碳化细菌纤维素/碳纳米管复合气凝胶柔性电极的研究

The existence of both high cost and complex preparation technology of electrode materials for flexible lithium-ion batteries is a critical bottle-necking issue restricting the development of flexible lithium-ion batteries. To solve this issue, the project combines low-cost carbonized bacterial cellulose with high conductive and superior flexible carbon nanotubes to design the substrates of secure and compressible electrodes, taking full advantage of carbonized bacterial cellulose with three-dimensional carbon nanofibers, surface hydroxyl groups and pressure sensitive. Inorganic Si with lithium-ion storing ability can molecular-scale accurately be anchored on such substrates. We will construct Si/carbonized bacterial cellulose/carbon nanotubes electrodes, develop a low-cost and scalable method for the fabrication of flexible electrodes based on carbonized bacterial cellulose/carbon nanotubes aerogels, illustrate the formation of the Si/carbonized bacterial cellulose/carbon nanotubes electrode interfaces and reveal the effects of structures of the components and compressive stress on pores, conductive network and flexibility of the electrodes. Both the deep relation between compressive stress and electrochemical performance of the electrodes and energy storage mechanism will be clarified. To optimize the preparation technology, we will develop secure and compressible electrodes with high energy density. The implementation of this project will obtain carbonized bacterial cellulose/carbon nanotubes based flexible electrodes, and more importantly it will help understanding the rules of construction for flexible electrode systems based on carbonized bacterial cellulose and lay out a theoretical foundation for the development of novel flexible electrodes.

制约柔性锂离子电池发展的瓶颈是目前柔性电极材料成本高和制备工艺复杂，针对这个问题，本项目提出以价格低廉的碳化细菌纤维素与碳纳米管复合，利用碳化细菌纤维素的三维（3D）连续碳纳米纤维导电网络、表面羟基官能团、压敏特性和碳纳米管的高导电性、高柔性来设计安全型柔性可压缩电极基体，并实现无机插锂材料Si分子尺度精确锚定在电极基体上。研究Si/碳化细菌纤维素/碳纳米管电极的构建，建立碳化细菌纤维素/碳纳米管复合气凝胶柔性电极的低成本、可规模化制备方法，阐明电极各组分的界面结合机理，研究各组分结构参数和压应力对电极的孔结构、导电网络、柔性的影响，从而揭示压应力与电化学性能的内在联系和电极储能机理，优化制备工艺，开发出高能量密度安全型柔性可压缩电极。通过本项目的实施，创建碳化细菌纤维素/碳纳米管复合物柔性电极平台，加深对碳化细菌纤维素电极体系构建规律的认识，为新型柔性电极的开发奠定理论基础。

取之不尽的纤维素绿色碳资源利用是发展趋势，在储能材料设计上，碳化纤维素碳材料优势非常明显，具有一维纳米碳纤维结构、少量含氧官能团、丰富的孔结构和易于制备膜和气凝胶等优点。然而，纤维素碳化规律未有深入研究，实现其可控制备与加工是非常有挑战，特别是多孔柔性碳基底膜的制备。本项目利用碳化细菌纤维素的特性设计高性能储能材料和可用于储能器件的柔性碳基底，并阐明电极材料理化性质与电化学性能的构效关系。本项目成功制备了具有高电化学活性和高稳定性硅碳纳米棒，应用于锂离子电池储能器件上。通过简单溶胶-凝胶法、热解碳化和镁热还原三步制备得到高分散性、高硅载量（98.7%）、大比表面、直径低于临界值250 nm的一维多孔棒状结构硅/热解细菌纤维素复合材料，低于临界破裂直径的多孔硅纳米棒可有效缓解硅的体积膨胀效应及电极粉化，提高循环寿命。本项目深入认识了纤维素高低温热解过程中的变化规律，发现纤维素热解收缩剧烈和导电率低的两大问题，并制备出不同的热解纤维素复合柔性碳基底，项目成员发明了一种碳化细菌纤维素/碳纳米管柔性电极基底材料，利用细菌纤维素水凝胶的吸水特点，在碳纳米管悬浮液中浸泡失水纤维素水凝胶，反复多次，此浸泡技术可使大量的碳纳米管进入到细菌纤维素三维孔道中，然后通过在惰性或还原气氛下碳化制备得到高电导性和力学性能的多孔碳化细菌纤维素复合膜；此外，针对细菌纤维素膜热解收缩剧烈和直接利用石墨烯和碳纳米管复合碳化纤维素易于团聚而难分散性的问题，首次提出通过在细菌纤维素膜中原位生长普鲁士蓝材料，然后高温热解，普鲁士蓝热解后变成树枝状碳管和石墨烯片，并实现树枝状碳管和石墨烯片均一分散在碳化细菌纤维素膜中。在此基础上，优化碳化纤维素基电极材料性能，为纤维素高值储能材料制备技术的建立奠定重要理论基础。