Co-Doping Inducing d-Electron Delocalization in α-MnO2 for High-Performance Zinc-Ion Batteries

Element doping technology is widely recognized as an effective strategy for high-performance MnO2-based cathode materials. While this approach improves the electronic and ionic conductivity of MnO2, it is often accompanied by the introduction of oxygen vacancies. This synergistic effect poses challenges for precisely investigating the effect of doping elements on the d-electron configuration of the Mn site and establishing atomic-level structure-activity relationships for high-energy aqueous zinc-MnO2 batteries. In this paper, the rational design of d-electron configurations in the Mn site has been achieved through simple Co doping in α-MnO2 (CMO). Experimental results confirm that the introduction of Co can delocalize the d-electrons of the Mn site and increase the ratio of eg (dz2 and dx2−y2) occupancy. Consequently, the charge transfer resistance, electrode polarization, and Zn2+ diffusion coefficient of the CMO-2 cathode have been greatly optimized. Thus, the as-prepared electrode delivers a high specific capacity of 287.4 mAh g−1 at 1 A g−1, with a capacity retention rate of 92.8% and a corresponding remaining capacity of 199.7 mAh g−1 after 700 cycles. This study paves the road for the designation and construction of high-energy MnO2 cathodes with optimized electronic structures for advanced aqueous zinc ion batteries.