δ-MnO2 has emerged as a highly promising cathode candidate for aqueous zinc-ion batteries (AZIBs) owing to its high theoretical capacity and structural controllability. Nevertheless, activating its two-electron redox reaction remains a significant challenge. Unlike conventional electrolyte optimization or heteroatom doping, this work introduces chemical bonding engineering to address this bottleneck. Herein, N-doped graphene (NG) is employed as a reducible template and conductive framework, guiding the uniform deposition of δ-MnO2 while establishing interfacial Mn–O–C and Mn–N chemical bonds. These bonds as “electron transfer bridges” not only accelerate interfacial charge transport but also modulate the electronic structure of Mn sites, which enables a higher proportion of Mn to participate in the two-electron reaction. Furthermore, the introduction of N and C elements with lower electronegativity than that of O weakens the strong Zn2+-lattice oxygen interaction, alleviating sluggish Zn2+ diffusion. Through these synergistic effects, the optimized cathode achieves a high capacity of 559 mAh g–1 at 0.1 A g–1, along with prominent cycling durability, retaining 248 mAh g–1 after 200 cycles at 1.0 A g–1, corresponding to a high-capacity retention of 80.8%. Furthermore, the enhanced kinetics and energy storage mechanisms are systematically investigated. This study presents a chemical bonding engineering to unlock the two-electron reaction capability of δ-MnO2, offering critical insights for high-performance AZIBs.
Wu et al. (Wed,) studied this question.