Carbon-coated isotropic natural graphite spheres as anode material for lithium-ion batteries

Abstract

Carbon coated isotropic natural graphite spheres (INGS/C) has been prepared by spray granulation using the by-product of spherical natural graphite (i.e., superfine graphite powders) as starting materials. In INGS/C, small graphite flakes are packed in disordered orientation and form an isotropic structure, which may effectively reduce local stress concentration appearing in the process of Li+ insertion/extraction. The pyrolytic carbon decomposed from polyvinyl alcohol (PVA) and citric acid is connecting the small graphite flakes and coating on the surface of INGS, respectively, thus forms a continuous conductive network to improve the electron transmission and maintain the micro-structural integrity of isotropic natural graphite spheres as well. With the help of synergetic effect between the isotropic structure of INGS and the continuous conductive network, the INGS/C electrode exhibits superior rate capability of 346 mA h g−1 at 3 C at low potential below 0.25 V.