Mixed phase hierarchical Ni9Se6/Cu4O4/Cu4O2/Cu4 core-shell architectures via surfactant-free approach using waste copper wicks for hybrid supercapacitors

Abstract

Recently, for energy storage materials, various surfactant-less synthesis methods have been attaining extensive attention from researchers. Herein, we utilized the wasted desoldering copper wicks (E-waste) as the base substrate to synthesize hierarchical core–shell maze-corn-like nickel selenide/copper oxide (NiSe/Cu4Ox) architectures by a facile two-step synthesis process. Initially, the Cu4Ox nanorods (NRs) were grown directly over the surface of the flat braided E-waste copper wicks by thermal oxidation, followed by a facile electrodeposition method to coat the pre-existing Cu4Ox NRs with NiSe nanoparticles. The optimized NiSe-120/Cu4Ox-3 electrode exhibited superior electrochemical characteristics (138.27 µAh cm−2 at 4 mA cm−2) compared to the other electrodes, owing to the contribution of core and shell materials, and sustained an ultra-long cycling test of 50,000 charge/discharge cycles with an excellent capacity retention of 98.7%. Inspired by commercially available AA battery, the as-synthesized working electrode was coupled with activated carbon-coated nickel foam to fabricate a cylindrical-type (C-type) hybrid supercapacitor (HSC) device, with an areal capacitance of 233.1 mF cm−2 accompanied by an extraordinary cycling efficiency of 99.1%. Furthermore, the C-type HSC device exhibited maximum energy and power densities of 70.9 µWh cm−2 and 14,000 µW cm−2, respectively and it was tested by powering portable electronics for real-time application.