IMDEA Materials researchers have made an important breakthrough in improving the safety of lithium-ion batteries (LIBs), powering everything from smartphones to electric vehicles.

In a bid to address the risks posed by thermal runaway, a dangerous failure mode that can lead to battery fires or explosions in LIBs, a recent research project from IMDEA Materials has presented a novel thermoresponsive electrolyte formulation.

This innovative research forms a major outcome of Dr. Arnab Ghosh’s Marie Skłodowska-Curie Actions project Smart electrolyte with inherent flame-retardancy for next generation fire-safe lithium-ion batteries (SMARTBATT). This breakthrough advances the vision set by the European Commission’s ‘Battery 2030+’ program to develop safe and sustainable batteries.

The details of the efficient thermal shutdown activities of the novel thermoresponsive electrolyte formulation are outlined in the research article “Deciphering a New Electrolyte Formulation for Intelligent Modulation of Thermal Runaway to Improve the Safety of Lithium-Ion Batteries,” published in Advanced Functional Materials.

In commercial LIBs, thermal runaway is typically controlled using temperature-responsive trilayer polypropylene/polyethylene (PP/PE/PP) separators. However, because of thermal shrinkage at approximately 160°C, these separators often fail to prevent thermal runaway in practical LIBs, where internal temperatures can easily exceed that range.

One way to solve this issue is the introduction of temperature-responsive electrolytes, including lower critical solution temperature electrolytes, which provide a promising alternative.

These electrolytes are designed to cease Li-ion transport within the battery immediately when a specific temperature threshold (generally 100–120°C) is exceeded, limiting internal temperature rises and reducing the risk of catastrophic failure due to thermal shrinkage of the trilayer separators.

Specifically, researchers have developed an electrolyte composed of a lithium salt dissolved in vinylene carbonate (VC) and 2,5-dimethylfuran (DMFu) that functions effectively in batteries at room temperature.

“At elevated temperatures, these thermoresponsive electrolytes have been shown to significantly reduce the Liion conductivity of the electrolyte and, at the same time, obstruct the micropores of the separator,” explains lead researcher, Dr. Ghosh.

“These dual effects allow for a two-step smart regulation of thermal runaway, initiating a warning phase at 100°C and achieving a complete thermal shutdown at 120°C, offering a built-in safeguard against the fire hazards of LIBs.”