Ostwald ripening mechanism-derived MnOOH induces lattice oxygen escape for efficient aqueous MnO2–Zn batteries

Abstract

Aqueous rechargeable MnO₂–Zn batteries have attracted much attention in recent years due to their high security, low cost and environmentally friendly nature. Nevertheless, the practical application of MnO₂ cathode materials is limited by the slow reaction kinetics during cycling and the poor cycle life caused by the disproportionation reaction of Mn. Here, we innovatively prepared MnOOH intermediates via the Ostwald ripening mechanism, followed by thermal treatment to induce lattice oxygen escape to finally obtain oxygen-defect-rich β-MnO₂(O_d) nanorods. First-principles calculations have shown that the oxygen defects can serve as p-type dopants to yield better electrical conductivity and enhance the adsorption capability of β-MnO₂ for protons. The tested Zn//β-MnO₂(O_d) batteries demonstrated an impressive specific capacity of 330.9 mA h g⁻¹ at 100 mA g⁻¹. After 800 charge–discharge cycles at 1 A g⁻¹, they maintained a capacity of 171 mA h g⁻¹ with a capacity retention rate of 88.9%. This work offers fascinating prospects for the creation of MnO₂ with oxygen-defects and provides distinct insights towards achieving high efficiency, more productive aqueous zinc ion batteries.