Connecting structure and rheology of silicon/carbon supraparticle-based lithium-ion battery anode slurries

Abstract

Due to the globally increasing demand for lithium-ion-batteries of high energy density, novel silicon-based materials of hierarchical structure are investigated as a potential replacement for conventional anode materials such as graphite. Since industrial process technologies cannot keep up with the development of new formulations, such approaches should be suited as ”drop-in” methods to the existing manufacturing processes. In this study, spray-dried silicon-based supraparticles of hierarchical structure are investigated regarding their suitability for industrial slurry processing under harsh mechanical conditions. The chosen strategy is to connect the structural integrity of the supraparticles with their time-dependent rheological behavior in anode slurries to provide methods for a mechanical characterization tailored to supraparticles. Apart from questions of battery processing, this study also provides general guidance on the rheology of supraparticle dispersions, which has been little studied so far. Structural kinetic models, experimentally determined thixotropic relaxation times, and a differential effective medium approach tailored for supraparticles are used herein. With this developed rheological toolset, a strong indicator of the mixing fraction of supraparticles and their primary particles inside full anode slurries is presented and the deagglomeration dynamics of the supraparticle structure in shear flow are resolved.