A Guest Cation Screening Principle for Enabling Customized Cathode/Electrolyte Interface Chemistry and Self‐Enhanced Aqueous Zinc‐Ion Batteries

Abstract

Intrinsic structural instability and sluggish reaction kinetics at the electrode‐electrolyte interface are two critical concerns that block the application of MnO2 cathode in high‐performance aqueous zinc‐ion batteries. This work proposes a theoretical screening principle to select the compatible guest cation for MnO2 host, not only to strengthen the structure but also customize high‐efficiency cathode‐electrolyte interphase (CEI). As identified, Sr2+ is selected as the suitable intercalation ion that enable in‐situ forming the SrSO4 CEI after partial release upon charge process. Moreover, density functional theory calculation and multiple characterization research indicate that such SrSO4 interphase shows an electronic insulation to stabilize the interfacial pH, inhibit the Mn dissolution, and promote the efficient de‐solvation of hydrated zinc ions. Benefited from the self‐optimizing cathode/electrolyte interface chemistry, the 2.5% Sr‐MnO2 one exhibits higher specific capacity (304.1 mA h g‐1 at 0.5 A g‐1), better rate capability (115 mA h g‐1 at 10 A g‐1), as well as higher capacity retention of 87.9% after 1000 cycles at 2 A g‐1, when compared with pure δ‐MnO2 electrode. This study provides a new insight on understanding the functions of ion intercalation engineering to design robust layered cathode for high‐performance aqueous zinc‐ion batteries and beyond.