Battery Design for Improved Resiliency Against Internal Shorting

Date of Award

5-1-2025

Degree Name

Ph.D. in Electrical Engineering

Department

Department of Electrical and Computer Engineering

Advisor/Chair

Jitendra Kumar

Abstract

Lithium-ion batteries (LIBs) are a cornerstone of next-generation electric aircraft, offering high energy density, power density, and long cycle life. However, these attributes introduce safety challenges, particularly the risk of thermal runaway (TR), which poses significant concerns in high-energy, high-power applications. This study addresses these challenges by investigating LIB systems’ structural, thermal, and mechanical under extreme conditions and proposing engineering solutions to enhance safety and performance by improving resiliency against internal electrical shorting. A key focus of this work is the detection and mitigation of internal short circuits (ISC), a primary trigger for TR. ISCs can result from mechanical abuse or the formation of lithium dendrites in which a metallic object internally connects anodes and cathodes, leading to a fast battery discharge and consequent heat generation. Advanced sensing layers that detect early dendrite growth are demonstrated, providing a critical safety feature. Techniques to distinguish dendrite-induced changes from routine operational behaviors are discussed, emphasizing the need for continued algorithm development for practical application. These innovations hold promise for integration into battery management systems (BMS), enhancing overall system safety while maintaining performance. To mitigate mechanical abuse risks, this study explores materials (battery enclosure) and configurations to improve LIB safety and functionality for a wide range of applications, including aviation. Titanium (Ti) is an optimal material for battery enclosures due to its superior thermal and mechanical properties and moderate gravimetric density. Among three widely used LIB formats, viz. cylindrical, prismatic, and pouch, pouch cell formats offer advantages in weight and compactness, they require enhanced protection to withstand mechanical stress and prevent TR. Modular designs and optimized secondary enclosures are proposed to improve battery mechanical resiliency and, hence, safety needed for applications in electronics, electric vehicles, and electric/hybrid aircrafts. Finally, experimental findings on LIB safety behavior under high-speed impact conditions, simulating aircraft crash scenarios, are presented. Tests on the pouch and cylindrical LIB cells (NMC and LFP chemistries) reveal the high vulnerability of unprotected cells to damage and TR at speeds exceeding 50 mph. The addition of protective enclosures significantly improved survivability, with cells enduring impacts up to 150 mph. Though, these results provide insights into optimizing protective designs to meet typical aircraft velocities (500–700 mph), the knowledge can be applied to improve the high-speed collision safety of electric vehicles as well. By integrating advancements in ISC detection, protective enclosure design, and high-speed impact testing, this work outlines a comprehensive approach to enhancing the safety, reliability, and performance of LIBs in a wide range of applications, including electric vehicles and electric aircraft. Future efforts will focus on further refining these strategies for modular battery systems, contributing to the implementation of sustainable and safe energy storage systems for electric vehicles and electric aviation.

Keywords

Electrical Engineering

Rights Statement

Copyright 2025, author.

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