Long-Lasting Panchromatic Electrochromic Device and Energy-Dense Supercapacitor Based on Zn-Doped NiO Microstars and a Redox-Active Gel

The technological importance of cost-effective zinc-doped nickel oxide (Zn:NiO) coatings is demonstrated by applying them to energy saving-electrochromic devices (ECDs) as well as energy storing-asymmetric supercapacitors (ASCs). These devices encompass an inexpensive nonaqueous gel electrolyte of ZnCl 2 /γ-butyrolactone/ferrocene (Fc)/poly(vinyl butyral), where Fc serves as a redox mediator and accelerates charge transfer and transport kinetics, enhancing both ion-storage and optical modulation responses. This report showcases the prowess of a simple doping and a redox-gel in an unprecedented manner, wherein the improved dc and ac electrical conduction by an order of magnitude, the star-like morphology of Zn:NiO compared to NiO microflowers, and the high conductivity of the gel (33 mS cm –1 ) come to the fore in an ASC [with activated carbon (AC) derived from corncobs as the anode, Zn:NiO//AC], which delivers a very high specific capacitance (SC) of 460 F g –1 (at 1.25 A g –1 ), comparable to expensive rare oxides, a battery like energy density of 164 W h kg –1 (at 1 kW kg –1 ), and a cycle life of 10,000 cycles with 95% SC retention. The potential of Zn doping is further showcased through the panchromatic visible light modulation of the Zn:NiO//WO 3 ECD, switching reversibly between the colorless and the dark black–brown states, accompanied by a remarkably high integrated transmission modulation (Δ T 400–900nm ) of 60.2%, sustained over 3500 cycles with no performance loss, and color/bleach times of 10 s/5 s, most suitable for smart window applications.