Tubular, proton-conducting, ceramic reversible fuel cell for high-performance energy storage

Reliable low-cost, grid-scale, and high-efficiency electrical energy storage is needed to accommodate the rapid growth in solar and wind-based intermittent renewable electricity generation. While batteries are well suited for short-term (hourly or daily) energy storage, they are less suited for longer-term (seasonal) electrical energy storage due to self-discharge challenges and economic constraints caused by a linear cost/stored-energy scaling relationship. Reversible fuel cells based on solid state ionic membranes can potentially address this electrical energy storage challenge. The team has demonstrated reversible protonic ceramic electrochemical cells which can operate with a charging/discharging current density of >1000 mA cm-2. This implies that reversible protonic ceramic electrochemical cells can function as ultrafast energy storage devices. However, the team recognized that the solid-state proton-conducting electrolyte membrane exhibits electronic conduction which leads to a Faradaic efficiency lower than 100%. In other words, less than 100% of the current applied to the cell in electrolysis mode operation results in the production of hydrogen, while the rest is lost through electronic shorting. A low Faradaic efficiency severely limits the energy conversion efficiency and must be addressed if reversible protonic ceramic electrochemical cells are to be technologically viable. Additionally, the conventional membrane is in a planar geometry which is not appropriate for robust and high-pressure operation because its high sealing area and relatively poor ability to handle thermal, chemical, and mechanical stresses. Thus, the architecture and geometry of electrolyte membrane and full devices should be engineered to overcome these problems and thus enabling to achieve robust and reliable energy storage. The Team will first conduct a fundamental, mechanistic study by leveraging numerous experimental and numerical tools to understand defect chemistry and probe the electronic leakage mechanisms in proton-conducing membrane materials and establish the strategies to mitigate the electronic leakage. To enhance the robustness and durability of the reversible fuel cells based on proton-conducting electrolyte membranes, the Team will demonstrate a novel tubular cell architecture by leveraging the tubular cell capabilities currently in production. Understand the electronic leakage of proton-conducting membrane and design novel membranes with minimized electronic leakage to improve energy efficiency. Fabricate the reversible protonic ceramic electrochemical reactors in a tubular geometry to enhance its robustness. Evaluate the performances of energy storage devices with novel membrane compositions and tubular geometry. Conceptually design the long-term energy storage system. This project can demonstrate proton-conducting electrolyte membranes and tubular reversible protonic ceramic electrochemical cell devices. The reversible protonic ceramic electrochemical cell system can function as a long-term energy storage technology to smoothen the wind/PV generation output fluctuations, aiming to improve the grid residence.