Polystyrene-Al2O3 composite solid polymer electrolyte for lithium secondary battery

Abstract

In a common salt-in-polymer electrolyte, a polymer which has polar groups in the molecular chain is necessary because the polar groups dissolve lithium salt and coordinate cations. Based on the above point of view, polystyrene [PS] that has nonpolar groups is not suitable for the polymer matrix. However, in this PS-based composite polymer-in-salt system, the transport of cations is not by segmental motion but by ion-hopping through a lithium percolation path made of high content lithium salt. Moreover, Al 2 O 3 can dissolve salt, instead of polar groups of polymer matrix, by the Lewis acid-base interactions between the surface group of Al 2 O 3 and salt. Notably, the maximum enhancement of ionic conductivity is found in acidic Al 2 O 3 compared with neutral and basic Al 2 O 3 arising from the increase of free ion fraction by dissociation of salt. It was revealed that PS-Al 2 O 3 composite solid polymer electrolyte containing 70 wt.% salt and 10 wt.% acidic Al 2 O 3 showed the highest ionic conductivity of 9.78 × 10 -5 Scm -1 at room temperature.