Interatomic Interactions and Ion‐Transport in a Polyoligomeric Silsesquioxane‐Based Multi‐Ionic Salt Electrolyte for Lithium‐Ion Batteries

Abstract Polyoligomeric silsesquioxane (POSS) tailored with trifluoromethanesulfonylimide‐lithium and solvated in tetraglyme (G4) is a potential electrolyte for Li‐ion batteries. Using classical MD simulations, at different G4/POSS(−LiNSO 2 CF 3 ) 8 molar ratios, the interactions of Li + ions with the oxygen atoms of G4 and, oxygen/nitrogen sites of the pendant tails, the behaviour of POSS(− − NSO 2 CF 3 ) 8 , and the mobility of species are investigated. The RDFs showed that there exist competing interactions of the O(G4), O(POSS), and N(POSS) sites with Li + ions. The lifetime analysis indicated that Li + ‐ ‐ ‐O(POSS) and Li + ‐ ‐ ‐N(POSS) interactions are longer‐lived compared to Li + ‐ ‐ ‐O(G4). The morphological changes of the POSS tails upon interaction with Li + ions were analysed using rotational lifetimes, coiling, and end‐to‐end distances. The ion‐speciation analysis indicated the presence of solvent‐separated ion pairs (SSIPs), contact ion pairs (CIPs), and higher‐order ion clusters, with SSIPs being the more dominant species at 32/1. The self‐diffusion coefficients for the 32/1 system, which showed the least cation‐anion interaction, followed the trend:D G 4 > D L i + > D F P O S S> D P O S S${{D}_{G4}\char62 {D}_{Li+}\char62 {D}_{F\left(POSS\right)}\char62 {D}_{POSS}}$ . The computed cationic transference number (t + ) using theD F P O S S${{D}_{F\left(POSS\right)}}$ is consistent with NMR experimental data. The t + (and the trends with temperature) computed using theD P O S S${{D}_{POSS}}$ and ionic conductivities are in good agreement.