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2013, Vol. 22, No. 2　Online: 2013-03-20


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Porous V₂O₅-SnO₂/CNTs composites have been stepwise synthesized by a hydrothermal treatment and a subsequent heat treatment in air. The cyclic capacity and rate capability of the composite cathode have been greatly improved via decreasing the particle size and coating with more conductive material, as compared to the commercial V₂O₅. See the article on Pages 347–355.

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Perspective

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A perspective on carbon materials for future energy application Dang Sheng Su, Gabriele Centi 2013, 22(2): 151-173.  摘要 ( 12758 )   Nanocarbon materials play a critical role in the development of new or improved technologies and devices for sustainable production and use of renewable energy. This perspective paper defines some of the trends and outlooks in this exciting area, with the effort of evidencing some of the possibilities offered from the growing level of knowledge, as testified from the exponentially rising number of publications, and putting bases for a more rational design of these nanomaterials. The basic members of the new carbon family are fullerene, graphene, and carbon nanotube. Derived from them are carbon quantum dots, nanohorn, nanofiber, nano ribbon, nanocapsulate, nanocage and other nanomorphologies. Second generation nanocarbons are those which have been modified by surface functionalization or doping with heteroatoms to create specific tailored properties. The third generation of nanocarbons is the nanoarchitectured supramolecular hybrids or composites of the first and second generation nanocarbons, or with organic or inorganic species. The advantages of the new carbon materials, relating to the field of sustainable energy, are discussed, evidencing the unique properties that they offer for developing next generation solar devices and energy storage solutions.

Reviews

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Role of carbon matrix heteroatoms at synthesis of carbons for catalysis and energy applications Volodymyr V. Strelko 2013, 22(2): 174-182.  摘要 ( 7964 )   The conceptual ideas about the positive effects of N- and O-heteroatoms on the reactivity of carbons in gasification processes, their catalytic activity in electron transfer reactions, as well as the performance of the electrode double-layer supercapacitors due to their electron-donating influence on the π-conjugated system of graphene layers have been developed. This influence decreases both work function and band gap of carbons, and also significantly affects their electron-donating properties. As a result of our investigations based on quantum chemical calculations of model graphene clusters with N- and O-heteroatoms in different positions, prognostic data have been obtained. These data have been confirmed by our experimental results of catalytic activity of corresponding carbons in H2O2 decomposition reaction, their reactivity in gasification processes, and also their performance as electrodes in supercapacitors.

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Important roles of graphene edges in carbon-based energy storage devices Yoong Ahm Kim, Takuya Hayashi, Jin Hee Kim, Morinobu Endo 2013, 22(2): 183-194.  摘要 ( 9682 )   Nanostructured carbon materials, including carbon nanotubes, graphene and nanoporous carbon, show promise for expanding renewable energy. In particular, the configuration and electronic properties of graphene edges in relation with their electrochemical activity have become a major issue in carbon-based energy storage devices. Here, we review recent results concerning the important roles of graphene edges as the gateway for lithium ion intercalation in the anode of lithium-ion batteries, as promoters of high capacitance in carbon-based supercapacitors, and as anchoring sites for Pt nanoparticles in fuel cells. We envisage that the controlled synthesis of a specific, clean, and stable edge configuration could be achieved to maximize the electrochemical performance of nanostructured carbon-based energy storage devices.

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Synthesis and functionalization of carbon xerogels to be used as supports for fuel cell catalysts José L. Figueiredo, Manuel F. R. Pereira 2013, 22(2): 195-201.  摘要 ( 10486 )   The synthesis and properties of carbon xerogels are briefly described in this mini-review, emphasizing the methods used for tuning their surface chemistry and textural properties in order to design efficient electrocatalysts for fuel cells. In particular, the role played by the surface functional groups in determining the loading, dispersion, oxidation state and stability of the metal phases is addressed.

