Papers by Keyword: LiMn₂O₄

Abstract: Spinel LiMn₂O₄ is one of the promising cathode materials used in commercial Li-ion batteries. In this study, Ni was partially substituted in order to give the material LiMn_1.8Ni_0.2O₄, which was successfully synthesized using a self-propagating combustion (SPC) method. Results from Simultaneous Thermogravimetric Analysis (STA) show the small mass loss about 4.6%. The precursor then was calcined at temperature of 800 °C for 24 h, 48 h and 72 h. X-Ray Diffraction (XRD) confirms that the final products are pure and single phase with no impurities present. The morphology and crystallite size of pure samples are examined using Field Emission Scanning Electron Microscope (FESEM). The result shows that all the materials consist of crystalline particles with smooth surface and polyhedral shaped materials.

Abstract: Wet recycling method was utilized for recycling manganese from waste Zn-Mn batteries to obtain MnCO₃. It was indicated that soaking time, the concentration and volume of acid all have great effects on the yield of MnCO₃. The productivity of MnCO₃ can reach 64.65%, when the concentration of HCl acid is 5mol/L, and with a volume of 40ml, under 180min soaking time. The productivity of MnCO₃ can also reach 63.36%, when the concentration of HNO₃ is 6mol/L, with 60ml volume by soaking for 80min. Furthermore, LiMn₂O₄ was synthesized in air atmosphere with the recycled MnCO₃ and Li₂CO₃ under different calcination temperatures. The electrochemical performances of prepared LiMn₂O₄ were studied and the results present preferable electrochemical properties.

Abstract: The blend cathode materials LiMn₂O₄/Li_1.2(Mn_0.56Ni_0.16Co_0.08)O₂ have been successfully prepared by the physical mixing of commercial Li₂MnO₄ and self-prepared Li_1.2(Mn_0.56Ni_0.16Co_0.08)O₂ nanoparticles. The structures, morphologies and electrochemical performances are characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), Cyclic Voltammetry (CV) and charge-discharge test, and the results show that the good mass ratio of Li₂MnO₄ and Li_1.2(Mn_0.56Ni_0.16Co_0.08)O₂ is 50:50. Therein, the nanosized Li_1.2Ni_0.16Co_0.08Mn_0.56O₂ uniformly adhere on the surface of Li₂MnO₄ micro structure, and occupy the gap of Li₂MnO₄ particles, which can effectively elevate the tap density of Li_1.2(Mn_0.56Ni_0.16Co_0.08)O₂ nanoparticles. As lithium ion battery cathode, the 50:50 sample reveals an initial discharge capacity of 265.4 mAh/g with negligible irreversible capacity loss at current density of 0.1C within 2.0-4.8 V, and retain 89.2% after 20 cycles.

Abstract: This study aims at investigating a better condition of calcination at different temperature to produce LiMn₂O₄ microstructure. In this study, cubic LiMn₂O₄ was synthesized using a low temperature solid-state reaction. We report, here, MnO₂ nanorods synthesis by reflux and their chemical conversion to LiMn₂O₄. The compound was characterized by XRD and TEM. Further, the analysis of LiMn₂O₄ microstructure was carried out by Direct Method using winPLOTR package program and Diamond using XRD data. At low calcination temperature, Mn₂O₃ is present as an impurity, but it disappears along with the increase in calcination temperature. It is also found that solid state reaction at is 750^oC give nanoLiMn₂O₄. The lattice parameters and cell volumes of LiMn₂O₄ increases with the increase in heating temperature.

Abstract: The surface morphology and structure of the cubic stoichiometric spinel LiMn₂O₄ powder prepared by microwave heating were examined using X-ray diffraction, scanning electron microscopy and transmittance electron microcopy. It is shown that the surface morphology of LiMn₂O₄ particle changed with increasing preparing temperature, while the crystal structure kept unchanged. Novel nanostructured morphologies including nanorods and nanowhiskers were formed under appropriate synthesis conditions. The growth mechanism of the nanostructured morphology of spinel LiMn₂O₄ was discussed in accordance with period bonding chains (PBCs) theory.

