Covalent-Organic Framework with Superior Proton Conduction for Solid-State Proton Battery Application

Solid-state proton batteries hold great promise as a technology for portable energy storage. However, their development is impeded by the scarcity of suitable solid proton electrolytes. In this study, we present the first demonstration of covalent-organic frameworks (COFs) exploited as solid proton electrolytes with promising application in solid-state proton batteries. Specifically, the methanesulfonic acid (MeSA) molecules were confined and stabilized within the channels of a polybenzimidazole COF (PBI-COF) to yield the solid proton electrolyte, termed MeSA@PBI-COF. MeSA@PBI-COF exhibits a wide electrochemical stability window and superior proton conduction (>10–2 S cm–1) under ambient conditions, along with good long-term stability. Furthermore, MeSA@PBI-COF was employed as the solid proton electrolyte to assemble solid-state proton batteries, which demonstrate excellent cycle stability with a capacity retention of 74.2% after 8000 cycles at 1.0 A g–1 and deliver a high specific capacity of 49.8 mAh g–1 at 1.0 A g–1, outperforming the reported solid-state proton batteries.