A Guest Cation Screening Principle for Enabling Customized Cathode/Electrolyte Interface Chemistry and Self-Enhanced...

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 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-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.