Effect of doping LiMn2O4 spinel on its use as cathodes in Li-ion batteries

LiMn2O4 spinel is a promising cathode material for Li-ion batteries, and doping it with small amounts of other metal ions has a remarkable effect on its electrochemical properties. In order to elucidate the relationship between structura and the electrochemical performance of doped compounds, with the general formula Li1+yMn2-xM'xO4 (x<=0.1;y<=0.02, M'=dopant metal ion), powder neutron diffraction experiments have been coupled with electrochemical data. Whereas the capacity of the spinels doped with trivalent metal ions is much greater, cyclic fading properties are much enhanced with the use of divalent metal ions. It is suggested that the occupancy of the tetrahedral sites is critical to the improved structural stability on Li insertion/extraction, but that this ultimately hinders the movement of Li.