Insight into the Role of Fluoroethylene Carbonate in Solid Electrolyte Interphase Construction for Graphite Anodes of Lithium-Ion Batteries

The role that fluoroethylene carbonate (FEC) plays in the construction of the solid electrolyte interphase (SEI) on graphite anodes of lithium-ion batteries is understood by theoretical calculations combined with electrochemical measurements and spectral characterizations. It is found that FEC is different from ethylene carbonate (EC), although they have a similar structure. FEC presents a stronger ability than EC to combine with PF6–, which is helpful for the reduction of LiPF6 to construct a LiF-rich inner layer of SEI. Additionally, FEC has a more negative electron affinity than EC, which makes it much easier to reduce, resulting in F-containing polymers that contribute to the outer layer of SEI. Consequently, the FEC-constructed SEI endows the graphite anode with excellent cycling stability.