Co-reporter:Xuejun Bai, Yueyang Yu, Harold H. Kung, Biao Wang, Jianming Jiang
Journal of Power Sources 2016 Volume 306() pp:42-48
Publication Date(Web):29 February 2016
DOI:10.1016/j.jpowsour.2015.11.102
•A porous 3D Si@SiOx/GH composite was synthesized for LIB anode material.•Si@SiOx/GH composite showed a stable storage capacity of 1020 mAh g−1 at 4 A g−1.•The outstanding performance could be attributed to the porous 3D structure of GH.A porous 3D graphene hydrogel (GH) composite embedded with Si nanoparticles coated with an ultrathin SiOx layer (Si@SiOx/GH) is successfully synthesized using a solution-based self-assembly process. The thickness of the SiOx coating, formed by an ozone treatment of the 30–50 nm diameter Si particles, increases with the treatment temperature, and its formation results in the presence of Si2+ and Si4+ on the surface of the Si nanoparticles. The GH provides an electrically conducting network of interconnecting, micron-size open cells bounded by ultrathin stacked graphene sheets onto which the coated Si nanoparticles are dispersed. The agglomeration among the Si particles decreases with increasing extent of surface oxidation. Electrodes constructed with the Si@SiOx/GH containing 71 wt.% Si@SiOx exhibit a stable storage capacity of 1020 mAh g−1 at 4 A g−1 and 1640 mAh g−1 after 140 cycles at 0.1 A g−1. The outstanding electrochemical performance can be attributed to the porous, open cell 3D structure of GH, which provides a large internal space and flexible and electrically conductive graphenic matrix that can accommodate volumetric changes of Si nanoparticles and a highly porous 3D structure of high specific surface area that allows rapid diffusion of Li-ions and easy penetration of electrolyte.
Co-reporter:Kun Peng, Biao Wang, Yueming Li and Chengchang Ji
RSC Advances 2015 vol. 5(Issue 99) pp:81468-81473
Publication Date(Web):18 Sep 2015
DOI:10.1039/C5RA18171B
Magnetron sputtering deposition (MSD) of TiO2 is applied on a porous polypropylene (PP) separator for lithium ion batteries. The surface morphology, contact angles, thermal properties, and electrolyte uptake of the modified separators are characterized and the electrochemical performances such as ionic conductivity, cycle performance, and high rate discharge capacity are investigated. The TiO2 MSD-coated separators present suppressed thermal shrinkage which may lead to improved safety of the batteries, and show improvement in wettability with polar electrolytes and cell performance as compared to the bare PP separator.
Co-reporter:Xuejun Bai, Biao Wang, Huaping Wang, Jianming Jiang
Journal of Alloys and Compounds 2015 Volume 628() pp:407-412
Publication Date(Web):15 April 2015
DOI:10.1016/j.jallcom.2014.12.211
•A novel architecture of profiled carbon fiber-supported Sn LIB anodes is developed.•This Sn/CF anode exhibits a reversible capacity of 740 mA h g−1 under 0.1 C for 160 cycles with about 92% capacity retention.•The unique structure and plentiful inter-fiber space enhance the electrochemical performance of the designed Sn/CF anode.Tin (Sn)-based lithium-ion battery (LIB) anodes are among the most promising alternatives for conventional graphite anodes due to their high specific capacity and safety. The applications of this anode material are restricted by its fast capacity fading during battery operation and its poor rate capacity. In this study, a novel architecture of profiled carbon fiber supported Sn anodes is developed. The profiled carbon fibers have numerous surface grooves where Sn particles are embedded to provide enough capillary channels for rapid lithium-ion transport and enough inter-fiber space for the accommodation of large Sn volume changes on lithium insertion and extraction. This anode architecture is demonstrated by enhanced electrochemical performance. The reversible capacity of 740 mA h g−1 at 0.1 C after 160 cycles is two times higher than that of the state-of-the-art graphite anode. The simple and applicable synthesis process also provides a new path for designing and preparing carbon fiber-based anode materials with improved electrochemical properties.Graphical abstract
Co-reporter:Cheng-Ran Yang;Yu-Mei Zhang
Journal of Applied Polymer Science 2015 Volume 132( Issue 37) pp:
Publication Date(Web):
DOI:10.1002/app.42545
ABSTRACT
P(AN-co-VA-co-DEMA) terpolymers were synthesized by aqueous precipitation copolymerization of acrylonitrile (AN), vinyl acetate (VA), and 2-dimethylamino ethyl methacrylate (DEMA) with an Na2S2O5–NaClO3 redox initiating system and fibers from these terpolymers were thus prepared by a wet spinning method. Functionalized multiwalled carbon nanotube (F-MWNT) networks were created on the surface of P(AN-co-VA-co-DEMA) fibers by a simple dipping method. The morphology and interfacial interactions of the obtained F-MWNTs-coated fibers were characterized by scanning electron microscope, Raman spectroscopy, and Fourier transform infrared spectroscopy. The results showed that F-MWNTs were assembled on the fibers and the density of F-MWNTs can be controlled by adjusting the F-MWNTs content in the dipping solution. The assembly process was driven by electrostatic interactions between the negative charges on the nanotube sidewalls and the positive charges of the fibers. The F-MWNTs-coated fibers had a good conductivity. The volume resistivity of the fibers coated with 1.18 wt % F-MWNTs reached 0.27 Ω·cm, while the original mechanical properties were preserved. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42545.
