Synthesis and Modeling of Polysiloxane-Based Salt-in-Polymer Electrolytes with Various Additives

Karatas Y, Banhatti RD, Kaskhedikar N, Burjanadze M, Funke K, Wiemhoefer H

Research article (journal) | Peer reviewed

Abstract

The effect of both nanoparticles and low molecular weight borate esters on the ionic conductivity of cross-linked polysiloxanes was systematically investigated by means of measuring conductivity spectra in the impedance regime at temperatures between -30 and 90 degrees C. Salt-in-polymer electrolytes were prepared by dissolving lithium triflate (LiSO(3)CF(3)) in comblike polysiloxanes bearing one methyl and one oligoether side group per silicon. An amount of 10 mol % of the oligoether side groups exhibited a terminal allytrimethoxysilane serving as a cross-linker moiety (T(0.1)OPS). Thus prepared polymer electrolyte membranes were completely amorphous and mechanically stable with an optimum conductivity value of 5.7 x 10(-5) S x cm(-1) at 15 wt % of lithium triflate (LiSO(3)CF(3)) at room temperature (T(0.1)OPS + 15 wt % LiSO(3)CF(3)). Further investigations concerned the influence of additives, i.e., nanosized ceramic fillers (alpha-Al(2)O(3) and SiO(2), up to 10 wt %) as well as two low molecular weight borate esters (tris(2-(2-methoxyethoxy)ethyl) borate (B2) and tris(2-(2-(2-methoxyethoxy)ethoxy)ethyl) borate (B3)) with maximum concentrations of 40 wt % as referred to polysiloxane T(0.1)OPS. The addition of borate esters resulted in a considerable increase of the conductivity, while still maintaining the mechanical stability. Optimum conductivities of 3.7 x 10(-5) and 1.6 x 10(-4) S x cm(-1) were measured for B2 and B3, respectively, at room temperature. A fit of the temperature-dependent DC conductivity by the empirical Vogel-Tammann-Fulcher (VTF) equation showed that there was an increased number density of mobile charge carriers in the case of borate esters as additives. However, the shape of the conductivity spectra in the dispersive regime changed considerably in going from nanoparticles as additives to borate esters. A careful and consistent modeling of the conductivity spectra and of the temperature dependence of the DC conductivity was done within the framework of the MIGRATION concept. The result was that the addition of borate esters to the polymer host most probably increased both number density of mobile charge carriers as well as their mobility.

Details about the publication

JournalJournal of Physical Chemistry B (J. Phys. Chem. B)
Volume113
Issue47
Page range15473-15484
StatusPublished
Release year2009 (21/10/2009)
DOI10.1021/jp907832q
KeywordsPEG-BORATE ESTER; OLIGO(OXYETHYLENE) SIDE-CHAINS; LITHIUM BATTERY ELECTROLYTES; ION-TRANSPORT PROPERTIES; LEWIS-ACID; DISORDERED STRUCTURES; GEL ELECTROLYTES; MG-SALT; ELECTROCHEMICAL PROPERTIES; RECHARGEABLE BATTERIES

Authors from the University of Münster

Banhatti, Radha Dilip
Institute of Physical Chemistry
Burjanadze, Marina
Institute of Inorganic and Analytical Chemistry
Wiemhöfer, Hans-Dieter
Professorship of Inorganic Chemistry (Prof. Wiemhöfer)