Wu Yifan, Cai Xincan, Lin Weiyi, Deng Yingdong, Zhang Qing, Li Haoyuan, Yan Pu, Zhong Guohui, Xie Jin
School of Physical Science and Technology, ShanghaiTech University Shanghai 201210 China.
Shanghai Key Laboratory of High-resolution Electron Microscopy, ShanghaiTech University Shanghai 201210 China.
Chem Sci. 2025 Apr 25;16(22):9809-9819. doi: 10.1039/d5sc00271k. eCollection 2025 Jun 4.
Solid-state calcination profoundly influences the structural integrity and electrochemical performance of polycrystalline layered oxide cathode materials in lithium-ion batteries. As temperatures increase, heterogeneous phase transitions driven by solid-state diffusion can result in structural non-uniformity. In this study, we employ characterization techniques and high-resolution electron microscopy to scrutinize the inherent heterogeneity observed in the early-stage of the solid-state lithiation process and its subsequent influence on the formation and merging of resultant LiNiCoMn (NCM90) grains on the surface of the secondary particle. We found that a conformal atomic layer deposited WO layer on the hydroxide precursor could be lithiated to form Li WO compounds, which are stable and non-dissolvable at the grain boundaries, further acting as a segregation layer to prevent the merging of grains during the formation of a layered phase on the surface of secondary particles, which preserves the route for the uniform lithiation of the inner part of the secondary particles. These investigations shed light on the effect of solid-state reaction heterogeneity and present a novel methodology for mitigating the persistent challenge by grain boundary engineering.
固态煅烧对锂离子电池中多晶层状氧化物阴极材料的结构完整性和电化学性能有深远影响。随着温度升高，由固态扩散驱动的异质相变会导致结构不均匀。在本研究中，我们采用表征技术和高分辨率电子显微镜来仔细观察在固态锂化过程早期观察到的固有异质性及其对二次颗粒表面上所得LiNiCoMn（NCM90）晶粒形成和合并的后续影响。我们发现，氢氧化物前驱体上沉积的共形原子层WO层可以被锂化形成Li₂WO₄化合物，该化合物在晶界处稳定且不可溶解，进一步作为隔离层，防止二次颗粒表面形成层状相时晶粒合并，从而保留二次颗粒内部均匀锂化的途径。这些研究揭示了固态反应异质性的影响，并提出了一种通过晶界工程缓解持续挑战的新方法。
