Rational optimization of substituted α‐MnO₂ cathode for aqueous zinc‐ion battery

Density functional theory (DFT) is utilized to explore the effects of increasing concentrations of vanadium (V) and chromium (Cr) substitution on the discharge of α‐MnO 2 cathode in hydrated zinc‐ion batteries (ZIBs). During H + ‐intercalation and Zn 2+ ‐intercalation, Cr‐substitution proves to be more effective than V‐substitution in promoting discharge behaviors. Transitioning from Mn 0.875 Cr 0.125 O 2 , Mn 0.75 Cr 0.25 O 2 to Mn 0.625 Cr 0.375 O 2 is found to consistently enhance the discharge voltage, along with improved tunnel structure retention and volume expansion suppression. In comparison, the promoting effect of increasing V‐substitution is relatively small at initial discharge stages and leads to degradation at later stages, primarily due to an increased concentration of unstable Mn 2+ ion. The superior effect of Cr‐substitution is attributed to the unique atomic and electronic structures of substituted Cr 4+ and reduced Cr 3+ ions during discharge. These ions serve as active electron acceptors to limit the formation of Mn 3+ and Mn 2+ ions, and as anchors to stabilize the α‐MnO 2 framework and intercalated H + /Zn 2+ ions, respectively. Our study highlights fine‐tuning through substitution to enhance the performance of α‐MnO 2 ‐based cathode materials in ZIBs.