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.