Carbon clusters decorated hard carbon nanofibers as high-rate anode material for lithium-ion batteries

Hard-soft composite carbons have shown great potential as one of the most promising anode materials for fast rechargeable lithium-ion batteries (LIBs). However, there is still a lack of systematic research about the influence of hard and soft carbons on rate performance. In this work, the influence of carbon microstructure on Li+ and electron transfer has been investigated thoroughly by controllable introduction of coal tar pitch (CTP) to polyacrylonitrile (PAN) in the electrospun carbon nanofibers (CNFs). The result indicates that the CTP derived carbon clusters introduced into low crystallinity carbon influence the electron transport and solid-state Li+ diffusivity simultaneously. As anode materials for LIBs, the enhanced electrical conductivity and balanced Li+ diffusion significantly improve rate performance. The composite CNFs exhibit a superior capacity retention of 53.7% from 0.1 to 5 A g−1, more than double of that for PAN-based CNFs. In addition, the composite CNFs present an ultra-stable cycle performance with 99.7% capacity retention at 1 A g−1 even after 1000 cycles. This work demonstrates that the balance between Li+ diffusion and electron transport plays a key role in lithium storage performance at high current density.