Poly(vinyl alcohol)–LiBOB complexes for lithium–air cells

Abstract

Poly(vinyl alcohol) or PVA complexes with lithium bis(oxalato)borate or LiBOB have been prepared by solution casting. X-ray diffraction reveals that the amorphousness of the polymer increased until 40wt.% LiBOB salt concentration. The increase in amorphousness is accompanied by a decrease in the glass transition temperature, Tg. The diffusion coefficient of lithium ion obtained from cyclic voltammetry (CV) is 1.98×10−8cm2s−1. From infrared and impedance spectroscopic studies, it is inferred that conductivity is governed by charge carrier density, ionic mobility and diffusion coefficient for PVA incorporated with 10–40wt.% LiBOB. However, for the sample with equal weight ratio of PVA and LiBOB, ionic mobility and diffusivity have a greater influence over charge carrier density in determining conductivity at room temperature (RT). PVA can solvate a large amount of salt and for the highest conducting composition of 60wt.% PVA–40wt.% LiBOB, conductivity extends from 10−4Scm−1 at RT (25°C) to 10−3Scm−1 at 100°C. This sample was tested as an electrolyte in a Li–air cell.