Jin-Guo Wang

Hierarchical TiO2 spheres as highly efficient polysulfide host for lithium-sulfur batteries

Hierarchical TiO2 micron spheres assembled by nano-plates were prepared through a facile hydrothermal route. Chemical tuning of the TiO2 through hydrogen reduction (H-TiO2) is shown to increase oxygen-vacancy density and thereby modifies the electronic properties. H-TiO2 spheres with a polar surface serve as the surface-bound intermediates for strong polysulfides binding. Under the restricting and recapturing effect, the sulfur cathode could deliver a high reversible capacity of 928.1 mA h g−1 after 50 charge-discharge cycles at a current density of 200 mA g−1. The H-TiO2 additive developed here is practical for restricting and recapturing the polysulfide from the electrolyte.

Design and synthesis of ZnO–NiO–Co3O4 hybrid nanoflakes as high-performance anode materials for Li-ion batteries

ZnO–NiO–Co3O4 hybrid nanoflakes are fabricated via a simple hydrothermal method followed by a subsequent annealing process. In these hybrid electrode materials, ZnO and NiO are the main active materials while a small amount of Co3O4 is introduced as a catalyzing and performance-enhancing agent. The obtained hybrid materials possess a novel 2D nanoflake structure which is mainly constructed by firmly interconnected ZnO and NiO nanoparticles. The particle size of ZnO and NiO is reduced to about 47 nm and 12 nm, respectively, through the hybridization process. When applied as anode materials, the ZnO–NiO–Co3O4 hybrid nanoflakes exhibit a high reversible capacity of 1060 mA h g−1 after 300 cycles at 500 mA g−1. The successful alleviation of the capacity fading problem and excellent electrochemical performance can be ascribed to the unique 2D nano-morphology, strong cobalt catalysis, improved electronic conductivity, uniform dispersity and porous surface. The results demonstrate that the ZnO–NiO–Co3O4 hybrid nanoflakes are promising anode materials for high-performance lithium-ion batteries.

One-step synthesis of Co-doped Zn2SnO4–graphene–carbon nanocomposites with improved lithium storage performances

Co-doped Zn2SnO4–graphene–carbon nanocomposites have been prepared for the first time through a convenient one-step hydrothermal method. The size of Co-doped Zn2SnO4 nanoparticles is about 3–5 nm and they are well dispersed on graphene nanosheets and carbon layer. L-Ascorbic acid is introduced to serve as a reductant for GO and carbon sources. The doping of Co can enhance the crystalline degree of Zn2SnO4 nanoparticles. When evaluated as anode materials for lithium ion batteries, the Co–ZTO–G–C nanocomposites exhibited a significantly higher reversible capacity of 699 mA h g−1 after 50 cycles at 100 mA g−1 and an improved cycling stability of 461 mA h g−1 after 200 cycles at 500 mA g−1 compared with Co–ZTO–G and ZTO–G–C nanocomposites. Moreover, even at a high current density of 1000 mA g−1, the reversible capacity of 418 mA h g−1 still remained. The improved electrochemical performance can be attributed to the synergy of the graphene substrate, the protective carbon layer, the uniform ultrafine Zn2SnO4 nanoparticles and Co doping. Therefore, Co–ZTO–G–C nanocomposites show great prospect as anodes for lithium-ion batteries.

Facile synthesis of hierarchical worm-like MoS2 structures assembled with nanosheets as anode for lithium ion batteries

Hierarchical worm-like MoS2 structures directionally assembled with nanosheets are successfully synthesized via a simple hydrothermal route using potassium sodium tartrate as a structure-directing agent. The possible growth mechanism of worm-like MoS2 structures is proposed through controlling hydrothermal temperature, time and the amount of potassium sodium tartrate. The results indicate that potassium sodium tartrate plays important roles in formation of worm-like structures. The unique hierarchical structures as anodes for lithium-ion batteries display high specific capacity of 845 mA h g−1 after 50 cycles at 100 mA g−1 and good cyclic stability of 698 mA h g−1 even at high rate of 500 mA g−1 after 100 cycles. The excellent electrochemical performance can be attributed to the hierarchical surface, sufficient void space between neighboring nanosheets and unique worm-like structures. Besides, this work also provides a simple strategy to design and construct other structural materials, such as layered metal sulfides and oxides.

Microstructure and tensile properties of new type of hot rolled Mg–3Sn–1Zn alloy sheet at elevated temperatures

Abstract Uniaxial tensile tests of a new type of hot rolled Mg–3Sn–1Zn (TZ31) alloy have been investigated within the temperature range of 25 to 200°C. The elongation to failure ϵf increases from 21·9% at 25°C to 79·0% at 200°C, while the 0·2% offset yield strength and peak true strength σp decrease from 141 to 60 MPa and from 264 to 91 MPa respectively. The thermal stability of globular Mg2Sn precipitates is beneficial to the strength of the rolled TZ31 alloy at elevated temperatures. However, dynamic recovery and dynamic recrystallisation play an important role in the elevated temperature elongation. Results obtained here can be used as a reference to develop inexpensive new types Mg alloys with potential for applications at elevated temperatures.

Modification of Primary Mg2Si in Mg-4Si Alloys with Antimony

The refinement in size and modification in morphology for primary Mg2Si depended significantly on Sb contents in Mg-4Si alloys. Adding Sb into melts evidently increased the nucleus numbers of primary Mg2Si crystals. Moreover, the preferential growth along

One-step in situ growth of ZnS nanoparticles on reduced graphene oxides and their improved lithium storage performance using sodium carboxymethyl cellulose binder

\left\langle { 100} \right\rangle

High strength and good ductility at elevated temperature of nano-SiCp/Al2014 composites fabricated by semi-solid stir casting combined with hot extrusion

directions in dendritic crystals was restricted greatly due to the Si sites being substituted by Sb in Mg2Si lattices, resulting in modified primary Mg2Si crystals growing to octahedral morphology surrounded by {111} planes; therefore, the modification process could be called adsorption and poisoning mechanisms.