Electrochemical reactions and cathode properties of Fe-doped Li2O for the hermetically sealed lithium peroxide battery

Fe-doped Li2O (FDL) is synthesized mechanochemically and is demonstrated as a new Co-free cathode material for use in sealed Li2O2 batteries, which have been proposed as high energy density batteries. Fe3+ ions are substitutionally doped into the Li sites in an antifluorite-type Li2O structure to create FDL. The FDL consists of (Li0.82Fe0.06)(2)O (d-FDL) and high -temperature form of Li5FeO4 (o-FDL), in which Fe3+ ions disorderly and orderly arranged, respectively. According to the Mossbauer spectra and quantitative peroxide species analysis, the FDL cathode operates principally based on the redox reaction between O-2(2-) and O2-. X-ray diffraction study reveals that the reversible formation of O-2(2-) proceeds mainly in the d-FDL. An irreversible side reaction involving the evolution of oxygen gas occurs when the cathode is charged to more than 250 mAh g(-1). The FDL (Fe/(Li + Fe) = 10 at%) cathode exhibits a reversible capacity of 200 mAh g(-1) over 200 cycles at a current density of 22.5 mA g(-1). (C) 2016 Elsevier B.V. All rights reserved.