Recent advances in cathode engineering to enable reversible room-temperature aluminium-sulfur batteries

The rigorous requirements, such as high abundance, cost-effectiveness, and increased storage capacities, pose severe challenges to the existing Li-ion batteries' long-term sustainability. Room-temperature aluminum-sulfur (Al-S) chemistry, in particular, is gaining importance due to its high theoretical energy density (1700 W h kg^-1). Al-S battery technology is one of the emerging metal-sulfur candidates that can surpass current Li-ion chemistries. When coupled with sulfur, aluminum metal brings a cheap and energy-rich option to existing battery technologies. Owing to the unique virtues of the Al-S battery, it has garnered increasing interest among scientific communities. Al-S chemistry has been investigated for quite some time, yet the cell performance remained in its infancy, which poses a challenge to this technology's viability. Besides stabilizing the Al metal anode, the most important challenge in the practical development of Al-S batteries is the development of a suitable sulfur cathode material. Owing to the complexity of this multivalent system, numerous factors have been taken into account, but the best sulfur cathode is yet to be identified. A detailed exploration of sulfur cathodes and their implications on the battery performance are discussed in this mini-review article. We present a detailed picture of cathode materials that may serve as the reference guide for developing more practical cathode materials. Also, fundamental principles and challenges encountered in the development of the sulfur cathodes are highlighted. Through the knowledge disseminated in this mini-review, the development in the multivalent post-Li-ion battery can be accelerated. A glimpse of the future outlook on the Al-S battery system with different potential solutions is also discussed.