面向电容性储能应用的石油基掺杂活性炭批量制备研究

Heteroatom-doped active carbons (HACs) are capable of delivering superior performance in capacitor electrodes and adsorption processes as compared to the undoped active carbons (ACs), because they possess not only high surface areas but also plenty of heteroatom-containing functional groups that help to efficiently enhance the application performances. However, there still exist several unresolved problems on the preparation of HACs. The heteroatoms are easy to etch during the activation process, and the mass production of HACs at a low cost is till difficult to realize. To resolve these problems, clearly understanding the transformation and reaction mechanism of heteroatoms during the carbonization and activation processes, and designing a process using cheap and available raw materials are very crucial, but still have not been systematically carried out. In this project, we plan to synthesize HACs by a synchronous carbonization and doping process followed by further activation, using pitch or petroleum coke as raw materials. The project will be focused on investigating the reaction mechanism of the heteroatom-containing groups during carbonization and activation processes, to find the key factors to control both the specific surface area and the doping level of HACs. The synthesis parameters will be optimized according to the request for capacitor applications. Finally, a large-scale production process will be designed and optimized to realize the 1 Kg-level mass production of petroleum-based HACs. Developing the mass production of high quality HACs will strongly improve the application technologies of ACs, which is of high scientific and economic values.

掺杂活性炭不仅拥有高表面积，还具备可有效提升应用性能的掺杂基团，因而在电容器电极和吸附等应用方面均表现出比普通活性炭更优异的性能。然而，在掺杂活性炭制备方面还存在活化过程中掺杂基团易流失、低成本批量制备困难等方面的问题。要解决这些难题，关键是要认清碳化和活化反应中掺杂元素的转化和反应规律，设计利用廉价易得原料制备掺杂活性炭的工艺，该方面的研究目前尚未系统开展。本项目将分别采用沥青和石油焦作为原料，通过碳化过程中掺杂再活化的方法制备掺杂活性炭。重点考察掺杂元素在碳化和活化过程中的反应机理，找出在制备过程中调控掺杂活性炭比表面积和掺杂元素含量的关键因素；根据电容器应用的要求，对掺杂活性炭的制备条件进行优化；最后，设计并优化批量制备工艺流程，实现石油基掺杂活性炭的公斤级批量制备。高品质掺杂活性炭批量制备工艺的开发将有力促进活性炭应用技术发展，具有重要学术和经济价值。

为了解决高品质掺杂活性炭低成本制备的难题，本项目在分级多孔活性炭制备的研究中，开发了压片-活化法来制备沥青基分级多孔活性炭（PACs），该制备过程是一个耗散体系。高密度的介孔和大孔的形成可归因于沥青粉-KOH胚体内部的加压气体分解产物的快速释放。通过调节耗散过程参数（如压片压力和胚体厚度），可实现多孔活性炭介孔和大孔结构的定向调控。由于具有超高的比表面积（高达3211 m2 g-1）、发达的多级孔结构和较低的杂原子（即氧原子）含量，最佳的多孔活性炭样品（PAC-10）在水系电解液和LIC有机电解液体系中均表现出优异的电容储能性能。特别地，当用作LIC正极材料时，在0.5 A g-1的电流密度下，PAC-10具有超高的比容量251 mA h g-1；而在15 A g-1的高电流密度下，其比容量仍高达158 mA h g-1。此外，此项工作也为实现高性能的电容性电极材料的批量制备提供了一种有效的方法。在掺杂碳材料选择性活化研究方面，硫氮双掺的碳材料分别采用酸性（CO2）和碱性（KOH和NH3）活化剂进行活化，该过程可看作典型的酸碱反应过程。当采用碱性活化剂进行活化时，掺杂碳材料中含硫基团相对于含氮基团表现出更高的反应活性，而当采用酸性活化剂时趋势则相反。采用NH3和CO2进行活化的碳材料单位面积电容高于采用KOH为活化剂的碳材料。在掺杂多孔碳的制备及应用方面，以三维多孔石墨烯为正极和掺杂多孔碳为负极组装了高性能锂离子电容器。得益于正负极材料在比容量、倍率性能和循环稳定性方面的匹配所带来的动力学平衡，多孔石墨烯和B,N共掺杂多孔碳组装的锂离子电容器在1 A∙g-1下有142 F∙g-1的比容量，在1018 W∙kg-1的功率密度下能量密度高达315 Wh∙kg-1。