CoF2 nanodots embedded N-doped carbon polyhedrons as a multifunctional interlayer for dendrite-free and stable lithium-sulfur batteries

Abstract

The shuttle effect of lithium polysulfides (LiPSs) and the uncontrolled growth of lithium dendrites remain formidable barriers to the large-scale commercialization of lithium-sulfur (Li–S) batteries. In order to simultaneously address both issues, herein, for the first time, we present MOF-derived CoF₂ nanodots embedded nitrogen-doped carbon polyhedrons (CoF₂@NCP) as a multifunctional separator interlayer. The conductive NCP and in-situ grown CNTs provide efficient electron transfer network. Most importantly, the homogeneously distributed polar and lithiophilic CoF₂ nanodots can not only strongly chemisorb and effectively catalytically convert LiPSs to suppress shuttle effect, but also uniformly regulate the Li-ion flux to realize smooth stripping/plating, thus inhibiting dendrite growth. Benefiting from the merits, the Li||Li symmetric cells with CoF₂@NCP sustain stable cycling for 1000 h at 1 mA cm⁻² and remain stable at 4 mA cm⁻²; the Li–S full cells with CoF₂@NCP deliver an outstanding initial capacity of 1514.8 mA h g⁻¹ at 0.2 C, retain 935.2 mA h g⁻¹ after 150 cycles, and exhibit a high capacity of 753.9 mA h g⁻¹ at a high rate of 4 C. In-situ Raman spectroscopy and Li₂S₆ adsorption tests confirm effective LiPSs immobilization and accelerated redox kinetics. This work offers a rational strategy for designing multifunctional interlayers for dendrite-free and stable Li–S batteries.