Rational design of ultrathin 2D tin nickel selenide nanosheets for high-performance flexible supercapacitors

A new type of electrodes with attractive nanostructures is garnering extensive attention for application in energy storage technologies owing to the ultrahigh charge storage properties of these electrodes. Transition metal dichalcogenides (TMDs), especially ternary metal selenide-based TMDs, exhibit excellent electrical conductivity and a lower band gap. However, to date, only few studies have been reported on the application of Se-based nanostructures. To achieve high electrochemical performance, herein, we established a novel flexible electrode consisting of tin nickel selenide (SnxNi1-xSe2) vertically grown on carbon fiber cloth (CFC) with tunable composition and attractive nanostructures, which enhanced the electrical conductivity, provided more electroactive surface area, and shortened the electron/ion transport pathways. Due to the hierarchical nanostructures and superior electrical conductivity, the optimal Sn0.33Ni0.67Se2 electrode showed significantly improved electrochemical performance, which included an ultrahigh specific capacity of similar to 346 mA h g(-1) at a current density of 1.0 mA cm(-2), extraordinary rate capability, and outstanding durability. Remarkably, a flexible supercapacitor was assembled using Sn0.33Ni0.67Se2 as the positive electrode and Fe2O3@NG as the negative electrode, resulting in an ultrahigh energy density (similar to 90.3 W h kg(-1) at 0.631 kW kg(-1)), tremendous power density (20.14 kW kg(-1) at 67.2 W h kg(-1)), and super-high cycling life (similar to 96.41% capacity retention after 10 000 charge-discharge cycles at a high current density of 30 mA cm(-2)). These results clearly indicate that the hierarchical Sn0.33Ni0.67Se2 nanosheets have substantial potential for next-generation energy conversion and storage technologies.