Oxygen Vacancies‐rich Manganese Oxide with Flower‐like Nanosheets for High Performance Supercapacitors

Here, flower‐like manganese oxide with enriched oxygen vacancies were reported for high performance supercapacitors. The moderate oxygen‐vacancy were achieved by controlling annealing atmosphere. Benefiting from improving the conductivity and the density of active sites, MnO x −Ar sample as an electrode material has remarkable specific capacity (339 mAh g −1 at 0.5 A g −1 ), extraordinary rate capability (90 % capacity retention at 1 A g −1 ), and good cycling property (90 % capacity retention at 1 A g −1 after 5000 cycles). Additionally, the asymmetric supercapacitor (ASC) was assembled which used the MnO x −Ar sample as cathode and Kochen Black (KB) as anode, which displayed a remarkable energy density (16 Wh kg −1 ) at a large power density (7593 W kg −1 ). These results, on the one hand, further expand the application of MnO 2 ‐based materials, and on the other hand, offer a new perspective for the oxygen non‐stoichiometry in material electrochemistry.