Hua Xiao, Allan Phoebe K, Gong Chen, Chater Philip A, Schmidt Ella M, Geddes Harry S, Robertson Alex W, Bruce Peter G, Goodwin Andrew L
Inorganic Chemistry Laboratory, University of Oxford, Oxford, OX1 3QR, UK.
School of Chemistry, University of Birmingham, Birmingham, B15 2TT, UK.
Nat Commun. 2021 Jan 25;12(1):561. doi: 10.1038/s41467-020-20736-6.
Binary metal oxides are attractive anode materials for lithium-ion batteries. Despite sustained effort into nanomaterials synthesis and understanding the initial discharge mechanism, the fundamental chemistry underpinning the charge and subsequent cycles-thus the reversible capacity-remains poorly understood. Here, we use in operando X-ray pair distribution function analysis combining with our recently developed analytical approach employing Metropolis Monte Carlo simulations and non-negative matrix factorisation to study the charge reaction thermodynamics of a series of Fe- and Mn-oxides. As opposed to the commonly believed conversion chemistry forming rocksalt FeO and MnO, we reveal the two oxide series topotactically transform into non-native body-centred cubic FeO and zincblende MnO via displacement-like reactions whose kinetics are governed by the mobility differences between displaced species. These renewed mechanistic insights suggest avenues for the future design of metal oxide materials as well as new material synthesis routes using electrochemically-assisted methods.
二元金属氧化物是锂离子电池颇具吸引力的阳极材料。尽管在纳米材料合成以及理解初始放电机制方面持续投入精力，但支撑充电及后续循环（即可逆容量）的基本化学原理仍知之甚少。在此，我们采用原位X射线对分布函数分析，并结合我们最近开发的采用 metropolis 蒙特卡罗模拟和非负矩阵分解的分析方法，来研究一系列铁氧化物和锰氧化物的充电反应热力学。与通常认为的形成岩盐型FeO和MnO的转化化学不同，我们揭示了这两个氧化物系列通过类似位移的反应进行拓扑转变，形成非天然的体心立方FeO和闪锌矿型MnO，其动力学受位移物种之间迁移率差异的控制。这些新的机理见解为金属氧化物材料的未来设计以及使用电化学辅助方法的新材料合成路线提供了思路。
