Robust Cu-Au alloy nanowires flexible transparent electrode for asymmetric electrochromic energy storage device

Abstract Flexible electrochromic energy storage (EES) systems have attracted tremendous attention because of their combined advantages of color-changing and energy-storing. Although copper nanowires (Cu NWs) flexible transparent electrodes (FTEs) have been considered as one of the most promising candidates for next-generation flexible electronics, its instinct electrochemical instability hindered its application in flexible electrochemical energy system, including EES device. Herein, we proposed a highly conductive electrochemically stable FTE based on Cu-Au alloy NWs network synthesized in a facile and simple electrochemical method. Compared with the pristine Cu NWs network that breaks into disconnected nanorods less than 10 s in 1 M H2SO4 solution during electrochemical anodic corrosion, the Cu-Au NWs network remained stable after 4000 s under the same condition. Furthermore, thanks to the forming of firm joints between the stacked NWs during inducting Au atoms, the optical-electrical performance (a sheet resistance of 23.2 Ohm/sq at a transmittance of 87%) and mechanical flexibility were highly improved. Based on these improvements, anodic PANI and cathodic WO3 layer were successfully deposited onto the Cu-Au NWs FTE by electrochemical method. An asymmetric-EES (AEES) device was assembled utilizing these complementary electrodes, which concurrently exhibited excellent electrochromic (coloration efficiency: 153.77 cm2/C at 633 nm) and energy storage performance (areal capacitance: 2.29 mF/cm2), demonstrating their potential for smart multifunctional flexible electronics.