Electrochemical Modeling for Single Particle Design of Electrode Active Material for Lithium Secondary Battery

Abstract

Some of promising electrode active materials for lithium-ion batteries are synthesized as a secondary particle composed of millions of primary particles to compensate for their low electric conductivity and slow diffusion rate (Fig. 1). However, regardless of significant importance of secondary particle design, this study is hardly proceeding due to experimental difficulties. Even, it is almost impossible to see inside phenomena of an active material particle during cycling using experimental methods. Therefore, we newly developed a 3D electrochemical model which can optimize particle capacity and reveal the inside of a single secondary particle in real time during cycling. The main model parameters, the diffusion coefficient and rate constant, were fitted by comparing to experimentally measured rate capability data with a single particle measurement technique [1]. The voltage profiles were drawn from 2 to 20C-rate, which were approximately equivalent to the experimental voltage profiles. The model can estimate overpotential, lithium ion concentration, and state-of-charge of the single particle in real time and these have not been done experimentally with different design parameters and operating conditions. In addition, the model was validated by comparing and analyzing the electrochemical results of LiFePO4 secondary particles with variable design parameters (i.e., solid volume fraction, primary and secondary particle sizes, etc.) [2]