Mixed Conducting Cathodes and Dense Electrolytes for Solid-State Batteries
Power Generation and Storage
Mixed Conducting Cathodes and Dense Electrolytes for Solid-State Batteries (LEW-TOPS-186)
Novel Technique and Formulation for Safe, Efficient, and High-Energy Li-S Batteries
Overview
NASA’s SABERS 2.0 (Solid-state Architecture Batteries for Enhanced Rechargeability and Safety) project aims to improve the state of the art for battery efficiency, power, and safety. Current lithium-ion batteries use liquid electrolytes that connect to the active material. However, these electrolytes are highly volatile and flammable, which can cause catastrophic failures and carry safety risks that may impact mass-market desirability. Solid-state batteries use solid electrolytes with better conduction abilities, making them a sound alternative to lithium-ion designs, but these often contain complex cathodes that have inefficient energy pathways and can be difficult to build at scale.
Teams at NASA’s Glenn Research Center have created two complementary SABERS innovations to improve solid-state batteries’ performance and safety: a low-temperature electrolyte densification process and a catholyte formulation that simplifies the path of conduction and reduces the number of required interfaces. These innovations work in conjunction to increase electrolyte density while simultaneously increasing cathode porosity, resulting in solid-state battery concepts with increased energy density combined with the safety improvements of higher tolerances.
The Technology
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).
Benefits
- Simplified Cathode Design: Reduces components from three (active material, ion conductor, electron conductor) to two, making manufacturing easier and less costly.
- Enhanced Safety: Eliminates flammable liquid electrolytes, reducing risk of thermal runaway and short-circuiting.
- Better Ion/Electron Transport: Mixed conductors reduce tortuosity (complex pathways), improving charge/discharge efficiency.
- Improved Ionic Conductivity: Fewer voids make ion charge pathways smoother, boosting battery performance.
- Extended Cycle Life: Stronger, less porous electrolytes resist degradation during repeated charging cycles.
- Higher Energy Capacity: Low-temperature densification creates materials that could deliver up to five times more energy than current lithium-ion batteries.
Applications
- Electric Vehicles: Enables high-capacity and reliable batteries for longer driving ranges and improved safety.
- Electric Aircraft: Improved reliability and energy storage necessary for aviation, enhancing efficiency, sustainability, and performance.
- Spacecraft: Improved reliability and energy storage necessary for spaceflight, reducing the need for servicing and refueling.
- Industrial Robotics: Safe and high-energy batteries enable longer operational periods, support manufacturing timelines, and enhance employee protection.
- Advanced Energy Storage Systems: Enable next-generation batteries for grid-scale energy storage with higher capacity and lower hazard risk.
Technology Details
Power Generation and Storage
LEW-TOPS-186
LEW-20610-1
LEW-20611-1
Donald A. Dornbusch, Rocco P. Viggiano, John W. Connell, Yi Lin, Vadim F. Lvovich,
Practical considerations in designing solid state Li-S cells for electric aviation,
https://doi.org/10.1016/j.electacta.2021.139406.
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