To assess the rate capability across various nanoporous carbons and electrolytes, the capacitance C(J) was fitted against current density J using the expression 𝐶(𝐽) = 𝐶 " exp 1 𝐽 𝐽 " 2 3, where J0 represents the rate capability. To remove the contribution from the cell design, the data points corresponding to less than 80% capacitance retention were excluded.