Heteroatom surface engineering with distinct doping ways and valence state regulation: Boosting electrocatalysis performance of Ni-doped MoS2/rGO host for excellent lithium sulfur batteries

Abstract

Sulfur host materials are crucial to the electrochemical performances of lithium sulfur batteries (LSBs). Two-dimensional (2D) nanomaterials with close atomic thickness and large specific surface area are considered as excellent sulfur hosts in lithium sulfur batteries due to their extraordinary physical properties and special structures, which play a key role in improving the redox reaction kinetics of sulfur/Li2S. The heteroatom doping, which is usually applied in surface engineering, can not only adjust surface coordination environment but also form surface functional groups. Herein, the surface structures and properties of 2D Ni-doped MoS2/rGO composite are regulated via two surface engineering strategies. One is that nickel atoms are doped into 2D MoS2 nanosheets by two distinct hydrothermal techniques, which would result in notable differences of surface heteroatom content, and another is that the valence state of surface heteroatom nickel is changed by the thermal reduction technology. The content and valence state of surface heteroatom nickel can significantly influence the electrocatalysis activities of host materials during the redox reaction processes of sulfur/Li2S, which would substantially alter the electrochemical performances of LSBs. When the S@3%Ni-MoS2/rGO-IIRe is used as sulfur host, the lithium‑sulfur cell has an initial discharge capacity of 936.4 mA h g−1 and a low capacity attenuation of only 0.027 % each cycle with the high capacity of 819.7 mA h g−1 after 450 cycles at 1C, exhibiting an excellent coulombic efficiency and outstanding cycle stability. This study would provide some inspiration for improving the electrochemical performance of advanced lithium‑sulfur batteries through the rational regulation of surface atomic structures and electronic states of sulfur hosts.