Daemi Sohrab R, Tan Chun, Vamvakeros Antonis, Heenan Thomas M M, Finegan Donal P, Di Michiel Marco, Beale Andrew M, Cookson James, Petrucco Enrico, Weaving Julia S, Jacques Simon, Jervis Rhodri, Brett Dan J L, Shearing Paul R
Electrochemical Innovation Lab, Department of Chemical Engineering, University College London, London WC1E 7JE, UK.
ESRF, The European Synchrotron, 71 Avenue des Martyrs, 38000 Grenoble, France and Finden Limited, Merchant House, 5 East Saint Helens Street, Abingdon, OX14 5EG, UK.
Phys Chem Chem Phys. 2020 Aug 24;22(32):17814-17823. doi: 10.1039/d0cp01851a.
This study presents the application of X-ray diffraction computed tomography for the first time to analyze the crystal dimensions of LiNi0.33Mn0.33Co0.33O2 electrodes cycled to 4.2 and 4.7 V in full cells with graphite as negative electrodes at 1 μm spatial resolution to determine the change in unit cell dimensions as a result of electrochemical cycling. The nature of the technique permits the spatial localization of the diffraction information in 3D and mapping of heterogeneities from the electrode to the particle level. An overall decrease of 0.4% and 0.6% was observed for the unit cell volume after 100 cycles for the electrodes cycled to 4.2 and 4.7 V. Additionally, focused ion beam-scanning electron microscope cross-sections indicate extensive particle cracking as a function of upper cut-off voltage, further confirming that severe cycling stresses exacerbate degradation. Finally, the technique facilitates the detection of parts of the electrode that have inhomogeneous lattice parameters that deviate from the bulk of the sample, further highlighting the effectiveness of the technique as a diagnostic tool, bridging the gap between crystal structure and electrochemical performance.
本研究首次展示了X射线衍射计算机断层扫描技术的应用，该技术用于分析以石墨为负极的全电池中循环至4.2 V和4.7 V的LiNi0.33Mn0.33Co0.33O2电极的晶体尺寸，空间分辨率为1μm，以确定电化学循环导致的晶胞尺寸变化。该技术的特性允许在三维空间中对衍射信息进行空间定位，并绘制从电极到颗粒水平的不均匀性图谱。对于循环至4.2 V和4.7 V的电极，在100次循环后，观察到晶胞体积总体下降了0.4%和0.6%。此外，聚焦离子束扫描电子显微镜横截面显示，颗粒开裂程度随上限截止电压而增加，进一步证实了严重的循环应力会加剧降解。最后，该技术有助于检测电极中晶格参数与样品主体不同的不均匀部分，进一步突出了该技术作为诊断工具的有效性，弥合了晶体结构与电化学性能之间的差距。
