A Facile Synthesis of Monodispersed Na3V2(PO4)3 Nanospheres Anchored on Cellular Graphene Oxide as a Self-supporting Cathode for High-Rate Sodium Storage

Na3V2(PO4)(3) (NVP) has been considered as a promising cathode for its high operating voltage and large capacity, though it suffers from an inherent low electronic conductivity and Na+ ion mobility. In this work, guided by an oriented freeze-casting strategy, monodispersed 20 nm NVP nanospheres combined with a cellular graphene oxide (CGO) matrix has been successfully synthesized, which could be directly applied as a self-supporting cathode for sodium storage. This NVP/CGO cathode can deliver a high capacity of 70.4 mAh g(-1) at a current density of 20 C and can retain 95% capacity even after 1000 cycles at 2 C. Moreover, the NVP/CGO self-supporting electrode can be employed as a bipolar material for symmetrical full cell applications. The full cell exhibits a high capacity of 103 mAh g(-1) with an output voltage of 1.75 V and keeps 75% of its initial capacity after 100 cycles at 1 C. We believe this oriented freeze-casting design concept can be generalized to fabricate various monodispersed nanoparticles on different 3D porous matrixes for energy storage applications.