Novel self-assembled natural graphite based composite anodes with improved kinetic properties in lithium-ion batteries

Novel self-assembled natural graphite composites (SANGs) were prepared by the granulation of natural graphite and styrene/acrylonitrile copolymer (SAN) particles by a spray-drying and subsequent pyrolysis procedure. In this work, monodispersed SAN particles with high residual carbon contents were prepared by the dispersion polymerization of acrylonitrile and styrene using the mixture initiators of 2,2′-azobis(isobutyronitrile) and benzoyl peroxide in the presence of polyvinylpyrrolidone in ethanol. The morphology and structure of SAN particles and SANGs were characterized by scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and Raman spectroscopy. The residual carbon contents and the pyrolytic carbon composition of SAN particles were characterized by thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). The as-prepared SANGs present more improved kinetic properties than those of natural graphite when used as anodes in Li-ion batteries. It is due to the self-assembled morphology of SANGs, which improves the less anisotropic transport of Li ions and facilitates the electrochemical kinetics during cycling.