Numerical Simulation with Multi-Network Model and Discrete Element Method for Dynamic Structure Change and Cell Performance of All-Solid-State Batteries

摘要

Recently, all-solid-state-lithium-ion batteries have attracted attention as next-generation batteries serving as driving sources for electric vehicles (EVs) and hybrid electric vehicles (HEVs). However, it is required to have more power density and more energy density. In order to develop the performance of batteries, High-capacity negative active material (AM) such as Si have been developed, but their use is not easy due to severe expansion during charging and discharging. Although materials with reduced expansion and contraction have been developed, it is unclear how much expansion of the AM is allowed in the first place and how much it affects the porous electrode structure. Also, since the performance of batteries depend not only on the material characteristics but also on its electrode structure, it is important to design an optimum electrode structure. Therefore, chasing the state in electrode layer using the numerical computation is a critical measure for the comprehension of phenomenon in the cell. However, in the relatively micro-scale system such as the electrode layer, a slight difference in structure affects the battery performance. However, usual simulations demand the reactive interface area and the tortuosity factor which critically affect the cell performance by reasonableness or approximation, as it might overlook the phenomenon from minute structure of electrode layer. Therefore, our laboratory has devised a multi-network model as a method that directly reflects the transport characteristics in the particle-packed structure. In this study, we apply it to an all-solid-state battery and examine the effect of various structural factors on the expansion and contraction of the AM.