Commercial cathode material （LiCoO2） was modified by coating with a thin layer of SrO/Li2O/La2O3/Ta2O5/TiO2 for improving its performance in lithium ion battery. The morphology and structure of the modified cathode ...Commercial cathode material （LiCoO2） was modified by coating with a thin layer of SrO/Li2O/La2O3/Ta2O5/TiO2 for improving its performance in lithium ion battery. The morphology and structure of the modified cathode material were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The performance including cycling stability, diffusion coefficient under different voltage, C-rate discharge of the batteries with this modified cathode material was examined. The results showed that the battery with the coated cathode material could discharge at a large current density, and it possessed a stable cycle performance in the range from 3.0 V to 4.2 V. It was explained that the rate of Li ion diffusion increased in the batteries using SrO/Li2O/La2O3/Ta2O5/TiO2-coated LiCoO2 as the cathode and the coated layer could act as a fast ion conductor （SrO/Li2O/La2O3/Ta2O5/TiO2） and as a protecting shell to prevent LiCoO2particles from being attacked by the acidic electrolyte.展开更多
Ho^（3＋） doped La_（2（1-x））Yb_（2x）TiO_5 samples were prepared by sol-gel method. Pyrochlore structured powders were obtained under the annealing of the as-prepared samples at 1100 °C for 3 h in the air. Al...Ho^（3＋） doped La_（2（1-x））Yb_（2x）TiO_5 samples were prepared by sol-gel method. Pyrochlore structured powders were obtained under the annealing of the as-prepared samples at 1100 °C for 3 h in the air. All the samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and photoluminescent spectroscopy. When x=0, we obtained La_2TiO_5 phosphors. Monitored at 546 nm, the excitation spectrum of Ho^（3＋） activated La_2TiO_5 phosphors consisted of a broad band originating from the charge-transfer band（CTB） between Ho^（3＋） ions and the nearest neighboring O^（2-） ions at 250-280 nm and four sharp bands associated to f-f transitions of Ho^（3＋） ions at 350-500 nm. Under the blue light excitation at 461 nm, Ho^（3＋） ion in La_2TiO_5 emitted an intense green emission band at 546 nm due to the transition of ~5S_2, ~5F_4→~5I_8. Two intense bands were observed at 490 nm（blue, ~5F_3→I_8） and 663 nm（red, ~5F_5→~5I_8） in the up-conversion（UC） spectrum under 980 nm NIR laser excitation in La_2TiO_5 phosphors activated with Ho^（3＋） alone, whereas they were much different from the down-conversion（DC） luminescent samples. When x=7.5 mol.%-17.5 mol.%, the UC emission spectra of them dominated at 546 nm（green, ~5S_2, ~5F_4→~5I_8） and enhanced significantly with the dose of Yb^（3＋） ion. The decay curve also confirmed that the transitions of ~5F_4→~5I_8 and ~5S_2→~5I_8 were merged into one emission band at 546 nm.展开更多
基金supported by the Natural Science Foundation of Guangdong Province,China (06105562)the Foundation of Manyang Bureau of Sci-ence and Technology,China (07Y003-1)
文摘Commercial cathode material （LiCoO2） was modified by coating with a thin layer of SrO/Li2O/La2O3/Ta2O5/TiO2 for improving its performance in lithium ion battery. The morphology and structure of the modified cathode material were characterized by scanning electron microscopy （SEM） and X-ray diffraction （XRD）. The performance including cycling stability, diffusion coefficient under different voltage, C-rate discharge of the batteries with this modified cathode material was examined. The results showed that the battery with the coated cathode material could discharge at a large current density, and it possessed a stable cycle performance in the range from 3.0 V to 4.2 V. It was explained that the rate of Li ion diffusion increased in the batteries using SrO/Li2O/La2O3/Ta2O5/TiO2-coated LiCoO2 as the cathode and the coated layer could act as a fast ion conductor （SrO/Li2O/La2O3/Ta2O5/TiO2） and as a protecting shell to prevent LiCoO2particles from being attacked by the acidic electrolyte.
基金supported by the National Natural Science Foundation of China(51401130)the Natural Science Foundation of Liaoning Province(2014028015)Fundamental Research Foundation of Central Universities(N142304007)
文摘Ho^（3＋） doped La_（2（1-x））Yb_（2x）TiO_5 samples were prepared by sol-gel method. Pyrochlore structured powders were obtained under the annealing of the as-prepared samples at 1100 °C for 3 h in the air. All the samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM） and photoluminescent spectroscopy. When x=0, we obtained La_2TiO_5 phosphors. Monitored at 546 nm, the excitation spectrum of Ho^（3＋） activated La_2TiO_5 phosphors consisted of a broad band originating from the charge-transfer band（CTB） between Ho^（3＋） ions and the nearest neighboring O^（2-） ions at 250-280 nm and four sharp bands associated to f-f transitions of Ho^（3＋） ions at 350-500 nm. Under the blue light excitation at 461 nm, Ho^（3＋） ion in La_2TiO_5 emitted an intense green emission band at 546 nm due to the transition of ~5S_2, ~5F_4→~5I_8. Two intense bands were observed at 490 nm（blue, ~5F_3→I_8） and 663 nm（red, ~5F_5→~5I_8） in the up-conversion（UC） spectrum under 980 nm NIR laser excitation in La_2TiO_5 phosphors activated with Ho^（3＋） alone, whereas they were much different from the down-conversion（DC） luminescent samples. When x=7.5 mol.%-17.5 mol.%, the UC emission spectra of them dominated at 546 nm（green, ~5S_2, ~5F_4→~5I_8） and enhanced significantly with the dose of Yb^（3＋） ion. The decay curve also confirmed that the transitions of ~5F_4→~5I_8 and ~5S_2→~5I_8 were merged into one emission band at 546 nm.
