High-capacity polysulfide-polyiodide nonaqueous redox flow batteries with a ceramic membrane

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Nonaqueous redox flow batteries (NRFBs) offer advantages like wider potential windows but are limited by low capacity and high material costs.
• Developing cost-effective, high-capacity active materials is crucial for NRFB scalability in stationary energy storage.

Purpose of the Study:

• To design and demonstrate a high-capacity polysulfide (PS)-polyiodide (PI) NRFB system.
• To investigate the feasibility of using low-cost, high-solubility PS and PI in organic electrolytes for enhanced NRFB performance.
• To assess the stability and long-term cycling performance of the developed NRFB system.

Main Methods:

• A nonaqueous electrolyte comprising 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME) was used with high concentrations of polysulfide (PS) and polyiodide (PI).
• A Li-ion conducting ceramic membrane was employed to ensure high coulombic efficiency and capacity retention.
• Voltage control strategies were implemented for PS and PI to prevent irreversible solid formation, and in situ UV-vis spectroscopy was used to study reaction reversibility.

Main Results:

• The PS-PI NRFB achieved a highest volumetric capacity of 28 Ah L^-1 with 1.5 M PS and 4 M PI.
• The system demonstrated high coulombic efficiency (∼100%) and excellent capacity retention (>99%) over 100 cycles.
• Continuous flow mode testing showed stable cycling performance for over 300 hours, indicating good long-term applicability.

Conclusions:

• The developed high-capacity PS-PI nonaqueous system overcomes the limitations of traditional NRFBs by utilizing low-cost, highly soluble active materials.
• The demonstrated stability and performance suggest significant potential for NRFBs in large-scale stationary energy storage applications.
• This work provides a new pathway for advancing NRFB technology and expanding their use across various energy storage fields.