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BaAl12O19:Tb, Dy phosphor was prepared by the sol-gel technique using citric acid as a complextant. XRD was used to characterize the relevant crystallization behavior of the phosphor. The luminescence properties and energy transfer between Tb3+ and Dy3+ were investigated. The results revealed that energy transfer exists between Dy3+ and Tb3+ at appropriate Tb3+ concentrations. The emission intensity of Tb3+ increases and energy transfer happens from Dy3+ to Tb3+ ions at the higher content of Tb3+ when Tb3+ and Dy3+ ions were co-doped. BaAl12O19 phosphors doped with Tb3+ or Dy3+ ions only were studied to compared with BaAl12O19:Tb, Dy phosphors. The results showed that the maximum excitation peak of BaAl12O19:Tb is 240 nm and the emission spectrum consists of four peaks at 490, 545, 590, and 625 nm, originating from 5D4 --> 7FJ (J = 6, 5, 4, 3) transitions of Tb3+ ion, respectively. The excitation peaks of BaAl12O19:Dy are at 291, 324 nm and the emissions of Dy3+ are at 370, 447 and 578 nm, originating from 4F9/2 --> 6P5/2, 4F9/2 --> 6H15/2 and 4F9/2 --> 6H13/2 transitions of Dy3+ ion, respectively.

Abstract: A micro-sized particle Li4Ti5−x La x O12 (0 ≤ x ≤ 0.2) material has been synthesized by a simple solid-state method at air. The obtained Li4Ti5−x La x O12 materials are Li3x La2/3−x TiO3 (LLTO)–Li4Ti5O12 (LTO) solid solution, and well crystallized with a particle size in the range of 1–2 μm. The electronic conductivity and lithium diffusion coefficient of La-modified LTO (Li4Ti4.95La0.05O12) are improved because LLTO exhibits a high ionic conductivity during Li+ extraction. Li4Ti4.95La0.05O12 material shows discharge capacities of more than 206 and 197 mAh g−1 after 100 cycles at 1 C and 3 C charge–discharge rates, respectively. Especially, in rate performance, the Li4Ti5−x La x O12 (x = 0.1, 0.2) samples maintain capacity of about 181 mAh g−1 until 5 C rates after 200 cycles, while the pure LTO sample shows a severe capacity decline at corresponding rate. These results suggest that La modifying is an effective way to improve the chemical stability of the electrode in contact with the electrolyte and improve their cyclability and rate capability during long term cycling. Since high rate performance is an important factor that needs to be considered in fabricating power batteries in industry, the La-modified LTO moves closer to real and large-scale applications. [Copyright &y& Elsevier]

Well-crystallized and high-performance x Li 2 MnO 3 ·(1- x )LiMn 1/3 Co 1/3 Ni 1/3 O 2 cathode materials over a wide compositional range (0.1 ≤ x ≤ 0.5) were prepared by a facile co-precipitation strategy. All samples show small and uniform particle dimensions in the range of 200-500 nm. 0.3Li 2 MnO 3 ·0.7LiMn 1/3 Co 1/3 Ni 1/3 O 2 (LMNC3) delivers the highest discharge capacities of 321.1 mA h g −1 at 0.1C, 305.2 mA h g −1 at 0.2 C, 243.2 mA h g −1 at 0.5C, 205.9 mA h g −1 at 1C, 182.1 mA h g −1 at 2C, and 133.7 mA h g −1 at 5C, respectively. LMNC3 also exhibits an excellent fast charge-discharge performance, and even at a charge-discharge rate of 2C in the 100th cycle its capacity still remains 128.2 mAh g −1 . The improved performance of LMNC3 can be ascribed to the improvement of electrochemical reversibility, lithium ion diffusion and ionic conductivity. First-principles calculation based on density function theory reveals that the strong covalent bonds formed between Mn-3d and O-2p orbits and stable Li 2 MnO 3 -enriched layer are helpful for stabilizing the LiMn 1/3 Co 1/3 Ni 1/3 O 2 structure. The same strategy adopted in this work could be helpful to develop other Li-rich cathodes with long cycle life and high rate performance. [ABSTRACT FROM AUTHOR]

Abstract: Microscale Li4Ti5−x Zn x O12 (0 ≤ x ≤ 0.2) particles with high phase purity were synthesized by a simple solid-state reaction. The effect of the zinc doping on the physicochemical properties of Li4Ti5O12 (LTO) was extensively studied by TG-DSC, XRD, Raman spectroscopy, SEM, CV, EIS, and galvanostatic charge–discharge testing. The crystallization of lithium titanate oxide forms at about 750 °C. The lattice parameter of the Zn-doped LTO samples is slightly smaller than that for the pure LTO samples, and zinc doping does not change the basic Li4Ti5O12 structure. Even though the material has a particle size of 1–2 μm, Zn-doped LTO shows very high excellent capacity retention between 0 and 2.5 V. Especially, in rate performance, the Li4Ti4.8Zn0.2O12 sample maintains capacity of about 180 mAh g−1 until 5 C rates after 200 cycles, while the pure LTO sample shows severe capacity decline at corresponding rates. The reason for the high rate performance of Zn-doped LTO anode is ascertained to the diffusion coefficient (D Li) and reversible intercalation and deintercalation of lithium ion. The superior cycling performance and wide discharge voltage range, as well as simple synthesis route and low synthesis cost of the Zn-doped LTO are expected to show a potential commercial application. [Copyright &y& Elsevier]