Wan Charles Tai-Chieh, Jacquemond Rémy Richard, Chiang Yet-Ming, Nijmeijer Kitty, Brushett Fikile R, Forner-Cuenca Antoni
Joint Center for Energy Storage Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA.
Adv Mater. 2021 Apr;33(16):e2006716. doi: 10.1002/adma.202006716. Epub 2021 Mar 2.
Porous carbonaceous electrodes are performance-defining components in redox flow batteries (RFBs), where their properties impact the efficiency, cost, and durability of the system. The overarching challenge is to simultaneously fulfill multiple seemingly contradictory requirements-i.e., high surface area, low pressure drop, and facile mass transport-without sacrificing scalability or manufacturability. Here, non-solvent induced phase separation (NIPS) is proposed as a versatile method to synthesize tunable porous structures suitable for use as RFB electrodes. The variation of the relative concentration of scaffold-forming polyacrylonitrile to pore-forming poly(vinylpyrrolidone) is demonstrated to result in electrodes with distinct microstructure and porosity. Tomographic microscopy, porosimetry, and spectroscopy are used to characterize the 3D structure and surface chemistry. Flow cell studies with two common redox species (i.e., all-vanadium and Fe ) reveal that the novel electrodes can outperform traditional carbon fiber electrodes. It is posited that the bimodal porous structure, with interconnected large (>50 µm) macrovoids in the through-plane direction and smaller (<5 µm) pores throughout, provides a favorable balance between offsetting traits. Although nascent, the NIPS synthesis approach has the potential to serve as a technology platform for the development of porous electrodes specifically designed to enable electrochemical flow technologies.
多孔碳质电极是氧化还原液流电池（RFBs）中决定性能的组件，其性质会影响系统的效率、成本和耐久性。首要挑战是在不牺牲可扩展性或可制造性的前提下，同时满足多个看似相互矛盾的要求，即高表面积、低压降和便捷的传质。在此，提出非溶剂诱导相分离（NIPS）作为一种通用方法，用于合成适用于RFB电极的可调谐多孔结构。结果表明，支架形成聚合物聚丙烯腈与成孔聚合物聚乙烯吡咯烷酮相对浓度的变化会导致电极具有不同的微观结构和孔隙率。断层扫描显微镜、孔隙率测定法和光谱学用于表征三维结构和表面化学。对两种常见氧化还原物质（即全钒和铁）进行的流通池研究表明，新型电极的性能优于传统碳纤维电极。据推测，双峰多孔结构在平面方向上具有相互连接的大（>50 µm）大孔，且整体具有较小（<5 µm）的孔隙，在抵消特性之间提供了良好的平衡。尽管尚处于初期阶段，但NIPS合成方法有潜力成为一个技术平台，用于开发专门设计以实现电化学流动技术的多孔电极。
