Structure and transport properties of poly(ethylene oxide) based cross-linked polymer electrolytes -- A Molecular Dynamics Simulations study

TL;DR

This study uses molecular dynamics simulations to analyze the structure and ion transport in cross-linked PEO-based polymer electrolytes with multi-salt systems, revealing insights into their microscopic behavior and dynamics.

Contribution

It provides a detailed molecular-level analysis of cross-linked PEO electrolytes with multi-salt systems, extending understanding beyond previous studies on linear polymers.

Findings

Local dynamics are only slightly restricted compared to linear PEO.

Multi-salt systems outperform single salt systems in ion transport.

Ion transfer and backbone motion are influenced by the type of salt used.

Abstract

We present an extensive molecular dynamics (MD) simulation study of poly(ethylene oxide) (PEO) based densely cross-linked polymers, focussing on structural properties as well as the systems dynamics in the presence of lithium salt. Motivated by experimental findings for networks with short PEO strands we employ a combination of LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide) and LiDFOB (Lithium difluoro(oxalato)borate). Recently, it has been shown that such multi-salt systems outperform classical single salt systems (Shaji et al., Energy Storage Materials, 2022, 44, 263). To analyse the microscopic scenario we employ an analytical model, originally developed for non-cross-linked polymer electrolytes or blends (Maitra et al., Phys. Rev. Lett., 2007, 98, 227802 and Diddens et al., J. Electrochem. Soc., 2017, 164, E3225-E3231). Excluding very short PEO strands, the local dynamics is only slightly restricted compared to linear PEO and is not significantly dependent on the network structure. The transfer of lithium ions between PEO chains and the motion along the polymer backbone may be controlled through the employed salt.