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1.
ACS Nano ; 11(9): 8628-8635, 2017 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-28800223

RESUMO

Designing yolk-shell nanostructures is an effective way of addressing the huge volume expansion issue for large-capacity anode and cathode materials in Li-ion batteries (LIBs). Previous studies mainly focused on adopting a SiO2 template through HF etching to create yolk-shell nanostructures. However, HF etching is highly corrosive and may result in a significant reduction of Si content in the composite. Herein, a silkworm cocoon-like silicon-based composite is prepared through a green approach in which Al2O3 was selected as a sacrificial template. The void space between the outer nitrogen-doped carbon (NC) shell formed by chemical vapor deposition using a pyridine precursor and the inside porous silicon nanorods (p-Si NRs) synthesized by magnesiothermic reduction of ordered mesoporous silica nanorods can be generated by etching Al2O3 with diluted HCl. The obtained p-Si NRs@void@NC composite is utilized as an anode material for LIBs, which exhibits a large initial discharge capacity of 3161 mAh g-1 at 0.5 A g-1, excellent cycling behavior up to 300 cycles, and super rate performance. Furthermore, a deep understanding of the mechanism for the yolk-shell nanostructure during the Li-alloying process is revealed by in situ transmission electron microscopy and finite element simulation.

2.
ACS Appl Mater Interfaces ; 8(6): 3868-73, 2016 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-26720145

RESUMO

In this work, hydroquinone resin was used to grow carbon nanotubes directly on Ni foam. The composites were obtained via a simple carbonization method, which avoids using the explosive gaseous carbon precursors that are usually applied in the chemical vapor deposition method. When evaluated as cathode for Li-O2 batteries, the binder-free structure showed enhanced ORR/OER activities, thus giving a high rate capability (12690 mAh g(-1) at 200 mA g(-1) and 3999 mAh g(-1) at 2000 mA g(-1)) and outstanding long-term cycling stability (capacity limited 2000 mAh g(-1), 110 cycles at 200 mA g(-1)). The excellent battery performance provides new insights into designing a low-cost and high-efficiency cathode for Li-O2 batteries.

3.
Dalton Trans ; 44(18): 8678-84, 2015 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-25854214

RESUMO

A novel binder-free electrode for lithium-oxygen batteries has been prepared by electrodepositing a Co3O4 layer onto a pretreated TiO2 fiber mesh, formed on nickel foam by an electrospinning method. The Co3O4 depositing layer is composed of Co3O4 nanoflakes, forming a uniform flower-like porous structure. The Co3O4 nanoflakes within the depositing layer provide a large amount of catalytic active sites for oxygen evolution and reduction reactions. The three-dimensional porous network of the Co3O4 depositing layer can not only facilitate the transportation of ions and electrolyte within the electrode, but also provide plenty of space to accommodate Li2O2 species formed during the discharge process. The Co3O4 spheres embedded in the TiO2 fiber mesh, formed by the treatment of a suspension of cobaltammine precipitate, function as anchors to prevent the detachment of the Co3O4 layer from the current collector, resulting in excellent structural and cycling stability. Only a slight specific capacity decay is observed at full discharge/charge after 80 cycles. This work demonstrates the important factors in the preparation of binder-free cathodes for high performance lithium-oxygen batteries.

4.
Adv Mater ; 26(35): 6145-50, 2014 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-25047876

RESUMO

Uniform porous silicon hollow nano-spheres are prepared without any sacrificial templates through a magnesio-thermic reduction of mesoporous silica hollow nanospheres and surface modified by the following in situ chemical polymerization of polypyrrole. The porous hollow structure and polypyrrole coating contribute significantly to the excellent structure stability and high electrochemical performance of the nanocomposite.

5.
Chem Commun (Camb) ; 50(69): 9961-4, 2014 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-25034037

RESUMO

Sn/SnO nanoparticles are incorporated in crumpled nitrogen-doped graphene nanosheets by a simple melting diffusion method. The resulting composite exhibits large specific capacity, excellent cycling stability and high rate capability as an anode for lithium-ion batteries.

6.
Sci Rep ; 4: 4673, 2014 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-24728289

RESUMO

Stacking various two-dimensional atomic crystals on top of each other is a feasible approach to create unique multilayered heterostructures with desired properties. Herein for the first time, we present a controlled preparation of large-area graphene/MoS2 heterostructures via a simple heating procedure on Mo-oleate complex coated sodium sulfate under N2 atmosphere. Through a direct in situ catalytic reaction, graphene layer has been uniformly grown on the MoS2 film formed by the reaction of Mo species with Species, which is from the carbothermal reduction of sodium sulfate. Due to the excellent graphene "painting" on MoS2 atomic layers, the significantly shortened lithium ion diffusion distance and the markedly enhanced electronic conductivity, these multilayered graphene/MoS2 heterostructures exhibit high specific capacity, unprecedented rate performance and outstanding cycling stability, especially at a high current density, when used as an anode material for lithium batteries. This work provides a simple but efficient route for the controlled fabrication of large-area multilayered graphene/metal sulfide heterostructures with promising applications in battery manufacture, electronics or catalysis.

7.
Chem Commun (Camb) ; 49(44): 5007-9, 2013 Jun 04.
Artigo em Inglês | MEDLINE | ID: mdl-23612557

RESUMO

A sodiothermic reduction method has been developed for the preparation of porous silicon using aluminosilicate zeolite NaY as a precursor. The porous silicon with a specific surface area of approximately 570 m(2) g(-1) shows distinct capacitive behavior when used as an electrode material for supercapacitors.


Assuntos
Capacitância Elétrica , Silício/química , Silicatos de Alumínio/química , Técnicas Eletroquímicas , Eletrodos , Oxirredução , Porosidade , Propriedades de Superfície , Zeolitas/química
8.
Environ Sci Technol ; 44(19): 7673-7, 2010 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-20804149

RESUMO

A much "greener" and harmless leaching method for removing impurity aluminum further from industrial quartz sands by very dilute mixed acids has been presented. With the help of supersonic, the percentage of removal aluminum reached up to 52.5%/53%, that is, 17.4 ppm/17.7 ppm at 30 °C/80 °C, respectively. These results are 4.4/4.7 ppm lower than that supplied by a world famous quartz sands supplier, and the leaching conditions are much milder compared with other comparable methods: the concentration of hydrogen chloride in the mixed acid is only 10% of the others, the leaching temperature is much lower; at the same time, the operating time is only 13-20% of the others, thereby pollution of industrial strong acids and thermo-scattering is reduced substantially.


Assuntos
Quartzo/isolamento & purificação , Ácido Clorídrico/química
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