Direct Growth of Flower‐Like δ‐MnO₂ on Three‐Dimensional Graphene for High‐Performance Rechargeable Li‐O₂ Batteries

Abstract

A challenge still remains to develop high‐performance and cost‐effective air electrode for Li‐O 2 batteries with high capacity, enhanced rate capability and long cycle life (100 times or above) despite recent advances in this field. In this work, a new design of binder‐free air electrode composed of three‐dimensional (3D) graphene (G) and flower‐like δ‐MnO 2 (3D‐G‐MnO 2 ) has been proposed. In this design, graphene and δ‐MnO 2 grow directly on the skeleton of Ni foam that inherits the interconnected 3D scaffold of Ni foam. Li‐O 2 batteries with 3D‐G‐MnO 2 electrode can yield a high discharge capacity of 3660 mAh g −1 at 0.083 mA cm −2 . The battery can sustain 132 cycles at a capacity of 492 mAh g −1 (1000 mAh g carbon −1 ) with low overpotentials under a high current density of 0.333 mA cm −2 . A high average energy density of 1350 Wh Kg −1 is maintained over 110 cycles at this high current density. The excellent catalytic activity of 3D‐G‐MnO 2 makes it an attractive air electrode for high‐performance Li‐O 2 batteries.