Development and Characterisation of Cathode Materials for the Molten Carbonate Fuel Cell

Among the obstacles for the commercialization of the MoltenCarbonate Fuel Cell (MCFC), the dissolution of thestate-of-the-art lithiated NiO cathode is considered as aprimary lifetime limiting constraint. Development ofalternative cathode materials is considered as a main strategyfor solving the cathode dissolution problem. LiFeO2and LiCoO2had earlier been reported as the most promisingalternative materials; however, they could not satisfactorilysubstitute the lithiated NiO. On the other hand, ternarycompositions of LiFeO2, LiCoO2and NiO are expected to combine some desirableproperties of each component. The aim of this work was todevelop alternative cathode materials for MCFC in the LiFeO2-LiCoO2-NiO ternary system. It was carried out byinvestigating electronic conductivity of the materials, firstin the form of bulk pellets and then in ex-situ sinteredporous-gas-diffusion cathodes, and evaluating theirelectrochemical performance by short-time laboratory-scale celloperations. Materials in the LiFeO2-NiO binary system and five ternary sub-systems,each with a constant molar ratio of LiFeO2:NiO while varying LiCoO2content, were studied. Powders withcharacteristics appropriate for MCFC cathode fabrication couldbe obtained by the Pechini method. The particle size of LiFeO2-LiCoO2-NiO powders considerably depends on thecalcination temperature and the material composition. Theelectrical conductivity study reveals the ability of preparingLiFeO2-LiCoO2-NiO materials with adequate electricalconductivity for MCFC cathode application. A bimodal pore structure, appropriate for the MCFC cathode,could be achieved in sintered cathodes prepared usingporeformers and sub-micron size powder. Further, this studyindicates the nature of the compromise to be made between theelectrical conductivity, phase purity, pore structure andporosity in optimization of cathodes for MCFC application. Cellperformance comparable to that expected for the cathode in acommercial MCFC could be achieved with cathodes prepared from20 mole% LiFeO2- 20 mole% LiCoO2- 60 mole% NiO ternary composition. It shows aniR-corrected polarization of 62 mV and a iR-drop of 46 mV at acurrent density of 160 mAcm-2at 650 °C. Altogether, this study revealsthe possibility of preparing LiFeO2-LiCoO2-NiO cathode materials suitable for MCFCapplication. Keywords: molten carbonate fuel cell (MCFC), MCFC cathode,LiFeO2-LiCoO2-NiO ternary compositions, electrical conductivity,porous gas diffusion electrodes, polarization, electrochemicalperformance, post-cell characterization

Development and Characterisation of Cathode Materials for the Molten Carbonate Fuel Cell

Among the obstacles for the commercialization of the MoltenCarbonate Fuel Cell (MCFC), the dissolution of thestate-of-the-art lithiated NiO cathode is considered as aprimary lifetime limiting constraint. Development ofalternative cathode materials is considered as a main strategyfor solving the cathode dissolution problem. LiFeO2and LiCoO2had earlier been reported as the most promisingalternative materials; however, they could not satisfactorilysubstitute the lithiated NiO. On the other hand, ternarycompositions of LiFeO2, LiCoO2and NiO are expected to combine some desirableproperties of each component. The aim of this work was todevelop alternative cathode materials for MCFC in the LiFeO2-LiCoO2-NiO ternary system. It was carried out byinvestigating electronic conductivity of the materials, firstin the form of bulk pellets and then in ex-situ sinteredporous-gas-diffusion cathodes, and evaluating theirelectrochemical performance by short-time laboratory-scale celloperations. Materials in the LiFeO2-NiO binary system and five ternary sub-systems,each with a constant molar ratio of LiFeO2:NiO while varying LiCoO2content, were studied. Powders withcharacteristics appropriate for MCFC cathode fabrication couldbe obtained by the Pechini method. The particle size of LiFeO2-LiCoO2-NiO powders considerably depends on thecalcination temperature and the material composition. Theelectrical conductivity study reveals the ability of preparingLiFeO2-LiCoO2-NiO materials with adequate electricalconductivity for MCFC cathode application. A bimodal pore structure, appropriate for the MCFC cathode,could be achieved in sintered cathodes prepared usingporeformers and sub-micron size powder. Further, this studyindicates the nature of the compromise to be made between theelectrical conductivity, phase purity, pore structure andporosity in optimization of cathodes for MCFC application. Cellperformance comparable to that expected for the cathode in acommercial MCFC could be achieved with cathodes prepared from20 mole% LiFeO2- 20 mole% LiCoO2- 60 mole% NiO ternary composition. It shows aniR-corrected polarization of 62 mV and a iR-drop of 46 mV at acurrent density of 160 mAcm-2at 650 °C. Altogether, this study revealsthe possibility of preparing LiFeO2-LiCoO2-NiO cathode materials suitable for MCFCapplication. Keywords: molten carbonate fuel cell (MCFC), MCFC cathode,LiFeO2-LiCoO2-NiO ternary compositions, electrical conductivity,porous gas diffusion electrodes, polarization, electrochemicalperformance, post-cell characterization

