Mechanochemical synthesis of LiMn2O4 cathode material for lithium batteries

The mechanochemical method was used for the synthesis of highly dispersed stoichiometric and nonstoichiometric LixMn2O4 spinel starting from different manganese (MnO2, Mn2O3, MnO) and lithium (LiOH, LiOH . H2O, Li2CO3) compounds. It is shown that the oxidation state of manganese greatly influences on the kinetics of mechanochemical reactions. On the other hand, different crystal structure and mechanical properties of initial lithium compounds result in different mechanisms of mechanochemical action on the activated mixtures. A strong effect of temperature and lithium content on the composition and lattice constant of the final products was found. Conductivity of LixMn2O4 spinels, measured by complex impedance spectroscopy, is likely caused by intergrain resistance. The activation energy of conductivity does not depend on x, the phase transition at 290+/-10 K, observed for stoichiometric spinel, is accompanied by a conductivity decrease. Test experiments in the electrochemical cell Li/LiPF6, EC/LiMn2O4,C demonstrate that lithium-manganese oxide obtained by the mechanochemical method is a promising cathode material for 4 V lithium batteries. (C) 2000 Elsevier Science B.V. All rights reserved.