Efficient Utilization of the Active Sites in Defective Graphene Blocks through Functionalization Synergy for Compact Capacitive Energy Storage.

Designing dense carbon materials with both high capacitance and good rate performance is crucial for future development of minimized and light-weight supercapacitors but remains challenging because sluggish ion transport inhibits the efficient utilization of the energy storage sites. Herein, we report a defective and functionalized graphene block (DFGB) prepared through ball milling using controllably reduced graphene oxide (RGO) as the precursor. Rational oxygen configuration enables good electrolyte wettability and improves ion migration kinetics, facilitating high utilization of the "self-doping" defects as active sites. Benefiting from this synergistic effect, the optimized DFGB with a high compact density of 0.92 g cm-3 shows high capacitances of 302 F g-1 and 278 F cm-3 at 1 A g-1 and good rate performance with a capacitance retention of 42% at 100 A g-1, which are among the best of the reported carbons. Moreover, the symmetric device at the commercial mass loading still shows a high energy density and remarkable cycle stability, demonstrating the importance of functionalization synergy in fully realizing the compact energy storage ability of carbon materials.