Session: 04-21-01: Dynamics of Advanced Functional Materials and Structures

Paper Number: 164102

Electrochemo-Mechanical Coupling in Electrode Materials Under Electrolyte-Induced Interactions 

The mechanical properties of electrode materials are critical to the mechanical, electrical, and thermal performance, safety, and durability of lithium-ion batteries (LIBs). While mechanical testing is often conducted to elucidate the fundamental behavior of electrode materials, most existing studies focus on dry electrodes, which fail to fully capture the in-cell conditions. To address this gap, this study provides a comprehensive investigation of the coupled effects of SOC, electrolyte, and strain rate on the mechanical behavior of battery components, i.e., cathodes, anodes and separator, through compression and tensile testing. Batteries were first charged to virous states of charge (SOCs), i.e., 20% and 40%, and then disassembled in a controlled inert environment to extract the electrode and separator materials. To account for the electrolyte effect, the electrode was soaked in the electrolyte for a sufficient duration. Compressive tests were performed by stacking multiple layers of material to simulate the out-of-plane compression in a battery. Additionally, tensile tests were conducted on single-layer samples to evaluate the in-plane mechanical properties of each battery component. The study begins by isolating the impacts of SOC and electrolyte individually, followed by an analysis of their coupling effects. Scanning electron microscopy (SEM) characterization is employed to uncover the underlying mechanisms driving these behaviors. Strain rate effects were investigated along with electrolyte and different SOCs. The results show that a higher SOC increases the modulus of the anode while decreasing the modulus of the cathode. This behavior is attributed to volume variation, phase transitions in the materials, and binder degradation. By treating electrode active materials as granular materials, the electrolyte influences mechanical performance through two distinct stages, depending on its concentration within the electrode particles. A force-enhancing liquid bridge at low electrolyte concentrations and a lubrication effect at high electrolyte concentrations result in distinct mechanical behaviors. A higher strain rate decreases the modulus of wet electrode materials but increases the modulus of separators. This behavior corresponds to the properties of the materials, with electrodes exhibiting granular characteristics and separators behaving as polymer materials. By analyzing the combined effects of SOC, electrolyte, and strain rate, an interplay among these three factors was observed, significantly impacting the mechanical response of the electrodes. While These findings offer critical insights into the behavior of battery components under realistic loading conditions, demonstrating the complexity of the coupling of solid-liquid interactions in porous materials, and providing a foundation for improving the evaluation and design of LIB safety and durability.

Presenting Author: Shuguo Sun University of Delaware

Presenting Author Biography: Shuguo Sun is a Ph.D. student at University of Delaware. His research focuses on the mechanical, thermal and electrochemical behavior of lithium-ion batteries, with a particular emphasis on mechanical failure, internal short circuits, and thermal runaway. Shuguo Sun has expertise in bat.

Authors:

Shuguo Sun University of Delaware
Bo Rui University of Delaware
Xijun Tan University of Delaware
Jun Xu University of Delaware