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

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Solid-state proton batteries offer enhanced safety and energy density compared to traditional batteries.
• High proton conductivity in solid electrolytes under ambient conditions is crucial for practical applications but remains a significant challenge.

Purpose of the Study:

• To engineer a robust zwitterionic covalent organic framework (COF) with sulfobetaine functionalities for high-performance solid protonic electrolytes.
• To investigate the proton conductivity, stability, and battery performance of the developed COF-based electrolyte.

Main Methods:

• Synthesis of a zwitterionic vinylene-linked COF functionalized with sulfobetaine groups.
• Modification of the COF with phosphoric acid to enhance proton conduction.
• Fabrication and testing of solid-state proton batteries using the developed electrolyte.

Main Results:

• The phosphoric acid-modified zwitterionic COF achieved a record proton conductivity of 5.34 × 10⁻² S cm⁻¹ under ambient conditions, surpassing all previously reported COF-based protonic electrolytes.
• The solid electrolyte demonstrated exceptional long-term cycling stability.
• Solid-state proton batteries exhibited a high specific capacity (108.5 mAh g⁻¹ at 1.0 A g⁻¹), excellent cycling durability (90% retention after 2000 cycles), and superior rate capability.

Conclusions:

• The developed zwitterionic COF represents a significant advancement in COF-based protonic electrolytes, setting a new benchmark for proton conductivity.
• This material offers a viable and effective strategy for constructing high-performance solid-state proton batteries with improved safety and energy density.