Rational Design Of Perforated Bimetallic (Ni, Mo) Sulfides/N-Doped Graphitic Carbon Composite Microspheres As Anode Materials For Superior Na-Ion Batteries

Highly conductive 3D ordered mesoporous Ni7S6-MoS2/N-doped graphitic carbon (NGC) composite (P-NiMoS/C) microspheres are prepared as anode materials for Na-ion batteries. The rationally designed nanostructure comprises stable Ni7S6- and MoS2-phases along with the homogeneously distributed ordered mesopores (phi = 50 nm) over the external and internal structures generated through thermal decomposition of polystyrene nanobeads (phi = 100 nm). Therefore, the P-NiMoS/C microspheres deliver initial discharge capacities of 662, 419, 373, 300, 231, 181, and 146 mA h g(-1) at current densities of 0.5, 1, 2, 4, 6, 8, and 10 A g(-1), respectively. Furthermore, P-NiMoS/C exhibits a stable discharge capacity of 444 mA h g(-1) at the end of the 150th cycle at a current density of 0.5 A g(-1), indicating higher cycling stability than the filled, that is, non-mesoporous, Ni3S2-MoS2/NGC (F-NiMoS/C) microspheres and filled carbon-free Ni3S2-MoS2 (F-NiMoS) microspheres. The superior electrochemical performance of P-NiMoS/C microspheres is attributed to the rapid Na+ ion diffusion, alleviation of severe volume stress during prolonged cycling, and higher electrical conductivity of NGC, which results in fast charge transfer during the redox processes. The results in the present study can provide fundamental knowledge for the development of multicomponent, porous, and highly conductive anodes for various applications.