硅基锂离子电池电极材料的制备及其电化学性能测试

发布时间：2018-05-19 17:08

本文选题：锂离子电池 + 硅　；参考：《东华大学》2017年硕士论文

【摘要】：为了顺应社会生产发展的需要,能源器件中大热的锂离子电池一直面对着提高比容量,降低材料成本,简化生产工艺等各种亟待解决的问题。硅作为地球上含量第二丰富的元素,无论其单质或其氧化物都体现了与锂离子超高的结合能力以及较低的放电平台,因此硅基材料成为了当下最有潜力的锂离子电池负极材料。单质硅用作锂离子电池负极材料理论比容量高达4200m Ah/g,是目前流行最广的商用石墨电极(372m Ah/g)的十多倍,而且放电平台在0.2V附近,但是由于硅单质在充放电循环中与锂离子发生化学反应形成硅锂合金体积变化超过300%,导致电极材料整体容易发生破碎,脱离等现象,使得电池的容量迅速衰减,循环稳定性得不到保障。本文中为了减小因材料体积变化导致的电池性能衰减问题,利用盐酸多巴胺作为碳源物质对单质硅颗粒进行了包裹,并通过刻蚀在碳与硅颗粒之间形成了一层空腔,得到了Si@void@C结构纳米材料,既避免了电解液与硅颗粒的直接接触导致的硅的损耗,同时允许硅在内部空腔尽可能的与锂结合,保证了电池的比容量的同时也大大增强了电池的循环稳定性。该方法相对于前人的成果在工艺上减少了原料的引入,并减少了工艺步骤。硅最具有代表性的氧化物二氧化硅作为锂离子电池负极材料同样具有相当高的理论比容量(1965m Ah/g),放电平台在0.1V到0.7V之间,虽然二氧化硅的体积膨胀效应不像单质硅那么明显,但是该材料巨大的电阻严重影响了结合锂离子的能力,在电池内部锂离子会选择电阻最低的路径进行扩散,难免会出现因“绕路”出现的材料充放电不完全的现象。为了减小电极材料电阻,本文利用葡萄糖作为碳源对二氧化硅进行了包碳处理,得到了Si O2@C复合结构纳米材料,通过导电性更高的碳为二氧化硅颗粒之间构建一座桥梁使得锂离子能够充分与二氧化硅结合从而提高比容量。同时通过比较不同形貌尺寸的二氧化硅的电池性能分析了尺寸对二氧化硅电池性能的影响,以及不同碳含量对材料导电性的提升。
[Abstract]:In order to meet the needs of the development of social production, lithium-ion batteries with large heat in energy devices have been faced with various problems to be solved urgently, such as increasing specific capacity, reducing the cost of materials and simplifying the production process. Silicon is the second most abundant element on the earth. Both its single substance and its oxides reflect the ultra-high binding ability with lithium ion and the low discharge platform. Therefore silicon based materials have become the most potential anode materials for lithium ion batteries at present. The theoretical specific capacity of silicon as anode material for lithium ion batteries is up to 4200m / g, which is more than ten times that of the most popular commercial graphite electrode (372m Ah/ g), and the discharge platform is around 0.2 V. However, due to the chemical reaction between silicon and lithium ion in charge and discharge cycle, the volume change of silicon-lithium alloy exceeds 300, which leads to the breakup and detachment of the electrode material, which makes the capacity of the battery decline rapidly. Cycle stability is not guaranteed. In this paper, in order to reduce the problem of cell performance attenuation caused by the change of material volume, dopamine hydrochloride was used as carbon source to encapsulate the silicon particles, and a layer of cavity was formed between carbon and silicon particles by etching. The Si@void@C nanomaterials are obtained, which can avoid the loss of silicon caused by the direct contact between electrolyte and silicon particles, and allow silicon to combine with lithium as much as possible in the inner cavity. The specific capacity of the battery is guaranteed and the cycle stability of the battery is greatly enhanced. Compared with the previous achievements, this method reduces the introduction of raw materials and the process steps. Silicon, the most representative oxide silicon dioxide, also has a high theoretical specific capacity of 1965m Ah路 g / g as anode material for lithium-ion batteries. The discharge platform ranges from 0.1 V to 0.7 V, although the volume expansion effect of silicon dioxide is not as obvious as that of simple silicon. However, the large resistance of the material seriously affects the ability of binding lithium ion. In the battery, lithium ion will choose the lowest resistance path for diffusion, and the phenomenon of incomplete charge and discharge of materials due to "detour" will inevitably occur. In order to reduce the resistance of electrode materials, silicon dioxide was treated with glucose as carbon source. By constructing a bridge between silica particles with higher conductivity of carbon, lithium ions can be fully combined with silica to improve specific capacity. At the same time, the effect of the size on the performance of silicon dioxide battery and the improvement of the conductivity of the materials with different carbon content were analyzed by comparing the performance of silicon dioxide cells with different morphologies.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;TQ127.2

【相似文献】