Constant current charge-discharge measurements were conducted under various current densities (from 0.05 to 2 A•g -1 ) with the same voltage window (0-2.5 V) for at least 3 cycles per condition. Capacitance was calculated from the slope of the second half of the discharge curve, with results averaged across at least two cells (standard deviation < 5 F•g -1 ). Error bars reflect standard deviations across two cells. Sufficient cell pre-cycling was verified by repeating charge-discharge tests at 50 mA•g -1 to ensure stable capacitance after pore wetting.