Preparation of yolk–shell urchin-like porous Co3O4/NiO@C microspheres with excellent lithium storage performance†

Yolk–shell urchin-like porous Co₃O₄/NiO@C microspheres were successfully synthesized via a facile solvothermal method and annealing treatment under an argon atmosphere. High reversible specific capacity, long cycling stability, and excellent rate capability were achieved for the material due to its specific yolk–shell urchin-like porous structure and coated carbon layers. The pores distributed on the yolk and shell, as well as the gap between the yolk and shell, provide numerous pathways for the penetration of electrolyte, and enhance the reversible specific capacity (the initial discharge specific capacity was as high as 1405.7 mA h g⁻¹ at 0.1 C). Meanwhile, the stress and volume expansion could be greatly released and relieved through the pores, and long cycling stability was achieved (a high reversible specific capacity of 502.7 mA h g⁻¹ was maintained after 1000 cycles at 5 C). The coated carbon layers greatly enhance the conductivity of the yolk–shell urchin-like porous Co₃O₄/NiO microspheres, accelerate the transmission of electrons, and improve their rate performance (a reversible specific capacity of 397.5 mA h g⁻¹ was achieved when the current density was increased to 10 C).

Keywords: Yolk–shell; Urchin-like; Co₃O₄/NiO@C microspheres; Anode; Lithium storage.