Hollow Urchin-like\nNi–Co MOF and RGO Synergistically\nFunctionalizing the Separators for High-Performance Li–S Batteries

Parasitic shuttle effects and sluggish polysulfide reaction\nkinetics\nseverely attenuate the properties of lithium–sulfur (Li–S)\nbatteries, especially the capacity retention and cycling performance.\nIn this work, a hollow urchin-like Ni–Co MOF was first developed,\nand its coupling with reduced graphene oxide (RGO) modified the commercial\nPP separators. The electrochemical properties of the Li–S battery\nhave been improved a lot. The initial capacity can reach 1385 mAh\ng<sup>–1</sup> at 0.1 C, the capacity can maintain 680 mAh\ng<sup>–1</sup> after 300 cycles at 1 C (89.3% Coulombic efficiency),\nand the capacity decay rate is only 0.036% per cycle. Then, the comparison\nbetween PP and modified separators revealed possible enhancement mechanisms.\nFirst, the modified separators display better electrolyte wettability\nand higher porosity, both of which are beneficial for improving mass\ntransfer efficiency. Second, the hollow urchin-like Ni–Co MOF\ncan provide abundant adsorption and catalytic sites for polysulfides,\ninhibiting the shuttle effect. Third, RGO nanosheets not only prevent\nthe aggregation of the Ni–Co MOF but also supplement excellent\nelectron conduction. In addition, the CV and LSV curves ascertain\nthe superior chemical reaction kinetics of the modified separators.\nThus, the hollow urchin-like Ni–Co MOF and RGO synergistically\nfunctionalizing the commercial PP separators can obtain a high-performance\nLi–S battery.