SBIR-STTR Award

To achieve adoption of large scale stationary electrical energy storage systems at economically and environmentally sustainable levels, cost and volumetric energy density are driving the choice of battery chemistry. Room temperature sodium-sulfur batteries are an ideal candidate for these applications as this chemistry is capable of achieving theoretical gravimetric and volumetric energy densities 2.5- to 3-fold higher than lithium ion at a fraction of the cost. Despite the advantages to energy density and cost, room temperature sodium-sulfur batteries have not reached commercial readiness, as they suffer from several key challenges including sodium dendrite formation, anode stability, and polysulfide shuttling, resulting in degradation on the anode, low efficiency, safety concerns, and shortened cycle life. This program will design a membrane to specifically address safety and cycle life for room temperature sodium-sulfur batteries. The resulting membrane will block polysulfide migration while conducting sodium ions between electrodes, and suppress uneven plating and dendrite formation during cycling. This will significantly reduce safety concerns and increase cycle life. In Phase I, each component of the membrane will be optimized and the final membrane design will be confirmed in full cells. Cycling and safety improvements over current separators will demonstrated, and the membrane will be characterized to demonstrate excellent ion conduction, dendrite suppression and ability to prevent anode corrosion. Stationary storage for grid applications is a major application for this technology, but improvements in safety and cycle life will widen the range of applications that can benefit from this next generation battery system to include electric vehicles along with a wide range of backup power applications.

While lithium-ion (Li-ion) batteries have become ubiquitous in our day to day life, this technology is approaching its limit in terms of gravimetric and volumetric energy density. Stationary, grid-level storage of renewably energy sourced from wind and solar is driving development of next-generation battery chemistries. Stationary electrical energy storage (SEES) systems are becoming increasingly important as intermittent energy production from renewable energy sources is becoming more widespread. To achieve the adoption of large scale SEES systems at economically and environmentally sustainable levels, cost and volumetric energy density are driving the choice of battery chemistry. Giner, Inc. is developing a multi-functional membrane to advance commercial readiness and viability of room temperature sodium-sulfur (RT Na-S) battery technology. The membrane is designed to both address the technical challenges of RT Na-S technology as well provide an unmet need for a viable separator compatible with commercial scale battery fabrication. In Phase I, we developed and characterized a membrane and demonstrated performance in full Na-S small scale cells. We have demonstrated improved capacity and capacity retention, and developed a membrane which is compatible with large scale battery fabrication equipment. In Phase II, we will further develop this technology and focus on the scale up of the materials and fabrication process to demonstrate performance in prototype pouch cells. Pouch cells will be evaluated for energy density and cycle life under realistic grid-level conditions. Development of a RT Na-S battery technology for grid scale SEES applications is of enormous public benefit. Recent wide scale power outages due to an overburdened infrastructure highlight the need for technology to provide load leveling during peak power periods. As renewable energy from wind and solar becomes more widespread, SEES to store intermittent power generation for supplementing to grid power during low generation periods is key to widespread adoption of this technology. A low- cost, earth abundant solution with high volumetric energy density—such as the proposed RT Na-S battery technology—would bring the cost of energy storage to a fraction of what is currently possible and make renewable energy storage more accessible.