Mechanochemical process enhancing pore reconstruction for dense energy storage of carbon-based supercapacitors

Improving the volumetric energy density of carbon electrode materials for supercapacitors is of significance to reducing the size of energy storage devices, and eliminating the ineffective pores in porous carbon electrode materials is the key to achieving dense storage of ions. Herein, we reconstruct the pore structure of commonly activated carbon via a facile high-energy mechanochemical process, by which modified activated carbon exhibits a much-increased packing density with an ultra-low specific surface area of 33 m2 g-1 without sacrificing the gravimetric specific capacitances, thereby enabling high volumetric capacitances up to 602 F cm-3. Gas adsorption characterization and small angle X-ray scattering tests collectively reveal the regulatory mechanism of mechanochemical process on pore structure reconstruction that high-energy mechanochemical treatment significantly eliminates the excess meso-/macro-pore volume to configure a compressed carbon skeleton structure and simultaneously increases proportions of micropore volume in the total pore volume, ultimately resulting in a cross-linked dense pore network structure. Benefitting from the optimized pore network and oxygen atoms introduced by mechanochemistry, the assembled aqueous symmetric supercapacitor in KOH electrolyte delivers a maximum volumetric energy density of 11.32 Wh L-1 when the volumetric power density is 223 W L-1. This work systematically reveals the effects of mechanical force on the pore reconstruction of carbon materials, and provides a simple method for enhancing the volumetric performances of carbon-based porous electrode materials.