Mesoscale Modeling and Analysis Pertinent to Electrode Processing
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Fabricating devices consisting of nanoparticles is a manufacturing challenge for novel small scale devices, e.g., ultrathin porous electrodes. Techniques that can have exquisite control over the shape, size and surface properties of nanoparticles have been developed. The efficient utilization of these highly functionalized nanomaterials is dependent on the assembly behavior and resultant microstructures. Evaporation-influenced nanoparticle assembly is a promising scheme to fabricate predefined microstructures. In the present study, a morphologically detailed mesoscale model is developed to investigate microstructure variation produced by evaporation-influenced nanoparticle aggregation. Three dynamic processes, namely solvent evaporation, nanoparticle diffusion and rotation, are incorporated in the model. Fundamentally, system dynamics is dictated by the Hamiltonian, which is the function of interparticle, particle-solvent and solvent-surroundings interactions. Irregularity in particle shape is simulated by using hexagonal particles. Aggregation characteristics like cluster size, film thickness and nanoparticle distribution are found to be a strong function of relative strengths of interaction energies. For evaporation-induced aggregation, an appropriate evaporation rate can facilitate nanoparticle aggregation. However, very high evaporation rates lead to a highly porous structure due to fast bubble growth. Though the usage of nanoparticles for the electrodes has become the center of research, most of the batteries are still prepared using the micro-sized active particles. A Stratification model is used to predict the distribution of micro-sized active particles and KMC method is used to predict the distribution of secondary nanoparticles like conductive additives and binders on the active particles. The stratification model predicts that at lower Peclet number, a uniform film is formed. Also at higher Sedimentation number, particles deposit at a higher rate leading to uniform film formation on the substrate. The KMC model predictions qualitatively explain morphological properties of a nanometer sized film of particulate slurry processed at different drying temperatures. The present simulations demonstrate that the higher drying temperatures and lower chemical potentials produce more compact film with less structural and surface inhomogeneities. This work provides guidelines for the design of efficient microstructure manufacturing strategies. In addition, the developed framework can be easily extended to study realistic slurry behaviors, e.g., polydispersed solution and morphological variations of particles.
Palakurthy, Seshendra (2016). Mesoscale Modeling and Analysis Pertinent to Electrode Processing. Master's thesis, Texas A&M University. Available electronically from