以氢氧化钴为电极材料的对称式超级电容器性能研究

发布时间：2018-05-04 12:15

本文选题：氢氧化钴 + 铁氰化钾　；参考：《吉林大学》2016年硕士论文

【摘要】：随着经济的发展,人们对于自然资源的需求量越来越大,对自然环境的破坏也越来越严重。这使得地球上原本丰富的自然资源日益匮乏,如雾霾、全球变暖等环境问题愈演愈烈。超级电容器作为绿色环保储能器件得到了越来越多的关注。超级电容器根据其正、负极材料可分为对称超级电容器与非对称超级电容器。相对于非对称超级电容器,对称超级电容器的制作简单,成本低。而相对于有机体系的超级电容器,水系超级电容器更加绿色环保、安全。但是水系电解液的工作窗口较低,约在1.2 V左右。因此,若要提高水系电容器的能量密度需要从提高电容器的比电容角度考虑。电容器的比电容源于电极和电解液两部分。可以通过电极材料和电解质各自的氧化还原反应存储和释放电荷,同时、独立、互不影响,叠加地贡献能量是提高该类化学电源装置性能的最有效手段。在众多电极材料的中,过渡金属化合物氢氧化钴(Co(OH)_2)的研究及应用较为广泛,尤其是α-Co(OH)2作为电极时其比电容较高,可逆性好。在电解中添加电活性物质可以提高电容器的比电容。电活性物质铁氰化钾(K_3[Fe(CN)_6]),亚铁氰化钾(K_4[Fe(CN)_6]),对苯二胺(PPD)作为无机离子和中性粒子的代表引起了许多科学家的兴趣。本文的目的是以α-Co(OH)_2为对称式电容器电极材料,在传统电解液氢氧化钾(KOH)中加入电活性物质并以离子交换膜将正负极室隔开,形成电极对称电解液不对称体系来提高氢氧化钴对称式超级电容的能量密度。这种方法仅见于本组的论文当中并且此前未见有关于α-Co(OH)_2作为对称式电容器正极及负极材料的报道。研究还发现,由于电极与电解液对超级电容器电容产生不同的贡献,提高电解液中氧化还原物质的浓度能大幅度提高超级电容器的比电容和能量密度。基于以上实验思路本文展开以下工作:首先,利用恒电位电化学沉积方法制得α-Co(OH)_2,经SEM测试α-Co(OH)_2呈纳米花瓣状垂直于碳纸(CFP)生长。选择质量约为0.96 mg的α-Co(OH)_2,在KOH电解液内测试,其比电容可达到742 F/g。为了使得电极与电解液同时贡献赝电容,在KOH电解液中添加铁氰化钾(K3[Fe(CN)_6]),以此作为电容器的正极体系,电位窗口为-0.1~0.45 V。经测试,当K_3[Fe(CN)_6]的浓度为0.05mol/L时,其比电容可达到2126 F/g。至于电容器的负极体系,我们在KOH电解液中添加对苯二胺(PPD),经过循环伏安测试后发现电极体系在较负的电位处出现一对氧化还原峰,使得电位窗口扩大到-1.0~0.45V。其次,使用制作的CFP/Co(OH)_2作为电极,用1mol/L KOH水溶液为电解液,组成Co(OH)_2|KOH|Co(OH)_2对称式超级电容器,经测试,其能量密度可达到4.44 Wh/kg,工作电压窗口可达到1.5V,而且具备较好的循环寿命(1000圈,87.6%)。其充放电的机制为两个电极上的氧还原反应,与之前报道过的以β-Co(OH)_2为电极材料,KOH为电解液的对称式电容器中正极氧化还原,负极双电层的充放电机制不同。然后,在正极室内添加10 m L的1mol/L KOH+0.05 mol/L K_3[Fe(CN)_6]水溶液,负极室内添加10 m L的1mol/L KOH+0.05 mol/L K_4[Fe(CN)_6]水溶液,并以离子交换膜将正、负极室隔开,组成Co(OH)_2|KOH+K_3[Fe(CN)_6]||K_4[Fe(CN)_6]+KOH|Co(OH)_2电容器。经测试,其能量密度可达到7.75 Wh/kg,若提高氧化还原物质的浓度,则比电容进一步增大。经过1000次循环后,其循环稳定性保持在89.2%。最后,为了进一步地提高电容器的能量密度,利用PPD和K_3[Fe(CN)_6]之间的电位差较大,采用1mol/L KOH+0.02 mol/L K_3[Fe(CN)_6]和1mol/L KOH+0.01 mol/LPPD作为电容器的正、负极电解液。经测试,电容器的能量密度可达到8.31 Wh/kg,当电活性物质K_3[Fe(CN)_6]和PPD的浓度提高到0.36 mol/L和0.18 mol/L时,电容器能量密度为49.5 Wh/kg,对应的功率密度为197 W/kg。但由于PPD与电极之间相互影响和PPD透过交换膜的问题,电容器的稳定性并不好(1000圈,40.4%)。
[Abstract]:With the development of the economy, the demand for natural resources is increasing, and the destruction of the natural environment is becoming more and more serious. This makes the original rich natural resources on the earth increasingly scarce, such as haze, global warming and other environmental problems. Supercapacitors have been paid more and more attention as green - green energy storage devices. Supercapacitors can be divided into symmetrical supercapacitors and asymmetric supercapacitors according to their positive, negative electrode materials. Compared with asymmetric supercapacitors, symmetric supercapacitors are easy to produce and have low cost. The water system supercapacitor is more green and safe than the organic supercapacitor, but the water system electrolyte works The window is about 1.2 V. Therefore, to improve the energy density of the water system capacitor, it is necessary to improve the capacitor's specific capacitance angle. The capacitor's specific capacitance is derived from two parts of the electrode and electrolyte. Adding the contribution energy is the most effective means to improve the performance of this kind of chemical power supply. In many electrode materials, the research and application of the transition metal cobalt hydroxide (Co (OH) _2) is more extensive, especially when the alpha -Co (OH) 2 is used as the electrode with higher specific capacitance and better invertibility. The addition of electroactive substances to electrolysis can improve the capacitor. Specific capacitance. The electroactive substance ferricyanide potassium (K_3[Fe (CN) _6]), potassium ferrocyanide (K_4[Fe (CN) _6]), and the representation of benzene two amine (PPD) as the inorganic ion and neutral particle have aroused many scientists' interest. The purpose of this paper is to use alpha -Co (OH) _2 as a symmetrical electric container electrode material to add electrical activity to the traditional electrolyte potassium hydroxide (KOH). The