Resolving PC-Graphite Incompatibility via Steric-Hindrance-Directed Interfacial Regulation

Abstract

The incompatibility between propylene carbonate (PC) and graphite anodes, arising from detrimental Li+-PC co-intercalation and subsequent graphite exfoliation, remains a longstanding obstacle to the deployment of PC-based electrolytes in lithium-ion batteries despite their wide liquidus range and high dielectric constant. Herein, we report a novel interfacial regulation strategy that fundamentally resolves this challenge through steric-hindrance-directed interfacial regulation, enabled by 1 vol.% addition of octafluorotoluene (OFT). A combination of density functional theory calculations, molecular dynamics simulations, and comprehensive spectroscopic analyses reveals a unique adsorption-steric hindrance-weakening mechanism, OFT molecules preferentially adsorb onto the graphite surface via π-π stacking between their electron-deficient benzene rings and the delocalized π-electrons of graphite; The protruding –CF3 groups subsequently create a physical steric barrier that impedes PC approach, while simultaneously weakening Li+-PC coordination strength through intermolecular dipole-dipole interactions, thereby reducing the desolvation energy barrier. In situ optical microscopy directly visualizes the complete suppression of graphite exfoliation. Consequently, graphite electrodes employing the optimized electrolyte (1 M LiPF6/PC + 1% OFT + 5% FEC) deliver exceptional cycling stability with negligible capacity fade over 600 cycles and superior rate capability compared to conventional ethylene carbonate-based electrolytes. Furthermore, graphite||LiFePO4 pouch cells exhibit stable long-term operation with 86.2% capacity retention after 500 cycles at 0.5 C. This work establishes a novel strategy for electrolyte design, demonstrating that interfacial physicochemical synergy can unlock the practical potential of previously incompatible solvent systems, offering a generalizable design principle for wide-temperature-range and high-safety lithium-ion batteries.