Experimental and Theoretical Study of LiMn2O4 Synthesized by the Solution Combustion Method Using Corn Starch as Fuel

Abstract

Lithium manganese oxide, LiMn 2 O 4 , was synthesized in two temperature stages, where the first consisted by an ecofriendly solution combustion method at 300 °C. Finally, the as-burned powders were thermal treated at 500 and 700 °C. The structural and morphological changes were evaluated by the Rietveld method and density functional theory (DFT) calculations. The Rietveld refinement indicates obtaining the spinel cubic phase LiMn 2 O 4 and a small amount of Mn 2 O 3 . The analyses by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show a porous microstructure composed of nano-sized crystallites for the sample treated at 500 °C. In cyclic voltammetry, it was possible to observe that the reduction-oxidation reaction is reversible due to the shape of voltammograms and the anodic and cathodic peaks of Mn ions. The theoretical calculations considered the experimental crystallographic parameters. The unit cell volume change was evaluated according to distinct amounts of lithium ions in the structure. The removal of the Li + cations from the oxides promotes a volume contraction. Therefore, it was possible to evaluate the participation of the Mn 3+ ions in the frontier region between the valence and conduction bands. The density of states (DOS) calculation shows a predominant contribution of the O 2p and Mn 3d orbitals in the frontier orbitals.

Combustion Synthesis of Semiconductor Oxides and Evaluation of Adsorption and Photocatalysis Properties

“…The crystallographic date of these phases (summarized in Table 1) is compatible with the literature (Chen et al 2017). Both materials present their crystalline phases with nanometric crystallite sizes (Table 1), according to the Scherrer equation (Siqueira Junior et al 2019).…”

“…For adsorption, activated carbon is widely used due to its high surface area, as also some nanostructured iron oxides and nanostructured ZnO (Rani et al 2017). Due to their semiconductor and piezoelectric properties, ZnO has also been used in the preparation of optoelectronic devices that have application in the aerospace sector (Fernandes et al 2016;Safyanu et al 2019) This work aims the synthesis of ZnO and the magnetic composite ZnO/ZnFe 2 O 4 by the combustion method using starch as fuel (Argolo et al 2019;Siqueira Junior et al 2019). The obtained materials were evaluated in the adsorption and photodegradation processes of the methylene blue dye, using a low cost commercial visible light source for photocatalytic evaluation.…”

Molten salt synthesis of LiMn 1 . 2 Ni 0 . 3 Cr 0 . 1 Co 0

“…To study induced deformation in the sample and their crystallite size, the Williamson‐Hall method was used. The strain induced and crystallite size in the sample are determined by the relation 42 where β is the full width at half maximum, λ is the wavelength of Cu(K α ), ε is strain induced, and θ is the Bragg's diffraction angle.…”

Pressure Effect on the Structural, Electronic, and Magnetic Properties of the Battery Cathode Material Limn2o4: An Ab-Initio Study

“…In this compound, Mn 3+ (configuration: e 2 g , b 1 2g , a 1 1g , b 0 1g ) is a Jahn-Teller (JT) active ion. On the other hand, Mn 4+ (configuration: t 3 2g , e 0 g ) is not a JT active ion [8][9][10]. In recent years, density functional theory (DFT) [11,12] has been widely used to study energy storage [13].…”