Cathode Activation Polarization Research Articles

Deciphering the Degradation Mechanism of High‐Rate and High‐Energy‐Density Lithium–Sulfur Pouch Cells

AbstractLithium–sulfur (Li–S) batteries are widely regarded as promising next‐generation battery systems due to their impressive theoretical energy density of 2600 Wh kg−1. However, practical high‐energy‐density Li–S pouch cells suffer from rapid performance degradation under high working rates. Herein, the performance degradation mechanism of 400 Wh kg−1 Li–S pouch cells is systematically investigated under a high cycling rate of 0.2 C. Focusing on the reduced specific capacity and increased cell polarization, the sluggish cathodic sulfur redox kinetics under lean‐electrolyte and high‐rate conditions is identified as the main limitation. Further polarization decoupling indicates the cathodic activation polarization contributes dominantly to the increased cell polarization. Accordingly, a delicately designed electrolyte using dimethyl diselenide as the kinetic promoter is proposed to enable the Li–S pouch cells to work at 0.2 C with reduced cell polarization. This work clarifies the sluggish cathodic interfacial charge transfer kinetics as the main challenge for high‐energy‐density Li–S batteries at high rates and is expected to inspire rational strategy design for achieving advanced Li–S batteries.

Micro-Tubular Solid Oxide Fuel Cell Polarization and Impedance Variation With Thin Porous Samarium-Doped Ceria and Gadolinium-Doped Ceria Buffer Layer Thickness

Abstract Porous buffer layers for anode-supported solid oxide fuel cells (SOFCs) have been investigated for many years with different thicknesses of the buffer layer in each study. In this work, micro-tubular SOFCs having samarium-doped ceria (SDC) and gadolinium-doped ceria (GDC) buffer layers are compared using the current–voltage technique, electrochemical impedance spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The thickness of the porous SDC and GDC buffer layer is investigated systematically with the thickness varying between 0.3 and 2.0 μm. The power density varies between 212 and 1004 mW/cm2 for samples having different SDC buffer layer thickness. Comparable changes occur for the SOFCs with a GDC buffer layer, but less variation in polarization losses resulted. Variation in electrochemical performance varies due to changes in ohmic resistance, cathode activation polarization, and interfacial reactions between the cathode and electrolyte materials.

Modeling investigation of Sm0.5Sr0.5CoO3−δ–Ce0.8Sm0.2O2−δ cathode for proton-conducting ceramic fuel cell

Simulation of proton ceramic fuel cell is of great importance in understanding their working mechanisms. Cathode activation polarization is a critical concern in the simulation. In this paper, Sm0.5Sr0.5CoO3−δ–Ce0.8Sm0.2O2−δ cathode is selected as studied case. The effective reaction order, which is the exponential of the oxygen partial pressure in cathode Butler-Volmer equation, is determined via our model. The dominant process in cathode reaction is investigated and identified. Among the involved reaction steps, model result points out that the surface diffusion of absorbed oxygen ion is dominant, which is in accord with the report. Moreover, single button cells with BaCe0.7Zr0.1Y0.2O3−δ electrolyte and Sm0.5Sr0.5CoO3−δ–Ce0.8Sm0.2O2−δ cathode are prepared, and the measured cell output voltages are compared with the simulated ones. The predicted cell outputs via our full cell simulation match the measurements under diverse experimental settings, suggesting that the method and parameters in our simulation are applicable. Our models facilitate both the analysis of experimental results and the development of proton-conducting solid oxide fuel cell model.

Performance evaluation of SOEC for CO2/H2O co-electrolysis: Considering the effect of cathode thickness

