2014 Vol. 29, No. 4

2014, 29(4)
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2014, 29(4)
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2014, 29(4)
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Review of carbon materials for advanced lithium-sulfur batteries
ZHANG Qiang, CHENG Xin-bing, HUANG Jia-qi, PENG Hong-jie, WEI Fei
2014, 29(4): 241-264.
Abstract(2073) PDF(1112)
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Lithium-ion batteries (LIBs) are extensively used in numerous portable devices such as smart-phones and laptops. However, current LIBs based on the conventional intercalation mechanism cannot meet the requirements of the electronics industry and electric vehicles although they are approaching their theoretical capacity. Therefore, it is extremely urgent to seek for systems with higher energy densities. Among various promising candidates, lithium-sulfur (Li-S) batteries with a high theoretical capacity are very attractive. However, the commercial use of Li-S batteries still faces obstacles such as the low electrical conductivity of sul-batteries sheds light on the efficient utilization of sulfur by improving the conductivity of the composites and restraining the shuttle effect of polysulfides. Here, we give a brief review of recent progress on carbon / sulfur composites, especially carbon nanotube, graphene and porous carbon-based hybrids, new insights on the relationships between the structure and the electrochemical performance, and propose some important aspects for the future development of Li-S batteries.
Carbon-based material for a lithium-air battery
WEI Wei, WANG Da-wei, YANG Quan-hong
2014, 29(4): 265-271.
Abstract(806) PDF(1554)
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Carbon-based materials are important in energy storage and conversion materials, because of their different possible morphologies and superior performance. We discuss relationships between the structure and properties of carbon-based materials as the cathode of the lithium-air battery, discuss the importance of structure design and performance control, specify the research priori- ties for carbon-based materials for lithium-air batteries, and explore the potential applications of carbon-based materials in lithium-air batteries.
A review of the electrochemical activity of carbon materials in vanadium redox flow batteries
WEI Guan-Jie, FAN Xin-Peng, LIU Jian-Guo, YAN Chuan-Wei
2014, 29(4): 272-279.
Abstract(1073) PDF(1261)
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Carbon materials mainly act as the electrode in a vanadium redox flow battery (VRFB). Due to the poor electrochemical activity of traditional carbon materials for vanadium redox reactions, a comprehensive study of the electrochemical activity of carbon materials, especially graphite felt (GF), is greatly needed and has become an important feature of electrode research. This paper presents research progress on carbon materials for use in a VRFB, focusing on modifying the GF and new carbons as catalysts for vanadium redox reactions. The electrocatalytic influence of surface oxygen and nitrogen functional groups on vanadium redox reactions is introduced. The use of carbon nanotubes and graphene in a VRFB is discussed and future trends to improve the electrochemical activity of carbon materials are highlighted.
Nitrogen-doped mesoporous carbon nanosheets from coal tar as high performance anode materials for lithium ion batteries
WANG Hao-qiang, ZHAO Zong-bin, CHEN Meng, XIAO Nan, LI Bei-bei, QIU Jie-shan
2014, 29(4): 280-286.
Abstract(886) PDF(786)
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Nitrogen-doped mesoporous carbon nanosheets (NMCNs) were prepared from coal tar and melamine using a layered MgO as template. Porous structures and nitrogen doping levels were readily tuned by adjusting experimental parameters. NMCNs show high specific capacities and excellent cyclic stabilities as anode materials for lithium ion batteries. A sample prepared under optimum conditions shows a high reversible capacity of nearly 1 000 mAh / g at a current density of 100 mA / g, which can be ascribed to its unique mesoporous sheet-structure, a high specific surface area of 1 209 m2 / g, and a uniform and high bulk nitrogen content of 8. 6% . Our work demonstrates that coal tar can act as an excellent carbon source for the production of carbon materials with high performance in lithium-ion batteries.
Carbon nanotube-modified LiFePO4 for high rate lithium ion batteries
LUO Wen-bin, WEN Lei1, LUO Hong-ze, SONG Ren-sheng, ZHAI Yu-chun, LIU Chang, Li Fen
2014, 29(4): 287-294.
Abstract(977) PDF(813)
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A hybrid cathode material for high rate lithium ion batteries was prepared by ball-milling and spray drying a slurry containing LiFePO4 nanoparticles, glucose and carbon nanotubes (CNTs) in water, followed by pyrolysis at 600 for 6 h under a gas mixture of 5% H2 in Ar. CNTs with a large aspect ratio form a continuous conductive network connecting the LiFePO4 nanoparticles and amorphous carbon, which significantly reduces the electrical resistance of the cathode. The hybrid material can deliver a specific capacity of 99 mAh / g at a 50 C charge / discharge rate. An excellent cycling performance was also demonstrated, with a capacity loss of less than 10% after 450 cycles at a 10 C rate.
LI Yao-Hai, LV Chun-Xiang
2014, 29(4): 295-300.
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Morphology-controlled synthesis of Fe3 O4 / carbon nanostructures for lithium ion batteries
DENG Hong-Gui, JIN Shuang-Ling, DAN Yao-Liang, JIN Ming-Lin, LING Li-Cheng
2014, 29(4): 301-308. doi: 10.1016/S1872-5805(14)60139-6
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Morphology-controlled Fe3 O4 / carbon nanocomposites were synthesized by a solvothermal reaction followed by calcination under a nitrogen atmosphere. Flower-like structures, dispersed nanoflakes and hollow microspheres could be readily obtained by adjusting the concentrations of the reactants. Based on the time dependent structure evolution, a possible mechanism for the formation of the different morphologies under various conditions was discussed. The lithium storage properties of the different Fe3 O4 / carbon composites were compared. The flower-like sample shows the best electrochemical performance with the highest specific capacity of 227mAh / g at a current rate of 5 C while hollow microspheres and dispersed nanoflakes have specific capacities of only 45 and 10mAh / g, respectively.
