Electrochemical characterizations of Fe-substituted LiNiO2 synthesized in air by the combustion method

The phases that appear in the intermediate reaction steps for the formation of lithium nickel oxide were deduced from XRD and DTA analyses. XRD analysis and electrochemical measurements were performed for LiNi1−yFeyO2 (0.000 ≤ y ≤ 0.300) samples calcined in air after preheating in air at 400 °C for 30 min. Rietveld refinement of the LiNi1−yFeyO2 XRD patterns (0.000 < y ≤ 0.100) was carried out from a [Li,Ni]3b[Li,Ni,Fe]3a[O2]6c starting structure model. The samples of LiNi1−yFeyO2 with y = 0.025 and 0.050 had higher first discharge capacities when compared with LiNiO2 and exhibited better or similar cycling performance at a 0.1 C rate in the voltage range of 2.7–4.2 V. The LiNi0.975Fe0.025O2 sample had the highest first discharge capacity of 176.5 mAh/g and a discharge capacity of 121.0 mAh/g at n = 100. With the exception of Co-substituted LiNiO2, such a high first discharge capacity has not been previously reported.