Solid oxide electrolysis cells (SOECs) provide a great opportunity to stabilize carbon dioxide (CO2) emissions by converting CO2/H2O into synthetic fuels with high energy conversion efficiency. Nevertheless, the performance of state-of-the-art Ni-cermet supported SOEC is limited by the interfacial polarization resistance. This study presents a simple approach to minimize the cathodic polarization resistances by reducing its thickness. The effect of cathode thickness on the electrochemical performance of SOECs for CO2/H2O co-electrolysis are investigated at 750–850 °C for variable reactant gas composition. Electrochemical measurements like current density-voltage (i-V) curves and electrochemical impedance spectroscopy (EIS) are performed to characterize the performances of the cells. Impedance spectra are recorded under open circuit voltage (OCV) and polarization (1.4 V) to deeply study the influence of cathode thickness on polarization loss processes. The EIS results confirm that when reducing the cathode thickness, the cathode activation polarization is slightly decreased, whereas, the concentration polarization is significantly reduced, improving the reactant gas diffusion and the performance of SOEC. A similar effect is observed by increasing the CO2 mole fraction in the feed. Furthermore, the variation of cathode thickness and gas composition greatly affected the cell performance at high temperature, due to large reactants utilization. The results reveal that SOEC performance for co-electrolysis of CO2/H2O could considerably be improved by reducing the cathode thickness and improving the transport processes within the fuel-electrode. These results aid the optimization of cell design to improve the gaseous transport to the electrode/electrolyte interface and enhance the performance of SOEC for CO2/H2O reduction.

Three dimensional modeling of a FE-DMFC short-stack

One of the primary challenges in fuel cell stack models is the lack of numerical methods and computational resources available to handle full-scale stack geometry to at least the same grid resolution and detailed physics as could be obtained in an equivalently detailed single cell model. To help resolve this challenge, a 3D modeling approach is proposed, and applied to a 3-cell Flowing Electrolyte-Direct Methanol Fuel Cell short-stack. In this approach, the flow fields, backing layers and membranes are solved numerically in a 3D manner, whereas the electrochemical performance is solved analytically. This approach allowed for the detailed physics to be incorporated into the model without the requirement of a high mesh density within the MEA, thus softening the computational load. The methanol concentration distributions at the anode catalyst layer of each cell for different methanol concentrations and sulfuric acid flow rates were found. In addition, the changes of crossover current density and cathodic activation polarization with current density were assessed. The model was used to shed light onto the mechanisms that lead to non-uniform flow behavior within the stack's cells; help identify methods to maintain a uniform flow and concentration distribution within the stack; and to provide methods to minimize methanol crossover to the cathode. The results showed that among the studied parameters, taking the methanol concentration as 2000 mol/m3 and sulfuric acid flow rate as 10 mL/min, cathodic activation polarization takes its lowest value.

Numerical investigations to determine the optimal operating conditions for 1 kW-class flat-tubular solid oxide fuel cell stack

In this study, a detailed three-dimensional numerical model is developed which simultaneously assimilates the transport processes, the electrochemical and chemical reactions to optimize the performance of 1 kW-class flat-tubular solid oxide fuel cell stack while operating on H2 and pre-reformed methane fuels. The unique feature of this CFD (computational fluid dynamic) model is that it encompasses the electrochemical oxidation of H2 and CO as well as internal steam reforming reactions including radiation heat transfer analysis in the full stack. A CFD model validated with the experiments performed in-house is utilized to explore the optimal operating conditions by investigating the effect of pre-reforming rate, air/fuel inlet temperatures, oxidant utilizations and radiative heat transfer effect on the temperature distributions. The numerical results elucidated that temperature and the current density distributions can be regulated by adjusting the methane conversion in the pre-reformer. It is also observed that neglecting the CO electro-oxidation in the modeling can underestimate the stack performance; whereas increasing the inlet temperature increases the stack performance. The oxidant utilization analysis established that higher oxidant utilization adversely affects the stack performance due to higher cathodic activation polarization losses. Radiation heat transfer analysis demonstrates that it curtails peak temperature and minimizes temperature gradients of the stack components.

Polarization modeling and performance optimization of a molten sodium hydroxide direct carbon fuel cell (MHDCFC)

An electrochemical model for a molten sodium hydroxide direct carbon fuel cell (MHDCFC) is developed based on electrochemical reaction dynamics, mass transfer, and electrode processes in the cell. Activated carbon and graphite are considered the main fuels, and static and dynamic parameters describing polarizations are taken into account for valuation and optimization of cell performance. Asymmetric reaction compartments are used in the MHDCFC, and the effect of the anodic compartment height on polarization is described first. The cell performance mainly depends on temperature (T), the pressures in the anodic (Pan) and cathodic compartments (Pcat), the anodic compartment height (H1), and the fuel type. Besides, cell performance is affected by ohmic polarization, anode activation polarization, cathode concentration polarization, and cathode activation polarization, in order of precedence. At Pan of 1.8 atm, Pcat of 1.7 atm, H1 of 0.06 m, and T of 773–973 K, the efficiencies (e) of the cells with activated carbon and graphite are higher than 50% at current densities of 0–500 A m−2 and 0–700 A m−2, respectively. The maximum power densities (e > 50%) are achieved for activated carbon and graphite and reach 367.6626 W m−2 and 498.9687 W m−2, respectively.

