Mixed-anion materials for Li-ion batteries have been attracting attention in view of their capabilities with tunable electrochemical properties. Herein, we compare two isostructural (Fm-3m) model intercalation materials Li2VO3 and Li2VO2F with O2- and mixed O2-/F- anions, respectively. Synchrotron X-ray diffraction and pair distribution function data confirm large structural similarity over long-range and at atomic scale for these materials. However, they show distinct electrochemical properties and kinetic behaviour arising from the different anion environment and the consequent difference in cationic electrostatic repulsion. In comparison with Li2VO3 with an active V4+/5+ redox reaction, the material Li2VO2F with oxofluoro anions and a partial activity of V3+/5+ redox reaction favors higher theoretical capacity (460 mAh g-1 vs. 230 mAh 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 cm2 s-1 vs. ~10-11 cm2 s-1). This work not only provides insights in understanding anion chemistry, but also suggests rational design of new mixed-anion battery materials.