Preparation and electrochemical performance of Na-doped Li3V2(PO4)3/C cathode material

摘要

Na-doped Li 3V _2(PO _4) _3/C (LVP/C) cathode materials are prepared by a sol-gel method. X-ray diffraction results show that the Na ion has been well doped into the crystal structure of LVP/C and does not disturb the extraction-insertion behavior of lithium ion seriously. The initial discharge capacity of the Na-doped LVP/C is 112.2 mA h g ~(-1) at 5 C, and the capacity retention reaches 98.3% over 80 cycles. Cyclic voltammetry and electrochemical impedance spectra indicate that the reversibility of electrochemical redox reaction and the charge-transfer resistance of LVP/C cathode material have been significantly improved by Na doping. The improved performances can be attributed to the more convenient route for lithium ion diffusion and the lower activation energy of the extraction-insertion of lithium ion due to the weakness of Li-O bond.