Polarization distribution and theoretical fitting of direct methanol fuel cell

Membrane Electrode Assembly (MEA) is a key component of direct methanol fuel cell. In order to improve the power generation performance of the MEA, it is necessary to reduce polarization losses. The cathode and anode activation polarization, proton exchange membrane ohmic polarization and gas diffusion layer mass transfer polarization were studied under different methanol concentration and operation temperature conditions respectively. A theoretical study of the various polarization fitting and distribution losses was conducted. The polarization distribution results indicated that the activation polarization of cathode and anode are the main over potential contribution and accounted for more than 80%. The ohmic resistance accounted for approximately 10%. By studying the distribution of polarization loss, we got a variety of distribution of polarization losses under different operating conditions, these results provide a theoretical basis for efficient ways to optimize the MEA.

A Simple Pressurized SOFC Test Rig for Measurements of Cell Performance, Impedance, and Various Overvoltages

Nowadays, our modern society is facing many serious environmental and energy shortage problems. Delay of action will jeopardize the ability of future generations to meet their needs. Thus, how to develop highly efficient power generation systems with very low emissions is an urgent need for our modern society. Probably, a pressurized solid oxide fuel cells (PSOFC) integrating with a gas turbine (GT) or micro gas turbine (MGT), the hybrid PSOFC-GT or -MGT power system, which has the highest efficiency up to 70%, is the best candidate. The development of such hybrid power system helps to the consolidation of the fuel cell industry, the expansion of the gas turbine industry, and the improvement of the environment. As such, the hybrid PSOFC-MGT power system has become an emerging topic in the 21th century with wide interest, as evidenced by a large volume of literature and several demonstration projects. For examples, Siemens demonstrated a 220 kW PSOFC-MGT hybrid system in 2002, the Korea Institute of Energy Research displayed a 30 kW (5 kW PSOFC integrated with 25 kW MGT) hybrid system in 2006, and Mitsubishi Heavy Industries run a 200 kW hybrid PSOFC-MGT combined-cycle power plant in 2011. Indeed, considerable progresses have been made over the past two decades in optimization of geometry and development of new materials and in understanding of mass and heat transports together with electrochemical reactions in porous microstructures. However, there are still technical challenges remaining to be solved step by step with limited but controllable parameters before a stable operation among different components of the hybrid PSOFC-MGT system can be assured and the status of the development can be then elevated from a module level. One of the challenges is the detail electrochemical impedance spectra (EIS) of PSOFC, which is still rare in literatures. This motivates us to design a simple efficient high-pressure full/half button cell testing platform for measurements of the effect of pressurization and increasing temperature on EIS and various overvoltages of PSOFC. The testing platform has several parts, from inside out including a specially thread-designed housing carrier for the full/half button cell, a serpentine heating pipe system for uniform heating of the supplied fuel and air gases, a temperature-controlled furnace, and a large high-pressure vessel together with measuring devices and their associates. Hence, current-voltage curves and AC impedance spectra of any full/half button cells can be measured. In this study, we present power-generating characteristics and EIS data of an anode-supported full button cell over wide ranges of pressure (p = 1~5 atm) and temperature (T = 700~850 oC). We apply constant gas flow rates, 200ml min-1 H2 in anode and 200ml min-1 air in cathode, for all experimental events. Results show that, for any given values of T or p, power densities increase with increasing p or T at any fixed current densities. Such enhancement on power densities is more sensitive to the increase of T than to the increase of p. These results are explained by the corresponding EIS data. The latter shows that both high and low frequency arcs of impedance spectra decrease with increasing p, resulting in a reduction of the total polarization resistance. Specifically, the high frequency arcs decrease rather weakly with increasing p as compared to that of the low frequency arcs. Further, we found that the characteristic frequencies of high and low frequency arcs occur around 100 ~ 1000 Hz and at about 10 Hz, respectively. The former may be attributed to the cathode activation polarization and the latter may be due to the diffusion processes in the anode electrode. Hence, pressurization can simultaneously decrease the cathode activation polarization and the anodic diffusion concentration polarization. In addition to the aforesaid power-generating characteristics and EIS results, this study reports analyses of activation and concentration overvoltages using the Butler-Volmer equation and the related concentration overvoltage equation based on a 1D diffusion model. We found that both activation and concentration overvoltages decrease with increasing p. Two important parameters, the exchange current density and the anodic effective diffusion coefficient, are also calculated by applying the present measured data. Results show that pressurization enhances the exchange current density leading to an increase of the electrochemical reaction rate. Though pressurization reduces slightly the anodic effective diffusion coefficient, it can increase the molar concentration and thus the overall gas-phase diffusion rate in porous electrode. These overvoltage results will be compared with previous numerical and experimental data to enhance our understanding of the effect of pressurization on the polarization mechanisms in SOFCs. Figure 1

