New Type of Li Ion Conductor with 3D Interconnected Nanopores via Polymerization of a Liquid Organic Electrolyte-Filled Lyotropic Liquid-Crystal Assembly

A new type of polymer electrolyte material for Li ion transport has been developed. This material is based on a polymerizable lyotropic (i.e., amphiphilic) liquid crystal (1) that forms a type-II bicontinuous cubic (QII) phase with the common liquid electrolyte, propylene carbonate (PC), and its Li salt solutions. The resulting cross-linked, solid−liquid nanocomposite has an ordered, three-dimensional interconnected network of phase-separated liquid PC nanochannels and exhibits a room-temperature ion conductivity of 10−4 to 10−3 S cm−1 when formed with 15 wt % 0.245 M LiClO4−PC solution. This value approaches that of conventional gelled poly(ethylene oxide)-based electrolytes blended with larger amounts of higher-concentration Li salt solutions. It is also similar to that of a bulk 0.245 M LiClO4−PC solution measured using the same AC impedance methods. Preliminary variable-temperature ion conductivity and NMR DOSY studies showed that liquidlike diffusion is present in the QII nanochannels and that good ion conductivity (∼10−4 S cm−1) and PC mobility are retained down to −35 °C (and lower). This type of stable, liquidlike ion conductivity over a broad temperature range is typically not exhibited by conventional gelled-polymer- or liquid-crystal-based electrolytes, making this new material potentially valuable for enabling Li ion batteries that can operate more efficiently over a wider temperature range.