Optimisation of some parameters for the preparation of nanostructured LifePO4/C cathode

LiFePO4/C powders have been synthesised by an easy and inexpensive mild hydrothermal method in the presence of an organic surfactant compound [hexadecyltrimethylammonium bromide (CTAB)] previously developed. The samples have been synthesised with different amounts of CTAB, and the effect of this parameter on their structural characteristics and electrochemical behaviour has been investigated. The processing of the high-resolution diffraction data in a Rietveld refining analysis and the HRTEM observations, previously not available, has put in evidence the high purity of the samples prepared and the good quality of the carbon layer covering the grains. Such layer, obtained during the firing step of the preparation in N-2 atmosphere, is very important to enhance the electronic conduction of the electrode. The sample high purity and the conduction enhancer carbon layer, along with the low grain size and high surface area, properties already put in evidence, are obtained to the maximum degree only for a sample prepared with a certain quantity of surfactant. The investigations on samples with very low and with the maximum CTAB content found out the best performing sample confirming the previous results.