Performance analysis of molten carbonate fuel cell using a Li/Na electrolyte

doi:10.1016/S0378-7753(02)00468-8

Journal of Power Sources

Volume 112, Issue 2, 14 November 2002, Pages 509-518

https://doi.org/10.1016/S0378-7753(02)00468-8 Get rights and content

Abstract

Several years ago, Li/Na carbonate (Li₂CO₃/Na₂CO₃) was developed as the electrolyte of molten carbonate fuel cells (MCFCs) in place of the usual Li/K carbonate (Li₂CO₃/K₂CO₃) to the advantage of a higher ionic conductivity and lower rate of cathode NiO dissolution. To estimate the potential of Li/Na carbonate as the MCFC electrolyte, the dependence of the cell performance on the operating conditions and the behavior during long-term performance was investigated in several bench-scale cell operations. The obtained data on the performance of Li/Na cells was analyzed to estimate the impact of voltage losses by using a performance model and discussed in comparison with the data of conventional Li/K cell performance.

Introduction

In molten carbonate fuel cell (MCFC) technology, the progress in terms of improving materials and manufacturing processes is a key to obtain superior cell performance and life. Although various carbonate compositions (the ternary mixtures of Li₂CO₃, Na₂CO₃ and K₂CO₃) were used as the MCFC electrolyte material in early development phases, from the 1950s to the mid-1970s, Li₂CO₃/K₂CO₃ eutectic has been used as the electrolyte in most developments since the mid-1970s [1], [2]. In Japan, scientists developing commercial MCFCs also adopted the Li/K carbonate electrolyte for several decades. However, since Yoshioka and Urushibata [3], [4] reported about cell performance using a Li/Na carbonate electrolyte an attempt has been made in Japan to change the electrolyte material from Li/K to Li/Na carbonate. Some groups [5], [6], [7], [8], [9], [10] also studied the potential of Li/Na carbonate in the early 1990s.

In this study, several Li/Na bench-scale cells were used to understand the dependence of cell performance on various operating conditions (pressure, temperature, current density, gas compositions) and the behavior during long-term performance. The obtained data on Li/Na cell performance is analyzed to estimate the impact of voltage losses (Nernst loss, Ohmic potential drop, anode and cathode polarization) by using a performance model and compared with the data of conventional Li/K cell performance. The aim is to characterize the Li/Na cell performance and contribute towards the design and operation of Li/Na stacks.

Section snippets

Experimental

The experimental data of the Li/Na cell performance was obtained by using eight bench-scale cells (No. 1−8). The experimental data of conventional Li/K cell performance to compare with that of Li/Na cell performance was obtained under a contract with NEDO and MCFC Research Association, or collaborative research agreement with CRIEPI and IHI. Table 1 shows the specifications of conventional Li/K cells and the examined Li/Na cells manufactured in IHI. The specifications of Li/K and Li/Na cells in

MCFC performance model description

Fig. 1 shows the performance curves of MCFC under the practical operational range in current density. A linear relationship between the current density and the output voltage is found in the experimental curve. Regarding the linear range, the following potential balance must be satisfied approximately in the cell: $V≅E−η_{ne} −(R_{ir} +R_{a} +R_{c})J$ where V is the output (uniform) voltage, E the equilibrium cell voltage (i.e. open circuit voltage), η_ne the Nernst loss, R_ir the internal resistance, R_a and R_c the

Cell performance under a 1.00 atm and 650 °C condition

Li/Na carbonate has the advantages of higher ionic conductivity, lower rate of cathode dissolution and lower electrolyte vapor loss than Li/K carbonate, whereas Li/Na carbonate has the disadvantage of lower oxygen gas solubility [1], [18]. In order to clarify the potential of the Li/Na carbonate as the MCFC electrolyte, the examinations of the Li/Na cell performance were carried out under the following for a MCFC bench-scale cell typical conditions: 1.00 atm pressure, 650 °C temperature, 150 mA/cm²

Conclusions

In view of the Li/Na bench-scale cell operations to understand the dependence of cell performance on various operating conditions and the behavior during long-term performance, the following conclusions have been obtained.

1.
Any examined Li/Na cell performance is superior in output voltage to the Li/K cell performance under a condition of 1.00 atm and 650 °C. The reason for the superior performance of the Li/Na cell is the lower internal resistance and the lower cathode reaction resistance of carbon

Acknowledgements

This work was carried out as a collaborative research agreement with Chubu Electric Power, CRIEPI and IHI. Some of the data used in this paper was quoted from the results of bench-scale cell operations under a contract with New Energy and Industrial Technology Development Organization (NEDO) and the MCFC Research Association (Technology Research Association for Molten Carbonate Fuel Cell Power Generation System). The authors appreciate the advice and support they received.

