Decarbonizing transportation through electrification requires less expensive, higher energy density batteries made from earth-abundant materials to displace internal combustion engines. Suitable solid-state electrolytes (SSEs) that facilitate lithium metal anodes by blocking Li dendrite formation represent a promising pathway to high-energy density cells. In a similar manner, SSEs that block the polysulfide shuttle could facilitate sulfur cathodes with even higher energy density that avoid issues of critical materials and supply chain constraints coupled to transition metal oxide-based cathodes.

Interest in solid-state batteries has increased rapidly in recent years. There are examples of solid-state batteries (SSBs) in commercial automotive applications; however, achieving wider adoption requires SSBs operating without the need for heating or excessive applied cell pressure. Several solid-state electrolyte chemistries (e.g., sulfides, ceramics, polymers, halides) are under development, but key issues remain unresolved in the case of each electrolyte chemistry.

The U.S. Department of Energy Vehicle Technologies Office supports R&D encompassing all of these candidate electrolytes for solid-state batteries through the Advanced Battery Materials Research program. The R&D portfolio prioritizes: improving electrolytes through modified composition or synthesis to increase room-temperature Li⁺ conductivity and mitigate Li dendrite penetration; improving interfaces to address chemical or electrochemical reactivity, to decrease impedance, and to improve Li plating and stripping; and improving suitability for high-volume manufacturing of solid-state lithium metal batteries by improving mechanical properties and demonstrating thin, defect-free, large-area SSE layers.

This presentation comprises solid-state lithium metal battery R&D priorities and accomplishments in the context of meeting DOE targets for energy density, cycle life, and cost. It will also emphasize the importance of SSBs to U.S. DOE strategy for increasing domestic lithium-based battery manufacturing and securing the U.S. position in next-generation battery innovation.