M.N. Islam, S.C. Dey, M. Liu, J.S. Forrester, R.K. Bhardwaj, B. Tremolet de Villers, W.J. Sagues, S. Park
North Carolina State University,
United States
Keywords: Biographite, Pyrolysis, Catalytic graphitization, in situ XRD, PALS.
Summary:
Graphitic carbon materials derived from biomass are gaining increasing attention as sustainable alternatives to fossil-based anode materials for lithium-ion batteries. Despite this growing interest, the mechanistic pathway governing the transformation of amorphous biocarbon into highly crystalline graphite during catalytic graphitization remains incompletely understood. In this study, iron-catalyzed graphitization using zero-valent iron was systematically investigated to elucidate the catalytic transitions and graphitic structural development as a function of temperature. Ambient X-ray diffraction and Raman spectroscopy revealed progressive enhancement in graphitic ordering with increasing thermal treatment. Advanced high-temperature in-situ X-ray diffraction provided direct evidence that the γ-Fe phase transition initiates graphitic reorganization, while the subsequent formation of molten iron governs the development of highly ordered and stable graphite structures. Positron Annihilation Lifetime Spectroscopy (PALS) was uniquely employed to probe atomic-scale defect evolution during graphitization. A continuous decrease in positron lifetime with increasing temperature indicated reduced vacancy-type defects and improved lattice ordering. Notably, the material processed at 1500 °C demonstrated competitive electrochemical performance and structural features closely comparable to commercial graphite. This mechanistic insight provides a robust foundation for the rational design and scale-up of catalytic bio-graphitization processes, accelerating the development of high-performance, biomass-derived anode materials toward commercialization.