Sulfonic acid functionalized Al-based MIL-101-NH2 modified separator for lithium-sulfur batteries

The transmembrane diffusion of soluble lithium polysulfides (LiPS) is the main cause of capacity loss and negative electrode corrosion in lithium-sulfur (Li-S) batteries. In order to suppress the shuttle effect of LiPS, a selective permeability membrane was constructed by introducing functional materials with negative charge groups. Herein, a functional separator with high ion conductivity is obtained by casting the environmentally friendly MOF material sulfonic acid functionalized amino-MIL-101 (S-MIL-101) onto the separator. It is found that the functionalized sulfonic acid group not only accelerates the conduction of the lithium-ion but also repels the polysulfide anion through electrostatic interactions. With this functionalized separator, the initial capacity of batteries is 1444.6 mAh center dot g- 1 at 0.2C and remains 990.4 mAh center dot g- 1 after 100 cycles. Meanwhile, the batteries still deliver a high initial discharge capacity of 895.7 mAh center dot g- 1 even with the high-sulfur-loading cathode (4.7 mg cm-2) at 0.2C.

Automated summary

This study focuses on using a functional separator to suppress the shuttle effect of soluble lithium polysulfides in Li-S batteries. It is found that the functionalized sulfonic acid group not only accelerates the conduction of lithium ions, but also repels polysulfide anions through electrostatic interactions. The performance of the batteries is significantly improved with the use of this functionalized separator.