Influence of Solvent Evaporation Rate in the Preparation of Carbon-Coated Lithium Iron Phosphate Cathode Films on Battery Performance

In this work, the drying step for cathodes based on carbon-coated LiFePO4 prepared in the temperature range of 60-120 degrees C has been investigated in detail. The microstructure of the cathode shows a homogeneous distribution of the active material and conductive additive particles independent of the drying temperature. However, the results of impedance spectroscopy and cycling voltammetry are affected by the drying temperature. The solvent evaporation temperature, therefore, affects the polymer binder distribution and its characteristics, which include the polar phase content of the polymer and its affinity with the other components of the cathode. The discharge capacity value after 50 cycles is 120 and 81 mAhg(-1) for the samples dried at 80 and 60 degrees C, respectively, which show the best and worst battery performance, respectively. It was concluded that carbon-coated LiFePO4 cathodes should be prepared at drying temperatures between 80 and 100 degrees C for optimized performance.