A simple, one-pot synthesis of molybdenum oxide-reduced graphene oxide composites in supercritical methanol and their electrochemical performance

Abstract

A simple and green supercritical methanol (scMeOH) route is developed to tightly anchor molybdenum oxide (MoO₂) nanoparticles on reduced graphene oxide (RGO). In scMeOH, graphene oxide is reduced, and MoO₂ nanoparticles with sizes of 10–20 nm are simultaneously deposited on the basal plane of RGO in a short time without using any reducing agents or additives. When tested as an anode in lithium ion batteries, the MoO₂–RGO composites show enhanced electrochemical performance compared to bare MoO₂. The composite with a MoO₂ loading of 37.0 wt% delivers a high reversible discharge capacity of 793 mA h g⁻¹ at 50 mA g⁻¹ and an excellent rate performance of 205 mA h g⁻¹ at 2.5 A g⁻¹. After 100 cycles of high rate testing of up to 50 A g⁻¹, the MoO₂–RGO composite recovers most of its initial capacity. The improved electrochemical performance of MoO₂–RGO can be attributed to the tight anchoring of nanosized MoO₂ on RGO and the mesoporous structure of the composite. Consequently, the transport length of Li diffusion into the MoO₂ phase is shortened, charge transfer kinetics at the electrode–electrolyte interface is facilitated, and the volume expansion associated with the conversion reaction can be accommodated.