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Electrocatalytic conversion of CO2 to liquid fuels using nanocarbon-based electrodes Chiara Genovese, Claudio Ampelli, Siglinda Perathoner, Gabriele Centi 2013, 22(2): 202-213.  摘要 ( 8825 )   Recent advances on the use of nanocarbon-based electrodes for the electrocatalytic conversion of gaseous streams of CO2 to liquid fuels are discussed in this perspective paper. A novel gas-phase electrocatalytic cell, different from the typical electrochemical systems working in liquid phase, was developed. There are several advantages to work in gas phase, e.g. no need to recover the products from a liquid phase and no problems of CO2 solubility, etc. Operating under these conditions and using electrodes based on metal nanoparticles supported over carbon nanotube (CNT) type materials, long C-chain products (in particular isopropanol under optimized conditions, but also hydrocarbons up to C8-C9) were obtained from the reduction of CO2. Pt-CNT are more stable and give in some cases a higher productivity, but Fe-CNT, particular using N-doped carbon nanotubes, give excellent properties and are preferable to noble-metal-based electrocatalysts for the lower cost. The control of the localization of metal particles at the inner or outer surface of CNT is an importact factor for the product distribution. The nature of the nanocarbon substrate also plays a relevant role in enhancing the productivity and tuning the selectivity towards long C-chain products. The electrodes for the electrocatalytic conversion of CO2 are part of a photoelectrocatalytic (PEC) solar cell concept, aimed to develop knowledge for the new generation artificial leaf-type solar cells which can use sunlight and water to convert CO2 to fuels and chemicals. The CO2 reduction to liquid fuels by solar energy is a good attempt to introduce renewables into the existing energy and chemical infrastructures, having a higher energy density and easier transport/storage than other competing solutions (i.e. H2).

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Functional porous carbon-based composite electrode materials for lithium secondary batteries Kai Zhang, Zhe Hu, Jun Chen 2013, 22(2): 214-225.  摘要 ( 8914 )   The synthetic routes of porous carbons and the applications of the functional porous carbon-based composite electrode materials for lithium secondary batteries are reviewed. The synthetic methods have made great breakthroughs to control the pore size and volume, wall thickness, surface area, and connectivity of porous carbons, which result in the development of functional porous carbon-based composite electrode materials. The effects of porous carbons on the electrochemical properties are further discussed. The porous carbons as ideal matrixes to incorporate active materials make a great improvement on the electrochemical properties because of high surface area and pore volume, excellent electronic conductivity, and strong adsorption capacity. Large numbers of the composite electrode materials have been used for the devices of electrochemical energy conversion and storage, such as lithium-ion batteries (LIBs), Li-S batteries, and Li-O2 batteries. It is believed that functional porous carbon-based composite electrode materials will continuously contribute to the field of lithium secondary batteries.

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Carbon/carbon supercapacitors Elzbieta Frackowiak, Qamar Abbas, François Béguin 2013, 22(2): 226-240.  摘要 ( 8162 )   Supercapacitors, or electrochemical capacitors, are a power storage system applied for harvesting energy and delivering pulses during short periods of time. The commercially available technology is based on charging an electrical double-layer (EDL), and using high surface area carbon electrodes in an organic electrolyte. This review first presents the state-of-the-art on EDL capacitors, with the objective to better understand their operating principles and to improve their performance. In particular, it is shown that capacitance might be enhanced for carbons having subnanometric pores where ions of the electrolyte are distorted and partly desolvated. Then, strategies for using environment friendly aqueous electrolytes are presented. In this case, the capacitance can be enhanced through pseudo-faradaic contributions involving i) surface functional groups on carbons, ii) hydrogen electrosorption, and iii) redox reactions at the electrode/electrolyte interface. The most promising system is based on the use of aqueous alkali sulfate as electrolyte allowing voltages as high as 2 V to be reached, due to the high overpotential for di-hydrogen evolution at the negative electrode.

Communication

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Efficient conversion of fructose to 5-hydroxymethylfurfural over sulfated porous carbon catalyst Liang Wang, Jian Zhang, Longfeng Zhu, Xiangju Meng, Feng-Shou Xiao 2013, 22(2): 241-244.  摘要 ( 7906 )   Sulfated porous carbon (PC-SO3H) catalyst was successfully synthesized from one-pot treatment of porous polydivinylbenzene in H2SO4 at 250 ℃, which exhibited very good catalytic performances in the production of 5-hydroxymethylfurfural from fructose.

