Industrial Consultancy & Sponsored Research (IC&SR) , IIT Madras
High-capacity Redox Flow Battery
Technology Category/Market
Category- Energy, Energy Storage & Renewable Energy
Industry Classification:
NIC(2008)- 2720- Manufacture of batteries and accumulators
NAICS(2022)- 33591 Battery Manufacturing
Applications:
Manufacturing of Batteries for grid energy storage; Peak Shaving and Load Leveling; Battery Storage for Evs; Uninterruptible Power Supply (UPS); Microgrid Energy Storage; Energy Storage for Remote Communities; Long Duration Energy Storage (LDES); Energy Storage for Telecommunications and Data Centers
Market report:
The global Redox Flow Battery Market size was valued at USD 243.06 million in 2023 and is projected to grow to USD 1.71 billion by 2036, with a CAGR of 16.2%
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Problem Statement
- The adoption of renewable energy sources like solar and wind is increasing, but their intermittent nature makes reliable electricity storage and delivery over long periods a significant challenge.
- Redox flow batteries (RFBs) using quinone-based aqueous electrolytes, particularly those with 2,6-dihydroxyanthraquinone (2,6-DHAQ) and potassium salt of iron hexacyanide (K4[Fe(CN)6]), suffer from low capacity and high decay rates, limiting their effectiveness for long-duration storage.
- Previous studies have shown that capacity loss in these RFBs is caused by degradation mechanisms such as dimer formation or hydrogen bonding, leading to irreversible changes in the anolyte and catholyte that reduce performance over time.
- There is a need for a redox flow battery with high capacity and a low decay rate, improving longevity and increasing the number of charge-discharge cycles, thus making it more suitable for reliable long-duration storage of renewable energy. This patent provides an easy route to achieve high capacity
Technology
- The invention involves increasing the charging cutoff voltage above conventional limits (more than 1.5 V, typically in the range of 2.0-2.4 V) to improve the performance of the anolyte in RFBs, specifically for 2,6-DHAQ.
- At higher voltages, the peroxo species (dimer 4) formed during the reduction of DHAQ is converted into the tetra-anion (3), which is electroactive and capable of storing more energy during charging.
- By adjusting the charging voltage, the capacity decay of the anolyte is minimized, and long-term cycling stability is achieved, with performance sustained even after 300 charge-discharge cycles.
- The higher charging cutoff voltage results in a significantly higher percentage of the theoretical capacity being utilized (e.g., 91% at 2.4 V), leading to better overall battery performance.
- The invention ensures that the anolyte remains stable throughout many charge/discharge cycles, with minimal degradation, and provides high capacity and low decay rate in the resulting RFB system, making it highly efficient for long-term use.
Key Features/Value Proposition
- When compared to literature data, the conditions were optimized in the invention to obtain higher capacity i.e., 12 Ah L-1 and lower the decay rate to 2.5% per day at 0.25 M concentration of anolyte.
- The system’s decay rate is only 2.5% per day, outperforming systems with decay rates up to 8% per day
- The invented cell was assembled with higher concentration of DHAQ2- (0.45 M) and demonstrated a discharge capacity of up to ~20 Ah L-1
- Aqueous alkali (KOH) ensures stable, safe, and non-toxic electrolytes, unlike other systems with more corrosive or hazardous materials.
- Robust testing with CV, NMR, IR, and EPR ensures stable performance and verifies no electrolyte crossover or anolyte degradation, making it more reliable than prior technologies under real-world cycling conditions.
- The system’s decay rate is only 2.5% per day, outperforming systems with decay rates up to 8% per day.
- By optimizing charging cutoff voltage, the system achieves up to 19 Ah L⁻¹, comparable to conventional VRFB systems.
Questions about this Technology?
Contact for Licensing
Research Lab
Prof. Kothandaraman Ramanujan
Department of Chemistry
Intellectual Property
- IITM IDF Ref 2476
- IN 553775 Patent Granted
Technology Readiness Level
TRL 4
Technology Validated in Lab