Boosting Polysulfide Catalytic Conversion and Facilitating Li+ Transportation by Ion-Selective COFs Composite Nanowire for Li-S Batteries

The large-scale application of lithium-sulfur batteries (LSBs) has been impeded by the shuttle effect of lithium-polysulfides (LiPSs) and sluggish redox kinetics since which lead to irreversible capacity decay and low sulfur utilization. Herein, a hierarchical interlayer constructed by boroxine covalent organic frameworks (COFs) with high Li+ conductivity is fabricated via an in situ polymerization method on carbon nanotubes (CNTs) (C@COF). The as-prepared interlayer delivers a high Li+ ionic conductivity (1.85 mS cm(-1)) and Li+ transference number (0.78), which not only acts as a physical barrier, but also a bidirectional catalyst for LiPSs redox process owing to the abundant heterointerfaces between the inner conductive CNTs and the outer COFs. After coupling such a catalytic interlayer with sulfur cathode, the LSBs exhibit a low decay rate of 0.07% per cycle over 500 cycles at 1 C, and long cycle life at 3 C (over 1000 cycles). More importantly, a remarkable areal capacity of around 4.69 mAh cm(-2) can still be maintained after 50 cycles even under a high sulfur loading condition (6.8 mg cm(-2)). This work paves a new way for the design of the interlayer with bidirectional catalytic behavior in LSBs.

Automated summary

By constructing a multi-layer structure with boroxine covalent organic frameworks on carbon nanotubes to improve lithium ion conductivity and enrich the heterointerfaces between the inner conductive material and the outer material, this study addresses the challenges of capacity decay and low sulfur utilization in lithium-sulfur batteries.