An investigation of intercalation-induced stresses generated during lithium transport through sol-gel derived LixMn2O4 film electrode using a laser beam deflection method

Abstract

The stress changes Delta sigma generated during lithium transport through the sol-gel derived LixMn2O4 film electrodes annealed at 773 and 873 K were quantitatively determined as a function of the lithium stoichiometry x using a laser beam deflection method (LBDM). Delta sigma generated during a real potential step between an initial electrode potential and a final applied potential was uniquely specified by the Delta sigma versus x curve. The LixMn2O4 film annealed at 773 K for 24 h (low temperature (LT)-LixMn2O4) showed larger capacity than the LixMn2O4 film annealed at 873 K for 6 h (high temperature (HT)-LixMn2O4) and this result is ascribed to the fact that the smaller the grain size is, the more increases the electrochemically active area of the film electrode. From the analysis of the normalised Delta sigma transient measured simultaneously along with the cyclic voltammogram in the potential range of 2.5-3.4 VLi/Li+, it is found that normalised Delta sigma generated in the LT-LixMn2O4 was smaller than that in the HT-LixMn2O4 during the lithium intercalation/de-intercalation around 3.0 VLi/Li+ region. This result gives an experimental evidence for the fact that the Jahn-Teller distortion is suppressed by the increase in the average oxidation state of manganese with decreasing in annealing temperature. (C) 2005 Elsevier Ltd. All rights reserved.