Effect of Electronic Conductivity on the Polarization Behavior of Li[Li1/3Ti5/3]O4 Electrodes

Abstract

Along with structural factors such as thickness and porosity, the conductive additive in lithium insertion electrodes in lithium-ion batteries influences the rate capability. The addition of a conductive additive improves the electronic conductivity of the electrodes, necessitating the optimization of such additives. However, the relationship of conductive additives to the electronic conductivity and rate capability of an electrode cannot be explained using classical electrochemical theory. The effect of the electronic conductivity of electrodes on polarization was investigated using Li[Li1/3Ti5/3]O4−pellet electrodes, whose electronic conductivity can be modified using a graphite conductive additive during an oxidation/reduction reaction. Consequently, the polarization behavior of the Li[Li1/3Ti5/3]O4−pellet electrodes without the conductive additive is asymmetric during the reduction and oxidation reactions, while it is symmetrical in the electrodes with the conductive additive. Furthermore, the polarization voltage is significantly lower in the electrodes with the conductive additive. Herein, we propose a rational explanation for the observed relationship between the electronic conductivity and polarization of electrodes using the formation and disappearance of electron conduction paths. This explanation would help us understand the enhancement of the rate capabilities of electrodes with poor electronic conductivity using conductive additives by the construction of the electron conduction paths.