Aqueous aluminum ion system: A future of sustainable energy storage device

The world is predicted to face a lack of lithium supply by 2030 due to the ever-increasing demand in energy consumption, which creates the urgency to develop a more sustainable post-lithium energy storage technology. An alternative battery system that uses Earth-abundant metals, such as an aqueous aluminum ion battery (AAIB), is one of the most promising post-lithium battery technologies not only because of its safety and sustainability but also because of their high theoretical energy density in addition to their natural abundance in the Earth's crust. However, the commercialization of AAIB is confronted with many challenges as the three-electron transfer reactions of Al³⁺/Al are difficult to realize, and its charge transfer mechanism is still controversial. Delicate engineering of every battery part, from cathode, anode, and electrolyte, must be done simultaneously and carefully to realize these systems to meet the requirements of real-life applications. This review discusses the recent advancements in various AAIB designs where different approaches were carried out to realize the trivalent Al-ion transfer. Advanced battery systems with added functionalities in the context of AAIB, such as electrochromic, paper-based, wearable, and biobattery, will also be discussed. As a secondary energy device option, developments in the Al-ion supercapacitors are also highlighted. Finally, the review highlights the challenges and prospects for further research in this growing field.