Synergistically Enhanced Electrochemical Performance of Ni-rich Cathode Materials for Lithium-ion Batteries by K and Ti Co-modification

To improve the performance–price ratio of cathode materials, some modified Ni-rich (LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) 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 LiNi 0.8 Co 0.1 Mn 0.1 O 2 (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 Li 2 TiO 3 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 Li 2 TiO 3 coating as a protective layer suppresses side reactions on electrodes to improve the electrochemical performance.