Synergistic Influence of Anode Composition and Electrolyte Interactions in Sodium-Ion Cells

Sodium-ion batteries (SIBs) present a promising low-cost alternative to lithium-ion batteries due to the extensive availability of sodium resources. However, several challenges need to be addressed for SIBs to achieve commercial viability, particularly concerning the anode materials. Hard carbon, a popular choice of anode in SIBs, can facilitate highly reversible sodium storage through complex diffusion pathways and storage sites. However, a major challenge with this intercalation type anode is the insufficient storage capacity and low coulombic efficiency. On the other hand, tin (Sn) alloys with sodium at a high specific capacity (847 mAh/g), undergoing phase changes during electrochemical operation. The complication pertaining to Sn is due to its vulnerability to particle deformation and consequent volume expansion. This work investigates the synergistic role of anode compositions and electrolyte interactions on the electrochemical performance of sodium vanadium phosphate (NVP) based sodium-ion cells. A comparative analysis of the specific capacity retention among the anode composites was carried out with carbonate ester (NaClO₄ in PC: FEC (10%v/v)) and ether (NaPF₆ in diglyme) electrolytes. Further, an amalgamation of hard carbon and Sn as the anode is demonstrated to be a potential approach toward achieving high reversibility and specific capacity in SIBs.