▎ 摘　　要

Designing oxygen catalysts with well-defined shapes and high-activity crystal facets is of great importance to boost catalytic performance of Li-O2 batteries but challenging. Herein, we report the facet engineering of an ultrathin Mn3O4 nanosheet (NS) with dominant (101) crystal planes on graphene (Mn3O4 NS/G) as efficient and durable oxygen catalysts for high -performance Li-O2 batteries with ultrahigh capacity and long-term stability. Notably, the Mn3O4 NS/G with the (101) facets and enriched oxygen vacancies offers a lower charge overpotential of 0.86 V than that of Mn3O4 nanoparticles on graphene (1.15 V). Further, the Mn3O4 NS/G cathode exhibits a long-term stability over 1300 h and an ultrahigh specific capacity up to 35,583 mAh g-1 at 200 mA g-1, outperforming most Mn-based oxides for Li- O2 batteries reported. Both the experimental and theoretical results prove the lower adsorption energy of Mn3O4 (101) for Li2O2 in comparison with Mn3O4 (211), manifesting the easier decomposition of Li2O2 during the charging process. This work will open many opportunities to engineer Mn-based materials with a defined crystal facet for high-performance Li-O2 batteries.