Simulation of a fluidized bed electrode direct carbon fuel cell

In order to deeply understand the characteristics of fluidized bed electrode direct carbon fuel cell (FBEDCFC), a mathematical model based on thermodynamics, electrochemical reaction dynamics, mass transfer theory and electrode processes is established and discussed. Polarization losses for the FBEDCFC are examined using Li2CO3/K2CO3 eutectic melt with the molar ratio of 62:38 as the electrolyte and activated carbon impregnated by HNO3 as the fuel. The results indicate that the anode activation polarization and the cathode activation polarization both decrease with the reaction temperature, while the decrement in the former is more evident than the latter. The ohmic polarization decreases with the reaction temperature but increases with the gas flow rate. In contrast to other polarizations, the concentration polarization is extremely small. Calculation results of the model well agree with experimental results under low current density. The peak power density of the FBEDCFC is 314.2 W m−2 with the reaction temperature of 923 K and the gas flow rate of 0.0709 m s−1. With the current density of 400 A m−2, the overall efficiency of the FBEDCFC is as high as 54.36% at 923 K.

Concepts for Ultra-High Power Density Solid Oxide Fuel Cells (SOFC)

Over the past two decades, considerable work has been reported on solid oxide fuel cells (SOFC) [1-3]. While progress has been made, there has not been significant further gain in performance (at 800oC), beyond that achieved about fifteen years ago (~2 Wcm-2), despite using many different cathodes. Thus in many cases, the cathode may not be limiting the performance. To achieve further improvements in cell performance beyond what has been discussed in previous studies [4,5], it will require accurate identification of various polarization losses, their sources, and dependence on material and microstructural parameters, atmosphere and temperature. The majority of the modeling studies do not provide the required guidance as they rely on a number of often not so easily measurable parameters thus necessitating a somewhat arbitrary selection of such parameters. The objective of this work is to estimate various polarization losses based on out-of-cell measurements made using micro-fabricated electrodes, microstructural measurements on cells, and cell electrochemical performance measurements using a parametric model. Such an approach may identify where the dominant losses are and how to further improve cell performance. The minimum number of independent parameters necessary to model cell performance for an anode-supported SOFC with five distinct layers are 9 and they are: Deff1 O2-N2 and Deff2 O2-N2 , the effective binary diffusivities through the cathode current collector and the cathode functional layer, respectively; Deff1 H2-H2Oand Deff2 H2-H2O , the effective binary diffusivities through the anode support and the anode functional layer, respectively; cathode exchange current density (i0c ); anode exchange current density ((i0a ), cathode transfer coefficient (αc), anode transfer coefficient (αa), and ohmic resistance Ri. The parametric model is given by equation (1). V(i)=E0-iRi-(RT/2F)arcsinh(i/2i0 c)-(RT/2F)arcsinh(i/2i0 a)+( RT/2F)ln(pH2'(i)pH2Oo /( pH2o pH2O')+ ( RT/4F)ln(pO2'(i)/ pO2o ) (1) where pO2o and pO2'(i) are the oxygen partial pressures just outside the cathode current collector and close to the cathode functional layer/electrolyte interface, respectively; pH2o and pH2'(i) are the hydrogen partial pressures in the fuel just outside the anode support and close to the anode functional layer/electrolyte interface, respectively; pH2Oo and pH2O' are the water vapor partial pressures in the fuel just outside the anode and close to the anode functional layer/electrolyte interface, respectively. In equation (1), both transfer coefficients are assumed to be 0.5. As seen in Fig. 1, at low current density, the most dominant contribution is cathodic activation polarization for a cathode grain size of 2 mm. However, beyond about 1.3 A/cm2, the ohmic contribution is the dominant one, and underscores its importance. In Figs. 2a to 2b, the cathode functional layer grain size is varied from 2 μm to 0.2 μm. This increases the maximum power density by 0.3 W/cm2. However, if the ohmic resistance can be somehow reduced from 0.1 to 0.05 Ωcm2, the maximum power density increases by 1.2 W/cm2 (Figs. 2b and 2c) even in a thin electrolyte, anode-supported cell. This shows the profound role of ohmic contribution on cell performance. By contrast, a change from LSM/YSZ to Pt/YSZ only leads to a modest increase in maximum power density of about 0.4 W/cm2 (Figs. 2c and 2d). This is consistent with the observation that cells with several very different cathodes exhibit similar performance. Further work is thus required in lowering the ohmic contribution. Many cathodes that have been developed over the years appear quite satisfactory and not limiting cell performance for operation at 800oC. Funded by DOE EFRC Grant Number DE-SC0001061 as a flow-through from the University of South Carolina.

