Revealing Pseudocapacitive Mechanisms of Metal Dichalcogenide SnS2/Graphene-CNT Aerogels for High-Energy Na Hybrid Capacitors

SnS2 nanoplatelet electrodes can offer an exceptionally high pseudocapacitance in an organic Na+ ion electrolyte system, but their underlying mechanisms are still largely unexplored, hindering the practical applications of pseudocapacitive SnS2 anodes in Na-ion batteries (SIBs) and Na hybrid capacitors (SHCs). Herein, SnS2 nanoplatelets are grown directly on SnO2/C composites to synthesize SnS2/graphene-carbon nanotube aerogel (SnS2/GCA) by pressurized sulfidation where the original morphology of carbon framework is preserved. The composite electrode possessing a large surface area delivers a remarkable specific capacity of 600.3 mA h g(-1) at 0.2 A g(-1) and 304.8 mA h g(-1) at an ultrahigh current density of 10 A g(-1) in SIBs. SHCs comprising a SnS2/GCA composite anode and an activated carbon cathode present exceptional energy densities of 108.3 and 26.9 W h kg(-1) at power densities of 130 and 6053 W kg(-1), respectively. The in situ transmission electron microscopy and the density functional theory calculations reveal that the excellent pseudocapacitance originates from the combination of Na adsorption on the surface/Sn edge of SnS2 nanoplatelets and ultrafast Na+ ion intercalation into the SnS2 layers.