Mn-O bond Engineering Mitigating Jahn-Teller Effects of Manganese Oxide for Aqueous Zinc-ion Battery Applications

Manganese-based oxides (MNO) are commonly employed as cathodes in aqueous zinc-ion batteries (AZIBs) due to their affordability, minimal toxicity, and various valence states. However, the Jahn–Teller (J-T) effect of high-spin Mn3+ can induce Mn2+ dissolution and irreversible phase changes, significantly deteriorating the cycling life. Herein, 1D core–shell Mn3O4 with doping of heteroatoms is successfully designed through a dopamine coating and subsequent annealing strategy. Specifically, N-doping elongated the Mn-O bonds within the Mn3O4 crystal, suppressing lattice J-T distortion caused by MnO6 octahedra. This result in weakened electrostatic repulsion, contributing not only to structural stability but also facilitating the insertion of more cations. Simultaneously, N-doping carbon encapsulates Mn3O4 with an external conductive network, providing a unique mesoporous morphology and improved conductive pathways. Therefore, the optimized NC@Mn3O4 displays high capacity (420 mAh/g at 1 A/g) and superior cycle stability (90.34 % of capacity retention over 1000 cycles at 3 A/g). In addition, the charge storage of NC@Mn3O4 is the highly reversible H+/Zn2+ co-intercalation/extraction reactions, which revealed by ex-situ characterizations. This work initially proposed an effective design trend to eliminate the J-T effect, and provided assistance for the application of MNO cathode materials.