is the gradient of the discharging slope (V s -1 ). CT has units of Farads (F). This equation assumes that the gradient is constant over the chosen voltage range of analysis. While most groups used Equation 1, Group 12 analysed the dataset using a different approach also seen in the literature . This method involves calculating the energy stored in the device by integration of the discharge curve and using this value to calculate the capacitance via the energy-capacitance relationship for an ideal supercapacitor (SI Section 3). This approach gives comparable results to Equation 1 for ideal datasets. All groups analysed the discharge profile to calculate the capacitance. We recommend that research groups report the voltage range used to calculate the discharge slope as this impacts the final results. Groups should also report whether the Ohmic voltage drop was excluded from the calculation of the discharge slope.