奈米碳管陣列與錳氧化物奈米複合物超高電容器的製作與特性

Abstract

隨著科技進步，能源材料與科技的發展就更顯重要。錳氧化物為電化學電容器中極具潛力的電極 材料，具有價格低廉、無毒性、安全性高等優點，但是電極反應物與集電板間的附著性不佳，使其充 放電循環壽命衰減與單體超高電容器耐電壓有限，此兩大問題，造成應用上的限制；本三年之研究計 畫主題著重在利用高準直性奈米碳管陣列密度的調變、碳管表面改質、超電容系統電解液選擇、低維 度奈米電極反應物材料及其複合式電極的製備，探討其在超高電容器儲能性能及應用。 計畫中將引入高規則排列的陽極氧化鋁奈米孔洞作為模板，並利用電化學電鍍法沉積觸媒於陽極 氧化鋁孔洞內，利用化學氣相沉積法，以氫氣與甲烷為製程氣體合成奈米碳管陣列，藉此希望得到較 佳疏密程度之高準直性碳管，接著利用電漿反應系統及化學反應法來處理奈米碳管表面，以增加其管 壁上之氧官能基(C=O與-COOH)，使碳管表面在接枝時容易與錳氧化物進行反應性鍵結。將藉由水熱 法與水溶液反應法的方式合成出不同的低維度之氧化錳奈米結構，再利用電泳法及水溶液反應法來製 備 錳氧化物薄膜或奈米粒/Aligned MWCNTs/Ni 複合式電極，此電極將進行熱處理程序，來提升其電 容特性。最後，為了改善超高電容器耐電壓的問題，本研究將針對水系與非水系電解液進行測試，以 期盼得到最佳化參數。根據上述五大方向的改善，期待能藉由奈米碳管具高比表面積特性並配合改善 奈米錳氧化物在碳管上之附著機制，以獲得較大反應面積及可靠的複合奈米結構，開發出具有高功率 密度 (> 2,000 W/kg)、高循環次數 (> 20,000 cycles)及低充電時間 (10~12 分鐘)之高效能超高電容器。

In recent years, manganese oxide has been widely investigated as a promising supercapacitive material because of its low cost, high electrochemical activity and more friendly environmental nature than other transition metal oxides. However, poor adhesion between the electrode material and current collector, cause its charging and discharging cycle life to weaken, and the limited operating voltage of the monomer supercapacitor. The main subjects of this three-year proposal to be investigated include: the density control of aligned carbon nanotubes (ACNTs)、the surface modification of carbon nanotube、the choice of liquid electrolyte for supercapacitor system、the synthesis and characterizations of low-dimensional nanomaterials, the preparation of nanocomposite electrode, and properties and application of such nanocomposite supercapacitors. In this proposal, we will utilize nanoporous anodic aluminum oxide (AAO) with highly ordered pore channels as the template to grow carbon nanotube. After electro-deposition of the metal catalyst on the bottom of the AAO pore channel, multiwall CNTs will be synthesized by chemical-vapor-deposition (CVD) system using the gas mixture of CH4 and H2. Afterward, the aligned carbon nanotube (ACNTs) electrodes will be treated by the plasma reaction system and chemical oxidation reaction method separately to obtain the oxygen function base (C=O and -COOH) on the surface of ACNTs. Such treatments will facilitate the precipitation of the manganese oxide nanoparticles on the ACNTs electrodes. The low-dimensional manganese oxide nanomaterials with various crystal structures and morphologies will be synthesized using a hydrothermal method. Then, MnOx dispersed on the ACNTs by Electrophoretic deposition (EPD) and redox deposition process method will be employed to produce nanocomposite electrodes of MnOx/ACNTs/Ni. In addition, effects of heat treatment on material characteristics and electrochemical properties of the MnOx/ACNTs composite electrodes will be investigated. The performance of a supercapacitor is not only dependent on the electrode materials, but is also strongly affected by the electrolytes employed. Therefore, effect of electrolytes including aqueous based and non-aqueous based medium on the performance of supercapacitors will also be studied to obtain optimum parameters. After solving the above issues, the nanocomposite electrodes with high surface area and reliable nanostructure will be obtained through utilization of ACNTs and improved adhesion between MnOx and ACNTs. High efficiency supercapacitors with high power density (> 2,000 W/kg), high cycle-index (> 20,000 cycles) and low duration of charging will be expeted to be developed using such nanocomposite electrode and suitable electrolyte.