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Title: Lithium-based inorganic-organic framework materials
Author: Yeung, Hamish Hei-Man
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2013
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This dissertation describes research into lithium-based inorganic-organic frameworks, which has led to an increased understanding of the structural diversity and properties of these materials. The crystal structures of 11 new forms of lithium tartrate, based on chiral, racemic and meso forms of the ligand, have been discovered, including eight anhydrous isomers of dilithium tartrate, Li2(C4H4O6). An experimental and computational study of their formation behaviour and energetics has shown that both kinetic and thermodynamic conditions can be used to control their phase behaviour, and the main structural factors affecting their relative energies were found to be density and hydrogen bonding. Three crystal structures topologically identical to lithium succinate, Li2(C4H4O4), have been discovered using substituted forms of the ligand: lithium L-malate, Li2(C4H4O5), lithium methylsuccinate, Li2(C5H6O4), and lithium tetrafluorosuccinate, Li2(C4F4O4). The cell parameters and mechanical properties of these non-porous frameworks were found to depend on inter-ligand interactions and metal-ligand bond strength. The effects of different ligand substituents on the atomic structure of the binary mixed-ligand solid solution, Li2(succinate)1 x(tetrafluorosuccinate)x, and the ternary system, Li2(succinate)x(L-malate)y(methylsuccinate)z [where (x + y + z) = 1], have also been investigated. Topotactic dehydration of the ligand in lithium L-malate results in the formation of Li2(L malate)1 x(fumarate)x, suggesting a new route to mixed-ligand inorganic-organic frameworks. Investigation into frameworks based on other dicarboxylate ligands produced four structurally diverse lithium-based inorganic-organic frameworks: 2-D frameworks lithium 2,2-dimethylsuccinate, Li2(C6H8O4), and lithium hydrogen D,L-malate, LiH(C4H4O5), and 3 D frameworks lithium fumarate, Li2(C4H2O4), and its singly protonated analogue, lithium hydrogen fumarate, LiH(C4H2O4). A survey of all known lithium dicarboxylates revealed that their structural trends are a function of the ligand geometry, metal:ligand ratio and degree of solvation. The electrochemical properties of nine lithium-based inorganic-organic frameworks were investigated by impedance spectroscopy and electrochemical cycling, revealing many areas to be improved in order for them to become viable materials for battery applications, such as ligand conjugation length, particle size and lithium mobility. Overall, this work has achieved a greater understanding of lithium-based inorganic-organic frameworks, revealing insight into polymorphism, phase behaviour, energetics, topological similarity, mechanical properties, ligand solid solutions, topotactic reaction, structure control and lithium battery properties. In total, 18 new crystal structures and three mixed-ligand solid solution systems are reported. The work provides a solid platform upon which new lithium-containing inorganic-organic materials may be designed and studied.
Supervisor: Not available Sponsor: EPSRC
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral