Influence of Pitches with Different Softening Points on the Coating Properties of Natural Graphite

Three petroleum-based pitches with different softening points were used to treat natural graphite by liquid phase coating method. The particle size, structure, morphology and electrochemical properties of the samples were analyzed. The results showed that the high softening point pitch could form a thicker coating layer on the natural graphite surface, and the graphite surface became more rounded and the defects were reduced. The pitch coated natural graphite with softening point 250 ℃ showed the best electrochemical performance, the first Coulomb efficiency increased from 84.70% to 88.04%, and the capacity retention rate increased from 63.14% to 81.19% after 250 cycles. The low softening point pitch had a large irreversible capacity loss due to the large number of micropores formed by the light component releasing during carbonization, while the high softening point pitch was beneficial to the formation of complete coating, which could improve the cyclic property and rate property of natural graphite best.