Design and synthesis of multiroom-structured metal compounds–carbon hybrid microspheres as anode materials for rechargeable batteries

Highlights: • Multiroom-structured carbon hybrid microspheres of metal oxides are prepared by one-pot spray pyrolysis process. • Multiroom-structured CoSe₂-graphitic carbon hybrid microspheres are prepared by a simple post-treatment process. • Multiroom-structured microspheres have excellent electrochemical properties for Li-ion and Na-ion storage. A novel structure denoted as a "multiroom carbon hybrid", which comprises empty voids dispersed in metal oxide-, sulfide-, and selenide-carbon composites is introduced. Multiroom-structured carbon hybrid microspheres of single component Co₃O₄ and NiO and multicomponent (Ni_0.5Co_0.5)O_x were successfully prepared using a one-pot spray pyrolysis process. Liquid-liquid phase segregation during the spray pyrolysis process is a key requirement for generating multiroom-structured metal oxide-carbon hybrid microspheres. Multiroom-structured CoSe₂-graphitic carbon (GC) and CoS₂-CoS-GC hybrid microspheres were also prepared using a simple post-treatment process. Multiroom-structured CoSe₂-GC hybrid microspheres have superior sodium-ion storage properties to bare CoSe₂ microspheres. The reversible discharge capacities of the CoSe₂-GC and CoS₂-CoS-GC hybrid microspheres for the 100th cycles at a current density of 0.2 A g⁻¹ are 393 and 334 mA h g⁻¹, respectively. The discharge capacity of the multiroom-structured Co₃O₄-C hybrid microspheres for lithium-ion storage at a high current density of 3 A g⁻¹ for the 150th cycle is 1243 mA h g⁻¹.