【作者】 贺本林；

【导师】 力虎林；

【作者基本信息】 兰州大学 ， 物理化学， 2007， 博士

【摘要】 锂离子电池与传统的二次电池如铅酸电池、Ni／Cd电池、Ni／MH电池等相比，在比功率、能量密度及充放电性能方面有着明显的优势。而且，锂离子电池还有着循环寿命长、自放电率低、“绿色”环保等优点，目前已广泛地应用于小型用电器中，并正积极地向国防工业、空间技术、电动汽车、静置式备用电源（UPS）等领域发展。锂离子电池技术及性能的进一步提高，主要依赖于电池中各组分材料的改进开发及电池工艺的革新，进一步提高性能和降低成本是现阶段锂离子电池发展和改进的主攻方向。正负极材料由于在电池成本中所占比重较大，对它们进行研究显得尤其重要。本论文在综述当前锂离子电池电极材料最新研究进展的基础上，制备了相关的电极材料并对其在电池装置中的应用进行了深入的研究。利用TG-DTA、XRD、SEM和TEM等技术对电极材料的微观结构和形貌进行了分析，采用恒电流充放电、循环伏安（CV）和电化学阻抗谱（EIS）等技术详细的测试了其电化学性能。主要内容如下：1．对LiMn₂O₄正极材料的制备方法进行了详细的研究并加以改进，首次采用微波辅助流变相法制备了尖晶石型LiMn₂O₄锂离子电池正极材料。实验结果表明，微波辅助流变相法具有焙烧反应时间短，节约能源等优点，且制得的LiMn₂O₄样品形貌规则，颗粒分散均匀。这主要是由于微波加热不仅是从外部加热更是从前躯体的内部加热，是体加热，与传统的加热方式不同，热传递方式是由内到外，加热速度较快，因此提供了一个均匀的加热环境，这样既缩短了合成样品的时间又阻止了颗粒的团聚。从而使样品具有完美的晶体形貌和良好的电化学性能。2．对LiMn₂O₄正极材料进行了不同离子掺杂的改性研究。实验结果表明，金属阳离子的掺杂有效地抑制了LiMn₂O₄材料的Jahn-Teller畸变效应，增强了尖晶石结构中宿主内部原子间结合力，提高了材料结构的稳定性，进而显著提高了LiMn₂O₄尖晶石的循环稳定性。对比结果发现，铝、钴、锌三种金属离子的掺杂中，Co掺杂型LiCo_0.05Mn_1.95O₄正极材料具有最好的循环稳定性，循环30周后，其容量衰减仅为3％。且其具有良好的倍率容量，在2C／3下的放电容量是在C／3下放电容量的97.5％。这些优异的性能为LiCo_0.05Mn_1.95O₄样品的实用化提供了可能。利用阴阳离子的协同作用，制备了A1-F双掺杂型LiAl_0.05Mn_1.95O_3.95F_0.05锂离子电池正极材料。实验结果表明，前驱体中LiF的加入，可以起到助熔的作用，促进尖晶石相的烧结，对改善晶体的形貌起到了一定的作用。阴阳离子双掺杂的协同作用不仅降低了Jahn-Teller畸变效应，改善了材料的循环性能，同时也提高了材料的放电容量。因此，阴阳离子协同双掺杂对改善锰酸锂电池的电化学性能比阳离子单掺效果好。3．采用原位化学氧化聚合法制备了聚苯胺／多壁碳纳米管复合材料，首次将该复合材料用作可充式锂电池的正极材料，以提高聚苯胺的比容量及库仑效率。多壁碳纳米管对复合材料的电化学性能有着明显的改善作用，它使复合材料更可逆，具有更多的法拉第反应活性位置，增加了复合材料的电子导电率，降低了复合材料的电阻，便利了复合材料的电荷转移，且保持并改善电极结构，增强电极循环时的完整性。复合材料的最高放电容量达118.8mAh／g，而纯聚苯胺的比容量仅为97.8mAh／g，提高了约21.5％。而且多壁碳纳米管的引入有效地提高了聚苯胺的循环稳定性。4．通过银镜反应制备了TiO₂纳米管／Ag复合材料，并将其作为锂离子电池负极材料加以详细的电化学性能研究。由于金属银是优良的导体，它的引入可以加速电子的传递，有效地提高了锂离子在TiO₂纳米管中的迁移速率，从而降低了复合材料电池的内阻，减少了首次不可逆容量损失，改善了TiO₂纳米管的倍率特性，提高了TiO₂纳米管高的充放电倍率可逆容量及循环稳定性，并降低了电池的极化。更多还原

