Steering ion transport direction for thin-film electrochromic energy storage device

Abstract

Electrochemical devices are vital to modern technology, but their complex structures, essential for functions like the memory effect in electrochromic devices, hinder their advancement. Herein, through a systematic investigation of the interplay between the electric field direction and ion transport pathways, we develop a structural simplification strategy based on a coplanar interdigitated electrode configuration. This controlled directional transport significantly prolongs the diffusion time required for the self-erasing of redox-active species, enabling a single-layer electrochromic device to achieve the memory effect enhancement of about 600 times (from 7 s to 4160 s) and areal capacitance enhancement of up to 40 times (from 0.055 mF cm−2 to 2.2 mF cm−2) , the average transmittance of the device in its bleached state increased by 10%, while exhibiting excellent cycling stability (>5000 cycles). This design yields a soft, adhesive film that can be directly applied to various surfaces like marble, wood, plastic, ceramic, and cloth, facilitating easy integration into next-generation portable devices.