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Title: Simulation of Energy Storage Characteristics for Engineered Solid-State Nanocomposite Materials
Committee:
Dr. Jeffrey Davis, ECE, Chair, Advisor
Dr. Azad Naeemi, ECE
Dr. Muhannad Bakir, ECE
Dr. John Cressler, ECE
Dr. Hamid Garmestani, MSE
Abstract: This dissertation details the exploration of energy density characteristics and inherent variations in a broad array of nanoparticle (NP) composite materials. It first outlines the development of a custom, high-throughput simulator which approximates the internal electric fields within randomly generated composite materials. It also details a new physics-based model that was developed for the accurate approximation of breakdown strength in composites. In documenting the successful validation of both the simulator and this new physics-based breakdown model, this work presents a unique computational framework for the in-depth study of hypothetical composite materials toward the development of next-generation solid-state energy storage materials. To this end, initial simulation experiments highlight an opportunity for the enhancement of breakdown strength and energy density using low-k (rather than high-k) nanoparticle filler with average simulated energy densities reaching more than double that of the pure host material. Following this, a quasi-electrostatic model is documented which has been implemented to accurately simulate metal-insulator-composites (MIC) and their loss characteristics. While this model was successfully validated against certain material combinations, two publications report anomalous measured data which cannot be explained using classical electrostatic models. This anomalous data motivates an in-depth exploration into negative capacitance (NC) behavior in heterogeneous materials, culminating with the successful simulation of NC effects in NP-MIC, and a close match to the anomalous measured data. This highlights one possible physical explanation for the anomalous data and leads to the conclusion that the engineering of NC behavior in MIC could lead to ultra-high energy density composites. Lastly, a simulation study of core-multishell NP engineering was carried out to quantify the possible energy density enhancements that could be achieved using NP fillers with multiple shells with gradient permittivity between that of the host and filler permittivities. The results of this final study have indicated a possible improvement in energy density of up to 47% compared to pure host material for core-multishell NP composites consisting of SiO2 NP filler immersed in a P(VDF-HFP) host.
