Meaning
Surface-sensitive analytical technique irradiates a material sample with a beam of X-rays while measuring the kinetic energy and number of electrons that escape from the top few nanometres of the surface. Researchers utilize XPS to determine the chemical composition and electronic states of the elements present in the solid electrolyte interphase of lithium-ion batteries. Identifying these surface films allows battery developers to identify the specific organic and inorganic compounds that form on the electrodes during initial cycling.
Surface Resolution
Detection limits are extremely sensitive to the top surface layers. Because the escape depth of the photoelectrons is less than ten nanometres, the XPS measurements provide a precise picture of the interface without interference from the underlying bulk electrode material. This allows for the tracking of electrolyte decomposition products as they build up during cycling.
Argon Sputtering
Depth profiling uses a beam of argon ions to remove surface material layer by layer. This reveals how the composition of the solid electrolyte interphase changes from the outer electrolyte boundary to the inner electrode surface. These profiles show the distribution of lithium fluoride, carbonates and other degradation products through the film thickness.
Chemical State
Peak shifts in the spectrum identify the oxidation state of the surface elements.
