Interpenetrated Networks between Graphitic Carbon Infilling and Ultrafine TiO₂ Nanocrystals with Patterned...

Interpenetrated networks between graphitic carbon infilling and ultrafine TiO₂ nanocrystals with patterned macropores (100-200 nm) were successfully synthesized. Polypyrrole layer was conformably coated on the primary TiO₂ nanoparticles (∼8 nm) by a photosensitive reaction and was then transformed into carbon infilling in the interparticle mesopores of the TiO₂ nanoparticles. Compared to the carbon/graphene supported TiO₂ nanoparticles or carbon coated TiO₂ nanostructures, the carbon infilling would provide a conductive medium and buffer layer for volume expansion of the encapsulated TiO₂ nanoparticles, thus enhancing conductivity and cycle stability of the C-TiO₂ anode materials for lithium ion batteries (LIBs). In addition, the macropores with diameters of 100-200 nm in the C-TiO₂ anode and the mesopores in carbon infilling could improve electrolyte transportation in the electrodes and shorten the lithium ion diffusion length. The C-TiO₂ electrode can provide a large capacity of 192.8 mA h g^-1 after 100 cycles at 200 mA g^-1, which is higher than those of the pure macroporous TiO₂ electrode (144.8 mA h g^-1), C-TiO₂ composite electrode without macroporous structure (128 mA h g^-1), and most of the TiO₂ based electrodes in the literature. Importantly, the C-TiO₂ electrode exhibits a high rate performance and still delivers a high capacity of ∼140 mA h g^-1 after 1000 cycles at 1000 mA g^-1 (∼5.88 C), suggesting good lithium storage properties of the macroporous C-TiO₂ composites with high capacity, cycle stability, and rate capability. This work would be instructive for designing hierarchical porous TiO₂ based anodes for high-performance LIBs.