The ionic conductivity of the Li + coordinated PDMS with different counter anions is measured by EIS and shows orders of magnitude differences: LiCl < LiBF 4 < LiOTf < LiTFSi (Figure , Figure , Table ). The ionic conductivity of the Li + coordinated PDMS increases with the size of the counter anion. Bulkier counter anions such as OTf - and TFSi -have higher charge delocalization, yielding weaker cation-anion interaction, and therefore the increased ion mobility promotes higher ionic conductivity. In contrast, the smaller anions such as Cl -and BF - 4 have stronger electrostatic attraction with Li + , which results in more significant cation-anion association. This explains the limited salt solubility in PDMS, and moreover, the low ion concentration and low ion mobility together lead to the low ionic conductivity. The MD simulations of LiTFSi also show greater ionic conductivity than LiOTf (σ T F Si -= 0.0054 S/m vs σ OT f -= 0.0041 S/m), though the trend is less prominent than the experimental one. At 30 ℃, the ionic conductivity from MD simulations for LiTFSi is about 3 times higher than the experimental value and it is about 46 times higher than the experimental value for LiOTf. The reason for the large discrepancy in