity of a single battery reaches 65% of the design value, it will be directly collected and stored, and regularly sold to recycling companies. Single batteries that cannot be recycled will enter the discharge workshop.

2. Single battery crushing process

There are 1 discharge workshop and 1 pretreatment workshop. There are 3 single cell crushing production lines in the pretreatment workshop. The production process of each single cell crushing production line for lithium-ion battery recycle is exactly the same, as follows:

2.1. Chemical discharge

The disassembled battery cells are discharged physically and chemically. Physical discharge is carried out in a discharge cabinet, which does not produce pollutants. Chemical discharge uses a discharge cell for immersion discharge, which will produce discharge waste gas. At the same time, a damaged battery storage warehouse with an area of 100m² is set up in the discharge workshop. The collected broken batteries are directly stored in the damaged battery storage warehouse after entering the site, and chemical discharge is given priority.

The battery cells are transported to the belt conveyor of the discharge workshop through the hopper and forklift. A 50m3 discharge battery is set up in the discharge workshop for chemical discharge, and the discharge battery contains a saturated sodium sulfate solution. After the battery cells are soaked in the discharge battery for 2-3 hours, they are grabbed by the grab bucket and placed in the cleaning tank for surface cleaning, and then dried by the high-pressure air dryer, placed on the belt conveyor and dropped into the hopper. The reaction equation of the discharge process is as follows:

Anode reaction formula: 4OH--4e=2H₂O+O₂↑;

Cathode reaction formula: 4H++4e=2H₂↑

The main pollutant in the exhaust gas generated during the battery discharge process is H2; the proposed project will set up a gas collection system with an air volume of 5000m3/h and a gas collection efficiency of 95% on one side of the discharge battery. The collected discharge exhaust gas will be treated by "two-stage alkali solution spraying" and then discharged through a 20m high exhaust cylinder; the discharge slag generated in the discharge tank will be regularly salvaged and safely disposed of as hazardous waste; the discharge wastewater will be reused after being treated by the sodium sulfate wastewater treatment system and will not be discharged.

2.2. Broken

The discharged single battery is transported to the crushing production line in the processing workshop through the feeding hopper and forklift. The single battery is automatically fed through oxygen-free feeders, electronic weighing scales, battery feeding belt conveyors and other equipment. The feeding system is interlocked with the crushing system to select the appropriate feeding speed to ensure that the battery monomer is fully crushed and dissociated. The entire crushing process is carried out in a closed dry crusher, and the crushed material is pneumatically transported to the pyrolysis furnace through a closed pipeline.

The battery cells are fed into an oxygen-free feeder that is isolated from air by a feeding belt, and then fed into a closed gas-protected crusher by the oxygen-free feeder for crushing under a nitrogen protective atmosphere. The crusher cutter instantly shears the material to separate the diaphragm, positive and negative plates, and shell of the battery cells. The particle size of the crushed product is ≤40mm, and the temperature of the crushed product is ≤45℃.

The waste gas generated by crushing is first treated by a bag filter, and then enters the "high-temperature incineration + SNCR denitrification + rapid cooling + activated carbon injection adsorption + bag filter + two-stage alkali solution spraying" treatment before being discharged through a 35m high exhaust pipe.

2.3. High temperature oxygen-free pyrolysis

The crushed materials are mainly composed of the following substances: electrolyte, crushed diaphragm paper (plastic), positive and negative electrode powder, iron foil, aluminum foil, copper foil, and organic substances such as PVDF, the powder binder. The crushed materials are sent to the closed pyrolysis furnace through a closed conveying system, and nitrogen is introduced into the pyrolysis furnace to protect it from oxidation of the electrolyte. A high-temperature oxygen-free pyrolysis furnace is used to indirectly heat the materials with natural gas as energy, and volatile organic substances such as electrolyte and PVDF are removed through pyrolysis technology.

First, the material is heat treated at 450°C to 550°C for 1h to 3h, and the high-boiling point electrolyte organic matter and the binder polyvinylidene fluoride (PVDF) are thermally decomposed in a non-oxidizing atmosphere to produce organic matter, HF and CO₂.

During high-temperature oxygen-free pyrolysis, all volatile organic matter in the electrolyte of the battery cell is converted into gaseous state, and the electrolyte lithium hexafluorophosphate (LiPF6) is completely decomposed into gaseous PF5 (phosphorus pentafluoride). The reaction formula is:

LiPF₆→LiF↓+PF₅↑

PF₅+H₂O→POF₃+2HF↑

The pyrolysis process produces pyrolysis waste gas and natural gas combustion waste gas. After being collected in a closed negative pressure, the pyrolysis waste gas is first treated by a cyclone dust collector, and then enters the "high temperature incineration + SNCR denitrification + rapid cooling + activated carbon injection adsorption + bag dust removal + two-stage alkali solution spraying" treatment before being discharged through a 35m high exhaust pipe.

The natural gas combustion waste gas is directly discharged through a 20m high exhaust pipe. POF3 and HF in the pyrolysis waste gas are treated by alkaline solution absorption, and the reaction formula is as follows:

2POF₃+3Ca(OH)₂→Ca₃(PO₄)₂+6HF↑

2HF+Ca(OH)₂→CaF₂+2H₂O

2.4. Grinding

The pyrolyzed material enters the grinder through a closed conveying system. After high-speed stripping, the metal material is decomposed into 0.5mm metal particles and the active material is decomposed into battery black mass with a particle size of less than 50μm. The grinding waste gas generated during the grinding process is discharged through a 20m high exhaust pipe after "three-stage bag" dust removal. The collected battery black mass is sent to the buffer silo through a closed conveying system.

2.5. Screening

The ground material enters the screening machine through a closed conveying system, and the metal particles and battery black mass in the material are separated by the screening machine. Most of the battery black mass in the material is screened material, which is collected and sent to the cache silo through a closed conveying system. The screened material is metal particles such as copper and aluminum, diaphragms, and a trace amount of battery black mass, which are sent to the air separator through a closed conveying system for further separation. The screening exhaust gas generated during the screening process is discharged through a 20m high exhaust pipe after being treated with a "three-stage bag" dust removal. The collected battery black mass is sent to the cache silo through a closed conveying system.

2.6. Winnowing

The material on the sieve enters the air separator through a closed conveying system, and the metal particles are further separated from a small amount of battery black mass through air separation. All the battery black mass in the material enters the air separation waste gas, which is discharged through a 20m high exhaust pipe after being treated with a "three-stage bag" dust removal. The collected battery black mass is sent to the buffer silo through a closed conveying system; the metal particles selected by air enter the next magnetic separation process.

2.7. Gravity sorting

In the gravity separator, the copper-aluminum mixed material is separated into copper particles and aluminum particles, and the product purity reaches more than 98%.

The copper and aluminum particles collected by the gravity separator are packed in bags through the discharge port and sold as general solid waste. The waste gas from the separation is discharged through a 20m high exhaust pipe after being treated with a "three-stage bag" dust removal system, and the collected battery black mass is sent to the buffer silo through a closed conveying system.