Hollow Urchin-like Ni–Co MOF and RGO Synergistically Functionalizing the Separators for High-Performance Li–S Batteries

Abstract

Parasitic shuttle effects and sluggish polysulfide reaction kinetics severely attenuate the properties of lithium–sulfur (Li–S) batteries, especially the capacity retention and cycling performance. In this work, a hollow urchin-like Ni–Co MOF was first developed, and its coupling with reduced graphene oxide (RGO) modified the commercial PP separators. The electrochemical properties of the Li–S battery have been improved a lot. The initial capacity can reach 1385 mAh g^–1 at 0.1 C, the capacity can maintain 680 mAh g^–1 after 300 cycles at 1 C (89.3% Coulombic efficiency), and the capacity decay rate is only 0.036% per cycle. Then, the comparison between PP and modified separators revealed possible enhancement mechanisms. First, the modified separators display better electrolyte wettability and higher porosity, both of which are beneficial for improving mass transfer efficiency. Second, the hollow urchin-like Ni–Co MOF can provide abundant adsorption and catalytic sites for polysulfides, inhibiting the shuttle effect. Third, RGO nanosheets not only prevent the aggregation of the Ni–Co MOF but also supplement excellent electron conduction. In addition, the CV and LSV curves ascertain the superior chemical reaction kinetics of the modified separators. Thus, the hollow urchin-like Ni–Co MOF and RGO synergistically functionalizing the commercial PP separators can obtain a high-performance Li–S battery.