Cationically Substituted Bi<sub>0.7</sub>Fe<sub>0.3</sub>OCl Nanosheets as Li Ion Battery Anodes

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