Hybrid Anatase/Rutile Nanodots-Embedded Covalent Organic Frameworks with Complementary Polysulfide Adsorption for High-Performance Lithium–Sulfur Batteries

Abstract

The shuttling effect of polysulfides species seriously deteriorates the performance of Li-S batteries, representing the major obstacle for their practical use. However, the exploration of ideal cathodes that can suppress the shuttling of all polysulfides species is challenging. Herein, we propose an ingenious and effective strategy for constructing hybrid-crystal-phase TiO₂/covalent organic framework (HCPT@COF) composites where hybrid anatase/rutile TiO₂ nanodots (10 nm) are uniformly embedded in the interlayers of porous COFs. The synthesis was realized via a multiple-step reaction relay accompanying by a pseudo-topotactic transformation of three-dimensional layered structures from 1,4-dicyanobenzene monomer-embedded Ti-intermediate networks to HCPT nanodots-embedded COF frameworks. The HCPT@COF/S cathodes show superior comprehensive performance such as high specific capacity, long cycling stability, and remarkable rate capability for Li-S batteries, owing to the complementary anchoring effect of hybrid anatase/rutile TiO₂ in the HCPT@COF composite, which is evidenced by substantial characterizations including X-ray photoelectron spectroscopy and density functional theory calculations.