Synergistic effect of uniform lattice cation/anion doping improved structural and electrochemical performance stability for Li-rich cathode materials.

Although the properties of high energy density and low costs have contributed the extensive research of Lithium-rich layered oxide materials as a candidate of next-generation cathode materials in lithium-ion batteries, present poor cyclic life, and fast voltage fade hinder their large-scale commercial applications. Here, we propose a novel cation/anion (Na+/PO43-) co-doping approach to mitigate the discharge capacity and voltage fade of Co-free Li1.2Ni0.2Mn0.6O2 cathode. Results show that the synergistic effect of cation/anion can obviously promote the long cycle stability and rate performance by inhibiting the phase transformation of layered structure to spinel or rock-salt structure and stabilizing the well-order crystal structure during long cycle. 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 for accelerating the Li diffusion and the large tetrahedral PO43- polyanions with high electronegativity stabilize the local structure for improving the electrochemical performance.