Modeling analysis of ionic solvation structure in concentrated poly (ethylene carbonate) electrolytes

Although the performance of all-solid-state batteries has improved greatly in the last few decades, the lack of understanding of their working mechanism is still a hindrance in many studies and in improving the properties and performance of solid polymer electrolytes (SPE). To learn about the solvation structure in concentrated poly (ethylene carbonate) (PEC) electrolytes and aim to improve their ionic conduction, molecular dynamics simulations were performed in electrolyte models consisting of PEC and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI). Based on the radial distribution function, a competitive effect induced by interactions between Li cations and TFSI anions was determined to take over the capital coordination from C=O groups in the PEC chains and increase segmental motion. Changes in the total coordination number in electrolytes revealed that the freeing of Li cations from the coordinating bonds would lead to an increase in the transport number with increasing salt concentration. Finally, according to the theoretical calculation of free volume and ionic conductivity, the TFSI anions are expected to act as a plasticizer in concentrated electrolytes, which could transform into an aggregate with Li cations and promote the mobility of those cations as well as their conductivity.

Automated summary

Despite the significant improvement in the performance of all-solid-state batteries in recent decades, the lack of understanding of their working mechanism remains a hindrance in many studies and in enhancing the properties and performance of solid polymer electrolytes (SPE). Molecular dynamics simulations were conducted to investigate the solvation structure in concentrated poly (ethylene carbonate) (PEC) electrolytes and to enhance their ionic conduction. The competitive effect induced by the interactions between Li cations and TFSI anions was found to replace the main coordination of C=O groups in PEC chains and enhance segmental motion. The calculations of total coordination number in the electrolytes indicated that the release of Li cations from the coordinating bonds would increase the transport number with the increase in salt concentration.