Morphology-Tuned Synthesis of NiCo₂O₄-Coated 3D Graphene Architectures Used as Binder-Free Electrodes for Lithium-Ion Batteries

Nanostructured NiCo₂O₄ is directly grown on the surface of three-dimensional graphene-coated nickel foam (3D-GNF) by a facile electrodeposition technique and subsequent annealing. The resulting NiCo₂O₄ possesses a distinct flower or sheet morphology, tuned by potential or current variation electrodeposition, which are used as binder-free lithium-ion battery anodes for the first time. Both samples exhibit high lithium storage capacity, profiting from the unique binder-free electrode structures. The flower-type NiCo₂O₄ demonstrates high reversible discharge capacity (1459 mAh g^-1 at 200 mA g^-1) and excellent cyclability with around 71 % retention of the reversible capacity after 60 cycles, which are superior to the sheet-type NiCo₂O₄. Such superb performance can be attributed to high volume utilization efficiency with unique morphological character, a well-preserved connection between the active materials and the current collector, a short lithium-ion diffusion path, and fast electrolyte transfer in the binder-free NiCo₂O₄-coated 3D graphene structure. The simple preparation process and easily controllable morphology make the binder-free NiCo₂O₄/3D-GNF hybrid a potential material for commercial applications. Flower power: 3D nanostructured flower-type and sheet-type NiCo₂O₄/3D graphene-coated nickel foam composites were synthesized by a facile and tunable electrodeposition method. Both composites have mesoporous structure and exhibit high specific surface area, which favor not only higher Li storage capacity, but also excellent cycling performance as a binder-free electrode for lithium-ion batteries (see figure).