Flexible large-area electrochromic devices with enhanced cycling stability enabled by Ni/MnO2 hybrid mesh electrodes

Abstract

The realization of large-area, high-performance flexible electrochromic devices (FECD) faces significant hurdles, primarily stemming from conductivity limitations in flexible transparent electrodes (FTEs) governing electrochromic uniformity and cycling instability caused by "ion trapping" phenomena and electron/ion conductivity mismatches. Here, we introduce a novel device architecture and fabrication strategy to overcome these challenges. An embedded micrometer-scale nickel (Ni) mesh electrode was firstly introduced and then manganese dioxide (MnO2) was precisely deposited onto the Ni surface. This innovation not only ensures high optical transparency but also facilitates efficient ions and electrons transport by balancing charge capacities between MnO2 and tungsten oxide (WO3) films that significantly enhance device cycling stability. We also demonstrate an 8×8 cm2 flexible electrochromic device based on this Ni/MnO2 hybrid electrode architecture, achieving an optical modulation range of 64%, coloration/bleaching times of 6 s /8 s, and a coloring efficiency of 153.81 cm2 C-1. The device exhibits exceptional cycling stability (retaining 99% of its optical modulation after 150 cycles) and outstanding flexibility (displaying only 6% modulation loss after 300 bending cycles at 60° curvature). We believe that our FECDs would accelerate the development of large-area patterned flexible displays and wearable electronics.