Abstract:

The constant current charge/discharge mode, constant voltage charge mode and constant current cycling and floating mixed mode were applied to the ageing of commercial supercapacitors at both the nominal voltage of 2.7 V and overvoltage 3.0 V, respectively, followed by the comparison of the performance of the supercapacitors, including capacitance, impedance, etc. The results show that: ① The devices aged at constant voltage mode have the highest net discharge capacity higher than the nominal capacity of 10 F and have the highest net discharge energy more than 25 m·Wh. The devices aged at constant voltage have the biggest power capacitance and energy storage capacity; ② The devices under constant current mode show the lowest capacitance of less than 10 F, but the variation of resistance and capacity are the smallest, which reveals that the devices have a longer spanlife though the devices show the worst performance. ③ The equivalent resistance of the devices under the constant current cycling and floating mixed mode is up to 37.6 mΩ (the maximum of initial value is 30 mΩ), which is higher than the devices operated at the other two modes. The results indicate that the constant current cycling and floating mixed mode seriously damaged the devices, and show the greatest effect of various voltage on the resistance of the devices. This study provides a guideline that the choice of an appropriate operating mode will significantly decrease the cost of energy storage.

Key words: supercapacitor, constant current, constant voltage, mixed mode, ageing