Synthesis of spinel lithium manganate powders using an inverse emulsion process (original) (raw)
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Preparation of Ceramic Powders From Emulsions
MRS Proceedings, 1986
ABSTRACTYttrium oxide powders were prepared from water-in-oil type emulsions by loading the yttrium ions into the aqueous phase. Emulsions were characterized with respect to droplet size and distribution, emulsion type, and time and temperature stability. Precursor powders were obtained from the emulsions by evaporation of the aqueous phase in a hot oil bath. Powder characteristics, such as size, shape, composition, and sinterability as a function of procedural variables, were determined. The new technique appears to be practical and may be economically feasible.
Journal of the European Ceramic Society, 2004
Ultrafine orthorhombic LiMnO 2 (o-LiMnO 2) were successfully synthesized using a newly developed reverse-microemulsion (RmE) process. To prepare o-LiMnO 2 powders with a rock salt structure, precise control of the oxygen content in the heating atmosphere was required. Monophasic o-LiMnO 2 was obtained at as low as 700 C. Not only the reaction temperature was lowered, the reaction duration for synthesizing the desired powders was also markedly shortened via the RmE route. The average particle size of the 900 C-calcined powders was measured to be around 90 nm. The discharge capacities of the prepared o-LiMnO 2 powders significantly increased in the initial stages, and rapidly reached a saturated plateau. The impedance spectroscopy analysis revealed that the chemical diffusion coefficient of lithium ions in o-LiMnO 2 was markedly greater than that in LiMn 2 O 4-based materials. The high diffusion rate of lithium ions in o-LiMnO 2 is attributed to the high crystallinity as well as the nanosize of the powders synthesized via this RmE process.
Nanostructured Materials, 1993
Synthesis of ultrafine/ultrapure powders was carried out by hydrolysis of metal alkoxides in anhydrous solvents, at various temperatures, using superheated steam for the process. The precursorpowders of alumina, titania, tialite, zirconia, and magnesia obtained were characterized by chemical analysis, physical properties (e.g., BET surface measurements and XRD phase analysis). Thermal treatment of the powders (coMpressing) in the range up to 1400°C showed dehydration in the lower range, phase transitions that not always corresponded to the usual thermodynamic order, and a gradual increase of crystallinity at higher temperatures. Tialite was formed only at temperatures above 1200°C, despite the intimate contact between alumina and magnesia extant in the precursor powders, similarly to the behavior of stoichiometric mixtures of pulverized commercial corundum and rutile. However, reaction with ultrafine precursors was complete, as opposed to the latter mixtures. Densification of powders obtained with superheated steam showed that the particles are probably of less homogeneous shape, possibly more agglomerated, than in the case of ultrafine powders obtained by the usual sol-gel methods, and ways have to be found to improve this characteristic.
Solution combustion synthesis of LiMn2O4 fine powders for lithium ion batteries
Advanced Powder Technology, 2014
In this work, fine powders of spinel-type LiMn 2 O 4 as cathode materials for lithium ion batteries (LIBs) were produced by a facile solution combustion synthesis using glycine as fuel and metal nitrates as oxidizers. Single phase of LiMn 2 O 4 products were successfully prepared by SCS with a subsequent calcination treatment at 600 to 1000 ºC. The structure and morphology of the powders were studied in detail by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The electrochemical properties were characterized by galvanostatic charge-discharge cycling and cyclic voltammetry. The crystallinity, morphology, and size of the products were greatly influenced by the calcination temperature. The sample calcined at 900 ºC had good crystallinity and particle sizes between 500 and 1000 nm. It showed the best performance with an initial discharge capacity of 115.6 mAh g-1 and a capacity retention of 93% after 50 cycles at a 1 C rate. In comparison, the LiMn 2 O 4 sample prepared by the solid-state reaction showed a lower capacity of around 80 mAh g-1 .
Synthesis and characterization of submicron size particles of LiMn 2 O 4 by microemulsion route
Journal of Solid State Electrochemistry, 2008
Among the various positive electrode materials investigated for Li-ion batteries, spinel LiMn2O4 is one of the most important materials. Small particles of the active materials facilitate high-rate capability due to large surface to mass ratio and small diffusion path length. The present work involves the synthesis of submicron size particles of LiMn2O4 in a quaternary microemulsion medium. The precursor obtained from the reaction is heated at different temperatures in the range from 400 to 900 °C. The samples heated at 800 and 900 °C are found to possess pure spinel phase with particle size <200 nm, as evidenced from XRD, SEM, and TEM studies. The electrochemical characterization studies provide discharge capacity values of about 100 mAh g−1 at C/5 rate, and there is a moderate decrease in capacity by increasing the rate of charge–discharge cycling. Studies also include charge–discharge cycling and ac impedance studies in temperature range from −10 to 40 °C. Impedance data are analyzed with the help of an equivalent circuit and a nonlinear least squares fitting program. From temperature dependence of charge-transfer resistance, a value of 0.62 eV is obtained for the activation energy of Mn3+/Mn4+ redox process, which accompanies the intercalation/deintercalation of the Li+ ion in LiMn2O4.
Materials Letters, 2006
Nanocrystalline LiMn 2 O 4 powders were synthesized by Pechini process using metal nitrates/acetates as metal ion sources, citric acid and polyethylene glycol-400. Effect of calcining temperature on the electrochemical performance of nanocrystalline LiMn 2 O 4 powders was investigated. Thermal decomposition of polymeric intermediate was investigated through DSC thermogram. FT-IR was used to identify the structural coordination of as prepared and calcined polymeric intermediate. The phase of the synthesized LiMn 2 O 4 powder was confirmed by comparing the obtained XRD patterns with the JCPDS standard. CV and battery cyclic studies showed that the better electrochemical activity for LiMn 2 O 4 compound, prepared at 750°C, with a discharge capacity of about 110 mAh g − 1 .