Cationic-Polymer-Functionalized Separator As a High-Efficiency Polysulfide Shuttle Barrier for Long-Life Li–S Battery

Because of the advantages of high theoretical capacity, low cost, and environmental friendliness, lithium–sulfur (Li–S) batteries have attracted wide attention as promising energy storage system for electric vehicles and smart power grids. However, their commercialization is still greatly restricted by their poor cycle stability, resulting from the severe shuttling of soluble lithium polysulfides (LiPSs) during cycling. Herein, we designed a CNT@cationic polymer/rGO (CNT@CP/rGO) blocking layer on a commercial PP separator. Such a blocking layer can strongly fix LiPSs by the electrostatic attraction effect between the cationic polymer backbones and the polysulfide anions. As a result, a Li–S battery equipped with a CNTs@CP/rGO-functionalized separator showed much improved cycling stability with a capacity fading rate as low as 0.06% per cycle during 700 cycles at 1 C. Especially, high areal capacity of 6.3 mAh cm–2 was also achieved with a high sulfur loading of 8.5 mg cm–2 after 50 cycles. This work highly emphasizes that the electrostatic attraction mechanism between cationic polymers and polysulfides can effectively restrain the polysulfide shuttling and thus significantly improve the electrochemical performance of Li–S batteries.