Youngmin Ko

Solution properties and PGSE-NMR self-diffusion study of C18:1E10/oil/water system

The microemulsion systems of polyoxyethylene-10-oleyl ether/oil/water have been studied. The medium chain triglycerides (MCT) and retinyl palmitate mixture (1:1, w/w) was solubilized up to 9% w/w at the surfactant concentration of 25% w/w. The lowest phase inversion temperature (PIT) of the microemulsion solutions was about 57 8C and showed no phase separation for 6 months at room temperature. The critical micelle concentration (CMC) of polyoxyethylene-10-oleyl ether (C18:1E10) was 1.20/10 5 Ma t 278C. The phase behavior and pulsed field gradient NMR data clearly indicate that these microemulsions are discrete oil-in-water (O/W) microemulsions. The self-diffusion coefficient of free retinyl palmitate, MCT and MCT/retinyl palmitate mixture (1:1, w/w) were 1.61/10 10 , 2.60/ 10 10 and 2.59/10 10 m 2 s 1 , respectively. The D of free C18:1E10 was 4.96/10 11 m 2 s 1 . The relative selfdiffusion coefficients of water and oil differed by more than 1 order of magnitude. The hydrodynamic radius (RH )o f this oil swollen micelle was calculated as 14 nm at 1% w/w oil concentration (23% w/w C18:1E10, 0.5% w/w MCT, 0.5% w/w retinyl palmitate, 76% w/w water) and increased to 34 nm at 7% w/w oil concentration (23% w/w C18:1E10, 3.5% w/ w MCT, 3.5% w/w retinyl palmitate, 70% w/w water). # 2002 Elsevier Science B.V. All rights reserved.

High-efficiency and high-power rechargeable lithium–sulfur dioxide batteries exploiting conventional carbonate-based electrolytes

Shedding new light on conventional batteries sometimes inspires a chemistry adoptable for rechargeable batteries. Recently, the primary lithium-sulfur dioxide battery, which offers a high energy density and long shelf-life, is successfully renewed as a promising rechargeable system exhibiting small polarization and good reversibility. Here, we demonstrate for the first time that reversible operation of the lithium-sulfur dioxide battery is also possible by exploiting conventional carbonate-based electrolytes. Theoretical and experimental studies reveal that the sulfur dioxide electrochemistry is highly stable in carbonate-based electrolytes, enabling the reversible formation of lithium dithionite. The use of the carbonate-based electrolyte leads to a remarkable enhancement of power and reversibility; furthermore, the optimized lithium-sulfur dioxide battery with catalysts achieves outstanding cycle stability for over 450 cycles with 0.2 V polarization. This study highlights the potential promise of lithium-sulfur dioxide chemistry along with the viability of conventional carbonate-based electrolytes in metal-gas rechargeable systems.