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 Washington University team will develop new membrane separators for redox flow batteries using a styrene-ethylene-butylene block copolymer. The team will investigate three types of membrane construction to achieve the high levels of ion selectivity and mechanical stability necessary for use in flow batteries. If needed, the team will also explore the addition of inorganic silica particles in the polymer membrane to enhance selectivity. While many flow batteries utilize proton exchange membrane (PEM) separators that conduct positively-charged ions, the proposed membrane in this project is an anion exchange membrane (AEM) that will conduct negatively-charged ions. An inexpensive, durable AEM will allow for improved efficiency and lower system cost in existing flow battery systems such as the iron-chromium redox flow battery as well as enabling development of new low-cost chemistries.
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.