Improved performance of rare earth doped LiMn2O4 cathodes for lithium-ion battery applications†
Different rare-earth element (Dy, Gd, Tb and Yb) doped LiMn2O4 spinel active materials were prepared by a sol–gel method. The rare earth doping elements decrease the particle size but do not affect the formation of a cubic spinel structure. Furthermore, these dopants have a strong influence on the overall electrical properties of the cathodes prepared from them. In cyclic voltammetry measurements, two pairs of separated redox peaks are observed, regardless of the dopant. LiMn2O4 materials doped with gadolinium (Gd) and dysprosium (Dy) exhibit comparable room temperature rate capabilities to pristine LiMn2O4, with a discharge capacity of 94.5 mA h g−1 and 82.3 mA h g−1, respectively, versus 73.4 mA h g−1 for pristine LiMn2O4 at a rate of C5. Terbium (Tb) and ytterbium (Yb) doping shows, on the other hand, lower performance. After 50 cycles at C2, the capacity fade is 7% for LiMn1.95Dy0.05O4 and 14% for LiMn1.95Gd0.05O4, whereas for LiMn2O4 it is 32%. The improved cycling performance of LiMn2O4 doped with Gd and Dy is attributed to the powder size and atomic radii of the elements. The differences of the capacity retention on cycling are attributed to superior structural stability due to the rare earth doping. These results indicate that improved cathode materials doped with rare earth elements are suitable for lithium-ion battery applications.