Reversible Na15Sn4 alloy compensation for hard carbon anodes to enhance initial coulombic efficiency in sodium-ion full cells†

Abstract

An effective sodium compensation strategy employs Na15Sn4 alloy as a dynamic sodium reservoir paired with hard carbon (HC) anodes, undergoing reversible dealloying at low potentials (<0.5 V vs. Na⁺/Na) to release active Na ions, thereby compensating for irreversible sodium losses during initial cycles. The Full-cell configurations with NaSn@HC in Na3V2(PO4)3 cathode system achieve 90.1% ICE, outperforming conventional hard carbon anodes by more than 50%.