References (22)

K. Tanimoto et al.
Int. J. Hydrogen Energy
(1992)
P. Tomczyk et al.
J. Electroanal. Chem.
(1991)
L.K. Bieniasz
J. Electroanal. Chem.
(1991)
P. Tomczyk et al.
J. Electroanal. Chem.
(1991)
G. Mordarski
J. Electroanal. Chem.
(1991)
L.K. Bieniasz et al.
J. Electroanal. Chem.
(1993)
K. Yamada et al.
Electrochim. Acta
(1993)
K. Yamada et al.
Electrochim. Acta
(1995)
J.R. Selman, H.C. Maru, L.G. Marianowski, E. Ong, A. Pigeaud, V. Sampath, Advances in Molten Salt Chemistry, in: G....
J.R. Selman, Fuel Cell Systems, in: Leo J.M.J. Blomen, Michael N. Mugerwa (Eds.), Plenum Press, New York,...

S. Yoshioka et al.

Denki Kagaku (presently Electrochemistry)

(1996)

Cited by (135)

Model-based quantitative characterization of anode microstructure and its effect on the performance of molten carbonate fuel cell
2024, International Journal of Hydrogen Energy
This paper presents research on the impact of the material microstructure on the performance of Molten Carbonate Fuel Cells (MCFC). The study is motivated by the need to increase the operation time of MCFC stacks. As the MCFC stacks are mainly composed of porous materials, the paper shows the impact of the porosity on both fuel cell performance and degradation rate. The study is based on the mathematical model, validated through experiments with varying microstructure parameters, achieving an overall relative error of 8%. The study evaluated the performance of MCFC using anodes with different porosity and found that increasing anode porosity from 40% to 70% led to a nearly two-fold increase in maximum power density. However, from both the degradation test and polarization curves, the optimal level of porosity for the anode is around 55%. The porosity level at 55% ensures the highest catalytic surface of the electrodes and is a compromise between the mechanical properties of the electrode and its electrochemical properties.
Simulation and modeling of copper-chlorine cycle, molten carbonate fuel cell alongside a heat recovery system named regenerative steam cycle and electric heater with the incorporation of PID controller in MATLAB/SIMULINK
2022, International Journal of Hydrogen Energy
MCFC (molten carbonate fuel cell) is a relatively new kind of fuel cell that may be utilized in both local and large-scale energy distribution and generating systems. MCFCs are largely regarded as a viable source of renewable energy. Making an MCFC is a time-consuming and costly process. Mathematical modeling and efficiency simulations are essential to appropriately maximize its performance. Regenerative cycle, copper-chlorine cycle, and electric heater with PID controller is also studied to integrate them with MCFC to increase the efficiency of the overall system. Copper–Chlorine cycle is integrated to provide a stable stream of hydrogen and oxygen for the fuel cell. The Molten Carbonate fuel cell of stack 100 generates 1.203 MW of power at Voltage of 1.2 V each. Waste Heat recovery system is installed named regenerative Steam cycle which produces 2.94 MW of power. The total efficiency of system is 57% and the total extracted power is 4.143 MW. MATLAB/Simulink R2020a is used for modeling of multigeneration system with use of Engineering Equation Solver.
Influence of alkaline species on the high temperature lubrication of molten carbonate
2022, Tribology International
Citation Excerpt :
ILs have glass-transition temperatures or melting points below 100 °C, they are typically eutectic mixtures of an inorganic salt and organic salt or organic salts alone. Considered as a kind of ionic liquid, molten carbonate has attracted widespread attraction as solvents [4], catalysts [5] and electrolytes of molten carbonate fuel cell (MCFCs) [6,7] for power conversion technology because of its low cost, high efficiency and low impact on environment. Our recent work demonstrated that the molten sodium carbonate possesses promising lubrication performance at high temperature [8,9].
Ionic liquid with the melting points lower than 100 °C is a promising lubricant used ranging from automotive industry to aerospace application, to reduce the friction consumed energy loss and wear caused failure. This work investigated the high temperature lubrication effect of three different molten alkaline carbonate (high-temperature ionic liquid). The results suggest that the lubrication properties of the alkaline carbonate is alkaline species dependent, the carbonate of potassium shows a better lubrication than sodium and lithium carbonate from 730 to 825 °C. At 920 °C, the alkaline carbonate decomposes and reacts with iron oxide to form an alkali ferrite, the tribo-layer of the reactant shows promising anti-wear, and the Li₂Fe₃O₄ has a better lubricity than NaFeO₂ and KFeO₂. This study reports the concept of high-temperature ionic liquid lubricant, particularly on the roles of alkaline species. The high-temperature ionic liquid lubricant concept can potentially open up a new direction for the design and application of novel high temperature lubricants.
Coarsening mechanism of LiAlO<inf>2</inf> in acidic and basic molten carbonate salts
2021, Corrosion Science
