Highly Proton-Conductive Solid-State Electrolyte Based on Covalent Organic Framework for Proton Battery Application

Solid-state proton batteries are emerging as promising technologies for energy storage. However, efficient solid-state protonic electrolyte development remains in its early stages. Herein, we report the preparation and potential application of a high-performance covalent organic framework (COF)-based protonic electrolyte for solid-state proton batteries. Using a mechanochemical method, H₃PO₄ was incorporated into the channels of a sulfonated COF (COF-SO₃H) to produce the composite solid-state electrolyte, H₃PO₄@COF-SO₃H. This composite was thoroughly characterized using techniques such as powder X-ray diffraction, ¹³C NMR spectroscopy, X-ray photoelectron spectroscopy, and nitrogen adsorption/desorption analysis. Impedance spectroscopy revealed that H₃PO₄@COF-SO₃H exhibited superprotonic conductivity exceeding 10^-2 S cm^-1 under ambient conditions, alongside remarkable long-term stability and a broad electrochemical stability window. A solid-state proton battery assembled using H₃PO₄@COF-SO₃H as the electrolyte demonstrated exceptional performance, including excellent rate capability, high specific capacity of 101.8 mAh g^-1 at 1.0 A g^-1, and good cycling stability with a capacity retention of 80.6% after 1000 cycles at 1.0 A g^-1, outperforming previously reported solid-state proton batteries. These findings suggest that COF-based composite solid-state electrolytes hold significant promise for future applications in solid-state proton batteries.