Numerical analysis of solid-state battery cathode hetero-agglomerate formation in turbulent pipe flows

Hetero-agglomeration of micron- and submicron-sized particles enables the formation of all-solid-state battery cathode materials with enhanced safety and energy density. This study investigates a turbulent pipe flow process for mixing lithium iron phosphate (LiFePO 4, LFP), lithium indium chloride (Li 3 InCl 6 , LIC), and carbon black (CB) to form three-component hetero-agglomerates. The analysis aims to identify suitable pipe dimensions and evaluate how different mixing configurations affect agglomerate size, composition, and structure. The investigation employs a dedicated simulation framework utilizing a mesh-free representation of turbulent flow fields derived from direct numerical simulation datasets. Lagrangian particle tracking incorporates an improved discrete random walk model, while stochastic agglomerate structure simulations account for various turbulent collision mechanisms, hydrodynamic interactions, and breakup events. Prior to simulations, virtual CB aggregates were stereologically reconstructed from scanning electron microscopy images, the particle size distributions were determined using laser light diffraction, and the surface energies of all materials were determined from contact angle measurements using the Owens-Wendt-Rabel-Kaelble method. Simulations examined parallel mixing and sequential premixing configurations (LFP-CB, LIC-CB, and LFP-LIC) across various pipe diameters. For parallel mixing under experimental process conditions, an 18 mm pipe diameter proved optimal, achieving maximum particle capture in agglomerates at a downstream distance of 2.73 m. Premixing diameters were selected based on mixing length and deposition. The mixing configuration significantly influences the agglomerate composition, material-specific mixing quality measures, and the contact-pair distribution. The findings provide concrete recommendations for experimental process design regarding pipe dimensions and mixing strategies, while the influence on electrochemical properties requires further investigation.