【作者】 麦立强；

【导师】 陈文；

【作者基本信息】 武汉理工大学 ， 材料学， 2004， 博士

【摘要】 以钒氧化物纳米管（VONTs）、VO₂纳米棒和LiMVO₄纳米粉等为研究对象，采用现代测试手段对低维钒氧化物纳米材料合成、结构和性能进行了深入研究，探讨了组成、结构及性能的相关性，分析了结构形成和性能优化的机理和规律。主要内容和研究结果如下： （1） 钒氧化物纳米管：①流变相-自组装法合成了长1～10μm，内、外径分别为10～30nm和50～100nm，管束直径为200-300nm的钒氧化物多壁纳米管，为低成本、高可控合成低维无机纳米结构提供了一条新思路。基于“卷曲”或“弯曲”机制，分别建立了3-2-1D（R）及3-2-1D（B）钒氧化物纳米管生长模型。②VONTs首次充、放电容量分别为200、185mAh／g，明显高于其它正极材料归因于VONTs能为Li⁺提供更多的嵌入空间及更好的热力学嵌锂位置。放电容量循环10次后为120 mAh／g，纳米管中残余有机物导致容量衰减较快。③掺钼改变了纳米管生长动力学，形成大的层间距和更短的Li⁺扩散路径，改善了电化学性能。而惰性气氛下热处理使纳米管结构更稳定，具有更好的循环性能。激光辐射除去了残余有机物而改善了电化学性能。PEO嵌入纳米管内或管壁钒氧化物层问，占据一定嵌锂位置，导致容量有所减小，但PEO修饰导致局部最优取向纳米管束形成以及屏蔽VO_x层对Li⁺的库仑作用，促进Li⁺的定向迁移及嵌脱可逆性。VONTs活性物质与乙炔黑比例对电化学容量的测量有较大影响，比例为4：3和4：1时的放电容量分别为185、383mAh／g。用Mn²⁺交换纳米管中有机模板，稳定纳米管结构，减少了循环过程中的容量损失。④VONTs在450～550nm出现弥散结构的光致发光带，[VO₄]四面体较短的V=O键容易在外界能量激发下使O的外层电子迁移到V⁵⁺的外层轨道形成V⁴⁺-O^-离子对，导致发光。掺钼纳米管发光谱增强，峰位蓝移至455nm。因Mo与纳米管间的耦合及量子限域效应，吸收边红移。⑤VONTs富含缺陷，很易形成表面态，使表面电子的非和谐振动加强，产生加强的Raman散射，导致纳米管光学非线性的增强，提高了由双光子吸收机制引起的光限幅性能及由二声子或多声子组合辐射机制引起的红外辐射性能。掺钼引起晶格畸变，降低晶格振动对称性，进一步提高了红外辐射性能。 （2） VO₂纳米棒：①以V₂O₅和CTAB为原料通过流变相-自组装法首次合成了长1～2μm，直径30～60nm、棒束直径lOO～300nm的VO₂（B）纳米棒。VO₂（B）纳米棒的形成为“面着陆”自组织过程。VO₂（B）纳米棒经H₂O₂和CTAB溶液处理，发生了VO₂（B）→VO₂（R）→VO₂（M）相迁移过程，得到VO₂（M）纳米棒。②VO₂（B）纳米棒首次充、放电压平台分别在2.75和2.5V附近，充、放电容量分别为254.08、247.60mAh／g。前35次循环的效率均超过97.4％。③掺钼抑制了VO₂（B）纳米棒深放电时相分离，增大充放电容量，对结构起支撑和“钉扎”作用，抑制了晶体单胞结构的改变，改善了循环性能。④VO₂（M）纳米棒在65℃时出现相变，电阻突变4个数量级，温度滞豫宽度为8℃，低温半导体相的激活能为0.2eV，费米能级位于禁带中央附近。掺钼VO₂（M）纳米棒形成施主能级，武汉理工大学博士学位论文禁带宽度变窄，使半导态向金属态转变温度降低为59℃。⑤分析“一维纳米束”的结构状态，为准确描述纳米结构、丰富纳米科学内涵提供参考。 （3） LIMvO;纳米粉:①柠檬酸凝胶燃烧法在450℃制得了纳米颗粒（一次粒子直径为30一90lun）团聚后直径为100一3 00刊rn的纳米LINio.SCoo.svO4。②纳米LINi05Coo万VO;首次充、放电最高电压均达4.8V，充、放电容量分别为90和72mAh/g。电解液氧化造成10次循环后放电容量降至38.7mA柑g。5102表面修饰减少了LINi05Coo.SVO;与电解液的接触，抑制了二者之间的恶性作用和副反应的发生，明显改善了LINi05Coo.SVo;的电化学性能，首次充电容量为1 00 mAh/g，前10次循环容量保持率为87%。纳米LINio.SCoo乃VO4的室温电导率为7.03 x 10一，szem。掺少量饰时，L训io.seo05vo;的电导率增至5.14x 10一s/em。更多还原

