A π‐Bridge Spacer Embedded Electron Donor–Acceptor Polymer for Flexible Electrochromic Zn‐Ion Batteries

Abstract Zinc–ion batteries (ZIBs) have drawn much attention for next‐generation energy storage for smart and wearable electronics due to their high theoretical gravimetric/volumetric energy capacities, safety from explosive hazards, and cost‐effectiveness. However, current state‐of‐the‐art ZIBs lack the energy capacity necessary to facilitate smart functionalities for intelligent electronics. In this work, a “π‐bridge spacer”‐embedded electron donor–acceptor polymer cathode combined with a Zn²⁺–ion‐conducting electrolyte is proposed for a smart and flexible ZIB to provide high electrochromic–electrochemical performances. The π‐bridge spacer endows the polymeric skeleton with improved physical ion accessibility and sensitive charge transfer through the cycles, providing extremely stable cyclability with high specific capacity (110 mAh g⁻¹) at very fast rates (8 A g⁻¹) and large coloration efficiency (79.8 cm² C⁻¹) under severe mechanical deformation over a long period. These results are markedly outstanding compared to the topological analogue without the π‐bridge spacer (80 mAh g⁻¹ at current density of 8 A g⁻¹, 63.0 cm² C⁻¹). The design to incorporate a π‐bridge spacer realizes notable electrochromism behaviors and high electrochemical performance, which sheds light on the rational development of multifunctional flexible‐ZIBs with color visualization properties for widespread usage in powering smart electronics.