Accelerated oxidation-reduction kinetic functional polyurea Binders: Diselenide building block as redox co-moderators

The performance of Li-S batteries based on multiphase and multi-electron transfer mechanisms is highly dependent on the redox kinetics of sulfur. However, the slow redox kinetics of the endogenous redox mediator lithium polysulfides hinders the preparation of high-performance Li-S batteries. In this work, two functional polyurea binders (PUSe and PUS) were synthesized, which possess diselenide or disulfide modules. PUSe and PUS binders can not only limit the shuttling effect of polysulfides by abundant urea groups effectively, but also give the sulfur cathode excellent mechanical properties by introducing intermolecular hydrogen-bonding networks and diselenide and disulfide modules. More significantly, selenium-selenium and sulfur-sulfur modules have been considered as redox co-mediators to accelerate the redox process of sulfur cathode. Li-S batteries involved with PUSe and PUS as binders show excellent electrochemical performance, while significantly accelerating the redox kinetic process, the initial discharge specific capacity of the cell with PUSe as binder was as high as 963.1 mAh/g and 856.7 mAh/g after 500 cycles at 1C; the capacity decay rate is only 0.022% per cycle.