Revisiting the layered LiNi0.4Mn0.4Co0.2O2: a magnetic approach

Abstract

Layered LiNi_0.4Mn_0.4Co_0.2O₂ has been synthesized by the co-precipitation method, and the structural, electrochemical and magnetic properties were comprehensively studied by Rietveld analysis, charge–discharge potential profiles, X-ray photoelectron spectroscopy, and dc and ac susceptibilities. The material shows initial discharge capacities of 166 and 206 mA h g⁻¹ in potential windows of 2.5–4.4 V and 2.5–4.6 V, respectively, and a better capacity retention of 95% at 2.5–4.4 V after 50 cycles. The effective paramagnetic moment is calculated to be 3.02(3) μ_B/f.u. by fitting to the Curie–Weiss law, which is consistent with the averaged value, based on the specific contributions, as quantified by an analysis of the X-ray photoelectron spectroscopy data. The dc magnetization curves show irreversibility and spin freezing behavior at 77 K and 18 K, respectively. The evolution of irreversibility temperature under different applied fields indicates a spin-glass-like transition. The ac susceptibility data and the fitting using the frequency dependent spin-freezing temperatures also confirm this magnetic transition. In comparison with the previous results, the co-precipitation prepared sample shows a big difference in the magnetic parameters, coming from the different microscopic exchange interactions or the formation of a different scale of spin clusters, which is sensitive to the preparation procedure.