The electrochemical reversibility of the aluminum–sulfur (Al–S) battery critically depends on the physical and chemical properties of the sulfur cathode.

Post-Li ion battery technologies are gaining importance due to their high theoretical energy density and high specific capacity of the electrode materials.Due to fundamental limitations, the existing Li-ion batteries cannot fulfill rigorous requirements, like cost-effectiveness and high storage capacities. Roomtemperature sodium-sulfur battery (RT-Na/S), in particular, is an emerging candidate with the high theoretical specific capacity of sodium (~1166 mAh/g) and sulfur (~1675 mAh/g) and naturally high abundance of both the electrode materials. Sodium metal, combined with sulfur, is a cheap and energy-dense option to the existing battery technologies. In recent years, this has garnered much interest in the scientific community due to a wide range of possibilities for altering battery performance. With the invention of the high-temperature sodium-sulfur batteries, Na metal-based chemistries remain in oblivion.However, due to increasing concerns over the safety of high-temperature sodium-sulfur batteries, Na metal anode is revived in recent years with the ever-growing demands for high energy density and improved safety. Despite that current Na metal anode still lacks high-reversibility, efficiency, and roomtemperature stability due to limited or no control over the interfacial chemistry of the Na metal anode. The electrochemical reduction of Na + ions is accompanied by the inevitable reduction of organic species, which leads to the growth of the solid-electrolyte interphase (SEI) with Na-deposits. The SEI is inherently unstable due to the localized fluctuations in its chemical and physical properties. A deep understanding of challenges associated with the SEI's localized interfacial chemistry is of prime importance toward developing practical Na metal anodes for RT-Na/S batteries. This minireview highlights critical challenges in developing a stable Na metal anode and further sheds light on its mechanistic aspects. In addition to that, novel approaches to precisely tune the interphase's physicochemical properties are highlighted to pave path for developing a stable and long-life Na-metal anode for RT-Na/S batteries.

Solid electrolytes for room-temperature sodium–sulfur batteries have gained acceptance considering the advantages of safety, mitigating the polysulfide shuttling, stable cycling and mechanical property, which suppresses dendrite proliferation.

The physiochemical aspects of the matrix play an important role in deciding the loading of sulfur cathodes.

The increased demand for energy has prompted users to seek alternative energy storage devices. Post‐Li‐ion battery chemistries have been considered potential contenders for the development of next‐generation battery technologies. The high specific capacity (≈1675 mAh g−1) and high natural abundance (≈953 ppm) of sulfur provide opportunities to meet the rigorous requirements of the market's demands, such as high energy density and low cost. When combined with a high capacity metal anode (e.g., Na ≈ 1165 mAh g−1, Mg ≈ 2205 mAh g−1, and Al ≈2980 mAh g−1), it leads to high energy density that can outperform the existing battery technologies, including high‐energy Li‐ion batteries. Despite the unique attributes of the sulfur‐based battery system, it remains in infancy owing to the complex reaction chemistry of sulfur cathode, and the level of complexity increases with an increase in valency of metal ions. This review summarizes the unique aspects of a sulfur cathode essential to stabilizing sulfur cathode‐based high‐energy rechargeable batteries. Furthermore, deeper insight into the electrochemical performance of various metal–sulfur‐based systems has been provided. This review may pave the path for the researchers to accelerate the development of sulfur cathode for post‐Li‐ion batteries.