SABERS: Solid-State Lithium-Sulfur Battery Technology Portfolio

In traditional batteries with liquid electrolytes, e.g., lithium-ion, each battery cell must be individually sealed, packaged, and electrically connected to other cells in the pack. The cells in solid-state batteries on the other hand may be stacked on top of one another with only a separation layer in between, called a bipolar plate. These bipolar plates or membranes if thin enough must be electrochemically inert to the electrode and electrolyte materials while providing electrical connectivity between the individual cells. Here, NASA has combined advances in the preparation of carbon nanomaterials and solid-state batteries to create extremely lightweight bipolar plates and membranes. These bipolar membranes will enable high energy density solid-state batteries unachievable with typical bipolar plate materials like stainless steel, aluminum, aluminum-copper, or conductive ceramics. The carbon bipolar membranes may be fabricated in multiple ways including but not limited to directly compressing carbon powders onto an electrode-electrolyte stack or separately making a film of the carbon material and dry pressing the film between other battery layers. The new bipolar membranes have been demonstrated in high energy density solid-state batteries in coin and pouch cells. The carbon bipolar membranes are at technology readiness level TRL-4 (Component and or breadboard validation in laboratory environment)and are available for patent licensing.

This invention is for scalable methods that allows preparation of bulk quantities of holey nanocarbons with holes ranging from a few to over 100 nm in diameter. The first method uses metal particles as a catalyst (silver, copper, e.g.) and offers a wider range of hole diameter. The second method is free of catalysts altogether and offers more rapid processing in a single step with minimal product work-up requirements and does not require solvents, catalysts, flammable gases, additional chemical agents, or electrolysis. The process requires only commercially available materials and standard laboratory equipment; and, it is scalable. Properties that can be controlled include: surface area, pore volume, mechanical properties, electrical conductivity, and thermal conductivity.

Aluminum-air batteries produce electricity from the reaction of atmospheric oxygen with aluminum. They have extremely high energy densities, but significant problems remain with byproduct removal due to use of traditional electrolytes. The electrolyte used is an aqueous potassium hydroxide (KOH) solution, incorporated into a polymer-based electrolyte matrix. Traditional alkaline electrolytes enable high ionic conductivity but corrode aluminum, wasting active material and releasing hydrogen gas. Unlike free liquid electrolytes, this hybrid design holds the conductive solution in place, providing the same high ionic conductivity while dramatically reducing the uncontrolled corrosion and gas evolution that typically deplete aluminum electrodes. The polymer host also prevents leakage and drying, improving reliability under demanding conditions such as high altitude and variable temperature environments. The aluminum-air battery electrolyte is a lightweight, high-capacity, and inherently safer primary power source that can meet stringent aerospace requirements for emergency and backup energy. Beyond aircraft, the technology’s combination of high energy density, safety, and sustainable byproducts makes it attractive for electric aircraft, defense systems, and other mission-critical applications. The electrolyte for aluminum-air batteries is available for patent licensing.

NASA Ames has developed very small-sized oxygen sensors made of a graphene and titanium dioxide (TiO2) hybrid material. With ultraviolet (UV) illumination, these sensors are capable of detecting oxygen (O2) gas at room temperature and at ambient pressure. The sensors are able to detect oxygen at concentrations ranging from about 0.2% to about 10% by volume under 365nm UV light, and at concentrations ranging from 0.4% to 20% by volume under short wave 254nm UV light. These sensors have fast response and recovery times and can also be used to detect ozone. This unique room temperature O2 sensor provides significant advantages in O2 sensing applications, especially those applications where high operating temperature requirements cannot be met, or would result in inefficient manufacturing processes. Since graphene is not intrinsically responsive to O2, and TiO2 is not responsive to oxygen at room temperature, the materials are first synthesized as a hybrid material. The synthesized graphene- TiO2 hybrid material is then ultrasonicated and then drop-casted onto a series of Interdigitated Electrodes (IDE) to form the sensors. Ultrasonication ensures effective charge transfer at the graphene- TiO2 interphase. The graphene and the titanium dioxide may be present in the composite material in different ratios to ensure optimal oxygen detection. It is the combination of graphene with TiO2 that yields a semiconducting material capable of O2 sensing at room-temperature operation.

The subject technology is an extension of closely related, solid-state ultracapacitor innovations by the same team of inventors. The primary distinction for this specific technology is the addition of co-dopants to affect the dielectric behavior of the barium titanatebased perovskite materials. These co-dopants include lanthanum and other rare earths as well as hydroxyl ions. The materials are processed at the nano scale, and are subjected to carefully designed thermal treatments as well. The presence of the hydroxyl ions has been shown to provide several orders of magnitude increase in the capacitance of the dielectric material. Additionally, these high capacitance values are obtained at relatively low voltages found in current consumer and industrial electronics. The capacitors tested to date are simple, single-layer devices. Ultimately, a range of manufacturing methods are possible for making commercial devices. Features of the technology enable manufacturing via traditional thick-film processing methods widely used in the capacitor industry, or via advanced printing methods for state-of-the-art printed electronics. Future efforts will be made to advance the manufacturing and packaging processes to increase device energy density, including multilayer devices and packages