A nanosized LiMn2O4 (nano-LiMn2O4) spinel was prepared by a novel route using a porous silica gel as a sacrificial hard template. This material was found to be made up of 8–20 nm nanoparticles with a mean crystallite size of 15 nm. The electrochemical properties of nano-LiMn2O4 were tested in lithium cells at different cycling rates and compared to those of microsized LiMn2O4 (micro-LiMn2O4) obtained by the classical solid state route. Microsized LiMn2O4 is formed by 3–20 μm agglomerates, the size of each individual particle being approximately 0.20 μm. The behaviour of nano-LiMn2O4 as a positive electrode improves with increasing current densities (from C/20 to 2C). Moreover, it was found to exhibit a noticeably better performance at high rates (2C), with higher initial capacity values and very good retention (only 2% loss after 30 cycles), with respect to micro-LiMn2O4, almost certainly due to enhanced lithium diffusion in the small particles.

Dr. Heiner Santner is thanked for his assistance in carrying out the electrochemical experiments. TVS thanks CSIC-ESF for the award of a postdoctoral I3P contract. The financial support for this research provided by the Spanish MCyT (MAT2005-00262) is gratefully acknowledged.

7 pages, 4 figures, 1 table.-- Printed version published Apr 15, 2007.

Peer reviewed