Investigation of protic ionic liquid electrolytes for porous RuO2 micro-supercapacitors

Abstract

The rapid advancement of the Internet of things (IoT) with applications across various sectors urges the development of miniaturized energy-storage devices that can harvest or deliver energy with high power capabilities. While micro-supercapacitors can meet the high-power requirements of ubiquitous sensors connected to IoT networks, their low voltage and low energy density remain a major bottleneck preventing their wide-scale adoption. In this report, we develop micro-supercapacitors using RuO2 electrodes providing pseudocapacitive charge storage in protic ionic liquid-based non-aqueous electrolytes while enlarging their operational voltage. The triethylammonium bis(trifluoromethanesulfonyl)imide (TEAH-TFSI)-based interdigitated porous RuO2 micro-supercapacitors showed an extended cell voltage up to 2 V with 4 times more energy density compared with conventional H2SO4 electrolyte. We then developed an all-solid-state micro-supercapacitor using TEAH-TFSI-based ionogel electrolyte able to deliver high areal capacitance (79 mF cm−2 at 2 mV s−1) and long-term cycling stability that is superior to state-of-the-art ionogel-based micro-supercapacitors employing carbon-based or pseudocapacitive materials. This study gives a new perspective to develop all-solid-state micro-supercapacitors using pseudocapacitive active materials that can operate in ionic-liquid-based non-aqueous electrolytes compatible with on-chip IoT-based device applications seeking high areal energy/power performance.