Composite electrolytes from self-assembled colloidal networks

Abstract

In this study, we present two approaches to developing composite electrolytes exploiting the self-assembling nature of colloidal fillers. The first system comprises of oligomers of poly(ethylene glycol) dimethyl ether, branched fumed silica particulates and lithium salt. The fumed silica forms a three-dimensional, self-supporting network that provides mechanical stability. The large pores of the network has little effect on diffusivity of ions and oligomers, lithium transference number and ionic conductivity, with the latter showing values >10 −3 S/cm at ambient conditions. The second system consists of Li exchanged hectorite clay in a mixture of low molar mass carbonates. Similar to the fumed silica, the clay provides mechanical stability through formation of a three-dimensional network. In addition, the immobile clay platelets also serve as the anion rendering the system to be a single ion conductor. Near-unity transference number is observed in this case. However, the room temperature conductivity of the clay composite is lower than the fumed silica, revealing a value of about 10 −4 S/cm. The lower conductivity can be attributed to the clay not being in a fully exfoliated form as evident from morphological analysis.