Fabrication of Nb2O5 Nanosheets for High-rate Lithium Ion Storage Applications

Nb2O5 nanosheets are successfully synthesized through a facile hydrothermal reaction and followed heating treatment in air. The structural characterization reveals that the thickness of these sheets is around 50 nm and the length of sheets is 500 similar to 800 nm. Such a unique two dimensional structure enables the nanosheet electrode with superior performance during the charge-discharge process, such as high specific capacity (similar to 184 mAh.g(-1)) and rate capability. Even at a current density of 1 A.g(-1), the nanosheet electrode still exhibits a specific capacity of similar to 90 mAh.g(-1). These results suggest the Nb2O5 nanosheet is a promising candidate for high-rate lithium ion storage applications

Intrinsic factors attenuate the performance of anhydride organic cathode materials of lithium battery

Anhydride organic materials are promising candidates for lithium batteries on account of reversible insertion and de-insertion of Li+ on the conjugated carbonyl structure. However, anhydride compounds suffer from drawbacks that rapidly attenuate the capacity of lithium batteries. This study aims to reveal the essential reason for the rapid capacity attenuation of four anhydride organic compounds by characterizing the morphological features of the lithium foil surface and the loss of active materials before and after charge-discharge cycles, to speculate the reasons for the electrochemical property attenuation along with molecular weight decreases. This study proposes that the phenomenon is because the anhydride monomer react Li+ during the charge and discharge processes, then cross the separator and deposits on the surface of lithium foil (Li-foil), leading to loss of active materials and low utilization of the Li-foil. Based on the mechanism study, anhydride compounds will face the new development in the field of energy storage. (C) 2016 Elsevier B.V. All rights reserved

Synthesis of V2O5 hierarchical structures for long cycle-life lithium-ion storage

A facile solvothermal method was used to synthesize V2O5 nanosheet hierarchical structures. Using different solvent systems, we obtained the hierarchical structures with different nanosheet thicknesses of <10 nm, 50-100 nm and 100-200 nm, respectively. A systematic investigation of their electrochemical properties showed that both the reversible lithium storage capacity and the cycling stability increased with the reduced thickness of nanosheets. In order to prevent the serious structural damage of the V2O5 electrodes during cycling, we employed a voltage-regulation charge/discharge scheme which led to a long cycle-life with an average capacity decay of 0.04% (2.0 to 3.0 V) and 0.10% per cycle (2.8 to 4.0 V) over 500 cycles

Selenium-Doped Black Phosphorus for High-Responsivity 2D Photodetectors

Department of Applied Physic

A high energy density Li2S@C nanocomposite cathode with a nitrogen-doped carbon nanotube top current collector

Lithium sulfide (Li2S), with a high theoretical capacity of 1166 mA h g(-1), is considered as one of the most promising cathode materials for the next-generation lithium-ion batteries. In this work, a novel cell configuration with a top current collector was designed for Li2S based batteries. The nitrogen-doped carbon nanotube (N-CNT) film was applied on top of the cathode, which serves not only as a top current collector but also as a barrier layer to effectively impede the polysulfide diffusion and enhance the utilization of active materials. A sheet-like Li2S@C nanocomposite was synthesized from low-cost and environmentally friendly raw materials of lithium sulfate (Li2SO4) and activated graphite. The as-prepared Li2S@C composites were directly used as cathode materials without adding any binder or carbon additive, which enabled a high Li2S loading up to 68% in the total cathode weight. The cells exhibited superior electrochemical performance. The specific energy at 0.5C was 804 W h kg(-1) based on the total electrode weight including the N-CNT top current collector, which is among the highest values demonstrated so far for sulfur and Li2S cathodes

Constructing Ultrahigh-Capacity Zinc–Nickel–Cobalt Oxide@Ni(OH)₂ Core–Shell Nanowire Arrays for High-Performance Coaxial Fiber-Shaped Asymmetric Supercapacitors

