Limiting cationic mixing and lattice oxygen loss of single-crystalline Ni-rich Co-poor cathodes for high-voltage Li-ion batteries

Developing cost-effective single-crystalline Ni-rich Co-poor cathodes operating at high-voltage is one of the most important ways to achieve higher energy Li-ion batteries. However, the Li/O loss and Li/Ni mixing under high-temperature lithiation result in electrochemical kinetic hysteresis and structural instability. Herein, we report a highly-ordered single-crystalline LiNi_0.85Co_0.05Mn_0.10O₂ (NCM85) cathode by doping K⁺ and F^- ions. To be specific, the K-ion as a fluxing agent can remarkably decrease the solid-state lithiation temperature by ∼30 °C, leading to less Li/Ni mixing and oxygen vacancy. Meanwhile, the strong transitional metal (TM)-F bonds are helpful for enhancing de-/lithiation kinetics and limiting the lattice oxygen escape even at 4.5 V high-voltage. Their advantages synergistically endow the single-crystalline NCM85 cathode with a very high reversible capacity of 222.3 mAh g^-1. A superior capacity retention of 91.3% is obtained after 500 times at 1 C in pouch-type full cells, and a prediction value of 75.3% is given after cycling for 5000 h. These findings are reckoned to expedite the exploitation and application of high-voltage single-crystalline Ni-rich cathodes for next-generation Li-ion batteries.