Synergistic effect of uniform lattice cation/anion doping to improve structural and electrochemical performance stability for Li-rich cathode materials
Hao Liu, Bin He, Wei Xiang, Yongchun Li, Changjiang Bai, Yongpeng Liu, Zhou Wei, Xianchun Chen, Yuxia Liu, Shuyan Gao, Xiaodong Guo
Abstract
Abstract There has been extensive research into lithium-rich layered oxide materials as candidates for the nextgeneration of cathode materials in lithium-ion batteries, due to their high energy density and low cost; however, their poor cycle life and fast voltage fade hinder their large-scale commercial application. Here, we propose a novel cation/anion (Na + /PO 4 3– ) co-doping approach to mitigate the discharge capacity and voltage fade of a Co-free Li 1.2 Ni 0.2 Mn 0.6 O 2 cathode. Our results show that the synergistic effect of cation/anion doping can promote long cycle stability and rate performance by inhibiting the phase transformation of the layered structure to a spinel or rock-salt structure and stabilizing the well-ordered crystal structure during long cycles. The co-doped sample exhibits an outstanding cycle stability (capacity retention of 86.7% after 150 cycles at 1 C) and excellent rate performance (153 mAh g −1 at 5 C). The large ionic radius of Na + can expand the Li slab to accelerate Li diffusion and the large tetrahedral PO 4 3– polyanions with high electronegativity stabilize the local structure to improve the electrochemical performance.