High Specific Energy Lithium Cells for Space Exploration

The paper discusses development under an ESA TRP activity (Contract No. 4000109879/13/NL/LvH) with a target of high specific energy Lithium-ion cells, capable of operating under low temperature conditions, i.e. −40 °C. Such cells may be encountered in future exploration missions, which do not consider the use of Radioisotope Heater Units. During the activity, ≥1 Ah silicon-based high energy density prototype cells, following components characterization and optimization, were designed, developed, manufactured and tested under room and subzero temperature conditions down to −40 °C. The developed and tested prototype cells exhibited energy density of around 208 Wh/Kg at room temperature under C/10 charge-discharge rate within voltage range of 2.8 V and 4.1 V. Moreover, the prototype cells could retain and deliver more than 75% of their capacity at room temperature upon cycling at −40 °C, demonstrating an energy density of 140 Wh/kg

Activation of catalyst for gas-phase combustion by electrochemical pretreatment

The catalytic activity of an IrO2 catalyst used as an electrode on a YSZ solid electrolyte cell for the gas-phase combustion of ethylene can be increased by electrochem. pretreatment. Thus, the polarization of the IrO2 electrode during 90 min at 300 mA, relative to a gold electrode, both deposited on YSZ, increases the activity of the IrO2 catalyst after current interruption by a factor of 3. In situ catalyst work function measurements showed that after the electrochem. pretreatment the IrO2 catalyst obtains higher work function. The activation of the catalyst is explained through the formation of a higher oxide, IrO2+d. [on SciFinder (R)

Work function and catalytic activity measurements of an IrO2 film deposited on YSZ subjected to in situ electrochemical promotion

In order to investigate the origin of the effect of non faradaic electrochem. modification of catalytic activity (NEMCA), a Kelvin probe was used to measure in situ the changes induced in the work function of an IrO2 catalyst film deposited on yttria-stabilized zirconia upon electrochem. supply of O2- to the catalyst under reaction conditions. Ethylene oxidn. was chosen as a model reaction system. For this purpose an electrochem. reactor of novel design was used in which work function measurements could be carried out in situ during kinetic measurements. It was found that the changes in catalyst work function equal to changes in catalyst ohmic-drop-free potential and that the reaction rate depends exponentially on catalyst work function at low applied potentials. [on SciFinder (R)

Certain specific electrochemical behaviour of some aldehydes. Potentiodynamic investigations

Two distinct specific features have been clearly observed and recorded by cyclic voltammetry in alkaline aldehyde (typical simple aldehydes and monosaccharides) solutions: (a) Heterogeneous reaction of aldehyde group hydrogenation at its higher concentrations removes hydrogen adsorption and desorption peaks in cyclic voltammograms and provides rather high (over 90 percent) current efficiencies at remarkably high current densities (even above 10 mA cm(-2)) for corresponding alcohol yields; and (b) anodic oxidation of the aldehyde group by its specific electrode reaction mechanism suppresses and even prevents any surface oxide growth at noble metal substrates, and thereby creates a new reverse current jump in the anodic range of repeated aldehyde oxidation within the same cycle during the reversal potential scan towards the hydrogen evolution limits. For various aldehydes, including monosaccharides, the surface oxide desorption peak clearly depends in its charge capacity on the rate of oxidation of the aldehyde groups for each individual reactant and/or the number of adsorbed aldehyde groups per unit area of the electrode surface: the smallest was in the presence of formaldehyde, the largest with d-fructose