Hybrid Polyoxometalate Membranes
Energy storage is a critical enabler for large-scale integration of renewable energy onto the electric grid, as well as to improve grid efficiency, reliability, the distributed siting of resources that can help with transmission and distribution, and other applications. Flow batteries have the potential to provide the high energy, durability, and scalability required of grid-scale energy storage systems at an affordable price. A flow battery consists of two tanks of liquids that are pumped past a membrane held between two electrodes. Electrochemical reactions in the flow battery enable it to provide or store electricity, and ion transfer through a membrane is typically a key part of these reactions. However, current membranes do not have extremely high selectivity; over time they allow the undesired movement of liquid reactants from one side of the battery to the other. Advanced membranes and new liquid reactants could prevent this “crossover,” thus opening pathways to increase battery efficiency and enable operation on a daily basis for fifteen years with little degradation.
Project Innovation + Advantages:
The Colorado School of Mines will develop a new membrane for redox flow battery systems based on novel, low-cost materials. The membrane is a hybrid polymer that includes heteropoly acid molecules and a special purpose fluorocarbon-based synthetic rubber called a fluoroelastomer. The team will enhance the membrane's selectivity by refining the polymer structure, employing crosslinking techniques, and also through doping the polymer with cesium. The fluoroelastmer is commercially available, thereby contributing to a superior performance-to-cost ratio for the membrane. Flow battery experts at Lawrence Berkeley Laboratory will extensively test the selectivity, conductivity, and stability of the membranes developed in this project, and 3M will apply its decades of membrane fabrication experience to scale-up the new technology. If successfully developed, the separator in this project will increase efficiency and reduce cost in existing flow battery systems such as the all-iron redox flow battery.
If successful, developments made under the IONICS program will significantly reduce battery storage system costs for the grid to about $150/kWh (for a 5-hour discharge time, on a fully installed basis), a cost point that transforms the grid by enabling cost-effective electrical energy storage.
IONICS program innovations could contribute to energy storage solutions for the grid, improving grid resilience by providing widespread electrical storage, a basic capability the grid has largely done without since its creation over one hundred years ago.
Greater integration of renewable resources into the power mix, enabled by improved energy storage, will reduce the need for other more carbon-intensive forms of electricity generation. In addition, energy storage can improve the efficiency of the grid by allowing greater use of the most efficient, cost-effective generators.
IONICS program innovations could further establish U.S. businesses as technical leaders in energy storage, encouraging greater use of readily available renewable energy and helping to reduce costs on the grid.