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 the addition of 1 vol% 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 the 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 significant suppression of graphite volume expansion during cycling. 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 0.5C. 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.