Applications of Polymer Materials in Lithium-Ion Batteries: Polymeric Electrolytes and Separators

The applications of polymer materials in lithiumion batteries (LIBs) have become increasingly popular in the past few decades. Some polymer materials can effectively solve many potential dangers of traditional LIBs, such as leakage, short cycle life, and low resistance to high temperature. In this review, several recent advances on electrolytes and separators in LIBs have been discussed in detail. Because of the safety issues of conventional liquid electrolytes, solid polymer electrolytes (SPEs) and gel polymer electrolytes (GPEs) have been developed and used to replace liquid electrolytes in LIBs. Many studies have shown that SPEs and GPEs can efficiently improve lithium-ion batteries' ionic conductivity, safety, and stability. On the other hand, the polymer separator facilitates the flow of ions through the cell by increasing porosity, thus significantly increasing the ionic conductivity. Separators made by PVdF-TrFE material can have even four times higher conductivity than the traditional separator, as well as the ceramic coated polymer separator could have a lower expanding rate, which improves safety. Additionally, the harm to the environment caused by battery pollution also brings trouble to human beings. To protect the environment, some polymer electrolytes with biodegradable and recyclable properties have been developed. However, those polymer electrolytes are not yet available for industrial production because of the complexity and high cost of preparations.