Bifunctional Oxygen Electrocatalysts for Lithium−Oxygen Batteries

Abstract

LithiumÀoxygen batteries have attracted great attention over the last few decades owing to their extraordinarily high theoretical energy density, which can potentially exceed that of current state-of-art lithium-ion batteries. However, lithiumÀoxygen batteries exhibit poor cycle stability, relatively low power capability and significantly large polarizations for both, the oxygen reduction reaction (ORR, discharge) and the oxygen evolution reaction (OER, charge). To address these issues, various catalysts for aqueous and non-aqueous lithiumÀoxygen batteries have thus been introduced, and some recent developments of bifunctional catalysts could simultaneously facilitate the ORR and OER, leading to great advance-ments in the overall battery performance. Herein, we present a brief overview of recent progress in the development of bifunctional catalysts for lithiumÀoxygen batteries based on the current understanding of their working mechanism. Perovskitetype, spinel-type, and non-oxide catalysts and their use in aqueous lithiumÀoxygen batteries are reviewed. Recently reported bifunctional catalysts in non-aqueous lithiumÀoxygen batteries are also introduced, and the different roles of solidand soluble-type catalysts are further discussed. Finally, we conclude by deliberating the design prospects and perspectives for efficient bifunctional catalysts for future lithiumÀoxygen batteries.

Flexible and Wearable Power Sources for Next‐Generation Wearable Electronics

“…On the one hand, the operation of rechargeable metalÀ air batteries bases on oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which require the utilization of electrocatalyst on the air cathode. [114][115][116][117][118][119][120][121][122] On the other hand, the half-opened battery structure pose challenges to the electrolyte materials for metalÀ air batteries.…”

“…One of the greatest challenges of metal−air batteries is the semi‐open battery configuration which should be particularly paid attention in wearable power supplies. On the one hand, the operation of rechargeable metal−air batteries bases on oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), which require the utilization of electrocatalyst on the air cathode [114–122] . On the other hand, the half‐opened battery structure pose challenges to the electrolyte materials for metal−air batteries.…”

Electrochemistry: Retrospect and Prospects

“…[135] Let it be mentioned in passing that the ORR in organic solvents takes different pathways and thus remain an obstacle to the realization of LiÀ air batteries, in which there is a shift in emphasis to soluble catalysts such as oxygen species carrier and redox mediators. [140] Electrocatalysts Electrocatalysis is at the heart of electrolyzers and fuel cells, where platinum and platinum group metals are dominant, limiting large-scale deployment of these technologies. Studies indicate that polarization in these systems arise from a surface oxide on platinum.…”

“…For example, N‐Co 9 S 8 /G shows better dual activity than do NG, Co 9 S 8 and N‐Co 9 S 8 [135] . Let it be mentioned in passing that the ORR in organic solvents takes different pathways and thus remain an obstacle to the realization of Li−air batteries, in which there is a shift in emphasis to soluble catalysts such as oxygen species carrier and redox mediators [140] …”

Dual‐Functioning Molecular Carrier of Superoxide Radicals for Stable and Efficient Lithium–Oxygen Batteries

“…It should also be noted that it is not clearly understood whether or to what extent ORR mediators suppress the reactivity of radicals, with most of the previous investigations focused on promoting the solution-mediated discharge process in Li-O 2 chemistry. [37][38][39][40][41][42][43][44][45] Moreover, the reduction potentials of ORR redox mediators are generally similar to that of oxygen; thus, it would be difficult to completely suppress the production of some amount of oxygen radicals at the discharge potential in an electrochemical system, which would continuously degrade the cells in every discharge cycle. In contrast, directly regulating the oxygen radicals would block many potential routes of the side reactions.…”