Iodide-conducting polymer electrolytes based on poly-ethylene glycol and MgI sub(2: Synthesis and structural characterization)

• Published in: Electrochimica acta Vol. 57; pp. 112 - 122
• Main Authors: Vittadello, Michele, Waxman, David I, Sideris, Paul J, Gan, Zhehong, Vezzu, Keti, Negro, Enrico, Safari, Ahmad, Greenbaum, Steve G, Di Noto, Vito
• Format: Journal Article
• Language: English
• Published: 15.12.2011
• Subjects: Conductivity; Electrolytes; Magnesium; Nuclear magnetic resonance; Obstacles; Resistivity; Spectroscopy; Synthesis
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2011.07.133

A major obstacle for a viable technological development of dye sensitized solar cells (DSSCs) is still the synthesis of a high performance iodide-conducting polymer electrolyte. Here we present a series of eight electrolytic complexes with formula PEG1000/(MgI sub(2)) sub(x)(I sub(2)) sub(y) (0.0038 less than or equal to x less than or equal to 0.5801, 0 less than or equal to y less than or equal to 0.0636). The synthesis involves the preparation of a disordered form of MgI sub(2 by a metallorganic route, which enables us to dissolve high amounts of salt in the chosen polymer host. The thermal analysis of the resulting polymer electrolytes was performed using modulated differential scanning calorimetry measurements. Vibrational studies were carried out using medium FT-IR, far FT-IR and FT-Raman. The variation of the CO and OH stretching modes in the medium infrared, as a function of the mole-to-mole ratio n) sub(M)g/n sub(O, was investigated by Gaussian decomposition to provide insight into the polymer-polymer and salt-polymer interactions in these materials. The FT-Raman spectra confirmed and complemented the vibrational assignment. The conductivity study of these systems was performed by electrical spectroscopy in the frequency interval 10 mHz-10 MHz. The direct current conductivity ( sigma ) sub(D)C) profiles versus the reciprocal temperature exhibited a Vogel-Tamman-Fuelcher (VTF) behavior. The best sigma sub(DC at 50 degree C was 5 x 10) super(-)5 S cm super(-1. The overall results indicate the presence of bivalent, monovalent and neutral species, Mg) super(2)+, [MgI] super(+ and MgI) sub(2), respectively, which participate in the conduction process. These results are consistent with what was previously observed in PEG400-based systems doped with delta -MgCl sub(2. The presence of at least one Mg site containing a distribution in parameters was observed using ) super(2)5Mg solid state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The site has been assigned to a Mg complex involving the coordination by oxygen atoms of the polymer backbone.