Fuxing Yin

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.

Mechanism for direct graphite-to-diamond phase transition

Using classical molecular dynamics with a more reliable reactive LCBOPII potential, we have performed a detailed study on the direct graphite-to-diamond phase transition. Our results reveal a new so-called “wave-like buckling and slipping” mechanism, which controls the transformation from hexagonal graphite to cubic diamond. Based on this mechanism, we have explained how polycrystalline cubic diamond is converted from hexagonal graphite, and demonstrated that the initial interlayer distance of compressed hexagonal graphite play a key role to determine the grain size of cubic diamond. These results can broaden our understanding of the high pressure graphite-to-diamond phase transition.

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.

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 micro-spherical 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 g−1 at 0.1 C. The discharge capacity remained at 828 mAh g−1 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 composites.

Effect of WC/Co coherency phase boundaries on Fracture toughness of the nanocrystalline cemented carbides

The effect of coherency WC/Co phase boundaries on the fracture toughness of the nanocrystalline WC-Co cemented carbides is studied by MD simulation method. The simulation results show that the nanocrystalline WC-Co cemented carbides with coherency WC/Co phase boundaries has higher fracture toughness than that without coherency WC/Co phase boundaries. Moreover, the mechanism of why coherency WC/Co phase boundaries can improve the fracture toughness of the nanocrystalline cemented carbides is also investigated. It is found the fact that the separation energy of the coherent WC/Co phase boundary is larger than that of the incoherent WC/Co phase boundaries is the main reason for this excellent mechanical property.

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.

Electrochemical Properties of an Na4Mn9O18-Reduced Graphene Oxide Composite Synthesized via Spray Drying for an Aqueous Sodium-Ion Battery

An aqueous sodium ion battery (ASIB) with metal Zn as anode and Na4Mn9O18-reduced graphene oxide (Na4Mn9O18-RGO) as cathode has been developed. In this work, spherical Na4Mn9O18-RGO composite particles were prepared via spray drying. The aqueous battery exhibits stable cyclability and high specific capacities. Typically, a high initial discharge capacity of 61.7 mAh·g−1 is attained at a high current rate of 4 C, and a stabilizing reversible capacity of 58.9 mAh·g−1 was obtained after 150 cycles. The network interlaced by RGO sheets provided fast electron conduction paths and structural stability to accommodate the mechanical stresses induced by sodium insertion and extraction, so the Na4Mn9O18-RGO electrode displayed superior electrochemical performance in the ASIB.

Interconnected nitrogen-doped carbon nanofibers derived from polypyrrole for high-performance Li/S batteries

Interconnected nitrogen-doped carbon nanofibers (INC) prepared through the carbonization of polypyrrole (PPy) precursor is designed as scaffold to load sulfur. The BET measurement showed that INC possessed abundant mesopores with a relatively high specific surface area and a large total pore volume. The sulfur/INC (S/INC) composite was synthesized by a melt-diffusion of sulfur nanoparticle into INC network. Transmission electron microscopy showed the formation of a nanofiber structure with uniform sulfur coating on the surface of INCs. When tested as cathodes for Li/S batteries, a high initial discharge capacity of 1173 mAh g–1 and a reversible capacity of 702 mAh g–1 after 50 cycles at 0.1 C are achieved, which ascribe to the chemical and physical adsorption properties of mesoporous and nitrogen-doped INC.

ZnO nanorods grown directly on copper foil substrate as a binder-free anode for high performance lithium-ion batteries

1 Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province, China. 2 Synergy Innovation Institute of GDUT, Heyuan, Guangdong Province, China 3 Research Institute for Energy Equipment Materials, Tianjin key laboratory of laminating fabrication and interface control technology for advanced materials, Hebei University of Technology, Tianjin 300130, China 4 Institute of Batteries LLC, Center of Energy and Advanced Materials Science, PI National Laboratory Astana, School of Engineering, Nazarbayev University, 53 Kabanbay Batyr Avenue, Astana 010000, Kazakhstan 5 Institute of Advanced Materials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, Guangdong Province, China. * E-mail: yongguangzhang@hebut.edu.cn; wangxin@scnu.edu.cn

Effect of Ni interlayer on characteristics of diffusion bonded Mg/Al joints

ABSTRACT Magnesium and aluminium were joined through diffusing bonding with a Ni interlayer prepared by plasma spraying for the first time. Examination of the microstructure and phase constitution of interfacial regions indicated that Mg–Al reaction was successfully prevented in the presence of the Ni interlayer. With the elevation of temperature, a reaction layer of Mg2Ni intermetallic was formed at Mg/Ni interface but few Al–Ni intermetallic was generated at Al/Ni interface. The mechanical test results showed that the tensile strength of the Mg/Al joint was substantially improved compared to that of the direct joint of Mg and Al. A maximum value of 5.8 MPa was obtained at 420°C for the joint with Ni interlayer.