Excellent electrochemical performance of Lithium-sulfur batteries via self-standing cathode from interwoven α-Fe2O3 integrated carbon nanofiber networks

Abstract

Lithium‑sulfur batteries (LSBs) are one of the highly attractive next-generation electrochemical energy-storage systems owing to their high energy density at a low cost. However, the performance degradation of sulfur cathodes over repeated cycling remains a critical challenge to be addressed. Herein, the influence of a current collector-free and binder-free flexible self-standing cathode featured by three dimensional nanofibrous matrix composed of α-Fe 2 O 3 integrated carbon nanofiber (Fe-CNF) toward improving the electrochemical performance of LSB with the aid of an effective electrolyte penetration, Li + migration and accommodating the volume variation is investigated. The physical barrier effect by the interwoven nanofibrous architecture and the intense chemisorption by the combined effect of polar α-Fe 2 O 3 and nitrogen-doped carbon restrict the dissolution and diffusion of soluble lithium polysulfides. In addition, the α-Fe 2 O 3 ensures the acceleration of polysulfide conversion reactions. Benefiting from this architecture, the cathode retains 92.5%, of its initial capacity, after 150 cycles at 0.2C-rate. Even after 650 cycles at a high rate of 1C, a significant capacity retention of 43.1% is attained, with an average capacity fade rate of 0.087% per cycle. The self-standing LSB cathode, namely, Fe-CNF/S electrode fabricated via electrospinning technique, not only can provide physical and chemical barrier to restrict the shuttling of soluble lithium polysulfide (LiPS), but also can efficiently catalyze their conversion to insoluble products and vice-versa, leading in an improved active material utilization and electrochemical performance. • α-Fe 2 O 3 integrated carbon nanofiber self-standing mat prepared via electrospinning. • Metal current collector-free and slurry-free electrode design. • The interwoven nanofibers improve electrolyte penetration and sulfur utilization. • α-Fe 2 O 3 have strong chemisorption and catalytic effect toward polysulfides. • Superior electrochemical performance is achieved by the self-standing electrodes.