title: Li(+) intercalation in isostructural Li2VO3 and Li2VO2F with O(2-) and mixed O(2-)/F(-) anions.
abstract: Mixed-anion materials for Li-ion batteries have been attracting attention in view of their tunable electrochemical properties. Herein, we compare two isostructural (Fm3̅m) model intercalation materials Li2VO3 and Li2VO2F with O(2-) and mixed O(2-)/F(-) anions, respectively. Synchrotron X-ray diffraction and pair distribution function data confirm large structural similarity over long-range and at the atomic scale for these materials. However, they show distinct electrochemical properties and kinetic behaviour arising from the different anion environments and the consequent difference in cationic electrostatic repulsion. In comparison with Li2VO3 with an active V(4+/5+) redox reaction, the material Li2VO2F with oxofluoro anions and the partial activity of V(3+/5+) redox reaction favor higher theoretical capacity (460 mA h g(-1)vs. 230 mA h g(-1)), higher voltage (2.5 V vs. 2.2 V), lower polarization (0.1 V vs. 0.3 V) and faster Li(+) chemical diffusion (∼10(-9) cm(2) s(-1)vs. ∼10(-11) cm(2) s(-1)). This work not only provides insights into the understanding of anion chemistry, but also suggests the rational design of new mixed-anion battery materials.
authors.affiliation: Helmholtz Institute Ulm for Electrochemical Energy Storage, 89081 Ulm, Germany. ruiyong.chen@kit.edu hc18chen@gmail.com.
authors.forename: Ruiyong
authors.initials: R
authors.lastname: Chen
authors.forename: Shuhua
authors.initials: S
authors.lastname: Ren
authors.forename: Murat
authors.initials: M
authors.lastname: Yavuz
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Guda
authors.forename: Viktor
authors.initials: V
authors.lastname: Shapovalov
authors.forename: Raiker
authors.initials: R
authors.lastname: Witter
authors.forename: Maximilian
authors.initials: M
authors.lastname: Fichtner
authors.forename: Horst
authors.initials: H
authors.lastname: Hahn