Solid electrolyte interphase (SEI) formation behavior was carefully tracked on the well-defined edge and basal surfaces of carbon nanofibers. The effects of boron doping on SEI formation were also examined. Platelet carbon nanofibers (PCNFs) successfully afforded well-defined edge and basal surfaces. Surface morphology and chemistry were controlled by graphitization, nitric acid treatment and boron doping. The surface morphologies of various well-defined PCNFs were observed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The SEI of PCNF with edge surfaces was more abundant and four times thicker than those of PCNF-G and PCNF-B-G with basal surfaces. The SEI of PCNF-G-NA without boron doping was much more abundant and three times thicker than that of PCNF-B-G-NA with boron doping.