Study on the Electrochemical Properties of Fe2 O 3 ‐ TiO2 Films Prepared by Sol‐Gel Process

Transparent Fe 2 O 3 ( 1 − x ) ‐ TiO 2 ( x ) ( x = 0, 0.3, 0.5, 0.6, 0.7, 0.8, and 0.9 in molar fraction) thin films on indium‐tin oxide (ITO)/glass substrates were made by sol‐gel dip‐coating. The iron‐ion‐containing sols were prepared from Fe ( NO 3 ) 3 ⋅ 9 H 2 O and Ti ( OC 4 H 9 ) 4 precursors. The electrochemical investigation of the Li + ion storage process in Fe 2 O 3 ‐ TiO 2 films has been made in a Pt / LiClO 4 ‐ PC ( 1 M ) / Fe 2 O 3 ‐ TiO 2 / ITO cell between −1.5 and 1.0 V potential range vs. saturated calomel electrode (SCE). The total electric charge inserted and extracted during a cycle has been determined by the cyclic voltammetry. The electric charge transition ability is mainly influenced by the composition and thickness of films, heat‐treatment temperature, and the precursor concentration of sols. In a pure iron oxide system, amorphous Fe 2 O 3 exhibited better Li+ ion storage behavior than α‐ Fe 2 O 3 phase. In the Fe 2 O 3 ‐ TiO 2 composite systems, Fe 2 O 3 ( 0.3 ) ‐ TiO 2 ( 0.7 ) films showed the best reversibility of the insertion‐deinsertion process while their maximal Q/d value is about 0.12 mC cm −2 nm −1 .