A Long-Range Planar Polymer with Efficient π-Electron Delocalization for Superior Proton Storage.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Aqueous proton batteries (APBs) offer safe and sustainable energy storage, leveraging the Grotthus mechanism.
• Polymers are attractive electrode materials for APBs due to their tunable structures, but their proton-storage capabilities are often limited.
• Existing polymer electrodes face challenges with unsatisfactory redox behaviors, hindering practical APB applications.

Purpose of the Study:

• To synthesize and evaluate a novel planar phenazine (PPHZ) polymer as a high-performance electrode material for APBs.
• To investigate the structural and electronic properties of PPHZ that contribute to enhanced proton storage.
• To demonstrate the practical viability of PPHZ in APB devices with long-term stability.

Main Methods:

• Synthesis of a novel planar phenazine (PPHZ) polymer with an imine-rich skeleton.
• Electrochemical characterization of PPHZ as an electrode material in 1 M H2SO4 electrolyte.
• In situ techniques to study redox reversibility and proton dynamics.
• Theoretical calculations to elucidate protonation pathways.

Main Results:

• The PPHZ polymer exhibits ordered molecular stacking and optimized electronic properties due to its planar, conjugated structure.
• Achieved a high proton storage capacity of 273.3 mAh g⁻¹ at 0.5 A g⁻¹ (1 C), the highest reported for proton-inserted electrodes in acidic electrolytes.
• Demonstrated excellent redox reversibility and fast proton diffusion, confirmed by in situ studies and theoretical calculations.
• A pouch-type APB cell using PPHZ showed an ultralong lifespan exceeding 30,000 cycles.

Conclusions:

• The novel PPHZ polymer demonstrates superior proton-storage redox behaviors, making it a highly promising electrode material for APBs.
• The unique planar structure and electronic properties of PPHZ overcome limitations of previous polymer electrodes.
• PPHZ offers a viable pathway towards developing safe, sustainable, and long-lasting aqueous proton battery technologies.