(Invited) Separator Requirements for Nonaqueous Flow Batteries

Energy storage is increasingly viewed as a potentially valuable asset for electricity grids composed of high fractions of intermittent sources, like wind turbines, or unreliable generation and transmission services.  Flow batteries are a candidate technology for large-scale, long duration storage of grid energy.  Both aqueous and nonaqueous technologies are being researched and technical progress is being made on both fronts.  The separator between the positive and negative electrolytes is a key technology that must be addressed in both cases.  Nonaqueous electrolytes are generally less conductive than aqueous electrolytes, and the degree to which this can be tolerated in light of higher expected operating voltages needs to be understood.  We use techno-economic modeling to establish ranges of separator properties that are required to attain economic viability for nonaqueous flow batteries and compare these to the properties required for aqueous cells.