In Situ Synthesis Method of Approaching High Surface Capacity Sulfur and the Role of Cobalt Sulfide as Lithium–Sulfur Battery Materials

Abstract

Lithium–sulfur batteries (Li–S) are potentially applicable in electrification and the replacement of fossil fuels due to the high energy density and the economy of sulfur. However, effectively an insulator, sulfur is known to suffer from inert electrochemical and poor conductivity. By synthetically incorporating conductive, low‐dimensional carbonaceous composites acting as both containment hosts and catalysts to active materials, this work entails an effective and straightforward materials engineering approach in fundamentally remodeling active materials utilization and activation. This synthetic‐based approach highlights direct processing capabilities than traditional thermal infusion processes without compromising performance and addresses the low activation, poor conductivity as well as alleviating side reactions due to polysulfide species. Motivated by recent efforts in excellent catalytic properties of cobalt sulfide (CoS)‐based materials, in this work, high‐performance CoS‐based carbonaceous composites are designed and employed, alleviating side reactions. These sulfide‐based catalysts are further elucidated in their role in facilitating charge/discharge of active materials, and assessed on practical polysulfide and side reaction alleviation with respect to various discharge/charge states. Proof‐of‐concept devices demonstrate the following performance highlights: 1) high‐performance stability, 2) strong polysulfide adsorption capability and kinetic characteristics, 3) large and workable areal capacity, and active materials loading.

Metal-ion exsolution effect to accelerate the reaction kinetics in Li–S batteries

“…5a and b, nickel and cobalt ions were initially discussed due to their higher activity. These ions underwent electrochemical reactions with S 2− generated during the reaction process through ion exsolution, resulting in the formation of corresponding metal-sulfides such as NiS, Ni 3 S 2 , Ni 7 S 6 , and CoS. 33,34 All of the transition metal sulfides exhibit high catalytic activity for LiPSs and rapid reaction kinetics, which can explain the superior performance of the NCM@3D-SP/S cathode. Furthermore, a lattice spacing related to Ni was also observed, which is attributed to the discharge of Ni 3 S 2 .…”