【作者】 马华；

【导师】 陈军；

【作者基本信息】 南开大学 ， 无机化学， 2009， 博士

【摘要】 植入式医疗器件、电动汽车和通讯器材等移动式应用领域的快速发展,为锂一次和锂二次电池带来了前所未有的机遇与挑战。高容量、长寿命、高安全性的电极材料是锂电池领域研究的重点。目前锂电池中所用的传统电极材料存在着利用率低、锂离子扩散慢、极化大等问题,制约着锂电池性能的提升。纳米材料具有反应活性高、有利于电荷传导和物质输送以及独特的结构优势,可以有效地提高锂电池的性能,其组成、结构、形貌与性能之间的关系需深入研究。另一方面,以α-CuV₂O₆为代表的过渡金属钒酸盐和Si是极具潜力的锂电池电极材料。因此,本论文开展了过渡金属钒酸盐和Si纳米/微米材料的可控制备、表征与电化学性能研究。主要内容如下:采用水热法可控制备出α-CuV₂O₆一维纳米/微米材料,获得了α-CuV₂O₆纳米线“奥斯特瓦尔德熟化-分裂”的形成机理,详细研究了α-CuV₂O₆纳米线的嵌锂机理和电化学性能。结果表明:α-CuV₂O₆纳米线由于具有比表面积大、锂离子固态扩散路径短等优势,电化学性能得到显著提高,在20 mA/g电流密度下的放电比容量达到514 mAh/g,电荷传输反应表观活化能为39.3～35.7 kJ/mol,明显优于α-CuV₂O₆亚微米线、微米棒以及块状颗粒,在锂一次电池中表现出潜在的应用前景。通过水热-热处理两步反应可控制备出具有多孔结构的FeVO₄纳米棒和纳米颗粒,这种多孔材料显示出较高的放电容量和较好的循环性能,特别是FeVO₄多孔纳米棒循环20周后,放电容量仍能达到760 mAh/g,在锂二次电池负极材料中具有潜在的应用。进一步采用水热法可控制备得到了CoV₂O₆纳米线和Co₂V₂O₇微米片,并对其电化学性能进行了初步探讨。采用改进的溶剂热方法制备得到了Si纳米空心球,并开展了其电化学性能研究。实验发现:Si纳米空心球结构能有效缓冲充放电过程中体积膨胀所产生的应力,提高了循环性能,在2000 mA/g电流密度下循环48周后,Si纳米空心球放电容量仍然达到1095 mAh/g,为锂二次电池性能的提升提供了实验基础。更多还原

【Abstract】 The rapid development of mobile application areas such as implantable medical devices,electric vehicles and communications equipment,has brought unprecedented opportunities and challenges for primary and rechargeable lithium batteries. High-capacity,long-life and high-safety electrode materials are the focus of research in the fields of lithium batteries.Currently,the electrochemical performance of lithium batteries is limited due to the low utilization efficiency,slow diffusion of the lithium ion as well as severe polarization problem of the traditional electrode materials.The high reactivity,favourable charge transport properties and novel structural merits of nanomaterials make them suitable alternative to effectively improve the performance of lithium batteries.On the other hand,α-CuV₂O₆ and other transition-metal vanadates,and Si are potential electrode materials for lithium batteries.The relationship between their composition,structure,morphology and properties needs to be further studied.Therefore,this dissertation focuses on the preparation,characterization and electrochemical investigation of transition metal vanadates and Si nano/microstructures.The main content is as follows.The one-dimensional（1D）α-CuV₂O₆ nano/microstructures were successfully synthesized via a simple and facile low-temperature hydrothermal approach based on the "Ostward ripening-splitting" mechanism.The Li-ion intercalation mechanism and electrochemical properties of theα-CuV₂O₆ nanowires were investigated in detail. Electrochemical measurement results demonstrated that the as-preparedα-CuV₂O₆ nanowires displayed a discharge capacity of 514 mAh/g at 20 mA/g,and activation energies of 35.7-39.3 kJ/mol,which are superior to that of theα-CuV₂O₆ mesowires, microrods and bulk particles due to the large surface area and short Li-ion diffusion route of the nanowires.This result indicates that theα-CuV₂O₆ nanowires are promising cathode candidates for primary lithium batteriesPorous FeVO₄ nanorods and nanoparticles were prepared by a two-step process including a hydrothermal route and a calcination process.Electrochemical measurements revealed that the porous FeVO₄ nanomaterials exhibit further improved electrochemical performance.Particularly,the porous FeVO₄ nanorods retain a high discharge capacity of 760 mAh/g after 20 cycles,indicating their potential application in rechargeable Li batteries.Furthermore,the CoV₂O₆ nanowires and Co₂V₂O₇ microflakes were also obtained by hydrothermal method and preliminarily investigated as anode materials in rechargeable Li batteries.Silicon hollow nanospheres were successfully synthesized via a modified solvothermal approach.The growth mechanism and electrochemical properties of the Si hollow nanospheres were further investigated in detail.The results show that the Si hollow nanospheres retain a high capacity of 1095 mAh/g after cycling up to 48 cycles at 2000 mA/g.The superior electrochemical performance rises from the fact that the hollow nanospherical structure can reduce the stress caused by the volume change of the Si electrode during the charge/discharge process and restrain the aggregation of the nanomaterials.This work opens a new route for the performance improvement of rechargeable Li battery.更多还原