Redox-active Hexaazatriphenylene@MXene composite for high-performance flexible proton batteries

Owing to the proton as charge carrier with the smallest ionic size and fastest kinetics, aqueous proton batteries (APBs) with high safety and low cost are of great promise as flexible energy storage devices for portable/ wearable electronics. Although Hexaazatrinaphthalene (HATN) is regarded as a potential organic electro-active material, the sluggish electron transfer and low tapped density of HATN seriously hinder its application as flexible electrode with high performance. Herein, we report a self-standing and binder-free HATN@MXene composite film electrode with high tapped density (~2.21 g cm(-3)) for flexible APBs. In such film electrode, the HATN nanowires are encapsulated between the MXene flakes to construct a 3D lamination-like robust and conductive network to facilitate the electron transmission. As a result, the HATN@MXene film electrode delivers superior proton storage behaviors with a specific capacity as high as 516.2 mAh cm(-3) (or 233.6 mA h g(-1)) in aqueous acidic electrolyte, while the reversible redox process upon proton uptake/removal is further revealed by in-situ Raman investigation. For real-life application, a high-performance flexible APB is assembled with high energy density (58.5 mWh cm(-3)) and long-term cycle performance upon the straight and bent states, suggesting its great potential for portable/wearable electronics.