Stabilizing α-MnO₂ Tunnel Structure via Mo-Zn Synergistic Doping for Highly Efficient Zn²⁺ Storage

To address the rising demand for eco-friendly and efficient energy storage devices, rechargeable aqueous zinc ion batteries (AZIBs) are emerging as a promising candidate for large-scale energy storage. α-MnO₂ has attracted extensive attention for its open channels and exceptional Zn²⁺ storage capacity. However, the electrochemical performance of α-MnO₂ is significantly hindered by severe structural collapse and sluggish reaction kinetics. Herein, we propose a simple hydrothermal approach for co-doping Mo and Zn into tunnel-structured MnO₂ (MZMO). The ion diffusion kinetics of MZMO are optimized due to ameliorated electrical conductivity by doped cations and introduced oxygen vacancies within the MnO₂ lattice. Moreover, Mo and Zn co-doping stabilizes the MnO₂ framework, significantly enhancing its electrochemical performance during prolonged cycling. Charge storage mechanism analysis further validates the extraordinary stability of the MZMO phase structure during the Zn²⁺/H⁺ co-intercalation and deintercalation. The MZMO cathode demonstrates rapid and reversible Zn²⁺ storage, with a high capacity of 395 mAh g^-1 at 0.2 A g^-1, and the capacity remains at 136 mAh g^-1 after 1000 cycles at 2 A g^-1. This study demonstrates Mo and Zn co-doping is an effective strategy to enhance the electrochemical performance of MnO₂, offering valuable insights for developing other promising cathodes for AZIBs.