Influence of solvent evaporation rate during C-LiFePO4 cathode film preparation on lithium-ion battery performance

Abstract

In this work, the drying step for C-LiFePO4 based cathodes prepared in the temperature range between 60 and 120 ºC has been investigated in detail. The microstructure of the cathode shows an homogeneous distribution of the active material and conductive additive particles independently of the drying temperature. On the other hand, impedance spectroscopy and cycling voltammetry are affected by the drying temperature. Solvent evaporation temperature affects therefore polymer binder distribution and its characteristics, including the polar phase content of the polymer and the affinity with the other components of the cathode. The discharge capacity value after 50 cycles is 120 mAh.g-1 and 81 mAh.g-1 for the samples dried at 80 ºC and 60 ºC, that show the best and worse battery performance, respectively. It was concluded that C-LiFePO4 cathodes should be prepared at drying conditions between 80 ºC and 100 ºC for optimized performance.