TY - JOUR AU - Xiaosong Liu AU - Jun Liu AU - Ruimin Qiao AU - Yan Yu AU - Hong Li AU - Liumin Suo AU - Yong-sheng Hu AU - Yi- De Chuang AU - Guojiun Shu AU - Fangcheng Chou AU - Tsu-Chien Weng AU - Dennis Nordlund AU - Dimosthenis Sokaras AU - Yung J Wang AU - Hsin Lin AU - Bernardo Barbiellini AU - Arun Bansil AU - Xiangyun Song AU - Zhi Liu AU - Shishen Yan AU - Gao Liu AU - Shan Qjao AU - Thomas J Richardson AU - David G Prendergast AU - Zahid Hussain AU - Frank M.F de Groot AU - Wanli Yang AB -

Through soft X-ray absorption spectroscopy, hard X-ray Raman scattering, and theoretical simulations, we provide the most in-depth and systematic study of the phase transformation and (de)lithiation effect on electronic structure in LixFePO4 nanoparticles and single crystals. Soft X-ray reveals directly the valence states of Fe 3d electrons in the vicinity of Fermi level, which is sensitive to the local lattice distortion, but more importantly offers detailed information on the evolution of electronic states at different electrochemical stages. The soft X-ray spectra of LixFePO4 nanoparticles evolve vividly with the (de)lithiation level. The spectra fingerprint the (de)lithiation process with rich information on Li distribution, valency, spin states, and crystal field. The high resolution spectra reveal a subtle but critical deviation from two-phase transformation in our electrochemically prepared samples. In addition, we performed both first principles calculations and multiplet simulations of the spectra and quantitatively determined the 3d valence states that are completely redistributed through (de)lithiation. This electronic reconfiguration was further verified by the polarization-dependent spectra collected on LiFePO4 single crystals, especially along the lithium diffusion direction. The evolution of the 3d states is overall consistent with the local lattice distortion and provides a fundamental picture of the (de)lithiation effects on electronic structure in the LixFePO4 system.

BT - Journal of the American Chemical Society DA - 08/2012 DO - 10.1021/ja303225e IS - 33 LA - eng N2 -

Through soft X-ray absorption spectroscopy, hard X-ray Raman scattering, and theoretical simulations, we provide the most in-depth and systematic study of the phase transformation and (de)lithiation effect on electronic structure in LixFePO4 nanoparticles and single crystals. Soft X-ray reveals directly the valence states of Fe 3d electrons in the vicinity of Fermi level, which is sensitive to the local lattice distortion, but more importantly offers detailed information on the evolution of electronic states at different electrochemical stages. The soft X-ray spectra of LixFePO4 nanoparticles evolve vividly with the (de)lithiation level. The spectra fingerprint the (de)lithiation process with rich information on Li distribution, valency, spin states, and crystal field. The high resolution spectra reveal a subtle but critical deviation from two-phase transformation in our electrochemically prepared samples. In addition, we performed both first principles calculations and multiplet simulations of the spectra and quantitatively determined the 3d valence states that are completely redistributed through (de)lithiation. This electronic reconfiguration was further verified by the polarization-dependent spectra collected on LiFePO4 single crystals, especially along the lithium diffusion direction. The evolution of the 3d states is overall consistent with the local lattice distortion and provides a fundamental picture of the (de)lithiation effects on electronic structure in the LixFePO4 system.

PY - 2012 SN - 0002-7863 SP - 13708 EP - 13715 T2 - Journal of the American Chemical Society TI - Phase Transformation and Lithiation Effect on Electronic Structure of LixFePO4: An In-Depth Study by Soft X-ray and Simulations VL - 134 ER -