Leigh Anna Marie Steele

Synthesis and characterization of 4,4′-methylenebis (2,6-di-tert-butylphenol) derivatives of a series of metal alkoxides and alkyls

Investigation of the coordination behavior of 4,4′-methylenebis(2,6-di-tert-butylphenol) (or H2-4DBP) with a series of metal alkoxides led to isolation of [(OR)3M]2(µ-4DBP), where M/OR = Ti/OBut (2), Ti/ONep (3), Zr/OBut (4), Hf/OBut (5), and [(py)(OR)3M]2(µ-4DBP) · py (5a), where py = pyridine and ONep = OCH2C(CH3)3. Metal alkyl derivatives of 4DBP were also studied and found to form similar di-substituted species: [(py)2(Et)Zn]2(µ-4DBP) · py (6), [(THF)3(Br)Mg]2(µ-4DBP) (7), [(THF)2(Br)Mg](µ-4DBP)[Mg(Br)(THF)3] · (THF, tol) (7a), and [(py)(R)2Al]2(µ-4DBP), where R = CH3 (8), Et (9), CH2CH(CH3)2 (10); tol = toluene and THF = tetrahydrofuran. All structures demonstrate the bridging nature of 4DBP and the ability to bind a variety of metal centers. Solution state NMR indicates that the structures of 2–10 are retained in solution. Thermal analyses indicate that 4DBP is preferentially lost during heating.

Structural diversity in a series of alkyl-substituted cesium aryloxides.

A family of cesium aryloxides [Cs(OAr)](n) were synthesized and structurally characterized from the reaction of 1:1 or 1:excess stoichiometry of Cs(0) and the appropriate alkyl-substituted phenol: 2-alkylphenol [alkyl = methyl (H-oMP), isopropyl (H-oPP), and tert-butyl (H-oBP)] and 2,6-dialkylphenol [alkyl = methyl (H-DMP), isopropyl (H-DIP), tert-butyl (H-DBP), and phenyl (H-DPhP)]. The products were structurally identified as [Cs(oMP)(H-oMP)(2)](n) (1), [Cs(5)(oPP)(5)](n) (2), [Cs(4)(oBP)(4)(H-oBP)(6)](n) (3x, shown), [Cs(3)(DMP)(3)](n) (4), [Cs(2)(DIP)(2)](n) (5), [Cs(DIP)(H-DIP)](n) (5x), and [Cs(DPhP)](n) (7). Compounds 1-7 were found to adopt complex polymeric structures employing π interactions from the neighboring pendant phenoxide ligands. The solution behavior of these compounds was studied using solution (133)Cs NMR spectroscopy, and for each compound, a single (133)Cs NMR resonance was observed, with chemical shift values found to be strongly solvent-dependent. This implies that monomeric cesium salt species involving solvent interactions exist in solution.

Propagation testing multi-cell batteries.

Propagation of single point or single cell failures in multi-cell batteries is a significant concern as batteries increase in scale for a variety of civilian and military applications. This report describes the procedure for testing failure propagation along with some representative test results to highlight the potential outcomes for different battery types and designs.

Synthesis and characterization of a series of rubidium aryloxide compounds

A series of rubidium aryloxides, [Rb(OAr)(solv) n ] x , was synthesized from the reaction of Rbo with a select set of 2-alkyl phenols [alkyl = methyl (H-oMP), iso-propyl (H-oPP), and tert-butyl (H-oBP)] and 2,6-di-alkyl phenols [alkyl = methyl (H-DMP), iso-propyl (H-DIP), and tert-butyl (H-DBP)]. The products were identified by single-crystal X-ray diffraction as [Rb5(μx-O)(ηx,μx-oMP)3] n (1), [Rb4(ηx,μx-oPP)4(py)] n (2), [Rb(μ3-oBP)(ηx-tol)]6 (3), [H]2[Rb7(O)(ηx,μ-DMP)7(py)2] n (4), and [Rb(η6,μ x -DIP)] n (5) (where ηx and μx indicate an undetermined amount of the specified interaction). Acceptable crystals of the DBP derivative could not be grown in our hands. In contrast to the solvated polymeric K and unsolvated Cs derivatives, the Rb derivatives were a mixture of solvated and unsolvated polymers and for the first time some were isolated with oxo ligands. NMR studies indicated that these compounds become smaller symmetric species upon dissolution.

Quantification of Lithium-ion Cell Thermal Runaway Energetics

Much of what is known about lithium-ion cell thermal runaway energetics has been measured and extrapolated from data acquired on relatively small cells (< 3 Ah). This work is aimed at understanding the effects of cell size on thermal runaway energetics on cells from 3 to 50 Ah of both LiFePO4 (LFP) and LiNi0.80Co0.15Al0.05O2 (NCA) chemistries. Results show that for both LFP and NCA cells, the normalized heating rate (W/Ah) increases roughly linearly for cells from 3-38 Ah while the normalized total heat released (kJ/Ah) is relatively constant over that cell size range. The magnitude of the normalized heating rate is on the order of 2x greater for NCA relative to LFP chemistries for 2-3 Ah cells, while that difference is on the order of 10x for 30-40 Ah cells. The total normalized heat release is ~ 15-20% greater for NCA relative to LFP cells across the entire size range studied 3-38 Ah.