This capacity range was selected to maximize the average R 2 value of the best fit lines across the entire current range, which ranged from 0.9996 to > 0.9999. To obtain accurate data, the same capacity range should be used across the entire current range, and the optimal capacity range should be determined for each specific system. The minimum current density was limited to 5 mA cm -2 because it was found that the sloping voltage profile of LCO, unlike the flat voltage profile of LFP, caused inaccuracy of the extrapolated voltage at very low current densities .