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.