Being able to observe lithium-ion batteries during operation could help scientists better understand the electrochemical and physicochemical phenomena at play—information that could then be used to enhance battery performance. Researchers at Liten developed a protocol for using XPS* to observe changes in the chemical composition of batteries during operation.

Until now, this type of observation entailed stopping the cycling test and autopsying the battery at various operating times. Researchers at Liten developed a special sample holder to connect the lithium-ion battery to a potentiometer so that the chemical changes at the electrolyte-electrode interfaces could be observed in real time. The researchers also came up with a workaround for using the spectroscope under ultra-vacuum: They used batteries with an ionic liquid electrolyte—less likely to evaporate under ultra-vacuum than conventional liquid electrolytes.

The protocol, called OXPS, was tested on micro-batteries (button batteries). The results obtained were corroborated by the results of direct observation completed in parallel. OXPS provides insights that can help researchers better understand the relationship between chemical (electron) structures and the degradation mechanisms that affect the electrolyte at the interfaces with electrode materials. Ultimately these new insights could lead to improved materials that enable more efficient energy conversion.

*XPS: X-ray photoelectron spectroscopy