A Simple Dual-Ion Doping Method for Stabilizing Li-Rich Materials and Suppressing Voltage Decay.

A gentle method is used to treat the precursor to induce the doping of SO42- and Ni2+. The doped SO42- induces the formation of oxygen vacancies and defects, which are beneficial for inhibition of the loss of O2-, stabilization of the structure, and amelioration of voltage decay, and the doped Ni2+ increases the degree of lithium nickel mixing and significantly increases the midvoltage. After modification, the specific discharge capacity reaches 305.20 mAh g-1, with a Coulombic efficiency of 86.20% (the specific discharge capacity and Coulombic efficiency of the original material are only 276.50 mAh g-1 and 77.30%, respectively). In addition, the cycle performance is also significantly improved, and the discharge midvoltage is dramatically increased from 2.74 to 3.00 V after 350 cycles at a large current density of 1C due to the dual-ion synergistic effect. In summary, these results show that the materials exhibit not only a more stable structure but also better electrochemical performance after modification.