Manipulation of surface microstructures of porous carbon derived from waste tea leaves for lithium sulfur batteries

• Published in: Surface & coatings technology 2020-10, Vol.400, p.126228, Article 126228
• Main Authors: Wang, Chih-Chieh, Lin, Yu-Wei, Lee, Shang-Min
• Format: Article
• Language: English
• Subjects: Activated carbon; Activating agent; Charge transfer; Lithium ion battery; Lithium sulfur; Lithium sulfur batteries; Microstructure; Pore size distribution; Porosity; Porous carbon; Sulfur content; Tea; Zinc chloride
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2020.126228

Surface microstructures of porous carbon (PC) derived from waste tea leaves were manipulated by using ZnCl2, KOH and H3PO4 as activating agents. The PCs with various surface microstructures were used as hosts for sulfur, and their electrochemical performances were investigated systematically. The KOH activated carbon exhibited not only a maximum specific surface area, 2287.3 m2g−1 but also a broadened pore size distribution, 2.60 to 3.87 nm, as well as a large pore volume, 1.273 cm3g−1, leading to a high sulfur content, 71 wt%. Interestingly, the KOH activated carbon‑sulfur composite (CS) exhibited superior electrochemical performances. The initial discharge capacity under 0.1C, 1350 mA h g−1 was obtained. After 100 cycles under 0.2C, the capacity of 750 mA h g−1 was maintained. When the current density increased to a 1C the capacity of 728 mA h g−1 was reached, but only capacities of 360 mA h g−1 and 264 mAhg−1 were reached, respectively, for the ZnCl2-and H3PO4-CS samples. The improved electrochemical performances were due to the lowest resistance of charge transfer from the SEI layer (Rs) and the interfacial electrons (Rct). Both reduced resistances were attributed to the microstructural features that suppress the polysulfide dissolution. •Surface microstructures of porous carbon (PC) derived from waste tea leaves can be manipulated by a facile method.•The KOH activated carbon enables to load high amounts of sulfur due to the microstructures.•The KOH activated carbon-sulfur composite (CS) exhibits superior electrochemical performances.