Influence of synthesis approach on the electrochemical properties of (Li3V2(PO4)3-LiVOPO4)/graphite composite material for Li-ion batteries

Abstract

In this work, a dual-phase Li3V2(PO4)3-LiVOPO4 cathode material was synthesized using a novel vanadium-excess sol-gel process, followed by the addition of graphite by compositing in-situ or ball milling mixing. The different graphite addition approaches did not affect the ratio of the two phases in the composite but significantly influenced its electrochemical performance. The Li3V2(PO4)3-LiVOPO4/G sample prepared by in-situ compositing showed a special flake-like morphology with a uniform distribution of graphite and the cathode material showed significantly superior electrochemical performance in a wide voltage window of 1.5–4.5 V with discharge capacities of 281, 250, and 211 mAh g−1 at a discharge rate of 0.2 C, 1 C, and 10 C, respectively, as well as higher capacity retention of 88% and 67% after 100 and 650 cycles at high discharge rates of 1 C and 10 C, compared to its ball milling mixed counterpart. The excellent electrochemical performance can be ascribed to the mutual modifications induced by in-situ graphite addition and their synergistic effects.