Molten carbonate fuel cell research at ORNL

Abstract

implied, or assumes any legal liability or responsibility forthe accuracy, completeness or usefulness of any information, apparatus, product or process d~scloSM, 6r tbptesents tnat ~rs use WOUld nor Infringe prlvululy UWIIUJ 1iyl11a.

Steady‐State Composition Profiles in Mixed Molten Salt Electrochemical Devices: I . Lithium/Sulfur Battery Analogs

“…(2), Equation 14]. The general one dimensional flux expressions may be written --JL* = D 0eL --ML* I/F [1] 0} --JK* = DOCK _ ME* I/F [2] 0}…”

“…(2), Equation 14]. The general one dimensional flux expressions may be written --JL* = D 0eL --ML* I/F [1] 0} --JK* = DOCK _ ME* I/F [2] 0} where the Ji*'s are the flows of ions i (in equivalents) relative to the reference frame*. D is interdiffusion coefficient of L and K, the Ci's are the equivalent concentrations, the Mi*'s are migrational terms related to the transference numbers in the appropriate reference frame, and flows, concentrations, and migrational terms also satisfy the relations…”

“…Electrochemical devices employing mixed electrolytes and operated at high current densities, such as molten salt batteries and fuel cells (1,2), are subject to composition gradients resulting from the faradaic and migrational processes occurring at the electrodes, a phenomenon we have referred to as migrational polarization. Since such composition gradients can have significant effects on the performance of molten salt batteries and fuel cells, an understanding of the phenomenon and its characterization is important to design and modeling studies (3).…”

Transport of Electrolyte in Molten Carbonate Fuel Cells

“…Although a higher mobility of the lithium ion has been inferred from voltage relaxation data for an equimolar mixture of lithium and potassium carbonate (17) actual measurements of mobilities indicate that the lithium ion has a lower mobility than that of other alkali metal ions in sulfates (18), chlorides (19), bromides (20), and nitrates (21) over wide ranges of concentration. This high potassium content is evidently not caused by selective vaporization of lithium from this region by some mechanism, because the lithium was found in the lower, more positive regions of the gasket.…”

Steady‐State Composition Profiles in Mixed Molten Salt Electrochemical Devices: II . Molten Carbonate Fuel Cell Analogs

“…The electrodes thus behave phenomenologically as membranes permeable to carbonate ions but impermeable to Li + or K + ions (here designated L and K). In this case the migrational term becomes (2) /P/K V = tK c --XK and the boundary conditions at the two electrodes separated by a distance ~ are JL v=JK v=0 at ~=0 (anode) and at ~ =~ (cathode) [4] where the superscript V corresponds to the constant volume reference frame.…”