Co-reporter:Chengran Yang;Yumei Zhang;Huaping Wang
Fibers and Polymers 2015 Volume 16( Issue 8) pp:1611-1617
Publication Date(Web):2015 August
DOI:10.1007/s12221-015-4480-1
The polyacrylonitrile (PAN) fibers grafted with guanidine groups were prepared by hydrolyzing with sodium hydroxide solution followed by reacting with polyhexamethylene guanidine hydrochloride (PHGC). The grafting degree could be controlled by changing the treatment time of hydrolyzed PAN fibers with PHGC. The chemical composition and morphology of the modified PAN fibers were characterized by Fourier transform infrared spectroscopy (FTIR), Elemental analysis (EA), X-ray photoelectric spectroscopy (XPS) and scanning electron microscope (SEM). The results showed that the guanidine groups were effectively grafted on the fibers. The water contact angle of the surface modified PAN fibers was reduced and moisture regain was improved significantly with the immobilization of PHGC on the fibers. Furthermore, the modified PAN fibers exhibited favorable acid dyeability at low temperature (50 °C) over a wide pH range and good mechanical properties. The simple and applicable synthesis process provides a new avenue for modification of PAN fibers with improved hydrophilicity and acid dyeability.
Co-reporter:Yunzhou Shi, Biao Wang
Progress in Natural Science: Materials International 2014 Volume 24(Issue 1) pp:56-60
Publication Date(Web):February 2014
DOI:10.1016/j.pnsc.2014.01.006
Carbon fiber (CF)/cellulose (CLS) composite papers were prepared by papermaking techniques and hot-melting fibers were used for modification. The mechanical properties of the obtained composite papers with different CF, CLS and hot-melting fiber ratios were studied and further discussed. It is observed that, for both CF/CLS composite papers and those modified by hot-melting fibers, the normal stress firstly increases and then declines with the addition of carbon fibers. The results also show that with the addition of hot-melting fibers, the modified papers exhibit enhanced mechanical performance compared to CF/CLS composite papers. Through SEM characterization, it is confirmed that the improvement of mechanical properties attributes to the reinforcement of adhesive binding at the fiber overlap nodes. Also, through four-probe method, the resistivity and the electrical performance of the modified and unmodified papers were characterized and the result shows that the hot-melting fiber modification brings no harm to the electrical properties.
Co-reporter:Qiongjuan Duan, Biao Wang, Jiong Wang, Huaping Wang, Yonggen Lu
Journal of Power Sources 2010 Volume 195(Issue 24) pp:8189-8193
Publication Date(Web):15 December 2010
DOI:10.1016/j.jpowsour.2010.07.032
A carbon nanofiber sheet (CNFS) has been prepared by electrospinning, stabilisation and subsequent carbonisation processes. Imaging with scanning electron microscope (SEM) indicates that the CNFS is formed by nonwoven nanofibers with diameters between 400 and 700 nm. The CNFS, with its three-dimensional pores, shows excellent electrical conductivity and hydrophobicity. In addition, it is found that the CNFS can be successfully applied as a micro-porous layer (MPL) in the cathode gas diffusion layer (GDL) of a proton exchange membrane fuel cell (PEMFC). The GDL with the CNFS as a MPL has higher gas permeability than a conventional GDL. Moreover, the resultant cathode GDL exhibits excellent fuel cell performance with a higher peak power density than that of a cathode GDL fabricated with a conventional MPL under the same test condition.
