context: Electrochemical testing was performed in a 2032 coin-type cell using Na metal (Sigma Aldrich, USA) as the anode. Electrodes were fabricated by blending the prepared cathode powders (85 wt%), carbon black (10 wt%), and polyvinylidene fluoride (5 wt%) in N-methyl-2-pyrrolidone (Daejung Chem, Korea). The slurry was then cast on aluminum foil (Hohsen Corp., Japan) and pre-dried at 110 °C in an oven. Then, the electrode was further dried at 110 °C for 5 h in a vacuum oven, and the disks were punched out of the foil. The electrolyte solution was 0.5 M NaPF6 (Tokyo Chemical Industry, Japan) in a 1:1 volumetric mixture of ethylene carbonate (Sigma Aldrich, USA) and diethyl carbonate (Sigma Aldrich, USA) with 2 vol% fluoroethylene carbonate (Tokyo Chemical Industry, Japan). All cells were prepared in an Ar-filled glovebox (MBRAUN, Germany). The fabricated cathodes and sodium metal anodes were separated by a glass fiber (Advantec, USA) to prevent short circuiting. The loading amount of the active material for all electrodes was 3.0–4.0 mg cm−2 in the coin-type half-cell. The cells were typically tested in the constant current mode, within the voltage range of 2.0–4.3 V versus Na/Na+, where 1C = 150 mA g−1. For the full-cell test, pouch-type (3 × 5 cm) cells were fabricated and tested in the voltage range of 1.0–4.1 V at 15 mA g−1 at 25 °C. The loading amount of the active material was 9.5–10.0 mg cm−2. The anode was fabricated by blending hard carbon (provided by Aekyung Petrochemical, Korea) (80 wt%), carbon black (3 wt%), and polyvinylidene fluoride (17 wt%). The resulting slurry was covered over copper foil and dried at 110 °C for 5 h in a vacuum oven. The full cell balance was achieved by controlling the capacity ratio of anode to cathode (N/P ratio) at 1.15:1.