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Full-Text Articles in Physical Sciences and Mathematics

Flexible Free-Standing Graphene-Silicon Composite Film For Lithium-Ion Batteries, Jiazhao Wang, Chao Zhong, Shulei Chou, Hua Liu Feb 2013

Flexible Free-Standing Graphene-Silicon Composite Film For Lithium-Ion Batteries, Jiazhao Wang, Chao Zhong, Shulei Chou, Hua Liu

Shulei Chou

Flexible, free-standing, paper-like, graphene-silicon composite materials have been synthesized by a simple, one-step, in-situ filtration method. The Si nanoparticles are highly encapsulated in a graphene nanosheet matrix. The electrochemical results show that graphene-Si composite film has much higher discharge capacity beyond 100 cycles (708 mAh g− 1) than that of the cell with pure graphene (304 mAh g− 1). The graphene functions as a flexible mechanical support for strain release, offering an efficient electrically conducting channel, while the nanosized silicon provides the high capacity.


Nanocrystalline Nio Hollow Spheres In Conjunction With Cmc For Lithium-Ion Batteries, Chao Zhong, Jiazhao Wang, Shulei Chou, Konstantin Konstantinov, Mokhlesur Rahman, Hua Liu Feb 2013

Nanocrystalline Nio Hollow Spheres In Conjunction With Cmc For Lithium-Ion Batteries, Chao Zhong, Jiazhao Wang, Shulei Chou, Konstantin Konstantinov, Mokhlesur Rahman, Hua Liu

Shulei Chou

Hollow spherical NiO particles were prepared using the spray pyrolysis method with different concentrations of precursor. The electrochemical properties of the NiO electrodes, which contained a new type of binder, carboxymethyl cellulose (CMC), were examined for comparison with NiO electrodes with polyvinylidene fluoride (PVDF) binder. The electrochemical performance of NiO electrodes using CMC binder was significantly improved. For the cell made from 0.3 mol L−1 precursor, the irreversible capacity loss between the first discharge and charge is about 43 and 24% for the electrode with PVDF and CMC binder, respectively. The cell with NiO–CMC electrode has a much higher discharge …


Free-Standing Single-Walled Carbon Nanotube/Sno2 Anode Paper For Flexible Lithium-Ion Batteries, Lukman Noerochim, Jia-Zhao Wang, Shulei Chou, David Wexler Feb 2013

Free-Standing Single-Walled Carbon Nanotube/Sno2 Anode Paper For Flexible Lithium-Ion Batteries, Lukman Noerochim, Jia-Zhao Wang, Shulei Chou, David Wexler

Shulei Chou

Free-standingsingle-walledcarbonnanotube/SnO2 (SWCNT/SnO2) anodepaper was prepared by vacuum filtration of SWCNT/SnO2 hybrid material which was synthesized by the polyol method. From field emission scanning electron microscopy and transmission electron microscopy, the CNTs form a three-dimensional nanoporous network, in which ultra-fine SnO2 nanoparticles, which had crystallite sizes of less than 5 nm, were distributed, predominately as groups of nanoparticles on the surfaces of singlewalled CNT bundles. Electrochemical measurements demonstrated that the anodepaper with 34 wt.% SnO2 had excellent cyclic retention, with the high specific capacity of 454 mAh g−1 beyond 100 cycles at a current …


Irradiation Si On Carbon Nanotube Paper As A Flexible Anode Material For Lithium-Ion Batteries, Shulei Chou, Mihail Ionescu, Jia-Zhao Wang, Brad Winton, Hua Liu Feb 2013

Irradiation Si On Carbon Nanotube Paper As A Flexible Anode Material For Lithium-Ion Batteries, Shulei Chou, Mihail Ionescu, Jia-Zhao Wang, Brad Winton, Hua Liu

Shulei Chou

Silicon single walled carbon nanotube composite paper was modified by low energy ion implantation using 5i to obtain a flexible composite paper. Raman and FE-SEM results show that structure of SWCNT could be destroyed by the implantation. Electrochemical measurements display that the implanted SI can improve the specific capacity and the reversible capacity of CNT paper. After 50 cycles, the specific capacity of 5Hmplanted CNT paper is 30 per cent higher than the pristine CNT.


Paper-Like Free-Standing Polypyrrole And Polypyrrole-Lifepo4 Composite Films For Flexible And Bendable Rechargeable Battery, Jun Chen, Sau Yen Chew, S. Dou, Jiazhao Wang, Guoxiu Wang, Hua Liu, Konstantin Konstantinov, Jian Wu, Shulei Chou Nov 2012

Paper-Like Free-Standing Polypyrrole And Polypyrrole-Lifepo4 Composite Films For Flexible And Bendable Rechargeable Battery, Jun Chen, Sau Yen Chew, S. Dou, Jiazhao Wang, Guoxiu Wang, Hua Liu, Konstantin Konstantinov, Jian Wu, Shulei Chou

Shulei Chou

Highly flexible, paper-like, free-standing polypyrrole and polypyrrole-LiFePO4 composite films were prepared using the electropolymerization method. The films are soft, lightweight, mechanically robust and highly electrically conductivity. The electrochemical performance of the free-standing pure PPy electrode was improved by incorporating the most promising cathode material, LiFePO4, into the PPy films. The cell with PPy-LiFePO4 composite film had a higher discharge capacity beyond 50 cycles (80 mA h/g) than that of the cell with pure PPy (60 mA h/g). The free-standing films can be used as electrode materials to satisfy the new market demand for flexible and bendable batteries that are suitable …


