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 MnO 2 cathode in high‐performance aqueous zinc‐ion batteries. This work proposes a theoretical screening principle to select the compatible guest cation for MnO 2 host, not only to strengthen the structure but also customize high‐efficiency cathode/electrolyte interphase (CEI). As identified, Sr 2+ is selected as the suitable intercalation ion that enable in situ forming the SrSO 4 CEI after partial release upon charge process. Moreover, density functional theory calculation and multiple characterization research indicate that such SrSO 4 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‐MnO 2 one exhibits higher specific capacity (304.1 mAh g −1 at 0.5 A g −1 ), better rate capability (115 mAh 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‐MnO 2 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.