MOF-Derived Mn₂ O₃ Nanocage with Oxygen Vacancies as Efficient Cathode Catalysts for Li-O₂ Batteries

Designing efficient and cost-effective electrocatalysts is the primary imperative for addressing the pivotal concerns confronting lithium-oxygen batteries (LOBs). The microstructure of the catalyst is one of the key factors that influence the catalytic performance. This study proceeds to the advantage of metal-organic frameworks (MOFs) derivatives by annealing manganese 1,2,3-triazolate (MET-2) at different temperatures to optimize Mn₂ O₃ crystals for special microstructures. It is found that at 350 °C annealing temperature, the derived Mn₂ O₃ nanocage maintains the structure of MOF, the inherited high porosity and large specific surface area provide more channels for Li⁺ and O₂ diffusion, beside the oxygen vacancies on the surface of Mn₂ O₃ nanocages enhance the electrocatalytic activity. With the synergy of unique structure and rich oxygen vacancies, the Mn₂ O₃ nanocage exhibits ultrahigh discharge capacity (21 070.6 mAh g^-1 at 500 mA g^-1 ) and excellent cycling stability (180 cycles at the limited capacity of 600 mAh g^-1 with a current of 500 mA g^-1 ). This study demonstrates that the Mn₂ O₃ nanocage structure containing oxygen vacancies can significantly enhance catalytic performance for LOBs, which provide a simple method for structurally designed transition metal oxide electrocatalysts.