Electrical and electrochemical characterization of nano-sized LiFePO4 cathode materials synthesized by a lauric acid-based sol--gel method

We synthesized pure LiFePO$_{4}$ and C-LiFePO$_{4}$ nanoparticles by sol-gel technique. Carbon coating was accomplished by including Lauric acid in the sol-gel precursor solution. Three C-LiFePO$_{4}$ samples of particle sizes 29, 27, 23 nm, were prepared by varying lauric acid concentration in the precursor solution. All the samples were characterized by X-ray diffraction, Raman, conductivity, and electrochemical measurements. The micro-Raman measurements showed two major bands at 1350 and 1590 cm$^{-1}$ respectively (I$_{D}$/I$_{G})$ and the electronic conductivity were found to depend strongly on the amount of surfactant coverage. The 23 nm particle size sample showed minimum (D/G) band ratio and the maximum electrical conductivity among the three samples. The measured value of the capacity for 23 nm sized sample, $\sim $ 170 mAh/g, approached the theoretical capacity limit value for LiFePO$_{4}$