The elevated temperature performance of the LiMn2O4/C system:: failure and solutions

This paper reviews various chemical approaches that have participated in the improvement of the high temperature performance of the LiMn2O4/C Li-ion system. These approaches range from chemical surface and bulk modification of the spinel to the improvement of electrolyte stability towards acidification, and to the stabilization of the SEI chemistry of the carbon anode. More specifically, we describe the advantages of (1) modifying the surface chemistry of the spinel in order to obtain encapsulated particles or (2) modifying the crystal chemistry of the spinel through dual cationic and anionic substitutions by improving its stability towards Mn dissolution. The role of the carbon negative electrode towards the high temperature issue, namely through the formation/dissolution of the SEI layer is discussed, and a way of controlling such an SEI layer through a pre-conditioning of the cell is presented. The benefit of adding zeolites to the Li-ion cell to trap some of the species (H+, or others) generated during cell functioning as the result of the electrolyte decomposition or SEI layer is presented. Finally, from a compilation of other reports on that topic together with the present work, our present understanding of the failure mechanism in the LiMn2O4/C system is elucidated. (C) 1999 Elsevier Science Ltd. All rights reserved.