Abstract: LiMn₂O₄ was synthesized by flameless solution combustion at 600°C for 3 hours (h). The influence of HNO₃ on the morphologies, crystal structure and electrochemical performances of the material was investigated. The results show that the main phase of all synthesized products is LiMn₂O₄, and the impurities are Mn₂O₃ or Mn₃O₄ depending on the concentration of HNO₃ (C_HNO3). While C_HNO3=0 and 15 mol L^-1, the impurity was Mn₂O₃, when the concentrations of HNO₃ from 3 to 9 mol L^-1, the impurity was Mn₃O₄; at C_HNO3=12 mol L^-1, the synthesized product was single phase; C_HNO3≤12 mol L^-1, with the increase of C_HNO3, particles size grew from 70-130 nm to 140-500 nm, however, C_HNO3 is up to 15 mol L^-1, particles become small (70-140 nm); the single phase of LiMn₂O₄ obtained the maximum first discharge capacity (119.7 mAh g^-1) at C_HNO3=12 mol L^-1, but its retention rate was undesirable, while C_HNO3=15 mol L^-1, the cycling performance of the product was the optimum with first discharge capacity of 118.5 mAh g^-1 and capacity retention of 90.9 % after 40 cycles at 0.2 C.

Abstract: LiMn₂O₄ and LiNi_0.5-xCr_2xMn_1.5-xO₄(x=0, 0.05) cathode materials of spinel structure were prepared via co-precipitation derived precursors and subsequent high-temperature sintering between the precursors and LiOH. XRD, SEM and electrochemical tests were performed for the characterization of the as-prepared samples. The results show that the substitutions of Ni and Cr for Mn can not prevent Mn²⁺from being oxidized into Mn³⁺ in solution process, yet do not change their final crystal structures of spinel with or without substitution, and after substitution the first charge and discharge capacities decrease but its cyclic capability is improved significantly, especially for the Ni and Cr co-substitution

Abstract: In this experiment, the spinel-type lithium manganese oxide (LiMn₂O₄) prepared via solid-phase sintering method was coated with magnesium titanium composite oxide (MgTiO_x) in the presence of polyvinyl pyrrolidone (PVP) under the ultrasonic wave. The crystal structures, surface morphologies and electrochemical properties of the sample prepared were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical analysis. The X-ray diffractions indicated that the LiMn₂O₄ coated with MgTiO_x were similar to that of the pure LiMn₂O_4, and they both showed sharp and high peaks. The particles of the samples prepared with PVP did not aggregate obviously, and the samples were coated completely and homogeneously. At charge-discharge rates of 0.2C, the first discharge capacity can reach more than 120 mAh / g. Compared with pure LiMn₂O₄, the capacity attenuation of MgTiO_x-coated LiMn₂O₄ reduced after fifty cycles, and showed good electrochemical performance.

Abstract: Spinel LiMn2O4 was prepared by solid state reaction from composite carbonate precursors Li2CO3 and MnCO3, which were obtained by coprecipitation method. The physicochemical properties of spinel LiMn₂O₄ and its precursor were investigated by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffraction (XRD), scanning electron micrographs (SEM) and galvanostatic charge-discharge test, respectively. The carbonate precursors demonstrate the porous spherical flower-like morphology, and spinel LiMn₂O₄ shows the rod or rod clusters-like one with different particle sizes. The spinel LiMn₂O₄ prepared from composite carbonate precursors delivers an initial discharge capacity of 115 mAh/g with excellent capacity retention, indicating an attractive application in the high-power lithium-ion batteries.

Abstract: LiMn₂O_4-yF_y were synthesized by a novel method named liquid phase flameless combustion reaction with LiNO₃, MnAc₂.4H₂O and LiF as raw materials calcined at 600 °C for 3 h with HNO₃ as aided oxidant. All samples were investigated by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) and electrochemical performance. The results show that: all samples have main phase of LiMn₂O₄ with impurity of Mn₃O₄ and the vibrational bands of Mn-O are a little red shift by doping F, which indicated that the F- enter the host structure of LiMn₂O₄ successfully. The electrochemical performance show that the initial discharge capacities of F-doped samples are lower than pristine LiMn₂O₄, which is 117.7 mAh•g^-1. However, the capacity retention of LiMn₂O_3.96F_0.04 and LiMn₂O_3.90F_0.10 are 73.6% and 74.5%, respectively, which are higher than pristine LiMn₂O₄, which is only 69.0% after 40 cycles.