SBIR Phase II: Engineered Nanoporous Ceramic Membranes that Enable High-Performance and Low-Cost Flow Batteries

This SBIR Phase II project seeks to develop a novel low-cost molecular filter for use in harsh environments. This is accomplished using commodity silica gel, commonly found as a desiccant in food packing, whose pores can be made to be only a few molecules wide. Accurate tuning of the size and shape of the silica gel pores enables certain molecules to pass through while others are blocked from passing. One promising application for these molecular filters is their use in grid-scale energy storage. Flow batteries could store city-sized quantities of renewable energy. However, they require the use of expensive molecular filters that are not easily replaced due to the harsh battery environments. The low-cost filters developed during this SBIR Phase II project have the potential to reduce the cost of flow batteries by as much as 15%, making them less expensive than grid-scale lithium ion batteries. Lower cost grid-scale storage means that more renewable energy generation (e.g., solar & wind) can be added without overwhelming the grid. Low cost molecular filter also has commercial upside with the potential to capture a significant fraction of the $2.7 billion-dollar market. Because of this, this project could generate nearly 15 jobs and $39 million dollars in tax revenue over the next 5 years. This SBIR Phase II Project is developing a molecularly selective sol-gel ceramic membrane that does not require calcination or high polymer loading but also does not fracture during compression in stack applications (e.g., fuel cells and flow batteries). This is accomplished by decoupling the selective region from the region of the membrane being compressed by the stack. These membranes will be utilized to improve the performance and reduce the costs of all-vanadium redox flow batteries (VRFB). VRFB membranes require selective transport of hydronium ions but not vanadium ions. Size and charge exclusion membranes must therefore have tight control over the pore size, shape and network structure to selectively transport ions. Towards this end, sol-gel processing and surface charge modification will be utilized to maximize proton conductivity and limit vanadium ion permeability. Optimized membrane formulations must also have excellent chemical and mechanical stability; showing no degradation after hundreds of VRFB cycles. Finally, membranes must be scaled from lab size (50 cm2) to commercial size (> 500cm2) while maintaining performance uniformity. The low-cost membranes developed during this SBIR Phase I project have the potential to reduce the cost of VRFBs by as much as 15%. Lower cost grid-scale storage means that more renewable energy generation (e.g., solar & wind) can be added without overwhelming the grid. 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.