title: Structural transformation of LiVOPO4 to Li3V2(PO4)3 with enhanced capacity.
abstract: In the present investigation, we report the transformation of alpha-LiVOPO 4 to alpha-Li 3V 2(PO 4) 3, leading to an enhancement of capacity. The alpha-LiVOPO 4 sample was synthesized by a sol-gel method, followed by sintering at 550-650 degrees C in a flow of 5% H 2/Ar. The structural transformation of a triclinic alpha-LiVOPO 4 structure to a monoclinic alpha-Li 3V 2(PO 4) 3 structure was observed at higher sintering temperatures (700-800 degrees C in a flow of 5% H 2/Ar). The alpha-Li 3V 2(PO 4) 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 LiVOPO 4 to Li 3V 2(PO 4) 3.
authors.affiliation: Department of Chemistry, National Taiwan University, Taipei 106, Taiwan.
authors.forename: H T
authors.initials: HT
authors.lastname: Kuo
authors.forename: N C
authors.initials: NC
authors.lastname: Bagkar
authors.forename: R S
authors.initials: RS
authors.lastname: Liu
authors.forename: C H
authors.initials: CH
authors.lastname: Shen
authors.forename: D S
authors.initials: DS
authors.lastname: Shy
authors.forename: X K
authors.initials: XK
authors.lastname: Xing
authors.forename: J-F
authors.initials: JF
authors.lastname: Lee
authors.forename: J M
authors.initials: JM
authors.lastname: Chen