Electrochemical Investigations of Li2Fe0.8-xMn0.2MxSiO4 (M = Mg2+, Zn2+) Cathodes for Lithium Ion Batteries

AUTOR(ES)

Li, Shu-Dan, Zhao, Yun, Wang, Chen-Yi, Gao, Kun

FONTE

J. Braz. Chem. Soc.

DATA DE PUBLICAÇÃO

2016-11

RESUMO

The Mn2+ and Mg2+ (or Zn2+) co-doped Li2Fe0.8-xMn0.2MxSiO4 (x = 0.05 and 0.1) are synthesized by a solid-state reaction route. Compared with the single doped Li2Fe0.8Mn0.2SiO4, the co-doped samples show improved cycling performance. The capacity retention can stay above 50% after 50 cycles, which is significantly higher than 30.4% for Li2Fe0.8Mn0.2SiO4. This phenomenon could be attributed to the increased structural stability caused by the incorporation of the electrochemically inactive M2+ ions. However, except for Li2Fe0.75Mn0.2Mg0.05SiO4, the other samples show decreased capacities, especially in the case of the Mn/Zn co-doping. Further tests indicate that the promotion of Li+ diffusivity may be a key reason for the improved rate and cycling performances. By contrast, the incorporation of Zn2+ impaired the cell performances such as increased internal polarization, hindered charge transfer, decreased Li+ diffusivity. In this work, the Mg2+ with smaller radius seems to be a better choice as the co-doping element at Fe sites than Zn2+.

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