Effect of Heat Treatment on Charge-Discharge Property of Fluoride Cathode Materials for Li ion secondary batteries.

摘要

Iron fluoride(III) anhydrate fine particle was prepared by drying in vacuum from FeF_3-3H_2O, a mechanical milling process and a calcination at 473 - 773 K. Particle size of FeF_3-3H_2O was ca. 3 - 5 μm and that of FeF_3 anhydrate was 100 - 500 nm after drying and milling. FeF_3 sample only after drying and milling was hygroscopic and became FeF_3-3H_2O under atmosphere. FeF_3 became stable under atmosphere after oxidation at 673 K for more than 20 minutes. It was found that Fe_2O_3 was produced by calcination and covered the surface of FeF_3 particles. In Charge-discharge measurements, the discharge capacity of these FeF_3 samples was 150 - 200 mAh/g at a discharge rate of 0.1 C. The oxidation could improve the discharge properties of FeF_3 cathode.