Preparation and electrochemical performance of a graphene-wrapped carbon / sulphur composite cathode
LI Fang-Fei, Lv Wei, NIU Shu-Zhang, LI Bao-Hua
2014, 29(4): 309-315. doi: 10.1016/S1872-5805(14)60140-2
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Graphene is used as a barrier film to suppress the “shuttle effect ”and to improve the performance of activated carbon-sulphur hybrid cathode materials in a lithium-sulphur battery by forming a core-shell structure. Graphene wraps around the activated carbon-sulphur hybrid to form a core-shell structure, in which the porous carbon framework stores most of the sulphur and the graphene layer suppresses the movement of the soluble polysulfide in the electrolyte during charge-discharge, resulting in an improvement of capacity and cyclic stability during long-term cycling. Such a core-shell structure is formed by changing the hydrophilicity of graphene oxide during reduction, in which the hydrophobic graphene closely wraps around the hydrophobic carbon surface.
Easy synthesis of MnO-graphene hybrids for high-performance lithium storage
GAO Feng, QU Jiang-ying, ZHAO Zong-bin, DONG Yan-feng, YANG Juan, DONG Qiang, QIU Jie
2014, 29(4): 316-321. doi: 10.1016/ S1872-5805(14)60141-4
Abstract(751) PDF(1157)
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Graphene oxide was produced using a modified Hummers method and used to produce a MnSO4 -graphene oxide (MnSO4-GO) hybrid which was then transformed into a MnO-graphene hybrid by precipitation with NaOH followed by hydrogen reduction. The MnO-graphene hybrid shows a high specific capacity of 870 mAh·g-1 at 100 mA·g-1 as an anode material for lithium ion batteries, which is much higher than that of bare MnO (around 456 mAh·g-1 ). A capacity of 390 mAh·g-1 could be maintained even at a high current density of 1 600 mA·g-1 . This green and highly efficient approach offers a new technique for the synthesis of MnOx-graphene battery materials.
Performance of lithium ion batteries using a carbon nanotube film as a cathode current collector
ZHONG Cheng-Wen, HU Jing-Wei, TUN Zi-Beng, MEI Wen-Cha
2014, 29(4): 322-328.
Abstract(1087) PDF(1113)
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A carbon nanotube (CNT) film was used as the current collector and LiCoO2 as the cathode for a lithium ion battery. The battery showed a high initial discharge capacity of 132. 8 mAh·g-1 , a high retention rate of over 80% after 500 cycles under 1C and a low self-discharge rate of 1. 5% . When the areal density of the CNT film is 16 mg·cm-2 , the energy density of the LiCoO2 -CNT battery is 25% larger than that of a LiCoO2-Al battery. The superior properties of the battery may be attributed to the high electrochemical stability of the graphitic structure of CNTs and the porous surface of the CNT film that ensures a high contact surface area between the current collector and the cathode material. The CNT film is promising as a new current collector for lithium ion batteries. Macroscopical carbon nanotubes (CNTs) was studied as current collector for lithium ion battery. LiCoO2 was used as active substance. The prepared battery showed high first special discharge capacity (132. 8mAh·g-1 ) and retention rate (over 80% ) after 500 cycles under 1C. When the areal density of cathode layer is 16mg cm-2 , energy density of LiCoO2 -CNT battery is 25% larger than that of LiCoO2 -Al battery. Meanwhile, the battery with CNTs film as current collector has low self-discharge rate (1. 5% ). The superior properties of the battery maybe attribute to graphite structure even underwent current and porous surface of the CNTs film. The characteristic of the surface ensures the cathode to contact with CNTs film tightly. Considering the stable and outstanding properties , the CNTs film is expected to be a new current collector for lithium ion battery
A brief overview of the International Forum on Graphene 2014
LU Wei, ZHENG Xiao-Yu, KANG Fei-Yu
2014, 29(4)
Abstract(630) PDF(1106)
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The International Forum on Graphene 2014 was held in the Graduate School at Shenzhen, Tsinghua University, Shenzhen, China from May 18 to 21, 2014. It was organised by the China Association for Science and Technology (CAST) with the support of the National Natural Science Foundation of China, the Chinese Materials Research Society, Shenzhen Science and Technology Association and the Science & Technology Innovation Committee of Shenzhen. Graduate School at Shenzhen, Tsinghua University and the Institute of Metal Research, Chinese Academy of Sciences. In this forum, twenty outstanding scientists (10 from abroad and 10 from China) presented their recent research and opinions on future developments on graphene and related carbon materials. More than two hundred people attended. Twenty presentations, including one plenary presentation by Professor Andre Geim, the Nobel Prize winner, ten keynote talks and nine invited presentations, were given. The forum included six topics: fundamentals of graphene and other two-dimensional materials, controlled growth and mass production, unique physical and chemical properties, advanced applications of graphene and carbon nanotubes, opportunities and challenges of graphene industrialization, and future markets and developments. Two dialogue sessions were held to promote academic and industrial discussion about graphene materials, and this advocated the future cooperation of China with other counties.