2025 Theses Doctoral

Fabrication and Modeling of Thick Alkali-Ion Electrodes

Hu, Kedi

The adoption of renewable energy in place of fossil fuels for grid-scale electricity generation requires low-cost storage systems. In battery energy storage systems, thick electrodes, with their reduced inactive material content and potential for higher energy density, are a promising pathway to achieve these goals. However, as electrode thickness increases, so do the challenges associated with mass transport, which can lead to poor rate performance and premature cell failure. This dissertation explores the fabrication, modeling, and optimization of thick electrodes for alkali-ion batteries, with a focus on both lithium and sodium chemistries.

This work first introduces a solvent-free fabrication method for thick electrodes and investigates the transport properties of dry-pressed thick lithium-ion electrodes using a physics-based model (Chapter II). Millimeter-thick electrodes demonstrate strong capacity utilization at charge and discharge rates relevant to diurnal grid storage, but utilization at higher rates is inhibited by mass transport limitations arising from high thickness and tortuosity. The study of these limitations is expanded in Chapter III, which introduces the concept of polarization-driven saturation in the electrolyte, a previously under-examined transport phenomenon that further constrains performance. Analytical expressions for the limiting current in both depletion and saturation conditions are derived, which can be used to predict limiting transport conditions across other electrode-electrolyte systems. Chapter IV extends the modeling framework built in the previous two chapters to a cylindrical geometry, presenting a model for thick cylindrical electrodes that is used to optimize the design of a lithium-ion bobbin cell.

Finally, Chapter V explores the use of thick electrodes in lithium-ion and sodium-ion full cells, demonstrating the feasibility of using dry fabrication techniques to create high-loading alkali-ion batteries. Through a combination of experimental and theoretical approaches, this dissertation provides a comprehensive framework for understanding and overcoming the transport limitations that hinder the commercialization of thick electrodes.