Zhao Qinghe, Song Aoye, Zhao Wenguang, Qin Runzhi, Ding Shouxiang, Chen Xin, Song Yongli, Yang Luyi, Lin Hai, Li Shunning, Pan Feng
School of Advanced Materials, Peking University Shenzhen Graduate School, Shenzhen, 518055, P. R. China.
Angew Chem Int Ed Engl. 2021 Feb 19;60(8):4169-4174. doi: 10.1002/anie.202011588. Epub 2020 Dec 21.
The recent developments in rechargeable aqueous batteries have witnessed a burgeoning interest in the mechanism of proton transport in the cathode materials. Herein, for the first time, we report the Grotthuss proton transport mechanism in α-MnO which features wide [2×2] tunnels. Exemplified by the substitution doping of Ni (≈5 at.%) in α-MnO that increases the energy density of the electrode by ≈25 %, we reveal a close link between the tetragonal-orthorhombic (TO) distortion of the lattice and the diffusion kinetics of protons in the tunnels. Experimental and theoretical results verify that Ni dopants can exacerbate the TO distortion during discharge, thereby facilitating the hydrogen bond formation in bulk α-MnO . The isolated direct hopping mode of proton transport is switched to a facile concerted mode, which involves the formation and concomitant cleavage of O-H bonds in a proton array, namely via Grotthuss proton transport mechanism. Our study provides important insight towards the understanding of proton transport in MnO and can serve as a model for the compositional design of cathode materials for rechargeable aqueous batteries.
可充电水系电池的最新进展引发了人们对阴极材料中质子传输机制的浓厚兴趣。在此，我们首次报道了具有宽[2×2]隧道结构的α-MnO中的格罗特斯质子传输机制。以α-MnO中Ni（约5原子%）的替代掺杂为例，其使电极的能量密度提高了约25%，我们揭示了晶格的四方-正交（TO）畸变与隧道中质子的扩散动力学之间的紧密联系。实验和理论结果证实，Ni掺杂剂在放电过程中会加剧TO畸变，从而促进块状α-MnO中氢键的形成。质子传输的孤立直接跳跃模式转变为一种简便的协同模式，该模式涉及质子阵列中O-H键的形成和随之而来的断裂，即通过格罗特斯质子传输机制。我们的研究为理解MnO中的质子传输提供了重要见解，并可作为可充电水系电池阴极材料成分设计的模型。
