锂硫电池膨胀氧化石墨/硫复合正极材料的制备及其性能

以棒状石墨为原料,采用改良的Hummers法与热处理制备得到膨胀氧化石墨(E-GO),利用在酸性水溶液中归中化学反应的方法合成纳米尺寸的硫颗粒,使其嵌入到膨胀氧化石墨的内部,制备了膨胀氧化石墨-硫复合材料。采用红外光谱,X-射线光电子能谱表征了膨胀氧化石墨表面官能团的存在和种类;X-射线衍射分析结果表明生成的硫属于斜方晶结构;扫描电子显微镜和透射电镜分析证明了材料中硫的均匀分布。恒电流充放电结果表明该复合正极材料的首次放电容量为1 020 mAh.g-1,100周循环之后其容量还保持在650 mAh.g-1左右;材料的倍率性能和库伦效率优异,这可能得益于小尺寸的硫在材料中均匀分布,以及表面官能团对硫的固定化作用。

Synthesis and Electrochemical Performance of Novel Expanded Graphite Oxide/Sulfur Composite Cathodes for Lithium-Sulfur Batteries

The expanded graphite oxides were prepared by modified Hummers method. The expanded graphite oxide/sulfur (E-GO/S) composites have been successfully prepared by a new chemical reaction method based on comproportionation in the acidic aqueous solution. FT-IR, XPS were characterized the existence of functional groups on the surface of expanded graphite oxide. XRD results showed that the as-prepared sulfur belongs to orthorhombic system. SEM and TEM results indicated the uniform distribution of the sulfur in the composite. The electrochemical test showed that the expanded graphite oxide/sulfur (E-GO/S) composites can deliver the highest discharge capacity of 1 020 mAh·g^-1 at the first cycle, after 100 cycles of charge-discharge, the discharge capacity of the composites keep the capacity of ca. 650 mAh·g^-1, and have the excellent rate performance and coulombic efficiency that may be attributed to the homogeneous distribution of sulfur in the composites and the chemical approach to fix sulfur and the lithium polysulfides via the chemical bonds with the functional groups on the surface of expanded graphite oxide.