Operando interlayer expansion of multiscale curved graphene for volumetrically-efficient supercapacitors

Abstract

Supercapacitors deliver high power but are limited in compact applications by low volumetric energy and power densities. Two-dimensional materials like graphene, despite their high packing density, are hindered by poor ion transport kinetics. A rapid thermal annealing step generates unusually curved turbostratic graphene crystallites, integrated and interwoven within disordered domains in micron-size particles to yield multiscale graphene. Ion insertion into the interlayers enables precise pore-ion matching and partial charge transfer, enabling a high Brunauer-Emmett-Teller surface area-normalized capacitance of 85 µF/cm². Here, we show that multiscale graphene exhibits rapid ion transport dynamics within the curved crystallites and disordered domains. When the thin electrodes are assembled into symmetric pouch cell devices, they deliver a stack-level volumetric energy density of 99.5 Wh/L in ionic liquid electrolytes and 49.2 Wh/L in organic electrolyte with a high power density of 69.2 kW/L at 9.6 Wh/L.