Ionic liquid electrolytes supporting high energy density in sodium-ion batteries based on sodium vanadium phosphate composites.

Sodium-ion batteries (SIBs) are widely considered as alternative, sustainable, and cost-effective energy storage devices for large-scale energy storage applications. In this work, an easily fabricated sodium vanadium phosphate-carbon composite (NVP@C) cathode material shows a good rate capability, and long cycle life (89% capacity retention after 5000 cycles at a rate of 10C) with an ionic liquid electrolyte for room temperature sodium metal batteries. The electrochemical performance of a full-cell sodium ion battery with NVP@C and hard carbon electrodes was also investigated at room temperature with an ionic liquid electrolyte. The battery exhibited 368 W h kg-1 energy density and 75% capacity retention after 100 cycles, outperforming the organic electrolyte-based devices.