context: Typically, the working electrodes were fabricated by mixing 10 wt% of the binder polytetrafluoroethylene (PTFE), 10 wt% conductive agent (Super-P-Li) and 80 wt% of active materials (MnO2, K0.296Mn0.926O2 and active carbon). Ethanol was used to make the above materials into a slurry and Ni foam was employed as the current collector to coat the slurry with a mass loading of around 3 mg cm−2. Each electrode was dried for 6 hours in the oven and finally subjected to a pressure of 10 MPa. Electrochemical tests were performed on a three-electrode system with 1 M potassium sulfate as the electrolyte with the HgO/Hg as the reference electrode and Pt foil as the counter electrode. The CHI 660E Electrochemical Workstation was used to test the galvanostatic charge–discharge (GCD) and cyclic voltammetry (CV). The Zahner IM6 Electrochemical Workstation was employed to measure the electrochemical impedance spectroscopy (EIS). The LAND battery system was used to test the cycling life.
answer: 1 M potassium sulfate