Accelerating the reaction rates of nucleation growth and solid-state diffusion in electrochemical lithium insertion into MgMn₂O₄ by controlling the particle size

Lithium insertion reactions occur via two main processes: nucleation growth in the initial stage and three-dimensional diffusion in the subsequent stage. This study aims to understand the effect of particle size on these processes, which are crucial for optimizing battery performance. The lithium insertion kinetics of MgMn₂O₄ particles of varying sizes is analyzed by chronoamperometry. The results show that smaller particles exhibit faster lithium insertion kinetics than larger particles. The experimental data is fitted to a solid-state reaction model that accurately describes the observed current profiles. The fitting analysis reveals that the rate constants of nucleation growth (k_A) and three-dimensional diffusion (k_D) are influenced by the particle size. Specifically, k_A and k_D increase exponentially as the particle size decreases. This relationship indicates that smaller particles have larger surface areas and shorter diffusion distances, which facilitate faster lithium insertion. In addition, the overvoltage dependence of k_A remains constant across different particle sizes, indicating a consistent reaction mechanism. Overall, these findings emphasize the importance of particle size in optimizing lithium insertion kinetics in battery materials. A smaller particle size can significantly improve the reaction rates, but trade-offs, such as reduced electrode density and increased side reactions due to a larger surface area, must be considered. Thus, understanding the particle size dependence of lithium insertion kinetics is essential for designing high-performance lithium-ion batteries.