Quantum mechanical insight into the Li‐ion conduction mechanism for solid polymer electrolytes

Ion transport in polymeric electrolytes (PEs) has been studied for approximately a half century, yet the ion conduction mechanism in the PEs is not fully understood. Herein, we report a new approach to understand the ion migration process in poly (ethylene oxide)/Lithium bis(trifluoromethane sulphonyl) imide (PEO/LiTFSI) and poly (ethylene oxide)/Lithium bis(oxalate) borate (PEO/LiBOB) electrolytes based on quantum mechanics. The results show that the coefficient of determination (R-2) obtained from the new model exceeds 0.99 for all the PEs, which is far higher than these obtained from the well-known Arrhenius and Vogel-Tammann-Fulcher (VTF) equations. The wavelength (lambda(Li+)) of Li-ion migrations or the distance between the occupied site and the neighboring partially-occupied site is the most crucial factor to affect the ionic conductivity of PEs. The higher the lambda(Li+), the better the ionic conductivity. The maximum lambda(Li+) value of the PEs approximates angstrom order of magnitude. The developed ion conduction model opens an avenue to design PEs with a higher ionic conductivity.