Enhanced electrochemical performance of hybrid SnO2@MOx (M = Ni, Co, Mn) core–shell nanostructures grown on flexible carbon fibers as the supercapacitor electrode materials

Abstract

In this study, hierarchical SnO₂@MO_x (SnO₂@NiO, SnO₂@Co₃O₄, and SnO₂@MnO₂) heterostructures grown on carbon cloth (CC) for high performance supercapacitors were fabricated by a two-step solution-based method involving a hydrothermal process and a chemical bath deposition, which utilizes the better electronic conductivity of SnO₂ nanosheets as the supporting backbone to deposit MO_x for supercapacitor electrodes. Particularly, the as-formed SnO₂@MO_x heterostructure electrodes showed better electrochemical performance than bare SnO₂ nanosheets. Remarkably, the SnO₂@MnO₂ heterostructure electrode showed the highest discharge areal capacitance (980 mF cm⁻² at 1 mA cm⁻²), good rate capability (still 767 mF cm⁻² at 20 mA cm⁻²), and excellent cycling stability (∼21.9% loss after 6000 repetitive cycles at a charge–discharge current density of 1 mA cm⁻²). The enhanced pseudocapacitive performance was mainly attributed to its unique hybrid structure, which provides fast ion and electron transfer, a large number of active sites, and good strain accommodation. The excellent electrochemical performance of the as-obtained heterostructures will undoubtedly make these hybrid structures attractive for high performance supercapacitors with high power and energy densities.