Selective sulfur conversion with surface engineering of electrocatalysts in a lithium–sulfur battery

Abstract

The sluggish kinetics of multiphase sulfur conversion with homogeneous and heterogeneous electrochemical processes, causing the “shuttle effect” of soluble polysulfide species (PSs), is the challenges in terms of lithium–sulfur batteries (LSBs). In this paper, a Mn3O4−x catalyst, which has much higher activity for heterogeneous reactions than for homogeneous reactions (namely, preferential-activity catalysts), is designed by surface engineering with rational oxygen vacancies. Due to the rational design of the electronic structure, the Mn3O4−x catalyst prefers to accelerate the conversion of Li2S4 into Li2S2/Li2S and optimize Li2S deposition, reducing the accumulation of PSs and thus suppressing the “shuttle effect.” Both density functional theory calculations and in situ X-ray diffraction measurements are used to probe the catalytic mechanism and identify the reaction intermediates of MnS and LiyMnzO4−x for fundamental understanding. The cell with Mn3O4−x delivers an ultralow attenuation rate of 0.028% per cycle over 2000 cycles at 2.5 C. Even with sulfur loadings of 4.93 and 7.10 mg cm−2 in a lean electrolyte (8.4 µL mg s−1), the cell still shows an initial areal capacity of 7.3 mAh cm−2. This study may provide a new way to develop preferential-activity heterogeneous-reaction catalysts to suppress the “shuttle effect” of the soluble PSs generated during the redox process of LSBs.