Nanomaterials are becoming important for use in Li-ion battery electrodes as these can deliver increased capacity and improved power performance. Our work is focused on Mg-doped high-voltage spinet materials, such as LiNi0.5Mn1.5O4, in order to improve its stability. LiMg delta Ni0.5-delta Mn1.5O4 with delta=0.05, having the cubic spinel structure (P4(3)32) were made via four different synthesis routes - a solid-state route, a sol-gel method, a xerogel route and an auto ignition method. The powders were investigated with SEM and TEM analysis. XRD was used to determine the crystallographic structure. Electrochemical tests were performed in CR2320 coin cells built with 1 M LiPF6 in EC/EMC/DMC 1:2:2 as electrolyte and metallic Li as negative electrode - cells were measured with a MACCOR cycler. LiMg0.05Ni0.45Mn1.5O4 made via the sol-gel and xerogel routes revealed agglomerated nanoparticles with sizes ranging from 10 to 200 nm, whereas the auto ignition method gives particle sizes between 10 and 50 nm. Although agglomerated, often residual LiMn2O4 is observed, with increasing concentration going from solid-state, sol-gel, xerogel to auto ignition. Hence, thanks to these different synthesis routes, we are able to obtain particle sizes reaching from 10 to 200 nm, with a narrow particle size distribution. The electrochemical tests of the xerogel particles showed promising results. The auto ignition method show also promising results, however, the impurity phase needs to be suppressed significantly. The sol-gel method, the xerogel route and the auto ignition method show increased capacity retention at high power rates compared to the solid state method. (c) 2006 Published by Elsevier B.V.