【Abstract】 In the dissertation the low-dimensioned vanadium oxide nanomaterials such as vanadium oxide nanotubes(VONTs), vanadium dioxide nanorods and LJMVO4 nanomaterials were chosen as the objects of study. Modem testing methods were used to study the preparation, structure and properties of low-dimensioned vanadium oxide nanomaterials. The obtained main results are as follows:(1) Vanadium oxide nanotubes: (1) Vanadium oxide nanotubes with length of 1-10 m, inner diameter of 10~30 nm, outer diameter of 50~100nm and the diameter of the namotube bundles of 200~300nm were synthesized in a Theological self-assembled methods, which open a way which synthesizes low-dimensioned inorganic nanostructure in a low-cost and high-control way. Based on the mechanism of "rolling" and "bending", the growth model of 3-2-1 D(R) and 3-2-lD(B) are built. (2) The first charge and discharge capacity for VONTs is 200 and 185mAh/g, respectively, evidently higher than other cathode materials, which is attributed to more intercalation space and better thermodynamic intercalation sites for Li+ in the nanotubes. The dicharge capacity decrease to 120mAh/g after 10 cycles because of the presence of residual organic template. (3) Mo doping changes the growth dynamics of the nanotubes, and results in bigger interlayer spacing and shorter diffusivity distance and enhanced electrochemical performances. The heat treatment in inert atmosphere makes the nanotubes have stabler structure and better cycling properties. Laser is used to remove the residual organic template to improve the electrochemical performance. PEO is inserted in the tubes, which takes up some space and leads to the decrease of the capacity, but the PEO insertion can form the partial preferential direction of the nanotube bundles and shield the electrostatic interaction between V2O5 interlayer and Li+ ions to improve the transition and the insertion/extraction reversibility of Li+. The molar ratio of VONTs to carbon materials have great effect on the electrochemical capacity. When the ratio is 4:3 and 4:1, the attained discharge capacity is 185 and 383mAh/g, respectively. The topological substitution of the residual amine with Mn2+ stabilize the structure the nanotubes, and decrease the loss of capacity in the process of cycle. (4) The well-resolved photoluminescence band at 450-550 nm is discovered in VONTs, which is attributed to the transitions from the lowest vibrational level of excited triplet Ti(V4+-O-) to the various vibrational levels of the ground state So(V5+=O2-) and belongs to the mechanism of charge transition. The intensity of photoluminescence spectrum of nanotubes increases with Mo doping and shifts to 455nm. The coupling effect and quantum limiting effect between Mo and nanotube lead to red shift of absorption edge. (5) There are abundant defects on the nanotube surface and the surface states are easily formed, VONTs exhibit stronger optical limiting property based on TPA and better infrared radiation property based on two phonon combination radiation mechanism. And this infrared radiation property isimproved with Mo doping resulting in decreased symmetry of crystal lattice vibration.(2) VO2 nanorods: The VO2 (B) nanords with length of l~2um, nanorod diameter of 30~60nm, and the diameter of the nanorod bundles of 100~300nm were synthesized for the first time by V2O5 and CTAB in a Theological self-assembled methods. The formation of VO2 (B) nanorods is "face landing" self-assembled process. The as-synthesized VO2 (B) nanorods was treated by H2O2 and CTAB solution and VO2 (M) nanorods were attained through phase transfer process of VO2(B)-VO2 (R)-VO2(M). (2) The initial charge and discharge capacity of VO2(B) nanorods is 254.08 and 247.60mAh/g, respectively. The efficiencies of first 35 cycles exceed to 97.4%. (3) Mo doping reduces the phase separation during deep discharge and supports structure, resulting in improved electrochemical performance. (4) For VO2(M) nanorods, the transition temperature is 65 C and the hysteresis loop width is 8C. The active energy of更多还原