Synthesis and Characterization of a Multi-Layer Core-Shell Composite Cathode Material LiVOPO4-Li3V2(PO4)3

Abstract

A novel multi-layer core-shell composite cathode material LiVOPO4-Li3V2(PO4)3 was synthesized by calcining Li3V2(PO4)3 at 350°C for 2 h in the air atmosphere. The XRD results indicate the triclinic type LiVOPO4 and the monoclinic Li3V2(PO4)3 co-exist. XPS results reveal that the valence states of V in external surface area and the internal surface area of the sample are +4 and +3, respectively. HRTEM results indicate the sample has a multi-layer core-shell structure, the external shell is amorphous carbon, the internal shell of the sample is LiVOPO4, and the core is Li3V2(PO4)3. The initial discharge capacity of LVOP-LVP at the current density of 45 mA g−1 is about 132.8 mAh g−1, and the discharge capacity is about 126.8 mAh g−1 after 100 cycles. The cell retains 95.5% of its initial discharge capacity. The electrochemical performance is much better than that of bare LiVOPO4.