Constructing stronger interaction with polysulfides for faster conversion of Li2S2 to Li2S by Co-CoSe2@N, Se-doped carbon nanocages in lithium-sulfur batteries

Abstract

The transformation of Li2S2-Li2S is indubitably the most crucial and labored rate-limiting step among the sophisticated reactions for the lithium-sulfur batteries (LSBs), the adjustment of which is anticipated to impede the shuttle effect. Herein, a N, Se dual-doped carbon nanocages embedded by Co-CoSe2 nanoparticles (Co-CoSe2@NSeC) is employed as a functional coating layer on commercial separator to improve the performance of LSBs. The well-designed N, Se co-doped nanostructures endow the modified layer with a satisfactory capacity for blocking polysulfides. Both calculations and experiments jointly disclose that the Li2S2 to Li2S reaction, including the liquid-solid conversion, was prominently expedited both thermodynamically and electrodynamically. Consequently, the batteries fabricated with Co-CoSe2@NSeC modified separator can deliver a favorable 764.2 mAh g−1 with 8.0 C, accompanied by a salient long cycling lifespan (only 0.066 % at 1 C and 0.061 % under 2 C after 1000 and 2000 cycles), and a desired anode protection. In addition, despite a raised areal loading of 7.53 mg cm−2 was introduced, the cells assembled by Co-CoSe2@NSeC@PP are allowed to produce an outstanding initial behavior of 8.71 mAh cm−2 under 0.2 C. This work may reinforce further explorations and serve with valuable insights into N, Se dual-doping materials for high-performance LSBs.