Revealing the chemical separated two-phase structure in lithium-manganese-rich cathode

作者：Jiayi Wang, Xincheng Lei, Hao Meng, Pengxiang Ji, Tenglong Lu, Weijun Liang, Xiaozhi Liu, Sheng Meng, Yi Xu, Miao Liu, Xin Wang, Dong Su · 发表于：National Science Review · 年份：2025 · DOI：10.1093/nsr/nwaf202 · 被引用次数：14 · 研究领域：Advancements in Battery Materials、Advanced Battery Technologies Research、Extraction and Separation Processes

ABSTRACT Lithium-manganese-rich (LMR) oxides are regarded as one of the most promising cathode materials for next-generation batteries. However, their poor rate capability and performance degradation during cycling present significant challenges for practical applications. Understanding how to optimize their microscopic structures during synthesis may provide critical insights for enhancing their performance. In this work, we investigated the structural evolution during the solid-state sintering of Li1.2Ni0.2Mn0.6O2 from Li-/Mn-/Ni-carbonate precursors. Combining X-ray diffraction and transmission electron microscopy (TEM) techniques, we observed the nucleation of a nanoscaled solid-solution phase at 550°C, accompanied by secondary phases of spinel-like, layered and rock salt. At 800°C, a relatively pure solid-solution phase R3̅m is formed. Notably, we uncovered, for the first time, a phase transition from a solid-solution structure to a chemically separated two-phase structure when annealing the sample from 850°C to 900°C. Atomic resolution scanning-TEM (STEM) imaging clearly distinguished the C2/m phase from the R3̅m phase, separated by a coherent grain boundary, as confirmed by using STEM–energy-dispersion spectroscopy mapping. Our calculations indicate that the diffusion of Ni²⁺ induced by high-temperature activation plays a significant role in facilitating the phase separation. The relatively large chemically separated two-phase structure is expected to exhibit different...