Lubin Ni

Petal-like MoS2 Nanosheets Space-Confined in Hollow Mesoporous Carbon Spheres for Enhanced Lithium Storage Performance

An innovative approach for efficient synthesis of petal-like molybdenum disulfide nanosheets inside hollow mesoporous carbon spheres (HMCSs), the yolk-shell structured MoS2@C, has been developed. HMCSs effectively control and confine in situ growth of MoS2 nanosheets and significantly improve the conductivity and structural stability of the hybrid material. The yolk-shell structured MoS2@C is proven to achieve high reversible capacity (993 mA h g-1 at 1 A g-1 after 200 cycles), superior rate capability (595 mA h g-1 at a current density of 10 A g-1), and excellent cycle performance (962 mA h g-1 at 1 A g-1 after 1000 cycles and 624 mA h g-1 at 5 A g-1 after 400 cycles) when evaluated as an anode material for lithium-ion batteries. This superior performance is attributed to the yolk-shell structure with conductive mesoporous carbon as the shell and the stack of two-dimensional MoS2 nanosheets as the yolk.

Core–Shell Structure and Interaction Mechanism of γ-MnO2 Coated Sulfur for Improved Lithium-Sulfur Batteries

Lithium-sulfur batteries have attracted worldwide interest due to their high theoretical capacity of 1672 mAh g-1 and low cost. However, the practical applications are hampered by capacity decay, mainly attributed to the polysulfide shuttle. Here, the authors have fabricated a solid core-shell γ-MnO2 -coated sulfur nanocomposite through the redox reaction between KMnO4 and MnSO4 . The multifunctional MnO2 shell facilitates electron and Li+ transport as well as efficiently prevents polysulfide dissolution via physical confinement and chemical interaction. Moreover, the γ-MnO2 crystallographic form also provides one-dimensional (1D) tunnels for the Li+ incorporation to alleviate insoluble Li2 S2 /Li2 S deposition at high discharge rate. More importantly, the MnO2 phase transformation to Mn3 O4 occurs during the redox reaction between polysulfides and γ-MnO2 is first thoroughly investigated. The S@γ-MnO2 composite exhibits a good capacity retention of 82% after 300 cycles (0.5 C) and a fade rate of 0.07% per cycle over 600 cycles (1 C). The degradation mechanism can probably be elucidated that the decomposition of the surface Mn3 O4 phase is the cause of polysulfide dissolution. The recent work thus sheds new light on the hitherto unknown surface interaction mechanism and the degradation mechanism of Li-S cells.

Dual Core–Shell-Structured S@C@MnO2 Nanocomposite for Highly Stable Lithium–Sulfur Batteries

Lithium-sulfur (Li-S) batteries have currently excited worldwide academic and industrial interest as a next-generation high-power energy storage system (EES) because of their high energy density and low cost of sulfur. However, the commercialization application is being hindered by capacity decay, mainly attributed to the polysulfide shuttle and poor conductivity of sulfur. Here, we have designed a novel dual core-shell nanostructure of S@C@MnO2 nanosphere hybrid as the sulfur host. The S@C@MnO2 nanosphere is successfully prepared using mesoporous carbon hollow spheres (MCHS) as the template and then in situ MnO2 growth on the surface of MCHS. In comparison with polar bare sulfur hosts materials, the as-prepared robust S@C@MnO2 composite cathode delivers significantly improved electrochemical performances in terms of high specific capacity (1345 mAh g-1 at 0.1 C), remarkable rate capability (465 mA h g-1 at 5.0 C) and excellent cycling stability (capacity decay rate of 0.052% per cycle after 1000 cycles at 3.0 C). Such a structure as cathode in Li-S batteries can not only store sulfur via inner mesoporous carbon layer and outer MnO2 shell, which physically/chemically confine the polysulfides shuttle effect, but also ensure overall good electrical conductivity. Therefore, these synergistic effects are achieved by unique structural characteristics of S@C@MnO2 nanospheres.

Heterogeneous Double-Shelled Constructed Fe3O4 Yolk–Shell Magnetite Nanoboxes with Superior Lithium Storage Performances

Among the numerous candidate materials for lithium ion batteries, ferroferric oxide (Fe3O4) has been extensively concerned as a prospective anode material because of its high theoretical specific capacity, abundant resources, low cost, and nontoxicity. Here, we designed and fabricated a unique yolk-shell construction by generating heterogeneous double-shelled SnO2 and nitrogen-doped carbon on Fe3O4 yolk (denoted as Fe3O4@SnO2@C-N nanoboxes). The yolk-shell structured Fe3O4@SnO2@C-N nanoboxes have the adjustable void space, which permits the free expansion of Fe3O4 yolks without breaking the double shells during the lithiation/delithiation processes, avoiding the structural pulverization. Moreover, the heterogeneous double-shelled SnO2@C-N can meaningfully improve the electronic conductivity and enhance the lithium storage performance. Two metal oxides also show the specific synergistic effect, promoting the electrochemistry reaction. As a result, this yolk-shell structured Fe3O4@SnO2@C-N exhibits high specific capacity (870 mA h g-1 at 0.5 A g-1 after 200 cycles), superior rate capability, and long cycle life (670 mA h g-1 at 3 A g-1 after 600 cycles). This design and construction method can be extended to synthesize other yolk-shell nanostructured anode materials with improved electrochemistry performance.

