External vibrations can destroy the specific capacitance of supercapacitors - From experimental proof to theoretical explanations

Today, nearly all publications related to supercapacitors suggest their use in electric vehicles and mobile technologies. They only report the performance under static conditions, which is far from reality as vibrations cannot be ignored in the above mentioned applications. Over the last few years, there have been some studies trying to understand the effect of external vibrations on the performance of Li-ion cells. Such studies, still being ignored for supercapacitors, can have a direct impact on their industrial applications. In this paper, the results establish that supercapacitors will also have a significant variation in specific capacitance, if they are operated under the influence of external vibrations. Actually, the external vibrations can lead to a loss of >50% in the specific capacitance of supercapacitors. Intriguingly, pseudocapacitors are affected far more than EDLCs. These results can also be explained theoretically by consideration of the cavitation collapse induced by the external energy, which leads to thermal activation of molecules or generation of radicals near the electrode-electrolyte interface. This directly impacts the rate constants of electron transfer reactions in solution, near the electrodes. The results can tilt the advantage in favour of carbon based electric double layer capacitors in applications, where external vibrations are envisaged.