Articles

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Synthesis of SAPO-34/graphite composites for low temperature heat adsorption pumps L. Bonaccorsi, L. Calabrese, E. Proverbio, A. Frazzica, A. Freni, G. Restuccia, E. Piperopoulos, C. Milone 2013, 22(2): 245-250.  摘要 ( 7881 )   Low temperature heat adsorption pumps represent the innovative cooling systems, where cold is generated through adsorption/desorption cycle of water by a suitable adsorbent with good adsorption and high thermal conductive properties. In this work, the hydrothermal synthesis of zeolite SAPO-34 on thermal conductive graphitic supports, aiming at the development of highly performing adsorbent materials, is reported. The synthesis was carried out using as-received and oxidized commercial carbon papers, and graphite plate. Composites were characterized by XRD, SEM and also by a thermogravimetric method, using a Cahn microbalance. The water adsorbing capacity showed typical S-shape trend and the maximum water loading was around 25 wt%, a value close to water adsorption capability of pure SAPO-34. These results are very promising for their application in heat adsorption pumps.

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Facile filling of metal particles in small carbon nanotubes for catalysis Hongbo Zhang, Xiulian Pan, Xinhe Bao 2013, 22(2): 251-256.  摘要 ( 8115 )   A versatile wet chemistry method is developed for filling of subnanometer sized metal particles in carbon nanotubes with a diameter smaller than 1.5 nm. As an example, we showed that a confined bi-component Pd-V catalyst exhibit a higher benzene hydroxylation activity compared with that within multi-walled carbon nanotubes.

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Stability and activity of carbon nanofiber-supported catalysts in the aqueous phase reforming of ethylene glycol T. van Haasterecht, C. C. I. Ludding, K. P. de Jong, J. H. Bitter 2013, 22(2): 257-269.  摘要 ( 9479 )   Nickel, cobalt, copper and platinum nanoparticles supported on carbon nano-fibers were evaluated with respect to their stability, catalytic activity and selectivity in the aqueous phase reforming of ethylene glycol (230 ℃, autogenous pressure, batch reactor). The initial surface-specific activities for ethylene glycol reforming were in a similar range but decreased in the order of Pt (15.5 h-1)>Co(13.0 h-1)>Ni(5.2 h-1) while the Cu catalyst only showed low dehydrogenation activity. The hydrogen molar selectivity decreased in the order of Pt (53%)>Co(21%)>Ni (15%) as a result of the production of methane over the latter two catalysts. Over the Co catalyst acids were formed in the liquid phase while alcohols were formed over Ni and Pt. Due to the low pH of the reaction mixture, especially in the case of Co (as a result of the formed acids), significant cobalt leaching occurs which resulted in a rapid deactivation of this catalyst. Investigations of the spent catalysts with various techniques showed that metal particle growth is responsible for the deactivation of the Pt and Ni catalysts. In addition, coking might also contribute to the deactivation of the Ni catalyst.

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A correlation between structural changes in a Ni-Cu catalyst during decomposition of ethylene/ammonia mixture and properties of nitrogen-doped carbon nanofibers O. Yu. Podyacheva, A. N. Shmakov, A. I. Boronin, L. S. Kibis, S. V. Koscheev, E. Yu. Gerasimov, Z. R. Ismagilov 2013, 22(2): 270-278.  摘要 ( 8593 )   Changes of a 65Ni25Cu10Al2O3 catalyst consisting of Ni-enriched and Cu-enriched alloys were investigated in the bulk and on the surface during the growth of nitrogen-doped carbon nanofibers (N-CNFs) by decomposition of a 50%C2H4/50%NH3 mixture using in situ X-ray diffraction (XRD) analysis, ex situ X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) techniques. It was shown that N-CNF growth at 450-650 ℃ is accompanied by dissolution of carbon and nitrogen in the Ni-enriched alloy, whereas Cu-enriched alloy remains inactive. A correlation between nickel and copper surface concentrations and properties of N-CNFs in relation to the nitrogen content was found. It was demonstrated that phase composition of the catalyst during N-CNF growth determines the type of N-CNFs structure.

