Rationally designed hierarchical porous CNFs/Co₃O₄ nanofiber-based anode for realizing high lithium ion storage

To achieve a high power density of lithium-ion batteries, it is essential to develop anode materials with high capacity and excellent stability. Cobalt oxide (Co₃O₄) is a prospective anode material on account of its high energy density. However, the poor electrical conductivity and volumetric changes of the active material induce a dramatic decrease in capacity during cycling. Herein, a hierarchical porous hybrid nanofiber of ZIF-derived Co₃O₄ and continuous carbon nanofibers (CNFs) is rationally constructed and utilized as an anode material for lithium-ion batteries. The PAN/ZIF-67 heterostructure composite nanofibers were first synthesized using electrospinning technology followed by the in situ growth method, and then the CNFs/Co₃O₄ nanofibers were obtained by subsequent multi-step thermal treatment. The continuous porous conductive carbon backbone not only effectively provides a channel to expedite lithium ion diffusion and electrode transfer, but also accommodates volume change of Co₃O₄ during the charge-discharge cycling process. The electrode exhibits a high discharge capacity of 1352 mA h g^-1 after 500 cycles at a constant current density of 0.2 A g^-1. Additionally, the composites deliver a discharge capacity of 661 mA h g^-1 with a small capacity decay of 0.078% per cycle at a high current density of 2 A g^-1 after 500 cycles. This hierarchical porous structural design presents an effective strategy to develop a hybrid nanofiber for improving lithium ion storage.