Li3V(2-2x/3)Mgx(PO4)(3)/C (x = 0, 0.15, 0.30, 0.45) composites have been synthesized by the sol-gel assisted solid state method, using adipic acid C6H10O4 (hexanedioic acid) as carbon source. The particle size of the composites is similar to 1 mu m. During the pyrolysis process. Li3V(2-2x/3)Mgx(PO4)(3)/C network structure is formed. The effect of Mg2+ doped on the electrochemical properties of Li3V2(PO4)(3)/C positive materials has been studied. Li3V1.8Mg0.30(PO4)(3)/C as the cathode materials of Li-ion batteries, the retention rate of discharge capacity is 91.4% (1 C) after 100 cycles. Compared with Li3V2(PO4)(3)/C, Li3V(2-2x/3)Mgx(PO4)(3)/C composites have shown enhanced capacity and retention rate capability. The long-term cycles and ex situ XRD tests disclose that Li3V1.8Mg0.30(PO4)(3) exhibits higher structural stability than the undoped system. (C) 2010 Elsevier B.V. All rights reserved.