Mo-doped Li3V2(PO4)3/C cathode material with high rate capability and long term cyclic stability
By Yuan, Wei; Yan, Ji; Tang, Zhiyuan; Sha, Ou; Wang, Jinmei; Mao, Wenfeng & Ma, Li
Published in Electrochimica Acta
2012
Abstract
Mo-doped Li3MoxV2-x(PO4)3/C (x = 0, 0.01, 0.02, 0.03 and 0.04) are prepared through a fast sol–gel method. The X-ray diffractometer, scanning electron microscopy and high-resolution transmission electron microscopy are employed to characterize the prepared materials, and the evidences show that Mo element have been successfully incorporated into the Li3V2(PO4)3 lattice. The Li3Mo0.03V1.97(PO4)3/C composite exhibits the most excellent electrochemical performance among all the samples. In the potential range of 3.0–4.3 V, Li3Mo0.03V1.97(PO4)3/C exhibits the discharge capacities of 125.0 mAh g-1 and 122.8 mAh g-1 at 5C and 10C rates, respectively. A capacity of 117.6 mAh g-1 is still delivered at 20C rate after 150 cycles with a capacity retention of 93.6%. In addition, the electrochemical impedance spectroscopy test proves that the electronic conductivity of Li3Mo0.03V1.97(PO4)3/C is decreased, while the lithium ion conductivity is increased compared with the un-doped one. Based on above results, we conclude that the solid state diffusion of lithium ions is the rate-determining step of the extraction/insertion process.