Enabling extreme fast charging systems in electric vehicles through thermal management and thermophysical property characterization

Extreme fast charging (XFC) systems have emerged as a critical area of focus in the evolution of electric vehicles (EVs). These systems aim to drastically reduce charging times, bringing them closer to the convenience of traditional refueling and potentially accelerating EV adoption. However, achieving XFC charging times of under 10 minutes from 0 to 80% requires charging currents in the range of 1000–1200 A at the vehicle scale and sustained 6C charge rates at the battery cell level, presenting significant thermal challenges. This dissertation explores these challenges comprehensively, addressing the thermal behavior of fast charging cables, batteries, and thermophysical property measurements of next-generation anode materials. The research begins with the thermal management of single-phase liquid-cooled charging cables and connectors for high-current vehicle chargers. The heat generated in these components increases quadratically with current, necessitating effective thermal management to ensure safety and efficiency. Electrothermal models were developed to evaluate the impact of design parameters such as cable size, connector geometry, insulation conductivity, and cooling fluid properties. Additionally, the role of current splitting was explored as a mitigation strategy. A system-level model integrating the cable and connector analyses examined the influence of various cooling topologies on overall temperature distribution. These findings highlight the feasibility of single-phase liquid cooling for XFC systems and identify limiting factors at high currents. Building on the insights from vehicle-level thermal challenges, the study next examines thermal behavior at the cell level, focusing on lithium-ion battery cells subjected to 6C charge rates. Using an electrothermal model enriched with detailed geometric and material parameters, this study investigates heat generation and temperature gradients within cylindrical cells (18650, 2170, and 26650). Furthermore, the role of thermal conductivity in improving the efficacy of side cooling is examined, alongside a comparative analysis of side and bottom cooling strategies. The results emphasize the importance of innovative cell design to address the thermal challenges posed by XFC, paving the way for safer and higher-performance batteries. Recognizing the importance of thermal conductivity to cell-level performance, the research culminates with an innovative approach to characterizing thermophysical properties at the material level. A novel method is developed to measure the thermal conductivity of nickel scaffolds, which serve as structural frameworks in structured silicon anodes for high-energy-density lithium-ion batteries. These scaffolds are thin and highly porous, making them difficult to characterize using conventional methods. The developed method integrates thermal imaging with iterative computational fluid dynamics and heat transfer (CFDHT) simulations. A physics-based parameter iteration algorithm was employed to ensure rapid convergence and accuracy. The method was validated against commercially available foams and solid materials, demonstrating its robustness. Application of this method to in-house fabricated nickel scaffolds revealed valuable insights into their thermal properties, underscoring the importance of innovative cell design for thermal management for next-generation batteries. Together, these studies form a connected exploration of the thermal challenges in XFC systems, starting from system-level components, progressing through battery-level behavior, and culminating in material-level characterization. This multi-scale approach highlights the need for integrating thermal management considerations across design levels to support the development of efficient, safe, and robust XFC systems. The findings aim to contribute to the broader pursuit of reliable and high-performance EV systems.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Gurumukhi, Yashraj

Contributors dc:contributor

• Miljkovic, Nenad
• Braun, Paul V
• Wang, Pingfeng
• Wang, Xiaofei

• Batteries
• Thermal management
• Thermal conductivity estimation
• Porous materials
• Charging cables.

Statement dc:rights

• Copyright 2025 Yashraj Gurumukhi

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/129483

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F129483