Pre-engineering artificial solid electrolyte interphase for hard carbon anodes for superior sodium storage performance.

A 5-nm-thick artificial solid electrolyte interface (SEI) was engineered for the hard carbon anodes of sodium-ion batteries. Benefiting from the artificial SEI, the hard carbon anode shows a significantly improved initial Coulombic efficiency of 94% and superior rate performance with a reversible capacity of 247 mA h g -1 after 800 cycles at 1C, 220 mA h g -1 after 400 cycles at 6C.