MOFs derived ZnSe/N-doped carbon nanosheets as multifunctional interlayers for ultralong-Life lithium-sulfur batteries

Abstract

• Zinc-based MOFs derived ZnSe/NC nanosheets were synthesized through a feasible process for improving the performance of Li-S batteries. • ZnSe/NC nanosheets have good conductivity and multiple adsorptive/catalytic sites. • The Li-S cells with the modified separator show an outstanding lifespan over 1500 cycles at 1 C with a low capacity decay of 0.046% per cycle. The shuttle effect and slow conversion rate of lithium polysulfides (LiPSs) have become the main obstructs to the development of lithium-sulfur (Li-S) batteries. Herein, the low cost metal-organic frameworks derived nitrogen-doped carbon nanosheets embedded with zinc selenide nanoparticles (ZnSe/NC nanosheets) were designed and synthesized for Li-S batteries. As the LiPSs trapping-layer, these nanocomposites provide some key benefits: (1) The nitrogen doping changes local electron distribution in the carbon nanosheets, thus the electrical conductivity is greatly improved for facilitating the transport of electrons/ions. (2) Nitrogen atoms and ZnSe nanoparticles play an important role in anchoring the LiPSs via chemical interactions. (3) The remarkable catalytic activity of ZnSe nanoparticles can accelerate the redox kinetics of LiPSs. As a result, the Li-S battery with the ZnSe/NC nanosheets modified separator exhibits ultralong lifespan over 1500 cycles with a small capacity loss of only 0.046% per cycle at 1 C, which is superior over those reported values. Furthermore, the Li-S battery with a high sulfur loading of 4.71 mg cm −2 can still maintain a high areal capacity of 4.28 mAh cm −2 after 50 cycles. This work provides a new route to the design of multifunctional low cost and high-performance separators for remarkably stable Li-S batteries.