Room-temperature Na-metal-based rechargeable batteries, including Na-O2 and Na-S systems, have attracted attention due to their high energy density and the abundance of sodium resources. Although these systems show considerable promise, concerns regarding the use of Na metal should be addressed for their success. Here, we report dendrite-free Na-metal electrode for a Na rechargeable battery, engineered by employing nonflammable and highly Na(+)-conductive NaAlCl4·2SO2 inorganic electrolyte, as a result, showing superior electrochemical performances to those in conventional organic electrolytes. We have achieved a hard-to-acquire combination of nondendritic Na electrodeposition and highly stable solid electrolyte interphase at the Na-metal electrode, enabled by inducing polygonal growth of Na deposit using a highly concentrated Na(+)-conducting inorganic electrolyte and also creating highly dense passivation film mainly composed of NaCl on the surface of Na-metal electrode. These results are highly encouraging in the development of room-temperature Na rechargeable battery and provide another strategy for highly reliable Na-metal-based rechargeable batteries.

Sodium rechargeable batteries have garnered intensive attention as alternatives to currently used lithium‐ion batteries (LIBs). Among various sodium secondary batteries, a rechargeable Na–SO2 battery deserves to be regarded as one of the most promising sodium battery systems because of its high energy density and safety. Here we report the enhanced rate performance of Na–SO2 battery by introduction of meso/macropores in the carbon electrode using urea as a pore‐forming agent. The resulting meso/macroporous carbon electrode leads to much improved rate capability and structural stability of the electrode in a Na–SO2 battery against mechanical stress/strains induced by the formation of large size insulting discharge product (NaCl). We firmly believe that the urea‐based cost‐effective and scalable process for a meso/macroporous electrode would be one of the most practical ways to improve the performance of Na–SO2 battery to be a candidate for post‐LIB systems.

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