Zwitterionic Engineering of Vinylene‐Linked Covalent Organic Frameworks for Superior Protonic Electrolytes

ABSTRACT Solid protonic electrolytes are a promising avenue for advanced solid‐state proton batteries, offering enhanced safety, long‐term cycling stability, and high energy density. However, achieving high proton conductivity under ambient conditions remains a formidable challenge. In this study, we demonstrate a highly robust zwitterionic vinylene‐linked covalent organic framework (COF) engineered with sulfobetaine functionalities that promote efficient proton dissociation and migration, enabling superior proton conduction under ambient conditions and setting a new benchmark in the COF field. The solid protonic electrolyte comprising phosphoric acid‐modified zwitterionic COFs achieved the highest proton conductivity (5.34 × 10 −2 S cm −1 ) under ambient conditions among all reported COF‐based protonic electrolytes, along with incredible long‐term stability. Furthermore, solid‐state proton batteries assembled using the solid electrolyte delivered a record‐high specific capacity (108.5 mAh g −1 at 1.0 A g −1 ), good cycling durability (90% capacity retention after 2000 charge‐discharge cycles at 1.0 A g −1 ), and excellent rate capability. This study presents a viable and effective strategy for constructing high‐performance COF‐based protonic electrolytes tailored for advanced solid‐state proton battery technologies.