In this work we studied the possibility of using Fe+6 "super iron" compounds, including BaFeO4, K2FeO4, CuFeO4, and SrFeO4 as potential cathode materials for rechargeable Li batteries, and their behavior in several nonaqueous Li salt solutions. Classic electrochemical techniques, such as cyclic voltammetry and chronopotentiometry combined with X-ray photoelectron spectroscopy, X-ray diffraction, Mossbauer spectroscopy, atomic adsorption, atomic emission, in situ and ex situ atomic force microscopy imaging, and diffuse reflectance Fourier Transform infrared spectroscopy were used in order to obtain a full picture of the electrochemical behavior of these compounds. Fe6+ compounds such as K2FeO4 and BaFeO4 are reduced in the presence of Li ions to Fe3+ compounds. Fe2O3, Li2O, and K2O or BaO are formed in amorphous or nanocrystalline structures. The reaction is partially reversible, i.e., Fe6+ compounds can be reformed by oxidation. The mechanisms of the lithiation-delithiation of these systems and what limited their reversibility are discussed. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.2128121] All rights reserved.