How are lithium iron phosphate batteries recycled?

EVs require power batteries with ≥80% capacity retention. They serve as the heart of electric vehicles. However, once they fall below this threshold, they no longer meet the demands of electric vehicles. Consequently, the recycling of decommissioned power LiFePO4 batteries has become a pressing issue.

Industries used to prioritize LCO, NCM/NCA battery recycling, showing less interest in LiFePO4 battery recycling in the past. This reluctance stemmed from the perception that the cost of recycling LiFePO4 batteries outweighed their recycling value. However, since May 2021, there has been a noteworthy shift. LiFePO4 battery shipments have outpaced ternary lithium batteries, reversing a trend that persisted since 2018.

LiFePO4 batteries have significant market potential in energy storage, 5G base stations, new energy vehicles, and renewable energy grid integration. Phosphorus and lithium price hikes boost LiFePO4 battery recycling interest, securing its future market dominance as predicted by experts.

1. Pretreatment in LiFePO4 Battery Recycling

The LiFePO4 battery recycling process commences with pretreatment, which involves the disassembly of batteries and the extraction or reuse of valuable metals. This initial step is crucial for separating the cathode active material from the battery casing, separator, current collector, electrolyte, carbonaceous additives, and battery hookup components.

Pretreatment necessitates the dismantling of battery shells and the separation of various valuable components. Safety measures include discharging waste batteries using external resistors or immersing them in a salt solution to prevent electric shocks, fires, explosions, and potential chemical hazards.

Next, operators use machinery to crush the batteries. They sort the crushed components based on properties such as density, particle size, magnetism, and hydrophobicity.This sorting process initially separates the battery case, separator, plastic, aluminum foil, cathode, and anode, facilitating their separate recycling.

2. Cathode Material Recycling in LiFePO4 Battery Recycling

Current research on recycling waste LiFePO4 batteries primarily focuses on cathode materials. In fully discharged lithium-ion batteries, lithium primarily resides in the cathode. The waste generated during cathode production also holds significant recycling value.

Mainstream wet process mainly recovers valuable lithium from cathode materials while also extracting metals like iron and aluminum.

Using NaOH lye, we dissolve the cathode sheet, which allows the current collector aluminum foil to enter the solution as NaAlO2. After filtration, we neutralize the filtrate with a sulfuric acid solution to precipitate Al(OH)3, thus facilitating the recovery of aluminum. The filter residue contains LiFePO4, conductive agent carbon black, and LiFePO4 surface-coated carbon.

There are two methods for LiFePO4 recycling in LiFePO4 battery recycling:

Method 1: Dissolving the filter residue with sulfuric acid and hydrogen peroxide causes LiFePO4 to enter the solution as Fe2(SO4)3 and Li2SO4. Separate the filtrate from carbon impurities and adjust it with NaOH and ammonia water to precipitate iron as Fe(OH)3. Subsequently, precipitate the remaining liquid with a saturated Na2CO3 solution to obtain Li2CO3.

Method 2: Dissolving the positive electrode material filter residue with nitric acid and hydrogen peroxide results in the formation of FePO4 and subsequent precipitation of Fe(OH)3. precipitate the remaining acid solution with a saturated Na2CO3 solution to obtain Li2CO3, accomplishing the separate precipitation and recovery of Al, Fe, and Li.

3. Anode Material Recycling in LiFePO4 Battery Recycling

The demand for graphite anodes has surged with the widespread use of lithium-ion batteries, including 12V, 24V, and 36V lithium batteries. Graphite constitutes 12% to 21% (by mass) of waste lithium batteries, making it a substantial resource.

In regions with low graphite reserves, such as the United States and some European countries, the recycled graphite powder holds significant potential for reuse in battery production following modification.

Furthermore, copper foil in the anode is expensive and easily recyclable in LiFePO4 battery recycling. In general, the recovery of anode materials involves methods such as heat treatment, leaching, or grinding flotation.

Researchers have successfully regenerated graphite from spent lithium batteries through a straightforward process involving high-temperature smelting and sieving. In this process, it produces spherical copper foil particles separated from graphite, which one can obtain through ultrasonic vibration and sieving. The purity of recovered graphite can reach 99.5%, meeting battery-grade graphite material standards.

4. Electrolyte Material Recycling in LiFePO4 Battery Recycling

Electrolytes constitute approximately 15% of the cost of power batteries and contain valuable lithium ions. In LiFePO4 battery recycling, practitioners utilize various methods for electrolyte recycling, encompassing vacuum pyrolysis treatment, organic solvent extraction, and CO2 supercritical recycling.

Supercritical CO2 recycling involves using it as an extraction agent to separate the electrolyte from the battery separator and active material. CO2’s ability to dissolve non-polar substances makes it effective in this process. It is stable, non-toxic, and cost-effective, making it a crucial player in lithium battery electrolyte recycling.

5. Conclusion and Future Prospects

The recycling of waste LiFePO4 batteries has made significant strides, with the primary focus being on cathode materials. However, there’s room for deeper research into the recycling mechanisms of metals within cathode materials, alongside technology refinement.

Efforts in selective separation and purification of various metals, recovery of anode materials, and electrolyte recycling processes and principles need expansion. We should develop a cleaner, environmentally friendly, and streamlined recycling process to enhance recycling efficiency and unlock the economic value of all components of used lithium-ion power batteries. This approach will drive sustainable progress in LiFePO4 battery recycling, ensuring a brighter, eco-friendly future for energy storage systems.

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