A first attempt has been made to prepare Li3MxV2−x(PO4)3/C (M=Fe, Co) composite solutions by adopting a novel oxalic dihyrazide assisted combustion (ODHAC) method. The pillaring effect of Fe in Li3FexV2−x(PO4)3/C and the possible electrochemical activity of the Co3+/4+ redox couple of Li3CoxV2−x(PO4)3/C at a 4.8 V limit increases the structural and cycling stability of the native Li3V2(PO4)3/C cathode respectively, thereby ultimately improving the electrochemical behaviour of Li3MxV2−x(PO4)3/C solid solutions. An extended solubility limit of x = 0.10 for Fe dopant has been achieved for the first time through the present study against the reported value of x = 0.05 in Li3FexV2−x(PO4)3/C compounds. The study demonstrates the suitability of the ODHAC synthesis approach in preparing a wide variety of phase pure Li3MxV2−x(PO4)3/C cathodes. Further, the superiority of Li3Co0.10V1.90(PO4)3/C in exhibiting the highest capacity (178 mAh g−1) and negligible fade (4%) and the demonstrated cyclability under the influence of 10 C rate has been understood as a function of the synergistic effect of the ODHAC synthesis method and the optimum concentration of Co dopant chosen for the study.