IR Near-Field Spectroscopy and Imaging of Single LixFePO4 Microcrystals

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• 作者：I. T. Lucas ; A. S. McLeod ; J. S. Syzdek ; D. S. Middlemiss ; C. P. Grey ; D. N. Basov ; R. Kostecki
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：January 14, 2015
• 年：2015
• 卷：15
• 期：1
• 页码：1-7
• 全文大小：364K
• ISSN：1530-6992

文摘

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_xFePO₄, 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.