Synthesis and characterization of olivine phosphate cathode material with different particle sizes for rechargeable lithium-ion batteries

• A facile method for the synthesis of LiFePO4 with different particle sizes.
• The consequences of phonon confinement are discernible in the vibrational spectra of LiFePO4.
• The variation of the optical band gap and dc electrical conductivity with particle size is due to the size effect.

A different solid state preparation of undoped cathode material LiFePO4 (LFP) olivine compound has been synthesized at low temperatures with an emphasis toward understanding the size dependent structural and transport properties. The phase purity, size and structural properties of as prepared sample have been characterized by various analytical techniques. These studies confirm that the obtained LFP of different particle sizes are without any secondary phases. Additionally, the spectroscopic studies on these samples reveal that the observed vibrational modes are characteristic part of LFP samples and the consequences of phonon confinement are discernible when the particle size becomes less than 200 nm. We substantiate that the measured optical band gap and electronic conductivity are the intrinsic part of LFP samples. The room temperature electronic conductivity and optical band gap shows the systematic dependence on particle size. We ascribe the variation of the optical band gap and dc electronic conductivity with particle size is due to the quantum confinement effects.