Formation of the graphite electrolyte interface by lithium bis(oxalato)borate

Solid electrolyte interface (SEI) formed on graphitic anode in electrolyte containing a salt, lithium bis(oxalato) borate (LiBOB), was investigated using electrochemical means, and an irreversible reduction process was found for LiBOB on graphitic anode at ca. 1.6 V vs. Li. To ascertain whether this process is responsible for the unique LiBOB property in stabilizing graphene structure against propylene carbonate (PC), we systematically interrupted the lithiation of graphitic anodes in LiBOB-electrolytes at a series of potentials and then tested the survivability of these preformed anodes in PC solution of LiPF6, an electrolyte composition known to exfoliate graphite materials readily. The results demonstrate that the formation of a functioning SEI is completed at potentials around 0.50 V vs. Li, and confirmed that BOB-anion plays a critical role in the effectiveness of the formed SEI to protect the graphene structure from exfoliation even in PC. (C) 2003 The Electrochemical Society.