Microstructure Evolution in Lithium-Ion Battery Electrode Processing

The electrode microstructure and composition play an important role in determining the performance of the lithium ion battery (LIB). To this end, the processing of the multi-phase slurry consisting of active nanoparticles, conductive additives, binder and solvent determines the electrochemical properties and performance of the electrode. Mixing components in the slurry homogenously is one essential requirement to process the high quality electrode. Additionally, it is necessary to make these components cooperate very well with each other.^1-4

Fundamentally, slurry properties and drying methods mainly determine the microstructure and the performance of the cathode composite. Viscosity of the slurry is an important property, which is determined by the concentration and the solid loading of each component, the interaction force among nanoparticles in the slurry, and the properties of active material nanoparticles that include the size of the nanoparticle, size distribution and the surface area.⁵ One common mechanism of the drying process is solvent evaporation from the surface of the substrate. The evaporation induced assembly is a popular scheme to make nanoparticles form desirable microstructures, and this assembly is controlled by interactions among nanoparticles and solvents, evaporation rates, mobility of nanoparticles and the morphology of nanoparticles.

In our present work, a morphology-detailed mesoscale model has been developed to gain fundamental understating of the influence of active particle morphology, size, volume fraction, solvent evaporation rated, and multi-phase (active particle, conductive additive, binder and solvent) interaction. Our results demonstrate that smaller isometric active particles tend to form favorable aggregation with conductive additive particles. Two regimes, namely spontaneous aggregation and evaporation induced