material is separated from the positive and negative electrode with the ion exchange membrane to form an asymmetric electrolyte electrolyte system to improve the energy density of the co symmetric supercapacitor of the hydrogen oxide. This method is only found in this paper and has not previously reported that alpha -Co (OH) _2 was used as the positive electrode and negative material of the symmetrical electric vessel. Since the electrode and the electrolyte have different contributions to the capacitance of the supercapacitor, the specific capacitance and the energy density of the supercapacitor can be greatly improved by increasing the concentration of the redox material in the electrolyte. Based on the above experimental ideas, the following work is carried out in this paper. Firstly, the constant potential electrochemical deposition method is used to produce the alpha -Co (OH) _2, and the SEM test is tested by the method of constant potential electrodeposition. The growth of alpha -Co (OH) _2 is perpendicular to carbon paper (CFP). The choice of alpha -Co (OH) _2 with a mass of about 0.96 mg is tested in the KOH electrolyte, and its specific capacitance can reach 742 F/g. in order to make the electrode and the electrolyte simultaneously contribute the pseudo capacitance and add potassium ferricyanate (K3[Fe) in the KOH electrolyte as the positive system of the capacitor, the potential window. When the -0.1~0.45 V. is tested, when the concentration of K_3[Fe (CN) _6] is 0.05mol/L, the specific capacitance can reach 2126 F/g. as to the negative electrode system of the capacitor. We add the benzene two amine (PPD) in the KOH electrolyte. After cyclic voltammetry, it is found that the electrode system has a pair of oxidation-reduction peaks at the negative potential, which makes the potential window expand to -1.0~0.45V. secondly, using the CFP/Co (OH) _2 as the electrode and the 1mol/L KOH water solution as the electrolyte, the Co (OH) _2|KOH|Co (OH) _2 symmetric supercapacitor is formed. The energy density of the Co (OH) _2|KOH|Co (OH) _2 symmetric supercapacitor can reach 4.44 Wh/kg, and the working voltage window can be reached, and has a good cycle life (1000 rings, 87.6%). The mechanism of its charge discharge is two. The oxygen reduction reaction on the electrode is different from the positive electrode redox of the symmetrical capacitor with the beta -Co (OH) _2 as the electrode material and the KOH as the electrolyte, and the negative electrode double layer is different. Then, the 1mol/L KOH+0.05 mol/L K_3[Fe (CN) aqueous solution of 10 m L is added in the cathode room, and the negative chamber is added to the negative chamber. The +0.05 mol/L K_4[Fe (CN) _6] water solution is separated by an ion exchange membrane and separates the negative electrode chamber to form a Co (OH) _2|KOH+K_3[Fe (CN) _6]||K_4[Fe (CN) _6]+KOH|Co (CN) _6]+KOH|Co capacitor. It is tested that the energy density can reach 7.75. If the concentration of the redox substance is increased, the capacitance is further increased. After 1000 cycles, its cycle is stable. At the end of 89.2%., in order to further improve the energy density of the capacitor, the potential difference between the PPD and K_3[Fe (CN) _6] is larger, and the 1mol/L KOH+0.02 mol/L K_3[Fe (CN) _6] and 1mol/L anode are used as the positive and negative electrolyte of the capacitor. The energy density of the capacitor can reach 8.31 When the concentration of K_3[Fe (CN) _6] and PPD increased to 0.36 mol/L and 0.18 mol/L, the energy density of the capacitor was 49.5 Wh/kg, and the corresponding power density was 197 W/kg., but the stability of the capacitor was not good (1000 circles, 40.4%) due to the interaction between PPD and the electrode and the exchange membrane of PPD through the exchange membrane.

【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM53

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