Ultralight carbon flakes modified separator as an effective polysulfide barrier for lithium-sulfur batteries

• Published in: Electrochimica acta 2019-02, Vol.295, p.910-917
• Main Authors: Zheng, Bangbei, Yu, Liwei, Zhao, Yang, Xi, Jingyu
• Format: Article
• Language: English
• Subjects: Carbon; Carbon flakes; Carbonization; Commercialization; Decay rate; Discharge; Electrochemical analysis; Energy storage; Flakes; Flux density; Functional separator; Lithium; Lithium sulfur batteries; Polysulfide barrier; Polysulfides; Self-discharge; Separators; Sodium citrate; Storage batteries; Sulfur
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2018.11.145

Lithium-sulfur (Li-S) batteries are widely recognized as the most promising next generation energy storage system owing to the incredibly high theoretical energy density and specific capacity. Nevertheless, the practical application of Li-S batteries is hindered by the inevitable “shuttle effect” of the soluble lithium polysulfide, which leads to fast capacity degradation, low coulombic efficiency and severe self-discharge. To address these issues, we propose an ultralight carbon flakes modified separator (CFs@PP) that improves the conductivity and works as an effective polysulfide barrier for high-performance Li-S batteries. The CFs are easily obtained by the direct carbonization of sodium citrate, making it possible for large scale manufacture. With the CFs@PP separator employed, the Li-S battery delivers an initial discharge capacity of 1063 mAh g−1 and retains 683 mAh g−1 after 500 cycles at 0.5C with a low capacity decay rate of 0.071% per cycle. Moreover, great rate performance and small self-discharge are also acquired with the CFs@PP separator applied. The facile preparation of the CFs and the superior electrochemical performance of the CFs@PP separator may promote the commercialization of Li-S batteries. [Display omitted] •Carbon flakes (CFs) are simply synthesized by the direct carbonization of sodium citrate.•The mass loading of the ultralight CFs coating on the PP separator is only 0.16 mg cm−2.•Conductivity and wettability of the separator are greatly enhanced due to the CFs coating.•CFs coating layer acts as an upper current collector and a polysulfide barrier simultaneously.•Li-S battery with the CFs@PP separator retains 683 mAh g−1 after 500 cycles at 0.5 C.