An asymmetric binuclear zinc(II) complex with mixed iminodiacetate and phenanthroline ligands: synthesis, characterization, structural conversion and anticancer properties

Transition metal complexes with substituted high affinity mixed ligands as potential anticancer agents can overcome the drawbacks of platinum-based drugs that are currently being marketed. Here, a new water-soluble asymmetric binuclear iminodiacetato-zinc(II) complex [Zn2(ida)(phen)3(NO3)]·NO3·5H2O (1) with a phenanthroline ligand has been synthesized and fully characterized with a wide range of analytical techniques including single crystal X-ray diffraction as well as spectroscopic techniques, such as FT-IR, UV/Vis, photoluminescence spectroscopy, and furthermore by elemental and thermogravimetric analyses. Moreover, unprecedented (H2O)10 water clusters consisting of a quasi-planar tetramer and six dangling water molecules were observed in the void space of 3D supramolecular assemblies. The conversion behavior of (1) into two monomeric species [Zn(ida)(phen)(H2O)] (2) and [Zn(phen)2(H2O)2]2+ (3) in aqueous solution was first studied by solid-state/solution NMR, ESI-MS, and solution UV/vis spectra. Next, these zinc(II) complexes (1–3), a mixture of (2) and (3) (mole ratio 1/1), ligands (phen and ida) and zinc ions (ZnCl2 and ZnSO4) were further evaluated for the in vitro cytotoxic profile in human hepatoma cell lines (HepG2 and SMMC-7721). We found that complex (1) effectively inhibited the proliferation of hepatocellular carcinoma cells, which is similar to a mixture of (2) and (3) in a 1:1 molar ratio, and IC50 values of (1) were almost about 20–50% of (2) or (3). Therefore, this binuclear complex (1) mainly acts as a cooperative inhibitor with complexes (2) and (3) toward tumor growth in solution. We further extended the preliminary research of complex (1) and found that (1) could induce cell cycle arrest at the G0/G1 phase. Additionally, overdosing on (1) exhibited low toxicity of mice (LD50 of (1) in ICR mice = 736 mg kg−1, with 95% confidence interval 635–842 mg kg−1). In conclusion, complex (1) with a high antitumor activity and low toxicity provides a new strategy for the treatment of liver cancer.

Coaxial Carbon/MnO2 Hollow Nanofibers as Sulfur Hosts for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have recently attracted a large amount of attention as promising candidates for next-generation high-power energy storage devices because of their high theoretical capacity and energy density. However, the shuttle effect of polysulfides and poor conductivity of sulfur are still vital issues that constrain their specific capacity and cyclic stability. Here, we design coaxial MnO2 -graphitic carbon hollow nanofibers as sulfur hosts for high-performance lithium-sulfur batteries. The hollow C/MnO2 coaxial nanofibers are synthesized via electrospinning and carbonization of the carbon nanofibers (CNFs), followed by an in situ redox reaction to grow MnO2 nanosheets on the surface of CNFs. The inner graphitic carbon layer not only maintains intimate contact with sulfur and outer MnO2 shell to significantly increase the overall electrical conductivity but also acts as a protective layer to prevent dissolution of polysulfides. The outer MnO2 nanosheets restrain the shuttle effect greatly through chemisorption and redox reaction. Therefore, the robust S@C/MnO2 nanofiber cathode delivers an extraordinary rate capability and excellent cycling stability with a capacity decay rate of 0.044 and 0.051 % per cycle after 1000 cycles at 1.0 C and 2.0 C, respectively. Our present work brings forward a new facile and efficient strategy for the functionalization of inorganic metal oxide on graphitic carbons as sulfur hosts for high performance Li-S batteries.

Ultrathin WS2 nanosheets vertically embedded in a hollow mesoporous carbon framework – a triple-shell structure with enhanced lithium storage and electrocatalytic properties

Ultrathin WS2 nanosheets are vertically embedded in hollow mesoporous carbon spheres (HMCSs) to form unique hierarchical triple-shell (WS2–C–WS2) hollow nanospheres, i.e. HTSHNs WS2/C, via a facile and scalable hydrothermal method. The as-synthesized HTSHNs WS2/C nanocomposites are confirmed to have an expanded interlayer spacing of WS2 with chemical bonding between WS2 and HMCSs. The expanded WS2 interlayer spacing contributes to the enhancement of the kinetics of ion/electron transport and the improvement of the electrochemical performance of the HTSHNs WS2/C. As a result, the optimized HTSHNs WS2/C composites deliver a superior rate capability of 396 mA h g−1 at 10 A g−1, and stable cycling performance up to 1000 cycles, presenting a capacity of 784 and 442 mA h g−1 at 1 and 5 A g−1, respectively. Additionally, HTSHNs WS2/C provide abundant catalytically active sites for the enhancement of the electrocatalytic activity for the hydrogen evolution reaction (HER).