Date of Award
1-1-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Mechanical Engineering and Applied Mechanics
Department
Mechanical, Industrial and Systems Engineering
First Advisor
Ashutosh Giri
Abstract
Rechargeable batteries are paramount to the further development of green energy infrastructure as they allow for energy storage during peak production times, energy distribution during off-peak times, and provide the impetus to transition away from standard combustion engines in the transportation sector. The ability for rechargeable batteries to safely charge and discharge over multiple cycles is key to their successful application and long-term use. Moreover, the growing use of rechargeable batteries necessitates designs utilizing materials that are abundant and accessible to meet the ever-increasing demands required by the green energy and transportation sectors.
To address these needs, we first investigate a form of carbon, called graphullerene, that consists of C60 molecules covalently bonded together in molecular sheets and stacked together, similar to the layered structure of graphite. Moreover, the fabrication of this material utilizes magnesium atoms that are removed afterwards, suggesting a possible use in magnesium-based batteries. We find that the graphullerene structure is endowed with exceptional thermal properties with a greater ability to conduct heat when compared with alternative cathode materials. Additionally, the mechanical and electronic properties of graphullerene are similar to those of commonly used cathode materials, highlighting its potential as a cathode in a magnesium battery. Finally, we test the feasibility of a hypothetical Mg-graphullerene battery through density functional theory calculations, where limitations in the operating voltage and ionic diffusion are observed. We offer potential application spaces where a hypothetical Mg-graphullerene battery could operate and conduct additional simulations to determine design strategies to improve the ionic diffusion within the graphullerene structure.
We then move to investigate fundamental aspects of heat transfer that occur in battery materials, as an inability to dissipate heat is a common cause of catastrophic battery failures during operation. In thin films, ubiquitous in electronics and battery systems, the intrinsic thermal conductivity is significantly reduced as energy carriers are unable to diffusely scatter. However, through careful design of thin films, we observe up to a 7 times increase in the thermal conductivity compared to a film with no modifications. In 2D porous frameworks, which have seen increased usage in the battery realm, structural modifications to the framework can affect the species selectivity and ion uptake. However, the effect on the thermal properties of organic frameworks caused by these modifications remains relatively unknown. In this case, we find that the addition of functional groups onto the porous framework increases the cross-plane (van der Waals direction) thermal conductivity while having a limited effect on the in-plane thermal conductivity. We attribute this behavior to the presence of energy carriers localized to the functional groups that are able to efficiently carry heat across adjacent 2D layers. Finally, we seek to investigate the nanoscale heat transfer characteristics at the active material/electrolyte interface within the electrode. By varying the number of Li+ ions adsorbed onto the active material surface, we find an increase in the thermal boundary conductance across the active material/electrolyte interface. However, depending on the size of the conducting salt, the mechanisms of increase is due to either anion adsorption and vibrational coupling, or structuring of the electrolyte near the interface. We also compare the thermal resistances present in the electrode and find that the resistance posed by the active material/electrolyte interface can contribute up to 60% of the total thermal resistance in the electrode and must be taken into account when performing multiscale thermal modeling of battery electrodes.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Dionne, Connor Jaymes, "COMPREHENSIVELY UNDERSTANDING AND MANIPULATING THE HEAT TRANSFER MECHANISMS IN NEXT-GENERATION BATTERY MATERIALS" (2025). Open Access Dissertations. Paper 4450.
https://digitalcommons.uri.edu/oa_diss/4450