Electrochemical Deposition Of Porous Vox And Mno2 Nanowires On Stainless Steel Mesh For Flexible Supercapacitors, Shulei Chou, Jiazhao Wang, Hua Liu, S Dou Nov 2012

Electrochemical Deposition Of Porous Vox And Mno2 Nanowires On Stainless Steel Mesh For Flexible Supercapacitors, Shulei Chou, Jiazhao Wang, Hua Liu, S Dou

Shulei Chou

Porous vanadium oxide (VOx) and MnO2 nanowires were synthesized by an electrochemical deposition method using stainless steel mesh as substrate. The as-prepared porous VOx and MnO2 nanowire films were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. The cyclic voltammetry (CV) results show that the MnO2 nanowire film shows specific capacitance of 195, 170, 158, and 91 F g-1 at scan rates of 5, 10, 20, and 50 mV s-1, respectively. The porous VOx film displays specific capacitance of 152, 124, 99, and 76 F g …


Enhanced Reversible Lithium Storage In A Nanosize Silicon/Graphene Composite, Shulei Chou, Jiazhao Wang, Mohammad Choucair, Hua Liu, John Stride, S Dou Nov 2012

Enhanced Reversible Lithium Storage In A Nanosize Silicon/Graphene Composite, Shulei Chou, Jiazhao Wang, Mohammad Choucair, Hua Liu, John Stride, S Dou

Shulei Chou

Si/graphene composite was prepared by simply mixing of commercially available nanosize Si and graphene. Electrochemical tests show that the Si/graphene composite maintains a capacity of 1168 mAh g-1 and an average coulombic efficiency of 93% up to 30 cycles. EIS indicates that the Si/graphene composite electrode has less than 50% of the charge-transfer resistance compared with nanosize Si electrode, evidencing the enhanced ionic conductivity of Si/graphene composite. The enhanced cycling stability is attributed to the fact that the Si/graphene composite can accommodate large volume charge of Si and maintain good electronic contact.


Sulfur-Mesoporous Carbon Composites In Conjunction With A Novel Ionic Liquid Electrolyte For Lithium Rechargeable Batteries, Jun Chen, Syed Ashraf, Sau Yen Chew, See How Ng, David Wexler, Jiazhao Wang, Hua Liu, Zhengwei Zhao, Shulei Chou Nov 2012

Sulfur-Mesoporous Carbon Composites In Conjunction With A Novel Ionic Liquid Electrolyte For Lithium Rechargeable Batteries, Jun Chen, Syed Ashraf, Sau Yen Chew, See How Ng, David Wexler, Jiazhao Wang, Hua Liu, Zhengwei Zhao, Shulei Chou

Shulei Chou

Sulfur coated mesoporous carbon (S-C) composites have been synthesized and physically characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, and thermogravimetric analysis. Firstly, the electrochemical properties of the S-C composite cathode materials were tested in a conventional electrolyte consisting of 1 mol/L lithium bistrifluormethanesulfonimidate in poly(ethylene glycol) dimethyl ether to compare them with pure sulphur electrode. The capacity and cyclic stability of the S-C composite were improved. Then the S-C composites were tested in a novel ionic liquid electrolyte consisting of 1-ethyl-3-methylimidazolium bis(trifluromethanesulfonyl)imide and lithium


Flexible Free-Standing Carbon Nanotube Films For Model Lithium-Ion Batteries, Jun Chen, Sau Yen Chew, See How Ng, Jiazhao Wang, Hua Liu, P Novak, F Krumeich, Shulei Chou Nov 2012

Flexible Free-Standing Carbon Nanotube Films For Model Lithium-Ion Batteries, Jun Chen, Sau Yen Chew, See How Ng, Jiazhao Wang, Hua Liu, P Novak, F Krumeich, Shulei Chou

Shulei Chou

No abstract provided.


One-Step Spray Pyrolysis Synthesized Cuo-Carbon Composite Combined With Carboxymethyl Cellulose Binder As Anode For Lithium-Ion Batteries, Chao Zhong, Jia-Zhao Wang, Xuan-Wen Gao, Shulei Chou, Konstantin Konstantinov, Hua Liu Nov 2012

One-Step Spray Pyrolysis Synthesized Cuo-Carbon Composite Combined With Carboxymethyl Cellulose Binder As Anode For Lithium-Ion Batteries, Chao Zhong, Jia-Zhao Wang, Xuan-Wen Gao, Shulei Chou, Konstantin Konstantinov, Hua Liu

Shulei Chou

Copper oxide-carbon composite with hollow sphere structure has been synthesized by a one-step spray pyrolysis method and tested as anode material for lithium-ion batteries. Different analytical methods, including X-ray powder diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, thermogravimetric analysis, and systematic electrochemical tests were performed. The results demonstrate that the CuO-carbon composite in conjunction with carboxymethyl cellulose (CMC) binder has an excellent electrochemical performance, with a capacity of 577 mAh g-1 up to 100 cycles. The usage of the water soluble binder, CMC, not only obviously improves the electrochemical performance, but also makes the electrode fabrication process much easier and …