Particle Size Polydispersity in Li-Ion Batteries

Abstract

Starting from three-dimensional X-ray tomography data of a commercial LiMn2O4 battery electrode, the effect of microstructure on the electrochemical and chemo-mechanical response of lithium-ion batteries is analyzed. Simulations show that particle size polydispersity impact the local chemical and electrical behavior of a porous electrode, while particle-particle mechanical interactions favor intercalation induced stress accumulation, resulting in a mechanically unreliable electrode microstructure. Simulations based on computer-generated electrode microstructures demonstrate that broad particle size distributions deliver up to two times higher energy density than monodisperse-sized particles based electrodes for low C-rates. However, monodisperse particle size distribution electrodes deliver the highest energy and power density for high discharge rates due to a higher surface area of reactive material per unit volume. Calculations show that the surface roughness in experimentally determined electrodes is 2.5 times higher than the one delivered by perfectly smooth spherical particles in computer generated electrodes, and provide high instantaneous power performance, but accelerate side reactions that impact negatively on power performance. The combined experimental and modeling approach demonstrates that porous electrodes with spatially uniform microstructural features improve electrochemical performance and mechanical reliability, especially for high power density applications.