Industrial Consultancy & Sponsored Research (IC&SR) , IIT Madras
Low-cost Zinc-polyiodide Redox Flow Battery
Technology Category/Market
Category- Energy, Energy Storage and Renewable Energy
Industry Classification:
Utility-Scale Energy Storage; Renewable Integration; Backup & UPS Systems and Industrial Energy Management
Applications:
Long-duration storage for load leveling and grid balancing; Storing renewable energy in microgrids and remote installations; Reliable, scalable backup power for telecom towers and critical infrastructure, On-site storage for manufacturing plants to reduce peak tariffs.
Market report:
The Global Redox flow battery market was valued at USD 0.34 billion in 2024 and is projected to grow to USD 1.47 Billion by 2035 with a CAGR of 16.2%
Problem Statement
- Zinc-polyiodide redox flow batteries (ZIFBs) offer high volumetric energy density and scalable, low-cost storage critical for grid-level renewable integration.
- Conventional ZIFBs use porous separators and Nafion membranes; high redox species solubility yields energy density but suffers from self-discharge and low cycle life.
- Further, key issues such as zinc dendrite growth, electrolyte crossover, low ionic conductivity, electrolyte imbalance, insoluble iodine precipitation, high membrane cost and reducing efficiency should be addresses.
- There is a need for a low-cost additive and a composite membrane to enhance energy efficiency, cycle life, and affordability by minimizing dendrite formation and preventing electrolyte shifting
Technology
- Utilizes 2 M KI, 1 M ZnBr₂, and 2 M KCl in aqueous solution; KCl enhances ionic conductivity and forms polyhalide redox couples (I₂Cl⁻ etc.), boosting cell voltage and stability during charge/discharge cycles.
- Bilayer of 10–300 µm microporous (polyethylene Daramic) and 20–300 µm cation-conducting Nafion; positioned with porous side toward anode, optimizing ion selectivity and minimizing crossover while reducing IR drop.
- Employs graphite felt or carbon cloth electrodes for both anolyte and catholyte; peristaltic pumping (20 mL min⁻¹) ensures uniform electrolyte flow and sustained reaction kinetics across electrode surfaces.
- Achieves ~100 mAh cm⁻² areal capacity at 50 mA cm⁻², volumetric capacity of 52 Ah L⁻¹, CE ~ 98 %, VE ~ 81 – 91 %, EE ~ 80 – 90 % with negligible capacity fade over >100 cycles.
- Electrolyte prep by dissolving salts; membrane activation via H₂O₂/H₂SO₄ treatments; cell assembly sandwiching membrane between electrodes; optional bilayer hot-press or solution casting for membrane fabrication.
Key Features/Value Proposition
- Achieves columbic efficiency up to ~99 %, voltage efficiency ~91 %, and energy efficiency ~90 % at 20 mA cm⁻², outperforming conventional ZIFBs..
- KCl additive promotes compact zinc deposition, reducing dendrite formation and preventing short-circuit risks inherent in bare porous separators.
- Bilayer microporous/Daramic + thin Nafion membrane blocks polyiodide crossover, minimizing self-discharge and maintaining capacity over extended cycles.
- Substituting thick Nafion® membranes with low-cost Daramic + 20 µm Nafion lowers membrane costs substantially without sacrificing performance.
- Delivers 100 mAh cm⁻² areal capacity and up to 52 Ah L⁻¹ volumetric capacity with 73 % utilization, surpassing prior ZIFB benchmarks.
Questions about this Technology?
Contact for Licensing
Research Lab
Prof. Kothandaraman R
Department of Chemistry
Intellectual Property
- IITM IDF Ref 2945
- IN 202441051658 Patent Application
Technology Readiness Level
TRL 4
Technology Validated in Lab