Resolving Interphases in Solid Electrolyte Batteries through Time-of-Flight Secondary Ion Mass Spectroscopy

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Non-Technical Summary: In today's society, new rechargeable battery technologies are urgently being developed to address the power and energy demands of the rapidly growing number of wireless devices, ranging from mobile communication to electric and hybrid vehicles. In particular, there is a pressing need for the development of safe, high performance, stable components for all-solid-state batteries. This project, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, investigates Li10GeP2S12 (LGPS) and Li7La3Zr2O12 (LLZO), two promising electrolyte materials, which are responsible for conducting the ions used to charge the batteries. The current problem is that these materials can trap Li ions and significantly change during battery operation, which, in turn, can severely limit their lifetime. Thus, this research project visually maps where the Li ions preferentially accumulate while the batteries are being used. To do this, Leite's and Wang's groups implement complementary microscopy techniques and correlate the acquired information with measurements of device performance. The outreach/education components of this research encompass: (i) mentoring graduate, undergraduate, and high school students, (ii) incorporating the scientific findings into lectures to enrich the curriculum of the Departments of Materials Science and Engineering and Chemical and Biomolecular Engineering at the University of Maryland, and (iii) engaging K-12 students in STEM by providing them with hands-on experiences on batteries during the Maryland Day, an open house event that attracts more than 60,000 people to campus. Technical Summary: The understanding and control of the relevant chemical reactions taking place during all-solid-state batteries cycling will enable the design of game-changing materials for energy storage based on Li, Na and Mg. This research elucidates the underlying mechanisms for the formation of solid-electrolyte interphases (SEIs) in two all-solid-state battery model systems with highly Li-ion conductive electrolytes: Li10GeP2S12 (LGPS) and Li7La3Zr2O12 (LLZO). This project, funded by the Solid State and Materials Chemistry program in the Division of Materials Research at NSF, advances the understanding of the materials chemistry that currently limits the performance of Li-ion all-solid-state batteries. The formation of SEIs is probed in situ by time-of-flight secondary ion mass spectroscopy (ToF-SIMS), combined with ex situ X-Ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). A correlation between the electrochemical impedance and the Li distribution maps reveals how the SEIs affect the interfacial resistance and, thus, the performance of these energy storage model systems. Determining Li preferential spatial distribution during cycling can potentially transform the future design of all-solid-state batteries, with controlled SEIs. While multiple in situ experiments have validated the formation of SEI in nanoscale batteries, there are no demonstrations of the dynamics of the mesoscale Li spatial distribution within all active layers of the batteries upon lithiation/delithiation. Thus, this research has scientific impacts in the field of materials chemistry and beyond. The outreach/education components of this research encompass mentoring students at various levels; incorporating the scientific findings into the curriculum of the Departments of Materials Science and Engineering as well as Chemical and Biomolecular Engineering at the University of Maryland; and engaging K-12 students in STEM by providing them with hands-on experiences on batteries during the Maryland Day, an open house event that attracts more than 60,000 people to campus.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.