A novel design of hybrid transparent electrodes for high performance and ultra-flexible bifunctional electrochromic-supercapacitors

In this study, a simple and cost-effective method of fabricating hybrid transparent conductive electrodes (TCEs) based on embedded silver nanowires (Ag NWs)/PEDOT: PSS was developed with the addition of low-temperature synthesis of Ni(OH)₂ and polyethylenimine ethoxylated (PEIE) composites as a novel interlayer. The hybrid TCEs with a Ni(OH)₂-PEIE interlayer exhibit remarkable volumetric capacitance of 443 F cm⁻³ with transparency of 86%, which is one of the highest values reported to date in the transparent supercapacitor. The fabricated bifunctional solid-state electrochromic-supercapacitor device with a transparency of 80% shows stable cyclic stability up to 10,000 charge/discharge cycles, extremely high coloration efficiency of 517 cm² C⁻¹ at 633 nm, and a fast switching speed (<0.6 s). The noted improvement is mainly caused by the Ni(OH)₂-PEIE interlayer influence the pore density of PEDOT: PSS which provides high surface area, thus resulting in efficient charge transfer pathways and fast ion diffusion. Moreover, a capacitance retention of 90% is achieved even after 8000 bending cycles at a bending radius of 1 mm and 15 times of crumpling is tolerated without noticeable degradation, implying excellent mechanical robustness and flexibility. The results present the significant potential of transparent hybrid electrodes for efficient energy storage and electrochromicity with stable transmittance changes, even during fast charge/discharge processes, demonstrating their potential as smart wearable energy storage devices.