Engineering topics

Takeuchi, E. S.

Publications and source records attributed to Takeuchi, E. S..

5 records

DOE OSTI2022

Hierarchically structured MoO 2 /dopamine-derived carbon spheres as intercalation electrodes for lithium-ion batteries

A hydrogen peroxide initiated sol-gel process involving molybdenum transformation in the presence of dopamine (Dopa) hydrochloride excess produced the metastable precipitate composed of polydopamine (PDopa) spheres coated with Dopa preintercalated molybdenum oxide, (Dopa) x MoO y @PDopa. The hydrothermal treatment (HT) of the (Dopa) x MoO y @PDopa precursor resulted in the simultaneous carbonization of Dopa and molybdenum reduction generating MoO 2 nanoplatelets distributed and confined on the surface of the Dopa-derived carbon matrix (HT-MoO 2 /C). The consecutive annealing (An) of the HT-MoO 2 /C sample at 600 °C under Ar atmosphere led to the formation of MoO 2 with increased Mo oxidation state and improved structural stability (AnHT-MoO 2 /C). Annealing had also further facilitated interaction between the molybdenum-derived and Dopa-derived components resulting in the modification of the carbon matrix confirmed by Raman spectroscopy. Morphology of both materials is best described as Dopa-derived carbon spheres decorated with MoO 2 nanoplatelets. These integrated metal oxide and carbon structures were tested as electrodes for lithium-ion batteries in the potential window that corresponds to the intercalation mechanism of charge storage. The AnHT-MoO 2 /C electrode showed enhanced electrochemical activity, with an initial specific discharge capacity of 260 mAh/g and capacity retention of 67% after 50 cycles, compared to the HT-MoO 2 /C electrode which exhibited an initial specific discharge capacity of 235 mAh g –1 and capacity retention of 47% after 50 cycles. The rate capability experiments revealed that the capacity of 93 mAh/g and 120 mAh/g was delivered by the HT-MoO 2 /C and AnHT-MoO 2 /C electrodes, respectively, when the current density was increased to 100 mA/g. Here, the improved specific capacity, electrochemical stability, and rate capability achieved after annealing were attributed to higher crystallinity of MoO 2 , increased oxidation state of Mo, and formation of the tighter MoO 2 /carbon contact accompanied by the annealing assisted interaction between MoO 2 and Dopa-derived carbon.

25 ENERGY STORAGE↗

NASA NTRS1998

Improved Li/BCX Primary Cells for Space Applications

Li/BCX (bromine chloride in thionyl chloride) primary cells have been qualified for flight aboard the space shuttle for over fifteen years. These cells provide high energy density while maintaining an excellent safety record. Recently, changes to the electrolyte have resulted in an improved Li/BCX II system with a lower self-discharge rate. The use of low molarity electrolytes in programs unique to NASA have improved the safety hazards tolerance of these cells while maintaining or increasing their energy density.

Spillman, David M.↗

NASA NTRS1990

Low temperature performance of lithium/silver vanadium oxide cells

Lithium/silver vanadium oxide cells for low temperature applications have been developed. Prismatic and spirally wound AA cells were tested under constant load discharge of 0.3 to 1.8 amps or pulse discharge of 0.225 or 1.0 amps at temperatures from -40 to 25 C. At -40 C with current densities of 2.5 mA/cm2, 23 percent of theoretical capacity was achieved under constant load discharge and 40 percent of theoretical capacity was achieved under pulse test. Self-discharge estimates of 0.7 percent per year at 25 C were obtained from microcalorimetry. Preliminary safety testing of the cells revealed no violent performance under short circuit or crush tests.

Takeuchi, E. S.↗

NASA NTRS1988

Improved Li/BCX (thionyl chloride) cells for space applications

New NASA requirements for the screening of lithium cells for space applications involve thermal soaks at elevated temperatures (149 C). The BCX DD and C size cells have been redesigned to pass this test with only marginal losses in capacity as was done previously for the D cells. In addition, the pressure increases in cells subjected to this high temperature environment have been characterized showing that the earlier designs failed this exposure due to lack of void volume. An improve BCX chemistry has been demonstrated which significantly improves voltage delay problems encountered after partial discharge and storage of the cells.

Clark, W. D. K.↗

NASA NTRS1987

Thermal properties and effects for Li/BCX (thionyl chloride) cells

New NASA requirements for the screening of lithium cells for space applications involve thermal soaks at elevated temperatures (149 C). The currently qualified Li/BCX cells and three design modifications have been evaluated showing that a design incorporating a shortened electrode stack met this test condition while continuing to satisfy the performance and safety requirements for cells used on NASA manned space vehicles. Information was also developed to show that measured heat capacities for the BCX D size cells correlated well with the heat generated from cells discharged in an insulated environment. Calculated heat capacities based on the amounts and types of materials in a cell were low compared to these values. This information provides the basis for the design of battery packs in the highly insulating environment of outer space.

Takeuchi, E. S.↗