Understanding the Influence of Functional Groups on the PEO Composite Electrolytes through a Theoretical, Spectroscopic, and Conduction Behavior Study of Model Systems

Abstract

Introducing functional groups via blending or copolymerization is a promising approach to improve Li + transference number and ionic conductivity of poly(ethylene oxide) (PEO) electrolytes in solid-state lithium battery. Nevertheless, the laws governing the impact of functional groups on ion coordination and transport at the microscopic level remain unclear, mainly due to intricate competitive interactions among multiple components and the absence of controllable variables in experimental models. In this work, potential energy surface search methods based on density functional theory, combined with molecular dynamics simulation, spectroscopy, and experiments of standardized models, were employed to examine the binding and migration property of lithium ions and anions with four functional groups showing distinctly different electronic effect: −NH 2 , −OH, −CN, and −CH 3 . The results show that the binding trends for lithium ions were −NH 2 > −OH > −CN > −CH 3 , and for anions, they were −NH 2 > −CN > −OH > −CH 3 . These varying binding preferences led to differences in conductivity and transference numbers for the grafted silica particle-PEO composite electrolytes. It could be a guideline for designing solid polymer electrolyte with improved ionic conduction performance by modifying filler surface or optimizing polymer chain structure with different functional groups.

Computational approach inspired advancements of solid-state electrolytes for lithium secondary batteries: from first-principles to machine learning

“…MD simulations play a multifaceted role in the study of SSEs by accurately capturing the complex dynamics and interactions between ions and the SSE matrix. 41 First, MD simulations enable the exploration of the structural stability and phase transitions of SSE materials. By simulating the system at different temperatures and pressures, researchers can identify phase boundaries and observe the structural changes that occur within SSEs.…”

Toward a molecular understanding of the conductivity of lithium-ion conducting polyanion polymer electrolytes by molecular dynamics simulation

“…For double ion conductor polymer electrolytes, the diffusion behavior of lithium ions in the PEO matrix has been deeply studied, which accelerates the research and development of polymer electrolytes. 39–42 Notably, PEO is a commonly used polymer solvent 19,22,31 for SLIC-SPEs due to its adequate ether-oxygen distance that allows it to chelate with Li-ions as well as its flexible chain segments, which allow for flexible Li-ion movement with the polymer chains. 43…”