Synthesis, thermal and electrical properties of Li1+δMn2-δO4 prepared by a sol-gel method

The Li1 + deltaMn2 - deltaO4 samples (0. 00 less than or equal to delta less than or equal to 0.20) were obtained by a sol - gel method and characterized using: chemical analyses, XRD, SEM, TGA, DSC, electric conductivity and thermoelectric power. The obtained results were discussed in relation to the calcination temperature, and to the results obtained on commercial LiMn2O4. The samples calcined at 300 degreesC (S-samples) consisting small excess of Li (delta less than or equal to 0.04) showed no phase transition at 285 K and no disturbance in electric conductivity and thermoelectric power, as observed for the related samples calcined at 800 degreesC (H-samples). Partial thermal decomposition of the S-samples or oxygen uptake by the H-samples were observed during TGA experiments above 350 degreesC. The beginning of the thermal decomposition of the H-samples started at higher temperatures, depending on Li-contents. At about 920 degreesC, the rapid acceleration took place independently on type of the samples. The thermal decomposition up to 800 degreesC seems to be reversible, owing to the samples reoxidation. (C) 2002 Elsevier Science B.V. All rights reserved.