The continuous efficient conversion and directional deposition of lithium (poly)sulfides enabled by bimetallic site regulation

The shuttle effect caused by the dissolution and accumulation of soluble (poly)sulfides seriously affects the reaction process and cycle performance of the lithium sulfur (Li-S) battery. One of the most effective strategies is the separator modification. The adsorption and catalytic mechanism of separator modification layer will cause discontinuous polysulfide conversion and loss of active substances. Therefore, 2D-bimetallic centered Zn/Co-ZIF nanosheets prepared by a novel method are selected to settle this unsolved problem for the first time. By regulating the metal center sites, the ability of ZIF nanosheets to transform (poly)sulfides is greatly improved.Further, based on the difference in conductivity between the ZIF modification layer and the cathode, the continuous efficient conversion and directional deposition of lithium (poly)sulfides to the cathode are realized. The battery assembled with the functional separator can deliver an initial capacity of up to 1304 mAh g−1 at 0.5 C, and excellent rate performance of 788 mAh g−1 at 3 C. Even at the current density of 2 C, the capacity attenuation rate of 1000 cycles is only 0.025% per cycle. This work will greatly promote the preparation of MOF materials and their application in Li-S batteries, and will further provide a new idea for the modification layer and cathode design.