Long-term corrosion behaviors of molten carbonate fuel cell (MCFC) electrolyte matrix with LiAlO₂ particle coarsening are evaluated in eutectic Li-Na carbonate melts with different pCO₂. In low pCO₂ (basic), the rapid growth of LiAlO₂ particles by Ostwald ripening is observed. TEM analysis verifies the continued process of dissolution and precipitation of LiAlO₂ nanocrystals that promotes LiAlO₂ crystal growth. It is revealed that this growth process is accompanied by α–γ phase transition through a Li₅AlO₄ intermediate phase. In high pCO₂ (acidic) conditions, oriented attachment, primarily between the (003) and (012) planes of α-LiAlO₂ crystals, leads to interparticle coalition and growth.
Lifetime expectancy of molten carbonate fuel cells: Part II. Cell life simulation using bench and coin-type cells
2021, International Journal of Hydrogen Energy
The lifetime of molten carbonate fuel cells is simulated in terms of electrolyte loss rate, voltage reduction rate, and activation energy using 7 cm² coin- and 100 cm² bench-type molten carbonate fuel cells. Arrhenius plots are used to determine the temperature dependence of the anode gas-phase mass transfer resistance, cathode gas and liquid-phase mass transfer resistances and electrolyte loss rate. The gas-phase mass transfer resistance of the anode has positive activation energy, indicating more substantial resistance at higher temperatures. The cathodic gas-phase mass transfer resistance has small and negative activation energy. In contrast, the cathode shows negative and positive activation energies at the mass transfer resistance of superoxide ion ( $O_{2}^{-})$ and CO₂ in the liquid electrolytes, respectively. The negative value indicates a lower overpotential at higher temperatures and vice versa. The Arrhenius plot of the electrolyte weight loss rate shows positive activation energy, indicating that an increase in temperature causes a simultaneous increase in electrolyte weight loss. The cell life of a molten carbonate fuel cell is predicted using a factor that relates the voltage reduction and electrolyte loss rates. A lower value of the factor gives a longer cell life.
The current status of high temperature electrochemistry-based CO<inf>2</inf> transport membranes and reactors for direct CO<inf>2</inf> capture and conversion
2021, Progress in Energy and Combustion Science
Citation Excerpt :
For CO2TMs, it has been adopted to improve the wettability of solid matrix with MC phase so that MC phase can be effectively retained within the solid porous structure. The ideal material of choice for surface modification is LiAlO2, which is known to fully wet MC with zero contact angle and the benchmark electrolyte matrix material for molten carbonate fuel cells (MCFCs) [137-141]. During the development of CO2TMs, it has also been used to coat the external surface of a solid porous matrix, such as in LSFCu-MC [54].
The concept of direct CO₂ capture and conversion has attracted significant interest from industries and academia in recent decades due to its potential to address the current grand challenge of global warming/climate change, rapid depletion of fossil fuels and realization of a future carbon neutral ecosystem. The incumbent benchmark technology for CO₂ capture is the post-combustion flue-gas “amine washing”, which is energy intensive and costly for large-scale commercial implementation. The CO₂ conversion technologies, on the other hand, are still at their infancy with many technical challenges to overcome, but primarily being explored in laboratory-scale, low-temperature, solution-based and high-temperature, solid-oxide-based electrochemical cells with renewable electricity perceived as the energy input. In this article, we provide a comprehensive overview on an emergent class of high-temperature electrochemical CO₂ transport membranes that can capture and convert CO₂ into valuable chemicals in single catalytic reactor fashion. The review starts with the chemistry and transport theory of three basic types of membranes purposely designed for different CO₂ feedstocks and downstream conversions. A range of key functional materials used in these membranes and their microstructural/electrochemical properties important to the CO₂ transport are then thoroughly discussed in conjunction with the effects of surface modifications and operating conditions. Several types of combined CO₂ capture and conversion catalytic reactors based on these membranes are also assessed with a focus on their working principles, system configurations and performance demonstrations. Finally, challenges and prospective of these electrochemical CO₂ transport membranes and their associated conversion reactors are candidly discussed for future development.

View all citing articles on Scopus

View full text

Performance analysis of molten carbonate fuel cell using a Li/Na electrolyte

Abstract

Introduction

Section snippets

Experimental

MCFC performance model description

Cell performance under a 1.00 atm and 650 °C condition

Conclusions

Acknowledgements

Int. J. Hydrogen Energy

J. Electroanal. Chem.

J. Electroanal. Chem.

J. Electroanal. Chem.

J. Electroanal. Chem.

J. Electroanal. Chem.

Electrochim. Acta

Electrochim. Acta

Denki Kagaku (presently Electrochemistry)