Self-Templating Synthesis of Hollow Co₃O₄ Nanoparticles Embedded in N,S-Dual-Doped Reduced Graphene Oxide for Lithium Ion Batteries

The design and synthesis of hollow-nanostructured transition metal oxide-based anodes is of great importance for long-term operation of lithium ion batteries. Herein, we report a two-step calcination strategy to fabricate hollow Co 3 O 4 nanoparticles embedded in a N,S-co-doped reduced graphene oxide framework. In the first step, core–shell-like Co@Co 3 O 4 embedded in N,S-co-doped reduced graphene oxide is synthesized by pyrolysis of a Co-based metal organic framework/graphene oxide precursor in an inert atmosphere at 800 °C. The designed hollow Co 3 O 4 nanoparticles with an average particle size of 25 nm and wall thickness of about 4–5 nm are formed by a further calcination process in air at 250 °C via the nanoscale Kirkendall effect. Both micropores and mesopores are generated in the HoCo 3 O 4 /NS-RGO framework. Benefiting from the hierarchical porous structure of the hollow Co 3 O 4 and the co-doping of nitrogen and sulfur atoms in reduced graphene oxide, the thus-assembled battery exhibits a high specific capacity of 1590 mAh g –1 after 600 charge–discharge cycles at 1 A g –1 and a promising rate performance from 0.2 to 10 A g –1 .