Nanosized Amorphous Iron Oxyhydroxide for Reversible Lithium Intercalation

Abstract

An iron oxyhydroxide was synthesized via a low-temperature aqueous solution route and investigated as a lithium intercalation host. The chemical composition of the material was determined to be Na0.01Fe(OOH)0.99.Na0.01Fe(OOH)0.99. The material possessed a nanosized morphology and a nearly amorphous structure resembling α-FeOOH or the mineral goethite. It exhibited an open-circuit voltage (OCV) of 3.1 V vs. Li+/Li.Li+/Li. At a slow discharge rate of C/100 or 62 μA/cm262 μA/cm2 and between the OCV and 1.5 V, close to 0.9 Li per Fe was intercalated into the material, corresponding to a specific capacity of 260 mAh/g. This high intercalation capacity was almost completely reversible. At a high discharge rate of C/10 or 0.53 mA/cm2,0.53 mA/cm2, a specific capacity of 215 mAh/g was attained, indicating excellent rate performance. At the same time, the material exhibited nearly perfect capacity retention upon cycling over 30 cycles. These superior electrochemical properties are attributable to the nearly amorphous structure and nanosize morphology of the material, and point to the promise of intercalation hosts of unconventional, noncrystalline structures. At the same time, the results indicate that the hydroxide ions present in the material did not interfere with lithium intercalation, permitting nearly perfect reversibility of the intercalation process and excellent capacity retention upon cycling. © 2003 The Electrochemical Society. All rights reserved.