High-Capacity Electrochromic Battery Enabled by Inverted Fabry–Pérot Nanocavity

Electrochromic batteries, integrating electrochromic functionality with energy storage, have attracted significant attention for their ability to visualize charge status, enable energy reutilization, and support low-power color modulation. However, conventional materials often struggle to simultaneously achieve high-capacity storage and tunable multicolor display. Herein, we propose a multicolor electrochromic battery based on an inverted Fabry–Pérot cavity structure. This design innovatively integrates electrochromic functionality, structural color modulation, and energy storage capability within a single device. A porous poly(ether sulfone) (PES) membrane serves as a flexible electrode substrate, supporting a front-side W/WO 3 multilayer to form a resonant cavity, while the electrolyte and counter electrode are placed on the back. This configuration minimizes optical loss and enhances color saturation. Furthermore, an extra WO 3 layer is introduced between the PES membrane and the W reflector to increases active material loading without compromising the structural color fidelity. Consequently, the device achieves vivid, tunable multicolor display and delivers a high areal capacity of 534.3 mAh m –2 at a current density of 0.5 mA cm –2 . This work offers a novel structural design strategy for developing high-performance, multifunctional electrochromic batteries.