Lithium Metal Polymer Cells assembled with Polyurethane-based Polymer Electrolytes

Abstract

Lithium-ion batteries have been widely used to a variety of applications such as smartphone, electric vehicle, and energy storage system due to their high energy density and long lifespan. However, more and more applications such as electric vehicles require higher energy density than that of lithium-ion batteries these days. In order to satisfy their requirements, employing the lithium metal batteries became inevitable despite of the safety concerns of using lithium metal. Solid-state electrolytes have been suggested as a solution for enhanced safety of the batteries by their non-volatility and suppressing the formation of lithium dendrite. In this study, polyurethane-based solid polymer electrolytes (PU SPEs) were prepared as a form of thin flexible film, and their electrochemical characteristics were investigated. To improve the ionic conductivity and thermal stability, non-volatile ionic liquid, 1-Ethyl-3-methylimidazolium bis(tri-fluoromethanesulfonyl)imide (EMImTFSI) was added as a plasticizer to the electrolytes. The films were used to fabricate the solid-state Li/LiNi0.6Co0.2Mn¬0.2O2 cells, and the cells exhibited an initial discharge capacity of 139.3 mAh g-1 and a good capacity retention of 80.6% at 55 oC.