Ermete Antolini

Formation of ternary lithium oxide–nickel oxide–magnesium oxide solid solution from the Li/Ni/MgO system

Abstract The effect of the thermal treatment at 1000°C in air of Li/Ni/MgO system was investigated by X-ray diffraction (XRD) analysis. During air calcinations of Li/Ni/MgO system, the formation of a ternary Li y Ni x Mg 1− y − x O solid solution takes place. The presence of Ni 3+ ions, as charge-compensating species, allows the incorporation of a high amount of Li + ions into MgO lattice without the formation of oxygen vacancies.

Effect of lithium carbonate on the densification of LixNi1−xO solid solutions at temperatures up to 900°C

Abstract Li x Ni 1− x O solid solutions are of interest as cathodes for molten carbonate fuel cells. Specimen (plaque) diameter changes (PDC) and density changes of Ni Li 2 CO 3 composites following heat treatment were determined as a function of starting composition and sintering temperature so as to determine the densification mechanism. For temperatures above 700°C the mixtures containing more than 12 mol% of Li + showed a decrease in PDC and an increase in density with increase in temperature. The behavior of high-lithium-content mixtures is attributed to the presence of a reactive liquid phase of undecomposed lithium carbonate at temperatures > 723°C, which promotes sintering.

Formation of LixNi1−xO solid solution from NiLi2CO3 mixtures

Abstract The formation of Li x Ni 1− x O solid solution from Ni Li 2 CO 3 mixtures is reported. Lithium loss by evaporation of both unreacted and NiO-dissolved lithium oxide was revealed, depending on temperature, time and nominal lithium content of the samples.

A new way of obtaining LixNi1−xO cathodes for molten-carbonate fuel cells

Abstract An unsintered nickel plaque containing Li 2 CO 3 and an organic binder were tested as a cathode in a molten-carbonate fuel cell. Organic burnout, nickel oxidation,lithium carbonate decomposition and Li x Ni 1− x O solid-solution formation occurred during the start-up of the cell. The in-cell test showed good performance after a short time of operation, and a limited performance decay after 3500 h.

Thermal treatment of Co/Li2CO3 mixtures at 1200 °C

Abstract The phase evolution and the sintering process of Co/Li2CO3 mixtures following thermal treatment at 1200 °C in air were evaluated. In the dynamic step of the thermal treatment, Co3O4 and LiCoO2 were obtained and the densification and grain size of lithiated samples were higher than those of pure Co. In the isothermal step at 1200 °C, decomposition of LiCoO2 and diffusion of lithium ions into CoO with formation of LixCo1 − xO solid solution were denoted, and after 40 h of isothermal treatment almost all LiCoO2 decomposed. The sintering constant n varied from 0.27 to 0.37, which suggested that grain-boundary diffusion was the primary mechanism for material transport. For all the compositions considerable morphological changes took place during thermal treatment.

Effect of the method of obtaining Li2CO3LiyNi1−yO mixtures on the densification of the resulting LixNi1−xO solid solutions

Abstract The weight and plaque diameter change following trermal treatment, and the density and lattice constant of lithium-rich Li x Ni 1− x O solid solutions obtained by heat treatment at 750°C of Li 2 CO 3 Li y Ni 1− y O ( y x ) mixtures were measured as a function of time. It was found that densification of the solid solutions depends on the method of obtaining the Li 2 CO 3 Li y Ni 1− y O mixtures. When a large amount of carbonate is put into the starting mixtures NiLi 2 CO 3 -binder, and the powders are milled together, sintering occurs; in contrast, when the carbonate is added after the formation of Li y Ni 1− y O solid solution, so that the interstices of the plaque are filled with molten carbonate, the resulting mixtures exhibit no densification. For densification to occur, Li 2 CO 3 must be in intimate contact with the lithium-doped NiO grains.

Li2O evaporation from LixCo1−xO solid solutions at 1200°C

Abstract Lithium loss from Li x Co 1− x O solid solutions at 1200°C was investigated by diffractometric (XRD) and gravimetric measurements. The results of XRD analysis indicated that the time dependence of Li 2 O evaporation from the solid solutions was 0.2 for a nominal Li 10% sample, while for a nominal Li 20% sample, the time dependence changed from 1 to 0.2 following 5 h of isothermal treatment. This dimensionless parameter is related to the evaporation mechanism. The behaviour of the nominal Li 20% sample was related to the presence of layered Li y Co 2− y O 2 solid solution in the external part of the particles. Lithium content of the solid solution attained a constant value of 0.06, independent of nominal lithium content of the sample. Then, the solid solution with x about 0.06 seems to be stable against lithium loss. Experimental weight loss, due to both lithium loss and Li x Co 1− x O stabilization against phase transition, was compared with calculated weight loss using the parameters obtained from XRD analysis.

A review study of the preparation of porous lithium-doped nickel oxide

Abstract The effect of both the kind and composition of starting powders and the thermal treatment of the green compacts on the preparation of porous Li x Ni 1− x O plaques, used as cathode material in molten carbonate fuel cells, are reviewed.