Reconstruction of Conformal Nanoscale MnO on Graphene as a High-Capacity and Long-Life Anode Material for Lithium Ion Batteries

Abstract

To tackle the issue of inferior cycle stability and rate capability for MnO anode materials in lithium ion batteries, a facile strategy is explored to prepare a hybrid material consisting of MnO nanocrystals grown on conductive graphene nanosheets. The prepared MnO/graphene hybrid anode exhibits a reversible capacity as high as 2014.1 mAh g⁻¹ after 150 discharge/charge cycles at 200 mA g⁻¹, excellent rate capability (625.8 mAh g⁻¹ at 3000 mA g⁻¹), and superior cyclability (843.3 mAh g⁻¹ even after 400 discharge/charge cycles at 2000 mA g⁻¹ with only 0.01% capacity loss per cycle). The results suggest that the reconstruction of the MnO/graphene electrodes is intrinsic due to conversion reactions. A long-term stable nanoarchitecture of graphene-supported ultrafine manganese oxide nanoparticles is formed upon cycling, which yields a long-life anode material for lithium ion batteries. The lithiation and delithiation behavior suggests that the further oxidation of Mn(II) to Mn(IV) and the interfacial lithium storage upon cycling contribute to the enhanced specific capacity. The excellent rate capability benefits from the presence of conductive graphene and a short transportation length for both lithium ions and electrons. Moreover, the as-formed hybrid nanostructure of MnO on graphene may help achieve faster kinetics of conversion reactions.