Ultra-micropore confinement effect in physical activated carbon sphere enables low-temperature electrical double-layer capacitance

Abstract

Activated carbon with a high specific surface area used as electrical double-layer capacitor electrodes is commonly produced by chemical activation, while chemical activation processes are frequently associated with high pollution and costs. Herein, polystyrene-divinylbenzene-based activated carbon spheres (ACS) with large specific surface area were prepared through physical activation, in which the hierarchical porous structure provides a more favorable route for electrolyte ions penetration and transport. As a result, the supercapacitors utilizing ACS electrodes exhibit higher capacitance (108.5F/g at 1 A/g) and better rate performance. The assembled EDLCs not only stabilize for 30,000 cycles with capacity retention of 92.4% but also possess a superior rate performance even at 0°C. In situ electrochemical quartz crystal microbalance reveals that eliminating the ultra-micropore confinement effect can boost ions storage. This study not only shows an understanding of the charge storage mechanism of EDLCs but also provides a novel possibility for the practical application.