Hierarchical nanostructure of RuO₂ hollow spheres with enhanced lithium ion storage and cyclic performance

RuO₂ hollow spheres as a macroporous model structure for substituting a graphite anode in a lithium ion battery were successfully fabricated by utilizing the electrostatic attraction between exfoliated RuO₂ nanosheets and cationic polymers onto the polystyrene (PS) templates. According to the results of scanning electron microscopy, thin RuO₂ nanosheets were homogeneously covered onto the polystyrene beads before calcination. Transmission electron microscopy images clearly indicated complete removal of the PS templates after calcination at 500 °C for 2 h, leading to RuO₂ hollow spheres with a macroporous structure. Electrochemical charge/discharge experiments demonstrated a much larger lithium storage capacity for the RuO₂ hollow spheres described here (600 mAh/g) than that of bare rutile RuO₂ (340 mAh/g), highlighting the effectiveness of this synthetic technology.