Structural characterization of carbons obtained from polyparaphenylenes prepared by the Kovacic and Yamamoto methods

The structure of polyparaphenylene (PPP)-based carbons prepared by the Kovacic and Yamamoto methods heat-treated at 650-3000 degrees C have been characterized comparatively by using x-ray diffraction, SEM, TEM, and Raman spectroscopy. Both kinds of carbons indicate not typical but poor graphitizing behavior, especially for the case of PPP Yamamoto samples, and much less for PPP Kovacic samples, by heat treatment up to 3000 degrees C. The Kovacic-based samples heat-treated at 600-2400 degrees C have a more developed layer structure than that of Yamamoto-based samples. In contrast, for HTT's (heat-treatment temperature) more than about 2400 degrees C, PPP Yamamoto-based carbons exhibit a more developed crystallite structure than PPP Kovacic-based carbons, At a given HTT, PPP Kovacic-based carbons have a much more quinoid-like structure and graphene-type structure than PPP Yamamoto-based carbons, as indicated by the carbon yield and Raman scattering measurements. It is suggested that the detailed structure of the starting polymers influences the texture as well as the microstructure of resultant carbons even though both are obtained from the same kinds of precursors. These microstructures also largely influence the anode performance when these carbons are used in Li ion batteries.