RESEARCH PROGRESS OF GEL POLYMER ELECTROLYTES FOR LITHIUM ION BATTERIES

In recent decades, gel polymer electrolytes (GPEs) have received renewed attention in several areas such as lithium-ion batteries, solar cells and super capacitors due to their promising application. GPEs, swollen in a liquid electrolyte becoming plasticized or a gelled polymer electrolyte, have attracted particular attention because they may provide lighter and safer batteries with longer shelf life,leak proof construction and easy fabrication into desired shape and size. However, GPEs still show poor mechanical strength due to the need for impregnation with the liquid electrolytes. This significant drawback of GPEs hinders their practical application. To overcome these problems, in this review, the up-to-date technologies such as composite gel polymer electrolyte (CGPEs) and porous polymer electrolytes (PPEs) based on the gel concept have been summarized. In the CGPEs, the role of a filler in the membrane is to provide surface groups as physical cross-linking centers for the polymer segments, and thus reduce the polymer reorganization tendency which establishes additional conducting pathways on the filler surface. As a result, the nanosized particles not only lead to better ionic conductivity but also interact with the polymer hosts to enhance the mechanical strength. In PGPEs, due to the existence of the porous structure, the lithium ions can migrate not only in gel electrolyte but also in liquid electrolyte stored in the pores, leading to higher ionic conductivity. In addition, the main characteristics of these gel polymer electrolytes were mentioned. Finally, the future directions are also pointed out.