Design and synthesis of coordination polymer frameworks for solid-state electrolytes
- UNCG Author/Contributor (non-UNCG co-authors, if there are any, appear on document)
- Pravalika Butreddy (Creator)
- Institution
- The University of North Carolina at Greensboro (UNCG )
- Web Site: http://library.uncg.edu/
- Advisor
- Hemali Rathnayake
Abstract: Current energy storage technologies suffer from low energy density, heaviness, high cost, and materials scarcity. Thus, lightweight, long-lasting, quick charging, eco-friendly, and low-cost battery technology is crucial for the expansion of power electronics and electric vehicle market, which fall short with conventional batteries. Aiming at solving these key shortcomings in current energy storage technologies, this dissertation envisions producing stable, low-cost, and eco-friendly solid-state electrolytes, a critical component in solid-state batteries. The overall objective is to tailor the structure and functionality of materials, which are already in demand for energy storage applications, at the molecular level and explore the lithium-ion conduction in solid state to design next generation lithium-ion conductors, which are superior in function, lightweight, and environmentally benign. Towards this vision, this dissertation research has explored one of the most abundant materials in demand, coordination polymers (CPs) and its subclass of metal-organic frameworks (MOFs), as potential candidates for solid lithium-ion conductors. Utilizing an abundant agricultural waste product precursor, tannic acid, lithium-tannate coordination complex (TALi), a novel bio-based coordination complex, has been synthesized as the very first lithium-based coordination complex for lithium-ion conduction. The structural and compositional analysis revealed the successful formation of microstructures of lithium-tannate coordination network, which is thermally stable up to 250 ºC. The solid-state lithium-ion conduction in TALi was deduced by blending different weight ratios of lithium perchlorate with ethylene carbonate as the plasticizer and lithium-ion mediator. Our temperature-dependent ionic conductance results exhibit ionic conductivity in the range of 1 x 10-5 S/cm to ~ 9 x 10-5 S/cm at room temperature for the optimum salt concentration, establishing the scientific foundation on lithium-ion conduction in lithium-tannate-based coordination complexes. Incorporating Si-O rich silsesquioxane matrix into the lithium-tannate structure, the lithium-ion conduction improved by 10-fold (in the range of 1 x 10-4 S/cm), owing to its high porosity and highly crosslinked silsesquioxane network. Augmenting a base-catalyzed sol-gel polymerization method in the presence of an organoalkoxy silane, porous microstructures of lithium-tannate silsesquioxane coordination polymer was prepared, with size range from 60 nm to 170 nm. Aiming at understanding the isoreticularity of MOFs, the second research project has focused on the lithium-ion conduction in three known isoreticular MOFs with lithium oxide metal nodes using 1,4-benzene dicarboxylic acid (BDC), 2,6-naphthalene dicarboxylic acid (NDC), and 4,4'-biphenyl dicarboxylic acid (BPDC) as organic linkers. A solvothermal approach was used to synthesize highly crystalline microstructures of isoreticular Li-MOFs having monoclinic topology. Compositional, morphology, and thermal analysis confirmed the formation of 3D porous microstructures with framework stability up to 500 ?. These isoreticular Li-MOF-based SSEs showed promising solid-state ionic conductivities in the range of ~10-5 S/cm with activation energies < 0.72 eV. The trend in ionic conductivities of each Li-MOFs at room temperature exhibit no significant effect on the isoreticular expansion, however, the Li+ conduction mechanism in each Li-MOF strongly depends on the reticular expansion of the framework and the size of the pore aperture. The vibronic absorption spectral analysis of the SSEs reveals the Li+ conduction mechanism, allowing us to propose an ion hopping and a vehicle type Li+ conduction mechanisms for these porous solids. Thus, our results could lead to tailor the solid-state Li+ conduction at the molecular level by manipulating framework functionality and pore dimension. [This abstract may have been edited to remove characters that will not display in this system. Please see the PDF for the full abstract.]
Design and synthesis of coordination polymer frameworks for solid-state electrolytes
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Created on 8/1/2023
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Additional Information
- Publication
- Dissertation
- Language: English
- Date: 2023
- Keywords
- Li-MOFs, Lithium-ion conduction, Lithium-tannate frameworks, Lithium-tannate silsesquioxanes, Metal-organic Frameworks, Solid-state Electrolytes
- Subjects
- Lithium ion batteries $x Materials
- Solid state batteries $x Materials
- Electrolytes $x Conductivity
- Metal-organic frameworks
- Coordination polymers