Despite their high theoretical capacity and energy density,lithiumsulfur(Li–S)batteries still face challenges such as soluble lithium polysulfides(LiPSs)shuttling and sluggish redox kinetics.In this work,we used a no...Despite their high theoretical capacity and energy density,lithiumsulfur(Li–S)batteries still face challenges such as soluble lithium polysulfides(LiPSs)shuttling and sluggish redox kinetics.In this work,we used a novel MoS_(2)-Mo_(2)C heterostructure anchored on a carbon sponge(CS)as a Li_(2)S host to solve these problems.A simple hydrothermal process following carbothermal reduction was used to construct the MoS_(2)-Mo_(2)C heterostructure,enabling control of the phases and integration of MoS_(2) and Mo_(2)C.Structural characterization confirmed the coherent interface of the heterostructure with a precise orientation relationship between the two phases and their uniform distribution.An evaluation of the adsorption and catalytic performance of the material showed that it has an exceptional LiPSs adsorption capacity with faster conversion from Li_(2)S_(4) to Li_(2)S_(2).Density functional theory calculations further confirmed these results.As a result,the cathode had a high initial discharge capacity of 693 mAh g^(−1) at 0.2 C and achieved stable cycling at 2 C for 500 cycles with a low decay rate of 0.107%per cycle.The heterostructure design,coupled with the macroporous CS framework,effectively prevented the shuttling and increased sulfur utilization,offering a promising way to produce practical high-energydensity Li–S batteries.展开更多
The BaGd（2-2 x）Eu（2 x）O4（BG, x = 0.01-0.09） phosphors were successfully synthesized via the sol-gel method,and BaY（2-2 y）Eu（2 y）O4（BY, y = 0.005-0.07） phosphors were included for comparison. The pure phase...The BaGd（2-2 x）Eu（2 x）O4（BG, x = 0.01-0.09） phosphors were successfully synthesized via the sol-gel method,and BaY（2-2 y）Eu（2 y）O4（BY, y = 0.005-0.07） phosphors were included for comparison. The pure phase BG phosphors with the ordered CaFe2 O4-type structure are obtained by annealing at 1300℃ for5 h. The phosphors with uniform particle size of 120 nm and good dispersion display typical Eu^3＋emission with the strongest peak at 613 nm（^5 D0→^7 F2 transition of Eu3＋） under optimal excitation band at 262 nm（CTB band）. The presence of Gd^3＋ excitation bands on the PLE spectra monitoring the Eu3＋emission directly proves an evidence of Gd^3＋-Eu^3＋ energy transfer. Owing to the concentration quenching, the optimum content of Eu3＋ addition is 5 at%（x = 0.05）, and the quenching mechanism is determined to be the exchange reaction between Eu3＋. All the BG samples have similar color coordinates and temperature of（0.64 ± 0.02, 0.36 ± 0.01） and 2000 ± 100 K,respectively. The lifetime value of BaGd（1.9）Eu（0.1）O4 for 613 nm is fitted to be 2.19 ± 0.01 ms, and the Eu^3＋ concentration does not change the lifetime significantly. Owing to the Gd^3＋-Eu^3＋ energy transfer, the luminescent intensity of the BaGd（1.9）Eu（0.1）O4 phosphor is better than BY system. The BG system served as a new type of phosphor is expected to be widely used in lighting and display areas.展开更多
文摘Despite their high theoretical capacity and energy density,lithiumsulfur(Li–S)batteries still face challenges such as soluble lithium polysulfides(LiPSs)shuttling and sluggish redox kinetics.In this work,we used a novel MoS_(2)-Mo_(2)C heterostructure anchored on a carbon sponge(CS)as a Li_(2)S host to solve these problems.A simple hydrothermal process following carbothermal reduction was used to construct the MoS_(2)-Mo_(2)C heterostructure,enabling control of the phases and integration of MoS_(2) and Mo_(2)C.Structural characterization confirmed the coherent interface of the heterostructure with a precise orientation relationship between the two phases and their uniform distribution.An evaluation of the adsorption and catalytic performance of the material showed that it has an exceptional LiPSs adsorption capacity with faster conversion from Li_(2)S_(4) to Li_(2)S_(2).Density functional theory calculations further confirmed these results.As a result,the cathode had a high initial discharge capacity of 693 mAh g^(−1) at 0.2 C and achieved stable cycling at 2 C for 500 cycles with a low decay rate of 0.107%per cycle.The heterostructure design,coupled with the macroporous CS framework,effectively prevented the shuttling and increased sulfur utilization,offering a promising way to produce practical high-energydensity Li–S batteries.
基金Project supported by the National Natural Science Foundation of China(51402125)China Postdoctoral Science Foundation(2017M612175)+3 种基金the Special Fund for the Postdoctoral Innovation Project in Shandong Province(201603061)the Research Fund for the Doctoral Program of University of Jinan(XBS1447)the Natural Science Foundation of University of Jinan(XKY1515)the Science Foundation for Post Doctorate Research from the University of Jinan(XBH1607)
文摘The BaGd（2-2 x）Eu（2 x）O4（BG, x = 0.01-0.09） phosphors were successfully synthesized via the sol-gel method,and BaY（2-2 y）Eu（2 y）O4（BY, y = 0.005-0.07） phosphors were included for comparison. The pure phase BG phosphors with the ordered CaFe2 O4-type structure are obtained by annealing at 1300℃ for5 h. The phosphors with uniform particle size of 120 nm and good dispersion display typical Eu^3＋emission with the strongest peak at 613 nm（^5 D0→^7 F2 transition of Eu3＋） under optimal excitation band at 262 nm（CTB band）. The presence of Gd^3＋ excitation bands on the PLE spectra monitoring the Eu3＋emission directly proves an evidence of Gd^3＋-Eu^3＋ energy transfer. Owing to the concentration quenching, the optimum content of Eu3＋ addition is 5 at%（x = 0.05）, and the quenching mechanism is determined to be the exchange reaction between Eu3＋. All the BG samples have similar color coordinates and temperature of（0.64 ± 0.02, 0.36 ± 0.01） and 2000 ± 100 K,respectively. The lifetime value of BaGd（1.9）Eu（0.1）O4 for 613 nm is fitted to be 2.19 ± 0.01 ms, and the Eu^3＋ concentration does not change the lifetime significantly. Owing to the Gd^3＋-Eu^3＋ energy transfer, the luminescent intensity of the BaGd（1.9）Eu（0.1）O4 phosphor is better than BY system. The BG system served as a new type of phosphor is expected to be widely used in lighting and display areas.
