(A) study on Mg-MOF-74-derived MgO/carbon interlayer for long-life Li-S battery

Abstract

Lithium-sulfur battery, with abundant sulfur sources and high theoretical capacity, is one of promising future battery technology. LiS cathode has a theoretical capacity of 1672 $mAhg^{-1}$, which is an order of magnitude higher than the transition metal oxides of commercial lithium-ion batteries. However, the commercialization of Li-S battery is still struggling due to poor cyclic stability and limited kinetics. These problems come from the low electrical conductivity of sulfur and $Li_2S$, polysulfide shuttling effect and large volume change during cycling. Herein, we report two types of interlayers composed of magnesium oxide (MgO) and carbon substrate: MgO/PAN-derived carbon and Mg-MOF-74-derived MgO/carbon interlayer. The roles of MgO on carbon substrate in mitigating polysulfide shuttling are investigated. Dispersed MgO on carbon film acts as a good barrier to stop polysulfide migration and enhances cycling retention. Especially, with MOF-derived MgO/carbon interlayer, the high surface area can effectively suppress migration of polysulfides. Due to low electrical conductivity and polysulfide dissolution of the sulfur cathode, increasing loading mass of the cathode and electrolyte could be detrimental to Li-S cell performance. However, with MgO/carbon interlayer, this limitation could be overcome.