Ionic Association in CH₃–(CH₂–CF₂)_n–CH₃(PVDF)–Li⁺–(CF₃SO₂)₂N^– for n = 1, 4: A Computational Approach

The ionic conductivity of solid polymer electrolytes is governed by the ionic association caused by the polymer···Li⁺ and the anion···Li⁺ interactions. We performed the density functional calculation to analyze the molecular interactions in the CH₃–(CH₂–CF₂)_n–CH₃–Li⁺–(CF₃SO₂)₂N^– for n = 1,4 systems. The gauche conformation is predicted in the lowest energy conformer of pure polymer except for n = 1. The lithium coordination number with the polymer is changed from 3 to 2 in the presence of anion for n = 2, 4 systems. The consequences of the Li⁺ ion and Li⁺–(CF₃SO₂)₂N^– to the vibrational spectrum are studied to understand the ionic association at the molecular level.