The active material loading was 1.0-1.5 mg cm -2 . R2032 type coin cells were assembled in an Ar-filled glove box (water and oxygen concentrations below 0.1 ppm). A sodium disc was used as the counter electrode. A piece of Glass fiber filter was used as the separator. A solution of 1 M NaClO4 dissolved in ethylene carbonate:propylene carbonate (EC:PC =1:1 in volume) solvent was used as the electrolyte. Galvanostatic charge-discharge (GCD) was carried out on a Neware battery cycler (CT-4008) in a voltage range of 2.3-4.3 V (vs. Na + /Na) at room temperature. Cyclic voltammetry (CV) was performed on a VSP potentiostat (Bio-Logic) in a scan rate of 0.1 mV s -1 . Galvanostatic intermittent titration technique (GITT) measurement was carried out with a current pulse at 15 mA g -1 for 10 min and a 2-hour relaxation. Before the measurement, the electrodes were charged and discharged at 15 mA g -1 for two cycles. K diffusion coefficient was calculated by the following equation.