Synthesis and lithium-storage properties of MnO/reduced graphene oxide composites derived from graphene oxide plus the transformation of Mn(vi) to Mn(ii) by the reducing power of graphene oxide

Abstract

In this report, a novel method is proposed to prepare MnO/reduced graphene oxide (rGO) composites via calcining the precursors (i.e. δ-MnO₂/graphene oxide composites) at 500 °C in Ar using no external reducing gas, in which graphene oxide (GO) successfully serves as a reductant by releasing CO during its thermolysis for the first time. By controlling the initial ratios of GO to KMnO₄, differently composed precursors can be obtained via the redox reaction between GO and KMnO₄, then leading to the formation of composites with different MnO/rGO ratios and dispersion of MnO on the rGO surface (denoted as MGC1 and MGC2). When applied as an active material in lithium ion batteries, MGC1 shows excellent cycling performance and capacity retention. Under 100 and 200 mA g⁻¹, MGC1 could deliver reversible capacities as high as 900 and 750 mA h g⁻¹, respectively, after more than 100 cycles. Considering the simple operation and low energy consumption in the whole material synthesis processes, the present strategy is feasible and effective for practical application. Even more importantly, the reductibility of graphene oxide upon thermolysis is utilized for the first time, which is meaningful for its extension in synthesis of functional nanomaterials.