Surface chemistry and lithium storage capability of the graphite–lithium electrode

We show that the chemistry taking place on the surface of graphite-base negative electrode fixes for the most part the total capacity of a lithium-ion battery. A linear relationship between the reversible and the irreversible capacities has been established showing the interdependence between the lithium storage capability of graphite powders and the lost capacity due to surface chemistry. The latter leads to the formation of an SEI when EC solvent is used. Several tools were used to characterize the SEI including SEM, FTIR, XPS and AFM, and showed its very heterogeneous composition and its nonuniform morphology. Chemical formulations of the SEI formed on deeper a, b surfaces of HOPG are proposed together with a mechanism of the electrolyte decomposition.