Impact of Supraparticle Sizes and Morphology on Interparticle Spacing, Slurry Rheology, Coating Density, and Electrochemical Performance in Si/C Anodes for Li-Ion Batteries

This study investigates the influence of supraparticle sizes and associated morphologies (shape, surface roughness, internal structure, and surface area) on the performance of silicon/carbon (Si/C) composite anodes for lithium-ion batteries. Supraparticles, hierarchically structured agglomerates produced via spray drying, enhance the processability of Si/C nanoparticles by improving handling and packing efficiency and minimizing solid electrolyte interphase (SEI) formation. We systematically explore how supraparticle size distributions and associated morphologies affect interparticle spacing, slurry rheology, coating density, and electrochemical performance. Medium-sized supraparticles (5.0–6.0 μm) with spherical shapes exhibit optimal properties, achieving the highest coating density (0.90 g cm –3 ) and providing precise control over layer thickness and porosity, resulting in uniform coatings. These supraparticles also deliver good electrochemical performance, with a first-formation Coulombic efficiency of 87.5% and stable cycling, retaining 86.2% of the capacity (relative to the third cycle) after 100 cycles. Furthermore, they demonstrate an ideal balance for high-power (up to 3 C) and high-energy applications. In comparison, smaller supraparticles (irregular shapes) exhibit increased interparticle spacing, resulting in less dense layers and higher SEI formation, while larger supraparticles excel at ultrahigh rates (5 and 10 C) but face limitations in long-term cycling due to internal voids. These findings highlight the critical role of controlling the supraparticle size and morphology to optimize electrode processing and performance, enabling scalable, high-performance energy storage solutions.