Hollow Co3O4 Microspheres Grafted with Nitrogen-Doped Carbon Nanotubes as Efficient Sulfur Host for High Performing Lithium–Sulfur Batteries

Abstract

Though the Li–S battery is considered as an attractive next-generation battery technology, a few challenges still need to be solved, for example, poor conductivity of the electrode, sluggish reaction kinetics, polysulfide shuttling, and cycle life. Here, we design an effective polysulfide immobilizer by grafting nitrogen-doped carbon nanotubes (NCNTs) on hollow Co3O4 microspheres and use it to prepare a freestanding sulfur composite cathode. This architecture imparts benefits such as superior electronic conductivity, better buffering of volume changes during electrochemical cycling, high polar surface for polysulfide absorption, and outstanding electrocatalytic activity to ameliorate the lithium polysulfide conversion kinetics. As a result, the composite sulfur electrode shows an initial capacity of 1104 mAh g–1 (at 0.5C rate) and capacity retention of 73% after 300 cycles. Similarly, at a 1C rate, the electrode shows stable cycling behavior over 800 cycles with a capacity retention of 65%. The Li–S cell also exhibits high power capability, as at a 5C rate, it delivers a capacity of 385 mAh g–1. The synergistic effect between the polysulfide adsorbing additives Co3O4 and NCNT plays a major role in the high utilization of sulfur even when sulfur loading increases to 12 mg cm–2.