טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentTel-Vered Ran
SubjectEnhanced Fe(VI) Electrochemical Energy Storage
DepartmentDepartment of Chemistry
Supervisors Professor Emeritus Chaim Yarnitzky (Deceased)
Mr. Stuart Licht


Abstract

This work presents a variety of compounds, based on iron in an unusual Fe(VI) valence state, and possessing a number of attractive characteristics for cathodic applications. Novel synthethic in-situ and ex-situ methods for the electrochemical preparation of BaFeO4 were developed, allowing a simpler synthetic approach, high product purity (94-96%) and avoiding the use of strong oxidizing agents. The work studies the influence of cell configuration, electrolyte composition and concentration, applied current density, cell internal temperature, membrane type, counter electrode effects, reactants molar ratio, synthesis duration and scaling up, on the electrochemical synthesis. The high purity product was analyzed by a variety of analytical techniques: XRD, FTIR, ICP, UV/Vis spectroscopy, EDS, SEM, BET, Chromite redox titration and constant external load discharges vs. lithium and zinc anodes. The enhanced thermal stability of the in-situ electrochemically synthesized BaFeO4 was explained by several bulk and surface impurities which inhibit the rate of thermal decomposition.

            The improved Fe(VI) electrochemical storage properties were then investigated versus lithium anodes in organic environments. Primary Li/Fe(VI) batteries were assembled and the performance dependence on Fe(VI) composition, discharge external resistance, conductive additives, electrolyte composition (solvents and supporting salts), cathode particle size, discharge temperature and Fe(VI)/MnO2 co-cathodes was probed. Under optimal conditions, Li/Fe(VI) batteries exhibit a substantial improvement in the gravimetric capacity over commercial Li/MnO2 cells, approach ~100% coulombic efficiency, and are discharged as environmentally benign products.