Evaluating carbochlorination for processing natural flake graphite into Li-ion battery-grade graphite

Chlorination was evaluated as a HF-free purification step within the conversion process of natural flake graphite (NFG) into coated spherical purified graphite (CSPG) for Li‑ion battery anodes. Two industrially realistic sequences were compared: chlorination before micronization–spheroidization (MS) and chlorination after MS. Processing used caustic leaching followed by carbochlorination, jet milling micronization and autogenous impact spheroidization, and petroleum‑pitch coating/carbonization. Detailed characterization was performed at each step of the processing. Carbochlorination raised purity to 99.98 wt% in both routes while preserving the graphitic structure as confirmed by X-ray diffraction and Raman spectroscopy analyses. MS produced spherical particles (median size ⁓17 µm, median circularity ⁓0.90). Pitch coating/carbonization lowered the surface area to ∼2 m2 g‑1 and led to a tap density of ∼1.1 g cm‑3. Half‑cell testing showed similar electrochemical performance for both routes with an initial coulombic efficiency of ⁓93 % and a reversible capacity of ⁓360 mAh g‑1 after 90 cycles, closely matching a commercial CSPG. Differences between the sequences were thus minor, indicating that carbochlorination can be flexibly integrated into industrial CSPG flowsheets. The findings support chlorination as a scalable, HF‑free purification alternative to produce battery-grade natural graphite.