Electrochemical Property of Natural Graphite Anode Coated with High Softening Point Pitch Derived from FCC Oil Slurry

Natural graphite, characterized by its wide availability, low cost, relatively high specific capacity, and stable intercalation/deintercalation potential, is the primary anode material for commercial lithium-ion batteries. However, its intrinsic surface defects and poor compatibility with organic electrolytes often lead to significant degradation in reversible specific capacity, primarily due to solvent co-intercalation and consequent graphite layer exfoliation, resulting in unsatisfactory Coulombic efficiency and cycling performance. Surface modification represents an effective strategy to address these limitations. Pitch, an important by-product of the petroleum refining industry, is widely utilized as a coating material for graphite modification. Upon high-temperature cracking in an inert atmosphere, the pitch coating seals surface defects and forms an amorphous carbon shell on the graphite surface. This resulting core-shell structure effectively enhances the reversible specific capacity and cycling stability of graphite. In this study, high-softening-point pitch was synthesized from fluid catalytic cracking oil slurry via air purging under a nitrogen atmosphere followed by thermal polycondensation. This pitch was then employed as a coating agent to modify natural graphite through a liquid-phase coating process. Results indicate that a 10% (mass fraction) pitch coating forms a complete layer on the natural graphite surface, reducing its specific surface area and thereby improving both cycling and rate performance. The coated graphite exhibits a significantly enhanced capacity retention rate of 88.53% after 200 cycles at 0.5 C, compared to 69.01% for the pristine material, demonstrating superior electrochemical performance.