Preparation of Co1−zAlz(OH)2(NO3)z Layered Double Hydroxides and Li(Co1−zAlz)O2

Abstract

The precipitate formed by the addition of an aqueous solution of Co(NO3)2 and Al(NO3)3 to LiOH solution has been thoroughly studied as a function of the Al:(Al+Co) ratio, z, for 0 ≤ z ≤ 1, using X-ray diffraction and thermogravimetric analysis. For 0 ≤ z ≤ 0.2, the precipitate was a mixed phase of Co(OH)2 and the layered double hydroxide (LDH) Co0.8Al0.2(OH)2(NO3)0.2·nH2O. For 0.2 ≤ z ≤ 0.4 the precipitate was a single LDH phase containing both NO3− and CO32− ions to compensate the Al3+ charge. As z increases in this range, the amount of NO3− decreases and the amount of CO32− increases. For z > 0.4, the precipitate was a two phase mixture of an LDH phase and Al(OH)3. Li[Co1−zAlz]O2 samples were made from the coprecipitated products for 0 ≤ z ≤ 0.5, by calcining the coprecipitate and Li2CO3. These Li[Co1−zAlz]O2 samples were compared to samples of the same stoichiometries made by the direct solid state reaction of Co3O4, Al(OH)3, and Li2CO3. The lattice constants varied smoothly with z for the Li[Co1−zAlz]...