Although most of our electronic devices, like mobile phones, laptops and electric vehicles use lithium rechargeable batteries, what is going on inside them is not fully understood. Researchers from the Center for Molecular Spectroscopy and Dynamics, within the Institute for Basic Science (IBS) succeeded in observing in realtime the ultrafast dynamics of lithium ions with femtosecond time resolution (1/1,000,000,000,000,000 of a second). These findings help to explain what happens during the process of charging and discharging: a cornerstone for the advanced batteries with better performance. Published on Nature Communications, this study reveals the interactions between lithium ions and electrolytes, which are organic molecules that surround the lithium ions and conduct electricity, and were able to conclude that the existing theory on ion diffusion in lithium rechargeable batteries is not completely correct.