H.X. Yang

Combustion synthesis and photoluminescence of SrAl2O4:Eu,Dy phosphor nanoparticles

Abstract Eu2+,Dy3+ co-doped strontium aluminate (SrAl2O4) phosphor nanoparticles with high brightness and long afterglow were prepared by glycine–nitrate solution combustion synthesis at 500 °C, followed by heating the resultant combustion ash at 1100 °C in a weak reductive atmosphere of active carbon. The average particle size of the SrAl2O4:Eu,Dy phosphor nanoparticles ranges from 15 to 45 nm as indicated by transmission electron microscopy (TEM). The broad-band UV-excited luminescence of the SrAl2O4:Eu,Dy phosphor nanoparticles was observed at λmax=513 nm due to transitions from the 4f65d1 to the 4f7 configuration of the Eu2+ ion. The results indicated that the main peaks in the emission and excitation spectrum of phosphor nanoparticles shifted to the short wavelength compared with the phosphor obtained by the solid-state reaction synthesis method. The decay speed of the afterglow for phosphor nanoparticles was faster than that obtained by the solid-state reaction method.

Preparation and characterization of LiNiO2 synthesized from Ni(OH)2 and LiOH·H2O

Synthesis of LiNiO2 by heat-treatment of Li(OH)·H2O and Ni(OH)2 is reported. The influence of synthesis conditions on the electrochemical performance of the resulting LiNiO2 is investigated. Thermal analysis of the synthesis process shows that LiNiO2 formation proceeds through the transformation of Ni(OH)2 to a layered compound Ni1−x(OH)2−x, followed by solid reaction with LiOH. The most favorable condition is heating a mixture of Li(OH)·H2O and Ni(OH)2 at 650°C, and then at 720°C in oxygen. The resulting LiNiO2 exhibits a considerably high discharge capacity of 145 mA h g−1 and a sufficiently long cycle-life when cycled over a lithium composition range of 0.2≤x≤0.65.

Metal Borides: Competitive High Capacity Anode Materials for Aqueous Primary Batteries

Experimental results indicated that transition metal borides VB 2 and TiB 2 electrodes can deliver exceptionally high discharge capacity of over 3100 and 1600 mAh/g, respectively, corresponding to an 11 and 6 electron oxidation reaction, although their parent elements V, Ti, and boron, are almost completely electrochemically inert. The reasons for the observed extraordinary capacities of diborides are probably due to the electrochemical activation of boron, which alleviates the passivation of the transition metal by clamping the electrode potential to a less positive range of potential.

A study of LiMn2O4 synthesized from Li2CO3 and MnCO3

Abstract Spinel LiMn2O4 samples are prepared by heating a Li2CO3/MnCO3 mixture in air at various temperatures, and their structure and chemical performance are studied by using thermal analysis, X-ray diffraction, microelectrode voltammetry, and charge–discharge measurements. It was found that the electrochemical properties of the LiMn2O4 samples are very sensitive to the synthesis temperature. The LiMn2O4 powder obtained at 800°C yields a high initial capacity of ∼115 mAh g−1, excellent cyclability, and has a good high-rate capability.

Polypyridine complexes of iron used as redox shuttles for overcharge protection of secondary lithium batteries

Abstract The 2,2′-bipyridyl and 1,10-phenanthroline complexes of iron, which show oxidation potential ∼0.7 V more positive than that of ferrocene, were studied for their possible use as redox shuttles for the overcharge protection of secondary lithium batteries. The shuttle voltage was found to be around 3.8–3.9 V. The electrochemical stability of these complexes at the electrodes of lithium batteries was also investigated.

Recent advances in experimental methods applied to lithium battery researches

Abstract Sealed minicells for microelectrode and spectroelectrochemical investigation of liquid cathode depolarizers of lithium batteries were developed. The applicability of these technique is illustrated with the results of the Li/SOCl2 and Li/SO2Cl2 systems studies using these techniques.