Synthesis and electrochemical properties of Al-doped LiVPO4F cathode materials for lithium-ion batteries

Al-doped LiVPO4F cathode materials LiAlxV1-xPO4F were prepared by two-step reactions based on a carbothermal reduction (CTR) process. The properties of the Al-doped LiVPO4F were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. XRD studies show that the Al-doped LiVPO4F has the same triclinic structure (space group p1) as the undoped LiVPO4F. The SEM images exhibit that the particle size of Al-doped LiVPO4F is smaller than that of the undoped LiVPO4F and that the smallest particle size is only about 1 μm. The Al-doped LiVPO4F was evaluated as a cathode material for secondary lithium batteries, and exhibited an improved reversibility and cycleability, which may be attributed to the addition of Al3+ ion by stabilizing the triclinic structure.