Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
Nano Lett. 2015 Jan 14;15(1):1-7. doi: 10.1021/nl5010898. Epub 2014 Dec 9.
This study demonstrates the unique capability of infrared near-field nanoscopy combined with Fourier transform infrared spectroscopy to map phase distributions in microcrystals of Li(x)FePO4, a positive electrode material for Li-ion batteries. Ex situ nanoscale IR imaging provides direct evidence for the coexistence of LiFePO4 and FePO4 phases in partially delithiated single-crystal microparticles. A quantitative three-dimensional tomographic reconstruction of the phase distribution within a single microcrystal provides new insights into the phase transformation and/or relaxation mechanism, revealing a FePO4 shell surrounding a diamond-shaped LiFePO4 inner core, gradually shrinking in size and vanishing upon delithiation of the crystal. The observed phase propagation pattern supports recent functional models of LiFePO4 operation relating electrochemical performance to material design. This work demonstrates the remarkable potential of near-field optical techniques for the characterization of electrochemical materials and interfaces.
本研究展示了红外近场纳米显微镜结合傅里叶变换红外光谱在绘制锂离子电池正极材料 Li(x)FePO4 微晶体的相位分布方面的独特能力。非原位纳米尺度 IR 成像为部分去锂化单晶微颗粒中 LiFePO4 和 FePO4 相共存提供了直接证据。对单个微晶体内部相分布的定量三维层析重建提供了对相变和/或弛豫机制的新见解，揭示了在晶体去锂化过程中，FePO4 壳围绕着菱形 LiFePO4 内核逐渐缩小并消失的现象。观察到的相传播模式支持了最近关于 LiFePO4 操作的功能模型，即将电化学性能与材料设计相关联。这项工作展示了近场光学技术在电化学材料和界面表征方面的巨大潜力。
