Direct Ink Writing of 3D‐Structured All‐Carbon Electrodes with High Electrical Conductivity for (Vanadium) Redox Flow Batteries

Redox flow batteries are attractive systems for large-scale energy storage due to their capability to uncouple energy and power but still need to make several improvements to reach full commercial scale. The need to search for better components, including electrode materials that allow the internal flow of electrolytes and have optimal electrochemical performance is a hot topic in the development of this kind of battery. The use of direct ink writing technology to engineer complex electrode materials both in the architecture and chemical composition opens a new field of research to optimize electrode performance. In this study, several formulations are prepared using graphite, multiwall carbon nanotubes, and two different Polyacrylonitrile (PAN)-based short carbon fibers. Furthermore, a graphitizable binder is added to the formulation to help consolidate the printed object into a highly conductive (3000-8000 Sm^-1) and mechanically resistant carbon electrode after a moderate heat treatment (800 °C). The 3D electrodes are successfully tested in an all vanadium redox flow cell showing a competitive performance when compared to benchmark electrodes (graphite felts).