基于廉价原料煤沥青/稻壳创制高性能中孔炭的机制及其储电性能研究

How to fabricate low-cost mesoporous carbon materials with tunable hierarchical pore structure and surface properties for high-performance supercapacitors and Li-ion batteries remains a challenge. In this project, we aim to develop a new procedure to make high performance mesoporous carbon materials with tuned three-demensional pore structure and surface properties from coal tar pitch and being coated rice husk by using ZnCl2 as activation agent coupling with microwave heating technique, of which the single ZnCl2 would function as the synergistic activating agent for the chemical activation of the two carbon precursors. This novel process is simple, and will lead to mesoporous carbon materials with tuned hierarchical pore structure and surface properties. The effects of the physical and chemical properties of raw materials, the mass ratio of raw materials, and the heating mode on the pore structure and the surface properties of the as-made hierarchical mesoporous carbons will be addressed in detail. The mechanism involved in the synergistic activation of coal tar pitch and rice husk will be studied. . The potential of these mesoporous carbons in supercapacitors will be explored in the electrolytes with higher decomposition voltage including ionic liquids, organic electrolyte and neutral electrolyte, and the energy storage mechanism involved will be studied. The storage and transport scheme of the charged ions in hierarchical pores of mesoporous carbons, and the effects of the pore structure parameters and the surface properties of mesoporous carbons on their specific capacitance, internal resistance and energy density will be investigated in order to figure out the relationship between the performance-structure-synthesis parameters of mesoporous carbons. This work will shed new lights on the energy storage mechanism of hierarchical mesoporous carbons for supercapacitors and Li-ion batteries. The results will give a new impetus on the research of coal chemical industry and realize the high added-value utilization of coal tar pitch, and will help improve the performance of supercapacitors and Li-ion batteries.

高性能超级电容器和锂离子电池用廉价中孔炭材料的结构与性能调变是一个富有挑战性的课题。本项目提出以浸渍在脱灰稻壳上的氯化锌等为单一活化剂，以煤沥青及其包覆的稻壳为碳源，利用微波高效加热和程序升温热处理实现对两种碳源的协同活化，制备具有三维孔隙结构的中孔炭。课题将研究揭示原料组成/配比、加热模式等对中孔炭的孔结构和表面性质的本征影响规律，阐明氯化锌协同活化煤沥青/稻壳制备中孔炭的机制，研究并建立具有层次孔中孔炭的廉价、快速、可控制备的新方法。在分解电压较高的离子液体、有机和中性电解液中，研究揭示荷电离子在中孔炭的层次孔中储存和输运规律及中孔炭结构和性质对其比容、内阻和能量密度等的影响规律，诠释中孔炭功能-结构-合成三者之间的关系，研究揭示中孔炭材料的储能机理。项目的实施将有助于丰富煤化工学科的科学内涵、实现煤沥青的高附加值利用，为进一步提升超级电容器和锂离子电池的性能奠定坚实的科学基础。

高性能超级电容器和锂离子电池用廉价中孔炭材料的结构与性能调变是一个富有挑战性的课题。本项目分别以稻壳和花生壳为碳源，以ZnCl2 为活化剂，制备了超级电容器用中孔炭材料，并研究其电化学性能。随后，以KOH代替ZnCl2，同时以稻壳和煤沥青为碳源，制备了微孔炭材料。接着，向原料中添加纳米氧化镁模板，同时以稻壳和煤沥青作为构建多孔石墨化炭纳米片的模块，以纳米氧化镁为导向模板，氢氧化钾为活化剂，制备了超级电容器用稻壳/煤沥青基多孔石墨化炭纳米片。随后，用三聚氰胺代替稻壳，即以煤沥青和三聚氰胺为碳源，KOH为活化剂，制备了微孔炭纳米片材料。此外，制备了锂氧电池用g-C3N4/LaNiO3复合材料，并研究其储电性能。主要结论如下：.采用常规加热ZnCl2活化稻壳，当 ZnCl2 与稻壳质量比为 2/1 时，在终温为850 ℃时，所得中孔炭的比表面积达 1768 m2/g；在 l mol/L Et4NBF4/PC有机电解液中，当电流密度为 50 mA/g时，中孔炭的比容和能量密度分别为 94 F/g和23.4Wh/kg。当煤沥青、稻壳和KOH质量分别为1 g、4 g和16 g时，制得的微孔炭的比表面积为1312 m2/g。当向煤沥青、稻壳和KOH原料中加入纳米氧化镁模板后，制得了多孔石墨化炭纳米片；所得材料作为超级电容器电极材料时，在0.05 A/g电流密度下，在6 M KOH 电解液中，其比容达397 F/g；当电流密度为20A/g时，其比容保持为222 F/g，显示了很高的容量和极好的速率性能。上述结果归因如下：稻壳经预炭化和脱灰后，除去了稻壳中的网络状分布的二氧化硅，形成的孔道有助于热塑性煤沥青将预炭化后的稻壳片段连接起来，降低了电极材料的内阻，提高了其导电性；采用纳米氧化镁作为导向模板和限域模板，辅以原位氢氧化钾化学活化有助于形成多孔石墨化炭纳米片，同时实现了材料的多孔化、石墨化和片状化的目的，所得材料内短的丰富的孔提高了超级电容器的容量和速率性能。最后，将所得多孔材料的平均孔径Dap、比表面积SBET、微孔表面积Smic、外表面积Sext和其比容C进行线性回归分析，得到了下述定量关系式：C=-24.99827Dap+0.15495SBET -0.13306Smic+227.23743。本项目原料廉价易得，制备工艺简单，易于工业化生产。