Challenges and opportunities in 2D materials for high-performance aqueous ammonium ion batteries

Abstract Aqueous ammonium ion batteries (AAIBs) have attracted considerable attention due to their high safety and rapid diffusion kinetics. Unlike spherical metal ions, NH4+ forms hydrogen bonds with host materials, leading to a unique storage mechanism. Despite the variety of proposed electrode materials for AAIBs, their performance often falls short for future energy storage needs. Hence, there is a critical need to design and develop advanced electrode materials for AAIBs. Two-dimensional (2D) materials, with their tunable interlayer spacing, remarkable interfacial chemistry, and abundant surface functional groups, are an ideal choice of electrode materials for NH4+ storage. This review highlights the latest research on 2D electrode materials for AAIBs, providing insights into their working principles, NH4+ storage mechanisms, and control strategies for designing high-performance AAIBs. Furthermore, summary and future perspectives of 2D electrode materials in the development of AAIBs are provided, aiming to promote the advancement of high-performance AAIBs.