钛酸锂电极材料的制备及其电化学性能研究

发布时间：2018-06-19 23:58

本文选题：钛酸锂 + 二氧化钛　；参考：《吉林大学》2017年硕士论文

【摘要】：目前,中国经济的快速发展很大程度上依赖化石燃料的消耗。然而,化石燃料的过度使用导致了诸如全球变暖和空气污染等环境问题。化石燃料属于不可再生能源,寻找清洁和可再生能源,以解决化石燃料带来的环境问题和确保可持续发展迫在眉睫。以锂离子电池提供动力的电动汽车具有替代传统内燃机,减少温室气体排放的潜力。锂离子电池具有循环寿命长和能量转化效率高等优势,在消费类电子设备、工业储能设备和电动汽车领域扮演重要角色。在追求电池高能量密度、高功率密度和长循环寿命等性能的同时,提高其安全性不可忽视。作为锂离子电池负极材料,钛酸锂(Li_4Ti_5O_(12))在1.55 V的嵌锂电位可以避免SEI膜形成和锂枝晶生长。同时,Li_4Ti_5O_(12)性质稳定,适用广泛;还具有价格低廉、环保友好等特点。但是,Li_4Ti_5O_(12)的锂离子扩散系数和电导率较低,限制了其倍率性能。构造纳米尺度的Li_4Ti_5O_(12)缩短电子和锂离子扩散距离并使用非碳材料进行复合提高电导率和锂离子扩散速率是一种非常有效的提高材料倍率性能手段。本文以提高Li_4Ti_5O_(12)的倍率性能为出发点,以纳米化为手段对Li_4Ti_5O_(12)材料进行研究。(1)使用溶胶凝胶法,以乙酸为络合剂制备Li_4Ti_5O_(12)纳米颗粒。在保持高物相纯度、良好结晶性的同时,通过络合剂延缓反应时间,使反应在分子级别进行,将样品粒径控制在40~60 nm。在电化学性能方面,络合剂的使用降低颗粒尺寸,进而利于锂离子和电子传输,提升Li_4Ti_5O_(12)的倍率性能和循环稳定性。0.1 C倍率下比容量为168 m Ah g-1,1 C倍率下循环100圈后容量为120.5 m Ah g-1。(2)使用水热法制备尺度在200~300 nm,厚度为30 nm的纯相Li_4Ti_5O_(12)纳米片;解释纳米片的形核长大机制;探究不同煅烧温度对Li_4Ti_5O_(12)纳米片形貌和电化学性能的影响。在600°C煅烧6 h得到的Li_4Ti_5O_(12)纳米片不仅结晶度高,同时形貌均匀,拥有最高的比容量和最佳倍率性能。这种分散、独立的纳米薄片结构缩短了锂离子和电子扩散路径,利于其快速传输。(3)以尿素为添加剂使用改进水热法制备尺寸范围在100~300 nm,具有八面体结构的纯相Li_4Ti_5O_(12)颗粒。XRD测试和FESEM表征表明添加质量比为5%的尿素能够促进形成物相纯度高、结晶性良好和粒径均匀的Li_4Ti_5O_(12)八面体,同时还会抑制颗粒的团聚现象。(4)以简单和廉价的水热法合成超薄Li_4Ti_5O_(12)和TiO_2条带交替组成的双相纳米片,阐释双相材料形成机制。通过精确控制原料中锂和钛的比例,调控条带宽度;探究不同配比对材料晶体结构、形貌、比表面积和电化学性能的影响。TiO_2条带在双相Li_4Ti_5O_(12)-TiO_2纳米片中充当通道作用,让电子和锂离子快速嵌入脱出Li_4Ti_5O_(12)能力,提升了导电率和锂离子扩散速率。这一方法为制造新一代非碳高安全和高倍率性能的负极材料提供了可能。
[Abstract]:At present, China's rapid economic growth largely depends on fossil fuel consumption. However, excessive use of fossil fuels has led to environmental problems such as global warming and air pollution. Fossil fuels are non-renewable energy, so it is urgent to find clean and renewable energy to solve the environmental problems caused by fossil fuels and to ensure sustainable development. Electric vehicles powered by lithium-ion batteries have the potential to replace conventional internal combustion engines and reduce greenhouse gas emissions. Li-ion batteries have the advantages of long cycle life and high energy conversion efficiency, and play an important role in consumer electronics, industrial energy storage equipment and electric vehicles. While pursuing the performance of high energy density, high power density and long cycle life, it can not be ignored to improve its safety. As a cathode material for lithium-ion batteries, lithium titanate Li4TiTi5O-1) at 1.55 V lithium intercalation potential can avoid SEI film formation and lithium dendrite growth. At the same time, Li4Ti5OCoC has a stable nature and wide application. It also has the characteristics of low price, friendly environment and so on. However, the low lithium ion diffusion coefficient and conductivity of Li4Ti5O\'s\? It is a very effective means to improve the performance of materials by shortening the electron and lithium ion diffusion distances and using non-carbon materials to compound to improve the conductivity and the diffusion rate of lithium ions. In this paper, with the aim of improving the performance of the Li _ 4Ti _ 5O _ O _ (12) as a starting point, and by means of nanocrystalline, we have studied the Li4Ti5O _ (12) _ () material. While maintaining high phase purity and good crystallinity, the reaction time was delayed by the complex agent, and the reaction was carried out at the molecular level, and the particle size of the sample was controlled at 4060 nm. In terms of electrochemical properties, the use of complexing agents reduces particle size and facilitates lithium ion and electron transport. The specific capacity at 0.1 C ratio is 168m Ah g-1C ratio, and the capacity is 120.5 mAh g-1.2C) the pure phase Li4Ti5OOC12 nanocrystalline is prepared by hydrothermal method with the scale of 200nmt and thickness of 30nm. The specific capacity is 168mAh g-1C ratio and the specific capacity is 168mAh g-1C ratio. The mechanism of nucleation and growth was explained, and the effects of different calcination temperatures on the morphology and electrochemical properties of Likes _ 4Ti _ 5O _ s _ (12) nanoparticles were investigated. Li _ 4Ti _ 5O _ 2O _ (12) nanochips calcined at 600 掳C for 6 h not only have high crystallinity, but also have uniform morphology, the highest specific capacity and the best rate performance. This dispersed, independent nanoscale structure shortens the lithium ion and electron diffusion pathways, The results of XRD and FESEM analysis showed that urea with a mass ratio of 5% could promote the purity of the formed phase, and the size range was 100 ~ 300nm, and the pure phase Li _ 4Ti _ 5O _ 2O _ (12) with octahedron structure could be prepared by the modified hydrothermal method. LiS _ 4Ti _ 5O _ O _ (12) octahedron with good crystallinity and uniform particle size can also inhibit the agglomeration of the particles. (4) Ultra-thin Li4Ti5O / S _ 12) and TIO _ (2) alternate biphasic nanochips are synthesized by a simple and cheap hydrothermal method to explain the formation mechanism of the biphasic materials. By accurately controlling the ratio of lithium to titanium in the raw material, adjusting the strip width, and exploring the effects of different ratios on the crystal structure, morphology, specific surface area and electrochemical properties of the material. The ability to rapidly embed electrons and lithium ions out of Li4Ti5O\ This method makes it possible to fabricate a new generation of non-carbon high-safety and high-rate negative materials.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912;TB383.1

【相似文献】