Interlayer Structure Design Based on Bipyridine Covalent Organic Framework Nanosheets and Its Application in Lithium-Sulfur Batteries
Lithium-sulfur batteries(LSBs)with elemental sulfur as cathode have received extensive attention in the field of energy storage due to their high theoretical specific capacity and energy density.However,the shuttle effect of soluble lithium polysulfides(LiPSs)during charge and discharge will lead to rapid capacity decay,which impedes the practical application of LSBs.In order to effectively inhibit the shuttle effect of LiPSs in LSBs,a bipyridine COF nanosheet(Tp-Bpy)was designed and used as a multifunctional interlayer for LSBs in this study.Benefiting from the strong adsorption and catalytic activity of the uniformly dispersed nitrogen sites in bipyridine linkers,as well as the nanosheet structure can provide more active sites.LiPSs can be well adsorbed and catalyzed by Tp-Bpy nanosheets,thus inhibiting its shuttle effect.Tp-Bpy nanosheet interlayer has faster transformation kinetics during LiPSs redox reaction,and reduces electrochemical polarization during liquid-solid transformation.Compared with the unmodified traditional polypropylene(PP)separator,the rate performance and cycle stability of the LSBs assembled with Tp-Bpy nanosheet interlayers have been significantly improved.Experiments have shown that the LSBs assembled with Tp-Bpy nanosheet interlayers exhibited an initial discharge capacity of 1 223 mAh·g-1 at 0.1 C.In addition,the specific capacity was maintained at 452 mAh·g-1 at 1 C after 500 cycles with a decay rate of 0.093%per cycle.Tp-Bpy nanosheets interlayers have emerged as a prominent research avenue in combating the shuttle effect of LiPSs in LSBs.This study contributes valuable theoretical underpinnings to the advancement of novel multifunctional interlayer.
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