γ-Fe2O3 nanoparticles anchored in MWCNT hybrids as efficient sulfur hosts for high-performance lithium-sulfur battery cathode

Lithium-sulfur (Li-S) battery is one of the most promising electrochemical energy storage devices due to its high energy density and reduced cost. The main challenges of Li-S battery are the severe dissolution of lithium polysulfides and low electrical conductivity of S. In this work, the synthesis of gamma-Fe2O3 nanoparticles anchored in MWCNT (MCF) is presented through a facile method with refluxing and heating, and studied as effective S hosts in Li-S batteries. In an electrochemical analysis, the S@MCF-1 electrode shows a high rate capability (over 340 mA h g(-1) at 7 C-rate) and stable long-term cycling performance even after 500 cycles (over 545 mA h g(-1), at 1 C-rate). These improved electrochemical performances could be corresponded to the two roles of gamma-Fe2O3 nanoparticles as (1) the nodes in MWCNTs for mitigating the aggregation and volume expansion of S, and (2) the active sites and strong chemical adsorption ability on the surface of MWCNTs to directly trap polysulfides during the cycling.