锂离子电池论文：Si-SiO_x-Sn-C复合负极材料的合成及电化学性能研究

锂离子电池论文：Si-SiO_x-Sn/C复合负极材料的合成及电化学性能研究

【中文摘要】目前锂离子电池的应用越来越广泛。与其他类型的二次电池相比锂离子电池具有较多优点,比如,工作电压和能量密度高,循环寿命长,自放电率小,无记忆效应且电极材料不含有毒物质,

是现代的“绿色电池”。广泛的应用于移动电话,笔记本电脑,电动车和混合电动车中。锂电池负极材料主要采用已经商业化的碳类材料,但由于它的理论比容量较低,且由于碳材料的嵌锂电位与金属锂接近,在快速充电时存在安全隐患,所以开发高比容量和性能安全的负极材料成为必要。由于硅和锡的理论比容量高(分别为4200 mAh g-1,994 mAh g-1),成为研究热点。但由于它们在充放电过程中存在严重的体积膨胀收缩,导致容量衰减较快,循环性能较差,极大的影响了材料的实用价值。利用硅锡的复合物或其合金,可以有效地改善它们的循环性能。本论文研究了一氧化硅和二氧化锡均匀混合后在碳的作用下于高温管式炉中发生反应,合成新的具有充放电效应的电极材料。考察了温度的影响,电化学性能及交流阻抗。通过实验研究得到以下结论：1.将SiO、纳米Sn02和碳混合后湿磨,于氮气保护下在管式炉中加热到750℃,800℃,850℃,900℃,950℃和1000℃。经XRD分析得知,新合成的材料中温度在800℃及以上时,Sn02经碳

【英文摘要】Lithium-ion cells are considered presently the best choice for rechargeable batteries. Lithium-ion cells have

many advantageous compared with other secondary batteries. Lithium-ion battery has high voltage, high energy density, long cycle life, self-discharge rate is small, no memory effect and also the electrode material does not contain toxic substances, is the modern “green battery.” It is widely used in mobile phones, notebook computers, electric vehicles and hybrid electric vehicles. Since the first commercialization of Li-ion batteries by Sony in 1991, graphite carbon has been the favorable anode material for its good reversibility and stability with thousands of cycles. However since the theoretical capacity (372 mAh g-1) of graphite is limited, new anode materials with high specific capacity are searched to satisfy the requirement of advanced power sources in such applications as electric vehicles with extended range.The search for next-generation anode materials of Li-ion batteries has focused on Si- and Sn-based oxide materials that offer a considerably larger specific (4200 mAh g-1 and 994 mAh g-1) and volumetric capacity than conventional carbonaceous materials. Such studies indicate that silicone monoxide, SiO, has a large discharge specific capacity. However, due to their serious volume change when charging and discharging, leading to fast capacity fading and poor cycle performance, it is a great impact

to the material of its practical value. The composite of Si- and Sn-based compounds or alloys can effectively improve their cycling performance. In this work, we studied Si-SiOx-Sn/C composite which was prepared by thermal reduction method, and tested it as anode material for Li-ion battery. The composites were synthesized by heating the milled mixture of SiO, SnO2 and carbon in an inert gas filled furnace. The effects of temperature, electrochemical properties and impedance were researched, and the results were as follows:1. Si-SiOx-Sn/C composites were prepared in following steps:the mixture of SiO powder, carbon powder and Nano-SnO2 powder was milled in a planetary ball mill for 5 h. The milled composites were dispersed into the acetone solvent. The dried solid mixtures were heated to 750℃,800℃,850℃,900℃,950℃and 1000℃for 2 h respectively in a furnace tube under an inert atmosphere. The XRD results show that SnO2 can be reduced into Sn metal above 800℃, and silicon-mono-oxide is transformed into silicon and silicon dioxide (2SiO→Si+SiO2). Further results indicated that the composite heated at 900℃for 2 h is better in performance.2. Charge and discharge measurements were carried out employing a two-electrode 2025 coin cell. Lithium metal was used as the counter electrode. When the composite was heated