Interface Polarization Effects Enhancing Mn₂O₃@TiO₂@MXene Heterostructures for Aqueous Magnesium Ion Capacitors: Guided Charge Distribution and Transportation via Built-in Electric Fields

The electrochemical performances of aqueous magnesium ion energy storage devices rely on the transmission capacity of magnesium ions (Mg2+) at the electrode/electrolyte interface. However, the diffusion of Mg2+ is hindered by the strong electrostatic attraction of doubly charged magnesium cations. Herein, novel Mn2O3@TiO2@MXene three-phase heterostructures with rich phase boundaries and synergistic effects is successfully designed. As expected, the mesoporous Mn2O3/TiO2@MXene can deliver a relatively high specific capacity of 241.5 mAh g(-1) at 0.1 A g(-1). Moreover, the energy density of the device using mesoporous Mn2O3@TiO2@MXene as cathode can reach 146.62 Wh kg(-1). The unique construction of extensive interfaces between different phases creates a polarization effect. This polarization effect leads to intrinsic electric fields that guide charge distribution and promote fast migration of Mg2+ ions. Additionally, the in-situ growth of TiO2 nanoparticles derived from MXene on Mn2O3 helps mitigate the volume expansion of host material, resulting in enhanced cycle stability. By strategically implementing the interface polarization effect and carefully engineering the heterostructure interfaces, we demonstrate a promising electrode synthesis approach with potential commercial viability and robust performance. This research aims to advance the field of materials science by exploring interface engineering and the multifunctional applications of MXene-related materials.