Self-templated formation of hierarchically porous TiO2 hollow microspheres with fast lithium-uptake performance

Hollow TiO2 microspheres composed of low-dimensional anisotropic building blocks (such as nanowires or nanosheets) possess a hierarchical porosity and thus favor mass/Li+ transfer. However, developing an easycontrol method to synthesize this type of TiO2 is still a challenge. Herein, an aerosol-assisted self-assembly method is developed to construct the nanowire-assembled TiO2 hollow microspheres (NW-TOHMS). The nanowire-intertangle configuration results in forming large surface area (similar to 207 m(2) g(-1)) and hierarchical porosity with a broad pore-size distribution from 2 to 100 nm. Moreover, finite element analysis suggests that nanowireconstructed open meso-/macro-pores benefit the Li+-transport/storage kinetics. As a consequence, the NWTOHMS electrode exhibits a high specific capacity of 117 mA h g(-1) at 5 A g(-1) after 1000 cycles. Excitingly, the activated carbon/NW-TOHMS Li-ion capacitors demonstrate an energy density as high as 37 Wh kg(-1) at the maximum power density of 6.1 kW kg(-1). This work offers a new pathway for the synthesis of mesoporous TiO2 hollow superstructures used to fast energy storage and conversion.