Date on Master's Thesis/Doctoral Dissertation

12-2025

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Mechanical Engineering

Degree Program

Mechanical Engineering, PhD

Committee Chair

Park, Sam

Committee Member

Bhatia, Bikram

Committee Member

Sumanasekera, Gamini

Committee Member

Wang, Hui

Author's Keywords

Lithium-ion battery; fast-charging; immersion cooling; multi-objective optimization; battery modelling

Abstract

Presently, widespread adoption of electric vehicles (EVs) is hindered by challenges associated with XFC, including heat generation, lithium plating, and accelerated battery degradation. This dissertation addresses these barriers through two coordinated themes—lithium plating and thermal management—spanning four manuscripts that integrate operando diagnostics, physics-based simulation, and module-level design optimization. The first theme seeks a fundamental investigation into the dynamic interplay between temperature heterogeneity and lithium plating during fast charging, a phenomenon that poses significant limitations on the performance of graphite-based anodes. Firstly, a custom operando cell with a sapphire window was designed to enable synchronized MWIR thermography and optical imaging of graphite anodes during fast charge. These experimentally reconstructed temperature fields are analyzed alongside a pseudo-two-dimensional (P2D) electrochemical–thermal model that includes a lithium-plating side reaction. The joint analysis clarifies how spatial temperature gradients reshape local overpotentials and accelerate plating onset and explains why surface hot spots seen by IR may not coincide with regions of peak internal heat generation—highlighting the role of current distribution, thermal pathways, and geometric constraints. Secondly, a hybrid modeling–statistical framework, supported by coin-cell experiments and electrochemical simulations, was used to quantify how electrode architecture (e.g., particle size, porosity, thickness, and transport properties) modulates plating risk under fast-charge protocols. Design-of-experiments (DoE) and sensitivity analyses are used to rank variable importance and extract robust design windows that mitigate plating without unduly penalizing power capability. Together, these results connect measurable temperature heterogeneity to the electrochemical conditions that trigger plating and translate physics into actionable electrode-level guidance for the design and development of XFC-capable graphite anodes.The second theme focused on addressing thermal non-uniformity challenges during fast charging by investigating conventional cold plate technologies and a novel immersion cooling system, using both experimental studies and numerical optimization. A multi-domain model of a large-capacity (55 Ah) pouch-cell module was used to evaluate one- and two-sided cold plate cooling strategies across nine EV-relevant charge/discharge profiles and ambient/coolant conditions. The study quantifies trade-offs among peak temperature, ΔT within and across cells, and pumping-power requirements. Further work was focused on the design and optimization of a single-phase immersion cooling system tailored specifically for pouch-type battery modules. Computational Fluid Dynamics (CFD) analysis and multi-objective genetic algorithm were employed to generate Pareto-optimal solutions balancing thermal uniformity (ΔT), peak temperature, hydraulic losses/pressure drop, and packaging volume. The optimization yields interpretable “knee” choices that reduce ΔT with acceptable penalties in pumping power and volume, offering practical guidance for pack-level integration. This multi-themed research endeavor connects electrode-scale heterogeneity and plating physics to module-scale thermal architectures, providing design rules and control-oriented insights for Battery Management Systems (BMS). The work advances the understanding and practical co-design of electrodes and cooling systems for safe, reliable XFC of Li-ion batteries. This work also holds profound implications for the practical advancement of energy storage technologies in various industries.

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