Critical Function of Organic Materials in Aqueous Ammonium-Ion Batteries

Aqueous ammonium-ion batteries (AAIBs) have attracted considerable interest as promising candidates for large-scale energy storage systems due to their low cost, intrinsic safety, and environmental friendliness. Distinct from conventional spherical metal ions, NH 4 + possesses a tetrahedral geometry and a strong tendency to form hydrogen bonds with surrounding species, which facilitates fast ion transport. At the same time, these features impose specific requirements on the chemical environments of the electrolyte, interface, and host frameworks. Although various inorganic materials have been explored for AAIBs, issues such as structural instability, dissolution, and limited cycling durability remain challenging, partly due to the fixed coordination environments of inorganic lattices. Organic materials offer distinct advantages arising from their molecular-level tunability, diverse functional groups, and flexible structural frameworks, enabling favorable interactions with NH 4 + through hydrogen bonding, coordination, and electronic delocalization. These features allow organic components to effectively regulate the thermodynamics and kinetics of ammonium-ion storage and transport. This review systematically examines the functional roles of organic materials in AAIBs, highlighting how molecular structures and interaction mechanisms translate into electrochemical performance, and summarizes recent advances in their applications as electrode materials, hybrid electrode architectures, and electrolyte components. Furthermore, the current challenges and future research directions are discussed to guide the development of high-performance AAIBs.