以金属锡粉(Sn)、金属钴粉(Co)和乙炔黑为主要原料,综合利用固相烧结和高能球磨的方法制备出Sn-Co-C复合负极材料,采用XRD、SEM、EDS和恒电流充放电等技术对材料进行了表征和电性能测试.实验结果表明:高能球磨处理后,Sn-Co-C复合材料颗粒尺寸减小,首次放电容量显著提升,为476.8 m Ah/g;经过30次循环后可逆容量仍保持在394.4 m Ah/g.
主要是用乙酸钴和四氯化锡分散在石墨烯乙醇溶液中,先进行液相聚合,然后在高温下还原,得到锡-钴-碳-石墨烯复合材料。在锡钴比例一定,当石墨烯含量为0.55 g时,制备的复合材料具有较好的电化学性能,透射电镜(TEM)、扫描电镜(SEM)图像表明金属合金均匀分布,颗粒大小在10 nm左右,且首次充电比容量为837.2 m Ah/g,经过80次循环之后比容量还能保持在796.6 m Ah/g,容量的保持率能达到90%以上。
以纳米二氧化锡、硝酸钴、脲、葡萄糖和十二烷基硫酸钠为原料,通过水热-碳热还原原位制备锂离子电池Sn-Co-C复合负极材料。通过XRD、SEM、EDS和TEM分析表明,原位生成的Sn-Co合金颗粒分布于纳米或微米尺度的碳球和碳纳米棒内部以及微孔碳基体之中。电化学测试表明,在50 m A·g-1电流密度下,Sn-Co-C复合负极材料首次充放电比容量分别为602.9 m Ah·g-1和867.1 m Ah·g-1,循环100次后其充放电比容量仍分别保持在350.4 m Ah·g-1和356.6 m Ah·g-1,平均每次放电容量衰减率仅为5.1%。优异的电化学性能主要归因于Sn-Co合金颗粒处于纳米或微米尺度的碳球和碳纳米棒内部以及微孔碳基体之中可以改善其导电性,并可以缓解锂电池充放电过程中产生的体积变化所导致的活性物质脱落,提高循环性能和寿命。
分别以葡萄糖和乙炔黑为碳源,采用固相烧结法制备Sn-Co/C锂离子电池负极复合材料,探讨碳源种类对材料结构和电化学性能的影响规律。结果表明:摩尔比为1:1的Sn-Co合金由Co Sn相和微量Co Sn2相组成;在Sn-Co/C复合材料中,大部分葡萄糖热解炭和乙炔黑存在于Sn-Co合金颗粒表面,少部分进入颗粒内部,会在一定程度上阻碍Sn-Co合金的相变反应,残留微量Co Sn2和Co3Sn2相,同时阻碍Sn-Co合金晶粒或颗粒的长大,起到细化晶粒或颗粒的作用。添加葡萄糖热解炭和乙炔黑有利于提高Sn-Co/C复合材料的电子导电和Li+扩散,从而提高其电化学活性;并且添加葡萄糖的Sn-Co/C复合材料电化学性能更好,在电流密度为0.05 m A/cm2条件下的首次可逆放电容量为325 m A·h/g,经过100次循环后的容量保持率达到70.8%,循环性能比Sn-Co合金的提高26.8%,显示出良好的结构稳定性。
As an anode material in lithium ion battery,the Sn-Co/Ccomposite electrode materials have been successfully synthesized by hydrothermal and sol-gel methods,respectively.The resultant composites were mainly composed of Sn-based oxides,nanometer Sn-Co alloy and carbon.Carbon and Co,acting as buffer materials,can accommodate to the large volume change of active Sn during the discharge-charge process,thus improving the cycling stability.Although charge/discharge curves revealed the excellent cycle performance for samples synthesized by both methods,composites obtained by the sol-gel showed a better dispersion effect of nanoparticles on the carbon matrix and possessed much more improved stable capacity with*624.9 mAh g-1over 100 cycles and that by hydrothermal method only exhibited*299.3 mAh g-1.Therefore,the Sn-Co/Ccomposites obtained by sol-gel synthesis method could be a perfect candidate for anode material of Li-ion storage battery.
Xiaoli ZouXianhua HouZhibo ChengYanling HuangMin YueShejun Hu
Alloy anodes were studied for pursuing Sn-based microcomposite synthesis, assembly and performance for lithium ion batteries. The self-assembled Sn-Co-Ccomposites with nano-scaled microstructures were prepared via solution method and carbothermal technology. The morphology and physical structure were investigated with scanning electron microscope (SEM) and X-ray diffraction (XRD). The as-prepared materials were assembled to half cell coin for the purpose of discussing the galvanostaticcycling, cyclic voltammetry and rate-capability performance. Results reveal that nanoscaled CoSn 2 alloys covered with Sn and C layer by layer are wrapped by cross-linked porous carbon network to form spherical microstructure. This distinguishing feature of Sn-Co-Ccomposites provides a possible solution to the problems of Sn particle aggregation and poor electron transport, and has strong effect on improving electrochemical performance.
