High capacity Graphene/α-MnO2 nanocomposite cathodes for Li–O2 batteries

• Graphene/α-MnO2 composite cathodes were produced by mechanical alloying method.
• Decoration of α-MnO2 nanowires on Graphene sheets result in increased the specific capacity.
• Graphene/α-MnO2 composite cathode containing 50 wt.% Graphene showed 1250 mAhg−1 stable specific capacity until 22nd cycle.

Graphene/α-MnO2 nanocomposite cathodes containing various amount of α-MnO2 catalysts (10 wt.%, 30 wt.%, 50 wt.%) were produced using planetary ball milling. The charge–discharge characteristics of the Li–O2 cells with composite cathodes have been investigated from 2.15 V to 4.35 V at a constant current density of 0.1 mA cm−2 with ECC–Air cells. In order to investigate lithium oxide formation and decomposition reactions on the Graphene/α-MnO2 cathode, cyclic voltammetry test was performed at a scan rate of 0.1 mV/s. The Li–O2 cell with a Graphene/α-MnO2 nanocomposite cathode containing 50 wt.% α-MnO2 exhibited a 6000 mAhg−1 discharge capacity at full discharge, 2500 mAhg−1 stable specific capacity up to 10th cycle at the state of 10 h charge and discharge and a 1250 mAhg−1 specific capacity until 25th cycle at the state of 5 h charge and discharge. This study demonstrated that Graphene/α-MnO2 nanocomposite cathodes on nickel foam might be a good alternative cathode material for Li–O2 batteries in the future.