PEDOT:PSS/PVA Electrode for High‐Efficiency Multicolor Electrochromic Battery via Stable Polyiodide Deposition

Electrochromic batteries based on transition metal oxides (e.g., WO 3 , LTO, NiO) or metal electrodeposition show great promise in applications like smart windows and flexible electronics. However, transition metal oxide systems often involve complex fabrication, limited energy storage capability, and non‐neutral monochromatic coloration, whereas metal‐electrodeposition systems suffer from dendrite‐related reliability issues and irreversible energy dissipation. In this work, we develop a low‐cost multicolor electrochromic battery based on reversible polyiodide (I n − ) electrodeposition, using a solution‐processable cathode comprising poly(3,4‐ethylenedioxythiophene) (PEDOT) and polyvinyl alcohol (PVA). The conductive PEDOT matrix suppresses electrochemical polarization in I − /I n − redox, enabling a large areal capacity (8700 mAh m −2 at 0.25 mA cm −2 ), superior energy density (11 200 mWh m −2 at 3250 mW m −2 ), and high energy efficiency (92.7%), while the uniformly distributed PVA enhances the film stability. Furthermore, 1‐butyl‐3‐methylimidazolium methanesulfonate is added to inhibit the polyiodide shuttle effect, enabling the device to undergo 10 000 optical cycles with ∼100% optical retention. Critically, the intrinsic transparent‐to‐blue electrochromism of PEDOT synergizes with the color modulation (yellow‐to‐brown) enabled by controlling polyiodide deposition time, facilitating voltage/duration‐programmable multicolor states. Overall, this design addresses several limitations hindering the practical deployment of electrochromic devices, including low areal capacity and efficiency, poor cycling stability, monochromatic coloration, and costly fabrication.