All-solid-state lithium-based polymer cells for high-temperature applications

A lithium salt doped siloxane/methacrylate copolymer membrane, prepared by a rapid UV curing process, has been characterised and tested as a fully solid electrolyte in rechargeable lithium test cells using low cost materials as electrodes. In addition, results of a laboratory-scale Li-ion polymer cell, assembled by contacting a LiFePO₄ cathode with a graphite anode and using the solid polymer as electrolyte, are presented. The polymer electrolyte production process is simple and versatile and the highly cross-linked membrane demonstrates mechanical integrity, low T _g and large thermal stability. It is an extra soft, non-crystalline, transparent solid and shows sufficient ionic conductivity (>10⁻⁴ S cm⁻¹ at 60 °C) along with a wide electrochemical stability window and improved interfacial stability with respect to lithium. The performances in Li-based cells have been determined by cycling tests carried out at 80 °C. Good rate capability, along with high charge/discharge efficiency even at 1C-rate, and a satisfactory cyclability have been obtained. These results outline the practical relevance of the use of this solid electrolyte membrane (which serves as the separator simultaneously) in Li-based cells conceived for high-temperature applications.