Rationally assembled rGO/Sn/Na2Zr(PO4)2 nanocomposites as high performance anode materials for lithium and sodium ion batteries
Zr(HPO4)2 is a promising anode material for secondary batteries due to its intrinsic layered structure. However, poor electronic conductivity and low coulombic efficiency hinder its practical application. To overcome those disadvantages, Sn/Na2Zr(PO4)2 composites were obtained by one-pot ion exchange and further wrapped with reduced graphene oxide (rGO) sheets to form rGO/Sn/Na2Zr(PO4)2 ternary composites with a three-dimensional network structure. The ternary composites exhibited enhanced reversible capacity and rate capability, which can be attributed to the structural and physical properties of each component. It was found that the large interlayer space of Na2Zr(PO4)2, the ability of Sn to form alloys with lithium, and the intrinsic ultra-large specific surface of the reduced graphene oxide sheets together afford the ternary composites with high specific capacity for lithium and sodium storage. The electron and ion conductivities of Sn and reduced graphene oxide, and the three-dimensional network of the composites provide the ternary composites with great rate capabilities. In addition, the reduced graphene oxide sheets in the ternary composites can effectively improve the electrochemical kinetic properties. Furthermore, the overall electrochemical properties of the rGO/Sn/Na2Zr(PO4)2 ternary composites can be tuned by varying the ratios of the three components.