The Mork Family Department of Chemical Engineering and Materials Science and ‡Ming Hsieh Department of Electrical Engineering, University of Southern California , Los Angeles, California 90089, United States.
Nano Lett. 2014 Feb 12;14(2):473-9. doi: 10.1021/nl403404v. Epub 2013 Dec 30.
A generic and facile method of coating graphene oxide (GO) on particles is reported, with sulfur/GO core-shell particles demonstrated as an example for lithium-sulfur (Li-S) battery application with superior performance. Particles of different diameters (ranging from 100 nm to 10 μm), geometries, and compositions (sulfur, silicon, and carbon) are successfully wrapped up by GO, by engineering the ionic strength in solutions. Importantly, our method does not involve any chemical reaction between GO and the wrapped particles, and therefore, it can be extended to vast kinds of functional particles. The applications of sulfur/GO core-shell particles as Li-S battery cathode materials are further investigated, and the results show that sulfur/GO exhibit significant improvements over bare sulfur particles without coating. Galvanic charge-discharge test using GO/sulfur particles shows a specific capacity of 800 mAh/g is retained after 1000 cycles at 1 A/g current rate if only the mass of sulfur is taken into calculation, and 400 mAh/g if the total mass of sulfur/GO is considered. Most importantly, the capacity decay over 1000 cycles is less than 0.02% per cycle. The coating method developed in this study is facile, robust, and versatile and is expected to have wide range of applications in improving the properties of particle materials.
本研究报道了一种通用且简便的在颗粒表面包覆氧化石墨烯（GO）的方法，以硫/GO 核壳颗粒为例，在锂硫（Li-S）电池应用中展示出了优异的性能。通过调控溶液中的离子强度，成功地将不同粒径（100nm-10μm）、形貌和组成（硫、硅和碳）的颗粒包覆上 GO。重要的是，我们的方法不涉及 GO 与被包覆颗粒之间的任何化学反应，因此，它可以扩展到大量的功能性颗粒。进一步研究了硫/GO 核壳颗粒作为 Li-S 电池正极材料的应用，结果表明，硫/GO 相较于未包覆的纯硫颗粒具有显著的提升。使用 GO/硫颗粒进行的恒流充放电测试表明，如果仅考虑硫的质量，在 1A/g 的电流密度下循环 1000 次后，其比容量仍保持在 800mAh/g，如果考虑硫/GO 的总质量，则比容量为 400mAh/g。更为重要的是，在 1000 次循环中，容量衰减率小于 0.02%/循环。本研究中开发的包覆方法简便、稳健且具有通用性，有望在改善颗粒材料性能方面具有广泛的应用前景。
