Well-dispersed sulfur anchored on interconnected polypyrrole nanofiber network as high performance cathode for lithium-sulfur batteries

Abstract Preparation of novel sulfur/polypyrrole (S/PPy) composite consisting well-dispersed sulfur particles anchored on interconnected PPy nanowire network was demonstrated. In such hybrid structure, the as-prepared PPy clearly displays a three-dimensionally cross-linked and hierarchical porous structure, which was utilized in the composite cathode as a conductive network trapping soluble polysulfide intermediates and enhancing the overall electrochemical performance of the system. Benefiting from this unique structure, the S/PPy composite demonstrated excellent cycling stability, resulting in a discharge capacity of 931 mAh g−1 at the second cycle and retained about 54% of this value over 100 cycles at 0.1 C. Furthermore, the S/PPy composite cathode exhibits a good rate capability with a discharge capacity of 584 mAh g−1 at 1  C

Multiscale Hierarchical Structure and Laminated Strengthening and Toughening Mechanisms

Metal matrix composites with multiscale hierarchical structure and laminated structure have been developed to provide a novel route to achieve high strength, toughness and ductility. In this chapter, a lot of scientific research has been carried out in the preparation, processing, properties and application of metal matrix composite. Many toughening mechanisms and fracture behavior of composites with multiscale hierarchical structure and laminated structure are overviewed. It is revealed that elastic property and yield strength of laminated composites follow the “rule of average.” However, the estimation of fracture elongation and fracture toughness is complex, which is inconsistent with the “rule of average.” The fracture elongation of laminated composites is related to the layer thickness size, interface, gradient structure, strain hardening exponent, strain rate parameter and tunnel crack, which are accompanied with crack deflection, crack blunting, crack bridging, stress redistribution, local stress deformation, interfacial delamination crack and so on. The concept of laminated composites can be extended by applying different combination of individual layer, and provides theoretical as well as experimental fundamentals on strengthening and toughening of metal matrix composites

Synthesis of hierarchical MoS2 microspheres composed of nanosheets assembled via facile hydrothermal method as anode material for lithium-ion batteries

A hierarchical MoS2 architecture composed of nanosheet-assembled microspheres with an expanded interplanar spacing of the (002) planes was successfully prepared via a simple hydrothermal reaction. Electron microscopy studies revealed formation of the MoS2 microspheres with an average diameter of 230 nm. It was shown that the hierarchical structure of MoS2 microspheres possesses both the merits of nanometer-sized building blocks and micrometer-sized assemblies, which offer high surface area for fast kinetics and buffers the volume expansion during lithium insertion/deinsertion, respectively. The micrometer-sized assemblies were found to contribute to the enhanced electrochemical stabilities of the electrode materials...

Micro-Spherical Sulfur/Graphene Oxide Composite via Spray Drying for High Performance Lithium Sulfur Batteries

An efficient, industry-accepted spray drying method was used to synthesize microspherical sulfur/graphene oxide (S/GO) composites as cathode materials within lithium sulfur batteries. The as-designed wrapping of the sulfur-nanoparticles, with wrinkled GO composites, was characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The unique morphological design of this material enabled superior discharge capacity and cycling performance, demonstrating a high initial discharge capacity of 1400 mAh g1 at 0.1 C. The discharge capacity remained at 828 mAh g1 after 150 cycles. The superior electrochemical performance indicates that the S/GO composite improves electrical conductivity and alleviates the shuttle effect. This study represents the first time such a facile spray drying method has been adopted for lithium sulfur batteries and used in the fabrication of S/GO composite

Synthesis and Characterization of Nanostructured WC-Co/Al Powder Prepared by Mechanical Alloying

Nanostructured WC-Co/Al powder was synthesized from WC-12Co powder and pure Al powder by mechanical alloying (MA). The morphology and microstructural evolution of WC-Co/Al powder were investigated by a series of characterization methods. The results showed that the β-Co phase in the initial WC-12Co powder was replaced by the AlxCo phases (such as Al9Co2 and Al13Co4). As the ball milling time increased, the average grain size of WC in the WC-Co/Al powder decreased firstly and then remained at a constant value of around 40 nm. The deposition behavior of powders sprayed by high velocity oxygen fuel (HVOF) spraying was investigated. During spraying, the WC-Co/Al powder had a better flattening than the WC-12Co powder without ball milling, which is beneficial to fabricate compact coatings with lower porosity

