Electrochemical properties of Li3-xNaxV2-xTix(PO4)3/C cathode materials in lithium ion batteries

• We synthesize Li3-xNaxV2-xTix(PO4)3/C via a sol–gel method.
• Na and Ti doping facilitate the diffusion of lithium ion in the lattice.
• Cycling performance and ionic conductivity are improved by doping the elements.

Li3-xNaxV2-xTix(PO4)3/C (x = 0, 0.01, 0.03, 0.05, and 0.07) have been prepared via a conventional sol–gel method. X-ray diffraction patterns indicate that Li3-xNaxV2-xTix(PO4)3/C are successfully obtained with a monoclinic structure. X-ray photoelectron spectroscopy has been performed to investigate the valence states of the doped elements. The morphologies of Li3-xNaxV2-xTix(PO4)3/C are investigated by field emission scanning electron microscopy. Li2.97Na0.03V1.97Ti0.03(PO4)3/C exhibits the highest electrochemical properties among all the samples. It delivers an initial discharge capacity of 170.61 mAh g−1 and capacity retention of 72.66% after 100 cycles, while the uncoated Li3V2(PO4)3/C only delivers an initial discharge capacity of 164.08 mAh g−1 and capacity retention of 71.59% in the voltage range of 3.0–4.8 V. In addition, the results of cyclic voltammetry and galvanostatic intermittent titration technique ensure that the ionic conductivity of Li2.97Na0.03V1.97Ti0.03(PO4)3/C is increased compared with the uncoated Li3V2(PO4)3/C.