Mechanistic Elucidation of Si Particle Morphology on Electrode Performance

Abstract

High specific capacity silicon anodes are limited by immense volumetric expansion upon lithiation making them prone to deleterious capacity fade through particle cracking and disintegration. Nanosized silicon active particles with spherical and rod morphology demonstrate resistance to lithiation induced fracture owing to their smaller size. However, lithiation in silicon nanospheres and nanowires exhibit varying characteristics as a function of the morphology. In this work, we contrast the lithiation impact on diffusive transport and reaction kinetics for silicon nanospheres and nanorods cognizant of the volume evolution using a particle formalism. For the same equivalent volume, nanorods surpass nanospheres in rate performance beyond a threshold initial length to initial radius aspect ratio. Nanorods show faster radial growth as compared to nanospheres for the same initial radius, resulting in exacerbated diffusion limitations below the threshold aspect ratio. The mechanistic insight into the performance dependence on morphology is elucidated. Diffusivity and exchange current density values for the silicon anode are calculated as well through synergy between experimental dataset and simulation results.