NiO Cathode Dissolution and Ni Precipitation in Li/Na Molten Carbonate Fuel Cells: Distribution of Ni Particles in the Matrix

Abstract

Due to the dissolution of the lithiated nickel oxide cathode, the life expectancy of a molten carbonate fuel cell is reduced. The use of a Li/Na carbonate electrolyte is expected to lead to a higher voltage and a longer life expectancy due to its higher ionic conductivity and its lower nickel oxide cathode solubility. Using the Li/Na electrolyte, single cells have been tested to evaluate their performance and their life expectancy. Empirical equations for these cells have been presented to determine the temperature, the CO2 partial pressure in the cathode gas, and the matrix thickness. The results prove that the life expectancy of Li/Na cells is reduced by nickel short-circuiting in comparison to Li/K cells, for which the life expectancy is many times longer. The dependence of the nickel-containing particle distribution in the matrix on the temperature has been evaluated using an image processing method. At 973 K, most of the particle distribution moves toward the anode more rapidly than at 873 K, because the rate of particle growth is lower at the higher temperature, and the particles move toward the anode due to the convection of the molten carbonate in the matrix. The initiation time for nickel short-circuiting was derived from he results of this study to explain the relationship between the shorting conductance and the volume of nickel-containing materials in the matrix porosity. Moreover, the results show that the predominant element contributing to short-circuiting is the nickel oxide, and not the metal. © 2001 The Electrochemical Society. All rights reserved.

Direct Fuel Cell Materials Experience

“…In terms of cathode dissolution, NiO dissolves slowly into the electrolyte as Ni +2 ions according to an acidic dissolution mechanism (NiO ↔ Ni +2 + O = ), which are then reduced to metallic nickel by the hydrogen diffused from the anode side (15). The deposition of Ni into the matrix may cause electric shorting, decreasing stack life.…”

SnO2 coated Ni particles prepared by fluidized bed chemical vapor deposition

“…Taking into account economical factors in addition to the above requirements, Ni appeared to be a good candidate. Indeed, it has been used as an electrode material in various electrochemical processes [17].…”

“…The formation of nickel oxide on the Ni particles does not prevent the use of these treated particles as anode materials because NiO exhibits a sufficiently high conductivity and its formation in this CVD process is quite limited. It is a p-type semi-conductor that has been used previously as electrode material for various electrochemical processes [17].…”

Oxygen Reduction Reaction at LaNiO3 Supported by Au Ring in Li/Na Eutectic Carbonate with La2O3

“…(6)(7)(8)(9)(10)(11) The lithiated nickel oxide is now used for the cathode of MCFCs because of their high conductivity, stability, and catalytic activity of oxygen reduction reaction (ORR) in molten carbonates. (12)(13) However, especially under high pressure, the cathode of NiO dissolves into the electrolyte and then occurs the internal short circuit (Ni shorting) (14)(15)(16)(17)(18) during a long time operation. As for the widespread commercialization of MCFCs, the material of their cathode should be more stable for longer time operation in order to get higher reliability.…”