Melt-Spinning Mesophase Pitch-Based Graphite Fibers as Anode Materials for High-Rate Lithium-Ion Batteries

Abstract

Lithium-ion batteries have rapidly become the most widely used energy storage devices in mobile electronic equipment, electric vehicles, power grid energy storage devices and other applications. Due to their outstanding stability and high conductivity, carbon materials are among the most preferred anode materials for lithium-ion batteries. In this study, mesophase pitch-based graphite fibers (GFs) were successfully prepared through melt-spinning, thermo-oxidative stabilization, carbonization and graphitization and used as anode materials. The radial fiber structure can lower the activation energy and minimize the distance of the Li+ diffusion, while the highly conductive cross-linked network within the fibers benefits the speed up charge transmission. Thus, the as-synthesized graphite fibers demonstrate superior rate capability and cycle stability. GFs exhibit a capacity retention rate of 97.94% and reversible capacity of 327.8 mA h g−1 after 100 cycles at 0.1 C, which is higher than that of natural graphite anode materials (85.66% and 289.7 mA h g−1, respectively). Moreover, the as-synthesized graphite fibers deliver a capacity retention of 64.7% at a high rate of 5 C, which is considerably higher than that of natural graphite (19.7%).