Electrochemical Performance and Stability of the Cathode for Solid Oxide Fuel Cells: I. Cross Validation of Polarization Measurements by Impedance Spectroscopy and Current-Potential Sweep

The aim of this paper is to address three issues in solid oxide fuel cells (SOFC): (i) cross-validation of the polarization of a single cell measured using both dc and ac approaches, (ii) the precise determination of the total area specific resistance (ASR), and (iii) understanding cathode polarization with cathodes. The ASR of an SOFC is a dynamic property, meaning it changes with current density. The ASR measured using impedance spectroscopy (low frequency interception with the real -axis of the ac impedance spectrum) matches that measured from a dc current–voltage sweep (the tangent of a dc curve). Due to the dynamic nature of ASR, we found that an impedance spectrum measured under open-circuit voltage or on a half-cell may not represent the cathode performance under real operating conditions, particularly at a high current density. In this work, the electrode polarization was governed by the cathode activation polarization; the anode contribution was negligible.

SOFC Modeling and Parameter Identification by Means of Impedance Spectroscopy

A zero-dimensional stationary model for the I-U characteristics of anode-supported solid oxide fuel cells (SOFC) is presented. The different kinds of electrode polarization resistances are separated from experimental impedance data by means of a detailed equivalent circuit model specified for anode-supported cells. This has the big advantage that partial pressure and temperature dependency of electrode exchange current densities could be determined by a fit of semi-empirical power law model equations. For the first time, the exponents a and b for the pH2- and pH2O-dependency of the anodic exchange current density are obtained independently. Equally, the exponent m for the pO2-dependency of the cathodic exchange current density is derived. The anodic and cathodic gas diffusion polarization is calculated without the estimation of parameters such as tortuosity and porosity. Our approach is advantageous to separate anodic and cathodic activation and diffusion polarization and precisely predicts I-U characteristics for a wide operating range.

Analysis of polymer electrolyte fuel cell performance by electrode polarization model

Abstract For development of polymer electrolyte fuel cell (PEFC) lifetime estimation method, a high accuracy PEFC electrode polarization model is required. An electrode polarization model which was previously proposed was verified. However, accuracy of the electrode polarization model was not enough to estimate PEFC performance under various conditions. A new high accuracy PEFC electrode polarization model has been developed based on electrochemical consideration and data observed at elevated pressures. In the cathode polarization model, effects of O 2 diffusion and H 2 O plugging have to be considered to obtain high accuracy for long-term operation. In addition, PEFC performance degradation was analyzed by the electrode polarization model. Main factors of PEFC performance degradation are OCV drop, the cathodic activation polarization, voltage drops by O 2 diffusion and H 2 O plugging.