Investigation of MgTiO3 as an anode material for rechargeable Li-ion batteries

Magnesium Titanate (MgTiO3) is a common and commercially available dielectric material used in electronics applications. The potential of using MgTiO3 as an anode material in rechargeable Li-ion batteries has been investigated under this study. MgTiO3 particles were synthesized by both wet-chemical Pechini method and solid state ball milling method. The subsequent material characterizations were carried out using X-ray diffraction and scanning electron microscopic techniques. The electrochemical performance of MgTiO3 as an anode material in Li-ion rechargeable battery was carried out with Li metal electrode in coin half cells. For wet-chemically synthesized MgTiO3, the potentials associated with lithiation were 1.14 V and 0.76 V vs Li/Li+ with an initial discharge capacity of 103 mAh/g at C/10 rate. Lithiation potential for ball milled MgTiO3 was found to be at 1.3 V vs Li/Li+ with an initial discharge of 63 mAh/g cycled at C/10 rate

Synthesis of Li (Ni_1/3Mn_1/3Co_1/3) O₂ by Glycine Nitrate combustion process

Glycine Nitrate Combustion (GNC) method was successfully employed for the synthesis of Li(Ni1/3Mn1/3Co1/3)O2 with powder characteristics appropriate for the cathode of rechargeable  Li-ion batteries (LIBs). The outcome of this study proposed an optimum value of 0.6 for the Glycine: Nitrate ratio to obtain phase pure, well crystalline and rather spherical shaped Li(Ni1/3Mn1/3Co1/3)O2 micron size secondary particles by the GNC process. These secondary particles were composed of softly agglomerated primary particles of 200 - 300 nm in size. This particle morphology is regarded as a highly favorable for the functioning as a cathode in LIB. The electrical conductivity of Li (Ni1/3Mn1/3Co1/3) O2, determined by the dc four-probe technique, revealed the semiconducting nature with conductivity of the order of 10-7 S cm-1, at  25 °C. Lithium ion half-cell constructed with this prepared cathode material showed initial discharge capacity of 187 mAhg-1 with irreversible capacity of 25 mAhg-1 at C/5 rate with a cut-off voltage of 2.5 - 4.6 V, at 25 °C. This performance can be attributed to the highly favorable particle morphology obtained by the successful use of GNC process for the powder synthesis

Synthesis of Li(Ni1/3Mn1/3Co1/3-xBax)O-2 cathode materials for lithium-ion rechargeable battery by glycine-nitrate combustion process

This study was based on developing Li(Ni1/3Mn1/3Co1/3-xBax)O-2 (x=0.04, 0.08, 0.11, 0.22, and 0.33) materials by substituting expensive Co with Ba, for the use in the cathode of rechargeable lithium-ion batteries (LIBs). Glycine-nitrate combustion method, which is a low-cost combustion technique, was employed to synthesize spherical shaped micron size secondary particles formed by densely agglomerated primary particles. The phase analysis performed by the X-ray diffractometry revealed the formation of the required layered phase of R-3m structure with trace amounts of a secondary phase. Furthermore, these Ba-substituted novel materials showed considerably higher electrical conductivity than those of the Li(Ni1/3Co1/3Mn1/3)O-2 base material. In the cell performance studies, the Ba-substituted cathode materials synthesized in this study showed slightly lower initial discharge capacity of 162.4mAhg(-1) but with considerably improved cycle performance compared to those of the Li(Ni1/3Co1/3Mn1/3)O-2 base material (187.7mAhg(-1)). More importantly, the Li(Ni1/3Mn1/3Co1/3-xBax)O-2, x=0.04 material clearly showed its ability to eliminate and prevent structural transformation usually associated with excess Li extraction at potentials above 4.5V. Therefore, the Li(Ni1/3Mn1/3Co1/3-xBax)O-2, x=0.04 material can be proposed as a potential candidate for the high-voltage cathode application of LIB

Performance of developed natural vein graphite as the anode material of rechargeable lithium ion batteries

Electrochemical performance of natural vein graphite as an anode material for the rechargeable Li-ion battery (LIB) was investigated in this study. Natural graphite exhibits many favorable characteristics such as, high reversible capacity, appropriate potential profile, and comparatively low cost, to be an anode material for the LIB. Among the natural graphite varieties, the vein graphite typically possesses very high crystallinity together with extensively high natural purity, which in turn reduces the cost for purification. The developed natural vein graphite variety used for this study, possessed extra high purity with modified surface characteristics. Half-cell testing was carried out using CR 2032 coin cells with natural vein graphite as the active material and 1 M LiPF6 (EC: DMC; vol. 1:1) as the electrolyte. Galvanostatic charge–discharge, cyclic voltammetry, and impedance analysis revealed a high and stable reversible capacity of 378 mA h g−1, which is higher than the theoretical capacity (372 mA h g−1 for LiC6). Further, the observed low irreversible capacity acquiesces to the high columbic efficiency of over 99.9%. Therefore, this highly crystalline developed natural vein graphite can be presented as a readily usable low-cost anode material for Li-ion rechargeable batteries