英语原文共 9 页，剩余内容已隐藏，支付完成后下载完整资料

Energy amp; Environmental Science

能源与环境科学

Ultralong single crystalline V2O5 nanowire/graphene composite fabricated by a facile green approach and its lithium storage behavior

简易绿色法制备超长V2O5单晶纳米线/石墨烯复合材料及其储锂性能

A novel hybrid material constructed from 2D graphene nanosheets (GNS) and 1D vanadium pentoxide (V2O5) nanowires was successfully fabricated via a very simple green approach. The ultralong V2O5 single crystalline nanowires were supported on the transparent GNS substrate and exhibited excellent electrochemical properties. When used as a cathode material of lithium-ion batteries, the composite material revealed high initial discharge capacities and exceptional rate capacities. For instance, at the lower current density of 50 mA g1 , an initial specific discharge capacity of 412 mAh g1 could be achieved; when the current density was increased to 1600 mA g1 , the composite still delivered 316 mAh g1 lithium ions. The good performance of the composite resulted from its unique nano-scaled V2O5 wires with short diffusion pathway for lithium ions and the excellent electrical conductivity of GNS. Note that the fabrication approach in the present work is environmental friendly without any strong reduction and oxidation reagents, or causing the generation of toxic gas during the fabrication process. We believe that this green approach may open up the possibility of fabricating more novel structured graphene-based functional materials.

通过一种非常简单的绿色方法，成功地制备了一种由二维石墨烯纳米片（GNS）和一维五氧化二钒（V2O5）纳米线构成的新型杂化材料。超长V2O5单晶纳米线以透明GNS为载体，具有优异的电化学性能。作为锂离子电池的正极材料，该复合材料具有较高的初始放电容量和优异的倍率容量。例如，当电流密度为50ma g^-1时，复合材料的初始比放电容量为412mah g-1；当电流密度增加到1600ma g-1时，复合材料仍能产生316mah g-1锂离子。这种复合材料的优良性能是由于其独特的纳米五氧化二钒丝对锂离子具有较短的扩散路径和良好的导电性能。注意，本工作中的制造方法是对环境友好的，没有任何强还原和氧化试剂，或在制造过程中产生有毒气体。我们相信，这种绿色方法可能为制造更新颖的结构石墨烯基功能材料开辟了可能性。

Introduction

引言

Vanadium pentoxide (V2O5) is one of the most promising candidates for cathode materials in rechargeable lithium-ion batteries (LIBs) due to its typical intercalation structure, low cost, wide existence in nature, and high energy densities.1–5

Because the electrochemical intercalation/de-intercalation of lithium ions into/from V2O5 can occur in a large potential window between 4.0 to 1.5 V vs. Li/Li , the maximum amount of lithium ions up to 3Li for every V2O5 could be intercalated, and thus a high specific discharge capacity of approximately 442 mAh g1 might be theoretically achieved.6 Therefore it is expected that V2O5 as a cathode material may meet the increasing demand of large capacities and high energy densities for the next generation of LIBs.

五氧化二钒（V2O5）具有典型的插层结构、低成本、广泛存在于自然界、高能量密度等优点，是最有希望的锂离子电池（LIBs）正极材料之一。由于锂离子在V2O5中的电化学插层/脱层可以发生在4.0到1.5V的大电位窗口中，相对于Li/Li ，可以插层的锂离子最多为3Li ，因此，理论上可获得约442 mAh g -1的高比放电容量。因此，作为阴极材料的V2O5有望满足下一代锂离子电池对大容量和高能量密度的日益增长的需求。

Since the reversible electrochemical intercalation of lithium ions in V2O5 was first reported by Whittingham in 1975,7 numerous efforts have been made to study its electrochemical properties.8–10 However, the intercalation capacity and rate capacity of V2O5 are greatly restricted in practical applications, owing to its moderate electrical conductivity (102 –103 S cm1 ) 11,12 and quite a low diffusion coefficient of lithium ions (1012–1013 cm2 s1 ).13,14 To improve the diffusion capability of lithium ions in V2O5, the construction of nano-scaled materials is an effective method, because nanomaterials possessing large surface area and short diffusion paths can provide more electrochemically active sites and alleviate the concentration polarization of electrode materials.15,16 Thereby a large number of nano-structured V2O5 materials have been fabricated so far, for example, nanobelts,17 nanowires,18,19 nanorolls,20 nanorods,21 and hollow microspheres.22 In our previous work, centimetrelong V2O5 nanowires were prepared which showed a high initial discharge capacity of 351 mAh g1 at a current density of 50 mA g1 . Nevertheless, it quickly faded to 175 mAh g1 after 20 cycles of charge/discharge testing.23 It seems that the construction of nano-scaled materials of V2O5 is not sufficient to achieve high performance electrode materials.

自1975年Whittingham首次报道锂离子在V2O5中的可逆电化学插层以来，人们对其电化学性能进行了大量研究。然而，V2O5的插层容量和速率容量在实际应用中受到很大限制，由于锂离子具有中等的电导率（10^-2～10^-3Scm^-1）和较低的锂离子扩散系数（10^-12～10^-13cm² s^-1）。为了提高锂离子在五氧化二钒中的扩散能力，纳米材料的制备是一种有效的方法，因为纳米材料具有较大的比表面积和较短的时间扩散路径可以提供更多的电化学活性中心，减轻电极材料的浓度极化。因此，迄今为止已经制备了大量纳米结构的V2O5材料，例如纳米带、纳米线、纳米卷、纳米棒和空心微球。在我们以前的工作中，制备了厘米长的五氧化二钒纳米线，当电流密度为50mA g-1时，其初始放电容量为351mAhg-1。然而，经过20次充放电试验后，它很快就下降到175毫安时g -1。看来，五氧化二钒纳米材料的结构不足以获得高性能的电极材料。

How to improve the electrical conductivity is another important topic for using V2O5 as a cathode material of LIBs. Extensive studies have been carried out to improve the electrical conductivity of V2O5 by conductive carbon modification. For instance, Dunnrsquo;s group incorporated V2O5 aerogels into singlewalled carbon nanotubes and the material exhibited high capacities exceeding 400 mAh g1 at high rate.24 Maier et al. prepared a composite of V2O5 and carbon tube-in-tube (V2O5/ CTIT), where the CTIT served as lsquo;lsquo;electronic wiresrsquo;rsquo; providing the electrons to the active materials, which displayed good electrochemical properties.25 A carbon nanotube (CNT) hybrid with V2O5 nanowires has also been fabricated to enhance the conductivity of V2O5.

如何提高锂离子电池的导电性是五氧化二钒作为锂离子电池正极材料的另一个重要课题。为了提高五氧化二钒的导电性，人们进行了大量的研究。例如，Dunn的研究小组将V2O5气凝胶掺入单壁碳纳米管中，该材料在高速率下表现出超过400 mAh g- 1的高容量。Maier等人制备了V2O5和碳管中管（V2O5/CTIT）的复合材料，CTIT作为“电子线”向活性材料提供电子，显示出良好的电化学性能。还制备了碳纳米管（CNT）与V2O5纳米线的杂化物，以增强V2O5的导电性。

Graphene, macro-molecular sheets of carbon atoms with a honeycomb structure, has opened a new window for utilizing 2D monolayer carbon materials as a conductive support because of its high conductivity (103 –104 S m-1 ), large surface area (ca. 2630 m2 g-1 ), unique graphitized plane str

剩余内容已隐藏，支付完成后下载完整资料

资料编号：[262035]，资料为PDF文档或Word文档，PDF文档可免费转换为Word