Performances and Degradation Phenomena of Solid Oxide Anode Supported Cells With LSM and LSCF Cathodes: An Experimental Assessment

The performance of solid oxide fuel cells is affected by various polarization losses, usually grouped in Ohmic, activation, and concentration polarizations. Under typical operating conditions, these polarization losses are largely dependent on cell materials, electrode microstructures, and cell geometry: as an example, the performance of a tubular cell is strongly limited by the Ohmic polarization due to the long current path of electrons, while in a planar cell each of these losses has a comparable effect. It is therefore of interest, in the case of planar geometry, to investigate the main performance limiting factors. In this paper, a performance evaluation of planar circular-shaped seal-less SOFC cells was performed. Two different designs of planar cells are considered. Both have a porous NiO-YSZ (yttria stabilized zirconia) anode as mechanical support, a NiO-YSZ anode active layer, and an YSZ electrolyte, and they only differ in the cathode design: (1) strontium doped lanthanum manganate (LSM)-YSZ cathode functional layer and LSM cathode current collector layer; (2) yttria doped ceria blocking layer and lanthanum strontium cobalt ferrite oxide (LSCF) functional layer. The characterization was performed by taking V-I measurements over a range of temperatures between 650°C and 840°C with hydrogen as fuel and air as oxidant. The experimental data analysis consisted in the analysis of some typical performance indicators (maximum power density (MPD); current density at 0.7V). The dependence of the cell performance on the various polarization contributions was rationalized on the basis of an analytical model—through a parameter estimation of the experimental data—devoted to the determination of the main polarization losses. Based on the results of the investigation, it is concluded that LSCF cathodes are really effective in decreasing the cathode activation polarization, allowing the reduction in operating temperature.

Effect of Anode Active Layer on Performance of Single-Step Cofired Solid Oxide Fuel Cells

Anode-supported planar solid oxide fuel cells (SOFCs) with and without the anode active layer were fabricated by a single-step cofiring process. The cells were comprised of a porous -stabilized zirconia (YSZ) anode support, a porous fine-grained anode active layer for some experiments, a dense YSZ electrolyte, a porous fine-grained Ca-doped cathode active layer, and a porous LCM cathode current collector layer. The fabrication process involved tape casting of the anode support followed by screen printing of the remaining component layers. The cells were then cofired at for . Sintered cells were electrochemically tested between 700 and with air as oxidant and various compositions of humidified hydrogen as fuel to simulate the effect of fuel utilization on cell performance. Experimentally measured current density-voltage () characteristics of the cells were fitted into a polarization model, and the cell parameters, including the area-specific ohmic resistance, exchange current density, anodic limiting current density, cathodic limiting current density, effective binary diffusivity of hydrogen and water vapor in the anode, and that of oxygen and nitrogen in the cathode, were obtained. Evaluation of the electrochemical performance and the polarization modeling results indicated that the cell performance is dominated by the cathodic activation polarization at low fuel utilization condition. However, the cell performance loss due to the anodic activation polarization increases as the fuel utilization increases. The anode active layer significantly improves the cell performance at high fuel utilization by lowering the anodic activation polarization under -rich fuel because the anode active layer has finer and less porous microstructures and increases the number of the reaction sites near the anode-electrolyte interface. Cell performance at high fuel utilization and the effect of the anode active layer on the cell performance were discussed in detail.

Experimental investigations of the microscopic features and polarization limiting factors of planar SOFCs with LSM and LSCF cathodes

The paper deals with the microscopic and polarization evaluation of planar circular-shaped seal-less SOFC cells from InDEC ® with an outline of performance limiting factors at reduced temperature. The cells consist of porous NiO–YSZ anode as mechanical support, NiO–YSZ anode active layer, yttria-stabilized zirconia (YSZ) electrolyte, and only differ for the cathode design. A first design (ASC1) with strontium doped lanthanum manganate LSM–YSZ cathode functional layer (CFL) and LSM cathode current collector layer (CCCL); the second design (ASC2) with yttria doped ceria (YDC) barrier layer and lanthanum strontium cobalt ferrite oxide (LSCF) cathode. The microscopic analysis was performed using SEM methods. The electrical characterization was performed by taking current–voltage measurements over a range of temperatures between 650 and 840 °C with hydrogen as fuel, and air as oxidant. The analysis of performance showed that at 740 °C the voltage of 700 mV is reached at around a double value of current density in the case of ASC2. Further, the dependence of performance on the various polarization contributions was rationalized on the basis of an analytical model. Through a parameter estimation on the experimental data, it was possible to determine some polarization parameters for the two cells such as the effective exchange current densities, ohmic resistance and anodic limiting current density. It is shown that the performance limitation at low temperature is due to activation polarization for ASC1 and ohmic polarization for ASC2. Based on the results of the investigation, it is concluded that LSCF cathodes are really effective for decreasing the cathode activation polarization, allowing the reduction of operating temperature.