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Published online by Cambridge University Press: 01 February 2011
As the youngest battery chemistry, Li ion technology was made possible by the formation of stable electrode/electrolyte interfaces. The correlation between the electrochemistry and the surface profile of the graphitic anode was studied in this work with a new salt lithium bis (oxalate) borate (LiBOB).
In an attempt to depict a dynamic picture of the formation of graphite/electrolyte interface during the initial forming cycle, we employed X-ray photoelectron spectroscopy in combination with the “pre-formation” technique to establish the dependence of the surface chemistry on the forming potential of the anode. A progressive transition in the 1s electron binding energies of the major elements was observed as the lithiation proceeds; however, the surface chemical species as well as their abundances seemed to stabilize around 0.55 V and remained constant during the subsequent delithiation process, indicating that a stable solid electrolyte interface (SEI) exists thereafter. Integrating the information revealed by different analyses, we believe that the reductive decomposition of BOB−-anion starts at ca. 1.00 V, while the effective protection of graphene surface by SEI is available after the anode is lithiated below the potential of 0.55 V.