2021 年 89 巻 2 号 p. 157-161
To establish the kinetics of the lithium insertion materials used as the electrodes in lithium-ion batteries, it is important to clarify the diffusion phenomena of lithium ions in the solid phase. Since there are two variations of the rate-determining step of a lithium insertion electrode (Li-ion diffusion in solid particles and that in the electrolyte solution), these have to be differentiated in any investigation of the diffusion phenomena of Li ions in a solid. In this study, we calculated the rate capability of diluted electrodes using a charge–discharge simulation program and proved that the transport of Li ions in the solid phase is the rate-determining step for a diluted electrode with an extremely low active material content. In addition, the solid-state Li-ion diffusion coefficient can be calculated by analyzing the results of the rate capability tests. These results reveal that the diluted electrode method is very useful for elucidating the solid-state Li ion diffusion phenomena of lithium insertion materials. As such, the rate capability tests provide a new means of analyzing the solid-state diffusion coefficient.