Electrochemical studies on LiFe_(1-x)Co_xPO_4/carbon composite cathode materials synthesized by citrate gel technique for lithium-ion batteries

摘要

LiFePO_4/carbon and LiFe_(1-x)Co_xPO_4/carbon (x = 0.02,0.04,0.08 and 0.1) composite cathode materials were synthesized by citrate gel technique. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to study the phase and morphology of un-doped and Co doped lithium iron phosphate/carbon composites. The SEM images revealed that the particles were agglomerated and the particle sizes were almost homogeneously distributed. The particle size was found to be between 200 and 300 nm from transmission electron microscopy. Cyclic voltammetric studies were taken to investigate the electrochemical performance of the prepared composite materials. The high intensity of the anodic and cathodic peaks indicates that Li-ions and electrons were participating actively in redox reactions due to the carbon coating. Charge/discharge studies carried out on a CR2032 coin cell revealed that the carbon coated LiFePO_4/carbon composite exhibited an improved discharge capacity of 157 mAh/g at low rates. We found that cobalt doping does not have a favourable effect on the electrochemical performance of lithium iron phosphate cathode materials.