Construction of composite separator with 3D hierarchical spinel structure in Lithium-Sulfur batteries

Lithium-sulfur (Li-S) batteries are considered the most promising candidate for achieving a low-cost high-energy–density system. One of the biggest deterrents during the practical application of Li-S batteries is the shuttle effect which causes fast capacity degradation and poor rate performance. 3D CoNi2S4 with 3D interconnected porous nitrogen doping carbon was prepared by sulfurizing the precursor Prussian blue analogues. The CoNi2S4 nanoparticles are confined in the carbon framework, affording interconnected macro-mesoporous channels. The constructed 3D CoNi2S4 modified separator effectively accommodates enough electrolytes and provides more exposed active sites that suppress the shuttle effect through trapping polysulfides and accelerating the lithiation of S8 to Li2S. Thus, Li-S batteries with 3D CoNi2S4-PP separators exhibit high-rate capacity and remarkable cycle stability. Furthermore, based on the modified separators, a high sulfur loading cathode delivers an areal capacity of 5.62 mAh cm−2. The separator size expands further to assemble the 1Ah Li-S pouch cell, confirming the practicality. This work provides an efficient strategy with a modified separator for high-performance Li-S batteries.