Toward Safe and Reliable Aqueous Ammonium Ion Energy Storage Systems

Aqueous batteries using non-metallic charge carriers like proton (H+) and ammonium (NH4+) ions are becoming more popular compared to traditional metal-ion batteries, owing to their enhanced safety, high performance, and sustainability (they are ecofriendly and derived from abundant resources). Ammonium ion energy storage systems (AIBs), which use NH4+ ions with tetrahedral geometry, a small hydrated ionic radius, and relatively low ionic weight, are emerging as strong candidates in non-metal ion battery chemistry. Various electrode materials (both inorganic and organic) are investigated as hosts for NH4+ ions, however, a comprehensive understanding of these mechanisms is still lacking. This gap limits the ability to optimize performance and identify further research opportunities in AIBs. In this review, the charge storage mechanisms in AIBs are discussed, offering insights into the interactions between NH4+ ions and different electrode materials. Additionally, existing literature on electrode materials, highlighting key structural, and electrochemical achievements are summarized. The review also outlines various electrolytes and examines how their properties influence AIB performance. Finally, the shortcomings of current research are discussed and potential solutions are suggested to advance AIB technology, with the goal of inspiring researchers to explore real-world applications for ammonium ion batteries. The article focuses on the ammonium ion energy storage with a discussion on the charge storage mechanism of the ammonium ion in different host materials. Further, the performance of the electrode materials and the electrolytes that are used in the application of ammonium ion energy storage is elucidated. image