Session: 12-02-02: Modeling of the Fracture, Failure, and Fatigue in Solids

Paper Number: 113196

113196 - Microstructure-Chemomechanics Relations of Polycrystalline Cathodes in Solid-State Batteries 

The future of e-mobility, including electric vehicles, aircraft, and ships, depends on the innovation of battery technology today. Since the energy density of conventional lithium (Li)-ion battery cells with graphite and metal oxides electrodes is limited to about 300 Wh/kg at the cell level, “next-generation batteries” such as the Li-metal all-solid-state batteries (Li-ASSBs) are demanded. The major obstacles preventing the widespread adoption of Li-ASSBs are the rapid degradation and poor rate capacities, which are directly linked to various interfacial issues involving multiple electro-chemo-mechanical processes. Overcoming these interfacial issues calls for a high-fidelity computational model that could be used for exploring the physical mechanisms involved in degradation and for identifying promising remedies through informed synthesis or operating conditions. A Li-ASSB cell is a typical complex engineered system. The modeling of cathode and anode has different fundamental challenges. On the cathode side, the deformation is usually small, but there are various failure mechanisms. Cracks can initiate and propagate along the grain boundaries between primary particles, through the primary particles, through the solid electrolyte (SE), or debonding the interface between particles and SE. On the anode side, interfacial failure mainly stems from lithium dendrite growth and mechanical penetration through the grain boundaries of SE. The biggest modeling difficulty is the complex large-deformation mechanical behavior of pure Li. In this presentation, we will focus on the cathode side. Lithium-nickel-manganese-cobalt-oxides (NMC) embedded in solid-electrolyte are being extensively applied as the composite cathode to match the high energy density of metallic anodes. During charge/discharge, the cathode composite often degrades through the evolution of micro-cracks within the grains, along the grain boundaries, and delamination at the particle-electrolyte interface. Experimental evidence has shown that regulating the morphology of grains and their crystallographic orientations is an effective way to relieve the volume-expansion-induced stresses and cracks, consequently stabilizing the electrochemical performance of the electrode. However, the interplay among the crystal orientation, grain morphology, and chemo-mechanical behavior has not been holistically studied. In that context, a thermodynamically consistent computational framework is developed to understand the role of microstructural modulation on the chemo-mechanical interactions of polycrystalline NMC secondary particles embedded in a sulfide-based solid electrolyte. A phase-field fracture variable is employed to consider the initiation and propagation of cracks. A set of diffused phase-field parameters are adopted to define the transition of chemo-mechanical properties between the grains, grain boundaries, electrolyte, and particle-electrolyte interfaces. This modeling framework is implemented in the open-source finite element package MOOSE to solve three state variables: concentration, displacement, and phase-field damage parameter. A systematic parametric study is performed to explore the effects of aspect ratio, morphological orientation, the crystal orientation of grains, and the interfacial fracture energy on the chemo-mechanical performance of the composite electrode. The findings of this study offer predictive insights for designing solid-state batteries with reduced fracture evolution and stable performance.

Presenting Author: Juner Zhu Northeastern University

Presenting Author Biography: Juner Zhu joined the faculty of Northeastern University as an Assistant Professor of Mechanical and Industrial Engineering in August 2022. Before that, he was a Research Scientist at MIT in Mechanical and Chemical Engineering. He received his Ph.D. from MIT in 2019. His thesis entitled “Mechanical Failure of Lithium-ion Batteries” provided a comprehensive study on the mechanical modeling of battery component materials, porous electrodes, and cells. Dr. Zhu co-developed the 2020-2022 phase of the MIT Industrial Battery Consortium and acted as the Executive Director working with eight world-leading companies in the areas of EV, battery, and consumer electronics. During his postdoctoral career, Dr. Zhu extended his research interests into multiphysics modeling with data-driven methods, including inverse methods, PDE-constrained optimization, and scientific machine learning. Juner has considerable industrial experience from his work as a materials engineer at Ford Motor Company and as a battery analyst at Apple. In 2022, Dr. Zhu was Awarded the Haythornthwaite Foundation Research Initiation Grants by the Applied Mechanics Division (AMD) of American Society of Mechancial Engineering (ASME). In the same year, he co-founded the Center for Battery Sustainability, a joint research program between Northeastern and MIT supported by the industry.

Authors:

Avtar Singh National Renewable Energy Laboratory
Wei Li Northeastern University
Trevor Martin National Renewable Energy Lab
Donal P. Finegan National Renewable Energy Laboratory
Juner Zhu Northeastern University