Dissertation
First principles and thermodynamics approach to understanding metal release from complex metal oxides
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2021
DOI: 10.17077/etd.006256
Abstract
Nanoscale complex metal oxides (CMOs) have transformed how technology is used around the globe. One of the most widespread examples are their use as the electroactive component in lithium-ion batteries (LIBs). LIBs are used in most portable electronics, such as smart phones, laptops, tablets, and electric cars. Currently, there is no fiscal incentive to develop proper LIB disposal protocols, therefore, these batteries and their components end up in landfills that runoff to aqueous environments. Though much of the functionality of these battery components have been optimized, the environmental interaction and impact is not widely understood. In this research, we investigate the transformation of the nanoscale CMOs that makes-up LIB cathodes. The most widely used cathode material is LiCoO2 (LCO) and it is the base structure of our studies. We combine density functional theory (DFT) and thermodynamics methodology to investigate and explain the processes of Co release from the LCO lattice. We define an upper- and lower-bounds for favorable release from the surface across a range of pHs. Since cobalt is expensive and not Earth-abundant, a more complex structure was developed to reduce the cost and increase the capacity of this cathode material. To do this, we replace 1/3 of the Co with Ni and 1/3 of the Co with Mn to have Li(Ni1/3 Mn1/3 Co1/3)O2 (NMC). Exposing Shewanella Oneidensis, a bacteria that plays a large role in the cycling of metals in the environment, to NMC in water has shown to have an adverse response. Ultimately, the bacteria die due to the release of Ni and Co metal cations into solution. Although the lattice contains equal parts of each metal, the amount of metal ions in solution is mostly Li, then Ni followed by Co and Mn. We used our DFT and thermodynamics methodology to reproduce this incongruent metal release trend and used electronic structure calculations to explain the mechanism. We then use compositional tunning to control the release and reduce biological impact by increasing the amount of Mn in the lattice. We found that increasing the amount in Mn actually increases the thermodynamic favorability for metal release by destabilizing the solid in solution. We used this insight to further compositionally tuning the lattice by replacing with metals with those that were cheaper, Earth-abundant, and stable in the lattice across a range of pHs. We replace Ni and Co with other metals such as Al, Fe and Ti, to suggest compositions for battery cathodes that are environmentally benign. We also tested the functionality of these compositions by calculating the voltage. We found that these CMOs are more stable and have similar voltage capacity as NMC. With our methodology, we captured the initial metal release mechanism and suggested potential compositions for future battery materials. To understand long-time ( 72 hours) exposure of NMC to water, we increased the complexity of our DFT and thermodynamics model to include the next steps in this dissolution process. By removing more than one M-OH unit from the surface, we can uncover additional factors that contribute to metal release such as vacancy site proximity and surface protonation events.
Details
- Title: Subtitle
- First principles and thermodynamics approach to understanding metal release from complex metal oxides
- Creators
- Diamond Tekeria Jones
- Contributors
- Sara E Mason (Advisor)Tori Z Forbes (Committee Member)Christopher M Cheatum (Committee Member)Leonard R MacGillivray (Committee Member)James J Shepherd (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Chemistry
- Date degree season
- Autumn 2021
- DOI
- 10.17077/etd.006256
- Publisher
- University of Iowa
- Number of pages
- xiv, 161 pages
- Copyright
- Copyright 2021 Diamond Tekeria Jones
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 143-161)
- Public Abstract (ETD)
Nanoscale complex metal oxides (CMOs) have transformed how technology is used around the globe. One of the most widespread examples is their use as the electroactive component in lithium-ion batteries (LIBs). LIBs are used in most portable electronics, such as smart phones, laptops, tablets, and electric cars. There is projected to be millions of tons of LIB disposed into landfills by 2030, where the component run-off will end up in aqueous environments. Little is known about the environmental impact of this interaction. The work presented here focuses on the transformation of these battery materials, specifically metal dissolution from the nanoscale LIB cathode material. We use a unique combined theory and experimental method that provides mechanistic insight into this process. We use this insight to predict potential replacement battery cathode materials made from cheap and Earth-abundant metals.
- Academic Unit
- Chemistry
- Record Identifier
- 9984210526502771
Metrics
2 File views/ downloads
122 Record Views