SnO2/Graphene Composites with Self-Assembled Alternating Oxide and Amine Layers for High Li-Storage and Excellent Stability
SnO2/Graphene Composites with Self-Assembled Alternating Oxide and Amine Layers for High Li-Storage and Excellent Stability
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DOI：
10.1002/adma.201301264
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发表时间：
2013-06-25
影响因子：
29.4
通讯作者：
Pyo, Myoungho
中科院分区：
文献类型：
--
作者：
Prabakar, S. J. Richard;Hwang, Yun-Hwa;Pyo, Myoungho
二氧化锡/石墨烯是研究最广泛的复合材料之一，作为石墨阳极的有前途的替代品，用于开发具有高能量密度的下一代锂离子电池（LIB）[1]。[2-4]这些复合材料的高锂存储能力是基于这样一个事实，即被石墨烯层包围的纳米 SnO 2 颗粒 [5-13] 可以显着减轻机械应变，否则会因重复使用过程中 Sn 域的破碎和粉碎而导致断电。 [14-21]复合材料中纳米锡域的尺寸稳定性主要归因于石墨烯层的机械缓冲作用。（虽然纳米级制造可以在一定程度上减轻锡的粉化，但通过减小尺寸来完全缓解应力是不可能的，因为临界晶粒尺寸远小于晶胞尺寸，低于该临界晶粒尺寸可以防止锡粉化。[22]）石墨烯层具有高电导率和杨氏模量[23]也可以减轻SnO 2 纳米粒子的聚集，这进一步有助于延长C-D循环期间稳定的容量响应。具有SnO 2 锚定石墨烯(SG)的复合材料通常可以由吸附Sn 2+ (或Sn 4+)的氧化石墨烯(GO)合成。这样，对所制备的SG进行热还原以增强SnO 2 的结晶度和石墨烯(rSG)的电导率。在此步骤中，已知石墨烯层通过 π− π 相互作用重新堆叠，从而为复合材料提供了尺寸完整性。大多数关于rSG 作为阳极的报告都指出，与SnO 2 纳米粒子相比，容量保持率得到了显着提高。例如，Aksay 等人。研究表明，通过自组装方法制备的 rSG 堆栈可以在 10 mA g− 1 的速率下循环 100 次后保留 625 mA hg− 1 的容量。 [24]最近，王等人。报道称，通过络合阴离子堆叠形成制备的 rSG 三明治纸可以显示出增强的容量和循环能力（在 50 mA g−1 下循环 50 次后超过 800 mA hg−1）。 [25]他们声称，rSG 优异的电化学行为归功于 N 掺杂石墨烯和优化的结构特征。在此，我们首次报道了由 Sn 2+ 锚定的 GO 和胺功能化石墨烯 (GN) 交替堆叠制备的 SnO 2/石墨烯复合材料，在长时间的 C-D 循环中对 Li+ 保持了前所未有的高且稳定的可逆能力。带相反电荷的 Sn 2+ 锚定的 GO 和 GN 层自发形成预排列的交替堆叠 (SG/GN)，其在水溶液中厚度为几微米。随后 SG/GN 的热还原产生了组织良好且致密的结构 (r (SG/GN))，由于增强的 π− π 堆积相互作用，孔体积显着减少。与rSG相比，r（SG/GN）具有减少的微介孔和完全消除的大孔，具有高可逆容量和优异的容量保持率（在100 mA g−1的倍率下循环200次后为872 mA hg−1），如图1A中的示意图所示。 GO 是通过使用改进的 Hummer 方法对人造石墨进行化学衍生而制备的。 [26]用于合成 GN 的 GO 含有约能量色散 X 射线光谱 (EDX) 和 X 射线光电子能谱 (XPS) 证实氧含量为 34–35 at%（图 S1，支持信息）。 GO 与 SOCl 2 反应，随后与六亚甲基二胺 (HDA) 反应。这 …
Tin dioxide/graphene is one of the most extensively studied composite materials as a promising alternative to graphite anodes for the development of next-generation Li ion batteries (LIBs)[1] with high energy densities.[2–4] The high Li storage capability of these composites is based on the fact that nanometric SnO 2 particles [5–13] surrounded by graphene layers can substantially relieve mechanical strain, which otherwise causes an electrical disconnection resulting from the crumbling and pulverization of Sn domains during repeated charge–discharge (C–D) cycles.[14–21] The dimensional stability of nanometric Sn domains in the composite has been ascribed mainly to the mechanical cushioning role of the graphene layers.(Although nanoscale fabrication can alleviate the pulverization of Sn to some extent, complete relief of the stress by decreasing the size is impossible because the critical grain size, below which pulverization of the Sn is prevented, is far less than the unit cell size.[22]) The graphene layers, endowed with high conductivity and Young’s modulus [23] can also mitigate the aggregation of SnO 2 nanoparticles, which further contributes to a stable capacity response during extended C–D cycles. A composite with SnO 2-anchored graphene (SG) can be commonly synthesized from Sn 2+(or Sn 4+)-adsorbed graphene oxide (GO). As such, prepared SG is subjected to thermal reduction in order to enhance the crystallinity of SnO 2 and the electrical conductivity of graphene (rSG). During this step, graphene layers are known to be restacked through π− π interactions, which provide the composite with a dimensional integrity. Most reports on rSG as an anode have addressed a substantially improved capacity retention, when compared with SnO 2 nanoparticles. For example, Aksay et al. showed that rSG stacks prepared by a self-assembly approach could retain a capacity of 625 mA hg− 1 after 100 cycles at a rate of 10 mA g− 1.[24] Recently, Wang et al. reported that rSG sandwich paper, prepared by stack formation by complexing anions, could show an enhanced capacity and cyclability (more than 800 mA hg− 1 after 50 cycles at 50 mA g− 1).[25] They claimed that the excellent electrochemical behaviors of rSG were due to N-doped graphene and optimized structural features.Herein, we provide the first report that SnO 2/graphene composites, which is prepared from alternating stacks of Sn 2+-anchored GO and amine-functionalized graphene (GN), maintain an unprecedented degree of high and stable reversible capability for Li+ during prolonged C–D cycles. The oppositely charged Sn 2+-anchored GO and GN layers spontaneously form pre-aligned alternating stacks (SG/GN) that are several micrometers thick in an aqueous solution. A subsequent thermal reduction of SG/GN results in a well-organized and densely packed structure (r (SG/GN)), which shows a significant reduction in pore volume due to enhanced π− π stacking interactions. The r (SG/GN) possessing reduced micro-mesopores and completely eliminated macropores, compared with rSG, results in a high reversible capacity and excellent capacity retention (872 mA hg− 1 after 200 cycles at a rate of 100 mA g− 1), as shown by the schematic illustration in Figure 1A. The GO was prepared by chemically derivatizing artificial graphite using a modified Hummer’s method.[26] The GO utilized for the synthesis of GN contained ca. 34–35 at% of oxygen as confirmed by energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS)(Figure S1, Supporting Information). The GO was reacted with SOCl 2 and subsequently with hexamethylenediamine (HDA). The …