Computational insight into the structural properties and redox chemistry of poly (ethylene carbonate) as electrolytes for Lithium batteries

Abstract

New electrolytes with high electrochemical stability and ionic conductivity are important in the development of lithium ion batteries. Polyethylene carbonate (PEC) is a very promising candidate. Herein, the DFT modeling approach is performed to investigate the coordination structure of Li+ ion in PEC, and the redox potentials of a set of polymer models to assess the effect of polymer monomer unit composition. [Li(PEC)] [Anion] (BF4−, PF6−, ClO4−, TFSI−) are also considered. It is highlighted that the coordination shell of Li+ ion is most likely fully occupied by four carbonyl oxygen atoms of PEC. Next, the carbonate group can lead to greater oxidation stability than ester, ketone and ether group, the length and configuration of alkyl chain affect the redox potential only slightly. Furthermore, the addition of electron-withdrawing groups (-F and -CF3) can increase the oxidation stability of PEC, while the -CN group substitution shows the opposite effect, due to the ring formation or bond breaking of intramolecular structure. All these findings provide important information for understanding the ion-polymer interactions and synthesizing the promising new electrolyte molecules for high-voltage batteries.