Nanosized FeF3·0.33H2O as Cathode Material for High-Performance Li-Ion Batteries

Conversion-type lithium–metal fluoride batteries with high energy density, are considered to be very promising candidates for the next generation of low-cost lithium-ion batteries. Unfortunately, metal fluoride cathodes generally suffer from poor conductivity, sluggish reaction kinetics, and irreversible structural changes. Reducing particle size to nanoscale is an effective way to solve the large volume change and poor electronic conductivity of metal fluoride cathodes. In this study, a nano-control strategy was proposed, using n-propanol as an auxiliary solvent to achieve the conversion of micrometer-scale FeF3·3H2O to nanoscale FeF3·0.33H2O. Meanwhile, the particle size and morphology of iron fluorides could be controlled by regulating the synthesis temperature. The distribution of relaxation times (DRT) was used to analyze the electrochemical impedance spectroscopy (EIS). FeF3·0.33H2O synthesized at 180 °C with lower resistance showed a high capacity of 200 mAh g−1 after 160 cycles with excellent rate performance and cycle stability.