Enhancing the Cycling Stability of Graphite Anodes Using a Dense Fluorine-Containing Thiophene-Based Electrolyte Additive

Abstract A pentafluorophenyl- and thiophene-functionalized imine compound, pentafluorophenyl thiophene imine (FPTI), was investigated as an electrolyte additive in graphite/Li half-cells to enhance interfacial stability and electrochemical performance. The incorporation of FPTI facilitates the formation of a robust solid electrolyte interphase (SEI), characterized by reduced activation energy, lower charge-transfer resistance, and enhanced lithium-ion diffusion kinetics. As a result, the FPTI-containing cells exhibit a high-capacity retention of 95.6% at 0.5 C. Differential voltage and differential capacity analyses provide mechanistic insights into capacity fading, highlighting the suppression of parasitic side reactions in anodic half-cells. X-ray photoelectron spectroscopy (XPS) confirms the presence of sulfur- and imine-derived species within the SEI, indicating the active participation of FPTI in interphase formation. Furthermore, full-cell evaluation demonstrates an energy density of 233 Wh kg–1 at an optimal additive concentration of 4 mg mL–1.