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A binary metal organic framework derived hierarchical hollow Ni₃S₂/Co₉S₈/N-doped carbon composite with superior sodium storage performance

Liu, Xinye, Zou, Feng, Liu, Kewei, Qiang, Zhe, Taubert, Clinton J., Ustriyana, Putu, Vogt, Bryan D., Zhu, Yu
Journal of materials chemistry A 2017 v.5 no.23 pp. 11781-11787
anodes, batteries, carbon, carbonization, coatings, cobalt, composite materials, coordination polymers, electrochemistry, nickel, sodium, sulfides
A binary Ni/Co metal organic framework (Ni–Co-MOF) with a hollow-sphere structure that is decorated with cone-shaped protrusions was prepared via a facile solvothermal reaction. Carbonization and sulfurization of the Ni–Co-MOF produced a Ni₃S₂/Co₉S₈/N-doped carbon composite that retained the hierarchical structure. The final composite material presents exceptional electrochemical performance when used as an anode in sodium-ion batteries. A reversible specific capacity of 419.9 mA h g⁻¹ at a current density of 0.1 A g⁻¹ was achieved after 100 cycles, with an exceptional capacity retention of 98.6%. Furthermore, superior rate capability was also demonstrated: an average capacity of 323.2 mA h g⁻¹ at a current density of 2 A g⁻¹ can be achieved. This exceptional performance can be attributed to the unique nano-architecture derived from the MOF precursor, as the resultant material possesses an ideal profile for an excellent anode material: ultrafine Ni₃S₂ and Co₉S₈ particles (∼7 nm), a hollow, porous structure, and an ultrathin N-doped carbon coating.