Flexible all-solid-state asymmetric supercapacitors with three-dimensional CoSe2/carbon cloth electrodes

Abstract

As electrode materials for energy storage devices, metal chalcogenides have recently attracted great attention due to their unique structure related electrochemical properties. In this paper, hierarchical CoSe₂ nanostructures are successfully grown on conductive carbon fabrics with robust adhesion by a facile two-step method. The electrochemical properties of the as-prepared hierarchical CoSe₂ architectures were investigated in three- and two-electrode systems. In the three-electrode system, the hierarchical CoSe₂ architectures exhibit a large specific capacitance of 332 mF cm⁻² at a current density of 1 mA cm⁻². After charging/discharging for 5000 cycles, the electrode still showed superior stability with the capacity retention of about 95.4%. When assembled into asymmetric supercapacitors (ASCs) based on the hierarchical CoSe₂ negative electrode and MnO₂ nanowire positive electrode, the potential window increased to 1.6 V, larger than that of symmetric supercapacitors (SCs) based on CoSe₂//CoSe₂ electrodes. And a high energy density of 0.588 mW h cm⁻³ at a power density of 0.282 W cm⁻³ was also reached for the fabricated ASCs. Excitingly, the electrochemical performance of the as-assembled ASCs showed little degradation even under severe bending conditions, demonstrating excellent flexibility and mechanical stability. The as-grown CoSe₂ electrode with a 3D hierarchical structure can be a potential candidate for high-performance ASCs because of its improved electrochemically active sites, electronic conductivity and the reduced ion diffusion path.