Co-reporter:Biao Wang;Ying Sun;Huaping Wang
Journal of Applied Polymer Science 2010 Volume 115( Issue 3) pp:1781-1786
Publication Date(Web):
DOI:10.1002/app.31288
Abstract
Polyacrylonitrile (PAN)/Fe3O4 composite nanofibers were prepared via the electrospinning of the PAN spinning solutions with magnetite Fe3O4 nanoparticles. The experimental results showed that the morphology and diameter of the nanofibers strongly depended upon concentrations of PAN and salt additives in the spinning solutions. A suitable PAN concentration and LiCl additives could effectively prevent the occurrence of beads in the electrospinning process and affected the diameters of the electrospun nanofibers. The breaking strength and breaking strain decreased when the magnetite Fe3O4 nanoparticles were incorporated. The prepared PAN/Fe3O4 nanofibers were superparamagnetic at room temperature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010
Co-reporter:Xiuling Zhu;Huaping Wang
Polymer Bulletin 2010 Volume 65( Issue 7) pp:719-730
Publication Date(Web):2010 October
DOI:10.1007/s00289-010-0321-y
A series of alkaline polyvinyl alcohol/1-ethyl-3-methylimidazolium hydroxide (PVA/[Bmim]OH) electrolyte membranes were developed via a direct blending and solution casting method. The structure and conductive properties of PVA/[Bmim]OH membranes with various concentrations of [Bmim]OH were systematically studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), attenuated total reflectance Fourier-transform infrared (ATR-FTIR), tensile-strength analysis, and AC impedance spectroscopy. When blended, the PVA/[Bmim]OH membrane exhibited superior ionic conductive and the maximum ionic conductivity was found around 0.0196 S cm−1 when the weight ratio of [Bmim]OH to PVA was 2.0. A model was proposed to illustrate the structure of PVA/[Bmim]OH membranes and the effect of [Bmim]OH on the ionic conductivity of the PVA matrix. The results and the model indicated that the addition of [Bmim]OH could significantly improve the electrochemical properties of the membranes, which is a promising candidate for direct methanol fuel cells (DMFCs) applications.
Co-reporter:Biao Wang, Yanfang Tang, Zhiwei Wen, Huaping Wang
European Polymer Journal 2009 Volume 45(Issue 10) pp:2962-2965
Publication Date(Web):October 2009
DOI:10.1016/j.eurpolymj.2009.07.001
We report here the initial results that polybenzimidazole can be dissolved in and regenerated from, 1-butyl-3-methylimidazolium chloride and other hydrophilic ionic liquids, which may enable the application of ionic liquids as alternatives to environmentally undesirable solvents currently used for dissolution of this polymer.PBI can be dissolved in [BMIM]Cl at 140 °C, which may enable the application of ionic liquids as alternatives to environmentally undesirable solvents currently used for dissolution of this polymer.
Co-reporter:Ying Sun, Biao Wang, Huaping Wang, Jianming Jiang
Journal of Colloid and Interface Science 2007 Volume 308(Issue 2) pp:332-336
Publication Date(Web):15 April 2007
DOI:10.1016/j.jcis.2006.12.076
Magnetic poly(styrene-co-acrylic acid-co-acrylamide) microspheres were prepared by water-in-oil-in-water (W/O/W) miniemulsion polymerization of monomers in the presence of Fe3O4 nanoparticles. The copolymerizable monomers of acrylic acid and acrylamide were used not only to modify the surfaces of the microspheres with functional groups, but also to act as viscosity regulators to control the morphology and size of these microspheres. It was experimentally observed that the surfaces of these microspheres were functionalized with NH2 groups produced by copolymerization, the morphologies (sphere, ringlike, and one-hole) of the microspheres were controlled by the concentration of copolymerizable monomers, and all samples prepared were superparamagnetic. The possible mechanism of formation of these magnetic microspheres is also discussed.Magnetic poly(styrene-co-acrylic acid-co-acrylamide) microspheres with ringlike or one-hole structures were prepared by miniemulsion polymerization of monomers in the presence of Fe3O4 nanoparticles. The morphology and size of these microspheres can be controlled by the viscosity of the water phase.
