Electrochemical characterizations of Fe-substituted LiNiO 2 synthesized in air by the combustion method

Abstract

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 LiNi 1− y Fe y O 2 (0.000 ≤ y ≤ 0.300) samples calcined in air after preheating in air at 400 °C for 30 min. Rietveld refinement of the LiNi 1− y Fe y O 2 XRD patterns (0.000 < y ≤ 0.100) was carried out from a [Li,Ni] 3b[Li,Ni,Fe] 3a[O 2] 6c starting structure model. The samples of LiNi 1− y Fe y O 2 with y = 0.025 and 0.050 had higher first discharge capacities when compared with LiNiO 2 and exhibited better or similar cycling performance at a 0.1 C rate in the voltage range of 2.7–4.2 V. The LiNi 0.975Fe 0.025O 2 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 LiNiO 2, such a high first discharge capacity has not been previously reported.