Li1+xFePO4 (x = 0 - 0.5) production from Fe3+ sources by glass-ceramic technique with different carbon sources and investigation of structural, thermal and electrochemical performance

Li1+xFePO4 (x=0 - 0.5) samples were successfully fabricated by the glass-ceramics technique with quenching from high temperatures. Thermal properties were analyzed by DTA, TG and the glass transition temperature, crystallization activation energy and Avrami parameters were calculated as 3.99 indicating that three dimensions of growth and one representing a constant nucleation rate. The XRD analysis shows that there are two-phase of LiFePO4 and Li3Fe2P3O12 which compete with each other according to increasing heat treatment temperatures. Glucose and ascorbic acid were used as the carbon source for increasing the conductivity of the powders during to crystallization process with different heating and cooling rates and it was found that the heating/cooling rates are effective for battery performance. The battery cells exhibit similar cycling voltammetry (CV) data with the undoped LiFePO4 battery cells. The charging/discharging cycles measurements for C/5- rate and C/20- rate for different environmental temperatures were made and it was found that the best capacity values for different carbon sources were obtained as 165.8 mAh/g and 169.9 mAh/g for using ascorbic acid and glucose addition, respectively. The environmental effect on the battery performance was investigated and the Li-diffusion rate depending on the temperature was calculated and it was found that the diffusion rate obtained from CV curves for 50 °C, room temperature, and 10 °C and the diffusion activation energy were found as 2.93 and 8.03 meV for glucose and ascorbic acid respectively.