Largely Increased Lithium Storage Ability of Mangnese Oxide through a Continuous Electronic Structure Modulation and Elevated Capacitive Contribution

An ultrathin MnO2 sheet assembled three-dimensional flower microsphere grown on nitrogen-doped graphene is synthesized through a hydrothermal treatment method. When tested as an anode in a lithium-ion battery, the obtained material exhibits a high discharge capacity of 993 mAh g–1 in the second cycle at 0.1 A g–1, which goes up to 2243 mAh g–1 gradually after 135 charge/discharge cycles. This phenomenon turns out to be related to the deep coupling between nitrogen-doped graphene and MnO2 caused by morphology evolution of the composite upon cycling. Also, kinetics analysis reveals the elevated capacitive contribution after cyclic reaction, indicating the ever enhanced phase interface charge storage mechanism associated with the morphology evolution. Otherwise, the first-principles calculations also indicate the electronic structure of MnO2 can be efficiently modulated by coupling with a conductive graphene substrate, through a covalent C–Mn or N–Mn bond; thus, the deep coupling between nitrogen-doped graph...