Recent advances and perspectives of electrode materials for emerging ammonium-ion storage: From mechanistic insights to practical applications

The aggravation of energy and environmental issues forces people to develop sustainable energy storage technologies. In recent years, emerging ammonium-ion storage has been considered a promising energy storage competitor because of NH4+ ions as charge carriers with merits of abundant resources, inherent safety, fast diffusion capability and unique storage mechanism. However, the development of NH4-ion storage devices is still in the initial stage, and finding appropriate electrode materials is one of the most important tasks for fabricating high-performance devices. This article provides a comprehensive review on recent advances of electrode materials for emerging NH4-ion storage devices. Firstly, the ammonium-ion batteries (AIBs) are briefly summarized, and then the cathode materials, anode materials and their NH4-ion storage mechanism based on hydrogen bond are introduced. Furthermore, other NH4-ion storage devices, including NH4-ion supercapacitors (NH4+-SCs), NH4ion capacitors (AICs), ammonium dual-ion batteries (ADIBs) and ammonium-zinc hybrid batteries (AHBs), are also briefly introduced. Finally, a short conclusion and our perspectives on future developments for NH4-ion storage device's electrodes are provided in order to promote their large-scale energy storage applications.