Functionalization of Nitrogen-Doped Carbon Nanofibers with Polyamidoamine Dendrimer as a Freestanding Electrode with High Sulfur Loading for Lithium-Polysulfides Batteries

Lithium sulfur (Li-S) batteries have been considered as promising energy storage devices because of their superiority in energy density. However, the sulfur loading, low active material utilization, and poor cycling stability limit their commercial applications. Herein, we prepared a three-dimensional structure of polyamidoamine dendrimer (PAMAM)-functionalized nitrogen-doped carbon nanofibers (PAMAM@N-CNFs) by combined electrospun and solution coating techniques. The fabrication of freestanding PAMAM@N-CNF membranes was carried out using a Li2S6 catholyte for lithium-polysulfides batteries. The PAMAM@N-CNFs shows the strong physicochemical adsorption of polysulfides and effectively reduced the electrochemical polarization. The Li2S6 catholyte-impregnated PAMAM@N-CNF electrode (sulfur loading: 4.74 mg) shows a high first discharge capacity of 998 mA h g(-1) at 0.2 C and stabilizes at 783 mA h g(-1) after 300 cycles, exhibiting a superior cycling performance than the N-CNFs/Li2S6 electrode. In addition, an excellent initial capacity of 5.77 mA h (capacity retention of 71.2% over 400 cycles at 0.2 C) is achieved under a high sulfur loading of 7.11 mg. The N-CNFs modified by PAMAM with functional groups is promising for assembling with a high sulfur loading electrode, which exhibits a superior electrochemical performance in Li-S batteries.