Physical properties and battery performance of novel two-phase ion-conducting gels

Mixtures containing liquid electrolyte and alpha,omega-alkane diacrylates were produced. Upon polymerization two-phase gels consisting of polymer-rich and polymer-poor phases were obtained. The structure and the properties of the gels were studied using nuclear magnetic resonance, complex impedance spectroscopy, and electron microscopy. Conductivity data of various mixtures before and after polymerization were fitted to a master curve using a modified free-volume theory. Low interaction between the polymer and the lithium ions in these gels ensures that the transport number for lithium is independent of the polymer concentration in various systems. Lithium metal batteries were constructed in which the two-phase gels performed a dual function as an ion conductor as well as a separator. The gel morphology was found to be very important in determining the performance of such batteries. By optimizing the morphology of the gels, internal short-circuiting could be prevented, and lithium metal cycling efficiencies in excess of 95% could be obtained. (C) 1999 The Electrochemical Society. S0013-4651(98)10-107-6. All rights reserved.