| Resumo: | Different rare-earth elements (Dy, Gd, Tb and Yb) doped LiMn 2 O 4 spinel active material were prepared by sol-gel method. The rare earth doping elements decrease particle size but do not affect the formation of cubic spinel structure. Further, these dopants have strong influence in the overall electrical properties of the cathodes prepared from them. In the cyclic voltammetry measurements, two pairs of separated redox peaks are observed, independently to dopants. LiMn 2 O 4 doped gadolinium (Gd) and dysprosium (Dy) exhibit a comparable room temperature rate capability to pristine LiMn 2 O 4 with discharge capacity of 94.5 mAh g -1 and 82.3 mAh g -1 , respectively, versus 73.4 mAh g -1 for pristine LiMn 2 O 4 at a rate of C5. Terbium (Tb) and ytterbium (Yb) doping show, on the other hand, lower performance. After 50 cycles at C2, the capacity fade is 7% for LiMn 1.95 Dy 0.05 O 4 and 14% for LiMn 1.95 Gd 0.05 O 4 , whereas for LiMn 2 O 4 it is 32%. The improved cycling performance of LiMn 2 O 4 doped with Gd and Dy is attributed to the powder size and atomic radius of the elements. Differences of the capacity retention on cycling are attributed to superior structural stability due to rare earth doping. These results indicate that improved cathode materials doped with rare earth element are suitable for lithium-ion battery applications |
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