On the preparation of multifunctional conversion coatings of FePO4/LiFePO4

Abstract

This research aims to take advantage of the properties of phosphate coatings to overcome the problems inherent in using LiFePO4 as a powder. LiFePO4 coatings have been prepared on iron sheets using cyclic voltammetry in an aqueous solution of H3PO4 and LiOH. The voltammograms evolved from the initial active-passive behaviour, typical for iron in H3PO4 solution, to a reversible redox behaviour upon cycling. The resulting coating was characterised morphologically (via SEM and optical microscopies), chemically (via XPS) and electrochemically (via EIS and SECM). The results showed a two-layered coating (a porous outer layer and a compact inner layer) with the behaviour of a porous electrode that reversibly exchanges Li+ ions with the environment and reduces the emission of ionic species (Fe2+, Fe3+) as its thickness increases.