[Image above] Yuxin Chen, graduate student instructor and graduate student research assistant in mechanical engineering at the University of Michigan, verifies the charge of lithium metal in a solid-state battery. Credit: Robert Coelius, University of Michigan Engineering
By Laurel Sheppard
Transforming the way energy is collected, stored, and used has been a defining challenge of the 21st century. That’s why, in 2009, the U.S. Department of Energy’s Office of Basic Energy Sciences established the Energy Frontier Research Center (EFRC) program.
The EFRC program supports major collaborative research efforts to accelerate high-risk, high-reward fundamental research that will provide a strong scientific basis for future transformative energy technologies. Since the program’s inception, there have been 88 EFRCs, of which 41 are currently active.
In August 2022, the University of Michigan announced they and eight partner institutions will lead a new $10.95 million EFRC called the Mechanochemical Understanding of Solid Ion Conductors (MUSIC) research center. It will explore the use of ceramic ion conductors as replacements for the traditional liquid electrolytes in lithium-ion batteries.
Lithium-ion batteries are the foundation for today’s electric vehicles and renewable energy technologies. However, such batteries have several shortcomings, particularly with regards to safety. Li-ion batteries have a tendency to overheat and can be damaged at high voltages, which in extreme cases can lead to thermal runaway and combustion.
Safety of Li-ion batteries can be greatly improved by switching the traditional liquid electrolyte with a solid ceramic electrolyte. It also allows the battery to charge faster and weigh less.
However, a better understanding of solid electrolyte properties—such as its mechanical-chemical interactions with other battery components—is required to achieve an optimized battery design.
In the University of Michigan announcement, Neil Dasgupta, MUSIC’s deputy director and associate professor of mechanical engineering, explains that an overarching goal of MUSIC is “to reveal the fundamental mechanisms of how mechanical stresses and strains interact with electrochemistry, which will inform future efforts to scale-up and accelerate commercialization of next-generation energy storage technology.”
Interfacial stability between the electrolyte and electrode will be a big focus at MUSIC. As explained in a recent review paper published in Current Opinion in Green and Sustainable Chemistry, “While significant progress in SSEs [solid-state electrolytes] has led to ionic conductivity and electrochemical window close to or even better than those of liquid electrolytes, poor interfacial stability between SSEs and electrodes during charging and discharging tends to deteriorate the cycle life of SSLBs [solid-state lithium batteries], which calls for a deep understanding of the interface evolution.”
While that paper emphasized the importance of in situ characterization techniques, such as microscopy and spectroscopy methods, to understanding failure mechanisms at the interface, it also noted that combining techniques likely will be necessary to obtain a full picture of interface mechanisms and provide guidance for interfacial design.
Lithium is not the only solid-state battery composition under investigation. All-solid-state sodium batteries are a potentially more sustainable and low-cost alternative to lithium. Currently, though, the only successfully commercialized sodium battery is a high-temperature sodium–sulfur battery that requires working temperature above 300°C, so both the sodium anode and sulfur cathode are in a liquid rather than solid state.
The challenge with developing a solid sodium battery is the electrolyte. When the sodium metal anode is in a solid state, the solid electrolyte now must be not only resistant to direct chemical and electrochemical reactions with sodium but also resistant to solid metallic sodium dendrite penetration.
In recent years, researchers have explored a variety of materials for use as electrolytes in all-solid-state sodium batteries. In July 2022, CTT covered work led by an ACerS Fellow on an oxysulfide glass electrolyte. Work on this topic as well as other solid-state configurations will take place at MUSIC in addition to the lithium research.
With so much still to learn about solid-state batteries, likely the hardest part for MUSIC researchers will be selecting which of countless experiments to conduct. Fortunately, “We have decades of fundamental research into ion conduction in ceramics to work with,” says Dasgupta.