Impact of PVDF Oligomers on LiFSI-Doped Protic Organic Ionic Plastic Crystal (POIPC): Insights from Molecular Dynamics Simulations and Experiments

We report here, for the first time, the molecular dynamics simulation to unravel the influence of polymer oligomers, PVDF oligomers, on the LiFSI-doped [DBUH]-[FSI] protic organic ionic plastic crystal (POIPC). Analysis reveals that the addition of PVDF to the LiFSI-doped POIPC results in further amorphization of the samples and subsequent reduction or disappearance of the first-order melting transition. The simulated solid–solid phase transition temperature and the melting temperature are in considerable agreement with the DSC analysis. The protic pairs N2–H1–O and N2–H1–N3 form the strongest hydrogen bonds (HBs) in the system, with the incorporation of PVDF into the samples resulting in the weakening of these HBs. Dynamical analysis further unveils that the rotational disorder in these systems is accompanied by the simultaneous enhancement in the translational dynamics. Most importantly, PVDF doping preferentially accelerates lithium-ion diffusion compared to other ionic species─a critical finding for solid-state electrolyte design.