Sulfuric acid aerosol roasting for closed-loop recycling of spent LiFePO4 cathodes

The rapid growth in end-of-life LiFePO 4 batteries demands sustainable recycling technologies. However, conventional leaching methods suffer from excessive chemical consumption and high saline wastewater discharge, posing environmental and economic challenges. Here, we report a sulfuric acid aerosol roasting strategy, employing air as a green oxidant, that enables efficient selective lithium extraction with near-stoichiometric acid usage. During roasting, sulfuric acid droplets undergo evaporative concentration, forming a thin H 2 SO 4 film on LiFePO 4 particles that drives interfacial redox reactions. The H 2 SO 4 film creates a gas–liquid–solid interface that mediates redox reactions among LiFePO 4 , O 2 , and the generated SO 2 , producing water-soluble Li 2 SO 4 and insoluble FePO 4 . In this process, O 2 serves as the terminal oxidant, allowing SO 2 to be fully reoxidized and thus preventing its emission. In addition, unreacted acid aerosol is carried away with the off-gas and can be efficiently recovered, enabling near-theoretical acid consumption. Upon roasting at 300 °C for 45 min, the process delivers 99.9 % Li leaching efficiency with minimal Fe (1.0 %) and negligible P (<0.1 %) dissolution. Coupled with a fluidized roasting design, this method ensures uniform aerosol–solid contact and high throughput, presenting a scalable, environmentally benign solution for LiFePO 4 recycling. The resulting FePO 4 residue can be directly utilized to regenerate LiFePO 4 with excellent cycling stability, thereby enabling closed-loop LiFePO 4 regeneration.