【Abstract】 Compared with traditional secondary batteries, e.g., Pb-PbO₂ battery, Ni-Cd battery, Ni-MH battery and so on, lithium ion battery shows greater advantages at the aspect of rate capability, energy density, and charge-discharge performance. Moreover, Lithium ion battery also shows the advantages of long cycling life, low self-discharge rate, and green environmental conservation. Recently, lithium ion battery has been widely used in minitype electric instruments, and are actively developing toward the fields of space technology, national defence industry, electromotive vehicle and UPS. The improvement of lithium ion battery technology and performance is depended on the development of the electrode materials and the renovation of the technics of battery, and nowdays the main attack is further improving properties and decreasing costs. It is very important to investigate the cathode and anode materials of lithium ion battery because they occupy a large proportion in the costs of lithium ion battery.In this thesis, we have reviewed the newest development in research of electrode materials of lithium ion battery, prepared relevant electrode materials and explored their applications in this device in detail. The micro-structures and morphologies of these materials were investigated by thermogravimetry/diffrential thermal analysis （TG/DTA）, X-ray diffraction （XRD）, scanning electronic microscope （SEM） and transmission electron microscopic （TEM）. The electrochemical performances have been evaluated by galvanostatic charge-discharge, cyclic voltammetry （CV） and electrochemical impedance spectra （EIS） detailedly. The main content is the following:1. The preparation methods of spinel LiMn₂O₄ cathode materials have been studied detailedly and made some improvement. Pure-phase and well-crystallized spinel LiMn₂O₄ powders as a cathode material for lithium ion battery were first successfully synthesized by a new simple microwave-assisted rheological phase method. The results of the experiments indicated that the microwave-assisted rheological phase method have the advantages of shorter sintering time and energysaving. The synthesized LiMn₂O₄ powders are pure, spinel-structure particles of regular shapes with distribution uniformly. Such well-crystallized particles benefit from the treatment of microwave because the microwave heated the precursor not only from the outside but from inside of the precursor and thus provided a uniform heating environment which shortened the synthesizing time and overcame the agglomeration of particles. It is apparent that this new microwave-assisted rheological phase method leads to the formation of better cubic spinel structure particles. Such kind of morphology will make the material have better electrochemical performance.2. The improvement of the performance of LiMn₂O₄ cathode materials by doping the spinel with other elements have been studied in detail. The results indicated that metal-doping could improve the cycle performance of LiMn₂O₄ due to inhibition of Jahn-Teller distortion and could enhance the atomic cohesive force in the cathode hosts to strengthen their stability. Among these Al, Co and Zn doped materials, the substituted cobalt manganese oxide spinel （LiCoo.05Mn1.95O4） had the best cycle performance, the capacity loss was only 3% of its initial capacity after 30 cycles. In addition, the LiCoo.05Mn1.95O4 spinel showed high rate discharge capability and good cycle stability, The discharge capacity ratio of （2C/3）/（C/3） is 97.5%. This outstanding performance provided the possibility for the practical application of LiCo_0.05Mn_1.95O₄ spinel material.Through cationic and anionic co-substitutions, Al-F double doped LiAl_0.05Mn_1.95O_3.95F_0.05 cathode materials were prepared. The results of experiment indicated that a little amount of LiF doping was allowed to play a role of reducing the melting point, which could accelerate the crystal formation of LiMn₂O₄, and improve the crystal structure and sample appearance. The cation and anion cooperation not only reduces the Jahn-Teller distortion, enhances the stability of LiMn₂O₄, but also improves the discharge capacity. Therefore, the cation and anion co-substitutions is a better way to improve the electrochemical performance of LiMn₂O₄ cathode materials than only substituted with cation.3. Polyaniline/multi-walled carbon nanotubes （PANI/MWNTs） composites were prepared by an in situ chemical oxidative polymerization method, and were firstly used as the cathode materials for rechargeable lithium battery to improve the specific capacity and coulombic efficiency of polyaniline. MWNTs have an obvious improvement effect, which makes the composites have more reversibility, more active sites for faradic reaction, and enhanced electric conductivity, lower the resistance, and facilitate the charge-transfer of the composites. Moreover, the addition of MWNTs can protect the well contact of polymers by retaining and strengthening the structure of the electrode automatically, and reinforcing the integrality of the electrode during cycling. The discharge capacity of PANI/MWNTs composites is high as 118.8 mAh g^-1, and it is only 97.8 mAh g^-1 for PANI. The cycle performance of PANI/MWNTs composites is also significantly improved by introducing MWNTs to pure PANI.4. TiO₂ nanotubes prepared by using a hydrothermal process were firstly coated with silver nanoparticles as the anode materials for lithium ion batteries by the traditional silver mirror reaction. The physical properties and electrochemical performance of Ag/TiO₂-NTs composites were investigated in detail. Because of the high electronic conductivity of metal Ag, Ag additive significantly increased the electronic conductivity of TiO₂ nanotubes, made the transfer rate of Li-ion in TiO₂ nanotubes higher, lower the resistance, reduced the first irreversible capacity, improved the reversible capacity and the cycling stability of the TiO₂ nanotube at high charge-discharge rate, and marvelously decreased the cell polarization.更多还原