Zhang Wei, Yu Hui-Chia, Wu Lijun, Liu Hao, Abdellahi Aziz, Qiu Bao, Bai Jianming, Orvananos Bernardo, Strobridge Fiona C, Zhou Xufeng, Liu Zhaoping, Ceder Gerbrand, Zhu Yimei, Thornton Katsuyo, Grey Clare P, Wang Feng
Sustainable Energy Technologies Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
Department of Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Sci Adv. 2018 Jan 12;4(1):eaao2608. doi: 10.1126/sciadv.aao2608. eCollection 2018 Jan.
Nanoparticulate electrodes, such as Li FePO, have unique advantages over their microparticulate counterparts for the applications in Li-ion batteries because of the shortened diffusion path and access to nonequilibrium routes for fast Li incorporation, thus radically boosting power density of the electrodes. However, how Li intercalation occurs locally in a single nanoparticle of such materials remains unresolved because real-time observation at such a fine scale is still lacking. We report visualization of local Li intercalation via solid-solution transformation in individual Li FePO nanoparticles, enabled by probing sub-angstrom changes in the lattice spacing in situ. The real-time observation reveals inhomogeneous intercalation, accompanied with an unexpected reversal of Li concentration at the nanometer scale. The origin of the reversal phenomenon is elucidated through phase-field simulations, and it is attributed to the presence of structurally different regions that have distinct chemical potential functions. The findings from this study provide a new perspective on the local intercalation dynamics in battery electrodes.
纳米颗粒电极，如磷酸铁锂，由于其扩散路径缩短以及能够通过非平衡途径快速嵌入锂，在锂离子电池应用中相对于其微米颗粒对应物具有独特优势，从而从根本上提高了电极的功率密度。然而，此类材料单个纳米颗粒中锂的局部嵌入过程仍未得到解决，因为目前仍缺乏在如此精细尺度上的实时观测。我们报告了通过原位探测晶格间距亚埃级变化，实现了在单个磷酸铁锂纳米颗粒中通过固溶体转变对局部锂嵌入进行可视化。实时观测揭示了不均匀嵌入现象，同时伴随着纳米尺度上锂浓度的意外反转。通过相场模拟阐明了反转现象的起源，这归因于存在具有不同化学势函数的结构不同区域。本研究结果为电池电极中的局部嵌入动力学提供了新的视角。
