低聚倍半硅氧烷为碳源制备有序分级孔碳及电容性能研究

发布时间：2018-11-06 11:10

【摘要】：碳基超级电容器具有充放电时间短、使用温度范围宽、循环寿命长、安全性能好等诸多优点,是最具应用前景的新型储能装置之一。但是,与二次电池相比,其能量密度较低。在保持碳基超级电容器高比功率的前提下,通过调控多孔碳电极材料的孔隙结构来提高其能量密度是该领域的研究重点。研究表明,孔径与净电解液离子尺寸相当的超微孔碳拥有大比容量储能特性,但介/大孔尺度的离子传输通道的缺乏影响其大倍率充放电性能。本文提出以具有分子内有机/无机杂化特点的多面体低聚倍半硅氧烷(POSS)作为碳源和产生均匀微孔的自模板,嵌段共聚物聚集体或者胶态晶体为产生有序介孔的软、硬模板,合成出有序微/介分级孔碳。具体内容如下:1.提出一种基于POSS与两亲性Pluronic型三嵌段共聚物PEO-PPO-PEO间自组装合成分级多孔碳的新方法。由于POSS分子中硅氧笼的分子尺度模板效应以及嵌段共聚物和所用的胺基功能化POSS化合物(笼型八胺苯基倍半硅氧烷,OAPS)间良好的组装适应性,所得碳既拥有十分均匀的微孔(尺寸~1 nm),也拥有高度有序的介孔(尺寸~4 nm),同时,还具有超过2000 m2 g-1的高比表面积和超过1.19 cm3 g-1的大孔容。通过简单地采用具有不同PEO/PPO比的嵌段共聚物,材料的介观对称性可以为二维六方(p6m)和体心立方(Im3 m)。另外,因为OAPS为富含氮元素的碳源前驱体,氮官能团也能自发掺杂到碳材料中。由于该类分级孔碳具有孔径接近电解液离子尺寸的均匀微孔,其在净离子液体电解液中最大比容量达~163 F g-1,在1.0 M H2SO4水系电解液中达~216F g-1。由于能够显著减小电荷传递阻力,该类分级孔碳与纯微孔碳相比表现出良好的倍率性能。当电流密度从0.25增至10 A g-1,最优试样在净离子液体和1.0 M H2SO4电解液中容量保持率分别可达94%和97%。2.由于商品化的Pluronic型三嵌段共聚物种类相对有限且分子量较低(通常Mw15000),由其胶束模板产生的有序介孔尺寸一般难以超过5 nm。为了研究介孔孔径对分级孔碳电容性能的影响,我们进一步以氧化硅胶态晶体为模板,笼型八胺苯基倍半硅氧烷(OAPS)为碳源,制备出含三维有序介孔、介孔孔径在14~40 nm范围内精确可调的有序微/介分级孔碳。结果表明,在净离子液体电解液中,随着介孔孔径增加,所得分级孔碳的倍率性能呈下降趋势。这可能是因为介孔孔径的增大也伴随着孔壁的明显变厚,反而增大了电解液向孔壁微孔内迁移、扩散的阻力。具有最小介孔孔径(~14 nm)的碳试样在电流密度为0.25 A g-1时比容量达172 F g-1,在电流密度增大至20 A g-1时仍有148F g-1,容量保持率为86%,表现出良好的倍率性能。
[Abstract]:Carbon based supercapacitors have many advantages, such as short charge / discharge time, wide temperature range, long cycle life, good safety performance and so on, so they are one of the most promising new energy storage devices. However, compared with the secondary battery, its energy density is lower. On the premise of maintaining the high specific power of carbon based supercapacitors, it is the focus of research in this field to improve the energy density of porous carbon electrode materials by adjusting the pore structure of porous carbon electrode materials. The results show that the ultraporous carbon with the same pore size as the net electrolyte has the characteristics of large specific capacity energy storage, but the lack of the mesoporous / macroporous ion transport channel affects its large rate charge-discharge performance. In this paper, the polyhedral oligomeric oligosilane (POSS), which has the characteristics of intramolecular organic / inorganic hybrid, is used as carbon source and self-template to produce homogeneous micropores, and block copolymer aggregates or colloidal crystals are used as soft and hard templates to produce ordered mesoporous structures. Ordered micro / mesoporous carbon was synthesized. The specific contents are as follows: 1. A new method for synthesis of graded porous carbon based on self-assembly of POSS and amphiphilic Pluronic triblock copolymer PEO-PPO-PEO is proposed. Due to the molecular scale template effect of siloxane cages in POSS molecules and the good assembly adaptability between block copolymers and amine-functionalized POSS compounds (caged octamine-phenyl bissiloxane, OAPS), The obtained carbon has both very homogeneous micropores (size ~ 1 nm),) and highly ordered mesoporous (size ~ 4 nm), as well as a high specific surface area of more than 2000 m ~ 2 g ~ (-1) and a large pore volume over 1.19 cm3 g ~ (-1). By simply using block copolymers with different PEO/PPO ratios, the mesoscopic symmetry of the materials can be two-dimensional hexagonal (p6m) and body-centered cubic (Im3 m). In addition, because OAPS is a carbon precursor rich in nitrogen, nitrogen functional groups can also be spontaneously doped into carbon materials. Because this kind of graded pore carbon has uniform micropores with pore size close to the ionic size of electrolyte, its maximum specific capacity in pure ionic liquid electrolyte reaches ~ 163F g-1, and in 1.0m H2SO4 aqueous electrolyte it reaches ~ 216F g-1. As the charge transfer resistance can be significantly reduced, this kind of graded porous carbon has a good rate performance compared with pure microporous carbon. When the current density is increased from 0.25 to 10 Ag-1, the optimal volume retention rate in the net ionic liquid and 1.0 M H2SO4 electrolyte can reach 94% and 97.2, respectively. Due to the relatively limited types of commercial Pluronic triblock copolymers and their low molecular weight (usually Mw15000), the ordered mesoporous size produced by their micelle templates is generally difficult to exceed 5 nm.. In order to study the effect of mesoporous pore size on the performance of graded pore carbon capacitors, we have further prepared three dimensional ordered mesoporous structure by using silica gel crystal as template and caged octamine-phenylbissiloxane (OAPS) as carbon source. Ordered micro / mesoporous carbon with a mesoporous pore diameter of 14 ~ 40 nm. The results show that with the increase of mesoporous pore size, the performance of graded pore carbon in pure ionic liquid electrolyte decreases. This may be because the increase of mesoporous pore diameter is accompanied by the obvious thickening of the pore wall, which increases the resistance of the electrolyte to migrate and diffuse into the pore wall. The specific capacity of carbon samples with minimum mesoporous aperture (~ 14 nm) was 172F g-1 at current density of 0.25 A g ~ (-1) and 148F g ~ (-1) when current density increased to 20 A g ~ (-1). Show good rate performance.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.4;TM53

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