Flexible Zn-ion Electrochromic Batteries with Multiple-color Variations.

Electrochromic batteries as emerging smart energy devices are highly sought after owing to their real-time energy monitoring through visual color conversion. However, their large-scale applicability is hindered by insufficient capacity, inadequate cycling stability, and limited color variation. Herein, a flexible Zn-ion electrochromic battery (ZIEB) was assembled with sodium vanadate (VO) cathode, ion-redistributing hydrogel electrolyte, and Zn anode to address these challenges. The electrolyte contains anchored -SO and -NH , which facilitates ionic transportation and prevents Zn dendrite formation by promoting orientated Zn deposition on the Zn (002) surface. The ZIEB exhibits a continuous reversible color transition, ranging from fully charged orange to mid-charged brown and drained green. It also demonstrates a high specific capacity of 302.4 mAh ⋅ g at 0.05 A ⋅ g with a capacity retention of 96.3 % after 500 cycles at 3 A ⋅ g. Additionally, the ZIEB maintains stable energy output even under bending, rolling, knotting, and twisting. This work paves a new strategy for the design of smart energy devices in wearable electronics.