Composite Cathodes for All-Solid-State Batteries Containing Lithium Thiophosphate Separators

Abstract

Li-based solid-state batteries (SSBs) have gained significant interest due to their potential for improved energy density and safety compared to Li-ion systems containing liquid electrolytes. A major challenge for SSBs is development of solid electrolytes (SEs) which meet several key requirements including: (i) high Li+ conductivity (ca. 1–10 mS/cm at room temperature), (ii) good compatibility with Li metal anodes and high energy cathodes, and (iii) ability to be scalably processed into thin separators (<30 µm thick) for practical devices. A wide range SE classes including oxides, sulfides, and polymers have been developed, but no single material has been able to satisfy all the requirements for Li metal batteries. A promising class of SEs include lithium thiophosphates which have room temperature Li+ conductivities exceeding 1 x 10–4 S/cm and can be prepared using scalable solvent-mediated routes. However, integrating these materials into SSBs containing high voltage cathodes remains challenging due to the SE’s poor oxidative stability. This presentation will describe recent studies on SSBs containing Li metal anodes, lithium thiophosphate SEs, and various cathodes. The effects of different active materials (e.g., NMC and FeS2), carbon additives, and stack pressure on the reversible capacity and cyclability of the composite cathodes will be discussed. In-situ stress evolution measurements related to volume changes in the cell will also be highlighted. Acknowledgements This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) through the Vehicle Technologies Office (VTO).