The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I project is derived from providing energy self-sufficiency to residential buildings. Fire-safe and low-cost redox flow batteries, combined with rooftop solar panels or backyard wind turbines, can meet the increased electricity needs of American families without relying on the national grid. During the daytime, solar arrays convert solar energy to chemical energy in batteries. During evenings, batteries will power houses and charge electric vehicles in family garages. Batteries play a critical role in harvesting and storing clean electricity for residential uses. Compared with lithium-ion batteries, the improved fire-safety profiles and reduced production costs of flow batteries will give homeowners peace of mind and allow the wider adoption of clean energy by society.This SBIR phase I project proposes to develop novel proton-conductive polymeric membranes that show reduced metal electrolyte crossovers and build the first 7 kW flow battery system that meets the energy need of a single-family house. To this end, the project will synthesize a group of phosphorylated polybenzimidazoles (PBIs) that have a phosphoric acid side chain. Such phosphoric acid groups can form unique zirconium phosphonate clusters that transport protons but deny the unwanted migration of metal cations. PBIs provide mechanical support to the zirconium-phosphate clusters. Zirconium and PBIs are bulk materials that cost significantly less than commercial perfluorosulfonic acids. The second task of this phase I project is to construct a 7 kW iron-titanium redox flow battery system. The peak electricity demand for the average American single-family house is around 7 kW. Such a battery will be connected to a rooftop solar system to meet residential electricity demands. The team plans to study various cell configuration designs. In particular, the project will focus on examining the effects of solvent channels of bipolar plates on the performance of the stack. In addition, other design parameters, such as pump flow rates and the choice of sealant materials, will be thoroughly investigated.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
