Metal oxide/graphene composite anode materials for sodium-ion batteries

Due to the abundance of sodium sources and relatively high safety, sodium-ion batteries (SIBs) are considered as a promising candidate for next-generation large-scale energy storage systems. However, currently the lack of suitable anode materials is limiting the development of SIBs. Metal oxides (MOs) which have the advantage of rich material sources and high theoretical capacity have attracted lots of attention as anode for SIBs in scientific community. Nevertheless, due to the low conductivity, large volumetric change during charge/discharge process of SIBs, the material often demonstrates unsatisfactory cycling stability and capacity rate. Construction of material composites through incorporation of graphene to MOs with tailored nanostructure and composition has demonstrated promising performance in SIBs. In this review, we attempt to provide a comprehensive summary of the research development on the low-cost metal oxides/graphene composites (MOs/G) as anode materials for SIBs. The characteristics of different morphology, composition, crystal phases of MOs/G composites and their electrochemical properties in SIBs are demonstrated. The correlation of the morphological and structural properties of the MOs materials with their performance in SIBs is discussed. This timely review sheds light on the path towards achieving cost effective, safe SIBs with high energy density and long cycling life using MOs/G as anode materials.