| 摘要: | 本研究主要是以陽極沉積法製備釩氧化物電極，實驗中發現依傳統文獻中的方法分別在硫酸氧釩鍍液及添加雙氧水之硫酸氧釩鍍液中所沉積之釩氧化物，不僅沉積時間過長且薄膜並非整片均勻狀。因此在本實驗中嘗試添加醋酸鹽類(醋酸鋰、醋酸鈉、醋酸鉀)進入鍍液中。結果發現所沉積出的釩氧化物與未添加的釩氧化物相比，釩氧化物能形成整片均勻的薄膜，且沉積時間相當快速。對於其結果，實驗進一步研究添加醋酸鹽類造成釩氧化物快速且均勻沉積的原因，分別針對pH值、陽離子以及醋酸根來做為探討，根據結果，得知添加醋酸根的硫酸氧釩鍍液在pH值約為3.8即可有效沉積釩氧化物。另一方面，額外添加的鋰、鈉、鉀也扮演著重要的角色，從FESEM圖得知，鋰、鈉、鉀的添加使得釩氧化物在外觀上有所不同，經由XRD更進一步證實，額外添加的陽離子會使的晶體結構扭曲、面間距及晶粒大小的改變，而XPS也同樣證實了釩氧化物的表面確實含有鋰、鈉、鉀。而電化學特性方面，則是利用循環伏安法(Cyclic Voltammetry)進行擬電容測試，結果發現陽離子的添加也會影響到釩氧化物的電化學行為以及比電容值大小的差異，其中，含鉀的釩氧化物之比電容值為350 F/g；含鈉的釩氧化物之比電容值為238 F/g；含鋰的釩氧化物之比電容值為220 F/g。 之後根據前面的結果，以最具有良好表現的含鉀的釩氧化物嘗試在各種不同的離子液體中進行循環伏安掃描之擬電容測試以及定電流充放電測試，其中離子液體包含N-butyl-N-methylpyrrolidine bis(trifluoromethylsulfony)imide (BMP-NTf2)、1-ethyl-3-methylimidazolium bis(trifluoromethylsulfony)imide (EMI-NTf2)、1-butyl-3-methylimidazolium hexafluorophosphate (BMI-PF6)、1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4)、1-ethyl-3-methylimidazolium thiocyanate (EMI-SCN) 、1-ethyl-3-methylimidazolium dicyanamide (EMI-DCA)、N-butyl-N-methylpyrrolidine dicyanamide (BMP-DCA)，經由結果顯示，釩氧化物的比電容值與離子液體中的陰離子有關，且在DCA系列的離子液體中具有較佳的比電容值，其中以BMP-DCA的比電容值為最高，約90 F/g左右，電位窗可達3.4 V，且壽命較優於其他離子液體與一般水溶液。最後藉由比能量對比功率圖得知，在低速掃描下，在水溶液中的比能量約有13 Wh/kg，而在BMP-DCA中則有132 Wh/kg。而在相同比能量下(約10 Wh/kg左右)，在水溶液中的比功率有9556 W/kg，而在BMP-DCA中則有27840 W/kg。顯示以離子液體為電解液確實能有效提升比能量及比功率，使得釩氧化物超高電容器更具有淺力。The vanadium oxides were prepared by anodic deposition in this study. Follow the method in the literature, the deposited vanadium oxides from VOSO4･xH2O solution with or without H2O2 were not uniform, and the time of deposition was too long. As a consequence, acetate (lithium acetate, sodium acetate, potassium acetate) were added into the VOSO4･xH2O solution to improve the vanadium oxide deposition. The vanadium oxides deposited from the solutions with acetate were uniform, and the depositing rates were faster. According to the results, three factors were discussed to clarify the reason for uniform and fast vanadium oxide deposition: pH values, cations, and CH3COO－. The experimental results showed that the plating solutions containing CH3COO－ at the pH around 3.8 produced vanadium oxide deposition fast and uniformly. On the other hand, the FESEM images confirmed that the cations affected the morphology of vanadium oxides. The XRD analyses explained that the cations could distort the lattice structure and change the d spacing and grain size. According to the XPS data, there were cations on the surface of vanadium oxides. In the electrochemical characterization, the cyclic voltammogtry showed that the cations could affect pseudocapacitive performance. The specific capacitance of Li-doped, Na-doped, K-doped vanadium oxide was 220, 238, 350 F/g, respectively. As the previous results, the K-doped vanadium oxide deposition had the best quality. The pseudocapacitive performances and discharge-charge tests of the K-doped vanadium oxide were measured in the ionic liquids. And the ionic liquids included BMP-NTf2, EMI-NTf2, BMI-PF6, EMI-BF4, EMI-SCN, EMI-DCA, and BMP-DCA. The results showed that the specific capacitance was related to the anion of ionic liquids. And the vanadium oxides in the DCA-based ionic liquids had the best capacitance performance. In particular, in BMP-DCA, the specific capacitance of vanadium oxide was 90 F/g, the potential window of vanadium oxide was 3.4 V, and the cycle life performance in BMP-DCA was better than in other ionic liquids and aqueous solutions. Then, the capacitive behavior of the vanadium oxide in BMP-DCA was compared with that in 3 M KCl. At low scan rate, the specific energy of vanadium oxide was 13 Wh/kg in 3 M KCl and 132 Wh/kg in BMP-DCA. At the same specific energy (~10 Wh/kg), the specific power of vanadium oxide was was 9556 W/kg in 3 M KCl and 27840 W/kg in BMP-DCA. The results indicated that the ionic liquid electrolytes could promote the specific energy and the specific power. With the ionic liquid electrolytes, vanadium oxides may become a potential supercapacitor. |
