Effect of Nb and F Co-doping on Li(1.2)Mn(0.54)Ni(0.13)Co(0.13)O(2) Cathode Material for High-Performance Lithium-Ion Batteries

The Li(1.2)Mn(0.54−x)Nb(x)Co(0.13)Ni(0.13)O(2−6x)F(6x) (x = 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(1.2)Mn(0.54)Co(0.13)Ni(0.13)O(2), 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(1.2)Mn(0.54−x)Nb(x)Co(0.13)Ni(0.13)O(2−6x)F(6x) shows suppressed voltage fade and higher capacity retention of 98.1% after 200 cycles at rate of 1 C. The replacement of O(2−) by the strongly electronegative F(−) is beneficial for suppressed the structure change of Li(2)MnO(3) from the eliminating of oxygen in initial charge process. Therefore, the initial coulombic efficiency of doped Li(1.2)Mn(0.54−x)Nb(x)Co(0.13)Ni(0.13)O(2−6x)F(6x) gets improved, which is higher than that of pure Li(1.2)Mn(0.54)Co(0.13)Ni(0.13)O(2). In addition, the Nb and F co-doping can effectively enhance the transfer of lithium-ion and electrons, and thus improving rate performance.