Wind and solar electricity are gaining traction in the marketplace, but the electricity available from these sources is out of synch with demand Protonic ceramic electrochemical cells (PCECs) operating at intermediate temperatures (400 - 650°C) have enormous potential for electricity storage and delivery by reversible operation between electrolysis and fuel cell modes and therefore stand to address the obstacles stalling further penetration of renewable electricity Recent advances made by the PI have resulted in cells that deliver record power densities for electricity production, record hydrogen generation rates for electrolysis, exceptional reversibility between these two modes, and prolonged stability over several hundreds of hours While these results have pushed the promise of PCECs towards commercial realization, two key challenges remain: (1) moderate Faradaic efficiency, presently 50 to 80% in electrolysis mode, which translate into system level efficiency losses; and (2) limited attention to fabrication approaches suitable for high-volume manufacturing Faradaic efficiency losses are the consequence of electronic conductivity through the electrolyte membrane, which should ideally conduct only protons and not electrons We propose an innovative two-pronged strategy for eliminating electronic leakage: (i) introduction of a thin, purely proton-conducting, electron blocking layer, and (ii) development, via a high throughput experimental effort, new perovskite electrolyte compositions that inherently display diminished electron conductivity without sacrificing other properties The approach provides risk mitigation and ensures that the critical challenge of Faradaic efficiency will be tackled To facilitate high-volume manufacturing at low cost, we propose to establish fabrication of high- performance cells by tape-casting, screen-printing, and co-sintering To meet these challenges we have assembled a world-class team PI Dr Sossina Haile, has years of experience in oxide materials development and currently holds the worlds record PCEC performance; Prime Contractor Fuel Cell Energy has deep expertise in fuel cell manufacturing and technology translation; Gaia Energy Research Institute has a wealth of sophisticated tools for technoeconomic analysis in the energy domain that will be deployed here Northwestern University will develop new membranes with diminished electronic conductivity without sacrifices in ionic conductivity or stability, and use measured component level properties to predict cell-level electrochemical characteristics, focusing on Faradaic efficiency Fuel Cell Energy will fabricate large-area cells with electrochemical characteristics comparable to high-performance button cells by methods amenable to large-volume manufacturing Gaia will perform technoeconomic analysis to determine materials costs at various scales of mass production The results of this project will be translated into a commercially attractive technologies that have the potential to (1) generate electricity efficiently in fuel cell mode (up to ~60% electrical efficiency), (2) generate hydrogen in electrolyzer mode (at as low as $2/kg H2), and (3) store energy efficiently operating in dual-reversible fuel cell-electrolyzer mode
