Phase and Microstructure stabilities of LiAlO_2 in molten Li/NA carbonate for molten carbonate fuel cells

摘要

The phase and microstructure stabilities of LiA102 for improving the matrix reliability of molten carbonate fuel cells are investigated. The phase transformation and particle growth of LiAlO_2 are examined via immersion tests of pure gamma-LiAlO_2,an alpha-LiAlO_2 mixture and pure alpha-LiAlO_2 in molten carbonate at 650 deg C in an air atmosphere. Dissolution of Li~+ ions occurs mainly from gamma-LiAlO_2 over an 18 000h period, and the dissolved Li+ ions precipitate as LiNaCO_3 and a-LiAlO_2. Particle growth takes place continuously from an early stage of heat-treatment and quickly progresses by the accelerated dissolution and precipitation of Li~+ ions after 10 000 h. By contrast, the particle size and the crystalline phase of alpha-LiAlO_2 do not change during 3000 h of immersion. These results show that alpha-LiAlO_2 is less soluble than Y-LiAlC_2 and is more stable in molten carbonate.