Facile synthesis of Li3V2(Po4)3/C nano-flakes with high-rate performance as cathode material for Li-ion battery

The flake-like Li3V2(PO4)3/C has been successfully synthesized by rheological phase method using polyvinyl alcohol (PVA) as template; the Li3V2(PO4)3/C without PVA assistance has been prepared for comparison. X-ray diffraction analysis shows that the two samples are well crystallized, and no impurity phases are detected. The scanning electron microscopy results reveal that there is a significant difference in morphologies between PVA-assisted sample and sample without PVA; the former shows a flake-like morphology, while the latter presents regular granular shape with some agglomeration. Transmission electron microscopy images reveal that Li3V2(PO4)3 particles are coated with a uniform surface carbon layer. The lattice fringes with a spacing of 0.428 nm can be clearly seen from the high-resolution transmission electron microscopy image. The PVA-assisted sample shows a discharge capacity of 120, 110, and 96 mAh g−1 at 1 C, 20 C, and 50 C, respectively; however, the sample without PVA exhibits a lower discharge capacity. Based on the analysis of electrochemical impedance spectroscopy, the lithium ion diffusion coefficients of Li3V2(PO4)3/C and PVA-assisted Li3V2(PO4)3/C are 4.19 × 10−9 and 4.99 × 10−8 cm2 s−1, respectively. In summary, it is demonstrated that using PVA as a template can obtain flake-like morphology and significantly improve the comprehensive electrochemical performances of Li3V2(PO4)3/C cathode material.