Searching for the Next Flow Battery Breakthrough

Flow batteries have long been regarded as one of the best technologies for large-scale energy storage. However, as the grid energy storage industry has grown rapidly, flow battery technology has struggled to compete against increasingly low cost lithium ion (Li-ion) batteries. Despite these struggles, new and large flow battery projects, including 200 MWh in South Australia and a combined 1,300 MWh in China, are evidence of the technology’s competitiveness. These new projects all use the industry leading vanadium redox flow battery technology.

The Disruptive Potential of Flow Batteries

While the vanadium technology is relatively well-proven and has attractive performance attributes, these systems may have a limited ability to reduce costs due to the high price of vanadium electrolyte. Researchers from universities, government laboratories, and startup companies are working to develop cheaper flow battery chemistries that utilize more abundant and cost-friendly materials. 

One of the best-known researchers in this field is Yet-Ming Chiang, a materials scientist and engineer at the Massachusetts Institute of Technology. Chiang’s team is working to develop a sulfur-based flow battery that could be built for as little as $20/kWh of energy storage capacity. The technology would be highly disruptive if commercialized at scale in this price range, as Li-ion battery packs for grid storage average around $210/kWh. However, Chiang’s team still struggles with a slow discharge rate and limited cycle life for the battery. 

Another promising alternative technology is being developed by Tianbiao Liu, a flow battery expert at Utah State University. This technology uses an iron electrolyte solution with ferrocyanide and ammonium at a neutral pH, making it less corrosive than other flow batteries. Liu’s team also claims the technology would be much cheaper than existing products. However, this battery suffers from low energy density, even compared to vanadium-based technologies. 

Innovation Close to Home

The latest potentially disruptive flow battery technology was announced this month from my alma mater, the University of Colorado, Boulder. Michael Marshak, an assistant professor in the University’s Department of Chemistry, leads a team that is using chromium and organic binding agents in a flow battery. The team’s battery shows dramatic improvements in voltage and efficiency. Marshak’s group developed a chelate (a special bonding to metal ions) known as PDTA, which shields the battery’s chromium electron, protecting the key chemical reactions. The team claims this battery design has an output of 2.13 V, nearly double the average for most flow batteries. The PDTA being used is a spinoff of EDTA, an agent already used in some hand soap, food preservatives, and municipal water treatments due to its bacteria-stymying properties.

A Long Road to Success

While the innovative technologies being developed in Massachusetts, Utah, and Colorado show great promise, there is a long road between success in a laboratory and large-scale commercialization. While the latest technology concepts aim for dramatic reductions in cost, other non-vanadium technologies are further in commercialization and promise lower cost and comparable performance. These include the zinc-bromide technology offered by Primus Power and the iron-based electrolyte system from ESS Inc.

Many promising technologies have failed to survive the journey from laboratory success and demonstration projects to full commercialization over the past several decades. Despite these challenges, new innovations such as these flow batteries are required for providing low-cost energy storage in a power grid based around renewable energy.