Tailoring the microstructure and solid electrolyte interface of hard carbon to realize high-initial-coulombic-efficiency and high-rate sodium storage

•The hard carbon is prepared from the precursor with crosslinked network structure.•The defect sites and interlayer distance of the hard carbon is tuned.•The thinner SEI endows the anode with lower interface impedance and faster kinetics.•The hard carbon anode shows higher initial Coulombic efficiency of 87%.•The hard carbon anode delivers superior rate performance of 205 mA h g−1 at 6 C.