Structural Modulation in the High Capacity Battery Cathode Material LiFeBO3

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• 作者：Yuri Janssen ; Derek S. Middlemiss ; Shou-Hang Bo ; Clare P. Grey ; Peter G. Khalifah
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：August 1, 2012
• 年：2012
• 卷：134
• 期：30
• 页码：12516-12527
• 全文大小：543K
• 年卷期：v.134,no.30(August 1, 2012)
• ISSN：1520-5126

文摘

The crystal structure of the promising Li-ion battery cathode material LiFeBO₃ has been redetermined based on the results of single crystal X-ray diffraction data. A commensurate modulation that doubles the periodicity of the lattice in the a-axis direction is observed. When the structure of LiFeBO₃ is refined in the 4-dimensional superspace group C2/c(伪0纬)00, with 伪 = 1/2 and 纬 = 0 and with lattice parameters of a = 5.1681 脜, b = 8.8687 脜, c = 10.1656 脜, and 尾 = 91.514掳, all of the disorder present in the prior C2/c structural model is eliminated and a long-range ordering of 1D chains of corner-shared LiO₄ is revealed to occur as a result of cooperative displacements of Li and O atoms in the c-axis direction. Solid-state hybrid density functional theory calculations find that the modulation stabilizes the LiFeBO₃ structure by 1.2 kJ/mol (12 meV/f.u.), and that the modulation disappears after delithiation to form a structurally related FeBO₃ phase. The band gaps of LiFeBO₃ and FeBO₃ are calculated to be 3.5 and 3.3 eV, respectively. Bond valence sum maps have been used to identify and characterize the important Li conduction pathways, and suggest that the activation energies for Li diffusion will be higher in the modulated structure of LiFeBO₃ than in its unmodulated analogue.