纤维素类生物质转化为新型纳米结构炭材料及离子液体体系超电容性能研究

For carbon-based supercapacitors, traditional activated carbons were widely used for commercial supercapacitors as a result of the advantages associated with their simple preparation process, low-cost and high surface area. However, graphene with open structure exhibited much better electrochemical performance than activated carbons. With the expanding of the range of commercial applications for supercapacitors, novel carbon materials combining the advantages of activated carbon and graphene attracted extensive attention. What would be ideal is to employ a relatively green carbonization method to create new carbon materials with graphene-like morphology, rather than activated carbon-like particulates, using biomass precursors. In this project, we proposed to utilize cellulose-based biomass as a feedstock to achieve the large-scale production of carbons with novel architectures by using hydrothermal method and carbonization-activation technique. The project aims to achieve the control of the thickness of carbon nanosheets and improve the electrochemical performance. The effects of hydrothermal environment, the structure of biomass, carbonization condition, and activation condition for the synthesis of carbon materials are mainly investigated, which can be beneficial for the clarification of the relationship between the composition and structure of precursor and the structure, composition, and morphology of carbon materials. In addition, this project also focuses on solving the problems of low capacitance and poor rate capability of traditional activated carbons in ionic liquids. By establishing the relationship between electrochemical property and porous structure of carbon materials, we can realize the aim of improving electrochemical performance of carbons in ionic liquids. By utilizing nature and nanotechnology to construct the design of new carbon architectures, low-cost supercapacitors with high energy density can be fabricated to extend the applications and accelerate the transition to “electrical economy”.

在超级电容器领域，由于传统活性炭的结构开放程度不足，使其倍率性能和电容值略逊于石墨烯类材料，但是具有制备工艺简单、成本低和高表面的优势。随着对高能量电容器需求的增加，开发兼具石墨烯和活性炭优异性能的新型结构炭材料日益重要。本项目拟采用以纤维素为主生物质为研究对象，结合水热反应和炭化-活化处理等手段实现低成本类石墨烯新型炭材料的可控制备，实现对炭纳米片层厚度的控制，并解决传统活性炭在离子液体体系高速率性能及电容表现欠佳的问题。重点考察介质环境、前驱体结构和反应条件对新型炭材料合成的影响，揭示生物质结构、组成与炭结构、形貌、成分之间的本质关系，并对合成机理进行推断与解释。建立炭材料结构与离子液体电化学性能的相互关系，并以此指导炭材料的结构调控。本项目从利用自然和纳米技术角度出发指导新型纳米结构炭材料的设计合成，为开发低成本、高能量、可用于极端环境的超级电容器的设计组装提供材料储备和理论支持。

在众多碳材料形态中，模板炭、碳化物衍生炭以及石墨烯在孔结构或者导电性方面有很大的优势，能够获得优异的倍率性能，但是面临着制备成本偏高/制备过程繁琐复杂的不足。商业化活性炭作为超级电容器的电极材料，其容量/倍率性能有待于进一步提高。从商业化应用的角度考虑，制备成本是首要关注的因素，低成本碳材料的制备才能得到大规模商业应用。因此，新型碳材料需要结合众多碳材料的优势，制备出兼具低成本、连续孔道以及类似石墨烯开放结构的碳材料。. 针对这一问题，本项目从生物资源的有效利用角度出发，充分发挥生物质本身的结构和成分特点，采用水热碳化以及高温碳化活化等手段制备具有纳米结构的新型碳材料。通过系统研究工艺条件实现了对碳材料微观结构、比表面积、孔结构、孔分布、元素组成等因素的调控规律，阐明了纳米结构碳材料的合成机理，完善了生物质转化为新型碳材料的标准化合成工艺，成功得到了分级孔碳纳米片、类石墨烯碳、掺杂碳等多种新型碳材料。在材料制备的基础上，深入探讨了电化学性能与材料结构、成分之间的构效关系，揭示了不同电解液体系(尤其是离子液体体系)下电荷存储的一般规律，解决了碳电极倍率性能差的问题。经过性能优化，离子液体基超级电容器的能量密度可达50 Wh kg-1以上，循环1万圈电容保持率在90%以上；水体系电容值可达450 F g-1以上，循环1万圈电容保持率同样在90%以上。. 本项目的实施为高能量、高功率、高稳定性、长寿命超级电容器的设计和制造提供了重要的材料和理论支撑。与此同时，本项目还展现了制备得到的生物质基碳可以作为有效载体实现活性材料的负载，通过协同作用提高了碳基复合材料的电化学性能。本项目共发表SCI收录论文19篇，申请中国发明专利4项。