Structural Transformation of LiVOPO4 to Li3V2(PO4)3 with Enhanced Capacity

• Published in: The journal of physical chemistry. B 2008-09, Vol.112 (36), p.11250-11257
• Main Authors: Kuo, H. T, Bagkar, N. C, Liu, R. S, Shen, C. H, Shy, D. S, Xing, X. K, Lee, J.-F, Chen, J. M
• Format: Article
• Language: English
• Subjects: B: Macromolecules, Soft Matter
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp803210w

In the present investigation, we report the transformation of α-LiVOPO4 to α-Li3V2(PO4)3, leading to an enhancement of capacity. The α-LiVOPO4 sample was synthesized by a sol−gel method, followed by sintering at 550−650 °C in a flow of 5% H2/Ar. The structural transformation of a triclinic α-LiVOPO4 structure to a monoclinic α-Li3V2(PO4)3 structure was observed at higher sintering temperatures (700−800 °C in a flow of 5% H2/Ar). The α-Li3V2(PO4)3 phase was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, and X-ray absorption near edge spectrum (XANES) techniques. The valence shift of vanadium ions from +4 to +3 states was observed using in situ XANES experiments at V K-edge. The structural transformation is ascertained by the shape changes in pre-edge and near edge area of X-ray absorption spectrum. It was observed that the capacity was enhanced from 140 mAh/g to 164 mAh/g via structural transformation process of LiVOPO4 to Li3V2(PO4)3.