Robust three-dimensional graphene skeleton encapsulated Na3V2O2(PO4)2F nanoparticles as a high-rate and long-life cathode of sodium-ion batteries

Abstract

Na3V2O2(PO4)2F (NVOPF) is a promising cathode material for sodium-ion batteries (SIBs) due to its high working voltage and theoretical capacity. However, the electrochemical performance is strongly impeded by its poor intrinsic electronic conductivity. Herein, we integrated the high flexible graphene sheets with NVOPF through a spray-drying method to re-construct its structure. The NVOPF nanocrystalline particles are homogeneously embedded in the high electronic conductive graphene framework. As a cathode of SIBs, the robust NVOPF/rGO microsphere composite exhibits excellent electrochemical performance: high specific capacity (127.2mAhg−1), long-term cycling stability (83.4% capacity retention at 30C after 2000 cycles) and superior high rate performance (70.3mAhg−1 at 100C). Furthermore, the Na+ insertion/extraction mechanism is also investigated by in-situ XRD and ex-situ HRTEM monitor technologies. This work demonstrates that the constructed 3D graphene skeleton serves as a high-efficient electronic conduction matrix and improves the electrochemical properties of electrode materials for advanced energy storage applications.