聚丙烯腈基碳毡电极材料的结构调控、构筑及其电化学特性的研究

As a kind of electrode material for redox flow battery, polyacrylonitrile-based carbon felt is one of the key materials to improve the efficiency and reduce the cost. However, the micro structure of PAN carbon felt restrict each other between the high activity and low resistance. Three-dimensional braided structure inherent limits the further improvement of the mass flow. The structure of PAN carbon felt above is unable to significantly elevate performance. In current research project, we propose a novel composite structure, which PAN carbon felt can be improved by the synergistic effect of axis-radial carbon fiber microstructure and interface. In the proposed method, PAN pre-oxidized felt is used as raw material. Based on the investigation of the axial and radial microstructure of carbon fiber during the formation of carbon felt, the ‘skin-core’ structure of PAN carbon felt was optimized to reduce the ohmic polarization. As a consequence of electrostatic flocking of graphene on fiber surface, PAN carbon felt exhibits "flake"-shaped with high activity , in order to reduce the electrochemical polarization. Furthermore, high performance flow channel is synthesized to reduce the concentration polarization. In current research we focus on scientific problems in the synthesis process, such as the factor controlling mechanism, the electrochemical behavior and interface properties, in order to reveal the relationship between PAN carbon felt composites and electrochemical properties. It would be to lay the theoretical foundation to develope important materials for redox flow batteries.

作为液流电池的电极材料，聚丙烯腈基(PAN)碳毡是提高电池效率并有助于降低成本的关键材料之一。然而在PAN碳毡的微观结构上高活性和低电阻存在相互制约，固有的三维编织结构限制了对流动传质的改进，导致PAN碳毡无法大幅度提升性能。针对于此，本项目提出一种新颖的PAN碳毡复合结构，综合利用碳纤维轴径向微观结构协同界面效应提高PAN碳毡性能。以PAN预氧毡为原料，通过探究碳毡形成过程中纤维轴向和径向微观结构，优化PAN碳毡的“皮芯”结构以降低欧姆极化；通过静电植绒石墨烯，构建“鳞片”状的石墨烯/PAN碳毡高活性界面结构，从而降低电化学极化；借助合成高性能流道，降低PAN碳毡的浓差极化。通过研究上述过程中的结构控制、电化学机理以及界面性质等科学问题，揭示了PAN碳毡复合材料和电化学特性之间的作用机制，为液流电池关键材料的发展奠定理论基础。

铁铬液流电池在储能市场上具有显著的应用前景。在此大背景下，为进一步扩大铁铬液流电池的成本优势，提高其能量转换效率和功率密度，本项目以碳毡电极材料为研究对象，围绕碳毡碳化和活化过程中影响其极化行为的关键问题，对碳毡的前驱体材料、碳含量、含氧官能团以及表面催化剂方面开展了研究工作，构建其与电化学极化、浓差极化和欧姆极化之间的构效关系，实现了对铁铬液流电池用碳毡电极影响机理的深入且全面的研究及认知。为铁铬液流电池的发展提供理论基础和依据。具体成果如下：（1）对比了由不同前驱体材料制得的粘胶基碳毡和聚丙烯腈基碳毡的结构特性，测定了二者的电化学性能，并得到了上述材料在铁铬液流电池中的应用性能。明确提出表面传质是影响两种碳毡极化行为的主要控制步骤。（2）针对聚丙烯腈基碳毡碳含量与极化的构效关系问题，获得了碳含量为90~99.2%碳毡的结构演变规律，及其在铁铬电解液中的电化学性能。结果表明，上述碳含量范围内碳毡的电化学性能取决于电化学极化和欧姆极化。（3）根据含氧官能团对聚丙烯腈基碳毡结构和极化的影响，分别建立了边缘面氧官能团和平面氧官能团与碳毡极化之间的构效关系。研究表明，在氧官能团的作用下，碳毡电化学性能主要取决于电化学极化和浓差极化。（4）Bi对碳毡的活化机制主要取决于BiHx的形成反应，该反应受电荷转移和扩散的混合控制。引入ZrP后石墨毡含有适量的磷酸基团、较高的导电性和优越的亲液性而具有良好的电化学性能。硅酸刻蚀石墨毡电极电化学性能的提高是由于石墨毡有效比表面积、氧官能团和电导率的三重耦合作用。（5）发明了一种自流道式液流电池用石墨毡材料的制备方法。本发明的液流电池石墨毡电极能通过合适的体积密度配比有效降低液流电池的浓差极化。该制备方法更简便、快捷，应用范围较为广阔。