Electrochemical properties of multicomponent oxide and selenide microspheres containing Co and Mo components with several tens of vacant nanorooms synthesized by spray pyrolysis

Simple fabrication of CoMoO₄ and CoMoO₄-C microspheres containing several tens of vacant nanorooms by spray pyrolysis is described. The successful introduction of internal nanorooms was achieved by the phase segregation of dextrin applied in the spray solution as a deformable template. These uniquely structured microspheres enabled the facile penetration of liquid electrolyte and effectively alleviated stress resulting from the huge volume change that occurs during the cycling of Li-ion storage devices. The initial discharge capacity of the CoMoO₄ microspheres with vacant nanorooms was 1235 mA h g⁻¹ at a current density of 1 A g⁻¹, and its capacity retention after 100 cycles measured from the second cycle was 99%. The CoMoO₄ microspheres with vacant nanorooms showed superior cycling and rate performances compared to that of the CoMoO₄ microspheres with dense structures. The vacant nanorooms of the CoMoO₄-C microspheres were well maintained after selenization to form CoSe₂-MoSe₂/C composite microspheres. The CoSe₂-MoSe₂/C composite microspheres with vacant nanorooms showed superior Na-ion storage performances compared to that of the carbon-free CoSe₂-MoSe₂ microspheres with dense structures.