Probing Dopant Redistribution, Phase Propagation, and Local Chemical Changes in the Synthesis of Layered Oxide Battery Cathodes
Zhijie Yang, Linqin Mu, Dong Hou, Muhammad Mominur Rahman, Zhengrui Xu, Jue Liu, Dennis Nordlund, Cheng‐Jun Sun, Xianghui Xiao, Feng Lin
Abstract
Abstract Achieving the targeted control of layered oxide properties calls for more fundamental studies to mechanistically probe their evolution during their synthesis. Herein, dopant distribution, phase propagation, and local chemical changes as well as their interplay in multielement‐doped LiNiO 2 materials are investigated using spectroscopic, imaging, and scattering techniques. It is shown that dopants undergo dynamic redistribution in the Ni(OH) 2 host lattice at the early stage of calcination (below 300 °C). Such redistribution behavior exhibits strong dopant‐dependent characteristics, allowing for targeted surface and bulk doping control. The Ni oxidation process exhibits depth‐dependent characteristics and the most rapid Ni oxidation takes place between 300 and 700 °C. Using Ni oxidation state as the proxy for the phase transformation, the buildup of heterogenous phase propagation in the early stage of calcination is shown, especially along the radial direction of secondary particles. The radial heterogenous phase distribution gradually decreases upon completing the calcination. However, a high degree of mosaic‐like heterogeneity may still be present in the final product, departing from the perfect layered oxide. The present study offers fundamental insights into manipulating multiscale materials properties during calcination for obtaining stable, high‐energy layered oxide cathodes.