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Carbon nanotubes decorated α-Al2O3 containing cobalt nanoparticles for Fischer-Tropsch reaction Yuefeng Liu, Thierry Dintzer, Ovidiu Ersen, Cuong Pham-Huu 2013, 22(2): 279-289.  摘要 ( 9190 )   A new hierarchical composite consisted of multi-walled carbon nanotubes (CNTs) layer anchored on macroscopic α-Al2O3 host matrix was synthesized and used as support for Fischer-Tropsch synthesis (FTS). The composite constituted by a thin shell of a homogeneous, highly entangled and structure-opened carbon nanotubes network and it exhibited a relatively high and fully accessible specific surface area of 76 m2·g-1, compared with that of 5 m2·g-1 of the original α-Al2O3support. The metal-support interaction between carbon nanotubes surface and cobalt precursor and high effective surface area led to a relatively high dispersion of cobalt nanoparticles. This hierarchically supported cobalt catalyst exhibited a high FTS activity along with an extremely high selectivity towards liquid hydrocarbons compared with the cobalt-based catalyst supported on pristine α-Al2O3 or on CNTs carriers. This improvement can attribute to the high accessibility of composite surface area comparing with the macroscopic host structure alone or to the bulk CNTs where the nanoscopic dimension induced a dense packing with low mass transfer which favoured the problem of reactants competitive diffusion towards the cobalt active site. In addition, intrinsic thermal conductivity of decorated CNTs could help the heat dissipating throughout the catalyst body, thus avoiding the formation of local hot spots which appeared in high CO conversion under pure syngas feed in FTS reaction. Cobalt supported on CNTs decorated α-Al2O3 catalyst also exhibited satisfied high stability during more than 200 h on stream under relatively severe conditions compared with other catalysts reported in the literature. Finally, the macroscopic shape of such composite easily rendered its usage as catalyst support in a fixed-bed configuration without facing problems of transport and pressure drop as encountered with the bulk CNTs.

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Simultaneous formation of sorbitol and gluconic acid from cellobiose using carbon-supported ruthenium catalysts Tasuku Komanoya, Hirokazu Kobayashi, Kenji Hara, Wang-Jae Chun, Atsushi Fukuoka 2013, 22(2): 290-295.  摘要 ( 6652 )   A carbon-supported Ru catalyst, Ru/BP2000, is able to simultaneously convert cellobiose into sorbitol and gluconic acid. This reaction occurs as the result of hydrolytic disproportionation in water at 393 K under an Ar atmosphere, without bases or sacrificial reagents. In-situ XANES measurements suggest that the active Ru species involved is composed of partially oxidized Ru metal.

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Synergistic effect between few layer graphene and carbon nanotube supports for palladium catalyzing electrochemical oxidation of alcohols Bruno F. Machado, Andrea Marchionni, Revathi R. Bacsa, Marco Bellini, Julien Beausoleil, Werner Oberhauser, Francesco Vizza, Philippe Serp 2013, 22(2): 296-304.  摘要 ( 8589 )   Few layer graphene (FLG), multi-walled carbon nanotubes (CNTs) and a nanotube-graphene composite (CNT-FLG) were used as supports for palladium nanoparticles. The catalysts, which were characterized by transmission electron microscopy, Raman spectroscopy and X-ray diffraction, were used as anodes in the electrooxidation of ethanol, ethylene glycol and glycerol in half cells and in passive direct ethanol fuel cells. Upon Pd deposition, a stronger interaction was found to occur between the metal and the nanotube-graphene composite and the particle size was significantly smaller in this material (6.3 nm), comparing with nanotubes and graphene alone (8 and 8.4 nm, respectively). Cyclic voltammetry experiments conducted with Pd/CNT, Pd/FLG and Pd/CNT-FLG in 10 wt% ethanol and 2 M KOH solution, showed high specific currents of 1.48, 2.29 and 2.51 mA·μgPd-1, respectively. Moreover, the results obtained for ethylene glycol and glycerol oxidation highlighted the excellent electrocatalytic activity of Pd/CNT-FLG in terms of peak current density (up to 3.70 mA·μgPd-1 for ethylene glycol and 1.84 mA·μgPd-1 for glycerol, respectively). Accordingly, Pd/CNT-FLG can be considered as the best performing one among the electrocatalysts ever reported for ethylene glycol oxidation, especially considering the low metal loading used in this work. Direct ethanol fuel cells at room temperature were studied by obtaining power density curves and undertaking galvanostatic experiments. The power density outputs using Pd/CNT, Pd/FLG and Pd/CNT-FLG were 12.1, 16.3 and 18.4 mW·cm-2, respectively. A remarkable activity for ethanol electrooxidation was shown by Pd/CNT-FLG anode catalyst. In a constant current experiment, the direct ethanol fuel cell containing Pd/CNT-FLG could continuously deliver 20 mA·cm-2 for 9.5 h during the conversion of ethanol into acetate of 30%, and the energy released from the cell was about 574 J.

