​One of the factors that can affect lithium-ion battery lifespans is lithium plating—the formation of metal lithium on the graphite negative electrode. Researchers at Liten, a CEA Tech institute, worked with CEA institute IRIG to characterize the lithium using NMR spectroscopy. The method developed aims to detect the formation of metal lithium in real time to provide a deeper understanding of the mechanisms that underpin the degradation of the negative electrode.

Until now, this type of characterization has been completed ex situ on samples of electrodes taken post mortem. However, lithium plating continues to evolve even after operation of the battery element ceases. The researchers developed a laboratory cell with a design similar to that used in commercially-available batteries but scaled down so that it could be inserted into the NMR coil, which was also modified for the experiment.

Several in operando tests were completed in a variety of conditions. The encouraging results obtained will provide new insights into how metal lithium is formed on the negative electrode so that charge protocols capable of limiting the phenomenon can be determined. This information will then be integrated into battery management systems (BMS) with the goal of extending battery lifespans or used to design electrodes less sensitive to this particular degradation mechanism.