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

Abstract

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 easy-control 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 (∼207 m2 g−1) and hierarchical porosity with a broad pore-size distribution from 2 to 100 nm. Moreover, finite element analysis suggests that nanowire-constructed open meso-/macro-pores benefit the Li+-transport/storage kinetics. As a consequence, the NW-TOHMS 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.