Structural Rearrangement of Expanded Graphite Through Ball Milling Method for Ultrafast Energy Storage Electrodes

Graphite has been employed as an energy storage material due to its ion intercalation capability. Nevertheless, the application of graphite in supercapacitors has been limited due to its strong bonding nature formed by sp²-hydridized C─C. Herein, structural rearrangement of expanded graphite (EG) was achieved through planetary ball milling method. High-levels of compressive and shear forces during milling not only rearranged the graphene stacks in the direction parallel to (002) plane but also developed a three-dimensional (3D) graphite structure with (101) crystallinity. This crystallographic rearrangement of milled EG (MEG) restores electrically conductive sp²-domains and regenerates intra- and interparticle electron transfer pathways. Furthermore, MEG revealed a highly porous structure with enhanced microporosity, balancing the macro-, meso-, and micropore ratio. The synergy of morphological and crystallographic rearrangements in MEG enhances the simultaneous ion and electron transport kinetics for electric double layer formation, making it suitable for ultrafast electric double layer capacitor electrodes (80 F/g at 50 A/g).