Ammonium Ion Batteries: Material, Electrochemistry and Strategy

Ammonium-ion batteries (AIBs) have recently attracted increasing attention in the field of aqueous batteries owing to their high safety and fast diffusion kinetics. The NH₄⁺ storage mechanism is quite different from that of spherical metal ions (e.g. Li⁺, Na⁺, K⁺, Mg²⁺, and Zn²⁺) because of the formation of hydrogen bonds between NH₄⁺ and host materials. Although many materials have been proposed as electrode materials for AIBs, their performances hardly meet the requirement of future electrochemical energy storage devices. It is thus urgent to design and exploit advanced materials for AIBs. This review highlights the state-of-the-art research on AIBs. The insights into the basic configuration, operating mechanism and recent progress of electrode materials and corresponding electrolytes for AIBs have been comprehensively outlined. The electrode materials are classified and compared according to different NH₄⁺ storage behaviour in the structure. The challenges, design strategies and perspectives are also discussed for the future development of AIBs.