Impedance Spectroscopy Screening of Various Nanocrystalline Metal Oxides: Effect of Lithiation on Electrical Properties

Abstract

AbstractThe electronic and crystalline properties of solid complex materials dictate performance in electrochemical applications, such as electrodes or solid electrolytes in solid‐state lithium ion power systems. Herein, we perform variable‐temperature two‐electrode impedance spectroscopy on a variety of nanocrystalline metal oxides to investigate their relative total conductivities and the kinetics of vacancy formation. Lithiated and unlithiated first‐row transition metal oxides (manganese, iron, cobalt, and nickel) with various crystal structures, surface areas, and morphologies were investigated. Characterization of these materials by XRD, SEM, and TEM was performed to investigate the physiochemical properties and changes imparted by chemical lithiation, specifically on the textural properties. Activation energies derived from Arrhenius plots were found to vary between 17 and 33 kJ mol−1 for the systems studied. Lithiated nickel oxide was observed to provide the lowest activation energy and highest conductivity of the studied systems. The relatively low electrical conductivity suggests conductive additives must be used to facilitate electron transfer in electrodes for these materials; however, the improved conductivity compared to nonporous “bulk” commercial oxide systems suggests these to be promising active materials for electrochemical applications.