桦木基Si@C复合材料的制备及其电化学性能

以桦木屑为碳源,KOH为活化剂,采用碳化-活化工艺制备多孔炭。用浸渍法将纳米硅颗粒分散在桦木基多孔炭上,得到桦木基Si@C复合材料。采用扫描电子显微镜(SEM)、透射电子显微镜(TEM)、能谱分析(EDS)、X射线衍射(XRD)、N_(2)吸附等手段表征多孔炭和Si@C复合材料的微观形貌、元素组成、晶型和孔结构等。以桦木基Si@C复合材料作为锂电池负极材料,采用扣式法制备纽扣电池并研究Si@C复合材料的电化学性能。结果表明:桦木基多孔炭和桦木基Si@C复合材料均很好保持了原桦木基的骨架结构特点;纳米硅颗粒均匀负载在多孔炭的表面和孔洞中;桦木基Si@C复合材料在0.5 A/g时的初次放电比容量为1 099.98 mA·h/g, 200次循环后稳定在1 089.77 mA·h/g,容量保持率为99.07%,展现出优异的循环稳定性能。

不同粒径纳米硅制备Si@C/石墨负极材料及其电化学性能

采用喷雾干燥热解法制备了Si@C/石墨复合材料,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)对合成材料的结构、形貌进行表征,将材料作为正极制备模拟电池,对电池进行恒流充放电和循环伏安(CV)测试。结果表明:具有不同纳米尺度的原料硅直接影响复合材料的性能。所研究的三种硅颗粒的粒径越小,电池的循环稳定性越好。以平均粒径为80nm的硅合成的复合材料Si@C/石墨制备而成的电池具有较好的综合电化学性能,以100mA/g电流密度充放电时,首次放电比容量可以达到774.3mAh/g,100次循环后容量保持率为78.1%。

Silicon/flake graphite/carbon anode materials prepared with different dispersants by spray-drying method for lithium ion batteries

Silicon/flake graphite/carbon （Si/FG/C） composites were synthesized with different dispersants via spray drying and subsequent pyrolysis, and effects of dispersants on the characteristics of the composites were investigated. The structure and properties of the composites were determined by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurements. The results show that samples have silicon/flake graphite/amorphous carbon composite structure, good spherical appearances, and better electrochemical performance than pure nano-Si and FG/C composites. Compared with the Si/FG/C composite using washing powder as dispersant, the Si/FG/C composite using sodium dodecyl benzene sulfonate （SDBS） as dispersant has better electrochemical performance with a reversible capacity of 602.68 mA·h/g, and a capacity retention ratio of 91.58 % after 20 cycles.