Research Progress on Polycarbonate-based Solid-state Polymer Electrolytes

Rechargeable lithium ion batteries become an very important technology in the contemporary society. They are expanding their application in electric vehicles and power grids. However, current lithium ion batteries with liquid electrolyte have been suffering from potential safety crisis mainly due to their highly flammable organic liquid carbonate organic electrolyte and explosion hazards. These potential risks (combustion and explosion) would retard the commercialization of electric vehicles or hybrid electric vehicles. Thus, the safety issue of lithium ion battery merits further study. Solid electrolytes have attracted ever-increasing interest owing to their enhanced safety issue and higher energy density of lithium battery. Solid electrolyte materials mainly include inorganic solid electrolytes (ISEs) and solid polymer electrolytes (SPEs). The ISEs are classified into oxide-based, sulfide-based and etc. However, in spite of the presence of highly ion conductive ISEs, there are still many undergoing issues that limit the practical application at the present stage, like the large interface impedance between electrode and ISEs and the difficulty of processing. More attention has been paid to solid polymer electrolytes due to their superior flexibility and processability, which are also subjected to thermal expansion at elevated temperature. Poly(ethylene oxide) (PEO) solid polymer electrolyte has undergone a sort of renaissance in the past few decades. However, the quintessential frailty of PEO solid polymer electrolyte is low ionic conductivity (in the order of 10(-7) S cm(-1)) at room temperature with a relatively narrow electrochemical window. Hence, it is essential to develop new solid polymer electrolytes with comprehensive performance in terms of high ionic conductivity, wide electrochemical window, superior mechanical strength, excellent thermal stability as well as good interfacial compatibility. In this review, a series of polycarbonate-based solid polymer electrolytes (such as PEC, PPC, PTMC and PVC et al.) are summarized. In addition, we also present a brief review on preparation, electrochemical property, modification, ionic transportation mechanism and future development direction for each of these solid polymer electrolytes.