Highly aligned and low tortuosity nanoarray engineering for fast Li-S batteries

Developing efficient sulfur cathodes toward low conductivity of S8 and severe polysulfide shuttling is of great significance for lithium-sulfur batteries. Herein, a highly aligned and low tortuosity nanoarray engineering composed of N-doped carbon nanotube arrays uniformly coated with a thin layer of TiO2 (noted as aligned TiO2@CNT@CC) was facilely synthesized. As revealed by density functional theory calculations and COMSOL simulations, the vertically aligned CNTs provide fast electronic transport paths and the TiO2 layer catalyzes fast redox reaction kinetics of polysulfides. As further confirmed by electrochemical tests, the low tortuosity TiO2@CNT@CC shows better performance than both bare CNT@CC and disordered TiO2@CNT@CC electrodes. Typically, a specific energy density of 1298 mAh g−1 at 0.1C is obtained, which retains 715 mAh g−1 at a high rate of 3C. Remarkably, the aligned TiO2@CNT@CC cathode shows a high specific discharge capacity of 779 mAh g−1 with sulfur loading of 3 mg cm−2 after 100 cycles at a E/S ratio of 10 μL mg−1. Our approach would provide a promising route for the facile structural & surface engineering of ordered array electrodes with high electrochemical performance.