A Long-Range Planar Polymer with Efficient π-Electron Delocalization for Superior Proton Storage
Abstract
Due to the unique Grotthus mechanism, aqueous proton batteries (APBs) are promising energy devices with intrinsic safety and sustainability. Although polymers with tunable molecular structures are ideal electrode materials, their unsatisfactory proton-storage redox behaviors hinder the practical application in APB devices. Herein, a novel planar phenazine (PPHZ) polymer with a robust and extended imine-rich skeleton is synthesized and used for APB application for the first time. The long-range planar configuration achieves ordered molecular stacking and reduced conformational disorder, while the high conjugation with strong pi-electron delocalization optimizes energy bandgap and electronic properties, enabling the polymer with low proton diffusion barriers, high redox activity, and superior electron affinity. As such, the PPHZ polymer as an electrode material exhibits fast, stable, and unrivaled proton-storage redox behaviors with a large capacity of 273.3 mAh g-1 at 0.5 A g-1 (1 C) in 1 M H2SO4 electrolyte, which is the highest value among proton-inserted electrodes in aqueous acidic electrolytes. Dynamic in situ techniques confirm the high redox reversibility upon proton uptake/removal, and the corresponding protonation pathways are elucidated by theoretical calculations. Moreover, a pouch-type APB cell using PPHZ electrode exhibits an ultralong lifespan over 30 000 cycles, further verifying its promising application prospect. A novel polymer material with a planar imine-rich configuration is developed, in which the overall molecular rigidity, efficient pi-electron delocalization, and optimized electronic structure endow the polymer material with a rapid, ultra-stable and unrivaled proton-storage capability. For real applications, an all-organic aqueous proton battery (APB) is constructed with high energy/power density and an ultralong lifespan of over 30 000 cycles. image
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