A facile electrochemical strategy for engineering sulfur deficiencies of CdS nanosheets to promote the catalytic conversion of polysulfides for lithium–sulfur batteries

Rechargeable lithium–sulfur batteries (LSBs) are regarded as one of the most promising next-generation energy storage systems for their high energy density and low-cost. However, the severe shuttle effect and the sluggish kinetics of polysulfides significantly hinder the practical application of LSBs. Most notably, surface defects of catalysts (typically anion deficiencies) have been fabricated via metal doping, hydrogen treatment and plasma engraving, in order to effectively enhance the chemisorption and electrocatalysis of polysulfides. However, these methods are complicated, have high costs and suffer from difficulties in scaling up. Herein, we present a facile and cost-effective strategy via electroreduction treatment to fabricate sulfur deficiencies applied to a CdS nanosheet/reduced graphene oxide (CdS NSs/rGO) composite, which serves as the functional separator to promote the catalytic interconversion of polysulfides for LSBs. The cell with the CdS1−x NSs/rGO functional separator not only exhibits a high initial rate performance of 1415.9 mA h g−1 at 0.2C, but it also delivers an excellent cycling stability with a decay rate of 0.066% after 1000 cycles at 1C. This work provides a new perspective on engineering sulfur deficiencies in energy storage systems through electrochemical technology.