二硫化鉬/錳/鈷複合物之合成與應用於不對稱超級電容器之研製

Abstract

超級電容器(Supercapacitors)依其能量儲存機制可分為電雙層電容器(Electrical double-layers capacitors, EDLC)、擬電容器(Pseudocapacitor)與非對稱超級電容器(Asymmetric supercapacitor)三大類，與傳統的電容器相比之下擁有更優異的比功率、比電容值以及循環壽命，故在電動車與消費性電子產品的應用上受到關注。二硫化鉬(MoS2)是一個與石墨烯相似的二維材料，其層狀結構使MoS2具有與石墨烯相同的電雙層電容特性，而金屬離子的氧化還原能力使金屬摻雜具有擬電容的特性，故非常適合用於儲能元件的電極材料。目前儲能領域的研究已廣泛使用MoS2搭配金屬離子進行合成，但目前在儲能領域並沒有文獻同時使用Mn、Co進行MoS2的開發。因此，本研究將利用二硫化鉬與錳、鈷金屬離子，使用一步水熱法合成雙金屬的錳-鈷-二硫化鉬化合物(Mn-Co-MoS2)，製備具高活性位點與高比電容值之正極，並以活性碳製作負極，利用此高性能正、負極電極材料之搭配，進行非對稱超級電容器之開發，也同時合成文獻常見之Mn-MoS2、Co-MoS2一同進行比較。本研究所開發具有花狀結構且擁有高活性位點的Mn-Co-MoS2，其具有最低的電荷轉移電阻10.4 Ω以及比電容值高達268.7 F/g，與文獻常見的Mn-MoS2以及Co-MoS2相比之下，顯示Mn-Co-MoS2擁有更優異的電容性能。根據恆電流充放電量測結果顯示，在1 A/g的電流密度下Mn-MoS2的比電容值為214.7 F/g、Co-MoS2的比電容值為185.6 F/g、Mn-Co-MoS2的比電容值為268.7 F/g，此結果證實Mn-Co-MoS2的電化學性能優於Mn-MoS2及Co-MoS2。並且Mn-Co-MoS2電極在10 A/g的電流密度下經過5000次充放電循環後仍具有81.2%的電容維持率。本研究也將實驗結果與文獻進行比較，證實本研究所開發的Mn-Co-MoS2有機會成為超級電容器極具前景的電極材料。最後，為了驗證實際應用能力，使用Mn-Co-MoS2作為正極材料、活性碳作為負極材料，開發一款不對稱超級電容器，並點亮排列成ME圖樣的40顆並聯LED綠燈，證實本研究所開發之不對稱超級電容器具有作為儲能元件的實際應用能力。Supercapacitors can be divided into three categories: electrical double-layers capacitors (EDLC), pseudocapacitor, and asymmetric supercapacitor according to their energy storage mechanism. Compared with traditional capacitors, they have better specific power, specific capacitance, and cycle life. Hence, the application prospects in electric vehicles and consumer electronics have attracted attention. MoS2 is a two-dimensional material which is similar to graphene. Its layered structure makes MoS2 have the same double-layer capacitance characteristic as graphene, and the redox ability of metal ions makes MoS2 have the same pseudocapacitor characteristics as metal oxides. Consequently, it is quite suitable for being electrode materials of energy storage elements. The current research in the field of energy storage has widely used metal ions and MoS2 for synthesizing, but there is no literature in the field of energy storage using Mn and Co metal ions at the same time to development MoS2 composite.Therefore, this research is devoted to develop Mn-Co-MoS2, which uses a one-step hydrothermal method with Mn and Co metal ions. Prepare a positive electrode with high active sites and high specific capacitance, use active carbon to make a negative electrode, and use this combination of high-performance positive and negative electrode materials to develop an asymmetric supercapacitor. In addition, synthesize Mn-MoS2 and Co-MoS2 which are commonly reported in literature to show their differences. This research has developed Mn-Co-MoS2 with a flower-like structure and high active site, it has the lowest charge transfer resistance of 10.4 Ω and its specific capacitance is as high as 268.7 F/g. Compared with Mn-MoS2 and Co-MoS2 in the literature, it shows that Mn-Co-MoS2 has better capacitance performance. According to the constant current charge and discharge measurement results, the specific capacitance of Mn-MoS2, Co-MoS2, and Mn-Co-MoS2 are 214.7 F/g, 185.6 F/g, and 268.7 F/g at a current density of 1 A/g. This result confirms that the electrochemical performance of Mn-Co-MoS2 is better than Mn-MoS2 and Co-MoS2. Moreover, Mn-Co-MoS2 has a capacitance retention rate of 81.2% after 5,000 charge-discharge cycles at a current density of 10 A/g. This experiment result also compares with literature to confirm that Mn-Co-MoS2 developed in this research has the opportunity to become a promising electrode material of supercapacitors.Finally, in order to verify the practical application ability, Mn-Co-MoS2 is used as the positive electrode material and activate carbon as the negative electrode material to develop an asymmetric supercapacitor, and successfully light up forty parallel green LEDs with ME pattern. It is confirmed that the asymmetric supercapacitor developed in this research has the practical application ability as an energy storage element.