Porous Carbon Nanofibers Encapsulated with Peapod-Like Hematite Nanoparticles for High-Rate and Long-Life Battery Anodes.

Fe2 O3 is regarded as a promising anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) due to its high specific capacity. The large volume change during discharge and charge processes, however, induces significant cracking of the Fe2 O3 anodes, leading to rapid fading of the capacity. Herein, a novel peapod-like nanostructured material, consisting of Fe2 O3 nanoparticles homogeneously encapsulated in the hollow interior of N-doped porous carbon nanofibers, as a high-performance anode material is reported. The distinctive structure not only provides enough voids to accommodate the volume expansion of the pea-like Fe2 O3 nanoparticles but also offers a continuous conducting framework for electron transport and accessible nanoporous channels for fast diffusion and transport of Li/Na-ions. As a consequence, this peapod-like structure exhibits a stable discharge capacity of 1434 mAh g-1 (at 100 mA g-1 ) and 806 mAh g-1 (at 200 mA g-1 ) over 100 cycles as anode materials for LIBs and SIBs, respectively. More importantly, a stable capacity of 958 mAh g-1 after 1000 cycles and 396 mAh g-1 after 1500 cycles can be achieved for LIBs and SIBs, respectively, at a large current density of 2000 mA g-1 . This study provides a promising strategy for developing long-cycle-life LIBs and SIBs.