Ethanol-aerosol-derived in situ syngas roasting for lithium recovery from spent layered oxide cathodes

Abstract

The recycling of layered oxide cathodes (e.g., LiCoO₂, LiNi_xCo_yMn_zO₂ (x + y + z = 1)) hinges on the reduction of high-valence transition metals yet conventional methods are plagued by safety hazards, environmental risks, and high carbon emissions. Here, we develop an ethanol-aerosol-assisted roasting strategy that achieves a dual benefit: the cathode material itself acts as a catalyst to promote ethanol-aerosol pyrolysis, in situ generating syngas (H₂/CO), which in turn reduces the transition metals in the cathode for efficient lithium leaching. The residual H₂/CO in the tail gas can be captured and reused as an energy source. This approach combines the efficiency of gas-phase reduction with the safety of solid-phase reagents. Under the optimized conditions (600 °C, 30 min), the process achieved 97.3% lithium leaching efficiency with negligible transition metal dissolution (<0.1%) and is expected to lower direct CO₂ generation relative to conventional carbothermic reduction, owing to the involvement of H₂ as the reducing agent. To address the challenge of low solid-to-liquid ratio in subsequent leaching, we developed two scalable solutions: acid–water sequential leaching and ethanol–HCl co-atomization roasting, enabling high lithium extraction (>97%) at ratios of up to 400 g L⁻¹. Finally, battery-grade Li₂CO₃ is obtained from the leachate, while the Co-rich residue can be further utilized for resource recovery. This work not only demonstrates efficient cathode recycling, but also offers a novel catalytic strategy for sustainable syngas production.