Size and shape-tuned LiFePO4 nano-platelets were prepared by the polyol process to examine the effect of their microstructure on their electrochemical performance when coated by a thin carbon layer. The materials were characterized by X-ray diffraction, scanning and transmission electron microscopy, magnetic susceptibility, Fourier transform infrared and Raman spectroscopy. The crystallinity, as well as the size of the particles, depends on the nature of the solvent that is used, and also on the rate of dilution. The electrochemical properties emphasize the role of antisite defects and the coherence length along the b-axis, i.e. along the Li channels. With an optimized choice of the synthesis parameters, the results showed that the orthorhombic olivine structure is retained even in crystals of few nanometers in width, a free of impurities. The high crystalline quality of the particles obtained in these optimized conditions lead to a good electrochemical performance of the nanocomposite C-LiFePO4 product as a cathode material for lithium-ion batteries, with a capacity 151mAhg−1 at low C-rate, despite the presence of residual adsorbed polyol species that are found to be insulating.