New technique allows recycling components of solid-state batteries over and over again

Researchers at Penn State University have successfully applied cold sintering to the solid and liquid electrolyte components of solid-state batteries to recycle them. Solid-state lithium batteries are energy-dense, safe, nonflammable and can be used in electric vehicles, wearable devices or laptop batteries.

Cold sintering is the process of combining powder-based materials into dense forms at low temperatures through applied pressure using solvents allowing for materials to be recycled again and again. The technique was developed in 2016 by a team of researchers led by Clive Randall, director of Penn State’s Materials Research Institute.

“Defects in batteries, such as voids and cracks caused by mechanical stress on the solid-state electrolytes, may block lithium-ion transport pathways and lead the battery to short circuit,” said Yi-Chen Lan, doctoral student in chemical engineering and first author on a paper explaining the recent findings and published in the journal ChemSusChem.

“To recycle electrolytes that have undergone mechanical degradation, we use cold sintering to re-densify the microstructures and reprocess composite electrolytes by mixing ceramics with polymers and lithium salts.”

The idea for cold sintering the liquid electrolytes needed in solid-state batteries came about in 2018, when a postdoctoral scholar in the lab led by Enrique Gomez, professor of chemical engineering in the Penn State College of Engineering, accidentally broke a sample of liquid electrolyte during an experiment.

“He decided to reprocess the electrolyte sample through cold sintering, and we found out it worked just as well after being reprocessed,” Gomez said. “We didn’t realize at the time that this was a concept we could exploit, and that was the birth of this paper.”

According to the researchers, reprocessing and reusing the electrolytes leads to lower energy consumption and a lesser environmental impact over time, which in turn promotes the viability and sustainability of all-solid-state battery types.

In another paper published in MRS Communications, the researchers cold sintered a composite that goes into capacitors, which are important components of electric vehicles. In the experiments, they combined the ceramic barium titanate with Teflon or polytetrafluoroethylene.

“Our work in MRS Communications demonstrates the potential for recycling materials that will be crucial for the electrification of transportation, and therefore the reduction of greenhouse gases,” said Hongtao Sun, co-corresponding author on the paper.