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Phosphorylated mesoporous carbon as effective catalyst for the selective fructose dehydration to HMF A. Villa, M. Schiavoni, P. F. Fulvio, S. M. Mahurin, S. Dai, R. T. Mayes, G. M. Veith, L. Prati 2013, 22(2): 305-311.  摘要 ( 7143 )   Phosphorylated mesoporous carbons (PMCs) were investigated as catalysts in the dehydration of fructose to hydroxymethylfurfural (HMF). The acidic PMCs show better selectivity to HMF compared to sulfonated carbon catalyst (SC) despite lower activity. The concentration of P-O groups on the PMC was correlated with the activity/selectivity of the catalysts; the higher the P-O concentration, the higher the activity. However, the higher the P-O content, the lower the selectivity to HMF. Indeed, a lower concentration of the P-O groups minimized the degradation of HMF to levulinic acid and the formation of by-products, such as humines. Stability tests showed that these systems deactivate due to the formation of humines and water insoluble by-products derived from the dehydration of fructose which blocked the catalytically active sites.

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Purified oxygen- and nitrogen-modified multi-walled carbon nanotubes as metal-free catalysts for selective olefin hydrogenation Peirong Chen, Ly May Chew, Aleksander Kostka, Kunpeng Xie, Martin Muhler, Wei Xia 2013, 22(2): 312-320.  摘要 ( 8209 )   Oxygen- and nitrogen-functionalized carbon nanotubes (OCNTs and NCNTs) were applied as metal-free catalysts in selective olefin hydrogenation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.

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Ru particle size effect in Ru/CNT-catalyzed Fischer-Tropsch synthesis Jincan Kang, Weiping Deng, Qinghong Zhang, Ye Wang 2013, 22(2): 321-328.  摘要 ( 11059 )   Carbon nanotube (CNT)-supported Ru nanoparticles with mean sizes ranging from 2.3 to 9.2 nm were prepared by different post-treatments and studied for Fischer-Tropsch (FT) synthesis. The effects of Ru particle size on catalytic behaviors were investigated at both shorter and longer contact times. At shorter contact time, where the secondary reactions were insignificant, the turnover frequency (TOF) for CO conversion was dependent on the mean size of Ru particles; TOF increased with the mean size of Ru particles from 2.3 to 6.3 nm and then decreased slightly. At the same time, the selectivities to C5+ hydrocarbons increased gradually with the mean size of Ru particles up to 6.3 nm and then kept almost unchanged with a further increase in Ru particle size. At longer contact time, C10-C20 selectivity increased significantly at the expense of C21+ selectivity, suggesting the occurrence of the selective hydrocracking of C21+ to C10-C20 hydrocarbons.

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Ammonia-treatment assisted fully encapsulation of Fe2O3 nanoparticles in mesoporous carbons as stable anodes for lithium ion batteries Fei Han, Wen-Cui Li, Duo Li, An-Hui Lu 2013, 22(2): 329-335.  摘要 ( 7401 )   To improve the initial coulombic efficiency and bulk density of ordered mesoporous carbons, active Fe2O3 nanoparticles were introduced into tubular mesopore channels of CMK-5 carbon, which possesses high specific surface area (>1700 m2穏-1) and large pore volume (>1.8 cm3穏-1). Fine Fe2O3 nanoparticles with sizes in the range of 5-7 nm were highly and homogenously encapsulated into CMK-5 matrix through ammonia-treatment and subsequent pyrolysis method. The Fe2O3 loading was carefully tailored and designed to warrant a high Fe2O3 content and adequate buffer space for improving the electrochemical performance. In particular, such Fe2O3 and mesoporous carbon composite with 47 wt% loading exhibits a considerably stable cycle performance (683 mAh穏-1 after 100 cycles, 99% capacity retention against that of the second cycle) as well as good rate capability. The fabrication strategy can effectively solve the drawback of single material, and achieve a high-performance lithium electrode material.

