Electrospun carbon nanofibers embedded with heterostructured NiFe2O4/Fe0.64Ni0.36 nanoparticles as an anode for high-performance lithium-ion battery

Binary transition metal compounds exhibit promising application potential as anode materials in the field of lithium-ion batteries (LIBs) due to their high theoretical specific capacity. However, their poor electrical conductivity and drastic volume expansion during charge and discharge pocesses limit their high-performance applications. Herein, we have synthesized carbon nanofibers (CNFs) loaded with heterostructured NiFe based nanoparticles (NiFe2O4/Fe0.64Ni0.36@CNFs) using electrospinning, and explore their cyclic stability and rate performances. By subjecting the electrospun membranes to thermal treatment at different annealing temperatures, three distinct phases of NiFe compounds embedded in CNFs, i.e., NiFe2O4 (400 °C), NiFe2O4/Fe0.64Ni0.36 (500 °C) and Fe0.64Ni0.36 (800 °C), are obtained. When they are used as anode materials, the electrochemical properties are investigated. The NiFe2O4/Fe0.64Ni0.36@CNFs anode material exhibits the best cycling and rate performances, with a capacity of 431.1 mAh g−1 achieved after 200 cycles at a current density of 0.2 A g−1. Moreover, its specific capacities are 558.9, 400.1, 272.4, 178.1 and 89.5 mAh g−1 at current densities of 0.1, 0.2, 0.5, 1.0 and 2.0 A g−1, respectively. As the current density returns to 0.1 A g−1, its specific discharge capacity can reach 527.5 mAh g−1. The excellent cycling and rate performances of NiFe2O4/Fe0.64Ni0.36@CNFs are mainly attributed to the following reasons: i) the carbon fibers can effectively alleviate volume expansion and structural stress during cycling; ii) Fe0.64Ni0.36 alloy can inhibit the formation of lithium dendrites and effectively reduce the nucleation overpotential of metallic lithium, thereby improving the electrochemical stability; iii) the heterostructure can improve electrochemical properties through the synergistic interaction between NiFe2O4 and Fe0.64Ni0.36. The catalytic Fe0.64Ni0.36 not only facilitate the conversion reaction of NiFe2O4, resulting in the high capacity, but also increase the conductivity of the material. This work offers a feasible strategy to significantly improve the electrochemical performance of binary metal compounds, paving the way for their practical applications in the high-performance LIBs.