Effect of Calcination Temperature on the Transformation of Spent NCM811 into Efficient TMO Electrocatalysts

Abstract The expansion of electric vehicles has increased spent lithium-ion batteries (LIBs) containing valuable transition metals. Recycling these materials reduces economic costs and addresses resource shortages. Additionally, transition metal-based catalysts derived from spent LIBs can replace expensive noble metal catalysts. This study examines the catalytic performance of spent LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) materials, enhanced by adjusting mixed valence states and defect structures. Increasing calcination temperature transformed the layered structure into spinel and rock salt phases, inducing mixed valence states. Consequently, the optimized NCM catalysts exhibited improved catalytic activity in both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). The ORR onset potential increased by 0.07 V, while the OER overpotential decreased by about 26.9%. In a zinc-air battery, the optimized catalyst demonstrated a discharge capacity of 792.1 mAh g⁻ 1 and stable performance over 100 cycles. Operando X-ray absorption spectroscopy (XAS) confirmed Mn as the main active site, with Ni and Co enhancing Mn's activity as electron donors and acceptors. These findings suggest that calcination-induced structural changes and mixed valence states enhance Mn site reactivity, improving catalytic performance. Overall, this study highlights the feasibility of repurposing spent LIB cathode materials into efficient electrocatalysts, thereby improving the economic viability and sustainability of catalyst development.