Ternary selenides nanosheets constituting coaxial structural electrode for flexible supercapacitors

Abstract

For flexible supercapacitors (FSCs), the structural collapse and performance degradation are still bottlenecks that need to be addressed. Herein, Ni-Co selenides (NCS) nanosheets are fabricated into "sponge" grown in situ on flexible conductive nickel-plated carbon cloth (NPCC), constructing the coaxial electrode structure, consisting of NCS nanosheets “sponge layer” (SL), Ni-plated layer (NL) and carbon fiber axis (CFA). The NC0.25S0.5-5/NPCC coaxial electrode shows a high areal capacitance of 6.47 F cm−2 at the 6 mA cm−2 (Hg/HgO reference electrode, 1 M KOH electrolyte) and excellent structural stability with no cracking or fracture after 5000 bending cycles. With the good electronic conductivity, the intermediate NL binds the SL active material and the flexible CFA substrate together to avoid breakage under mechanical deformation. A developed FSC device using the NC0.25S0.5-5/NPCC electrode shows the maximum energy density of 58.4 Wh kg−1. Besides, the excellent flexibility and coaxial structural stability endow the FCS with 90.5% retention of capacitance after 6000 cycles of electrochemical testing and negligible attenuation of electrochemical performance under bending at 180 ° in the last 1000 cycles.