High-energy-density electric double-layer capacitors (EDLCs) using tunable mesoporous carbon gel and ionic liquid electrolyte

Abstract

With the growing demand for efficient and reliable energy storage systems, electric double-layer capacitors (EDLCs) have attracted much attention due to their fast charging and discharging rates and long cycle life. However, enhancing its energy density remains a key challenge. In this study, a series of mesoporous carbon gels (CGs) with tunable pore size were synthesized and evaluated for their application as EDLC electrode materials. The advantages of the mesoporous structure in promoting ion diffusion and enhancing rate performance were verified by comparing with conventional microporous activated carbon (AC). While micropores (< 2 nm) are known to deliver high capacitance in aqueous and organic electrolytes, their accessibility in viscous ionic liquids is limited, thereby reducing power performance. Experimental results show that materials such as carbon gel synthesized at pH 5.9 and activated with CO₂ (denoted as CG59-CO₂) achieve energy densities as high as 180 Wh/kg at a voltage window of 4 V, which is comparable to the energy density of lithium-ion batteries that are widely used today. The devices maintained high power performances in the range of 10000–20000 W/kg, far superior to those of conventional AC materials. This study shows the potential for synergistic interaction between mesoporous carbon gels and ionic liquid electrolytes and provides new material design strategies for the development of next-generation electrochemical energy storage devices with both high energy density and high power density.