Among the various redox flow batteries, the all-vanadium flow battery system (VRFB), which capitalizes on four different oxidation states of vanadium ions, has been the focus of increasing research efforts around the world due to their excellent electrochemical reversibility, long cycle life, and high reliability. The most commonly used electrodes in VRFB are graphite felts (GF) and carbon felts (CF) because of their high electrical conductivity, excellent stability, high corrosion resistance, and broad operational potential at a reasonable cost. Despite the intensive research efforts devoted to the modification of GF, achieving high power density and energy efficiency is still a significant challenge for the VRFB.
The use of graphene and carbon nanotube-based catalysts are not practical, considering their high cost, the requirement of sacrificial metal, and rigorous reaction conditions. Therefore, there is a need for a low cost, facile, and scalable approach to improving the performance of electrodes in all‑vanadium flow battery systems.
Technology Overview
Northeastern researchers are developing a scalable, effective surface modification method of graphite felt electrodes based on controlled electrochemical exfoliation, in order to enhance the mass and charge transfer of the electrode. 
This technology proposes a scalable approach to fabricate a unique hierarchical core-shell framework of graphite fibers by treating the GF using a controlled electrochemical exfoliation. At the first step of the exfoliation process, active nucleophile hydroxyl ions (OH-) are generated from the electrolysis of water and initially attack the graphite fibers at the edge sites and grain boundaries leading to depolarization and expansion of the graphite layers. The expanded graphite layers facilitate the intercalation of water (H2O) molecules and sulfate anions (SO4 2-) in between the layers, where the SO4 2- reduces to sulfur dioxide (SO2) and the H2O molecule oxidizes to oxygen (O2) causing gas evolution. These produced gasses exert forces towards the much weaker van der Waals bonding between the layers, triggering the exfoliation of the graphite fibers. In addition, the unique hierarchical core-shell architecture contains abundant surface oxygen groups that simultaneously behave as the active sites for the redox reactions and promote electron and ion transportation. These are critical requirements for redox flow battery electrodes.
- Enhances the wettability of the electrode leading to better electrolyte penetration and ion diffusion 
- Provides an adequate number of reaction sites 
- Accelerates the electron and ion transportation by increasing the local charge concentration 
- Excellent electrochemical activity resulting in high voltage efficiency with an excellent round trip energy efficiency 
- The entire process is rapid, requiring only one minute
- Environmentally friendly, energy-efficient, low cost, and can potentially be scaled up to roll to roll large-scale manufacturing
- grid energy storage
- solar desalinzation
- electric vehicles
- License
- Partnering
- Research collaboration
Patent Information:
For Information, Contact:
Mark Saulich
Associate Director of Commercialization
Northeastern University
Hongli (Julie) Zhu