Cationic Additive with a Rigid Solvation Shell for High-Performance Zinc Ion Batteries.

Despite substantial progresses, in aqueous zinc ion batteries (AZIBs), developing zinc metal anodes with long-term reliable cycling capabilities is nontrivial because of dendritic growth and related parasitic reactions on the zinc surface. Here, we exploit the tip-blocking effect of a scandium (Sc 3+ ) additive in the electrolyte to induce uniform zinc deposition. Additional to the tri-valency of Sc 3+ , the rigidity of its hydration shell effectively prevents zinc ions from concentrating at the surface tips, enabling highly stable cycling under challenging conditions. The shell rigidity, quantified by the rate constant of the exchange reaction (k ex ), is established as a key descriptor for evaluating the tip-blocking effect of redox-inactive cations, explaining inconsistent results when only the valence state is considered. Moreover, the tip-blocking effect of Sc 3+ is maintained in blends with organic solvents, allowing the zinc anode to cycle reliably even at -40 °C without corrosion.