Effects of overvoltage and temperature on the lithium insertion kinetics of MgMn2O4

Abstract

The power capability of lithium-ion batteries strongly depends on the reaction kinetics of the lithium insertion material used in the electrodes. Previously, chronoamperometry revealed that the lithium insertion reaction of MgMn2O4 differs between static and dynamic processes and that the dynamic process consists of a nucleation–growth process followed by diffusion. Herein, we present the overvoltage and temperature dependence of the reaction rate of MgMn2O4 through chronoamperometry results under different applied voltages and temperatures. The rate constant of each process is determined by fitting the measured current profile to a solid-state reaction model. The rate constant of the nucleation-growth process exhibits an Arrhenius relationship with temperature and a Tafel-like relationship with overvoltage, whereas that of diffusion exhibits an Arrhenius relationship with temperature and does not depend on overvoltage. These dependencies are different because nucleation–growth is a reaction process on the particle surface, whereas diffusion is a reaction process occurring inside the particle. Accordingly, the rate-determining step of lithium insertion under various operating conditions is discussed.