Session: Government Agency Student Posters

Paper Number: 173020

Microstructure-Informed Mechanical Degradation Pathways in Silicon-Graphite Composite Electrodes 

Silicon-graphite (Si|Gr) composite electrodes are promising candidates for next-generation lithium-ion (Li-ion) batteries due to their commercial viability, high specific capacity, and potential to enable longer-lasting, more energy-dense devices. However, realizing the full potential of these electrodes is challenged by their mechanical and electrochemical stability during repeated charge–discharge cycles. In particular, increasing the silicon (Si) content, which offers over ten times the theoretical capacity of graphite (Gr), leads to rapid degradation and capacity loss, limiting its practical use in commercial cells. The primary cause of this degradation lies in the substantial volume expansion that Si undergoes during lithiation (approximately 300%), which induces severe mechanical stresses within the electrode microstructure and often lead to fracture of active particles of Si and Gr. This mechanical degradation initiates a cascade of degradation pathways, including the loss of electrical connectivity, loss of active material, exposure of fresh surfaces leading to parasitic side reactions (the growth of new solid electrolyte interphase (SEI) layer) that irreversibly consume lithium. These mechanisms are strongly coupled, reinforcing each other and accelerating capacity fade. To investigate these coupled degradation pathways, we develop a multiphysics electrochemical-mechanical framework incorporating a phase-field formulation for fracture. The framework is implemented on electrode microstructure that is directly reconstructed from high-resolution X-ray computed tomography of a commercial composite electrode, enabling high-fidelity simulations of electrochemical and mechanical interactions between the Si, Gr and pore phases. The model accurately captures the electrochemical interplay between the Si and Gr phases, leading to microstructure-dependent spatial inhomogeneities in reaction kinetics and stress distributions, that lead to preferential fracture zones in Si particles. We quantify the coupled effects of mechanical damage on loss of usable active material and SEI growth on newly formed surfaces and track the progressive loss of capacity over cycles. The model reveals distinct degradation pathways in Gr and Si, with Gr experiencing local fracture in the first cycle and remains stable while mechanical degradation of Si continues to accumulate over cycles. Two degradation modes in Si are highlighted, identifying critical conditions under which Si is progressively rendered electrochemically inaccessible to store Li due to mechanical failure. Finally, we propose operational and microstructural strategies to mitigate mechanical damage, improve material utilization, and extend cycle life, and enable robust high-Si content composite electrodes. By bridging high-resolution, realistic, three-dimensional electrode microstructures with mechanics informed multiphysics modeling, this work delivers new insights into the electro-chemo-mechanical failure mechanisms in next-generation battery electrodes. It highlights the critical role of mechanics in determining electrode reliability and performance, providing guidance for the development of robust, high-capacity Li-ion battery electrodes.

Presenting Author: Sameep Rajubhai Shah Purdue University

Presenting Author Biography: Dr. Sameep Shah is a postdoctoral researcher in the School of Mechanical Engineering at Purdue University. He received his Ph.D. from the School of Mechanical Engineering at Purdue University in 2025. His research lies at the intersection of mechanics and transport phenomena, with interest in their applications in energy storage and biopharmaceutical delivery. His research interest focuses on studying the intimate coupling between mechanics and electrochemistry in Li-ion batteries, and poroelastic flow in biological systems, through the development of integrated physics-based computational models for these coupled nonlinear systems.

Authors:

Sameep Rajubhai Shah Purdue University
Kejie Zhao Purdue University