Study of Effective Electrical Conductivity of Additive Free Electrodes Using a Homogenization Method

Conductive additives are used in the cathode of a Li-ion battery to improve electrical conductivity. However, these additives can negatively impact the ionic conductivity and specific capacity of the battery. Therefore, design of additive-free cathodes is gaining attention in the research community. In this paper, we explore the effective electrical conductivity of randomly generated two-phase conductive-free cathode microstructures using a mathematical homogenization method. Over thousand microstructures with various combinations of particle size, volume fraction and conductivity ratios are considered to evaluate effective electrical conductivity values using this method. An explicit formulation is proposed based on the results to provide a simple method for evaluation of the effective conductivity values. The intrinsic properties of each phase of the microstructure are used to obtain the effective electrical conductivity values. With the microstructure geometry information being utilized for the evaluation of the effective properties, the results obtained from this formulation are expected to be more accurate and reliable than those obtained using the popular Bruggeman’s approximation, providing better estimates of discharge characteristics. Finally, the significance of incorporation of micro-structural information to model cathodes is highlighted by studying the discharge characteristics of Li-ion battery system.