Engineering the Metal Sulfide Interface in All Solid State Batteries through Operando Study

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There is a critical need for improved energy storage technologies for electric vehicles and large-scale integration of renewable electricity grid storage to improve domestic energy security. Currently, state-of-the-art energy storage technologies such as lithium ion batteries are insufficient in providing the performance requirements needed such as cost and energy density to enable broad use. Battery chemistries using high energy density electrodes and solid-state electrolytes could provide an avenue towards gains in energy density and durability for these applications. This project is a fundamental research study of solid-state electrolytes, a key component that enables these high energy density battery chemistries along with safety and durability benefits. Sulfide composites are promising as solid electrolytes in all solid-state batteries due to their high ionic conductivity and favorable mechanical strength features. However, sulfide solid electrolytes still face challenges that limit their use. This project will result in fundamental understanding of the mechanisms and material interactions of metal sulfides in all solid-state batteries. The research will guide improvements to material design, improved electrolytes and electrodes, and eventually lead to improved designs for high energy, solid-state batteries. Society will also benefit from the training of highly qualified researchers who will be able to continue technology improvements in creating large-scale energy solutions from science, technology, engineering, and math disciplines.The specific objective of this research is to improve metal sulfide stability in solid-state electrolytes for the application of all solid-state lithium batteries. In pursuit of this objective, the fundamental mechanisms of metal sulfide ion conduction and interface reactivity will be interrogated by operando characterization carried out on realistic, fully operational battery cells. This will reveal the critical materials evolution processes occurring at buried interfaces within sealed devices during cycling. The findings will be used to modify the metal sulfide chemistry through elementary doping and to stabilize the interface through interface engineering. This will be accomplished by the convergent effort of two research groups, one with expertise in synthesis and materials engineering, interface stabilization, and cell modification, and one skilled in operando characterization and modeling of batteries. The methodology in this work ? combining materials synthesis and evaluation, operando device characterization, and computation ? will lead to an in-depth understanding of the thermodynamic, kinetic, electrochemical, chemomechanical, and structural stability of metal sulfide all solid-state batteries.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.