Enhancing conversion of polysulfides via porous carbon nanofiber interlayer with dual-active sites for lithium-sulfur batteries.

Lithium-sulfur (Li-S) batteries are promising candidates for next-generation energy storage. However, the notorious lithium polysulfides (LiPSs) shuttle effect and torpid redox kinetics hinder their practical application. Enhancing phase conversion efficiency and limiting the dissolution of LiPSs are critical for stabilizing Li-S batteries. Herein, sulfiphilic defective TiO2 nanoparticles (D-TiO2) were integrated into the lithiophilic N-doped porous carbon nanofiber membrane (D-TiO2@NPCNF) to construct interlayer for catalyzing the conversion of LiPSs. The D-TiO2@NPCNF provides hierarchical porous structure and large specific surface area, and the formed 3D conductive network accelerates the transport of electrons and ions. The dual-active sites (N and D-TiO2) enhance the interface conversion and chemisorption ability of LiPSs via forming "Li-N and Ti-S" bonds. Due to the structural advantage of the D-TiO2@NPCNF, the Li-S batteries exhibit excellent cycling stability (only 0.049% decay per cycle in 800cycles at 1.0C) and impressive specific capacity (608 mAh g-1 at 3.0C). This work is expected to deepen the comprehension of complex interphase conversion processes of LiPSs and provide novel ideas for the design of new interlayer materials.

Preparation of cellulose acetate derived carbon nanofibers by ZnCl2 activation as a supercapacitor electrode.

Porous carbon nanofibers are fabricated by one-step carbonization and activation of electrospun cellulose acetate (CA) nanofibres. Electrospun CA nanofibers were obtained by the electrospinning of a CA/DMAC/acetone solution, followed by deacetylation in NaOH/ethanol solution. One-step carbonization and activation was achieved by dipping the as-spun fibers in ZnCl2 solution, followed by one-step high temperature treatment. The effects of the concentration of the dipping solution on the microstructure of the CA-based carbon nanofibers (CACNFs), including the morphology, crystal structure, porous structure, specific surface area and surface chemical properties, have been investigated. The coating of ZnCl2 effectively improves the thermal stability of electrospun CA nanofibers and obviously enhances the oxygen-containing surface groups of the CACNFs. The CACNFs have a norrow pore size distribution (0.6-1.2 nm) and a high specific surface area (∼1188 m2 g-1). Electrochemical performances of the CACNFs were evaluated as supercapacitor electrodes in 6 M KOH solution. The CACNFs demonstrate high specific capacitance (202 F g-1 at 0.1 A g-1) and excellent rate capability (61% of the retention from 0.1 to 20 A g-1). After 5000 cycles of the electrode, the capacitance is maintained at 92%, and the coulombic efficiency is close to 100%, showing high electrochemical stability and reversibility. The renewable features and excellent performance make CACNFs quite a promising alternative to efficient supercapacitor electrodes for energy storage applications.