Increased efforts have recently been devoted to developing high-energy-density flexible supercapacitors for their practical applications in portable and wearable electronics. Although high operating voltages have been achieved in fiber-shaped asymmetric supercapacitors (FASCs), low specific capacitance still restricts the further enhancement of their energy density. This article specifies a facile and cost-effective method to directly grow three-dimensionally well-aligned zinc–nickel-cobalt oxide (ZNCO)@Ni­(OH)₂ nanowire arrays (NWAs) on a carbon nanotube fiber (CNTF) with an ultrahigh specific capacitance of 2847.5 F/cm³ (10.678 F/cm²) at a current density of 1 mA/cm², These levels are approximately five times higher than those of ZNCO NWAs/CNTF electrodes (2.10 F/cm²) and four times higher than Ni­(OH)₂/CNTF electrodes (2.55 F/cm²). Benefiting from their unique features, we successfully fabricated a prototype coaxial FASC (CFASC) with a maximum operating voltage of 1.6 V, which was assembled by adopting ZNCO@Ni­(OH)₂ NWAs/CNTF as the core electrode and a thin layer of carbon coated vanadium nitride (VN@C) NWAs on a carbon nanotube strip (CNTS) as the outer electrode with KOH poly­(vinyl alcohol) (PVA) as the gel electrolyte. A high specific capacitance of 94.67 F/cm³ (573.75 mF/cm²) and an exceptional energy density of 33.66 mWh/cm³ (204.02 μWh/cm²) were achieved for our CFASC device, which represent the highest levels of fiber-shaped supercapacitors to date. More importantly, the fiber-shaped ZnO-based photodetector is powered by the integrated CFASC, and it demonstrates excellent sensitivity in detecting UV light. Thus, this work paves the way to the construction of ultrahigh-capacity electrode materials for next-generation wearable energy-storage devices

Surface-enhanced Raman scattering from AgNP-graphene-AgNP sandwiched nanostructures

We developed a facile approach toward hybrid AgNP-graphene-AgNP sandwiched structures using self-organized monolayered AgNPs from wet chemical synthesis for the optimized enhancement of the Raman response of monolayer graphene. We demonstrate that the Raman scattering of graphene can be enhanced 530 fold in the hybrid structure. The Raman enhancement is sensitively dependent on the hybrid structure, incident angle, and excitation wavelength. A systematic simulation is performed, which well explains the enhancement mechanism. Our study indicates that the enhancement resulted from the plasmonic coupling between the AgNPs on the opposite sides of graphene. Our approach towards ideal substrates offers great potential to produce a "hot surface" for enhancing the Raman response of two-dimensional materials

Fabrication of mesoporous Li2S-C nanofibers for high performance Li/Li2S cell cathodes

A Li2S electrode is a very promising cathode for Li-ion batteries. However, the high voltage needed to activate Li/Li2S cells represents a challenging problem. Here, we report for the first time a mesoporous Li2S-C nanofiber composite with 72 wt% Li2S. The assembled Li/Li2S cells showed a low and stable voltage plateau of 2.51 V for the first charge and can deliver a high initial discharge capacity of similar to 800 mA h g(-1)

Synthesis of three-dimensional hyperbranched TiO2 nanowire arrays with significantly enhanced photoelectrochemical hydrogen production

The three-dimensional (3D) hierarchical nanostructure is one of the promising candidates for high performance photoelectrochemical (PEC) water splitting electrodes due to the reduced carrier diffusion distance, improved light absorption efficiency and charge collection efficiency. Here, by growing omnidirectional, densely packed branches on TiO2 nanowires, we demonstrated a 3D hyperbranched hierarchical TiO2 nanowire (HHNW) architecture that could significantly enhance the performance of PEC water splitting. Under a solar simulator with chopped AM 1.5G light of 100 mW cm(-2) intensity, the HHNW electrode yielded a photocurrent density of 1.21 mA cm(-2) at 1.23 V with respect to the reversible hydrogen electrode (RHE), which was about four times higher than that of TiO2 nanowires (NWs) (0.34 mA cm(-2)). The highest incident photon-to-current conversion efficiency (IPCE) obtained from our HHNWs was 77% at 365-425 nm. This greatly improved PEC performance can be attributed to the improved light absorption efficiency and the increased contact surface areas at the TiO2/electrolyte interface