RESUMO
In this paper, via a facile wet coating method, the LaPO4coating layer has been introduced onto the LiNi0.87Co0.09Al0.04O2(NCA) surface while a small part of La3+has also been doped on the surface to realize the dual functions modification of coating and doping. The morphology and structure of the samples were investigated by XRD, SEM and TEM measurements. The chemical compositions of the samples were analyzed via EDS and XPS data. The results showed that the coating of LaPO4and the doping of La3+were successfully achieved on the surface of NCA. Electrochemical tests indicate that the sample modified with 2 wt% LaPO4(L2-NCA) possesses the best electrochemical performance. After 100 cycles, compared with the capacity retention rate of pristine NCA of 87.1%/74.2% at 0.5 C at 25 °C/60 °C, L2-NCA showed better cycling stability, and the capacity retention rate increased to 96.0%/85.1%, respectively. Besides, the rate performance of the modified samples at 1 C, 2 C and 5 C were also significantly improved. These satisfactory results reveal that the surface modification of LaPO4provides a feasible scheme to uprate the performance of Ni-rich cathode materials.