Theoretical predictions vs. experimental measurements of the electrical conductivity of molten Li 2 CO 3 eK 2 CO 3 modified by additives V. Lair a,b, *, V. Albin a,b , A. Ringuede ´ a,b , M. Cassir a,b a Chimie ParisTech, Laboratoire d’Electrochimie, Chimie des Interfaces et Mode ´lisation pour l’Energie LECIME, 75005 Paris, France b CNRS, LECIME UMR 7575, Paris, France article info Article history: Received 30 June 2011 Received in revised form 29 September 2011 Accepted 30 September 2011 Available online 21 November 2011 Keywords: Molten carbonates Additives Conductivity measurements Theoretical predictions Impedance spectroscopy abstract The control of the physicochemical properties of the molten carbonate electrolyte is a key issue for optimising the performance and lifetime of the Molten Carbonate Fuel Cell (MCFC). In particular, the Li x Ni 1x O cathode dissolution should be kept low by increasing the oxobasicity of the electrolyte, which can be done by adding small amounts of alkali or alkali-earth carbonates. Nevertheless, these additives may present drawbacks with respect to other features such as the electrical conductivity. This work aims at determining the evolution of this last property in the classical eutectic used in MCFC, Li 2 CO 3 eK 2 CO 3 (62e38 mol%), containing small amounts of alkaline or alkaline-earth carbonates, such as Ca 2þ , Rb þ , Cs þ , or La 3þ . Experimental conductivity measurements carried out by imped- ance spectroscopy were correlated to theoretical predictions for each carbonate melt as a function of the amount of additive (1e10 mol%) at different temperatures within the range of (550  C < T < 700  C). In both experimental and theoretical cases, the conductivity slightly decreases with the quantity of additives except for the addition of lithium carbonate. The prediction gives general tendency but the calculated values are always lower than experimental ones because the chosen model is too simple. Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 1. Introduction One of the key problems in molten carbonate fuel cell devices is the selection and management of the electrolyte. The general requirements as in any electrochemical generator are a high ionic conductivity and a good chemical stability. The major difficulty is the corrosiveness of molten carbonates leading to the cathode dissolution and the bipolar plates attack; it results a progressive decrease in performances. The state-of-the-art molten carbonate fuel cell nickel cathode, in situ oxidised and lithiated, Li x Ni 1x O, presents a relatively high solubility in the Li 2 CO 3 eK 2 CO 3 (62/38 mol%) conventional electrolyte (up to30 wt. ppm) which can lead to the formation of metallic nickel and occurrence of short-circuits [1]. It is well-known that this dissolution increases with the oxoa- cidity of the carbonate melt and decreases in relatively oxo- basic media [2]. Moreover, the alkali electrolyte can deactivate the catalyst for internal reforming [3,4]. Among the solutions to overcome the degradation problem and to maintain the cell performance is the control of the electrolyte oxoacidity by * Corresponding author. Chimie ParisTech, Laboratoire d’Electrochimie, Chimie des Interfaces et Mode ´ lisation pour l’Energie LECIME, 75005 Paris, France. E-mail address: virginie-lair@ens.chimie-paristech.fr (V. Lair). Available online at www.sciencedirect.com journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 37 (2012) 19357 e19364 0360-3199/$ e see front matter Copyright ª 2011, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.ijhydene.2011.09.153