Electrochemical performance of Al-substituted Li_3V_2(PO_4)_3 cathode materials synthesized by sol-gel method

The effect of Al-substitution on the electrochemical performances of Li3V2(PO4)3 cathode materials was studied. Samples with stoichiometric proportion of Li3AlxV2-x(PO4)3 (x=0, 0.05, 0.10) were prepared by adding Al(NO3)3 in the raw materials of Li3V2(PO4)3. The XRD analysis shows that the Al-substituted Li3V2(PO4)3 has the same monoclinic structure as the un-substituted Li3V2(PO4)3. The SEM images show that Al-substituted Li3V2(PO4)3 has regular and uniform particles. The electrochemical measurements show that Al-substitution can improve the rate capability of cathode materials. The Li3Al0.05V1.95(PO4)3 sample shows the best high-rate performance. The discharge capacity at 1C rate is 119 mA-h/g with 30th capacity retention rate about 92.97%. The electrode reaction reversibility and electronic conductivity are enhanced, and the charge transfer resistance decreases through Al-substitution. The improved electrochemical performances of Al-substituted Li3V2(PO4)3 cathode materials offer some favorable properties for their commercial application.