The slurry mixture was coated on a copper foil (9 µm thickness) and dried under vacuum at 60 ˚C overnight. The dried electrodes were punched in the form of discs (diameter 12 mm) and the loading of the active material was 1.5-2 mg cm -2 . CR 2032 coin cells were assembled in an argon filled glove box (O2 < 0.5 ppm, H2O < 0.5 ppm) using glass fiber B (Whatman Glass Microfiber Filters) as the separator and potassium metal (98%, Thermo Fisher) as the counter and reference electrode. 1 M bis(fluorosulfonyl)imide potassium salt (KFSI) dissolved in 1:1 volume ratio of ethylene carbonate (EC) and diethyl carbonate (DEC) was used as the electrolyte. Galvanostatic charge discharge (GCD) measurements were tested in NEWARE battery cyclers (5V, 20 mA). Cyclic voltammetry (CV) measurements were tested in Biologic VSP potentiostat. Coin cells were rested for 12 h before electrochemical measurements were carried out under different potential ranges including 0.2-2.5 V and 0.001-2.5 V (vs. K + /K) at various current densities and scan rates.