Effect of texture on the electrochemical properties of LiFePO4 thin films

Carbon-free in situ crystallized LiFePO4 thin films were grown using the Pulsed Laser Deposition (PLD) technique. Adjusting the deposition time enabled the growth of films with different thicknesses. Comparing the properties of these films ((120) preferentially oriented) highlighted a relationship between microstructure and electrochemical activity. However, whatever film thickness (from 12 nm to 600 nm), the capacities recorded were far from the ones expected, since only a small percentage of the film was found to really chemically or electrochemically react. Simple experiments (creation of surface defect, metal electrodeposition, AC/DC conductivity measurements, etc.) carried out on these films gave a new insight into the origin of the limitations. The results presented herein singularly lead to the conclusion that the ionic conductivity is the main limitation for such olivine-type thin films.