Polymer gel combustion synthesis of LiFePO4/C composite as cathode material for Li-ion battery

LiFePO4/C has been synthesized by polymer gel combustion method. Of aniline monomer, 0.5 and 1.0 ml were used for the different amount of gel formation. The particle sizes of LiFePO4/C composites designated as lithium iron phosphate (0.5) (LFP(0.5)) and LFP(1.0) were estimated as similar to 400 and similar to 100 nm for the powders synthesized with 0.5 and 1.0 ml of monomers, respectively. The final particle size of the LiFePO4/C depends on the initial monomer content used in the synthesis process. Thicknesses of carbon coating on the particles of LFP(0.5) and LFP(1.0) powders, as revealed by TEM observation, are similar to 3 and similar to 7 nm, respectively. The sample LFP(1.0) delivers discharge capacities of 72 and 60 mAh g(-1) which are higher than those of LFP(0.5) at fast discharging rates of 5 and 10 C. The higher rate capability of sample LFP(1.0) was due to small particle size, low charge transfer resistance, and higher Li+ diffusion coefficient as compared to LFP(0.5).