Achieving superior electrochemical performances on LiNi0.8Co0.15Al0.05O2 cathode materials by cadmium oxide modification

Abstract

Cadmium oxides (CdO), an important semiconductor material, have many superior properties when used as a cathode material for nickel-cadmium batteries. Here, the coating and the doped co-modified LiNi0.8Co0.15Al0.05O2 cathode are constructed by a continuous wet chemical process and a high-temperature sintering process, wherein the Cd2+ are uniformly doped in a gradient form and the CdO protective layer is distributed on the outer surface of secondary particles. The Cd-modified NCA material has more stable interfacial and crystal lattice structure, thereby inhibiting harmful phase transitions and side-reactions. Accordingly, the modified sample has excellent electrochemical performance and maintaining a complete spherical morphology during long cycling compared to the pristine sample. In addition, as a pillar ion, cadmium increases the plate spacing and lithium-ion diffusion kinetics. The electrochemical results show that the capacity retention of the modified sample Cd-2000 reached 96.5% and 90.6% after 100 cycles and 200 cycles respectively at 1 C. At the high current rate of 8 C, the initial capacity and retention (100 cycles, 3.0–4.3 V) reach 166.2 mAh g−1 and 95.2%, respectively. Besides, the results of electrochemical impedance spectroscopy (EIS) reveal that CdO modification could decrease the resistance of the cell polarization and impedance increment upon cycling.