Effect of Si(IV) substitution on electrochemical, magnetic and spectroscopic performance of nanosized LiMn2-xSixO4

We report a simple and cheap process for the synthesis of Si substituted LiMn2O4. The resulting materials are composed of partially sintered particles of 80 nm average size, corresponding to single crystalline phases with cubic spinel structures. The substitution of Mn(IV) with Si(IV) in the crystal framework changed the cell parameter and volume, and was confirmed by the evolution observed in the XPS and ESR measurements. A complete magnetic study was carried out. Due to the in-built magnetic frustration within the spinel structure and the competition between different exchange pathways, the insertion of different quantities of Si(IV) causes significant differences in the properties. The electrochemical study revealed that introducing a small amount of Si(IV) enhances the electrochemical performance of the spinel. The highest specific capacity and rate discharge capability were obtained for LiMn1.95Si0.05O4, while insertion of a higher amount of the tetravalent dopant caused deterioration of the electrochemical behavior.