High-rate performance of xLiFePO4·yLi3V2(PO4)3/C composite cathode materials synthesized via polyol process

xLiFePO4·yLi3V2(PO4)3/C composite cathode materials were synthesized via a polyol process, using LiOH·H2O, Fe3(PO4)2·8H2O, V2O5 and H3PO4 as raw materials, citric acid and PEG as carbon sources, and TEG as both a solvent and a reductant. Structural and morphological characterizations of as-prepared materials were carried out by X-ray diffraction (XRD) as well as scanning electron microscopy (SEM), respectively. Furthermore, electrochemical properties of as-prepared materials were analyzed by charge–discharge tests, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). XRD results indicated that the composites consisting of an olivine phase of LiFePO4 and a monoclinic phase of Li3V2(PO4)3 are well-crystallized. It is found that the LF0.6P·LV0.4P/C composite exhibited better electrochemical performance than pristine LFP/C and LVP/C at 5 C and 10 C rate and delivered 126 mAh g−1 and 110 mAh g−1, respectively. The favorable particles morphology with less than 100 nm size and low extent agglomeration is believed as a factor. In addition, the co-existence of V3+-doped LiFePO4/C and Fe2+-doped Li3V2(PO4)3/C was supposed as another reason.

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► The composites were synthesized via polyol process and one-step sintering route.
► The discharge capacity of composite of LiFePO4 with Li3V2(PO4)3 was improved.
► The LF0.6V0.4P has extreme value appeared in the cell parameters and volumes.
► The sample LF0.6V0.4P has uniform particle size of about 200 nm.
► The LF0.6V0.4P has a stable capacity of about 110 mAh g−1 at 10 C after 50 cycles.