Polyvinylpyrrolidone-Coated KENAF-Derived Porous Carbon/Sulfur Composite for High-Performance Lithium-Sulfur Batteries

Abstract

As next-generation energy storage technologies, lithium-sulfur (Li-S) batteries have garnered a lot of attention because of their inexpensive cost, high theoretical capacity, low energy density, and lack of toxicity. Nonetheless, significant challenges about the dissolution of lithium polysulfides and the low conductivity of sulfur still need to be addressed. In this study, a low-cost kenaf stem precursor was pyrolyzed in a single step using a sodium hydroxide activating agent to create a micro/mesoporous carbon (KPC), which is porous carbon derived from the stem of a kenaf tree. This allowed for the efficient encapsulation of sulfur. Through a melt-diffusion technique, sulfur was loaded into the synthesized KPC pores (sulfur-laden KPC; S@KPC). The S@KPC composite has a higher loading of sulfur content (68%) inside the micro/mesoporous carbon. Additionally, with a multifunctional polyvinylpyrrolidone (PVP) coating (with different ratios), the resultant composite displays higher electrochemical performance, including a high specific capacity (1228 mAh/g at 0.3 C-rate (PVP-coated S@KPC 1-4)) and a good cycling life with a reversible capacity of 632 mAh/g after 100 cycles at 0.3 C-rate. Both the protective coating and the micro/mesoporous structure of the carbon inhibit polysulfide dissolution while simultaneously increasing interfacial stability and simplifying the charge transport pathways. This tactical combination leads to a high reversible capacity, better cycle reversibility, and good rate capabilities in Li-S batteries.