A neutral polysulfide/ferricyanide redox flow battery

Area of Science:

• Electrochemistry
• Energy Storage
• Materials Science

Background:

• Renewable energy integration necessitates efficient energy storage systems.
• Redox flow batteries (RFBs) show promise but face challenges in energy density, cost, and environmental impact.
• Solubility limits of active species restrict the energy density of conventional RFBs.

Purpose of the Study:

• To develop a novel RFB system overcoming the solubility limitations for enhanced energy density.
• To demonstrate a cost-effective and environmentally benign RFB for large-scale energy storage.
• To evaluate the long-term performance and stability of the new RFB system.

Main Methods:

• Designed a new RFB utilizing polysulfide and high-concentration ferricyanide (up to 1.6 M) reactants.
• Employed neutral aqueous electrolytes for improved environmental and cost profiles.
• Assembled and tested a cell stack to assess long-term cycling stability and capacity retention.

Main Results:

• Achieved high cell performance with 96.9% capacity retention over 1,500 cycles.
• Demonstrated a low reactant cost of $32.47/kWh.
• Exhibited a low capacity fade rate of 0.021% per cycle over 642 cycles (60 days) in a cell stack.

Conclusions:

• The neutral polysulfide/ferricyanide RFB offers a safe, long-duration, and low-cost solution for massive energy storage.
• This technology addresses key limitations of current RFBs, paving the way for practical applications.
• The system demonstrates feasibility for scale-up and integration with renewable energy sources.