Effect of Al-substitution on the stability of LiMn2O4 spinel, synthesized by citric acid sol-gel method

Spinel LiMn2O4 and LiAlxMn2-xO4 (x = 0.05, 0.15) are synthesized by a sol-g el method using citric acid as a chelating agent. The effect of calcination temperature on the purity of the Al-substituted spinel is examined by X-ra y diffraction measurements which suggests that pure material is obtained by calcination at 800 degreesC. Cyclic voltammetry is, employed to characteri ze the reactions of lithium insertion into and extraction from the spinel m aterials. Surface morphology changes are observed by scanning electron micr oscopy (SEM) and transmission electron microscopy (TEM). The results indica te that Al-substitution enhances sintering of the spinel LiMn2O4. Charge-di scharge cycling studies show that Al-substitution improves substantially th e capacity retention of the spinel LiMn2O4. (C) 2001 Elsevier Science B.V. All rights reserved.