High Power Interdigitated Carbon Nanotube Based Micro-Capacitors
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High Power Interdigitated Carbon Nanotube Based Micro-Capacitors Michael Spencer1, Kofi Adu2,3, Ramakrishnan Rajagopalan4,5 and Clive Randall1,2 1
Department of Materials Science and Engineering, Penn State, University Park, PA 16802, U.S.A.
2
Materials Research Institute, Penn State, University Park, PA 16802, U.S.A.
3
Department of Physics, Penn State – Altoona, Altoona, PA 16601, U.S.A.
4
Department of Engineering Science and Mechanics, Penn State, University Park, PA 16802, U.S.A.
5
Department of Engineering, Penn State DuBois, PA 15801, U.S.A.
ABSTRACT Micro-scale energy storage devices are of great importance to the advancement of low maintenance, high power electronics. They can easily be used in applications that extract energy from mechanical, solar, thermal and thermoelectric sources. Several of these devices have achieved mean areal capacitance of 1.5 mF cm-2 and maximal energy and power densities of 6.6 mJ cm-2 and 44.9 mW cm-2, respectively. It has been demonstrated that a smaller interspace enhances the performance. Currently, these types of devices are only made possible by using several micro-fabrication steps and techniques that are cost prohibitive and limit the larger scale manufacturability. We present a simple but highly scalable and cost effective method in fabricating high power interdigitated micro energy storage devices using binder-free carbon nanotubes membranes and laser irradiation to obtain interspaces on the order of 75 μm. The binder-free electrode devices show higher power density and an improved frequency response, compared to what has been reported in the literature. Additionally, we observed significant reduction in cell resistance leading to enhancement in cell capacitance, and consequently, an increase in energy density. INTRODUCTION Modern electronics are becoming increasingly ergonomic, and in order to continue this trend they require flexibility and autonomy. The primary challenge for these devices is incorporating a power source that is compatible with both the size and flexural requirements. In recent years, interdigitated micro-capacitors have set a new standard for performance at a small scale, outperforming other electrode configurations [1]. One downfall to this configuration is the intricate design, which requires several microfabrication steps that limit the device’s manufacturing scalability [2,3]. We demonstrate a simple but effective single-step laser scribing protocol on binder-free flexible carbon nanotube membranes, which are proven to have exceptional electrochemical performance [4]. This method will provide a scalable fabrication process and promote further development of these devices in the electronics revolution.
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One contribution to the success of energy storage devices is the accessible surface area, thus making the con
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