Modulating electrochemical properties by Fe3+ doping for cobalt-free Li1.2Ni0.26Mn0.54O2 cathode material

Abstract

The widespread application of Li-rich cathode material is restricted due to capacity attenuation and poor rate capability caused by crystal structure transformation and irreversible lattice oxygen escape during cycling. The Fe3+-doped effects on lattice structures and electrochemical properties of Li1.2Ni0.26−xMn0.54FexO2 (x = 0, 0.03, 0.05 and 0.08) cathode materials fabricated by a sol-gel method are systematically studied in this paper. Doped materials exhibit good electrochemical performance such as high discharge specific capacity and capacity retention at high current density rates. Li1.2 Ni0.21Mn0.54Fe0.05O2 can supply a specific capacity of 190.7 mAh g−1 with 73.6 % capacity retention after 100th cycle at 2 C, and rate capacities of 230.6, 208.5, 193.1, 172.1 and 105.6 mAh g−1 at 0.1, 0.5, 1, 2 and 5 C, respectively. It is attributed to the enhanced structural stability, enlarged Li layer spacing, intensive interaction between transition metals and oxygen, less manganese disproportionation and oxygen release and increased Li+ diffusion coefficient by Fe3+ doping.