Bimetallic MOF-derived CNTs-grafted carbon nanocages as sulfur host for high-performance lithium–sulfur batteries

Carbon materials , especially those with hollow structure, have gained considerable attention as the host materials for sulfur in Li–S batteries . Herein, the nanocages consisting of carbon nanotubes (CNTs) and hierarchically porous carbon (CNT-NC@GC) are synthesized using bimetallic core-shell metal-organic frameworks as precursor. CNTs are in situ introduced onto the inner/outer surface of the nanocages to form a three-dimensional conductive network throughout the entire electrode for the favorable electrolyte penetration and improved electrons/ions transfer. Abundant N-doping and Co nanoparticles decoration in the tips of CNTs or on the surface of GC shells are beneficial to immobilize soluble polysulfides . Moreover, the modified Co nanoparticles possess chemisorption and electrocatalytic activity for sulfur conversion, which can promote redox kinetics of the polysulfides and improve the cycling stability. As a result, the as-prepared CNTs-grafted nitrogen-doped carbon@graphitic carbon nanocages cathode containing 79.2 wt% of sulfur (CNT-NC@GC/S) delivers a high discharge capacity of 743 mA h g −1 after 500 cycles at a current density of 1.0C with a capacity retention of 83.6%. And the cathode with high areal sulfur loading of 4.95 mg cm −2 shows a high areal capacity of 4.01 mA h cm −2 over 100 cycles.