Enhanced high rate performance of LiMn2O4 spinel nanoparticles synthesized by a hard-template route

Abstract

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.