Evaluation of Electrode Structure and Simulation of Transport Phenomena in Lithium-Ion Battery

Recently, the importance of various secondary batteries is increasing remarkably, because it is expected as the energy storage devices for renewable energy, such as solar and wind, as the basic technology for energy security and as the power storage for automotive. Especially, in order to increase the high-rate performance, Innovative design of electrode structure on the basis of kinetics and transport phenomena of ion and electron is needed. In our previous study, we focused on the binder and examined the effect of binder distribution and porous structure on the discharge performance by numerical analysis. In this study, actual porous electrode structure was obtained by FIB-SEM and the effective electrical and ionic conductivities were estimated, and these were compared with experimental results. Moreover, the effect of structure on the discharge performance and reaction rate distribution by 3D direct simulation. As a result, the correlation model of the relationship between porosity and relative conductivity of Li⁺ and electron could be obtained. And the remarkable difference between heterogeneous structure and uniform particle packed model could be confirmed. The validity of this simulation method could be confirmed by the comparison of tortuosity and relative conductivity between estimation and experimental results. From the electrochemical reaction simulation, in the case of reducing binder to 1/3 of actual condition, overall current could increase twice. So it was found that the optimization of structure of sub-material, which consists of binder and conductive material, is very important to increase high-rate discharge performance. In addition, we examined the effect of binder adhesion model and migration in the direction of through-plane.