Hierarchical Nanoflower-like CoS ₂ Microspheres with Enhanced Sodium-Ion Storage and Printable Electrode Architectures

Hierarchical nanoflower-like CoS 2 micronanostructures (CoS 2 @CoS 2 -NS) were prepared using a simple solvothermal technique and a controllable after-synthesis solution. The hierarchical structure consisting of spherical CoS 2 cores bound with the connected ultrathin nanosheets, is a porous nanoflower-like structure with abundant electrochemically active sites, shorter Na + diffusion routes, and higher volume variation during cycling. Due to the rational structural design, CoS 2 @CoS 2 -NS anodes demonstrate excellent sodium-ion storage performance, including high reversible capacity, superior rate capability, and robust cycling stability. The hierarchical CoS 2 @CoS 2 -NS microspheres were also printed into printable inks, allowing accurate electrodes to be printed via direct ink writing (DIW) 3D printing. The double-layer 3D-printed electrodes offer excellent mass load and ion/electron-transport trade-offs (735 mAh g –1 at 1000 mA g –1 ) and excellent cycle life (728 mAh g –1 after 100 cycles at 2 A g –1 ) compared with blade-coated electrodes. We show that the combination of rational hierarchical structural design and DIW fabrication can be a promising option in high-performance sodium-ion battery anodes.