Corn stalk-derived activated carbon with a stacking sheet-like structure as sulfur cathode supporter for lithium/sulfur batteries

A novel stacking sheet-like carbon (SSC) has been synthesized by carbonizing the corn stalks and composited with sulfur to prepare a cathode for lithium/sulfur batteries. Scanning electronic microscopy observations showed the formation of irregularly interlaced nanosheet-like structure consisting SSC with uniform sulfur coating on its surface. The SSC nanoflakes in the composite act as nanocurrent collectors, favoring the charge carrier ion transport and electrolyte diffusion. The interlaced SSC nanoflakes irregularly stack together and form a three-dimensional network, which is beneficial for both trapping soluble polysulfide intermediates and rendering the electrical conductivity of the composite electrode..

Simple One-Pot Synthesis of Hexagonal ZnO Nanoplates as Anode Material for Lithium-Ion Batteries

Hexagonal ZnO nanoplates were synthesized via simple one-pot hydrothermal reaction of Zn(CH3COO)2 and CO(NH2)2. XRD, SEM, and HRTEM were used to investigate the composition and microstructure of the material. Together with the facile strain relaxation during structure and volume change upon cycling, this plate-like structure of ZnO is favorable for physical and chemical interactions with lithium ions because of its large contact area with the electrolyte, providing more active sites and short diffusion distances. The resulting hexagonal ZnO nanoplates electrode exhibited good cyclability and delivered a reversible discharge capacity of 368 mAh g−1 after 100 cycles at 0.1 C

A free-standing sulfur/nitrogen-doped carbon nanotube electrode for high- performance lithium/sulfur batteries

A free-standing sulfur/nitrogen-doped carbon nanotube (S/N-CNT) composite prepared via a simple solution method was first studied as a cathode material for lithium/sulfur batteries. By taking advantage of the self-weaving behavior of N-CNT, binders and current collectors are rendered unnecessary in the cathode, thereby simplifying its manufacturing and increasing the sulfur weight ratio in the electrode. Transmission electronic microscopy showed the formation of a highly developed core-shell tubular structure consisting of S/N-CNT composite with uniform sulfur coating on the surface of N-CNT. As a core in the composite, the N-CNT with N functionalization provides a highly conductive and mechanically flexible framework, enhancing the electronic conductivity and consequently the rate capability of the material

Facile Synthesis of ZnO Nanoparticles on Nitrogen-Doped Carbon Nanotubes as High-Performance Anode Material for Lithium-Ion Batteries

ZnO/nitrogen-doped carbon nanotube (ZnO/NCNT) composite, prepared though a simple one-step sol-gel synthetic technique, has been explored for the first time as an anode material. The as-prepared ZnO/NCNT nanocomposite preserves a good dispersity and homogeneity of the ZnO nanoparticles (~6 nm) which deposited on the surface of NCNT. Transmission electron microscopy (TEM) reveals the formation of ZnO nanoparticles with an average size of 6 nm homogeneously deposited on the surface of NCNT. ZnO/NCNT composite, when evaluated as an anode for lithium-ion batteries (LIBs), exhibits remarkably enhanced cycling ability and rate capability compared with the ZnO/CNT counterpart. A relatively large reversible capacity of 1013 mAh_g-1 is manifested at the second cycle and a capacity of 664 mAh_g-1 is retained after 100 cycles. Furthermore, the ZnO/NCNT system displays a reversible capacity of 308 mAh_g-1 even at a high current density of 1600 mA_g-1. These electrochemical performance enhancements are ascribed to the reinforced accumulative effects of the well-dispersed ZnO nanoparticles and doping nitrogen atoms, which can not only suppress the volumetric expansion of ZnO nanoparticles during the cycling performance but also provide a highly conductive NCNT network for ZnO anode