title: A XANES study of LiVPO4F: a factor analysis approach.
abstract: Evolving factor analysis (EFA) of X-ray absorption near-edge spectroscopy (XANES) data is shown to be a useful tool to understand the phase relationships and compositional ranges of stability in the LiVPO4F-VPO4F system. EFA was used to calculate the concentration of phases versus state-of-charge in a lithium-ion battery and true XANES spectra. The results of EFA showed that, indeed, three phases were present during cycling of a LiVPO4F∥Li cell: LiVPO4F, LixVPO4F, and VPO4F. In contrast to what was reported by others, the second phase was not a fixed composition with x = 0.67, but, instead, existed over a range of lithium stoichiometry, x = 0.25 to 0.80. EFA results also showed that the reactions leading to these phases are reversible.
authors.affiliation: Key Laboratory of Physics and Technology for Advanced Batteries (Ministry of Education), College of Physics, Jilin University, Changchun, 130012, P. R. China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Piao
authors.forename: Yan
authors.initials: Y
authors.lastname: Qin
authors.forename: Yang
authors.initials: Y
authors.lastname: Ren
authors.forename: Steve M
authors.initials: SM
authors.lastname: Heald
authors.forename: Chengjun
authors.initials: C
authors.lastname: Sun
authors.forename: Dehua
authors.initials: D
authors.lastname: Zhou
authors.forename: Bryant J
authors.initials: BJ
authors.lastname: Polzin
authors.forename: Steve E
authors.initials: SE
authors.lastname: Trask
authors.forename: Khalil
authors.initials: K
authors.lastname: Amine
authors.forename: Yinjin
authors.initials: Y
authors.lastname: Wei
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
authors.forename: Ira
authors.initials: I
authors.lastname: Bloom
authors.forename: Zonghai
authors.initials: Z
authors.lastname: Chen