Preparation and characterization of LiNi0.8Co0.15Al0.05O2 with high cycling stability by using AlO2- as Al source

We report the preparation of a series of LiNi0.8Co0.15Al0.05O2 materials with different reaction time (10, 20, 30 and 40 h) of precursor and their electrochemical properties as cathode material for lithium-ion batteries (LIBs). The preparation of LiNi0.8Co0.15Al0.05O2 was divided into two steps: a co-precipitation process to obtain Ni0.8Co0.15Al0.05(OH)2 precursor and a calcination step with LiOH. During the co-precipitation process, AlO2- was employed as Al source so as to guarantee Ni2+, Co2+ and Al3+ co-precipitation. The impacts of different synthesis time of the precursor on crystal structure, morphology and electrochemical performance of LiNi0.8Co0.15Al0.05O2 were systematically investigated. The samples with various synthesis time of precursor possessed spherical morphology and a layered α-NaFeO2 structure with R-3m space group. Especially, when the reaction time of precursor was 30 h, the LiNi0.8Co0.15Al0.05O2 had the weakest degree of Li+/Ni2+ ions mixing and the best uniformity and integrity. When used as cathode materials for LIBs, the LiNi0.8Co0.15Al0.05O2 with 30 h exhibited high discharge capacity, good cycling performance and remarkable rate capability. The maximum discharge capacity was 202.3 mAh g−1 at 0.1 C and the capacity retention approached 99.4% after 100 cycles at 1 C. At 10 C, the discharge capacity exceeded 140 mAh g−1, suggesting a possible application in the high rate LIBs. The excellent electrochemical performance might be attributed to the uniform co-precipitation of Ni2+, Co2+ and Al3+ and well layered structure with less Li+/Ni2+ mixing.