Aging processes in high voltage lithium-ion capacitors containing liquid and gel-polymer electrolytes

Lithium-ion capacitors (LICs) are nowadays considered as one of the most interesting high-power devices, and they are used in an increasing number of applications. In the last years, several efforts have been made to increase the energy of these devices, but only a few studies investigated in detail the degradation processes taking place in LICs. In this contribution, we are reporting on a systematic investigation of the aging processes taking place in LIC containing liquid and gel-polymer electrolytes. We show that the use of both electrolytes enables the realization of LICs that operate at 4.5 V and have very good stability. Furthermore, we report that the aging of LICs involves the deterioration of the solid electrolyte interface (SEI) of the graphite electrode, which leads to a decrease of the concentration of LiC6/LiF and to an increase of phosphide (P/LixP) within the electrode. In the activated carbon electrode, the concentration of phosphide (P/LixP) and fluoride (C-Fx) increases, and trapping of Li-ions on the pores of the carbon occurs. These degradation processes are taking place simultaneously and might affect each other.

Automated summary

This paper systematically investigates the aging processes in LICs containing liquid and gel-polymer electrolytes, revealing key factors impacting the stability of LICs.