Cationically Substituted Bi_0.7Fe_0.3OCl Nanosheets as Li Ion Battery Anodes

Cation substitution of Bi 3+ with Fe 3+ in BiOCl leads to the formation of ionically layered Bi 0.7 Fe 0.3 OCl nanosheets. The synthesis follows a hydrolysis route using bismuth(III) nitrate and iron(III) chloride, followed by postannealing at 500 °C. Room temperature electrical conductivity improves from 6.11 × 10 –8 S/m for BiOCl to 6.80 × 10 –7 S/m for Bi 0.7 Fe 0.3 OCl. Correspondingly, the activation energy for electrical conduction reduces from 862 meV for pure BiOCl to 310 meV for Bi 0.7 Fe 0.3 OCl. These data suggest improved charge mobility in Bi 0.7 Fe 0.3 OCl nanosheets. Density functional theory calculations confirm this behavior by predicting a high density of states near the Fermi level for Bi 0.7 Fe 0.3 OCl. The improvement in electrical conductivity is exploited in the electrochemical performance of Bi 0.7 Fe 0.3 OCl nanosheets. The insertion capacity of Li + ions shows an increase of 2.5×, from 215 mAh·.g –1 for undoped BiOCl to 542 mAh·g –1 for Bi 0.7 Fe 0.3 OCl after 50 cycles at a current density of 50 mA·g –1 . Thus, the direct substitution of Bi 3+ sites with Fe 3+ in BiOCl results in nanosheets of an ionically layered ternary semiconductor compound which is attractive for Li ion battery anode applications.