Enhanced cycling stability of nickel-rich layered oxide by tantalum doping

Ni-rich layered oxide cathode material is considered as a promising cathode material in Li-ion batteries owing to their high specific capacity. However, it suffers from poor cycling performance which hinder their commercial applications. The unstable oxygen retention is one of the main causes of structural deformation as well as lower cycling stability. Herein, a simple high-temperature solid state method is utilized to synthesize surface tantalum doped Ni-rich layered oxide cathode material (LiNi0.88Co0.09Al0.03O2) due to the stronger bond between Ta-O which intensifies the TM-O layer due to the positioning of Ta5+ in the TM layer. In the meantime, based on density functional theory (DFT) calculations it has been confirmed that the Ta-doped structure exhibits metallic behavior and lower Fermi level therefore it acquires better phase stability. The 1 wt% Ta-doped NCA (T2-NCA) reveals the best cycling performance of about 93% (4.3V at 1C). Even, it retains good cycling stability of 75% at high voltage (4.5 V) and 97.7% at high C-rate (5C). Therefore, a small amount of Ta surface doping on NCA plays an unneglectable role for enhancing the initial discharge capacity and cycling stability.