In Situ Transformed Solid Electrolyte Interphase by Implanting a 4‑Vinylbenzoic Acid Nanolayer on the Natural Graphite Surface

A solid electrolyte interphase (SEI) layer on a graphite anode plays a crucial role in deciding electrochemical properties of the electrode including the first Coulombic efficiency, rate capability, operating temperature, and long-term cycling stability. However, the ultrathin functional SEI layer is always naturally grown via electrolyte reduction decomposition reactions. Herein, we report a new strategy of in situ transformed solid electrolyte interphase of high stability by implanting a 4-vinylbenzoic acid (4-VBA) nanolayer on a mildly oxidized graphite surface. A 4-VBA layer of 40 nm contributes to the transformation of a robust and stable SEI layer, which not only significantly enhances the overall electrochemical performances of the natural graphite electrode but also greatly prolongs the cycle life of the full cell with the LiNi_0.6Co_0.2Mn_0.2O₂ cathode. The effectively suppressed surface evolution aroused from the stable organic SEI transformed from the implanted 4-VBA nanolayer explains the enhanced electrochemical properties.