Abstract
In recent years, there has been an upsurge in the study of novel and alternative energy storage devices beyond lithium‐based systems due to the exponential increase in price of lithium. Sodium (Na) metal‐based batteries can be a possible alternative to lithium‐based batteries due to the similar electrochemical voltage of Na and Li together with the thousand times higher natural abundance of Na compared to Li. Though two different kinds of Na–O2 batteries have been studied specifically based on electrolytes until now, very recently, a hybrid Na–air cell has shown distinctive advantage over nonaqueous cell systems. Hybrid Na–air batteries provide a fundamental advantage due to the formation of highly soluble discharge product (sodium hydroxide) which leads to low overpotentials for charge and discharge processes, high electrical energy efficiency, and good cyclic stability. Herein, the current status and challenges associated with hybrid Na–air batteries are reported. Also, a brief description of nonaqueous Na–O2 batteries and its close competition with hybrid Na–air batteries are provided.
Highlights
In recent years, there has been an upsurge in the study of novel and alterelectricity platform
Ductivity in aprotic electrolytes and poor safety may cause problems for its large-scale utilization. Those drawbacks motivate researchers to find new energy storage technologies alternative to lithium-ion batteries (LIBs) the current status and challenges associated with hybrid NA from sodium (Na)–air batteries are among which rechargeable metal–air batreported
As described in this progress report, there is a strong competition between the two key sodium battery technologies: nonaqueous Na–O2 and hybrid Na–air batteries
Summary
Mainly two different types of sodium metalbased air battery systems have been studied, namely, nonaqueous (often termed as Na–O2 battery) and hybrid batteries (often termed as Na–air battery). In nonaqueous Na– O2 battery usually pure oxygen is supplied whereas in hybrid cells, air works as oxygen source. A typical, nonaqueous Na–O2 battery is built up by the combination of metallic sodium as negative electrode and highly porous electrode as gas diffusion electrode (commonly known as electrocatalyst or air cathode).[6c] These two electrodes are separated by polymeric separator and immersed in an organic electrolyte (Figure 2a). The demonstrated configuration includes a Na-ion conducting solid electrolyte membrane which separates the negative compartment to positive compartment having different electrolytes (Figure 2b). The negative compartment design is the same as in conventional Na–O2 batteries whereas, the positive electrode is inserted in aqueous electrolyte. The energy storage mechanism in both cells involves the dissolution and plating of sodium metal at negative electrode during discharge and charge processes, respectively. On positive electrode ORR and oxygen evolution reaction (OER) takes place, when discharge and charge the cells
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