ELECTROCHEMICAL STUDIES ON THE SYNTHESIS AND CHARACTERIZATION OF LITHIUM AND VANADIUM AND CHROMIUM PHOSPHATE COMPOUNDS

The use of monodiphosphate compounds as renewable sources of energy as positive (cathode) material for lithium-ion batteries (LIB) is considered a great target. Lithium vanadium chromium monodiphosphate (LVCPP)Li9V2.8Cr0.2(P2O7)3(PO4)2 and the Na-doped:Li8.75Na0.25V2.8Cr0.2(P2O7)3(PO4)2 (LNVCPP) compounds have been prepared by using the sol-gel method. The prepared materials are characterized by XRD, FESEM, and EDX. The XRD data is indicated the presence of a single-phase of Li9V2.8Cr0.2 (P2O7)3(PO4)2 and Li8.75Na0.25V2.8Cr0.2(P2O7)3(PO4)2 with trigonal structure. Both cycle performance and rate capability have shown improvement with moderate Na doping content. Li9V2.8Cr0.2(P2O7)3(PO4)2 and Li8.75Na0.25V2.8Cr0.2(P2O7)3(PO4)2 compounds presented the good electrochemical rate and cyclic ability. The cell is prepared with x=0.25 delivered a specific discharge capacity of 50 mAhg-1 after 35 cycles in comparison with the other sample. The enhancement of the rate and cyclic capability may be attributed to the optimizing particle size, morphologies, and structural stability with the proper amount of Na-doping (x =0.25) in Li sites.