Preparation and Characterization of Chlorine Doped Li3V2(PO4)(3) as High Rate Cathode Active Material for Lithium Secondary Batteries

Abstract

Monoclinic Li3V2(PO4)(2).Cl-99(0.01) was synthesized using the conventional solid state method and the X-ray diffraction pattern was indexed based on P2(1)/n space group. The sharp cyclic voltammetric curves clearly revealed three lithium extraction/insertion processes at approximately 3.64, 3.72, 4.13, and 4.58 V during the anodic scan and 3.96, 3.58, and 3.48 V during the cathodic scan. Charge/discharge studies showed reduced electrolyte decomposition contribution in the case of the chlorine doped Li3V2(PO4)(2.99)Cl-0.01 sample with an initial capacity of 176 mA h g (1) at a 0.1 C current rate. The chlorine doped Li3V2(PO4)(3) sample showed an increased capacity retention with an increase in current rate, even at a very high C-rate (20 C), than the pristine and carbon coated samples. The pristine and carbon coated Li3V2(PO4)(3) samples showed a lower capacity retention of 71% and 84%, respectively, at a current rate of 0.1 C. In contrast, the chlorine doped Li3V2(PO4)(3) sample retained 87% of the initial capacity (176 mA h g(-1)) at the same current rate but with a higher coulombic efficiency of 91%. The enhanced capacity retention for the chlorine doped Li3V2(PO4)(3) was attributed to the reduction in polarization and decreased charge transfer resistance of the electrode.