Lithium ions in battery electrolytes do not always remain isolated. Research from Columbia University shows they often form clusters without anions. It revealed a structural feature that challenges long-held assumptions about lithium-ion battery chemistry.

The study combines machine learning simulations with experimental validation to examine the atomic-scale structure of these electrolytes. Its findings could guide electrolyte designs for higher-capacity, faster-charging, and longer-lasting batteries.

The research was co-led by Richard Friesner of Columbia’s Department of Chemistry and Alexander Urban, Lauren Marbella, and Daniel Steingart of Columbia Engineering.

Electrolytes are crucial to battery performance and help drive the formation of the solid electrolyte interphase, a protective film on the battery anode. This film influences battery lifespan and safety, but understanding how electrolyte structure affects its formation has remained difficult.

To investigate that structure, the researchers used machine-learning force-field technology from Schrödinger, Inc., with additional support from the New York Structural Biology Center.

The approach let them simulate battery electrolytes more accurately and at a larger scale.

The simulations revealed that up to 40% of lithium ions in standard battery electrolytes form multi-ion clusters.

Clustering became more prevalent at higher salt concentrations, challenging the assumption that lithium ions remain predominantly isolated in solution.

“We discovered lithium ions in batteries actually group together into clusters in the absence of anions, and that these clusters are what drive the creation of the protective film on the battery’s surface,” said Friesner, William P. Schweitzer Professor of Chemistry.

The team compared its simulations with a wide range of condensed-phase experimental data.

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