Encapsulating CoRu alloy nanocrystals into nitrogen-doped carbon nanotubes to synergistically modify lithium-sulfur batteries separator

Abstract

Lithium-sulfur batteries (LSBs) have attracted considerable attention owing to their large energy density and abundant reserves of sulfur element. However, the sluggish kinetics and shuttle effects.seriously inhibit the further application of LSBs. Extensive studies have conclusively demonstrated that separator modification was an effective strategy to enhance LSBs properties through the chemical adsorption and catalytic kinetic conversion of lithium polysulfides (LiPSs). In this study, cobalt and ruthenium nanoalloys confined into nitrogen-doped carbon nanotubes (CoRu@N-CNTs) were prepared by one-step annealing method using melamine as carbon source. The obtained CoRu@N-CNTs exhibit plenty of advantages, including abundant CoRu bimetallic catalytical and nitrogen adsorption active sites, exceptional electrolyte wettability and high conductivity. Thanks to these merits, the CoRu@N-CNTs can provide ultrafast ion transfer channels, lots of anchoring for LiPSs and the catalytic conversion kinetics of LiPSs. When applied to modify Li–S batteries separator, the CoRu@N-CNTs modified separator presented an excellent initial specific capacity of 1134.22 mAh g−1 at 0.5C, good rate performance (686 mAh g−1 at 3C) and outstanding cycle performance with a capacity attenuate rate of only 0.107 % per cycle for 400 cycles. Furthermore, when the current density increased to 1C (S loading of 1.344 mg), it displayed a superior capacity attenuation rate of 0.09 %. When the S loading increased to 2.304/3.072 mg, it also demonstrated an outstanding cycle performance. This work provides a feasible strategy to modify the Li–S battery separator through synergistic integration of catalytic conversion and chemisorption of polysulfides.