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柔性透明的超级电容器-- 可以像扑克一样来弯曲它

已有 8157 次阅读 2009-5-25 17:40 |系统分类:科研笔记|关键词:学者

[今天才看到原来这篇文章也被很多媒体报道了。一篇我在美国时的合作论文,我是第二作者,第一作者是实验室的一个来自台湾的博士生,这篇文章中的器件原型所用的转移到PET上的碳纳米管薄膜基本都是我做的,我完成了第一步后,那个博士生负责进行器件封装,然后我们进行相关测试工作。当时为了把器件做好看一些,着实花了不少力气(先用AAO滤碳管,然后转移到PDMS上,然后再转移到PET上,也是个力气活。要转移的很均匀,还真要一点技术。我当时的水平还挺差,实验室另外一个博士生,可以一次转移2英寸大小的碳管薄膜。本来文章写好后,是投JACS的,不过很遗憾未中,最后在APL上发表。]

Flexible, transparent supercapacitors -- bend and twist them like a poker card

March 31st, 2009 Flexible, transparent supercapacitors are latest devices from USC nanotube lab

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Anatomy of a supercapacitor: two films combining Indium Oxide (In2O3) separated by a layer of Nafion film. Credit: USC Viterbi School of Engineering

It is a completely transparent and flexible energy conversion and storage device that you can bend and twist like a poker card.

 

It continues a line of prototype devices created at the USC Viterbi School of Engineering that can perform the electronic operations now usually handled by silicon chips using carbon nanotubes and metal nanowires set in indium oxide films, and can potentially do so at prices competitive with those of existing technologies.

The device is a supercapacitor, a circuit component that can temporarily store large amounts of electrical energy for release when needed. A team headed by Chongwu Zhou describes it a newly-published paper on "Flexible and Transparent Supercapacitor based on Indium Nanowire / Heterogeneous Films" in the journal (Vol.94, Issue 4, Page 043113, 2009).

Its creators believe the device points the way to further applications, such as flexible power supply components in "e-paper" displays and conformable products.

The device stores an energy density of 1.29 Watt-hour/kilogram with a specific capacitance of 64 Farad/gram. By contrast, conventional capacitors usually have an energy density of less than 0.1 Wh/kg and a storage capacitance of several tenth millifarads.

Zhou, who holds the Jack Munushiun Early Career Chair at the USC Ming Hsieh Department of Electrical Engineering, worked with USC graduate students Po-Chiang Chen and Sawalok Sukcharoenchoke, and post-doc Guozhen Shen.

The group incorporated nanowires with carbon nanotubes (CNTs) to form heterogeneous films and further optimized the film thickness attaching on transparent plastic substrates to maintain the mechanical flexibility and optical transparency of the supercapacitors.

According to Zhou, the work, based on combing CNTs with metal nanowiers represents an advance on earlier attempts to produce supercapacitors using just CNTs or graphite.

Such efforts resulted in only modest performance compared to those using transition metal oxide materials, including such oxides of iron, manganese and rubidium. Moreover, energy storage devices made by these materials have neither mechanical flexibility nor optical transparency, which have confined their applications in the flexible and transparent electronics. 

The critical improvement in performance, according to the research, can be attributed to the incorporation of metal oxide nanowires with CNT films. Indium oxide nanowire, with the properties of wide band gap, high aspect ratio, and short diffusion path length, can be one of the best candidates for transparent electrochemical capacitors. Professor Zhou's lab has pioneered this material over the past several years.

These new devices, by contrast, "demonstrated enhanced specific capacitance, power density, energy density, and long operation cycles, compared to those supercapacitors made only by CNTs," says the new release.

"We successfully produced a prototype of flexible and transparent supercapacitors built on two important nanostructured materials (including metal oxide nanowires and CNTs).

The researchers not only created metal oxide nanowire / CNT heterogeneous films as active materials and current collecting electrodes for the supercapacitors, but also examined the stability of the transparent and flexible supercapacitors through a large cycle number of charge/discharge measurements.

The paper contains description of how the new devices are made.

"CNT films were fabricated by vacuum filtration method. An adhesive and flat poly (dimethysiloxane) (PDMS) stamp was adapted to peel the CNT film off of the filtration membrane and then released it onto a polyethylene terephtalate (PET) substrate. In2O3 nanowires with a diameter of ~ 20 nm and a length of ~ 5 μm were synthesized by a pulsed laser deposition (PLD) method. The as-grown nanowires were sonicated into IPA solutions and then dispersed upon transferred CNT films to form In2O3 nanowire /CNT heterogeneous film for transparent and flexible supercapacitor study.

"In addition, with the increasing amount of In2O3 nanowires dispersed upon CNT films, the specific capacitance of the heterogeneous supercapacitor can be dramatically improved up from 25.4 Farad/gram to 64 Farad/gram. In comparisons to supercapacitors made by other transition metal oxide nanostructured materials, this observation indicates a good stability of In2O3 nanowire / CNT heterogeneous films for long-term capacitor applications."



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