Doctoral Defense - Affan Malik

About the Event

The Department of Chemical Engineering and Materials Science

Michigan State University

Ph.D. Dissertation Defense

Thursday, September 19th, 2024 at 2:00 PM EST

Seminar Room 3540 Engineering Building

ABSTRACT

MULTIPHYSICS ELECTROCHEMICAL SIMULATIONS OF LITHIUM-ION BATTERY ELECTRODE MICROSTRUCTURES

By: Affan Malik

Advisor: Dr. Hui-Chia Yu

Energy storage technologies are key to a future of less reliance on fossil fuels and cleaner energy. Rechargeable batteries, particularly lithium-ion batteries, have become a mainstay in energy storage, notably in electric vehicles and mobile applications. However, optimizing their performance to achieve faster charging, increased capacity, and higher utilization remains a challenge. Accomplishing these goals requires a microscopic-level understanding of battery electrodes, which is hindered by their complex morphologies. Computer simulations can bridge this gap by providing insights into microstructure phenomena. A framework combining smoothed boundary method (SBM) and adaptive mesh refinement (AMR) is introduced to model and study electrode microstructures. This framework is implemented with finite difference methods (FDM) and parametrized with material properties from literature. We demonstrate the framework's usage and effectiveness with half-cell simulations of Li_xNi_1/3Mn_1/3Co_1/3O₂ (NMC-333) cathode through one-dimensional and three-dimensional simulations on synthetically generated microstructures. A crucial goal of our work is studying lithium plating on electrodes which is a major obstacle in realizing an electrode's true theoretical capacity and fast charging. Graphite, the predominant anode material in lithium-ion batteries, is particularly prone to lithium plating, especially at fast charging conditions. Thus, modeling graphite is critical to grasp the dynamics of lithium-ion batteries and lithium plating. Graphite anode undergoes phase transformations under lithiation. Incorporating the Cahn-Hilliard phase-field equation into the framework allows for detailed and more accurate simulations of these phase transformations in graphite anodes. Using the developed framework for graphite, we identified overcharging conditions, the influence of particle size, and the importance of pore tortuosity on real reconstructed electrodes. The framework can facilitate the design of thick electrodes, promising higher capacity without experimental construction.

Furthermore, the framework allowed us to examine two different approaches to delay lithium plating in graphite. A thermodynamic approach of hybrid anodes where we mix graphite with hard carbon and a kinetic approach of tunnels where we introduce synthetic channels in the electrode. Through our simulations, we identify that hard carbon particles act as a buffer for lithiation in hybrid anodes, delaying the surface saturation of graphite particles and thus delaying the lithium plating on graphite. On the other hand, creating tunnels generates easier paths for ion diffusion and therefore leads to better utilization of the electrode. Such channels in thick electrodes can generate high-capacity and efficient electrodes. Finally, the development of this framework culminates with a demonstration of full-cell simulations. In summary, simulating electrochemical processes in complex electrode microstructures is streamlined by the presented framework and offers a fast and robust tool for designing and studying microstructures. 

Persons with disabilities have the right to request and receive reasonable accommodation. Please call the Department of Chemical Engineering and Materials Science at 355-5135 at least one day prior to the seminar; requests received after this date will be met when possible.