Aqueous ammonium ion storage materials: A structure perspective

Aqueous ammonium ion energy storage devices have received widespread attention recently due to their high safety, fast diffusion kinetics, and unique tetrahedral structure with abundant charge carriers (NH4+) resources. Although many NH4+ storage electrode materials have been frequently proposed, there are still face explorations and challenges in terms of performance improvement and storage mechanisms. Therefore, there is an urgent need to develop high-performance NH4+ storage electrode materials and explore deeper mechanisms. This review comprehensively classifies and compares NH4+ storage electrode materials from a structural perspective, and reviews the influence of electrolyte composition and concentration on NH4+ storage systems. In addition, this review also elaborates on the current limitations and possible solutions. Finally, common NH4+ storage devices are summarized, and their future development prospects and challenges are discussed.