【作者】 张倩；

【导师】 孙世刚； 李君涛；

【作者基本信息】 厦门大学 ， 能源化学， 2014， 硕士

【摘要】 硅材料因具有高质量比容量、较低的电压平台、价格低廉、原料来源丰富等优点成为最有潜力的锂离子电池负极材料之一。但硅负极材料在充放电的过程中发生严重的体积变化。并且硅材料的导电性差,导致其循环性能和倍率性能差。针对上述问题,本论文尝试通过采用不同形貌的三维硅薄膜材料和使用新型硅基负极料料粘结剂这两条途径来提高硅基材料的电化学性能。首先采用磁控溅射的方法在泡沫镍的表面制备了三维网状结构的硅薄膜材料。当厚度为200nm时,在4.2A/g的电流密度下充放电300周后,容量高达1472mAh/g。基于上述三维结构薄膜能提高硅材料电化学性能的实验,我们制备不同三维结构的基底,通过磁控溅射制得一批性能优异的硅薄膜材料：(1)通过化学腐蚀和电化学还原的方法,在铜片的表面制备树叶状三维多孔结构,再沉积厚度分别为0.2、0.4、0.6和1μm的硅薄膜。厚度为0.2μm的硅薄膜材料具有优异的循环性能和倍率性能,在0.8A/g的电流密度下充放电200周后容量为1461mAh/g;当硅薄膜的厚度增加至1μm(硅薄膜中间夹入两层厚度为10nm的金属Al薄膜),前120周保持着优异的循环性能,且极片保持了良好的完整性。(2)采用化学腐蚀和电化学还原的法,在泡沫铜的表面制备针状三维多孔结构,再沉积得到厚度为0.6和1μm的硅薄膜材料。当厚度为0.6μm时,以0.8A/g的电流密度充放电500周后,容量保持在1132mAh/g,循环性能优异；当厚度为1μm时,以2.1A/g的电流密度充放电100周后,容量为1208mAh/g。本文还研究了一种新型硅基材料粘结剂-瓜尔豆胶。使用瓜尔豆胶作为粘结剂时,硅基材料的性能明显优于使用CMC、海藻酸钠等作为粘结剂时的性能。当电流密度为3.43A/g时,以瓜尔豆胶作为粘结剂的Si/C负极材料充放电100周后容量为1283mAh/g,而以海藻酸钠作为粘结剂的Si/C负极材料充放电100周后,容量为991mAh/go综上所述,本论文研究表明三维结构是提高硅负极材料电化学性能的一种有效方法。同时还首次提出采用瓜尔豆胶作为锂离子电池硅基材料的粘结剂,研究表明该粘结剂能大幅提高硅基材料的电化学性能。更多还原

【Abstract】 Si is one of the most potential anode materials, due to the high theoretical specific capacity, low voltage platform, low cost and abundant in nature. However, severe volume change during Li insertion and extraction processes and poor electrical conductivity of Si anodes lead to poor cycle performance and rate performance. In the thesis, different3D structured collectors and a novel binder are applied to improve the electrochemical performance of Si based anode.First, the3D net structure Si film anode is prepared by magnetron sputtering method on a foam Ni collector. When the thickness of the Si film is200nm, the3D net structure Si film anode can cycle300cycles with a capacity of1472mAh/g at4.2A/g. We also prepared different3D porous structured collectors and high-performance Si films by magnetron sputtering method:(1) The3D leaf-like porous structure is prepared on panel Cu by chemical etching and electrochemical reduction method, following magnetron sputtering method to obtain Si films with thickness of0.2,0.4,0.6and1μm, respectively. The Si film with thickness of0.2μm shows excellent cycle performance and rate performance with a capacity of1461mAh/g after200cycles at0.8A/g. Even when the thickness of Si film increases to1μm (two Al films with thickness of10nm are added in the middle of the Si film), the Si film also exhibits wonderful cycle performance in the first120cycles with integrated structure.(2) Another3D needle-like porous structure based Si film is prepared on foam Cu by the same methods with thickness of0.6and1μm, respectively. The electrochemical performance of the3D needle-like porous structure based Si film with the thickness of0.6μm is excellent with a capacity of1132mAh/g after500cycles at0.8A/g. The Si film anode could also cycle100cycles with a capacity of1208mAh/g even when the thickness of the Si film increases to1μm.A new binder (guar gum) for Si-based anodes is also studied in the thesis. The electrochemical performances of Si-based electrode with guar gum binder are much better than that of CMC binder and Na alginate binder. When the guar gum is applied as a binder, the Si/C anode could cycle100cycles with a capacity as high as1283mAh/g, witch is much higher than that of Na alginate binder (991mAh/g).In brief, forming a3D structure is an effective way to improve the electrochemical performance of Si-based anode. And the guar gum is applied as a binder for Si-based anode for the first time to improve the electrochemical performances.更多还原