Physical and electrochemical properties of iron-doped lithium–manganese-spinels prepared by different methods

Solid solutions of the general formula LiFeyMn2 − yO4 (0 ≤ y ≤ 1) were prepared in two different ways using a classical solid-state synthesis (SSS) and an auto-ignition method (AIM). The samples structure and texture were characterized by X-ray diffraction and High Resolution Transmission Electron Microscopy. Electrical and electrochemical properties of the samples were investigated by conductivity measurements and by charge–discharge in galvanostatic mode versus Li. Samples with y > 0.7 obtained by AIM were not homogeneous and contained impurities of Li2MnO3 or spinel phases with different lattice parameters. The auto-ignition method technique allows us to obtain nanocrystalline materials with a particle size of 20–60 nm. The value of electrical capacity depends of preparation method: capacity of samples obtained by AIM is higher on the first cycle, however, it falls essentially already on the second cycle.