锂离子电池硅碳复合负极材料的研究

锂离子电池硅碳复合负极材料的研究 参考文献 摘 要 锂离子电池作为储能系统中重要组成部分被广泛关注，目前锂离子电池负极材料中常用的是碳类负极材料，但是由于碳类负极材料比容量比较低，很难适应人们对高性能储能材料的要求，所以急需开发一种新的负极材料。硅是很好的选择，硅材料凭借着其高比容量、低电压平台和丰富的储量等优点备受关注。但是由于硅颗粒作为锂离子电池负极材料在充放电过程中，存在着体积效应，容易导致电极导电网络的破坏，并且硅作为半导体导电能力不高，所以硅材料目前尚不能投入商业化生产与应用。为了克服硅材料出现的缺点，我们研制了硅碳复合材料，研究了最佳的硅碳复合比例，并以此为基础分别用碳纳米管及石墨烯对其进行了掺杂改性，研究取得如下主要结果： （1）硅/石墨复合材料。采用简单机械球磨的办法将微米硅与石墨均匀复合，并研究了不同掺硅比对复合材料电化学性能的影响。研究发现当硅掺杂量达到20%时得到硅/石墨复合材料最好的电化学性能，循环15次以后充电比容量仍达到567 mAh g-1，容量保持率为58.6%，这主要得益于硅与石墨的协同作用。 （2）硅/石墨/石墨烯复合材料。采用机械方法先将硅与石墨烯进行复合，得到硅/石墨烯复合材料，再与石墨进行简单的复合，最终得到硅/石墨/石墨烯复合材料，并研究了不同石墨烯掺杂量对复合材料电化学性能的影响。发现在3%和5%石墨烯掺入量的条件下，复合材料循环10次后，仍能保持499.9 mAh g-1和520.9 mAh g-1充电比容量，容量保持率分别为98.2%和92.3%，石墨烯的二维层状结构能有效的抑制硅颗粒的膨胀破碎并且形成良好的导电网络，提高电化学性能。 (3)硅/石墨/碳纳米管复合材料的。采用机械方法先将硅与碳纳米管进行复合，得到硅/碳纳米管复合材料，再与石墨进行简单的复合，最终得到硅/石墨/碳纳米管复合材料，并研究了不同碳纳米管掺杂量对复合材料电化学性能的影响。发现在7%和9%MWCNTs掺入量的条件下，复合材料循环10次后，仍能保持455.4mAh g-1和462.4mAh g-1充电比容量，容量保持率分别为81.4%和82.1%，MWCNTs的晶须结构能有效的增加复合材料的导电性能形成良好的导电网络，提高电化学性能。 关键词：硅；石墨；石墨烯；碳纳米管；锂离子电池 45 ABSTRACT Lithium-ion battery is the essential part of the energy storage system, which is in the widely attention. Carbon anode materials is commonly used in lithium-ion battery at present, but it is difficult to adapt to the requirements of high performance energy storage materials, due to its lower specific capacity. It is necessary to research new anode materials. Silicon will be a good choice, which has high specific capacity, low voltage platform and abundant reserves. It is very difficult to put silicon into commercial production and application, because silicon particles has volume effect in the process of charging and discharging, which is easy to cause destruction of electrode conductive network. In order to overcome these defects,we research silicon –based anode materials. Best proportion of S/C was studied. On this basis.We used carbon nanotubes and graphene as the doping modification The research contents could be seen as follow: (1)Silicon/graphite composite material preparation. Micro silicon and graphite homogeneous mixed have been prepared by simple mechanical ball grinding method. the influence of different doped silicon ratio on electrochemical performance of composite materials have been studied. The results show that when the silicon doping amount is achieved 20%, the silicon/graphite composite has the best electrochemical performance with the charge capacity of 567mAh g-1 and capacity retention rate was 58.6% after 10 times circulation ，which is due to the synergy of silicon and graphite. (2)Silicon/graphite/grapheme composite material preparation. First , micro silicon and graphene homogeneous mixed have been prepared by simple mechanical ball grinding method. Then preparing composite compound with graphite ,finally get silicon/graphite/graphene composite. We study the influence of different doped graphene ratio on electrochemical performance of composite materials. Research show that the composite exhibited a high charge capacity of 499.9 mAh g-1 and 520.9 mAh g-1 , and capacity retention rate was 98.2% and 92.3 after 10 times circulation, when the graphene doping amount achieve 3% and 5% . The two-dimensional layered structure can effectively restrain the expansion of the silicon particle breakage and form good conductive network, eventually improve the electrochemical performance. (3)Silicon/graphite/carbon nanotube composite material preparation. First , micro silicon and carbon nanotube homogeneous mixed have been prepared by simple mechanical ball grinding method .Then make composite compound with graphite and finally get silicon/graphite/carbon nanotube. We study the influence of different doped carbon nanotube ratio on electrochemical performance of composite materials. Research show that the composite exhibited a high charge capacity of 455.4mAh g-1 and 462.4mAh g-1 , and capacity retention rate was 81.4% and 82.1% after 10 times circulation, when the carbon nanotube doping amount achieve 7% and 9%. MWCNTs whisker structure can effectively increase the conductivity of the composite and form good conductive network, then improve the electrochemical performance. Key words: silicon; graphite; graphene; carbon nanotube; lithium-ion battery 目 录 第1章 绪论 1 1.1 引言 1 1.2 锂离子电池工作机理和特点 2 1.2.1 锂离子电池工作机理 2 1.2.2 锂离子电池工作特点 2 1.3 锂离子电池关键材料 3 1.3.1 正极材料 4 1.3.2负极材料 5 1.3.3 电解液 6 1.4 硅基负极材料 7 1.4.1 硅负极材料的研究意义 7 1.4.2 硅负极材料的储锂机理 7 1.4.3 硅负极材料应用存在的瓶颈 8 1.4.4 硅负极材料性能改善方法 9 1.5 硅基复合负极材料研究现状 10 1.5.1 硅-碳复合材料 10 1.5.2 硅-金属复合材料 12 1.6 本课题研究的意义及主要内容 12 1.6.1 本课题研究的意义 12 1.6.2 本课题研究的内容 13 第2章 硅/石墨复合材料的研究 14 2.1 引言 14 2.2 实验材料及方法 15 2.2.1 实验药品与仪器 15 2.2.2 材料的物相表征 16 2.2.3 电化学性能测试 16 2.3 硅/石墨复合材料的制备与表征 17 2.3.1 硅材料的预处理 17 2.3.2 硅/石墨复合材料的制备 18 2.3.3 不同比例硅/石墨复合材料的表征 18 2.4 本章小结 24 第3章 硅/石墨/石墨烯复合材料的研究 25 3.1 引言 25 3.2 硅/石墨/石墨烯复合材料的制备与表征 26 3.2.1 硅/石墨/石墨烯复合材料的制备 26 3.2.2 硅/石墨/石墨烯复合材料的物相表征 27 3.2.3 硅/石墨/石墨烯复合材料的电化学表征 29 3.3 本章小结 32 第4章 硅/石墨/多壁碳纳米管复合材料的研究 33 4