Challenges for Developing Rechargeable Room‐Temperature Sodium Oxygen Batteries

Abstract

The development of high energy‐density and low‐cost energy storage devices requires new chemistry beyond the horizon of current state‐of‐the‐art lithium‐ion batteries. Recently, sodium/oxygen (Na/O2) batteries have attracted great attention as one possible battery type among the new generation of rechargeable batteries. They convince with superior energy density, a relatively simple cell reaction, and abundance of sodium. Research on Na/O2 batteries has progressed quickly in recent years. However, a fundamental understanding underpinning the complex chemical/electrochemical side reactions is still insufficient, and many challenges remain unsolved for real practical applications. Herein, recent achievements and remaining issues for the development of rechargeable Na/O2 batteries are summarized. The discussion focuses on cell reaction mechanisms as well as cathode materials, sodium anodes, and electrolytes as key components of this type of battery. Furthermore, perspectives for future research and technological advances of Na/O2 batteries are outlined.

Design Strategies to Enable the Efficient Use of Sodium Metal Anodes in High‐Energy Batteries

“…Various reaction intermediates or discharge products can be dissolved in the commonly used LE. These dissolved species, such as polysulfides in Na‐S batteries and superoxide in Na‐O 2 batteries, freely diffuse and migrate from one electrode to the other, allowing, what is known as “cross‐talk” between the electrodes (Figure ) . All‐solid‐state batteries with SEs would be the ideal solution to this problem since they immobilize any species except the intended metal ion to transport.…”

“…Inorganic SEs on the other hand exhibit high conductivity, high transference number, and very high mechanical strength, but many SE phases are chemically reduced by Na metal and degrade quickly. For a more comprehensive overview on SE materials, we refer the reader to recent literature …”

“…New types of rechargeable Na‐metal‐based batteries, such as RT sodium‐sulfur (Na‐S) batteries, RT sodium‐oxygen (Na‐O 2 ) batteries, and RT ZEBRA‐type sodium‐metal halide batteries, also exhibit potentials to develop high‐energy and low‐cost energy storage systems. However, there are still some key issues to be solved …”

Recent Development of Aprotic Na−O2 Batteries

“…However, owing to the high reactivity and dendrite formation, sodium metal may not be an ideal anode. The active dendrite of sodium can result not only in limited battery performance, but also potential hazard . Dendrites originate from inhomogeneous sodium deposition in charging processes.…”

“…Dendrite is one of the most serious problems of metallic anodes in alkali‐metal battery systems, such as Li−O 2 , Li−S, Na−O 2 , K−O 2 batteries etc . Dendrite formation limits the cycling performance of a Na−O 2 battery, which is commonly attributed to inhomogeneous deposition of sodium ions in the charging process.…”