Substitution effects on the bulk and surface properties of (Li,Ni)Mn2O4

• Published in: Ionics 2018-04, Vol.24 (4), p.977-987
• Main Authors: Alburquenque, D., Denardin, J. C., Troncoso, L., Marco, J. F., Gautier, J. L.
• Format: Article
• Language: English
• Subjects: Accuracy; Agglomerates; Atomic structure; Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electrochemistry; Energy Storage; Ferrimagnetism; Formulations; Lithium manganese oxides; Manganese; Nickel; Optical and Electronic Materials; Original Paper; Oxidation; Renewable and Green Energy; Sol-gel processes; Spinel; Surface properties; Ultrasonic testing; Ultrasound; Valence; X ray photoelectron spectroscopy
• ISSN: 0947-7047; 1862-0760
• DOI: 10.1007/s11581-017-2266-8

Manganese oxides of spinel structure, LiMn 2 O 4 , Li 1- x Ni x Mn 2 O 4 (0.25 ≤  x ≤ 0.75), and NiMn 2 O 4 , were studied by EDS, XRD, SEM, magnetic (M-H, M-T), and XPS measurements. The samples were synthesized by an ultrasound-assisted sol-gel method. EDS analysis showed good agreement with the formulations of the oxides. XRD and Rietveld refinement of X-ray data indicate that all samples crystallize in the Fd3m space group characteristic of the cubic spinel structure. The a -cell parameter ranges from a  = 8.2276 Å ( x  = 0) to a  = 8.3980 Å ( x  = 1). SEM results showed particle agglomerates ranging in size from 2.3 μm ( x  = 0) down to 0.8 μm ( x  = 1). Hysteresis magnetization vs. applied field curves in the 5–300K range was recorded. ZFC-FC measurements indicate the presence of two magnetic paramagnetic-ferrimagnetic transitions. The experimental Curie constant was found to vary from 5 to 7.1 cm 3  K mol −1 for the range of compositions studied (0 ≤  x  ≤ 1). XPS studies of these oxides revealed the presence of Ni 2+ , Mn 3+ , and Mn 4+ . The experimental Ni/Mn atomic ratios obtained by XPS were in good agreement with the nominal values. A linear relationship of the average oxidation state of Mn with Ni content was observed. The oxide’s cation distributions as a function of Ni content from x  = 0  Li + [Mn 3+ Mn 4+ ]O 4 to x  = 1 Ni 0.35 2 + Mn 0.65 3 + Ni 0.65 2 + Mn 1.35 3 + O 4 were proposed.