Advanced Reversible Long-Lasting Flexible Metal-Air Batteries Using Mn/Fe Hexaiminobenzene Metal-Organic Frameworks

Fast growing “Internet of Things” has an ever-increasing demand for advanced batteries with high energy density, robustness, flexibility, and environmental benignity for emerging high-tech electronic technologies, electric vehicles, and smart grids. Herein, we demonstrate robust aqueous and flexible ZABs employing three-dimensional dual-linked hexaiminobenzene metal-organic frameworks (Mn/Fe-HIB-MOF) as redox-active robust bifunctional electrocatalysts with ultrahigh intrinsic electrical conductivity and atomically tuned multi-shelled hollow spheres. Superionic functionalized bio-cellulose nanofibrous, solid-state membrane electrolyte (64 mS∙cm−1) is also presented with outstanding flexibility and water retention. The well-defined quintet-shelled hollow sphere MOFs possess a hierarchical porous structure, excellent packing density with a surface area of (2,298 m2.g-1), and chemical stability contrasted to conventional MOFs. The Mn/Fe-HIB-MOFs exhibited superior bifunctional oxygen electrocatalytic activity (0.627 V) with half-wave potential (0.883 V) for oxygen reduction and overpotential (280 mV @10 mA∙cm−2) for oxygen evolution reactions, outperforming commercial Pt/C and RuO2. The liquid and flexible ZABs with the present constituents revealed the world-record breaking cycling stability of 1,000 h (6,000 cycles) and 600 h (3,600 cycles) with fast fading and exceptionally high rate capacity (10 and 25 mA cm- 2), respectively, reported to date for rechargeable ZABs. These promising results illustrate great perspectives for sustainable rechargeable ZABs in the modern industries of electric vehicles and wearable electronics.