Hard carbon (HC) has been found to be an important anode material for sodium-ion batteries (SIBs) since graphite does not allow for the intercalation of sodium ions with a large size. While competitive capacity has been achieved using HC, the performance is still plagued by the low initial Coulombic efficiency (ICE), which stems from the electrolyte decomposition that forms a thick solid electrolyte interphase (SEI) and irreversibly trapped Na ions within the nano-pores. This defect becomes particularly profound when tested in full cell since the amount of Na is very limited.

In this study, we have systematically compared the performance of HC in carbonate and ether electrolytes and found that ether electrolyte demonstrates competitive performance with conventional carbonate at room temperature and significantly improved performance at -20 ^oC. The advantage of limited SEI from ether electrolyte also enabled a pre-lithiation treatment on the HC electrode using stabilized lithium metal powder (SLMP) to boost the initial Coulombic efficiency (ICE) to above 90% while maintaining the high capacity and good cycling stability. When coupled with Na₃V₂(PO₄)₃, the full cell with pre-lithiated HC demonstrates significantly improved ICE, cycling stability and capacity compared to pristine HC. Systematic characterizations and theoretical modelling have been performed to understand the effect of SLMP on the SEIs formed in different electrolytes. This work has provided a novel method to obtain high-performance SIBs with HC as the anode material.