Polyaniline-coated partially unzipped vapor-grown carbon fibers/sulfur microsphere composites for Li–S cathodes

PUVGCF/S microspheres have been prepared using high-heat treatment with partially unzipped vapor-grown carbon fibers (PUVGCF) as the carbon precursor. The PUVGCF structure is formed via peeling and further lengthwise cutting with highly graphitized vapor-grown carbon fibers (VGCF) using a simple solution-based oxidative process. The composites of PUVGCF/S wrapped with polyaniline (PANi) are synthesized via an in situ oxidative polymerization of aniline using a liquid process. The microsphere structure not only shortens the electron and ion transport pathway but also provides mechanical support to accommodate volume expansion during the discharge/charge process. Additionally, the PANi coating layer further enhances conductivity of the electrode and prevents the polysulfides from dissolving in the electrolyte. Electrochemical measurements demonstrate excellent performance.