Lithium sulfur batteries are one of the most promising alternative electrochemical systems,but their practical applications are largely hindered by the serious shuttling problems and sluggish redox kinetics.Here,the c...Lithium sulfur batteries are one of the most promising alternative electrochemical systems,but their practical applications are largely hindered by the serious shuttling problems and sluggish redox kinetics.Here,the conductive and polar niobium nitride(NbN)is in-situ introduced onto graphene with ultrasmall size and high dispersion,and their composite is used to construct an efficient lithium polysulfide blocking layer.The graphene helps to construct highly conductive pathways,and niobium nitride serves as the sulfiphilic sites to chemically adsorb the migrating lithium polysulfides and catalyze their redox conversion.Hence,the cells with the Nb N/G interlayers exhibit a long cycle life with a lower capacity decay of 0.096%/cycle at 1 C for 300 cycles and high rate capability of 937 m Ah g^-1 at 2 C.Further coupling with a sulfur/carbon nanofiber electrode,the cell with an ultra-high sulfur loading of 10.8 mg cm^-2 delivers an areal capacity of 12.5 m Ah cm^-2 at 0.1 C.展开更多
Effects of deposition angle and axial distance on the structural and mechanical properties of niobium nitride syn- thesized by a dense plasma focus （DPF） system are studied. The x-ray diffraction （XRD） confirms th...Effects of deposition angle and axial distance on the structural and mechanical properties of niobium nitride syn- thesized by a dense plasma focus （DPF） system are studied. The x-ray diffraction （XRD） confirms that the deposition parameters affect the growth of multi-phase niobium nitride. Scanning electron microscopy （SEM） shows the granular surface morphology with strong thermally assisted coagulation effects observed at the 5-cm axial distance. The non-porous granular morphology observed at the 9-cm distance along the anode axis is different from those observed at deposition angles of 10° and 20°. Energy dispersive x-ray （EDX） spectroscopy reveals the maximum nitrogen content at the shortest （5 cm） axial position. Atomic force microscopy （AFM） exhibits that the roughness of coated films varies for coatings synthesized at different axial and angular positions, and the Vickers micro-hardness test shows that a maximum hardness value is （08.44 ±0.01） GPa for niobium nitride synthesized at 5-cm axial distance, which is about 500% more than that of a virgin sample.展开更多
Superconducting nanowire single-photon detectors(SNSPDs) have attracted considerable attention owing to their excellent detection performance;however, the underlying physics of the detection process is still unclear.I...Superconducting nanowire single-photon detectors(SNSPDs) have attracted considerable attention owing to their excellent detection performance;however, the underlying physics of the detection process is still unclear.In this study, we investigate the wavelength dependence of the intrinsic detection efficiency(IDE) for NbN SNSPDs.We fabricate various NbN SNSPDs with linewidths ranging from 30 nm to 140 nm.Then, for each detector, the IDE curves as a function of bias current for different incident photon wavelengths of 510–1700 nm are obtained.From the IDE curves, the relations between photon energy and bias current at a certain IDE are extracted.The results exhibit clear nonlinear energy–current relations for the NbN detectors, indicating that a detection model only considering quasiparticle diffusion is unsuitable for the meander-type NbN-based SNSPDs.Our work provides additional experimental data on SNSPD detection mechanism and may serve as an interesting reference for further investigation.展开更多
基金financial support from the National Key R&D Program of China(2016YFB0100100 and 2016YFA0200100)the National Natural Science Foundation of China(Nos.51972313,51525206 and 51521091)+1 种基金the Strategic Priority Research Program of Chinese Academy of Science(XDA22010602)China Petrochemical Cooperation(No.218025)。
文摘Lithium sulfur batteries are one of the most promising alternative electrochemical systems,but their practical applications are largely hindered by the serious shuttling problems and sluggish redox kinetics.Here,the conductive and polar niobium nitride(NbN)is in-situ introduced onto graphene with ultrasmall size and high dispersion,and their composite is used to construct an efficient lithium polysulfide blocking layer.The graphene helps to construct highly conductive pathways,and niobium nitride serves as the sulfiphilic sites to chemically adsorb the migrating lithium polysulfides and catalyze their redox conversion.Hence,the cells with the Nb N/G interlayers exhibit a long cycle life with a lower capacity decay of 0.096%/cycle at 1 C for 300 cycles and high rate capability of 937 m Ah g^-1 at 2 C.Further coupling with a sulfur/carbon nanofiber electrode,the cell with an ultra-high sulfur loading of 10.8 mg cm^-2 delivers an areal capacity of 12.5 m Ah cm^-2 at 0.1 C.
文摘Effects of deposition angle and axial distance on the structural and mechanical properties of niobium nitride syn- thesized by a dense plasma focus （DPF） system are studied. The x-ray diffraction （XRD） confirms that the deposition parameters affect the growth of multi-phase niobium nitride. Scanning electron microscopy （SEM） shows the granular surface morphology with strong thermally assisted coagulation effects observed at the 5-cm axial distance. The non-porous granular morphology observed at the 9-cm distance along the anode axis is different from those observed at deposition angles of 10° and 20°. Energy dispersive x-ray （EDX） spectroscopy reveals the maximum nitrogen content at the shortest （5 cm） axial position. Atomic force microscopy （AFM） exhibits that the roughness of coated films varies for coatings synthesized at different axial and angular positions, and the Vickers micro-hardness test shows that a maximum hardness value is （08.44 ±0.01） GPa for niobium nitride synthesized at 5-cm axial distance, which is about 500% more than that of a virgin sample.
基金Project supported by the National Key R&D Program of China(Grant No.2017YFA0304000)the National Natural Science Foundation of China(Grant Nos.61671438 and 61827823)+2 种基金the Science and Technology Commission of Shanghai Municipality,China(Grant No.16JC1400402)Program of Shanghai Academic/Technology Research Leader,China(Grant No.18XD1404600)the Joint Research Fund in Astronomy(Grant No.U1631240)under Cooperative Agreement between the NSFC and the Chinese Academy of Sciences
文摘Superconducting nanowire single-photon detectors(SNSPDs) have attracted considerable attention owing to their excellent detection performance;however, the underlying physics of the detection process is still unclear.In this study, we investigate the wavelength dependence of the intrinsic detection efficiency(IDE) for NbN SNSPDs.We fabricate various NbN SNSPDs with linewidths ranging from 30 nm to 140 nm.Then, for each detector, the IDE curves as a function of bias current for different incident photon wavelengths of 510–1700 nm are obtained.From the IDE curves, the relations between photon energy and bias current at a certain IDE are extracted.The results exhibit clear nonlinear energy–current relations for the NbN detectors, indicating that a detection model only considering quasiparticle diffusion is unsuitable for the meander-type NbN-based SNSPDs.Our work provides additional experimental data on SNSPD detection mechanism and may serve as an interesting reference for further investigation.
