Fabrication of porous Na3V2(PO4)3/reduced graphene oxide hollow spheres with enhanced sodium storage performance.

Sodium-ion batteries (SIBs) have long been recognized as a potential substitute for lithium-ion batteries, while their practical application is greatly hindered owing to the absence of suitable cathode materials with improved rate capability and prolonged cycling life. Na3V2(PO4)3 (NVP) has drawn extensive attention among the cathode materials for SIBs because of its fast Na+-transportable framework which enables high-speed charge transfer, but the poor electric conductivity of NVP significantly restricts the Na+ diffusion. To tackle this issue, in this work, porous NVP/reduced graphene oxide hollow spheres (NVP/rGO HSs) are constructed via a spray drying strategy. Due to the unique porous hollow architecture, the synthesized compound manifests a high reversible capacity of 116 mAh g-1 at 1 C (1 C = 118 mA g-1), an outstanding high-rate capability of 107.5 mAh g-1 at 10 C and 98.5 mAh g-1 at 20 C, as well as a stable cycling performance of 109 mAh g-1 after 400 cycles at 1 C and 73.1 mAh g-1 after 1000 cycles at 10 C. Moreover, galvanostatic intermittent titration technique demonstrates that the Na+ diffusion coefficient of NVP/rGO HSs is an order of magnitude larger than the pristine NVP. The remarkable electrochemical properties of NVP/rGO HSs in full cells further enable it a potential cathode for SIBs.