Electrochemical performances of Li3V2-(4/3)xTix(PO4)3/C as cathode material for Li-ion batteries synthesized by an ultrasound-assisted sol–gel method

• An ultrasound-assisted sol–gel method was used to synthesize Li3V2-(4/3)xTix(PO4)3/C.
• PVDF is the carbon source to enhance the electro-conductivity.
• Li3V2-(4/3)xTix(PO4)3/C has better rate and cyclic performance when x = 0.03–0.06.
• Li3V1.92Ti0.06(PO4)3/C has Li+ diffusion rate of 4.39 × 10−5 cm2 s−1.

Cathode materials Li3V2-(4/3)xTix (PO4)3 (x = 0,0.03, 0.06, 0.09, 0.12) using Polyvinylidene Fluoride (PVDF) as carbon source are synthesized via an ultrasound-assisted sol–gel method. Ultrasound helps to a uniform dispersion of the water insoluble PVDF. X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that samples exhibit pure monoclinic structure and have similar morphology. Electrochemical galvanostatic charging/discharging results show that the capacities at low current density (less than 2C) of all samples are not that different. However, the discharge capacities and cyclic performance are improved at higher current density by a proper amount of Ti4+ doping (x = 0.03–0.06). The electrochemical performances become a bit worse when x is higher than 0.06. This may be attributed to the uniform lattice distortion caused by the overmuch dopant.

The capacity fading of Li3V2-(4/3)xTix (PO4)3/C becomes larger with increasing x, especially when the rate is more than 2C. Sample B and C (x = 0.03 & 0.06) have outstanding rate performance that their specific capacity excesses 100 mAh g−1 at 15C.Figure optionsDownload as PowerPoint slide