Structure, Shift in Redox Potential and Li-Ion Diffusion Behavior in Favorite LiFe_1?xV_xPO₄F Solid-Solution Cathodes.

ABSTRACT: Solid-solution Li-ion cathode materials transform through a single-phase reaction thus leading to a long-term structural stability and improved cyclability. In this work, a two- to single-phase Li⁺-extraction/insertion mechanism is studied through tuning the stoichiometry of transition-metal Fe/V cations to trigger a transition in the chemical reactivity path. Tavorite triclinic-structured LiFe_1-xV_xPO₄F (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) solid-solution powders were prepared by a facile one-step solid-state method from hydrothermal-synthesized and commercial raw materials. The broad shape of cyclic voltammetry (CV) peaks, sloping charge/discharge profiles and sloping open-circuit voltage (OCV) profiles were observed in LiFe_1-xV_xPO₄F solid-solution cathodes while 0 < x < 1. These confirm strongly a single-phase behavior which is different from the two-phase behavior in the end-members (x = 0 or 1). The electronegativity of M (M = Fe_1-xV_x) for the redox potential of Fe^2+/3+ couple or the M-O₄F₂ bond length for the V^3+/4+ couple plays respectively a dominant role in LiFe_1-xV_xPO₄F solid-solution cathodes.

SUBMITTER: Yan JL 

PROVIDER: S-EPMC6572713 | biostudies-literature | 2019 May

REPOSITORIES: biostudies-literature