Charge Delocalization on BO4- Centers to Improve Conductivity on Single Lithium Ion Conducting Polymer Electrolytes: A Computational/Experimental Approach

Single lithium ion conducting polymer electrolytes (SLIPCE) are one of the best options for safer Li ion batteries, only if new strategies can be envisaged to improve the ionic conduction properties. In this work we examine the effect of two strategies to improve the ionic conductivity of SLICPE based on sp3 boron atoms linkers by PEG chains, namely partial cross-linking and modification of the electro-attractor properties of the substituents. The molecular structure analysis, determined by Density Functional Theory, shows an important variation on the electron density of the BO4- group allowing lower Li+-polymer interaction energy and also lower activation energy for Li+ hoping; these results confirm the changes in the chemical environment of B and Li established by NMR. The increase of the electro-attractor capacity of the substituent groups over the BO4- groups decreases their electronic density, increases the length of the BO4- bond distance and allows higher mobility of Li+ in the partially cross-lin...