A NiCo bimetallic hydroxide electrode-based flexible Ni//Zn battery with smart electrochromic function for visually monitoring battery residual electricity

Flexible battery with a smart electrochromic function of changing color in the electrochemical process reveals great application potentials in the field of intelligent electronics. However, Ni//Zn battery with an electricity visual alerting function has seldom been reported by now. Herein, we designed a flexible Ni//Zn battery, assembled by the NiCo bimetallic hydroxide/Ni/indium tin oxide (NiCo BH/Ni/ITO) flexible electrode with an electrochromic feature. By optimizing the thickness of the middle Ni layer, the NiCo BH/Ni/ ITO electrode shows a coloration efficiency of 59.89 cm² C⁻¹ and a capacity of 7.15 µA h cm⁻² at a current density of 0.1 mA cm⁻². Correspondingly, the flexible electrochromic Ni//Zn battery shows a high energy density of 12.69 µW h cm⁻² at a power density of 160 µW cm⁻², outperforming those of transparent flexible supercapacitors and electrochromic batteries reported in literatures. Moreover, the flexible electrochromic Ni//Zn battery displays reversible color change during charging and discharging processes, rendering it a novel function to monitor the battery residual electricity by visual inspection. [Figure not available: see fulltext.].