Improving the Rechargeable Li-CO₂ Battery Performances by Tailoring Oxygen Defects on Li-Ni-Co-Mn Multi-Metal Oxide Catalysts Recycled from Spent Ternary Lithium-Ion Batteries

Rechargeable Li-CO2 batteries are considered as a promising carbon-neutral energy storage technology owing to their ultra-high energy density and efficient CO2 capture capability. However, the sluggish CO2 reduction/evolution kinetics impedes their practical application, which leads to huge overpotentials and poor cyclability. Multi-element transit metal oxides (TMOs) are demonstrated as effective cathodic catalysts for Li-CO2 batteries. But there are no reports on the integration of defect engineering on multi-element TMOs. Herein, the oxygen vacancy-bearing Li-Ni-Co-Mn multi-oxide (Re-NCM-H3) catalyst with the alpha-NaFeO2-type structure is first fabricated by annealing the NiCoMn precursor that derived from spent ternary LiNi0.8Co0.1Mn0.1O2 cathode, in H-2 at 300 degrees C. As demonstrated by experimental results and theory calculations, the introduction of moderate oxygen vacancy has optimized electronic state near the Fermi level (E-f), eventually improving CO2 adsorption and charge transfer. Therefore, the Li-CO2 batteries with Re-NCM-H3 catalyst deliver a high capacity (11808.9 mAh g(-1)), a lower overpotential (1.54 V), as well as excellent stability over 216 cycles at 100 mA g(-1) and 165 cycles at 400 mA g(-1). This study not only opens up a sustainable application of spent ternary cathode, but also validates the potential of multi-element TMO catalysts with oxygen defects for high-efficiency Li-CO2 batteries.