Unlocking the critical role of Mg doping in α-MnO₂ cathode for aqueous zinc ion batteries

Owing to the synergistic effect of metal atoms and the concomitant oxygen vacancies, doping is considered as one of the most efficient strategies to overcome the issues of sluggish dynamics and poor stability of MnO₂ for aqueous zinc-MnO₂ batteries. Nevertheless, the key role of the doped individual metal atom is rarely investigated. Herein, a Mg-doped α-MnO₂ configuration (MMO) with deficient oxygen vacancy has been innovatively constructed via a simple one-step hydrothermal method. Experimental measurements and theoretical calculations have been carried out to systemically reveal the important effect of the doped Mg atoms for its stabilized structure and boosted dynamics. The reduced reaction resistance, polarization, ion diffusion barrier, and improved ion diffusion coefficient and stability endow MMO-2 electrode with a superior capacity retention of 77.2 % (from 311 to 240 mAh/g) after 700 cycles at 1C (600 mA g⁻¹), which was higher to that of bare α-MnO₂ (60.3 %, from 214 to 129 mAh/g). This work provides a distinctive vision to understand the individual effect of the doped metal atoms in MnO₂ cathode, and is conducive to lights the way towards fabricating practical Mn-based cathode for aqueous zinc ion batteries.