電沉積鈷錳氧化物/奈米碳管複合電極應用於非對稱超級電容

Fabrications of Cobalt Manganese Oxide/Carbon Nanotube Composite Electrodes through Electrodeposition and Their Applications in Asymmetric Supercapacitors

謝佳恩(Chia-En Hsieh)

指導教授 ： 戴念華

國立清華大學/工學院/材料科學工程學系/碩士(2020年)

摘要

近年來，全球暖化議題愈趨嚴峻，人們開始提升對高性能儲能裝置的需求。超級電容作為極具發展潛能的儲能裝置，具備快速充放電、高功率密度、循環壽命長以及低成本且安全等優勢。超級電容之效能表現取決於電極材料的選擇與結構設計，本研究選擇以混合金屬氧化物提升電容值與能量密度，並搭配奈米碳管的管狀結構來提升表面積與提供電子傳輸管道，使其在獲得金屬氧化物之高電容值同時，也改善金屬氧化物導電性較差的問題。
本研究利用化學氣相沉積法，在三維結構的不鏽鋼網上成長奈米碳管，接著以電沉積之製程方式搭配鍛燒熱處理來成長鈷錳氧化物於奈米碳管之上。透過調整電沉積製程時間以控制鈷錳氧化物之沉積量與形貌來得到片狀鈷錳氧化物包覆奈米碳管的鈷錳氧化物/奈米碳管/不鏽鋼網之複合電極結構。而在電化學表現上，此複合電極於掃描速率2 mV/s下，可得到最佳比電容值732 F/g。
最後，以鈷錳氧化物/奈米碳管/不鏽鋼網作為正極材料搭配活性碳/不鏽鋼網作為負極，在2 M氫氧化鉀作為電解液的條件下組裝非對稱超級電容。其中不鏽鋼網不僅作為電極基板，同時也具有集流器之功能，使組裝而成的非對稱超級電容在能量密度為47.39 W/kg下，可輸出400 Wh/kg的功率密度，且具有良好的循環穩定性，此外，在5000圈循環測試後，仍可保有76.8 %的電容值。

關鍵字

超級電容 ； 鈷錳氧化物 ； 奈米碳管 ； 電沉積

並列摘要

Recently, global warming has become more and more serious, and people have begun to increase the demand for high-performance energy storage devices. As an energy storage device with excellent development potential, supercapacitors have the advantages of rapid charge and discharge, high power density, long cycle life, low cost, and safety. The performance of the supercapacitor depends on the choice of electrode materials and the design of structure. In this study, the mixed transition metal oxide is used to improve the capacitance and energy density. The tubular structure of carbon nanotubes (CNTs) enhances the surface area and provides electron transmission channels.
In this work, CNTs were synthesized by the chemical vapor deposition method using three-dimensional stainless steel mesh (SSM) as a substrate, followed by the electrodeposition process with heat treatment to grow cobalt manganese oxide (CMO) on CNTs. By adjusting the electrodeposition time, we can control the amount and morphology of the CMO to obtain a composite electrode of CMO/CNT/SSM. In terms of electrochemical performance, this composite electrode can obtain the best specific capacitance value of 732 F/g at a scan rate of 2 mV/s.
Finally, we assembled an asymmetric supercapacitor using 2 M potassium hydroxide as the electrolyte. The CMO/CNT/SSM is used as the positive electrode, and the activated carbon/SSM is used as the negative electrode. The SSM also has the function of a current collector. The assembled asymmetric supercapacitor performs an energy density of 47.39 W/kg and a power density of 400 Wh/kg. After 5000 cycles of cycle testing, it can still maintain 76.8 % capacitance retention, suggesting that the composite electrode can be a promising candidate for energy storage devices.

並列關鍵字

supercapacitors ； cobalt manganese oxide ； carbon nanotubes ； electrodeposition

參考文獻

[1] C. Zhang, B. Zheng, C. Huang, Y. Li, J. Wang, S. Tang, M. Deng, Y. Du, Heterostructural Three-Dimensional Reduced Graphene Oxide/CoMn2O4 Nanosheets toward a Wide-Potential Window for High-Performance Supercapacitors, ACS Applied Energy Materials 2(7) (2019) 5219-5230.

[2] L. Ren, J. Chen, X. Wang, M. Zhi, J. Wu, X. Zhang, Facile synthesis of flower-like CoMn2O4 microspheres for electrochemical supercapacitors, RSC Advances 5(39) (2015) 30963-30969.

[3] R. Kötz, M. Carlen, Principles and applications of electrochemical capacitors, Electrochimica Acta 45(15-16) (2000) 2483-2498.

[4] A. González, E. Goikolea, J.A. Barrena, R. Mysyk, Review on supercapacitors: technologies and materials, Renewable and Sustainable Energy Reviews 58 (2016) 1189-1206.

[5] L.L. Zhang, X. Zhao, Carbon-based materials as supercapacitor electrodes, Chemical Society Reviews 38(9) (2009) 2520-2531.