Limiting cationic mixing and lattice oxygen loss of single-crystalline Ni-rich Co-poor cathodes for high-voltage Li-ion batteries
Hujun Zhang, Haifeng Yu, Ling Chen, Muslum Demi̇r, Qilin Cheng, Hao Jiang
Abstract
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 0.85 Co 0.05 Mn 0.10 O 2 (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. The anion-cation synergistic strategy lowers the lithiation temperature of single-crystalline NCM85 and strong TM-F bonds are formed. Therefore, a highly ordered and robust layered structure is obtained operating at high voltage. • The highly-ordered single-crystalline Ni-rich cathodes by K/F co-doping are reported. • The sintering temperature is effectively lowered and strong TM-F bonds are created. • The as-prepared Ni-rich cathodes show superior rate capability and durable cycle life.