A Generalized Ultrasonic Inspection Method for Batteries

Astronauts' lives depend on the safe performance and reliability of lithium-ion (Li-ion) batteries when they are working and living on the International Space Station. These batteries are used to power everything such as communications systems, laptop computers, and breathing devices. Their reliance on safe use of Li-ion batteries led to the research and development of a new device that can more precisely trigger internal short circuits, predict reactions, and establish safeguards through the design of the battery cells and packs. Commercial applications for this device exist as well, as millions of cell phones, laptops, and electronic drive vehicles use Li-ion batteries every day. In helping manufacturers understand why and how Li-ion batteries overheat, this technology improves testing and quality control processes. The uniqueness of this device can be attributed to its simplicity. In a particular embodiment, it is comprised of a small copper and aluminum disc, a copper puck, polyethylene or polypropylene separator, and a layer of wax as thin as the diameter of one human hair. After implantation of the device in a cell, an internal short circuit is induced by exposing the cell to higher temperatures and melting the wax, which is then wicked away by the separator, cathode, and anode, leaving the remaining metal components to come into contact and induce an internal short. Sensors record the cell's reactions. Testing the battery response to the induced internal short provides a 100% reliable testing method to safely test battery containment designs for thermal runaway. This jointly developed and patented technology is available for your company to license and develop into a commercial product. NASA does not manufacture products for commercial sale.

Battery cells are sealed inside a strong, flexible pouch which is placed inside a lightweight pressure vessel filled with inert working fluid (e.g., argon gas, silicone oil) that applies a low pressure evenly around the pouch, ensuring uniform compression and eliminating directional stress on the cell. This case maintains constant pressure throughout the battery’s life cycle to ensure consistent contact between solid components, which optimizes performance and minimizes damage. The pressure necessary in this design is much lower than that in uniaxial systems, which allows for a less heavy packaging system. This lightweight design and improved technique may show particular relevance on large scales (e.g., aerospace, automotive), where onboard load weight and longevity are priorities. This isostatic battery case contributes to the SABERS 2.0 portfolio (LEW-TOPS-188), improving the state of the art for solid-state batteries. Currently at a TRL 4, the case is available to license independently or as part of the larger SABERS solid-state battery suite.

The technology utilizes photopolymer droplets (invisible to the digital radiograph) with embedded radiopaque fragments to create randomized fingerprints on battery samples. The droplets are deposited using a jig (see figure on right) that precisely positions samples. Then, at different points during battery R&D testing or use, digital radiography imaging with micron-level resolution can be performed. The high-resolution imaging required to detect dendrite formation requires images to be collected in multiple “tiles” as shown below. The randomized fingerprints uniquely identify relative positioning of these tiles, allowing rapid assembly of composite high-resolution images from multiple tiles. This same composite creation process can be used for images taken at a series of points in time during testing, and background subtraction can be applied to efficiently compare how the battery is changing over successive charge/discharge cycles to identify dendrite formation. This inspection technique is proven effective for thin-film pouch cell prototypes at NASA, and it works well at the lowest available x-ray energy level (limiting impact on the samples). The Fingerprinting for Rapid Battery Inspection technology is available for patent licensing.

The interlayer consists of lithiophilic metallic or metal-containing nanoparticles supported on holey graphene, a special carbon material perforated by small holes that enables dry processing. The composite interlayer guides uniform lithium deposition and maintain stability during cycling. The result is a thin, film-like material that can be integrated (via dry processes) into battery cells as standalone interlayers or combined with solid electrolyte and cathode powders to form bi- and tri-layer structures, separating anodes and electrolytes while encouraging efficient ionic movement and long cell lifecycles. Tests found that battery cells incorporating this dry-processed interlayer achieved ultrahigh current density and low overpotential, indicating that the interlayer prevents rough patches, resists dendrite formation, and supports efficient charge and discharge over time. The interlayer has demonstrated a high lithium-ion flux (i.e., a high critical current density of ~25 mA/cm²) and has shown that full battery cells incorporating the protective layer can be successfully cycled (with an areal capacity of 7 mAh/cm²). This innovation contributes to both the SABERS (LEW-TOPS-167) and SABERS 2.0 (LEW-TOPS-188) portfolios, improving the state of the art for solid state batteries. The anode interlayer is currently at a TRL 4 and is available to license independently or as part of the larger SABERS solid-state battery suite.

The first technique improves electrolyte densification, which is essential for ion conductivity and battery reliability overall. The process involves the use of a sintering aid (e.g., sulfur) to achieve denser and more stable electrolytes than are achievable through more common, high-temperature processes. Electrolytes that are denser and less porous have higher ion conductivity (thus better performance), longer cycle lives, and lower volatility. Aside from densification, this technique also significantly increased the base electrolyte's lithium wettability. The second innovation is a new cathode and electrolyte design using a mixed conducting material that can carry both ions and electrons, which simplifies the cathode’s composition by eliminating the need for separate ion and electron conductors. This catholyte is a composite that utilizes a mixed conducting material, replacing both the ion and electron conductors with a single material thus simplifying solid state cathode design from a 3-component to 2-component composite. The mixed material is composed of a metal chalcogenide, such as titanium disulfide (TiS2), which can act as a mixed conductor and contributes to energy storage. The addition of sulfur boosts energy capacity up to 33% compared to traditional cathode designs. Reducing single-conduction phases simplifies energy transport pathways and improves efficiency, making solid-state batteries easier to produce and safer to use. These two innovations work together to improve the state of the art, creating solid-state batteries with higher temperature tolerances and up to five times more energy capacity than current lithium-ion batteries. They stand together at a TRL 4 and are available for patent licensing individually or as part of the larger SABERS (LEW-TOPS-167) or SABERS 2.0 portfolio (LEW-TOPS-188).