Flexible electrode of Fe-doped NiSe2@porous graphene as binder-free anode for lithium-ion batteries

Abstract

Fe-doped NiSe₂@porous graphene (Fe-NiSe₂@PG) was prepared via the doping of iron in NiSe₂@porous graphene (NiSe₂@PG) by a vacuum filtration, annealing, and selenylation process. Different from the granular structure of NiSe₂@PG, Fe-NiSe₂@PG had a rod-like structure. The morphology, structure, and interfacial interaction of NiSe₂@PG and Fe-NiSe₂@PG were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy. After iron doping, the first reversible capacity of Fe-NiSe₂@PG increased to 951.7 mA h g⁻¹ from 472.6 mA h g⁻¹ (NiSe₂@PG) at 100 mA g⁻¹. After 50 cycles, the reversible capacity of Fe-NiSe₂@PG increased to 1221.8 mA h g⁻¹. Even at 1, 2, and 5 A g⁻¹, the specific capacities were still 659.7, 396.3, and 260.8 mA h g⁻¹ after 500 cycles, respectively. On the one hand, the Fe doping could increase the intrinsic conductivity of NiSe₂. On the other hand, the graphene helped to form a complete conductive network and improve the conductivity of Fe-NiSe₂@PG. Moreover, the porous structure was conducive to the wetting of electrolyte on the electrode material. In addition, the strong interfacial interaction between graphene and NiSe₂ can facilitate the transfer of lithium ions and electrons. Thus, when used as anode material for a lithium-ion battery, Fe-NiSe₂@PG exhibited excellent electrochemical performance.