AUTHOR=Ming Lei , Zhang Bao , Cao Yang , Zhang Jia-Feng , Wang Chun-Hui , Wang Xiao-Wei , Li Hui 

TITLE=Effect of Nb and F Co-doping on Li1.2Mn0.54Ni0.13Co0.13O2 Cathode Material for High-Performance Lithium-Ion Batteries

JOURNAL=Frontiers in Chemistry

VOLUME=6

YEAR=2018

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2018.00076

DOI=10.3389/fchem.2018.00076

ISSN=2296-2646

ABSTRACT=<p>The Li<sub>1.2</sub>Mn<sub>0.54−x</sub>Nb<sub>x</sub>Co<sub>0.13</sub>Ni<sub>0.13</sub>O<sub>2−6x</sub>F<sub>6x</sub> (<italic>x</italic> = 0, 0.01, 0.03, 0.05) is prepared by traditional solid-phase method, and the Nb and F ions are successfully doped into Mn and O sites of layered materials Li<sub>1.2</sub>Mn<sub>0.54</sub>Co<sub>0.13</sub>Ni<sub>0.13</sub>O<sub>2</sub>, respectively. The incorporating Nb ion in Mn site can effectively restrain the migration of transition metal ions during long-term cycling, and keep the stability of the crystal structure. The Li<sub>1.2</sub>Mn<sub>0.54−x</sub>Nb<sub>x</sub>Co<sub>0.13</sub>Ni<sub>0.13</sub>O<sub>2−6x</sub>F<sub>6x</sub> shows suppressed voltage fade and higher capacity retention of 98.1% after 200 cycles at rate of 1 C. The replacement of O<sup>2−</sup> by the strongly electronegative F<sup>−</sup> is beneficial for suppressed the structure change of Li<sub>2</sub>MnO<sub>3</sub> from the eliminating of oxygen in initial charge process. Therefore, the initial coulombic efficiency of doped Li<sub>1.2</sub>Mn<sub>0.54−x</sub>Nb<sub>x</sub>Co<sub>0.13</sub>Ni<sub>0.13</sub>O<sub>2−6x</sub>F<sub>6x</sub> gets improved, which is higher than that of pure Li<sub>1.2</sub>Mn<sub>0.54</sub>Co<sub>0.13</sub>Ni<sub>0.13</sub>O<sub>2</sub>. In addition, the Nb and F co-doping can effectively enhance the transfer of lithium-ion and electrons, and thus improving rate performance.</p>