Orbital engineering-activated intrinsic conduction enables ultra-high-rate performance zinc storage in manganese dioxide

Abstract

Layered manganese oxides (δ-MnO₂) are regarded as promising cathodes for aqueous zinc-ion batteries (AZIBs) owing to their abundant resources, multiple electron transfer, and environmental benignity. However, their poor intrinsic conductivity and severe Mn dissolution significantly limit their rate capability, rendering them insufficient to meet the “fast-charging” requirements of AZIBs. Herein, an orbital-engineering driven strategy is proposed to enhance the intrinsic conductivity and improve the electrochemical performance of δ-MnO₂. Based on high-throughput simulations, a theoretical framework for intelligent screening is first established. The results demonstrated that Fe-doped δ-MnO₂ (Fe–MnO₂) exhibits the strongest electron delocalization effect, with a charge-transfer number of 3.54. This originates from the orbital hybridization between Fe and O atoms, which introduces new electronic states, together with the degeneracy of d_xz and d_yz in Fe 3d orbitals. These effects collectively enhance electron delocalization around Fe atoms and electron localization around O atoms, thereby boosting intrinsic conductivity. Moreover, the Fe–O bonds formed by the Fe injection effectively increase the Mn dissolution energy and improve structural stability. Guided by theoretical predictions and supported by in situ/ex situ characterization, the activated intrinsic conduction enables the synthesized Fe–MnO₂ to not only increase electron density and accelerate charge transfer but also promote H⁺/Zn²⁺ reaction kinetics, leading to significantly enhanced rate performance. Consequently, Fe–MnO₂ delivers an ultrahigh rate performance of 20 A g⁻¹ (∼15 mA cm⁻²), with a capacity decay rate as low as 0.00037% per cycle over 30 000 cycles in 2 M ZnSO₄ + 0.1 M MnSO₄ electrolyte. This orbital-level activation of intrinsic conductivity via atom doping provides a new perspective for developing highly stable Mn-based cathodes for fast-charging AZIBs.