New Li+ ion-conducting ormolytes

Abstract

The preparation and characterization of two new families of lithium-conducting solid-state electrolytes is reported. Both systems are silica (SiO2) - polyethyleneglycol (PEGn) hybrid materials with (type I) or without (type II) covalent organic-inorganic chemical bonds. Their electrical conductivity has been studied by complex impedance spectroscopy between 20'°C and 100'°C in the frequency range 1 Hz to 10 MHz as a function of the polymer chain length (200 < n < 1900), polymer concentration and lithium concentration (4 < [O]/[Li] < 80). The highest room-temperature ionic conductivity (&sigma;&#8773; 6 x 10-2 S cm-1) has been found for type II material for ratios [O]/[Li] = 15 and PEG300/TEOS = 1.0. The effect of the chain length on the polymer mobility has been studied by nuclear magnetic resonance by measuring the Li+ line widths and the spin-lattice relaxation time T1 between -100'°C and + 100'°C, The bonded chain mobility increases with the chain length (type II) while the opposite occurs with unbonded chain material (type I). Both types of materials present high ionic conductivity at room temperature and are adequate as Li+-conducting electrolyte in all solid-state electrochemical devices.