Interpenetrated Networks between Graphitic Carbon Infilling and Ultrafine TiO₂ Nanocrystals with Patterned Macroporous Structure for High-Performance Lithium Ion Batteries

Interpenetrated networks between graphitic carbon infilling and ultrafine TiO 2 nanocrystals with patterned macropores (100–200 nm) were successfully synthesized. Polypyrrole layer was conformably coated on the primary TiO 2 nanoparticles (∼8 nm) by a photosensitive reaction and was then transformed into carbon infilling in the interparticle mesopores of the TiO 2 nanoparticles. Compared to the carbon/graphene supported TiO 2 nanoparticles or carbon coated TiO 2 nanostructures, the carbon infilling would provide a conductive medium and buffer layer for volume expansion of the encapsulated TiO 2 nanoparticles, thus enhancing conductivity and cycle stability of the C–TiO 2 anode materials for lithium ion batteries (LIBs). In addition, the macropores with diameters of 100–200 nm in the C–TiO 2 anode and the mesopores in carbon infilling could improve electrolyte transportation in the electrodes and shorten the lithium ion diffusion length. The C–TiO 2 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 TiO 2 electrode (144.8 mA h g –1 ), C–TiO 2 composite electrode without macroporous structure (128 mA h g –1 ), and most of the TiO 2 based electrodes in the literature. Importantly, the C–TiO 2 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–TiO 2 composites with high capacity, cycle stability, and rate capability. This work would be instructive for designing hierarchical porous TiO 2 based anodes for high-performance LIBs.