In situ architecting amorphous manganese oxide/MXene heterostructure electrode with fast ion transport and structural stability in aqueous Zn–Mn batteries

Abstract

To address challenges associated with sluggish dissolution kinetics of hydrated zinc and manganese ions in secondary aqueous zinc manganese batteries, we synthesized Ti₃C₂F–MXene by in situ preparation of amorphous manganese dioxide (a-MnO₂) with satisfactory specific surface area and excellent ion diffusion. Our results demonstrate that a-MnO₂/Ti₃C₂F has ultrahigh average capacity (403.7 mA h g⁻¹) compared to pure a-MnO₂ (216.7 mA h g⁻¹) at 300 mA g⁻¹, along with superb cycle stability compared to the continuous capacity decay of pure a-MnO₂ at a high current density of 2000 mA g⁻¹. Detailed in situ/non-in situ characterization indicates two energy storage modes (Zn²⁺/H⁺ intercalation/deintercalation and ZSH reversible conversion reactions) within the heterostructure of a-MnO₂/Ti₃C₂F. We also found that the structural framework of a-MnO₂/Ti₃C₂F positively affects the reversible conversion and uniform dispersion of ZSH, as well as the intercalation and deintercalation of Zn²⁺/H⁺ during the charging and discharging process. This result is explained by a density functional theory (DFT) analysis, revealing that the diffusion energy barrier in the a-MnO₂/MXene framework is significantly lower than that in the crystal α-MnO₂/MXene due to the orbital hybridization between Ti-d and O-p. Our work offers new avenues for the design of high-performance water-based zinc ion batteries.