Fig.5 (a) cycling performance and coulombic efficiency of the Na||HC half-cells using 3.3? mol/L NaFSI/TMP electrolyte and 1.0? mol/L NaPF₆/EC:DEC (1∶1, by vol.) electrolyte (insets: Schemes of SEI passivation layers produced on a hard carbon surface in the above two electrolytes)^[54]; (b) initial charge/discharge curves of Sb-based anode in 0.8 mol/L NaPF₆/TMP+10% (volume fraction) FEC electrolyte and in 1 mol/L NaPF₆ EC/DEC (1∶1, by vol.) electrolyte^[57]; (c) mechanism of formation the SEI layer on the hard carbon anode in 0.9 mol/L NaFSI/TFEP electrolyte, (d) electrochemical performance of the HC||NVP full cell using a 0.9 mol/L NaFSI/TFEP electrolyte^[58]