Cost‐effective Synthesis of α‐LiAlO₂ Powders for Molten Carbonate Fuel Cell Matrices

Abstract

Lithium aluminate (α‐/β‐LiAlO2) particles were fabricated using three methods. The first method used organic glycerin and triethylene glycol which functioned as a catalyst for fabrication of α‐LiAlO2 particles with Al(OH)3 and LiOH·H2O as the starting materials. As a result of the heat‐treatment of the starting materials, α‐/β‐LiAlO2 particles could be obtained. The amount of α‐LiAlO2 particles in α‐/β‐LiAlO2 increased slightly as more organics were added. Additionally, when synthesised α‐/β‐LiAlO2 particles were heat‐treated in a CO2 gas flow, β‐LiAlO2 was partially transformed to α‐LiAlO2. In the second method, molten salts (Li2/Na2/K2CO3) were used as a catalyst to fabricate α‐LiAlO2 as a major phase, however, this method requires a washing process which can produce unexpected impurities. In the third method, pure α‐LiAlO2 was obtained by heat‐treatment of cheap sources such as Li2CO3 and Al(OH)3 at 600–800 °C. The mean particle size (604 nm–11.85 μm) and the specific surface area (3.22–11.4 m2 g–1) of α‐LiAlO2 were suitable for reinforcing the matrix and tape casting. Lastly, this study examined the effect of CO2 for the synthesising of α‐LiAlO2 particles.

Tailoring the phase of Li–Al–O nanoparticles by nonaqueous sol–gel chemistry

“…The increase in dimension was related to a decrease in SSA that however was observed to be higher than 55 m 2 g −1 . This value is in line, if not higher, with the SSA values reported in the literature for γ- LiAlO 2 [36,38,57,58]. Nevertheless, a major advantage has to be pointed out for the proposed method.…”

“…The conversion temperature α, β→γ depends on the synthesis parameters and lies between 400 and 1000 °C [36]. α-LiAlO 2 and γ-LiAlO 2 are the main component for ceramic matrixes in molten carbonate fuel cells due to their low solubility in the electrolyte and relatively good stability at high temperature and operating conditions [37][38][39]. β-LiAlO 2 phase is less investigated due to the difficulties in the synthesis of a phase-pure product and to the limited temperature range of stability.…”

Stability of lithium aluminate in reducing and oxidizing atmospheres at 700 °C

“…The LiAlO 2 powder samples were prepared by solid-state synthesis method reported by Choi, et al [16]. The precursor materials, Al(OH) 3 (>99.9% pure) and…”

“…A mixture of Li 2 CO 3 and Al(OH) 3 were dried at 60ºC for 24 hours followed by heat-treated at 650ºC for 24 hours in a pure CO 2 atmosphere. The final powders were produced by eliminating the residual carbonate by washing [16]. Formation of minor-phase lithium aluminum oxide hydrate, LiOH…”

A review on MCFC matrix: State-of-the-art, degradation mechanisms and technological improvements

“…Since Al 2 O 3 is an expensive precursor, alternatively the boehmite (AlOOH·nH 2 0) can be mixed with LiOH in water, which makes the synthesis procedure low-cost, energy saving and environmentally friendly since the boehmite is a quite cheap material with a high dispersion in water [ 46 ]. It has been also investigated α -LiAlO 2 powder synthesis using industrial grade Al(OH) 3 and Li 2 CO 3 as precursors which permit to obtain a matrix with a high mechanical strength [ 52 ].…”