Polaron conduction in Li_x[Ni_1/3Mn_1/3Co_1/3]O_2-δ (x = 1, 0.9 and δ = 0, 0.05) cathodes

Abstract

The dc conductivity measured in a wide range of temperature (93-373 K) for the electrode compounds Li_x[Ni_1/3Mn_1/3Co1/3]O_2-δ (x = 1, 0.9 and δ = 0, 0.05) is reported in this paper. The dc conductivity data have been analyzed in the framework of theoretical models for polaronic conduction. The analysis shows that in the low temperature range (93-163 K) the dc conductivity data are consistent with the variable range hopping model and from the fits of experimental data the density of localized states at Fermi level for different compositions have been estimated. We have explained the temperature dependence of the conductivity employing polaron hopping models, proposed by Schnakenberg and Emin and co-workers, which consider the coupling of polarons with optical and acoustic phonon modes. The value of estimated polaron bandwidth indicates that polaron hopping process is nonadiabatic in nature. The parameters obtained from the fits of this model are reasonable.