Exploring the Relationship between Ion Diffusion and Molecular Structure of Gel Polymer Electrolytes Using NMR Spectroscopy

Lithium rechargeable batteries are widely used as energy sources for portable electronic devices, automobile, and wearable electronics. However, concerns regarding fire hazards have prompted efforts to transition from liquid to solid electrolytes. Gel polymer electrolytes (GPEs) have emerged as promising alternatives for enhancing the safety of lithium batteries. The ion conduction mechanism in GPEs can be conceptualized in two distinct modes: a liquid-like mechanism and a solid-like mechanism. We focus on the investigation of the liquid-like mechanism, which relies on polymer segmental motion. Various factors can influence ionic conduction of gel polymer electrolytes such as the structure of the sidechain, interaction between sidechain and ionic species etc. We utilize PFG NMR and nuclear relaxation time measurements to explore the correlation between the ionic motion and the structure of polymers and ionic liquids. Chain length of polymer sidechain will be varied and structurally isomeric ionic liquids will be utilized. We will demonstrate that NMR spectroscopy is a good indicator to examine the dynamics of the gel polymer electrolyte. Understanding of the structure-dynamics relation from our study will serve as a design principle to develop new gel polymer electrolyte with desired properties.