Untapped Potential: The Need and Opportunity for High-Voltage Aqueous Redox Flow Batteries

Total capital cost as a function of open circuit voltage for three durations (line styles) at a lower ($5/kg, yellow) and higher ($10/kg, blue) active species cost; the DOE target cost ($150/kWh) is shown as a horizontal teal line.

Scientific Achievement

Prior studies of the techno-economic design space for aqueous redox flow batteries (AqRFBs) have almost exclusively focused on cell potentials ≤1.5 V, due, at least in part, to the belief that battery operation at higher cell potentials in not feasible due to electrolyte decomposition. However, through careful consideration of electrolyte composition, cell design, and operating practices, AqRFBs with OCVs >1.5 V can operate with minimal and/or manageable side reactions.

Significance and Impact

The development of high-voltage AqRFB chemistries increases the attractiveness of the RFB technology platform and represents a promising pathway to low-cost energy storage. Higher voltages enhance both power and energy densities, reducing the system cost and providing a host of secondary benefits (e.g., reduced system footprint, increased flexibility for other cost and performance parameters, etc.).

Research Details

  • Solvent decomposition can be minimized via kinetic stabilization enabled by appropriate selections of electrolyte composition and electrode materials.

Beyond solvent decomposition, challenges remain for operation at extreme potentials for extended duration including electrode and active species stability which require fundamental analysis

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DOI: 10.1021/acsenergylett.1c02225

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