Zachary Paul Cano

Electrically Rechargeable Zinc–Air Batteries: Progress, Challenges, and Perspectives

Zinc-air batteries have attracted much attention and received revived research efforts recently due to their high energy density, which makes them a promising candidate for emerging mobile and electronic applications. Besides their high energy density, they also demonstrate other desirable characteristics, such as abundant raw materials, environmental friendliness, safety, and low cost. Here, the reaction mechanism of electrically rechargeable zinc-air batteries is discussed, different battery configurations are compared, and an in depth discussion is offered of the major issues that affect individual cellular components, along with respective strategies to alleviate these issues to enhance battery performance. Additionally, a section dedicated to battery-testing techniques and corresponding recommendations for best practices are included. Finally, a general perspective on the current limitations, recent application-targeted developments, and recommended future research directions to prolong the lifespan of electrically rechargeable zinc-air batteries is provided.

Recent progress and perspectives on bi-functional oxygen electrocatalysts for advanced rechargeable metal–air batteries

With continued dependence on carbon-based fuels and rising concerns of environmental issues, the development of rechargeable metal–air batteries has recently gained tremendous attention. However, due to the slow kinetics of electrochemical oxygen reactions, the charge and discharge processes of a rechargeable metal–air battery must be catalyzed by using bi-functional catalysts that are active towards both the oxygen reduction and oxygen evolution reactions. This review focuses on recent developments in bi-functional catalysts and their catalytic activity in relation to materials composition, morphology, and crystal structure obtained through various synthetic techniques. The discussion is divided into sections based on the main types of recent bi-functional catalysts such as transition metal- and carbon-based materials, and hybrids which consist of the two. The subsections are then divided based on the metal substituents, types of dopant, degree of doping, and defect densities, discussing the effects of composition. In parallel, morphological effects on the catalytic activity, such as unique nanostructured design, surface area enhancements, and porosity, are also discussed. Currently, bi-functional oxygen electrocatalyst research is heading in the direction of reducing the loading of precious metals, and developing cost-competitive non-precious metal- and carbon-based catalysts to enable commercialization of rechargeable metal–air batteries for various applications including electric-drive vehicles and smart-grid energy storage. To understand the origin of bi-functional catalytic activity, future catalyst research should be conducted in combination with in situ characterizations, and computational studies, which will allow exploitation of active sites to maximize the efficacy of bi-functional catalysts.

3D Ordered Mesoporous Bifunctional Oxygen Catalyst for Electrically Rechargeable Zinc-Air Batteries.

To enhance energy efficiency and durability, a highly active and durable 3D ordered mesoporous cobalt oxide framework has been developed for rechargeable zinc-air batteries. The bifunctional air electrode consisting of 3DOM Co3 O4 having high active surface area and robust structure, results in superior charge and discharge battery voltages, and durable performance for electrically rechargeable zinc-air batteries.

Hierarchical Core–Shell Nickel Cobaltite Chestnut-like Structures as Bifunctional Electrocatalyst for Rechargeable Metal–Air Batteries

Nano-engineered hierarchical core-shell nickel cobaltite chestnut-like structures were successfully synthesized as a bifunctionally active electrocatalyst for rechargeable metal-air battery applications. Both the morphology and composition of the catalyst were optimized by a facile hydrothermal reaction, resulting in a 10 h reacted sample demonstrating significantly enhanced activity toward both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in 0.1 m KOH. Specifically, the catalyst demonstrated -0.28 and 0.60 V versus SCE (saturated calomel electrode) at the ORR half-wave potential and an OER current density of 10 mA cm-2 , respectively. The resulting ORR/OER potential difference of 0.90 V was the smallest compared to the catalysts synthesized using 2, 6, and 12 h of hydrothermal reaction time. The excellent bifunctional activity of the catalyst is attributed to the nanoscale porous morphology and the spinel nickel cobaltite composition, which improved the active site exposure and transport of reactants and charges during the oxygen reactions.