Structural Investigation of Quaternary Layered Oxides upon Na-Ion Deinsertion.
Structural Investigation of Quaternary Layered Oxides upon Na-Ion Deinsertion.
复制标题
Na离子脱嵌后四元层状氧化物的结构研究。
作者：
A. Mullaliu;Kazutoshi Kuroki;M. Keller;K. Kubota;D. Buchholz;S. Komaba;S. Passerini
钠离子电池是锂离子化学品的新兴替代品，用于大规模储能应用。与纯相层状氧化物相比，四元层状氧化物Na0.76Mn0.5Ni0.3Fe0.1Mg0.1O2由于P/O相混合的协同效应而在Na离子电池中提供了优异的电化学性能。该材料实际上由P3、P2和O3相的混合物以及新鉴定的无Na相构成，即，镍镁氧化物相，其改善了热去除并增强了电化学性能。在本文中，我们通过同步辐射X射线衍射在结构上研究了完全去辐射后发生的修饰，详细描述了Na去除后的材料结构重排，并揭示了两种不同充电方案的效果，即，恒流（CC）和恒流-恒压（CCCV）。虽然无Na相是电化学惰性的，可能有助于在循环期间电极中的热梯度的均匀化，但在从板间层提取Na离子期间出现O-P共生相，并且它们取决于去辐射水平。恒电流充电结束时施加恒定电压阶跃导致板间距离缩短和显著的体积收缩（-11.9%）。
Na-ion batteries are emerging alternatives to Li-ion chemistries for large-scale energy storage applications. Quaternary layered oxide Na0.76Mn0.5Ni0.3Fe0.1Mg0.1O2 offers outstanding electrochemical performance in Na-ion batteries compared to pure-phase layered oxides because of the synergistic effect of the P/O-phase mixing. The material is indeed constituted by a mixture of P3, P2, and O3 phases, and a newly identified Na-free phase, i.e., nickel magnesium oxide phase, which improves heat removal and enhances the electrochemical performance. Herein, we structurally investigate, through synchrotron-radiation X-ray diffraction, the modifications occurring after full desodiation, detailing the material structural rearrangement upon Na removal and revealing the effect of two different charging protocols, i.e., constant current (CC) and constant current-constant voltage (CCCV). While the Na-free phase is electrochemically inactive, likely helping in homogenization of the thermal gradient in the electrode during cycling, O-P intergrown phases appear during the extraction of Na ions from interslab layers, and they are dependent on the desodiation level. The application of a constant voltage step at the end of the galvanostatic charge is responsible for a shortening of the interslab distance and a significant volume contraction (-11.9%).