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Hybrid core-shell nanowire electrodes utilizing vertically aligned carbon nanofiber arrays for high-performance energy storage.

机译：混合核-壳纳米线电极利用垂直排列的碳纳米纤维阵列实现高性能储能。

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摘要

Nanostructured electrode materials for electrochemical energy storage systems have been shown to improve both rate performance and capacity retention, while allowing considerably longer cycling lifetime. The nano-architectures provide enhanced kinetics by means of larger surface area, higher porosity, better material interconnectivity, shorter diffusion lengths, and overall mechanical stability. Meanwhile, active materials that once were excluded from use due to bulk property issues are now being examined in new nanoarchitecture.;Silicon was such a material, desired for its large lithium-ion storage capacity of 4,200 mAh g-1 and low redox potential of 0.4 V vs. Li/Li+; however, a ∼300% volume expansion and increased resistivity upon lithiation limited its broader applications. In the first study, the silicon-coated vertically aligned carbon nanofiber (VACNF) array presents a unique core-shell nanowire (NW) architecture that demonstrates both good capacity and high rate performance. In follow-up, the Si-VACNFs NW electrode demonstrates enhanced power rate capabilities as it shows excellent storage capacity at high rates, attributed to the unique nanoneedle structure that high vacuum sputtering produces on the three-dimensional array.;Following silicon's success, titanium dioxide has been explored as an alternative high-rate electrode material by utilizing the dual storage mechanisms of Li+ insertion and pseudocapacitance. The TiO 2-coated VACNFs shows improved electrochemical activity that delivers near theoretical capacity at larger currents due to shorter Li+ diffusion lengths and highly effective electron transport. A unique cell is formed with the Si-coated and TiO2-coated electrodes place counter to one another, creating the hybrid of lithium ion battery-pseudocapacitor that demonstrated both high power and high energy densities. The hybrid cell operates like a battery at lower current rates, achieving larger discharge capacity, while retaining one-third of that capacity as the current is raised by 100-fold. This showcases the VACNF arrays as a solid platform capable of assisting lithium active compounds to achieve high capacity at very high rates, comparable to modern supercapacitors.;Lastly, manganese oxide is explored to demonstrate the high power rate performance that the VACNF array can provide by creating a supercapacitor that is highly effective in cycling at various high current rates, maintaining high-capacity and good cycling performance for thousands of cycles.
机译：已经显示出用于电化学能量存储系统的纳米结构电极材料可以改善速率性能和容量保持率，同时允许更长的循环寿命。纳米结构通过更大的表面积，更高的孔隙率，更好的材料互连性，更短的扩散长度和整体机械稳定性来提供增强的动力学。同时，曾经由于体积特性问题而被淘汰使用的活性材料现在正在新的纳米体系结构中进行研究。硅是这样一种材料，因其具有4,200 mAh g-1的大锂离子存储容量和低的氧化还原电位而需要。 0.4 V vs.Li/Li+;然而，〜300％的体积膨胀和锂化时电阻率的增加限制了其更广泛的应用。在第一个研究中，硅涂层垂直排列的碳纳米纤维（VACNF）阵列展示了独特的核壳纳米线（NW）结构，该结构展示了良好的容量和高倍率性能。在后续工作中，Si-VACNFs NW电极表现出更高的功率速率能力，因为它在高倍率下显示出出色的存储容量，这归因于高真空溅射在三维阵列上产生的独特纳米针结构;继硅的成功之后，钛通过利用Li +插入和假电容的双重存储机制，已将二氧化碳作为替代的高速率电极材料进行了研究。涂有TiO 2的VACNFs显示出改善的电化学活性，由于较短的Li +扩散长度和高效的电子传输，可在较大电流下提供接近理论容量的性能。形成一个独特的电池，其硅涂层电极和TiO2涂层电极彼此相对放置，从而形成了锂离子电池-伪电容器的混合体，既显示了高功率密度又显示了高能量密度。混合动力电池像电池一样以较低的电流速率工作，从而实现了更大的放电容量，同时随着电流增加100倍而保留了该容量的三分之一。这展示了VACNF阵列作为一个固态平台，能够协助锂活性化合物以非常高的速率实现高容量，这与现代超级电容器相当。最后，探索了氧化锰以展示VACNF阵列可以提供的高功率速率性能。创造了一种超级电容器，可以在各种高电流速率下高效循环，可在数千个循环中保持高容量和良好的循环性能。

著录项

  • 作者

    Klankowski, Steven Arnold.;

  • 作者单位

    Kansas State University.;

  • 授予单位 Kansas State University.;
  • 学科 Energy.;Materials science.;Chemistry.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 176 p.
  • 总页数 176
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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