基于表面功能化碳微球与氧化还原电解液的无粘结剂超级电容器及其协同效应研究

发布时间：2018-05-02 19:09

本文选题：多孔碳电极 + 氧化还原活性电解液　；参考：《武汉理工大学》2015年博士论文

【摘要】：设计制备能同时实现高功率密度、高能量密度的超级电容器是新能源领域的重要发展方向和研究热点。基于双电层储能的多孔碳材料,由于其表面积高,导电性好,因而被广泛应用于超级电容器中。研究表明,除了双电层储能,碳材料表面的活性官能团可以发生氧化还原反应而提供额外的容量;然而,碳材料表面活性官能团与电解液离子之间的反应通常不够稳定,导致其循环性能差,电荷存储受限。另一种增加碳材料氧化还原活性的方法是使用具有氧化还原活性的电解液,此类电解液在电池中发生额外的氧化还原反应因而可以存储额外的电荷。但是它们在循环反应过程中主要缺点是有限的氧化还原反应和循环稳定性差。本文针对以上问题,提出了通过在多孔碳微球表面引入功能化含氧基团,与具有高氧化还原活性的电解液协同作用,来大幅提高其能量密度与功率密度。此策略为新型储能器件的设计提供了一种有效的方法,且对于高性能超级电容器的发展有巨大的促进作用,并获得以下创新性成果:(1)我们提出了一种新的有效策略,在无需加入粘结剂的情况下,利用电解液中的Cu2+与多孔碳电极表面氧化还原反应,实现了超过传统电解液体系高达10倍的比容量(4700 F g-1)。三电极体系中在60 A g-1的大电流密度下充放电循环5000次后,容量保持率高达99.4%。在二电极体系中材料比容量仍可达1010 F g-1。大幅提升的电化学性能归因多孔碳电极超低的电荷转移阻抗(0.04?),以及电解液离子与表面氧分子之间的协同作用。(2)在使用CuCl2这一新型氧化还原电解液时,对称两电极超级电容器也展现出很好电化学性能。可在实现7 kW kg-1的功率密度的同时,获得高的能量密度(73 W h kg-1)与比容量(294 F g-1)。(3)混合型超级电容器在能源存储领域体现了优异的电化学性能。然而,基于微型多孔碳电极的对称式超级电容器要实现高的输出电压和高的比容量仍然是一个巨大的挑战。基于这一挑战,我们进一步设计了微型无粘结剂对称式超级电容器。通过设计相互交错的微型多孔碳电极,在电解液中加入对苯二酚和蓝胭脂红,显著提升了电化学性能。在中性的水系电解液中,电容器的工作电压达到了2.5 V。在氧化还原酸性电解液中,其面积比容量提升了3倍。这种氧化还原电解液导致性能的提升归因于对苯二酚的存在,其加速了电荷转移的过程。
[Abstract]:Designing and fabricating supercapacitors with high power density and high energy density is an important development direction and research hotspot in the field of new energy. Porous carbon materials based on double layer energy storage are widely used in supercapacitors because of their high surface area and good conductivity. It has been shown that, in addition to the double layer energy storage, the active functional groups on the surface of carbon materials can undergo redox reactions to provide additional capacity; however, the reaction between the active functional groups on the surface of carbon materials and electrolyte ions is usually not stable. It leads to poor cycle performance and limited charge storage. Another way to increase the redox activity of carbon materials is to use redox active electrolytes which can store extra charges by additional redox reactions in the battery. However, their main shortcomings in the process of cyclic reaction are limited redox reaction and poor cycle stability. Aiming at the above problems, it is proposed that the energy density and power density can be greatly increased by introducing functionalized oxygen-containing groups on the surface of porous carbon microspheres and cooperating with the electrolyte with high redox activity. This strategy provides an effective method for the design of new energy storage devices, and has a great role in promoting the development of high performance supercapacitors, and obtains the following innovative results: 1) We propose a new and effective strategy. Using Cu2 in electrolyte and surface redox reaction of porous carbon electrode without adding binder, a specific capacity of 4700F g ~ (-1) is achieved, which is 10 times higher than that of traditional electrolyte system. After 5000 cycles at high current density of 60 A g ~ (-1) in the three-electrode system, the capacity retention rate is 99.4%. In the two-electrode system, the specific capacity of the material can still reach 1010 F g -1. The greatly improved electrochemical performance is attributed to the extremely low charge transfer impedance of the porous carbon electrode, and the synergistic effect between electrolyte ions and surface oxygen molecules. 2) when using CuCl2, a new redox electrolyte, Symmetrical two-electrode supercapacitors also show good electrochemical performance. The hybrid supercapacitors with high energy density (73W / h 路kg ~ (-1) and specific capacity (294F / g ~ (-1) 路L ~ (3) have excellent electrochemical performance in the field of energy storage while realizing the power density of 7 kW kg-1. However, the realization of high output voltage and high specific capacity for symmetric supercapacitors based on micro porous carbon electrodes is still a great challenge. In view of this challenge, we have further designed miniature binder-free symmetric supercapacitors. By designing interlaced micro porous carbon electrode and adding hydroquinone and blue carmine into the electrolyte, the electrochemical performance was improved significantly. In neutral aqueous electrolyte, the working voltage of the capacitor is up to 2.5 V. In the redox acidic electrolyte, the area specific capacity was increased by three times. This redox electrolyte leads to the improvement of performance due to the presence of hydroquinone, which accelerates the process of charge transfer.
【学位授予单位】：武汉理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ127.11;TM53

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