Researchers at the University of Chicago Pritzker School of Molecular Engineering (UChicago PME), along with visiting researchers from the University of California San Diego, have created materials that react to heat, pressure or electricity like any other material when they’re in their stable state, but their reactions are just the opposite when they’re in a metastable state.

Metastability is a state of steadiness in between stability and instability (or high potential energy), where energy is needed to “push” the material to full stability, but it cannot be pushed back to instability. Metastable materials can be quite durable—for example, diamonds are a metastable form of graphite.

“When you heat the materials, there’s no volume change,” said Y. Shirley Meng, UChicago PME Liew Family Professor in molecular engineering who is serving as the faculty director for the Energy Technology Initiative of the university’s newly launched Institute for Climate and Sustainable Growth. “When heated, the material shrinks instead of expanding.”

She goes on to say that the researchers believe they can “tune these materials’ properties through redox chemistry” to make them useful in a variety of applications, such as reviving old electric vehicle batteries.

“One of the goals is bringing these materials from research to industry, possibly developing new batteries with higher specific energy,” said Bao Qiu, visiting scholar at UC San Diego from the Ningbo Institute of Materials Technology and Engineering (NIMTE) and co-first author.

If the researchers can discover how to “fine-tune” the way materials react to heat and other forms of energy, they could create materials with zero thermal expansion, meaning they don’t expand when heated. This could have a significant effect on construction.

The researchers also tested how the material reacts to mechanical energy by compressing it on the gigapascal level—a pressure level typically used when discussing tectonic plate activity. They found “negative compressibility,” which correlates to negative thermal expansion in that, instead of shrinking when compressed, it expands.

Being able to resist heat and pressure opens up possibilities, such as structural batteries allowing an electric airplane’s walls to double as battery walls for a lighter, more efficient aircraft. These materials could also negate the impact of temperature and pressure changes on battery components.

Voltage creates the same reaction in the metastable materials.

“When we use the voltage, we drive the material back to its pristine state,” says UChicago PME research associate professor and study co-author Minghao Zhang. “We recover the battery.”

To drive the materials back from the metastable state to a stable state, you can use any sort of energy. This could eventually reset aging EV batteries by “pushing” the materials into their stable states using the electrochemical driving force.

“You don’t have to send the battery back to the manufacturer. You just do this voltage activation,” Zhang said. “Then, your car battery will be a new battery.”

Results of their current research were published in the journal Nature. Meanwhile, the researchers plan to continue to use redox chemistry to examine the materials further and explore the boundaries of this new area of research.