Porous nanofibers comprising hollow Co3O4/Fe3O4 nanospheres and nitrogen-doped carbon derived by Fe@ZIF-67 as anode materials for lithium-ion batteries

Porous nanofibers comprising of Fe@ZIF-67-derived dual-phase Co3O4/Fe3O4 hollow nanospheres and N-doped graphitic C (N-GC) are prepared for high-performance lithium-ion battery anodes. Optimized ZIFs containing both Co and Fe ion nodes (Fe@ZIF-67) are prepared by the supplementation of additional Fe salt in the precursor solution of ZIF-67. The size of Fe@ZIF-67 is controlled by adjusting the pH value. Further, hollow-structured dual-phase Co3O4/Fe3O4 nanospheres in the structure are obtained through the mechanism involving Kirkendall diffusion nanoscale regime to as-spun fibers by performing simple heat treatments. The obtained unique nanostructure shows a high discharge capacity of 937 mA h g(-1) after the 150th cycle at 0.1 A g(-1) current density. Final discharge capacities of A300NF at different current densities of 0.1, 0.5, 1.0, 2.0, 3.0, and 5.0 A g(-1) are 806, 726, 593, 472, 388, and 287 mA h g(-1), respectively. Nanostructuring strategies proposed in this report have a considerable potential in opening new frontiers to high-performance anodes in energy storage systems.