Accelerating charging dynamics in subnanometre pores
Svyatoslav Kondrat, Peng Wu, Rui Qiao, and Alexei A. Kornyshev
Supercapacitors store energy physically and have distinct advantages over batteries in terms of power density and cyclability. The widespread deployment of supercapacitors, however, is limited by their moderate energy density. Supercapacitors’ energy density can be increased using ionic liquids and electrodes with subnanometer pores, but this tends to reduce their power density and thus compromising their key advantage.
In collaboration with scientists at Imperial College at London, we unraveled the mechanisms of charging subnanometer pores with ionic liquids. We show that charging of ionophilic pores, a process complicated by a myriad of factors such ion crowding observes an effective diffusion law. In sharp contrast to conventional expectations, charging is fast because ion diffusion during charging can be an order of magnitude faster than in the bulk, and charging itself is accelerated by onset of collective modes. Further acceleration can be achieved using ionophobic pores and thus leading to charging behavior qualitatively different from that in conventional, ionophilic pores.
The insights gained from this study provide theoretical basis and guideline for developing supercapacitors with concurrently high power and energy densities using ionic liquids and ultra-porous electrodes.
S. Kondrat, P. Wu, R. Qiao, and A.A. Kornyshev, “Accelerating charging dynamics in subnanometre pores”, Nature Materials, 13, 387, 2014