Continuum-Scale Modeling of Rechargeable Batteries
Kazemiabnavi, Saeed
2020
Abstract
During the operation of a rechargeable battery, the electrochemical reactions occur at the interface between the electrolyte and the active material in the electrode. The electrochemical performance of such batteries is influenced by a complex interplay between the kinetics of the electrochemical reactions and the transport of reactant and product species in the electrode and electrolyte. In this dissertation, the effect of various electrode and electrolyte properties on the electrochemical performance of the battery is investigated via computational modeling at a variety of length scales and dimensionalities. Two applications are studied in this dissertation: the kinetics and thermodynamics of nucleation during electrodeposition on metallic anodes, and the transport kinetics in the electrolyte and intercalating electrodes in lithium-ion batteries. A continuum-scale model based on the classical theory of nucleation is formulated to study the nucleation behavior of several metals during electrodeposition on metal anodes. The model utilizes the formation energies of critical nuclei obtained from density functional theory calculations to estimate the time-dependent and steady-state nucleation rate and density on various metal anodes. Nucleation rates are predicted to be several orders of magnitude larger on alkali metal surfaces than on the other metals. This multiscale model highlights the sensitivity of the nucleation behavior on the structure and composition of the electrode surface. In order to study the kinetics of lithium ion transport in intercalating electrode particles, a continuum-scale model is developed that provides detailed insight into the kinetics and voltage behavior of the (de)intercalation processes in core-shell heterostructure cathode particles. The simulations indicated that an open-circuit potential difference between the surface and bulk phases in a core-shell cathode particle leads to a charge/discharge asymmetry in the galvanostatic voltage profiles, causing a decrease in the accessible capacity of the particle. Moreover, further simulations showed that this reduction in the accessible capacity is smaller when the surface-phase diffusivity is higher than the bulk-phase diffusivity. These findings provide valuable guidance in developing material selection criteria that ensures optimal electrochemical performance in core-shell heterostructure hybrid cathode particles. In composite battery electrode architectures, local limitations in ionic and electronic transport can result in nonuniform energy storage reactions. A continuum-scale model based on the porous electrode theory was utilized to investigate the effect of various electrode and electrolyte properties on the reaction heterogeneity across the electrode thickness. Our simulations showed that accelerated reactions at the electrode faces in contact with either the separator or the current collector demonstrate that both ionic and electronic transport limit the reaction progress. This rate heterogeneity may accelerate rate-dependent degradation pathways in regions of the composite electrode experiencing faster-than-average reaction. Designing Li-ion batteries with electrodes that are capable of fast ion transport is essential in improving their power density under fast-charging conditions. In order to investigate the effect of introducing vertical channels through the thickness of the electrode on the Li ion transport during fast charging, a three-dimensional continuum-scale model based on the porous electrode theory is developed. These simulations allow us to investigate the geometric parameters that affect the electrochemical performance of highly-ordered hierarchical (HOH) anodes under galvanostatic extreme fast charging conditions. Our analysis showed that the HOH anode architecture with optimized geometric parameters can significantly improve the galvanostatic charge capacity of the electrode at high rates by minimizing the transport limitations that occur during extreme fast charging conditions.Subjects
Rechargeable Battery Electrode Computational Modeling
Types
Thesis
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