Boosting Polysulfide Catalytic Conversion and Facilitating Li⁺ Transportation by Ion-Selective COFs Composite...

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.