Designing single-ion conductive electrolytes for aqueous zinc batteries

Rechargeable aqueous zinc batteries (AZBs) suffer from rampant Zn dendrites and detrimental parasite hydrogen evolution corrosion, which impede the broad implementation of AZBs. To address these issues, it is imperative and significant to engineer the aqueous electrolytes to render single-ion conduction. The key aim for single-ion conductive electrolytes (SICEs) is to improve the cation transference number (t) with minimum sacrifice of ionic conductivity (σ). SICEs render the opportunity to effectively mitigate dendrite formation by minimizing ion concentration gradients and concurrently suppressing the loose deprotonated oxide species passivation through the restrained mobility of anions. This perspective encapsulates the fundamental principles and recent progress of SICEs. We suggest ideas for breaking the trade-off between t and σ under lean-water conditions. The testing methods for zinc ion transference numbers are also critically discussed. The primary objective of this perspective is to shed light on further development of SICEs to foster the energy density and lifespan of AZBs.