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Enhanced reversible capacity of Li-S battery cathode based on graphene oxide Jin Won Kim, Joey D. Ocon, Dong-Won Park, Jaeyoung Lee 2013, 22(2): 336-340.  摘要 ( 7457 )   Lithium sulfur battery (LSB) offers several advantages such as very high energy density, low-cost, and environmental-friendliness. However, it suffers from serious degradation of its reversible capacity because of the dissolution of reaction intermediates, lithium polysulfides, into the electrolyte. To solve this limitation, there are many studies using graphene-based materials due to their excellent mechanical strength and high conductivity. Compared with graphene, graphene oxide (GO) contains various oxygen functional groups, which enhance the reaction with lithium polysulfides. Here, we investigated the positive effect of using GO mixed with carbon black on the performance of cathode in LSB. We have observed a smaller drop of capacity in GO mixed sulfur cathode. We further demonstrate that the mechanistic origin of reversibility improvement, as confirmed through CV and Raman spectra, can be explained by the stabilization of sulfur in lithium polysulfide intermediates by oxygen functional groups of GO to prevent dissolution. Our findings suggest that the use of graphene oxide-based cathode is a promising route to significantly improve the reversibility of current LSB.

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Hierarchical nanostructured composite cathode with carbon nanotubes as conductive scaffold for lithium-sulfur batteries Xiaofei Liu, Qiang Zhang, Jiaqi Huang, Shumao Zhang, Hongjie Peng, Fei Wei 2013, 22(2): 341-346.  摘要 ( 10041 )   Carbon nanotubes (CNTs) are excellent scaffolds for advanced electrode materials, resulting from their intrinsic sp2 carbon hybridization, interconnected electron pathway, large aspect ratio, hierarchical porous structures, and low cost at a large-scale production. How to make full utilization of the mass produced CNTs as building blocks for nanocomposite electrodes is not well understood yet. Herein, a composite cathode containing commercial agglomerated multi-walled CNTs and S for Li-S battery was fabricated by a facile melt-diffusion strategy. The hierarchical CNT@S coaxial nanocables exhibited a discharging capacity of 1020 and 740 mAh穏-1 at 0.5 and 2.0 C, respectively. A rapid capacity decay of 0.7% per cycle at the initial 10 cycles and a slow decay rate of 0.14% per cycle for the later 140 cycles were detected. Such hierarchical agglomerated CNT@S cathodes show advantages in easy fabrication, environmentally benign, low cost, excellent scalability, and good Li ion storage performance, which are extraordinary composites for high performance Li-S battery.

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Porous V2O5-SnO2/CNTs composites as high performance cathode materials for lithium-ion batteries Qi Guo, Zhenhua Sun, Man Gao, Zhi Tan, Bingsen Zhang, Dang Sheng Su 2013, 22(2): 347-355.  摘要 ( 9312 )   Vanadium pentoxide (V2O5) exhibits high theoretical capacities when used as a cathode in lithium ion batteries (LIBs), but its application is limited by its structural instability as well as its low lithium and electronic conductivities. A porous composite of V2O5-SnO2/carbon nanotubes (CNTs) was prepared by a hydrothermal method and followed by thermal treatment. The small particles of V2O5, their porous structure and the coexistence of SnO2 and CNTs can all facilitate the diffusion rates of the electrons and lithium ions. Electrochemical impedance spectra indicated higher ionic and electric conductivities, as compared to commercial V2O5. The V2O5-SnO2/CNTs composite gave a reversible discharge capacity of 198 mAh穏-1 at the voltage range of 2.05-4.0 V, measured at a current rate of 200 mA穏-1, while that of the commercial V2O5 was only 88 mAh穏-1, demonstrating that the porous V2O5-SnO2/CNTs composite is a promising candidate for high-performance lithium secondary batteries.