Enhanced Diffusion Kinetics of Li Ions in Double-Shell Hollow Carbon Fibers.

The rational design and preparation of hierarchical hollow structures have promising potential in electrochemical energy storage systems. In this paper, double-shell hollow carbon fibers (DSHCFs) with tunable thickness and shell spacing are prepared using hollow electrospun polystyrene fibers as the hard template and in situ coated polypyrrole as the carbon source. The as-prepared DSHCFs with an optimized structure exhibit a submicrometer shell spacing and a nanoscaled shell thickness, which guarantees sufficient contact area with the electrolyte and provides abundant electrochemical active sites for Li+ storage. Owing to the unique structural advantages, a DSHCF-based anode shows favorable transport kinetics for both Li+ ions and electrons during the lithiation/delithiation process, and a high reversible capacity of 348 mAh g-1 at 5.0 A g-1 is well maintained even after 500 cycles with no obvious capacity attenuation. Particular emphasis is given to kinetic Li+ storage mechanisms in DSHCFs that are discussed in detail, providing a new avenue for developing high-performance carbon materials for the practical application of energy storage devices.