Sodiation Kinetics of Metal Oxide Conversion Electrodes: A Comparative Study with Lithiation
Sodiation Kinetics of Metal Oxide Conversion Electrodes: A Comparative Study with Lithiation
复制标题
DOI：
10.1021/acs.nanolett.5b01709
复制
发表时间：
2015-09-01
期刊：
影响因子：
10.8
通讯作者：
Su, Dong
中科院分区：
文献类型：
--
作者：
He, Kai;Lin, Feng;Su, Dong
钠离子电池（NIB）的发展可以提供锂离子电池（LIB）的替代品，实现可持续、低成本的能源存储。然而，由于钠离子与锂相比尺寸较大且 m/e 比较高，因此候选电极的钠化反应预计与相应的锂电极有显着差异。在这项工作中，我们通过一系列相关技术研究了典型过渡金属氧化物 NiO 的钠化机制，包括电化学和同步加速器研究、实时电子显微镜观察和从头算分子动力学 (MD) 模拟。我们发现钠化开始时形成的结晶Na2O反应层在阻止钠离子的进一步传输中起着重要作用。此外，NiO 中的钠化表现出“收缩核心”模式，这是由逐层反应产生的，正如从头开始 MD 模拟所确定的那样。然而，对于锂化，Li反位缺陷的形成显着扭曲了有利于Li插入的局部NiO晶格，从而提高了整体反应速率。这些观察结果描绘了金属氧化物转化材料中钠化和锂化之间的机械差异。更重要的是，我们的研究结果确定了理解反应层对电极功能的作用的重要性，从而为通过表面工程进一步优化 NIB 材料提供了重要的见解。
The development of sodium ion batteries (NIBs) can provide an alternative to lithium ion batteries (LIBs) for sustainable, low-cost energy storage. However, due to the larger size and higher m/e ratio of the sodium ion compared to lithium, sodiation reactions of candidate electrodes are expected to differ in significant ways from the corresponding lithium ones. In this work, we investigated the sodiation mechanism of a typical transition metal-oxide, NiO, through a set of correlated techniques, including electrochemical and synchrotron studies, real-time electron microscopy observation, and ab initio molecular dynamics (MD) simulations. We found that a crystalline Na2O reaction layer that was formed at the beginning of sodiation plays an important role in blocking the further transport of sodium ions. In addition, sodiation in NiO exhibits a "shrinking-core" mode that results from a layer-by-layer reaction, as identified by ab initio MD simulations. For lithiation, however, the formation of Li antisite defects significantly distorts the local NiO lattice that facilitates Li insertion, thus enhancing the overall reaction rate. These observations delineate the mechanistic difference between sodiation and lithiation in metal-oxide conversion materials. More importantly, our findings identify the importance of understanding the role of reaction layers on the functioning of electrodes and thus provide critical insights into further optimizing NIB materials through surface engineering.