Insight into pre-sodiation in Na3V2(PO4)2F3/C @ hard carbon full cells for promoting the development of sodium-ion battery

Sodium-ion battery has been put into an eager consideration in the large-scale energy storage system, owing to its inexpensive cost ($/kWh) than that of the lithium-ion battery. The gap from research to industry still exists, however, including low energy density and unsatisfactory cycling lifespan in full cells. Here we report a Na-ion full cell with spray-dried Na3V2(PO4)2F3/C (NVPF/C) cathode and pre-sodiated hard carbon (HC) anode. It is demonstrated that the full cells (NVPF-HC), assembled with 100% presodiated HC anode, exhibits the best energy storage capability and rate performance. A remarkable reversible capacity of 114.1 mA h g−1 at 0.5C (attaining 95% of capacity for NVPF-Na anode half-cell), a desirable power performance with 90.6 mA h g−1 at a high rate of 20C, and an impressive cycling life (71.8% capacity retention after 600 cycles at 10C) are achieved. The outstanding battery performance is ascribed to that the electroactivity Na+ in HC can maximize the scavenger effect and forms the more stable solid-electrolyte interface (SEI). Moreover, an HC pre-sodiation degree dependent Na-ion battery performance is proofed. The findings in this paper offer new insights on the electrode design strategy, which facilitates the development of sodium-ion technology.