Ion-confinement effect for zinc anode of aqueous zinc ion batteries

Aqueous zinc ion batteries are anticipated to succeed lithium-ion batteries as the upcoming generation of eco-friendly energy storage systems due to their high safety profile and environmental friendliness. Nevertheless, the development of aqueous zinc ion batteries has been impeded by obstacles such as Zn dendrites, hydrogen evolution reaction, corrosion, and passivation of the Zn anode. Researchers have used various strategies to address the problems faced by Zn anodes, including the construction of artificial interface protection layers, development of functional separators, optimisation of electrolyte additives, and zinc alloying. Among them, an idea called ion-confinement effect can be easily extracted from them. With the ion-confinement effect, the passage of zinc ions through the specific structure of the material can be regulated, resulting in uniform zinc ion flux and a dendrite-free anode. This review systematically summarises the application of ion-confinement effect in the construction of artificial interface coatings and functional separators, and then discusses in detail the mechanism of ion-confinement effect in various materials, including carbon materials, inorganic materials, 3-dimensional framework materials, biomass-based materials and polymers. Finally, an outlook on the development of ion-confinement interaction is given.