Synergistically Enhanced Electrochemical Performance of Ni-rich Cathode Materials for Lithium-ion Batteries by K and Ti Co-modification
Wenli Yao, Yong Liu, Dong Li, Qian Zhang, Shengwen Zhong, Hongwei Cheng, Zhengquan Yan
Abstract
To improve the performance–price ratio of cathode materials, some modified Ni-rich (LiNi₀.₈Co₀.₁Mn₀.₁O₂) materials are identified by K and Ti single-doping or comodification using a simple coprecipitation method following by a proper post-treatment. The slab spacings for all the modified materials are broadened due to the doping of K and Ti. In particular, for K,Ti comodified LiNi₀.₈Co₀.₁Mn₀.₁O₂ (NCM-K-Ti), it possesses remarkably improved cycling and rate performances, i.e., 160.42 mAh g–¹ discharge capacity and 91.19% capacity retention at 1C after 200 cycles between 2.75 and 4.35 V. When being applied in graphite/NCM-K-Ti batteries, NCM-K-Ti keeps a high discharge capacity (173.74 mAh g–¹) and excellent capacity retention rate (91.62%) at 200th cycle at 0.2 C between 2.75 and 4.2 V. The enhanced mechanism is from the synergistic effect among codoping K and Ti and Li₂TiO₃ coating. Enlarging the interlayer spaces by K doping will open Li⁺ transporting channels to accelerate Li⁺ transport rate. Ti doping can strengthen Ni–O bonds to improve the structure stability. Furthermore, a certain Li₂TiO₃ coating as a protective layer suppresses side reactions on electrodes to improve the electrochemical performance.