Preparation and Characterization of Hybrid Oxyethylene/Siloxane Electrolyte Systems

One of the most significant consequences of technological evolution in the workplace has been a dramatic increase in the need for portable energy storage. This evolution has occurred, not only with respect to the number of devices, but also in their average energy storage capacity. An obvious commercial consequence has been an increased pressure to develop improved active materials for power sources and more efficient methods for battery production. In recent decades the growth of the commercial market for high performance batteries has been based on the development of both solid‐state and gel electrolytes. The incorporation of these electrolytes as components of various devices (advanced batteries, smart windows, displays and super‐capacitors) offers significant advantages relative to traditional electrolytes, including enhanced reliability and improved safety. The xerogel matrices prepared in this study are represented as U(900) and U(600) and contain 15.5 or 8.5 oxyethylene structural units (CH₂CH₂O) respectively. The oxyethylene chains are bonded at each end to a siliceous intersection through urea bridging links. These sol‐gel derived oxyethylene /siloxane xerogels (designated as di‐ureasils) were doped with controlled amounts of LiAsF₆ or LiSbF₆ to prepare a range of electrolyte compositions. The compositions prepared, with 200>n≥2.5 (where the salt content is expressed as n, the molar ratio of oxyethylene moieties to Li⁺ ions), were characterized by electrochemical and thermal techniques. Preliminary tests performed with a prototype electrochromic device (ECD) incorporating the most promising electrolyte composition, d‐U(900)₈LiAsF₆ as electrolyte and WO₃ as cathodic electrochromic layer, are extremely encouraging.