Transparent metal oxide interlayer enabling durable and fast-switching zinc anode-based electrochromic devices

Growing energy and environmental challenges have imposed higher requirements for the development of novel multifunctional energy storage and energy-saving devices. Electrochromic devices having similar configurations and working mechanisms with secondary batteries exhibit promising applications in dual-functional electrochromic-energy storage (ECES) devices. Electrochromic Prussian blue (PB) as typical battery cathodes are of great interest for ECES devices although they suffer from poor stability and limited capacity. In this study, a transparent metal oxide (NiO nanosheets) interlayer was incorporated to enhance the structural stability and capacity of PB while offering enlarged optical modulation (ΔT) and accelerated switching kinetics in the NiO/PB film. Impressively, the NiO/PB nanocomposite film exhibited a high areal capacity of 50 mA h m-2 and excellent electrochemical stability, simultaneously manifesting a large ΔT (73.2% at 632.8 nm), fast switching time (tc = 1.4 s, tb = 2.6 s) and higher coloration efficiency (CE = 54.9 cm2 C-1), surpassing those of the bare PB film (ΔT = 69.1% at 632.8 nm, tc = 1.6 s, tb = 4.1 s, CE = 50.9 cm2 C-1). Finally, a prototype zinc anode-based electrochromic device assembled with NiO/PB nanocomposite film exhibited a self-bleaching function and ΔT retention of up to 92% after 1000 cycles, and a 100 cm2 large area device was also demonstrated for high performance. Such a transparent metal oxide interlayer has enabled the construction of durable and fast-switching dual-functional zinc anode-based electrochromic devices and will inspire more efforts in designing novel multifunctional ECES devices.