Slurry Electrodes for Redox Flow Batteries

J. Wainright, C. Wirth, R. Akolkar, R. Savinell
Case Western Reserve University,
United States

Keywords: energy storage, battery, slurry


Redox flow batteries are a promising option for utility scale energy storage. In redox flow batteries (RFB), the power and energy storage capacities are decoupled, making them highly scalable. Due to their high abundance, low cost, and low toxicity, iron and zinc are very attractive as reactive species for the negative half cells in large scale redox flow batteries. Unfortunately, the reduction of Fe(II) or Zn(II) used in the negative half-cell involves plating solid metal onto the electrode during charge. This plating reaction limits the battery’s capacity based on the spatial constraints of the flow cell, coupling the power and storage capacities of the flow battery and limiting its scalability. Slurry electrodes, consisting of a dispersion of conductive particles in the electrolyte, have been proposed as solution for this issue. By having the metal deposit onto the mobile dispersion of particles, instead of a stationary electrode, the power and storage capacities of a hybrid flow battery can be decoupled. In this manner, the slurry electrode concept is an enabling technology for the development of long duration (> 10 hours) electrical energy storage. By focusing on battery chemistries based on zinc and iron, our goal is to develop a battery capability that can increase the resilience of the electrical grid while also using domestically sourced materials. We will present results from our recent efforts to improve the capabilities of redox flow batteries based on slurry electrodes. These include fundamental studies of electrodeposition and of advanced additive chemistries to limit hydrogen evolution as a side reaction, the development of improved slurry particles that enhance the long-term stability of slurries under flowing conditions and the demonstration of improved cell and stack architectures designed to enhance the ease of manufacture.