Strategic Enhancement of Ionic and Electronic Conductivities in Organic Frameworks for Efficient Energy Storage Devices

Abstract

The escalating demand for energy has underscored the need for efficient and affordable charge storage devices. Zinc–air batteries (ZABs) have garnered significant attention due to their high energy density, cost-effectiveness, and safety. To enhance ZAB performance, advancements in electrodes and separators are crucial. Hydroxide ion transport in the electrolyte plays a pivotal role in ZAB efficiency. Liquid-based electrolytes pose challenges in fabrication, handling, and cycle life, while solid-state electrolytes offer advantages in safety and ease of use. Developing ZABs with flexible, high-performance quasi solid-state separators holds promise for diverse applications. In this work, we present a novel approach to design and implement hydroxide ion-conducting viologen-resorcinol-based polymeric organic frameworks (POFs) as solid-state separators-cum-electrolytes for zinc-air batteries (ZABs). The viologen-based quaternary center in IISERP-POF11_OH is counterbalanced by a larger anion (Br−), facilitating easy exchange with OH− ions. The resulting solid-state separator demonstrates enhanced suitability for energy applications, especially in zinc-air batteries (ZABs). The amorphous nature, low electronic conductivity, and microporous structure of the POFs minimize zinc-dendrite formation, ensuring selective conduction of hydroxide ions. The solid electrolyte adheres to the electrode, accommodating volume changes during charging and discharging. Furthermore, we explore the systematic tuning of the monomeric building units to increase the number of hydroxide ions per unit cell i.e. IISERP-POF12_OH and IISERP-POF13_OH, resulting in enhanced hydroxide ion conductivity. The demonstrated high-power density and extended running life of the viologen-bakelite electrolyte-based rechargeable zinc-air battery showcase the potential of this strategy, opening up new possibilities for advanced energy storage systems. This research contributes to the ongoing development of sustainable and efficient battery technologies with broad applications in energy storage, catalysis, and anion exchange. Additionally, the work explores the use of a polyimide based Covalent Organic Framework (COF) modified with polypyrrole for energy storage applications. The COF–electrode–electrolyte system operates at a high voltage regime, showcasing increased energy and power densities. The incorporation of polypyrrole within the COF's nanochannels enhances electronic conductivity and charge storage, making the composite a promising candidate for all-solid-state capacitors. The study emphasizes the potential of these innovative frameworks for various electrochemical applications, highlighting their unique features and contributions to the field of energy storage.