Recovery of lithium iron phosphate cathode material from spent lithium-ion batteries using gradient pyrolysis

The recovery of spent lithium iron phosphate batteries (SLFPBs) has gained significant attention due to environmental concerns and the potential for valuable secondary resources. Among various recycling technologies for SLFPBs, pyrometallurgical processes are crucial but hindered by high roasting temperatures and secondary pollution from the decomposition of auxiliary salts. In this study, we present a gradient pyrolysis method for the efficient recovery of SLFPBs. By precisely controlling the temperature, aluminum foil and black powder were effectively separated at 350 °C, while organic impurities were removed at 650 °C. Lithium iron phosphate (LFP) synthesis was achieved through a reduction process at the same temperature. The thermochemical behavior of spent LFP cathode materials was investigated, providing insights into the mechanisms of aluminum foil and black powder separation. The thermodynamics of LFP oxidation and the subsequent reduction of its oxidation products were also elucidated. Additionally, phase and morphology changes of metals and impurities during the oxidation and reduction processes were analyzed. The discharge specific capacity retention of the re-synthesized materials was 94.34 % relative to the initial capacity (129 mAh·g^–1) after 200 cycles at 1C. This research offers a high-efficiency and short-flow recycling approach for SLFPBs, which could contribute significantly to the recovery of key components from lithium-ion batteries.