Operando interlayer expansion of curved graphene for dense supercapacitors

Summary

Multiscaling disordered graphene with curved crystallitesFigure 1A schematically illustrates the key distinctions between multiscale particulate graphene and conventional disordered and lamellar structures. The disordered rGO (D-rGO) network consists of randomly arranged, interconnected 3D porous sheets that facilitate short ion diffusion pathways but suffer from low electrode density due to excessive void volume. In such structures, capacitive energy storage relies on ion electrosorption within the porous network. In contrast, the densely packed lamellar structure, comprised of horizontally stacked 2D graphene sheets exhibits tortuous ion diffusion pathways and poor ion accessibility, limiting charge storage kinetics and capacitance. M-rGO addresses these shortcomings by integrating randomly oriented graphene sheets with abundant nanoscale curved crystallites. The disordered domains serve as ion reservoirs and are ‘transport highways’, while the crystallites contribute significantly to charge storage, creating a structure that is ideally suited to high energy and power density.Fig. 1: Schematic highlighting the differences between lamellar, disordered and multiscale graphene with morphological characterization of M-rGO.A Conceptual schematic illustrating the differences in structure in terms of density, ion transport and the BET-surface area normalized capacitance. B HR-TEM micrographs of M-rGO showing numerous curved graphene crystallites. C SEM micrograph of M-rGO particles.M-rGO synthesis follows a two-step thermal treatment of particulate graphite oxide (GtO) powder (depicted in Fig. S1, Supporting Information). In the first step, GtO is introduced into a preheated tubular furnace at 700 °C by using suction for conveying the particles across the heated zone of the furnace, and the product is captured in a fine mesh. The suction level is adjusted to maintain a steady flow and a dwell time of ~2 ± 1 s. The rapid heating rate triggers an exothermic removal of oxyg...