全钒液流电池用高性能微纳分级孔CNF电极的设计制备及性能研究

Electrode is one of the key materials of vanadium flow battery (VFB). Nowdays the thickness of the electrode is large and the resultant large internal resistance of VFB lead to the low working current density and the high cost of VFB. To resolve the contradiction among ohmic polarization, activation polarization and concentration polarization, the project proposed the idea of using carbon nanofiber web with micro-nano hierarchical pore structure as the electrode material of VFB. This kind of carbon nanofiber web was prepared by combining the co-electrospinning from multi-spinnerets with pore formed by activation techniques. In this design, the ultra-thin electrode thickness (tens - hundreds microns) will reduce the gap between the positive and negative current collector, hence reduce the internal resistance of VFB. The large surface area and plenty of oxygen-containing functional groups will provide the electrode the high electrocatalytic activity, and the micro-nano hierarchical pore structure will benefit to reduce the resistance during the mass transferring process. Therefore, it is a promising VFB electrode with high condutivity, high electrocatalysis activity and high mass transfer performance. In this project, further invesitigation will be focused on the relation between the perfomance and electrode structure, which will provide the basic theoretical guidance and experimental supporting for high performance VFB electrode.

电极是全钒液流电池（VFB）的关键核心部件之一，目前VFB用电极存在着电极较厚欧姆极化较大的问题，导致VFB工作电流密度较低而成本过高。本项目针对VFB电极中存在的欧姆极化与活化极化及浓差极化之间的矛盾问题，提出将多喷头静电纺丝制备碳纳米纤维（CNF）技术与活化造孔技术相结合，制备具有微纳分级孔结构的VFB用CNF电极材料的新构思。通过该设计，电极的超薄厚度(几十-几百微米)可大幅度降低电池欧姆极化；其较大的表面积和丰富的含氧官能团会赋予电极较高的电催化活性；而微纳分级孔有利于减小电解质溶液传质过程中的阻力，进而提高电极的导电性、电催化活性及传质性能。本项目将深入研究微纳分级孔CNF电极的构效关系和性能控制机制，为VFB用高性能电极的研发提供技术支持及理论依据。

大规模储能技术是实现可再生能源普及应用的关键技术。全钒液流电池（VFB）由于具有规模大、系统设计灵活、寿命长、安全性高等优点成为大规模高效储能的首选技术之一。然而，较高的电池成本阻碍了其商业化进程。电极是VFB的关键核心部件之一，目前VFB用电极存在着电极较厚欧姆极化较大的问题，导致VFB工作电流密度较低而成本过高。本项目针对VFB电极中存在的欧姆极化与活化极化及浓差极化之间的矛盾问题，通过将多喷头静电纺丝制备碳纳米纤维（CNF）技术与活化造孔技术相结合，制备出具有微纳分级孔结构的VFB用CNF电极材料。通过该设计，电极的超薄厚度(几十-几百微米)可大幅度降低电池欧姆极化；其较大的表面积和丰富的含氧官能团赋予电极较高的电催化活性；而微纳分级孔有利于减小电解质溶液传质过程中的阻力，进而提高电极的导电性、电催化活性及传质性能。本项目通过研究微纳分级孔CNF电极材料的形成机理及调控机制，明确了微纳分级孔CNF电极的孔结构、表面结构与其导电性能、电催化性能和传质性能之间的构效关系，确立了高性能VFB用微纳分级孔CNF电极的结构和制备方法。开发的高性能VFB用微纳分级孔CNF电极在工作电流密度为120mA/cm2时的库仑效率为96.0 %，电压效率为84.9 %，能量效率为81.6 %，140mA/cm2时500个循环效率无明显衰减。本项目研究结果发表SCI论文4篇，申请中国发明专利4项，授权1项，项目研究结果对于全钒液流电池高性能电极材料的开发具有重要的指导意义。