Department of Chemical Engineering, School of Environmental and Chemical Engineering, Shanghai University , Shangda Road 99, Shanghai 200444, P. R. China.
Nano Lett. 2016 Jan 13;16(1):440-7. doi: 10.1021/acs.nanolett.5b04105. Epub 2015 Dec 21.
Sulfur with a high specific capacity of 1673 mAh g(-1) is yet to be used as commercial cathode for lithium batteries because of its low utilization rate and poor cycle stability. In this work, a tube-in-tube carbon structure is demonstrated to relieve the critical problems with sulfur cathode: poor electrical conductivity, dissolution of lithium polysulfides, and large volume change during cycling. A number of small carbon nanotubes (∼20 nm in diameter) and a high loading amount of 85.2 wt % sulfur are both filled completely inside a large amorphous carbon nanotube (∼200 nm in diameter). Owing to the presence of these electrically conductive, highly flexible and structurally robust small CNTs and a large CNT overlayer, sulfur material exhibits a high utilization rate and delivers a large discharge capacity of 1633 mAh g(-1) (based on the mass of sulfur) at 0.1 C, approaching its theoretical capacity (1673 mAh g(-1)). The obtained S-CNTs@CNT electrode demonstrates superior high-rate cycling performances. Large discharge capacities of ∼1146, 1121, and 954 mAh g(-1) are observed after 150 cycles at large current rates of 1, 2, and 5 C, respectively.
硫具有高达 1673 mAh g(-1)的比容量，但由于其利用率低和循环稳定性差，尚未被用作锂离子电池的商业阴极。在这项工作中，展示了一种管中管碳结构，以缓解硫阴极的关键问题：导电性差、多硫化物锂的溶解以及循环过程中的体积变化大。大量的小碳纳米管（直径约 20nm）和 85.2wt%的高硫负载量完全填充在大的无定形碳纳米管（直径约 200nm）内部。由于存在这些导电、高弹性和结构坚固的小 CNT 和大的 CNT 覆盖层，硫材料表现出高利用率，并在 0.1C 时提供了高达 1633 mAh g(-1)（基于硫的质量）的大放电容量，接近其理论容量（1673 mAh g(-1)）。所获得的 S-CNTs@CNT 电极表现出优异的倍率循环性能。在 1、2 和 5C 的大电流速率下循环 150 次后，分别观察到约 1146、1121 和 954 mAh g(-1)的大放电容量。
