Electrochemical measurements were performed as in our previous studies . Activated carbon cloths (ACCs) were directly used as electrodes, whereas powdered carbons, were made into free-standing carbon electrode films by mixing carbon powder (95 wt%) with PTFE binder (5 wt%) in ethanol, rolling them to ~0.25 mm thickness, and drying at 100 °C for 24 h to remove residual solvents. All electrochemical cells were symmetric two-electrode coin cells, assembled in a N2-filled glovebox. Electrodes were cut with a stainless-steel manual punch (6.4 mm diameter), ensuring both electrodes in each cell had the same mass within 0.2 mg, which ranged from 3.5 to 5.2 mg for carbon films, and 5.5 to 8.5 mg for ACCs, due to their increased thickness. Mass loading ranged from 10.9 to 16.3 mg•cm -2 for films and 17.2 to 26.6 mg•cm -2 for ACCs. Electrodes were separated with a Whatman GF/A glass fiber separator, and ca.150 µL of electrolyte was added. Stainless steel (SS316) spacer disks and a spring were used as current collectors, and cells were sealed with a hydraulic crimper (Cambridge Energy Solutions) under the pressure of 80 kg/cm 3 for approximately 40 s. All components were stainless steel, supplied by Cambridge Energy Solutions.