Two-Dimensional Mn₃O₄Nanosheets with Dominant (101) Crystal Planes on Graphene as Efficient Oxygen Catalysts for Ultrahigh Capacity and Long-Life Li-O₂Batteries

Designing oxygen catalysts with well-defined shapes and high-activity crystal facets is of great importance to boost catalytic performance of Li-O₂batteries but challenging. Herein, we report the facet engineering of an ultrathin Mn₃O₄nanosheet (NS) with dominant (101) crystal planes on graphene (Mn₃O₄NS/G) as efficient and durable oxygen catalysts for high-performance Li-O₂batteries with ultrahigh capacity and long-term stability. Notably, the Mn₃O₄NS/G with the (101) facets and enriched oxygen vacancies offers a lower charge overpotential of 0.86 V than that of Mn₃O₄nanoparticles on graphene (1.15 V). Further, the Mn₃O₄NS/G cathode exhibits a long-term stability over 1300 h and an ultrahigh specific capacity up to 35,583 mAh g^-1at 200 mA g^-1, outperforming most Mn-based oxides for Li-O₂batteries reported. Both the experimental and theoretical results prove the lower adsorption energy of Mn₃O₄(101) for Li₂O₂in comparison with Mn₃O₄(211), manifesting the easier decomposition of Li₂O₂during the charging process. This work will open many opportunities to engineer Mn-based materials with a defined crystal facet for high-performance Li-O₂batteries.